Mechanism and Machine Science

This paper deals with the operation modes analysis of a 4-CRU parallel mechanism for 3D printing building as a new technology for constructing the sustainable houses. The analysis is based upon an algebraic approach, namely the Euler parameters quaternion and primary decomposition. The 4-CRU parallel mechanism is composed of rectangular base and platform that are connected by four identical CRU legs. Each leg consists of cylindrical (C), revolute (R) and universal (U) joints. Dimensions of rectangular base and platform are the design parameters and can be varied. Initially, the parallel mechanism is described by a set of four constraint equations that define the motion of CRU legs. Then the primary decomposition is computed over a set of constraint equations and it turns out that the 4-CRU parallel mechanism has three distinct operation modes, namely the Schönflies mode, the reversed Schönflies mode and additional modes. The Degree-Of-Freedom (DOF) of the additional mode can be either 4-DOF or even degenerate into 3-DOF, depending on the ratio of the platform to the base. This additional mode is also a transition mode for the mechanism to switch from the Schönflies mode to the reversed Schönflies mode, and vice versa. This condition makes the 4-CRU parallel mechanism become reconfigurable manipulator as long as the additional modes exist. A mock-up of 4-CRU parallel mechanism has been fabricated to depict the Schönflies mode, the reversed Schönflies mode and the additional modes performed by the moving platform.

This paper presents the work carried out to improve the design of an existing kinesthetic haptic device. The proposed improvement is designated for enhancing this device’s impedance width which is a common metric in performance evaluation of haptic devices. In this study, kinematic design optimization, static balancing, constructional design enhancement, and actuation system design studies are presented.

Within a predefined limit, continuously variable transmission (CVT) systems can continuously vary the power transmission ratio. The transmission in CVTs is achieved via friction, belt or gear systems. If CVT designs can incorporate backdrivability, independent output position and impedance variation, shock absorbtion, and low mass and inertia, they can be employed in human–robot interfaces. Among various types of CVT designs, the two-cone drive CVT designs have a major drawback since the output torque and position cannot be changed independent of each other. The friction wheel used in this design does not have a holonomic motion capability and causes this inconvenience. In order to overcome this problem, a sphere is used in this work for the CVT design as the transmission element. In addition, it is stated in the literature that common CVT drive systems do not have the capability to be used in cyclic bidirectional motion. In the presented CVT design, a second sphere is added to the system with two springs from the lower part of the cones for pretension in order to solve the bidirectional transmission problem. In this paper, the working principle and conceptual design details of the novel two-cone CVT drive are presented. Experimental results showed that the novel CVT has the capacity to transmit bidirectional power with some accuracy.

Current evacuation processes of natural disaster pose difficulties, since there are limitations from rescue team as well as workspace provided by existing tools. Cable driven parallel robot (CDPR) is a robot designed to overcome these limitations. It provides a large workspace with high mobility. Accordingly, this research aims to determine the geometric, static, and kinematic models of suspended CDPR consisting of 8 cables for search-and-rescue operation. The dimensions of mobile platform (length, width, and height) and cable arrangements are computed to achieve the largest interference-free workspace. The arrangements are varied based on the combination of anchor points and exit points. The optimum designs are obtained and presented based on three case studies by varying the external forces. The case where the CDPR is subjected to minimal external wrenches performs maximum workspace about 64.8% of the desired workspace.

Rehabilitation of ankle injuries must be under supervision of a therapist to prevent severe injuries. However, relying on a therapist is not consistent and accurate. In the present days, parallel manipulators play a key role as an ankle rehabilitation device to overcome the problem imposed by a therapist. The ankle rehabilitation device should be able to sustain the external forces and moments exerted from the patient’s feet. The external forces and moments applied to the platform can cause deflections, either translation or rotational deflections. These deflections depend mostly upon the stiffness properties of the device. The stiffness property is one of crucial factors to be considered in designing the ankle rehabilitation device. Therefore, this paper aims to analyse and establish the static and stiffness model of the 3-RPS parallel manipulator which is employed as an ankle rehabilitation device. Each RPS leg applies one constraint force and one actuation force intersecting the centre of spherical joint. By collecting all constraint forces and actuation forces, the Jacobian matrix can be formulated according to the Screw theory and Quaternion parameters. Influences of actuators and base-and-platform configuration are identified by using stiffness index, namely eigenvalues of the stiffness matrix. The base-and-platform configuration is described by the distance of each joint to the origin of coordinate frame and the angle among three legs. For given external wrenches, numerical simulations have been performed to determine the optimal distributions of actuators and base-and-platform configuration by taking into account the stiffness.

This paper presents a novel geometric solution to the problem of finding singularity-free paths joining two arbitrary points in the constant orientation workspace of a semi-regular Stewart platform manipulator. The formulation builds upon the known closed-form expression for the gain-type singularity surface of the manipulator. Using a rational parametrisation of the surface, it computes the geodesic curve on this surface, connecting the projections of the two given points on this surface. A sequence of spheres is then constructed in such a manner that each sphere is tangential to a previous one as well as the singularity surface, at a point on the said geodesic curve. Thus the geodesic curve acts as a guide, over which the singularity-free sphere is rolled, till it reaches its destination. Multiple methods for computing such sequences of spheres are presented and compared with the help of a numerical example. Finally, a sequence of line segments connecting the centres of the spheres is constructed, which connects the two given points via a provably singularity-free path.

This paper reviews the various methods developed for balancing of the planar mechanisms and synthesizing the link shapes. The methods discussed in this paper are used for complete force balance, complete force and moment balance, partial force and moment balance as well as for the link shape synthesis of different planar mechanisms. The concepts, applications, and limitations of various methods are discussed and reviewed from the available literature in the area of mechanism balancing. The better understanding of available methods will definitely help the researchers working in this area in analyzing the current practices and in developing the new methods.

This paper gives a screw theoretic insight into the instantaneous kinematics of the Darboux frame (D-frame) moving on a smooth surface. It is established that the velocity state of D-frame is described by a three screw system. The principal screws of this system depend only upon the local shape of the surface. The twist of the D-frame is decomposed into twisting about surface normal line and a screw which is a ruling of a cylindroid. The properties of this cylindroid are studied. It is also shown that the twist of the D-frame can be obtained by a linear combination of pure rotations about three axes. This result is used to arrive at an equivalent 3R (revolute) serial chain whose end-effector is the D-frame. An illustrative numerical example is presented.

