Recent Advances in Mechanism Design for Robotics

The problem of grasping with robots is solved by using suitable finger mechanisms that are inspired from structures in nature. A variety of solutions have been experienced and are used in a variety of designs all around the world. This paper discusses a survey of possibilities by addressing attention to characteristics and problems in the design and operation of those finger mechanisms. The author’s experience with LARM hand is reported to show practical results in attaching the problem of improving efficient solutions with better finger mechanisms.

Wristed, multi-fingered hands can be designed for specific tasks, leading to an optimized performance and simplicity. In this work we present the design of the simplest family of multi-fingered hands, with one revolute joint at the wrist and a set of fingers attached to the palm with a single revolute joint each. It is shown that hands with two to five fingers can be designed for meaningful tasks, and that two arbitrary positions can be defined at most for these hands, yielding a good tool for pick-and-place, or grasp-and-release, tasks. For each of those possible designs, dimensional synthesis is performed and an algebraic solution is derived. It is proved that two solutions exist for the general case of this family of hands. Coupled actuation for the grasp-and-release task can be easily implemented for these hands, to create an underactuated design able to be driven with a single actuator. Some examples are presented.

Underactuated and adaptive robotic hands are known for their ability to achieve multiple contact points on arbitrarily shaped objects with relatively simple actuation, improving grasp stability. However, in some cases the sequence in which these contact points are initiated does not promote robust capture of the grasped object. This paper presents the design of a new type of underactuated grasper based on an asymmetric pantograph structure. The new grasper achieves robust enveloping capture of arbitrarily shaped objects (including non-convex shapes) while maintaining balanced forces at multiple contact points. The design is easily adjustable for differently sized objects.

In this paper it is shown how a general 2-DoF dyad can be designed mass equivalent to a general (1-DoF) link element. This is useful in the synthesis of balanced mechanisms, for instance to increase or reduce the number of DoFs of a balanced mechanism maintaining its balance. Also it can be used as a simple approach for synthesis of complex balanced mechanisms. For finding the parameters for mass equivalence, a mass equivalent model with real and virtual equivalent masses is used. First the characteristics of this model are explained, then the properties of a mass equivalent dyad are shown. Subsequently with two methods the parameters of a mass equivalent dyad are derived and application examples are illustrated and discussed.

The conventional industrial manipulator has some drawbacks such as low payload-weight ratio, bulky structure and high power consumption, which limit their applications in such areas a space, anti-terrorism, service and medical robots. To overcome these shortcomings, a novel lightweight arm was developed based on modular joints, modular connection and light shaft structures. This paper discusses the general requirements for lightweight robots, upon which the new robot was designed. Both mechanics and electronics designs are presented. The development work of a prototype is described. Preliminary tests were conducted to evaluate the performance of the light weight arm. The results demonstrate the good performances of the prototype and validate the feasibility of the new robot system.

Force and moment balancing (dynamic balancing) of rigid body linkages with constant mass links is a traditional but still very active area of research in machine dynamics and robotics. The shaking force and the shaking moment caused by all moving links can be reduced in different ways but all having a common difficulty named to derive the so-called balancing conditions, that in general can be cumbersome. In this article a novel method to find the dynamic balancing conditions based on the use of Natural Coordinates is introduced. The method is direct, efficient, and easy to automate through the application of a computer algebra system. It can be used to obtain the shaking force and the shaking moment balancing conditions for planar and spatial mechanisms.

In this paper, a new 5-DOF arc welding robot is presented from aspects of mechanical design, control system and handheld welding teaching (HWT) method. Structure of this robot is inspired by selective compliance assembly robot arm (SCARA). With the aim to achieve HWT, magnet-clutches and encoders are adopted into the transmission chains which have large reduction ratio. In addition, a gravity balance mechanism is developed to reduce the load of operators. The processing of HWT operation is presented with optimal space arc interpolation algorithm. Two main design characteristics of this robot are low cost and easy operation features as compared to conventional 6-DOF industrial robots. Finally, experiments are discussed as from testing the welding performance and reported results validate the efficiency of the proposed solution.

In view of the Biglide parallel machine, this paper presented the theoretical and experimental basis for grinding the designated geometrical parameters of twist drill based on optimizing of the grinding parameters. The kinematics structure of the Biglide parallel machine was firstly introduced for grinding of the twist drill, and then the mathematical model of the twist drill flank was derived. And the relations between the geometric parameters of the drill point and grinding parameters of the grinding machine were analyzed, through which the optimal grinding parameters were obtained by using genetic algorithm. It was verified that the optimized grinding parameters improved the grinding precision,depending on the customers’ demands.

This paper focuses on the kinematics of a 3-RRR planar hybrid mechanism, which consists of serial and parallel kinematic chains. The configuration design is analyzed. The forward position and the inverse kinematic problems are formulated. The kinematic problem is solved by applying Chaos Particle Swarm Optimization. Moreover, three kinds of singularities are analyzed. The results play an important role in practical application for the 3-RRR hybrid mechanism.

A crucial parameter for the operational capability of a serial robot is its accuracy. For recurring tasks the high repeatability of the manipulator is utilized by programming the robot online. Therefore, the end effector is moved manually to all desired or necessary poses of a given task and the joint angles of the manipulator are stored at these poses. The end effector can return to these stored poses very accurately due to the high repeatability of industrial robots. But even this repeatability is subject to limits. A major influencing factor is the finite resolution of the encoders integrated within the manipulators joints. Based on the discrete encoder readings, the end effector pose can only be estimated. Despite the typically high resolution of encoders in modern industrial robots, it is worth considering this issue in detail, as one can identify interesting structural properties that are invariant with respect to the encoder resolution. In this work, we will show how to compute the upper limit of the estimation error depending on a desired pose and posture of the manipulator. Both positioning and orientation error due to this discretization effects are considered. Simulation results are illustrated by means of a general 6R serial manipulator and a path, which the end effector can follow with 16 different postures.

In this paper we present the design and development of the social robot called iSocioBot, which is designed to achieve long-term interaction between humans and robots in a social context. iSocioBot is 149 cm tall and the mechanical body is built on top of the TurtleBot platform and designed to make people feel comfortable in its presence. All electrical components are standard off-the-shelf commercial products making a replication possible. Furthermore, the software is based on Robot Operating Software (ROS) and is made freely available. We present our experience with the design and discuss possible improvements.

This paper proposes improvements to a simple spatial rehabilitation mechanism for the human ankle, aiming to prevent exertion of forces on the joint, and control the range of flexion it experiences. Such functions would additionally provide information on recovery status in terms of degree of mobility regained, and the force and torque on the affected joint. This information would both provide support for physiotherapists in their work and help to establish self-rehabilitation on the part of the patients themselves. The mechanism presented is built upon previous research of an extended Oldham’s coupling mechanism combined with a driving four-bar linkage. A complete rehabilitation device is designed and produced to be lightweight, affixed only to the patient’s leg with no additional supporting structure, and able to drive motion along a variety of total flexion angles by changing link lengths using a removable 10 mm pin and pre-drilled holes.

This paper deals with the kinematics, dynamics and joint torque distribution of a novel hexapod robot. In order to climb over large obstacles or high steps, a neck joint has been installed between the front and central part of the body. The formulation of dynamics is performed by the Lagrange’s equations, using the robot screw theory and product of exponential method. The torque distribution model is settled based on the inverse dynamics and force distribution of the tip point. The analysis has been verified by simulation and experiments to further improve the design and control of the hexapod robot.

In this paper, an automated twistlock handling robot system is proposed with the aim to perform tedious and danger works with safe efficient operations. The proposed robot system is composed of an unmanned ground vehicle, a human friendly lightweight robot manipulator, a robot gripper with three fingers, and a 3D Kinect sensor for object recognition. A segmentation algorithm has been developed and 3D models have been elaborated for different twistlocks. Then, a library has been built for automatic object recognition and registration purposes. An architecture design of the software module is introduced and a full cycle of twistlock handling operation is illustrated. Simulations are reported in order to evaluate feasibility and operation performances of the system.