Drivers of the road and off-road vehicles are continuously exposed to low-frequency whole-body vibration of significant magnitudes arising from tire/track-terrain interactions. The human body models reported in the literature for analyzing these are usually of lumped parameter category having only a few degrees of freedom. Most of them are also one-dimensional models, i.e., they allow an analysis of vibration only in the vertical direction. The highly complex motion that the human body is subjected to in real life requires at least a two-dimensional model. This paper presents a multibody human body model of 12 degrees of freedom that represents a seated human with backrest support. The motion has been assumed to occur in only the sagittal plane allowing vibration analysis in two dimensions. The modeling of the interconnection of masses using rotational and translational springs and dampers and the contact with backrest gives a better simulation of forces transmitted to the upper and lower torso. A sensitivity study to find the effect of critical model parameters on the frequencies of peak moduli helps in identifying the section of the human body which should be given appropriate support for improving comfort. This can lead to the re-design of the seat by considering the effect on different sections of the human body. This is expected to be a better approach than the current practice of considering the overall effect on the human body.

Theory of Machines and Mechanisms is the foundation for the world’s race toward automation. Simple mechanisms, cams, and gears find applications in all such automated systems. Therefore, a thorough understanding of these basics is quite essential. The authors are a part of the development team of MechAnalyzer, a software aimed at easing the teaching and learning of concepts related to mechanisms. In this paper, several new modules are reported. Cam module lets user select properties of a cam-follower mechanism and the steps required to draw cam profile is animated and shown to the user. Similarly, concepts related to gear profiles and meshing of gears are illustrated in gears module. Another module is presented which lets user understand the velocity analysis of planar mechanisms using the Instantaneous Center (IC) method. All these modules and the earlier set of modules to teach kinematics of mechanisms are readily available for free at http://www.roboanalyzer.com/mechanalyzer.html .

Older adults and people with various neurological diseases need some external assistance even during normal walking. Amongst various factors, due to a decrease in the muscle strength, they are not able to produce a large force that significantly affects the pre-swing phase of their gait cycle, an important determinant of walking speed. While there is significant work done on active assistance for walking, almost no work has been reported on the effect of torsional spring and combinations of torsional and linear springs as a mode of passive assistance. OpenSim was used to model the effects of linear and torsional spring-based passive assistance on the total metabolic energy and ankle moment during human gait. A total of six conditions were simulated out of which five gave satisfactory findings. Particularly, a combination of ankle torsional and gastrocnemius path springs showed the largest reduction in the peak total metabolic energy and peak plantar flexor moment during the pre-swing phase of the gait cycle, suggesting that such passive assistance could be used as an effective mode of support for walking.

This paper focuses on harvesting energy from chaotic vibration by attaching piezoelectric patches at the end of a cantilever beam. For more efficiently harvesting energy, the cantilever beam should be bistable and the majority of the trajectories should be of large amplitude orbit. The optimization problem of parameters is discussed.

This paper deals with the calibration of a Hybrid Robot which is a combination of serial and parallel mechanisms having five degrees of freedom. In this paper, a new methodology has been introduced to determine the kinematics of such robots to ease the complexities. A reference frame has been defined on the moving platform which helps to bifurcate the hybrid mechanism for analysis. Calibration of the PKM is complex compared to serial robots because of the passive joints present in the PKM. The calibration of the parallel mechanism part of the hybrid robot has been presented here. Sensitivity analysis of the kinematic parameters of the PKM has been performed to identify the most significant parameters to influence change in the joint variable. Generalized calibration algorithm has been developed using the least square approximation method which requires less number of poses (only 8 poses). The calibration procedure presents an approach which does not involve any external measurement or calibrating devices. The experimental results are validated through a simulation model and hence can be effectively used to calibrate the hybrid robot.

Piezoelectric energy harvester is developed and optimized based on Intelligent Optimization Techniques (Bat algorithm (BA), Grey Wolf Optimization (GWO), and Hybrid Grey Wolf Optimizer tuned Bat Algorithm (HGWOBA)) for medical applications. The structure is modeled by utilizing analytical equations to identify the voltage and power generated by the piezoelectric device and to use them for medical applications. These analytical equations of voltage and power are utilized as the objective function of the intelligent techniques to enhance the harvested voltage and power by optimizing the piezoelectric parameters. In this work, pacemaker and hearing aids are chosen as the medical applications, for which, the piezoelectric device is modeled and designed with respect to intelligent optimization techniques. Therefore, the design variables of the piezoelectric harvester are optimized and designed for medical applications. Moreover, the harvesting efficiency, stress, frequency, and load impedance of the piezoelectric device is calculated. Finally, with the results obtained, a comparative study is analyzed between the optimization techniques. Among them, HGWOBA is more efficient in comparison to BA and GWO, which has improved the efficiency of the unimorph piezoelectric harvester from 48.78 to 68.96%, which is designed for medical applications.

In the present work, a modular end effector has been conceptually designed to facilitate excavation using the gripper of the robotic arm of a proposed future rover. The advantage of the modular end effector is that it uses a common robotic arm for carrying out surface and subsurface collection using the respective active and passive modules thereby reducing the mass associated with independent multiple arms used for carrying out specific excavation. The design of the different modules of the collection mechanism is based on the mass of the sample and the interaction of excavation modules with the terrain. To provide contamination-free samples, each sample is required to be encapsulated in the very unit where it is collected and then placed inside the storage container for earth return. A rapid prototype of the mechanism has been developed and functionally demonstrated over lunar soil simulant. This paper contains the details of design, analysis, fabrication and tests carried out on a modular end effector to verify its functional performance as a sample collection mechanism. The present work provides a theoretical and experimental groundwork to design sample return mechanisms for future extraterrestrial missions. The calculations are done using MATLAB, the modelling using Siemens NX and the designed components are rapidly prototyped.

This paper presents an approach to design and optimize the planar walking mechanism that enables fast locomotion along with minimal actuation. The design of walking mechanism is based on the symmetrical foot-point path to get the required stability for walking on an even terrain and simplify its motion control. A systematic methodology is used for the concept generation of walking mechanisms to achieve these objectives. A brief study of a wide range of walking mechanisms developed in the past is used to develop Computer-aided Design (CAD) model of a single Degree of freedom (DOF) planar walking mechanism. An analytical method for dimensional synthesis based on path generation is used to get dimensions of linkages. Additionally, geometric constraints of motion are used to anticipate free variables to solve for unknown terms in the equation. However, the inclusion of the control system required for simulation in the CAD software is not feasible. Construction stages are shown to aid the development of the simulation model. This is accomplished by interfacing Solidworks and MATLAB/Simulink environments. This paper, in short, is an effort to develop simulation-based methods for optimizing planar mechanisms.