A new grinding method for the helical drill point based on a biglide parallel grinder was introduced in this paper. According to the mechanism description and kinematics analysis about the biglide parallel grinder, the mathematical models for the flank surface near the chisel edge was established in Cartesian coordinate frame and parametric form respectively. Moreover, the simulation of the flank surface was conducted. It was also discussed the effects of the velocity of the two glider and the distance between two gliders on determining the flank surface distribution near the chisel edge. Experiments have been implemented on the biglide parallel grinder and the helical drill point can be realized based on optimizing grinding parameters of the biglide parallel grinder. Therefore, the grinding helical drill can be obtained with the optimized parameters.

A proof of safety is paramount for an autonomous robotic surgical system to ensure that it does not cause trauma to patients. However, a proof of safety is rarely constructed, as surgical systems are too complex to be dealt with by most formal verification methods. In this paper, we design a controller for motion compensation in beating-heart surgery, and prove that it is safe, i.e., the surgical tool is kept within an allowable distance and orientation of the heart. We solve the problem by simultaneously finding a control law and a barrier function. The motion compensation system is simulated from several initial conditions to demonstrate that the designed control system is safe for every admissible initial condition.

This paper presents a comprehensive analytical model for a Z-shaped electrothermal microactuator operating in air condition. The model provides the estimate of the tip displacement of the microactuator directly based on a voltage difference applied on the both anchors of the actuator. In an attempt to improve the accuracy of modeling, the impact of the shuttle and multiple pairs of beams are included in the model. The numerical simulations with a Finite Element (FE) model are conducted using the commercialized FE software ANSYS to verify the analytical model. The experimental testing is performed as well to validate the analytical model. The analytical results based on the proposed model agree well with both the FE modeling and experimental results.

This work is aimed at a comprehensive discussion of experiments and numerical procedures for the open-loop geometric calibration of the KUKA LWR4+ redundant robotic arm, when a full 6D end-effector’s pose is measured using Nikon K610 optical coordinate measuring machine (CMM). The later includes a comparative analysis of three different conjugate-type and meta-heuristic iterative algorithms used for numerical optimization of two observability indexes associated with Jacobian properties of the manipulator kinematics. While the former is based an original LEDs fixture design, which geometry is important for organization of the experiment. To the best of our knowledge, such integrated efforts are new for the KUKA robot widely used in robotics research community.

This paper discussed the characteristic analysis of the novel tubular double excitation windings linear switched reluctance motor (LSRM), and the influence of this motor performance by different key parameters. Much of the work is accomplished by using finite element analysis method. The main contents include comparison of motor output force under the different condition of parameters, the flux linkage distribution and self induction electromotive force (EMF) when the motor running. In addition, the EMF can be used to apply sensorless technology into this machine.

Controlling complex mechanical systems is often a difficult task, requiring a skilled developer with experience in control engineering. In practice however, the theoretical difficulties of designing a good controller is only a first step as the implementation itself on the various pieces of equipment is also often challenging. This paper investigates if iterative learning control (ILC) can be used as an alternative to tuning existing controllers for improving system performance. This is evaluated by a case study on a high speed XY-positioning system used for laser cutting. An ILC algorithm is implemented by using a server client structure from Matlab. After tuning the parameters an implementation is found which is able to increase the tracking accuracy significantly for cutting speeds up to

$$0.5\;{\text{m}}/{\text{s}}$$

0.5

m

/

s

. This is done only by implementing code on the master control unit and thus without changing subsystem controllers.