The current computation models for gear contact analysis and wear prediction are mostly based on finite element analysis which consumes a lot of time and effort. In this paper, an alternate model to spur gear contact analysis is developed using linear complementarity. A linear complementarity solver computes the contact forces between meshing teeth along the path of contact. From the contact forces, sliding wear in gear tooth is predicted. Archard’s wear model is used for the wear prediction. The results of linear complementarity and finite element model are compared for both contact forces and sliding wear. For identical meshing gear pair, the linear complementarity model consumes much less computation time than the finite element model.

Nowadays, mechanism design is no longer a process based on pen and paper. Due to the increased complexity of mechanisms, a more effective proceeding is required. Since the appearance of increasingly powerful computers, the number of software tools for mechanism design had likewise increased. This huge number of software solutions can be divided into two categories—geometric software products and dedicated mechanism design software. Since most of these software solutions have disadvantages concerning the function range or usability, a new software product is under development by the Institute of Mechanism Theory, Machine Dynamics and Robotics (IGMR) of RWTH Aachen University. The consideration of new software engineering methods and software design processes allow a continuous implementation of functionalities that are not yet state of the art. One of these functionalities is the combination of analytical and numerical approaches within the kinematical analysis of planar mechanisms. Besides presenting the combination of analytical and numerical approaches, this paper will further outline the motivation to develop a new software solution. In addition, the software architecture as well as the software engineering process will be described.

In this paper, a design problem is attached to develop a robotic platform with hybrid mobility capability by combining locomotion and flight operations. Such a complex mobile robot can be required in applications in which one motion capability is not enough to ensure the success of an assigned task, such as in damaged cultural heritage sites, risky industrial environments, or accidented power plants where several kinds of obstacles cannot be overcome by locomotion and flying is not always possible. Design requirements are analyzed in order to identify the peculiarities of combining locomotion and flight in a suitable robotic platform with modular mechanism design that is based on parallel architecture for leg structures and propeller plate for drone flight. Design issues are discussed in terms of size, features, component assembly, user-oriented operation, sensors, and equipment for assigned tasks. A specific example is reported as referring to the design experience of HB platform that has been developed at LARM for applications in Cultural heritage sites both for inspection and intervention. A prototype is illustrated to show the feasibility of the proposed integrated mechanism design with suitable operation capabilities.

A mobile robot needs to perform localization and navigation tasks. In indoor environments, global localization sensors such as GPS cannot be used. Thus the robot has to build an environmental map using other available sensors (e.g., laser scanner, stereo camera, and bumpers) and localize itself on this map. The goals of this work are (i) to design and implement sensory fusion (available sensors are laser scanner, stereo camera, bumpers, and odometry) during creation of an environmental map; (ii) to perform obstacle detection during navigation; and (iii) to perform goal-driven navigation with obstacle avoidance. The work has been carried out on a Seekur Jr. robot by Adept MobileRobots, which in the state of the art uses most often the laser scanner alone. The proposed approach is a novelty technique to obtain a 3D enviromental map by merging the precision of the laser scanner with the capability of obtaining dense spatial information of the cameras.

Interest in low-voltage hybrid systems has grown because of the potential for significant fuel economy gains at a relatively low cost. Start/stop technology in hybrid powertrains is an economical technical approach in this general area of powertrain refinement. A new engine start mechanism concept is presented herein. It can change its operating state between two modes, respectively, involving a geared or belted connection to the crankshaft. This novel starter device enables an ultrafast start as well as a 5–10% fuel economy improvement, depending on voltage and power levels implemented. We also present a detailed engine cranking model developed in AMESim that distinguishes between motoring and firing events to get an accurate representation of engine dynamic torque response during engine start/stop events.

Theo Jansen built wind-powered walking mechanisms or strandbeasts using a basic 12-linked leg mechanism which has a single degree of freedom (DoF). In this work, the Jansen leg mechanism is used as a start point in an optimization routine to arrive at a single DoF mechanism to trace the ankle trajectory. Optimization and forward dynamic analysis methodology of the mechanism are presented. This preliminary work can be used in the design of rehabilitation devices and assistive exoskeletons.

There are several devices and machinery which are products of ingenious thought and subsequent refinement. Textile machinery specifically those used in the small scale sector in developing nations are one example of such an evolution. Here we examine the possibilities of enhancement of the performance of the DOBBY—a device used in weaving machines which are attached to a loom for weaving small patterns. The DOBBY (and the Jacquard) is the forerunner of modern digital systems and uses reciprocating “knives” for actuating the “healds” through a set of hooks. The hooks are brought into engagement and disengagement with the reciprocating knives depending upon the position of “feelers” that sense holes on punched cards. This ingenious device has served the handloom and power loom sector well. There is a limit, however, on operating speeds and thus throughput because of the dynamics of the “make and break” contact between the knives and hooks. The knife and hook engage with a jerk that causes unwanted dynamic forces and vibration which in turn is reflected in the weave. An attempt has been made to eliminate the “knife and hook” design through use of a circuit composed of “mechanical logic gates” to eliminate the “make and break” and maintain a continuous set of derivatives of motion in the critical portions of the activity of the device. The number of moving links in the mechanism has increased as a consequence of this artifice. The DOBBY can be recognized to be a “D Flip-Flop” in computer parlance by casting and examining its Truth Table. The elements in the circuit that was arrived at are AND and OR mechanical gates which had been synthesized over the past few years. The use of mechanisms with lower pairs ensured that the devices exhibit smooth motion. A working model was made and demonstrated.

The ride comfort, driving flexibility and stability, and operation safety all directly or indirectly depend on the suspension mechanism. Therefore a suspension system defines, in a certain degree, the vehicle’s performance. Traditional longitudinal spring suspension system occupies a large space which is not beneficial either to enlarging the steering angle or to the layout of vehicle chassis. This paper therefore proposes a suspension mechanism within which there are four identical single leaf-springs assembled in parallel. Thus the suspension forms a statically indeterminate oblique structure which improves the stiffness, strength, and reliability while reducing its total mass. The oblique arrangement of the leaf-springs allows the suspension to occupy smaller space which therefore provides larger steering angle for a vehicle. Experiments with real vehicles proved that this kind of suspension should also improve the dynamic performance as it reduces the suspension mass due to the redundant leaf-springs. Therefore, the oblique leaf-spring suspension mechanism can enhance the ride comfort, handling flexibility and stability, and driving safety of a vehicle.

The kinematic structure of an epicyclic gear train (EGT) contains the information regarding which link is connected to which other link and by what type of joint. In accordance with the graph theoretic framework for EGTs, its kinematic structure can be represented using a simple graph model. During the conceptual stage, structural synthesis of EGTs is performed, and it is aimed at the enumeration of all non-isomorphic graphs (concepts), for a given number of links and DOF. All the candidate graphs are generated by performing some combinatorial operations on a set of parent graphs. Basically, the structural synthesis approaches in the mechanisms literature can be grouped into three categories, namely, recursive, non-recursive and acyclic graph-based schemes, respectively. In this work, the strategies for generation of EGTs, adopted by different researchers and spanning all the three categories, are reviewed. Moreover, the different graph representations encountered in synthesis of EGTs and the generation algorithms are lucidly explained using examples. A recent trend is the development of synthesis methods of EGTs inspired from established methods of those of linkage-type kinematic chains.

This work presents grasp planning on everyday objects using vision. The hand considered is a one degree-of-freedom parallel jaw gripper of Mitsubishi Movemaster robot. Candidate grasping points are chosen on the object and a grasp matrix is computed for the grasp. The grasp matrix can be used to computationally determine a force-closure grasp feasibility. For selecting the candidate grasping points, image of the object is used. Three quality metrics based on different physical notions of quality of grasp are computed. The first quality measure tells how far a grasp is from violating the friction limits, the second gives the worst case performance of the force-closure for all external wrenches, and the third tells how well the object is enclosed from all directions. The main contribution of the paper is to compare grasps based on different quality measures and understand their physical interpretation.

An elephant trunk robot is a continuum robot consisting of a flexible backbone actuated by two pairs of cables (or tendons) offset by a distance and along the circumference of the backbone. By pulling the cables, the continuum robot assumes the shape of an arc of a circle in 3D space. In the literature, forward kinematics of the robot has been developed using differential geometry of 3D curves. In this paper, we show that forward kinematics can also be obtained by discretizing along the length of the robot, with each discrete element modeled as a four-bar mechanism, and using a minimization approach. Each of the four-bar mechanism is assumed to be rigid with constant link length. It is shown that minimizing the angle made by the coupler link with the fixed link of the parallel linkage results in a profile which is numerically same as that derived from differential geometry for a segment of the cable-driven robot in 2D. The results obtained for actuation in 2D are extended to 3D, using two four-bar mechanisms actuated by the two sets of cables, and it is shown to match the analytical formulation available in the literature. The proposed method of using a sequence of four-bar mechanisms opens up a new perspective in modeling the forward kinematics of cable-driven continuum robots.

In the field of robotics, several instances exist when a robot has to be controlled or jogged to move to a required configuration. It can be done using input devices such as a teach pendant, which requires the user to be well experienced in handling it. Another intuitive way to control a physical robot is by using an exoskeleton, a device that can be worn on a human arm which records the motion of the human which can be fed into the robot controller. In this paper, an efficient methodology to determine the usability of the exoskeleton to control a serial manipulator is presented. First, the CAD model of the exoskeleton is used to extract its Denavit–Hartenberg (DH) parameters using an analytical method developed by one of the authors. The obtained DH parameters and the CAD files of the exoskeleton are then imported in the Virtual Robot Module of RoboAnalyzer software, which acts as a server application. The virtual exoskeleton can be moved by giving the motion of the joints and hence acts as an intermediate step to validate whether the joint angles obtained from the sensors of the exoskeleton are correct or not, which otherwise requires trial and error strategy. Once the joint angles are found to be correct and free of noise, they can be used to control virtual and physical robot manipulators. In this paper, ABB IRB140 has been controlled both virtually and physically through an exoskeleton developed at ABB Ability Innovation Center.

Passive compliance is a necessary feature to ensure safety of home robots and medical robots working in human daily life. Such kinds of robots are desired to adjust their stiffness characteristics according to the task at hand and the surrounding environment. In this paper, we present an approach to control both the position and passive stiffness of output links of elastically constrained underactuated link mechanisms. Specifically, we consider a planar parallel link mechanism with nine degrees-of-freedom (DoF) consisting of six active revolute pairs with rotary actuators, eighteen passive revolute pairs, and nineteen links. Six of the passive revolute pairs are elastically constrained by torsional coil springs, thus the mechanism has passive compliance. We propose an optimization procedure to control the output position and multi-directional non-linear stiffness characteristics simultaneously by determining input actuator angles. The validity of the proposed analysis and optimization procedure is also experimentally corroborated.

The bat is an efficient flyer with flapping membrane wings but the measurement of aerodynamic forces is the major challenge. The motion of the bat’s wing is very complex which comprises translation as well as rotation. During the bat’s flight, the wing membrane will deform in the downstroke and upstroke process of wings. The investigation of the detailed kinematics of short-nosed fruit bat (Cynopterus sphinx) was conducted. We performed high-speed recordings of the kinematics to obtain 3D reconstructions of membrane wing movements. Living bats were used for performing the experiments. We used the motion capture system, OptiTrack, to measure the data set on the flapping membrane wings of the bat and finally rebuild the bat’s flight in the form of soft wings through this experiment. However, due to the complex kinematics of the bat’s wing, there are some periods when many points on the wing cannot be tracked by the motion capture system as the wing flaps. To rebuild the wing profile, a detailed analysis of every point is required. Therefore, this paper proposes numerical algorithms and MATLAB programs to recover the missing data from the wing during the flight of a bat. It is the purpose to find efficient calculation and analysis procedures and to provide ideas and techniques for the analysis of all marked points on the membrane wings of the bat.