Nowadays, with the construction of the railway has been more and more consummate and the environment requirements of the place where locomotive drives are also increasing, so the demand for a series of rail engineering vehicles have increased. In order to adapt for the various working condition of the rail engineering vehicles, so the rail engineering vehicles must have a good dynamic performance, and there need a hydraulic transmission device which used the hydraulic torque converter and the hydraulic coupler to control speed. In the transmission system, the hydraulic coupler and the hydraulic torque converter can switch flexibly. And this makes the rail engineering vehicles can deal with all kinds of different working conditions, and thus it improve the efficiency of the vehicle. This paper introduces the characteristics of the hydraulic torque converter and the hydraulic coupler, the selection of the shift gear parameters, strategy formulation of shift, and the principle of the shift strategy with optimal traction, thus we formed the final shift strategy.

RV transmission device is a new type of few teeth difference planetary transmission, which is widely used in robot joints, elbow and other precision transmission parts due to the high driving accuracy. Taking the RV-40E reducer as an example, transmission error dynamical model and mathematical equations of RV reducer used in robot were established using dynamic sub-structure method. The max transmission error of RV-40E reducer was calculated by theoretical calculation and experiment respectively. The max transmission error calculated from two methods changes periodically within 1′. But the experiment measured transmission error is greater than the theoretical transmission error, due to the bearing clearance and friction in the experimental process were not considered.

The insulator is a part of high-voltage power transmission lines. The security and reliability of power system is mainly determined by safe working of insulator. Moving mechanism of insulator inspection robot is developed to inspect potential risk and operating status of insulator, which has important application in power engineering. Considering the working condition of insulator and mobile program of existing inspection robot, a novel foot-simulated moving mechanism of insulator inspection robot is proposed. Mobile program and structural configuration are determined, structural parameters are designed and kinematics analysis are completed. Finally, a 3D virtual prototyping of the moving mechanism is built with Solidworks, the moving process on insulator string of the mechanism is simulated with Adams, kinematic performances are calculated by simulating. The simulation results verify structural rationality of the moving mechanism and correctness of kinematic analysis proposed in this paper.

This paper presents an overview of the design of the first full-scale prototype of the Atlas flight simulator motion platform for pilot training. The Atlas concept was introduced in 2005, and is unique in that orienting is decoupled from positioning, and unlimited rotations are possible about any axis of the mechanism. Detail design and manufacturing are complete, and assembly is in progress. The key to the design is three mecanum wheels in an equilateral arrangement, which impart angular displacements to a sphere that houses the cockpit, thereby providing rotational actuation. Since the Atlas sphere rests on these mecanum wheels, there are no joints or levers constraining its motion, allowing full 360° rotation about all axes, yielding an unbounded orientation workspace that is singularity free. In this paper, the current state of the design and assembly regarding actuation, the spherical S-glass shell, and modelling for motion control are discussed.

Developed an original method, which allows us to apply the finite element method to analyze the stiffness and strength of planar and spatial lever mechanisms with kinematic pairs of arbitrary orientation in space. The idea of the method is that the basic equation of equilibrium of a system of finite elements is made and solved in the local coordinate systems of nodes. This allows to take into account the lack of connections in the kinematic pair in any direction. For the finite element modeling is used also a method of hard knots.

In this paper, we focus on the need for the conceptual design of the intelligent lunar robot, and one kind of mechanical structure and compliance control methods are researched. Two-level shock absorber mechanism is adopted to effectively solve the question of the joint between four wheels of the robot and the ground at any road conditions. The control system consists of the on-board

PC

, the lower computer and the position feedback module. Each of them separately use the independent micro computer to process the system tasks in the distributed and parallel way. The experiments are carried on to test the performance of the intelligent lunar robot and the result shows that the whole system has the high precision and the rapid response. Simultaneously, this control system has strong computation ability and secondary development potential.

This paper introduces a four degree-of-freedom parallel robot producing three translation and one rotation (Schönflies motion). This robot can generate a rectangular workspace that is close to the applicable work envelope and suitable for pick-and-place operations. The kinematics of the robot is studied to analyze the workspace and the isocontours of the local dexterity over the representative regular workspace are visualized. The simplified dynamics is modeled and compared with Adams model to show its effectiveness.