Interplanetary missions have increased in the recent years, with spacecrafts landing successfully on Moon and Mars. The entry, descent, and landing on another planet is still a challenging job, since earlier few missions were unsuccessful. The lander is a mechanical system which is a combination of links and joints which provides the soft-landing platform for the spacecraft. The lander needs to be designed such that it can absorb the maximum impact energy and provide stable landing. Dynamic analysis of a lander is required in order to understand the behavior of impact forces on the lander. The main objective of this paper is to analyze an existing legged lander system configuration which will be capable of withstanding and attenuating the impact force. ADAMS simulation of a single-legged system is carried out for a range of terminal velocities. The simulation results are compared with the results of a single-legged system drop test.

In this project, we focus on developing wheat harvester for small farms of India. Farming has become efficient today since farmers have started adopting modern technologies such as tractors, threshers, etc. Still, farmers having small farms in India cannot afford such machines. Also, these machines are not designed to work on small farms. So, in small farms, manual labor is used for basic farming operations such as harvesting. It costs farmers concerning both, the money and the time. Also, people working as labor in such farms develop health issues such as back pain as they need to sit in an awkward position on the ground while harvesting. In our research, we have noticed that around 20 people are required to harvest the wheat in around 0.25-acre land in 1 day. So, this wheat harvester has the potential to reduce the labor force required tremendously.

Force regulation is a big challenge when robot end-effector interacts with the unknown environment. To satisfy such requirement, kinds of constant-force mechanisms (CFMs) are designed. Compared with the active CFMs, the passive CFMs get rid of introducing complex sensors and advanced control algorithms. Chained beam-constraint model (CBCM) can be used to model the large deflection problems efficiently. Based on CBCM, this paper explores the buckling properties of flexure beam and then presents one kind of CFM. Such CFM obtains the constant-force output by utilizing the flexible fixed-guided beam, which undergoes its first buckling mode. Finite element analysis (FEA) and experiment are also given to prove the designed CFM.

In this paper, we propose a Reinforcement Learning (RL) based approach to stabilizing and control of a biped robot. Bipeds have complex requirements of stabilization and gait planning in multiple degrees of freedom. A reinforcement learning strategy is presented in this work for the stabilization of a single leg as well as a biped to create a learned behavior of a system. In this paper, each leg of the Humanoid biped robot is approximated as a double inverted pendulum, and its static stabilization is studied in the sagittal plane. The equations of motion are derived using Lagrange’s formulation method. An equivalent Humanoid robot single leg and biped model developed in Gazebo. Through Robotic Operating System (ROS), a reinforcement learning based control algorithm was developed for static stabilization, and the simulation was carried out on the Gazebo model. A total of 1458 states are used for training the reinforcement learning algorithm.

Exoskeletons can augment the capacity of humans and restore mobility. Design of exoskeletons has been primarily experimental. The effect of different actuation and control strategies are learned from experiments. Human device interaction can be considered in the design phase using biomechanical simulations and it can provide optimal designs. In this study, we use musculoskeletal modeling and simulation to find optimal actuator configuration of exosuits for reducing the metabolic cost of walking with heavy loads. Computed muscle control algorithm was used to compute the muscle excitations and actuator controls required to achieve experimental kinematics. A muscle energy expenditure model was used to estimate the reduction in metabolic cost with each actuator configuration. Results show that biarticular actuator configurations can provide higher metabolic cost reduction compared to uniarticular configurations.

A solar tracker is a machine that uses a mechanical prime mover to tilt solar photo voltaic panels from east to west during the day to track the sun for maximizing the production of PV power by keeping the incident angle of sun-rays perpendicular to the panel surface. Drag and lift produced by the wind on the surface area of solar panels causes a torsional moment on the tracker structure, and may induce torsional instability in the structure due to wind galloping. The use of hydraulic dampers is recommended to reduce the intensity of galloping and reduce the potential risk of damage to the tracker structure and panels. In this paper, the vibration characteristics of the tracker structure are analysed (theoretically and numerically) with and without external dampers, using the lumped spring-mass-damper approach to identify the suitability of the selected dampers for the application.

In this paper, surface texturing has been adopted for meso scale gas journal bearing. Square texture shape is considered for the study. The compressible Reynolds equation of textured gas bearing is solved by the finite element method. For this, COMSOL 5.3 simulation software is used. The influence of partial texture on bearing hydrodynamic characteristics at variable process parameters such as eccentricity ratio, clearance, and journal speed has been studied. The hydrodynamic characteristics such as load capacity and friction coefficient are considered. In comparison with plain bearing, the significant improvement in hydrodynamic characteristics of textured bearing is observed. The texture arrangement in 0°–180° zone influences more to the load capacity and friction coefficient.

Underwater glider has an outstanding advantage of long endurance for ocean observation. This paper presents underwater glider path planning with uncertainties under the framework of partially observable Markov decision processes (POMDPs). The kinematics model and the sensor model of the underwater glider have been built, and the uncertainty of action has been taken into consideration. The priori probability distribution and posteriori probability distribution are obtained from the kinematic model and sensor model, respectively. Particle filtering has been used to combine the two probability distributions. Results show that integrating the uncertainties in state estimation can improve the accuracy of waypoint estimation. Obstacle avoidance is also presented in the same framework.

Compliant mechanisms provide friction-less and backlash-free smooth motion as it is obtained through deformation of flexible members. Micro-compliant mechanisms are widely used in many applications such as MEMS, micro-gripper, and tweezers for biological applications, precise motion of focusing lens. In the literature, various fabrication techniques such as wire EDM, micro-milling, Very-Large-Scale Integration (VLSI)-based lithography, and etching processes are used to fabricate micro-compliant mechanisms. These processes suffer from limitation that high speed, high resolution, and high aspect ratio (required for high performance mechanisms) all cannot be there in a single process. 3D micro-printing has the potential to meet these stringent requirements in a cost-effective manner. We demonstrate in this paper, development of high aspect ratio micro-mechanisms via 3D micro-printing based on indigenous technology. This 3D micro-printer has been developed based on micro-stereolithography technology with patented scanning. We report comparable short printing time, resolution, and ultra-high aspect ratios obtained using the proposed method.