In order to reveal the deformation state of elastomer actually, the fractal model of the M-B is modified, and deformation properties of elastic stage, elastic-plastic stage and plastic stage of elastomer are analyzed. From the combination of macro and micro perspective, the fractal model of contact stiffness between two cylinders’ joint surfaces is established considering the influence of friction, which is proofed to be feasible by numerical simulation. Moreover, the Fixed curved joint is taken as a research object, the dynamic model is established by the method of spring element, and the first 6 natural frequencies is obtained by the finite element analysis method. Finally, the natural frequency and model analysis obtained from theory and experiment are comparative analyzed. The results show that the established stiffness model is well suitable for the reality of joint surface. Then a new approach for the treatment of joint surface, which is largely present in robotics and NC machine tool etc. are completely provided.

This paper introduces a modular system consisting of a 3 DOF robotic local structure with revolute joints. Several wrist joints are presented where the contact element, the end-effector, is systematically varied. The range of objects to be handled is analysed with the aim to identify a minimum of contact principles. Realizing these principles with one gripper each and defining general interfaces leads to a modular system, which warrants the versatility, flexibility and reconfigurability required for the introduced parallel handling system.

The nonlinear dynamic characteristics of RV transmission device was investigated according to dynamics theory, mass centralized method was used to establish the nonlinear dynamical model of RV transmission device, which was composed of inertial component, elastic element and damping element. The influence of the nonlinear factors as meshing stiffness varying with time (though the variation in the number of meshing teeth), backlash of gear pairs and errors were considered. Movement differential equations of system were derived, and these equations were changed to non-dimension, which were solved by Runge-Kutta method. Influences of excitation frequency and damping on system dynamic characteristics were analyzed. As the excitation frequency increased, the system would vibrate from single periodic motion to harmonic motion, chaotic motion. Along with the reduced damping, chaos vibration occurs gradually after a doubling periodic of bifurcation, as the system gradually gets into the chaotic state. The impact is also changed from coexistence of non-impact and the unilateral impact to coexistence of the non-impact, unilateral impact and bilateral impact.

This paper presents compliance modeling and error compensation for lightweight robotic arms built with parallelogram linkages, i.e.,

$$\varPi$$

Π

joints. The Cartesian stiffness matrix is derived using the virtual joint method. Based on the developed stiffness model, a method to compensate the compliance error is introduced, being illustrated with a 3-parallelogram robot in the application of pick-and-place operation. The results show that this compensation method can effectively improve the operation accuracy.

Thin-walled and four-point contact ball bearings are key elements for industrial robots, since they play a critical role in the action accuracy, running stability and flexibility, and service life for the main engine of robots. In this paper, a new design method which involves structure optimization, finite element analysis and accurate service life calculation has been developed. FPXU408-2RZ bearing is applied as an example to describe the design method.

The paper presents the elastostatics analysis of a class of lower-mobility Parallel Kinematic Machines: the Spherical Parallel Machines. These robots usually recur to curved links in their structure to satisfy geometric constraints deriving from mobility reason. In fact, to make the mobile platform move with spherical motion all links or a part of these are constrained to have spherical motions too. This condition is generally obtained employing curved links with revolute pairs whose axes intersect at a common center of motion. Recurring to two-node Timoshenko’s beam element with constant strain fields to simulate curved beams in space we adapt a methodology proposed by the same authors to study the elastostatics of Spherical Parallel Machines. The method is finally applied to study the error positioning analysis of the Agile Eye.

This paper presents the accuracy analysis of a tripod parallel grinder. The manipulator structure was introduced and its inverse geometric problem was studied. The inverse Jacobian matrix of the tripod parallel grinder was obtained upon the differentiation of the loop-closure displacement equations. The influence of the geometric parameters to the accuracy of the tripod parallel grinder was investigated. Through simulation, the influences of link length error to accuracy were analyzed, which is the basis of error compensation and control for the machine tool.