Lower limb orthoses are wearable robotic devices used to assist people suffering from diseases such as paralysis, paraplegia, foot drop, muscle weakness, etc. People suffering from such diseases either lose their ability to walk or they walk in an asymmetric gait cycle with reduced speed and get exhausted easily by walking a short distance. The commercially available orthosis is very costly and moreover they do not provide complete rehabilitation. In the study, people suffering from lower limb muscle weakness are considered and a simulation study on orthosis design to assist them during swing phase of ground-level walking is described. The structural as well as functional aspect of a biological leg is considered to perform the simulation. Three-link (representing thigh, shank and foot) model is considered to perform the simulation of human lower limb in swing phase. Based on biomechanics, different muscles of lower limb are mimicked by using springs and series elastic actuator. A trajectory optimization problem is formulated to get human leg model’s hip, knee and ankle joint trajectories in the range of normal human during swing phase by varying stiffness of different springs and biarticular actuator parameters. The simulation results showed that the model’s different joint trajectories are well within the bounds of normal human by using only one biarticular series elastic actuator at the place of gastrocnemius muscle and passive elements such as springs. Thus, we can assist human during the swing phase of ground-level walking by using such a small actuator set.

The motion of a small rigid particle over a conveying tray that has oscillatory motion in an inclined direction with respect to horizontal is simulated and analyzed. Initially, when the amplitude of oscillation is small enough, the particle always remains in contact with the tray; however, it travels longitudinally due to differential friction in forward and backward directions which is produced due to vertical motion of the tray. As the oscillation amplitude is increased, the body loses contact and has periodic sliding and projectile phases of motion. The effect of friction coefficient, acceleration amplitude and vibration angle on the mean conveying velocity is examined. When the amplitude is further increased, the body starts bouncing on the tray after the impact and the motion appears to be chaotic. However, it is found that when a particle is dropped from a certain height, the periodic bouncing motion can be obtained with specific parameters.

Two variants of the drivetrain of a post-transmission parallel hybrid electric mini truck namely SCHD and TCHD, operated in the speed coupling (SC) and torque coupling (TC) hybrid modes respectively are analyzed. The equivalent fuel consumption of the conventional and hybrid drivetrains was estimated for three urban drive cycles. Substantial improvement was achieved in the equivalent fuel consumption in comparison with the conventional vehicle for both the variants. TC provided better reduction (up to 55.9%) in the equivalent fuel consumption than SC (up to 34.2%). A metric $$\Delta $$ SFC is introduced to determine the mean deviation of the engine operating point relative to its optimum over a drive cycle. $$\Delta $$ SFC was evaluated over three drive cycles for the conventional and hybrid drivetrains and was least in case of TCHD, indicating that in TC, the IC engine is operated more efficiently than SC.

A passive monolithic compliant grasping mechanism that works based on the eversion of an elastically deformable bistable shell is conceptualized. It comprises grasping arms made of beam segments that work in conjunction with the everting shell. The grasper is capable of picking up a stiff object of any shape up to a maximum size and weight. The bistable shell everts upon contact with the object to enable the grasping arms envelop the object forming an enclosure. The mechanism then stays in that configuration until it is actuated again to turn the shell back to its original configuration and thereby opening the enclosure to release the object. The stiffness of the arms decides the payload of the mechanism. The size of the arms decides the largest object that can be grasped and held. The arms have distributed compliance so that they can conform to the shape of the object without applying undue force on it.

This paper deals in design synthesis of a three translational degree-of-freedom Delta manipulator by combining together two different approaches (average condition number and power of point). By doing so, shortcomings of both approaches are eliminated. To solve this, multi-objective problem is solved with GA-based multi-objective optimization which works on the principle of Pareto optimality. Different constraints used in optimization are also discussed. A numerical example is presented to observe the effect of different constraints and objective function on the design variables which in turn dictate the manipulator workspace. Further, we try to conclude with a general procedure to design a Delta manipulator without using optimization routines.

The aim of this study is to investigate the existence of a symmetric and periodic walking gait in a flexible passive dynamic biped for walking along an inclined plane. This model is a simple, two-link, 2-D passive compass gait biped. These two links are connected at the hip through a freely rotating revolute joint and one of the links (stance leg) can change its length when it is in contact with the ground. Hence, the robot has three degrees of freedom (DoF). Dynamic equations of the system during the swing phase have been determined using the Euler–Lagrange method. For the linearized model, we have analytically obtained a natural set of initial conditions to obtain a periodic gait with above constraints. These initial conditions were used to obtain the periodic cycle for the non-linear model and the corresponding time period through numerical optimization. It has been investigated the effect of leg stiffness on the gait parameters. We found a flexible biped which can produce symmetric walking gait and walks fast.

Parallel Kinematic Mechanism’s (PKM) are being used for machining complex and intricate shapes for précised applications with higher stiffness and rigidity. It is possible to achieve different geometries with variable poses of the tool. PKMs are also being used for various operations such as inspection, surgical, assembly, etc. This paper focuses on modelling and analysis of a novel three legged PSS PKM for precise applications. The available automated systems are expensive and bulky making it less suitable for small/medium-scale industries. The focus of this paper is to develop a simple and cost-effective 3-PSS PKM. Kinematic modelling is done using the geometrical approach. The workspace for this PKM is plotted using MATLAB and compared with the existing mechanisms. The optimum workspace is determined using Genetic Algorithm (GA). Further, the static structural analysis is done using ANSYS for the determination of maximum stresses and deformation induced in the robot on the application of static load. The dynamic analysis is carried out using the MSC ADAMS software. The dynamic torques, acceleration and forces acting at each joint are determined instantaneously by considering velocity variations across sliders and friction at all joints.

Climbing robot requires adhesion mechanism for holding the robot on to the surface and locomotion mechanism for moving the robot along the wall surface in order to perform various tasks such as glass façade cleaning and remote surface inspection of civil structures. Pneumatic adhesion force control has a prominent role for safe locomotion of the climbing robot. In case of insufficient adhesion force or airflow leakage, the robot may not work properly while carrying payload such as cleaning device, multiple sensors, and power systems, etc. Actuation and de-actuation (open and close modes) of adhesion force control of multi-suction cups based on the traditional design restricts its application particularly in climbing on wall structures where the weight and electrical power have a major concern. In the present study, pneumatic adhesion mechanism based on flat suction cup has been chosen for its performance characteristics analysis, while operation under rough and smooth wall surface conditions. Based on these experimental investigations and stability analysis, pneumatic adhesion and timing belt mechanisms for simultaneous operations of adhesion and locomotion have been developed. The developed concept for multi-suction cup-based timing belt mechanism is implemented in a mobile robot for climbing on a vertical/inclined wall surface. The manufacturing trials for simultaneous locomotion and adhesion required for surface climbing have also been conducted under static and dynamic situations.