GIM is a general purpose kinematics simulation program which was initially developed to compute and visualize the motion of mechanisms of any number of DOFs. In this motion simulation, at each mechanism position, the velocities and accelerations results are obtained and stored. This paper presents a new computation module recently added to the GIM program which is able to read those kinematic results in order to build the inertial efforts and simulate the inverse dynamics of the mechanism. All joint efforts are computed across the motion, so the free solid diagram of any link can be depicted at a specific position, as well as animated over time. In addition, for straight axis elements of the mechanism, the inertial forces are considered as distributed loads, and the internal efforts diagrams (axial and shear forces and bending moment) are traced. These results allow a further cross section dimensional design for such elements.

This paper presents a new and computationally efficient method for the modelling of flexible robot manipulators. The proposed method avoids the global dynamics by decomposing it to the component dynamics. The component dynamics is established, and is linearized based on the acceleration-based state vector. The transfer matrices for different type of components are created, and the systematic dynamics of a flexible robot manipulator is then established by transferring the state vector from the base to the end-effector without increasing the order of the system matrices. The numerical simulations of a flexible manipulator are conducted for verifying the proposed methodologies.

Focusing on the potential of one translational and two rotational (1T2R) parallel kinematic machines (PKMs) for high precision manufacturing, this paper carried out the first time a comparative study on the kinematic and static performance of two promising Exechon variants, named PAW and PAW-II. PAW has the topology with 2R

P

U-S

P

R while the topology of PAW-II is 2R

P

U-R

P

S. Herein, R, U,

P

, S denote revolute joint, universal joint, actuated prismatic joint and spherical joint, respectively. After introducing their architectures and inverse kinematics, two key performance characteristics, i.e. workspace and stiffness were conducted for the two PKMs. Comparative results show that PAW has a smaller workspace but better stiffness performance comparing to PAW-II.

The paper discusses the Forward Kinematic Model (FKM) of a special Spherical Parallel Manipulator (SPM). The special SPM is obtained by modifying one leg of a classic SPM. This new architecture eliminates the singularity from the workspace. The SPM is used as master device for medical tele-operation system. The FKM of the new SPM is calculated using the equation of spherical four-bar mechanism. A method to improve the FKM calculation using extra sensor is proposed in this paper.

In this paper, a parallel mechanism with six degrees of freedom is presented with capability for decoupled translational and rotational movements as a significant advantage for use in lifting and transport operations for measuring, assembly, manufacturing operations, working within a limited workspace. Direct and inverse kinematics is formulated for the proposed mechanism with the capability to provide rotational and translational in different operation modes.

This paper deals with the characterization of the operation modes of the 2-RUU parallel manipulator with an algebraic approach, namely the Study kinematic mapping of the Euclidean group

SE

(3). The manipulator is described by a set of eight constraint equations and the primary decomposition reveals that the mechanism has three operation modes. The singularity conditions are obtained by deriving the determinant of the Jacobian matrix of the constraint equations with respect to the Study parameters. It is shown that there exist singular configurations in which the 2-RUU manipulator may switch from one operation mode to another operation mode. All the singular configurations are mapped onto the joint space and are geometrically interpreted. Finally, the mechanism may switch from the 1st Schönflies mode to the 2nd Schönflies mode through the additional mode that contains self-motions.

This paper studies the possible configurations and singularities of 3-DOF spherical parallel mechanisms with revolute and prismatic pairs. In particular, the 2R1P spherical parallel mechanisms are studied, for which the kinematic models are established and Jacobian matrices are derived. Three kinds of singularities, namely the boundary, configuration and structure singularities, are identified and analyzed for RRP, PRR and RPR type of spherical parallel mechanisms. The results can be used for further modeling and analysis on workspace and trajectory planning of 3-DOF spherical parallel mechanisms towards the practical application of the kind of mechanisms.

In the paper kinematics of the independent 5-rod car suspension mechanism is analyzed to calculate camber and toe angles, lateral and longitudinal displacements that affect the performance of the whole vehicle guiding mechanism. The problem is solved numerically by multidimensional Newton method with regularization. The proposed regularization parameter provides acceptable problem conditioning and proximity to the original problem.