Multi-patch isogeometric analysis (IGA) of planar compliant mechanism, based on the planar Timoshenko beam theory, is presented. IGA is a new computational framework that seamlessly integrates geometric modelling and deformation analysis. The multi-patch technique enables analysis of multi-segmented beam structures with bifurcation points and star junctions. Methods to handle various Dirichlet and Neumann boundary conditions in the framework of IGA are also discussed. Displacement and section force distributions obtained from IGA are compared with the results obtained from finite element analysis (FEA) and analytical solutions. IGA is particularly advantageous in the problems involving geometries with large curvatures, such as curved beams, curved thin plates, etc. Such curved geometries can be used to model various interconnected members in a compliant mechanism. The multi-patch IGA approach discussed in this paper can be used to improve the efficiency of shape optimization process of planar compliant mechanisms, by providing better control over the shape using fewer design variables and by reducing errors arising due to geometric approximation.

In this paper, a contact-aided compliant flapping wing for micro air vehicle (MAV) is presented. The design consists of a perforated plate, covered with flaps which allow motion in one direction only. In order to arrest the motion of flaps in the other direction, a contact stopper is provided. When the wing (i.e., perforated plate along with flaps) is making a flapping motion in a fluid environment, it experiences different drag forces in forward and reverse strokes. The wing is made with acrylic (Poly (methyl methacrylate) or PMMA) sheet having 2 mm thick. The flaps are connected to perforated plate by compliant joints that act as torsional springs. Furthermore, these compliant joints aid in moving flaps from open to a closed position. Experiments were carried out in both air and water medium for various plate configurations. It is observed that only 14.71% of input power is saved during a reverse stroke of four-flap perforated plate while flapping in air. Hence, the advantage is less in air, wing thickness needs to be reduced substantially to get an advantage in air medium. But in a water medium, input power is saved by 32.80% for the current dimensions. This increment is due to the fact that the density of water is more compared to air. It is also noticed that there is no advantage beyond 65 and 70% of area reduction in air and water mediums respectively as it is the minimum power required to drive the servomotor.

Traditional tensegrity mechanisms comprise compressive (rigid rods) and tensile members (cables). Compliant tensegrity mechanisms (CoTM) include springs alongside cables. Introduction of spring elements allows these structures to be more adaptable and robust. The kinematic and stability analyses of such mechanisms will facilitate better understanding of their behaviors for developing control and design methodologies. The analysis of CoTM often involves making the zero free-length (ZFL) assumption, i.e., the free-length of the spring is zero, which disqualifies the analysis for most real-word applications. The paper illustrates the drastic increase in computational complexity for finding static solutions as the assumption of ZFL for spring elements are relaxed for a simple planar compliant tensegrity mechanism comprising two rigid triangular platforms connected by a compressive member and two spring elements. The resulting nonlinear behavior of obtained static solutions shows intersecting manifolds of equilibrium orientation angles where the number of solutions vary from minimum of 4 to beyond 10 as the spring free-lengths are varied.

Serial manipulators have limited purpose in the area where quick motion is a prerequisite. Parallel manipulators are known to be advantageous due to their low actuation inertia. However, the dynamics of parallel manipulators are highly coupled and nonlinear, and control structures require de-coupling modules, if quick motion is required with direct drive systems. Underactuated (base actuated) serial manipulators use the benefit of the two and serve the purpose of quick motion. The proposed method is different from the available “flatness”-based methods of underactuated control. Additionally, the requirement of passive actuation in the joints is evaded. In this paper, we propose a control algorithm for swing up control of Double Inverted Pendulum on a Moving Cart (DIPMC) and Single Inverted Pendulum on a Moving Cart (SIPMC). The control algorithm is divided into two parts: Feedforward controller and Feedback controller. In feedforward controller, a force predictor input is applied from the base to ensure the manipulator achieves a pose in the required domain and then a subsequent feedback-based control is implied on the system.

The work proposes an underactuated design of a glove-like soft hand exoskeleton for grasping and lifting objects of varied shapes and sizes. Strings are used to flex all finger joints, assuming that finger anatomy of an impaired hand is intact. A pulley-based differential mechanism is designed to actuate all four fingers via a single motor to allow adaptive grasping. Two DC motors are used, one for flexion of all four fingers and the second for thumb flexion. Finger extension is passively achieved via elastic bands on the dorsal side. A prototype of the hand exoskeleton, weighing 300 g without battery is fabricated that occupies $$100\times 56$$ mm $$^2$$ space over the palmer side of the forearm. Novelty in the design lies in reducing the required length of the existing pulley-based differential mechanism from 20 cm to 10 cm. Lightweight, and compactness make the device portable. Performance of the soft exoskeleton is demonstrated via testing it on a healthy subject.

Distance-bound smoothing is a method to characterize point configurations satisfying a given set of constraints on the pairwise ranges of distances between the points. This technique essentially consists in the iterative application of a set of algebraic conditions to reduce the given initial distance ranges. Although originally developed in a Computational Chemistry context, it has successfully been applied to problems of planar point configurations arising in Robotics, which includes the position analysis of planar robots. In this paper, this technique is generalized to deal with points on a sphere so that the planar case can now be deduced from the one presented here as a limit case. To exemplify the interest of this technique, it is applied to solve the position analysis of multiloop spherical linkages.

This paper proposes a lying/sitting type lower-limb rehabilitation robot based on a three degrees of freedom spatial parallel kinematic manipulator namely “The Orthoglide” along with an actuated rotational degree of freedom at the end-effector for the purpose of lower-limb rehabilitation treatments. This rehabilitation robot is an end-effector/foot-plate based mechanism which controls the ankle-joint movements to assist physiotherapists in performing therapeutic treatments along with a passive orthosis (supporting system). The conceptual and detail design of the rehabilitation device is presented along with its kinematics. Further, the functional validation of the proposed robot in terms of the kinematic motion capabilities to provide physiological motions like knee flexion-extension, hip adduction-abduction and hip flexion-extension are also investigated. The required safety features for the proposed rehabilitation robot in terms of mechanical constraints and non-actuated joints are also discussed.

Hand rehabilitation requires intensive training of various gross and fine movements. Robotic devices have been developed and tested for implementing intense training of different hand functions in the current literature. Current hand rehabilitation robots can be broadly grouped into two categories: (a) simple robots with one or two degrees-of-freedom (DOF) that train only one or two hand functions; or (b) complex robots with several DOF capable of training a wide range of functions. Thus, to train different hand functions, we either need a set of simple robots or one complex robot, both of which are not economically viable solutions. A potential solution is to have a single DOF robot that can train a wide range of functions, i.e. a robot with a single actuator, along with a set of easily pluggable passive mechanisms for different hand functions. In this paper, we present the design and analysis of various kinematic mechanisms for a single DOF hand rehabilitation robot plug and train hand rehabilitation robot (PLUTO). Three different kinematic mechanisms have been designed and analyzed to train four different functions: wrist flexion/extension, wrist ulnar and radial deviation, forearm pronation/supination, and gross hand opening-closing. Proper alignment of the robot and human joints is essential for safe and appreciate interaction with a human. Misalignment in the robot and human joints can cause undesired forces on the human joint, makes the interaction potentially unsafe. The problem of misalignment was addressed in the proposed mechanisms through the use of appropriate passive DOFs between the robot and human joints. This paper presents the design and analysis of the three mechanisms for the different hand functions. The analysis of the mechanisms were carried out by considering variations in human hand anthropometry, and uncertainty in the robot-human axis alignments.

Compared to the last few decades, there is an increase in prevalence of neuromuscular diseases like stroke, multiple sclerosis, and cerebral palsy. These diseases cause lower limb disability like drop foot. The main reason for drop foot is weakness in dorsiflexor muscles. Drop foot results in ‘toe drag during swing phase’ and ‘foot slap during heel contact’. Ankle foot orthosis (AFO) is a mechanical device, which is used to treat drop foot. Based on usage of sensors, actuators, and control systems, there are three types of AFOs: Semi active, Active, and Passive AFOs. Semi active and Active AFOs contain sensors, actuators, control systems, and onboard power source. Passive AFOs do not contain electrical boards but contain mechanical elements to control relative motion between foot part and shank part of the AFOs. Based on relative motion between foot and shank parts of AFOs, AFOs are also classified into two types: Non-articulated (or Fixed) and Articulated AFOs. Non-articulated AFOs are single piece devices having no relative motion between foot part and shank part of the device. Articulated AFOs are two-piece devices, having relative motion between foot part and shank part of the device, and the relative motion is controlled by passive and active actuators. In this paper, different working principles, advantages, and disadvantages of the existing AFOs are presented.

This paper illustrates the validation of a mathematical model developed for the kinematic and dynamic analyses of the lower body exoskeleton mechanism using Adams software. This framework is designed to assist individuals in the shipbuilding industry for lifting heavy payload with reduced physical fatigue. It contains modeling, simulation, and validation of the proposed lower body exoskeleton mechanism. An Adams software-based simulation environment is developed to validate the results obtained from the kinematic and dynamic analyses of the mechanism. Further, this work also extends to actuator and valve selection, sizing by utilizing clinical gait data (CGA). Torque versus gait cycle curves obtained for all active exoskeleton joints shows that the design has adequate torque to perform tasks with a payload of 30 kg. The design also ensures a minimum consumption of energy at the same time. Future work will be to build a prototype and test simulation results.

Omnidirectional mobile robots are widely used in various fields like warehouses, hospitals, military and nuclear power plants. Due to independent actuation of each wheel, it facilitates the highest order maneuverability and mobility. However, it being a complex mechatronics system, dynamic modeling and control is a challenging task. In this paper, an attempt is made to model a four-wheel omnidirectional mobile robot using highly intuitive bond graph technique. The dynamic model thus obtained is used to derive the control law for the robot. Control of the robot along desired trajectory is attained using principle of differential flatness theory. The validation of the approach is done in real time by performing simulation and experimental trials. These trials revealed effectiveness of bond graph technique for dynamic modeling of robot and flatness-based controller for smooth and accurate trajectory tracking.

This paper presents elaborated optimization process for lobed petals of a novel affordable setup capable of climbing staircases. Completely innovative method of specifically built wheels is already presented by the authors in their previous research paper. This setup uses driving wheels similar to lobe cam. The outline of each cam is conjugate to the staircase. Number of petals was an independent parameter. So it was important to select suitable number of petals for the projected setup. Standard process of ‘Design of Experiments’ is adopted for deciding the appropriate number of petals. Last section presents results of the study.

The double-wishbone (DWB) is a popular suspension system, particularly in the high-end automobiles. Simulation of its kinematics and dynamics are vital elements in the process of analysis and design of these complex mechanical systems. However, the simulation of the DWB suspension can be computationally demanding, due to the large number of nonlinear, coupled ordinary differential equations (ODEs) that arise from the motion of the multiple links present in the system. In this paper, a less common approach to the Lagrangian formulation is adopted, which is known as the embedded formulation or the actuator space formulation. In this formulation, the number of ODEs to be solved come down to only two-a number that equals the degree-of-freedom of the system. The joint variables associated with the unactuated links are computed through the forward kinematics of the system. This method has the advantage of reducing the computational burden in the numerical solution of the ODEs significantly, as the number of ODEs comes down to two, as opposed to eleven in the more commonly used configuration space formulation. Furthermore, the unactuated variables are determined from the kinematic constraints, as opposed to being computed from the numerical solutions to ODEs, which make them more accurate. The formulation is illustrated via numerical examples implemented in the Computer Algebra System (CAS), Mathematica. It is believed that such a formulation would aid in the understanding of the dynamics of the suspension systems, and help in the process of their design.

Mechanical logic gates, whose embodiments were demonstrated in the past with rigid bodies connected with kinematic joints, are revisited in this work using compliant mechanisms. In particular, an OR gate is designed using pinned-pinned bistable arches. The compliant OR gate consists of five bistable arches arranged in such a way that a central arch acts as the output with 0 and 1 stable states while two pairs of arches, with their own 0 and 1 states, act as inputs. The arch-profiles of all arches are designed so that the forces of switching and switching back between the two stable states and the travel between the two stable configurations are as per the desired functionality. An analytical method, which is based on linear superposition of buckling mode shapes of a straight pinned-pinned column, was used to design the arch-profiles. Finite element analysis was used to validate the OR logic behaviour of the entire setup. A macroscale prototype was made using 3D printing to demonstrate the working of the OR logic. Since mechanical gates are useful at the micro-scale, using fixed-fixed arches instead of pinned-pinned arches is beneficial from the viewpoint of microfabrication.