Mechanism, Machine, Robotics and Mechatronics Sciences

Polymers are widely used in machine design, biomedical engineering, aircraft, and mechatronics. Certainly, these products are subjected to thermo-mechanical loading. For this reason, dealing with the fatigue criteria for viscous polymers is essential. In fact, this requires a large number of cycles to reach the accommodated cycle. These materials have a thermoviscoelastic behavior that has already been studied within the Finite Element Method (FEM). However, a very large computation time or a non-convergence has been noticed. In this paper, we considered a 3D thermal problem under cyclic load in which three main parts are considered. Firstly, the problem is studied using the Proper Generalized Decomposition method (PGD) where it shows a gain in the computation time compared to the classical FEM with a relative error less than 5%. Secondly, different time scales are taken into consideration: the cyclic time (load) and the characteristic one (material properties), where different relaxation times lead to various responses of the polymer. A link between these times should be established. Finally, the effect of the spatial point position on the evolution of the temperature within the domain is investigated.

Metal cutting plays an important role in the industry, and as such, the mastery of machining processes has become an issue in the industrial sector. The understanding of the physical phenomena present during manufacture is an important factor in the optimization of a process of production by removal of material. The tool-part interface during a machining process is a place of complex interactions between mechanical, thermal and physicochemical phenomena. The temperature variable which changes according to the cutting parameters directly affects the quality of production. In our contribution, we propose an experimental measurement methodology, which makes it possible to obtain coherent temperature data at the tool-piece interface. This work will focus on two main activities:

Wireless Multimedia Sensor Networks (WMSN) engender a wide scope of important Machine-to-Machine video based applications. However, energy consumption in WMSN determines the complete network lifespan. Communication is the greediest energy consumption task which grows exponentially with the increase of transformed data. Even though video data is considered the richest information holder, it is the most energy craving data. In this paper, we propose a new Simple On-line Single-view video summarization mechanism (SOS). This mechanism adds a low-complexity video summarization task to the sensor nodes. Nevertheless, it reduces the transfer load of network through extracting only significant video information. Simulation results confirm the efficiency of our proposition in saving the life of WMSN. Resource consuming reduction reaches as high as 40%.

Since pipelines have become an important asset to the economic development of almost any country, maintaining and conserving them is a must. Some of the methods used to maintain them are as simple as inserting a tube with a camera to find the defective part of the pipeline or continuous digging to assess and find the problem. However, most methods currently used involve taking risks to reach inaccessible areas in a pipeline. The proposed semi-autonomous pipe inspection robot is designed to navigate through tight areas inside a pipe, with the ability to adapt to different pipe sizes and report the state of the pipe and the nature of any problem found. This robotic system adapts easily to the cylindrical shape of a pipe and runs on DC geared motors that provide the required torque for the robot to ascend vertically if needed. In addition, this particular robot does not only work by user command but can also be configured to run specific autonomous tasks. The sensor data collected is stored on a router acting as a web server that can be monitored by the user and accessed in addition to the live-feed provided by the IP camera mounted on the robot. The robot’s design and control interface provide easy and safe access to tight and distant areas of a piping system. This robot has proven to solve risky, time-consuming and expensive maintenance procedures.

Solar energy market is growing rapidly and presenting a high energy share. We can find many applications of solar energy harvesting systems like Photovoltaics, Dual Face Photovoltaics, Concentrated Photovoltaics, and Concentrated Solar Power. All these systems need tracking technology to increase their efficiency or total output. We present in this paper an innovative sensorless tracking algorithm for PV panels where we track the sun’s position without using a sensor. The algorithm has been implemented on a Beckhoff PLC and a small PV module has been used to test the system.

Recent technical advances in minimally invasive surgery have been enabled by the development of new medical instruments and technologies. To date, the vast majority of mechanisms used within a clinical context are rigid, contrasting with the compliant nature of biological tissues. The field of robotics has seen an increased interest in flexible and compliant systems, and in this paper we investigate the behaviour of deformable multi-segment structures, which take their inspiration from the ovipositor design of parasitic wood wasps. These configurable structures have been shown to steer through highly compliant substrates, potentially enabling percutaneous access to the most delicate of tissues, such as the brain. The model presented here sheds light on how the deformation of the unique structure is related to its shape, and allows comparison between different potential designs. A finite element study is used to evaluate the proposed model, which is shown to provide a good fit (root-mean-square deviation 0.2636 mm for 4-segment case). The results show that both 3-segment and 4-segment designs are able to achieve deformation in all directions, however the magnitude of deformation is more consistent in the 4-segment case.

This paper deals with the control of a lower limb orthosis. In which a model of the shank-orthosis system is given, we consider the human effort as external torque acting on the system. A comparative study, through a number of simulations in different operational scenarios, highlights the limits of a standard PID controller. On another hand, this work brings out the benefits of orienting the control strategies toward model reference approaches. Hence, a better exploitation of the nonlinear system dynamics; by deriving adaptive control strategies to enable the management of parameters uncertainty could be a relevant approach for such systems.

This paper presents a robust sliding mode algorithm developed to control an exoskeleton used for rehabilitation of the upper limb. The considered system is a robot with three degrees of freedom controlling the flexion/ extension movement of the shoulder, the elbow and the wrist. A Monte Carlo simulation is done to analyze the robustness of the controller against matched and unmatched disturbances. Simulation results are provided to prove the performances and the effectiveness of the sliding mode algorithm face to disturbances.

Magnetorheological fluid is a smart material which can change its viscosity in milliseconds depending on the magnetic field applied. This brings a great advantage to create variable damping ability if it is used in an absorber. The stiffness of the absorber can be manipulated by an external magnetic field which effects the apparent viscosity of the magnetorheological fluid inside the absorber. Various control algorithms can be used to provide an effective absorption for any kind of structural vibration. Because of these features, magnetorheological absorbers have received great attention of researchers in the last decade. In this study, it is aimed to simulate a magnetorheological absorber under a sinusoidal vibration with Computational Fluid Dynamics and Magnetic Field Finite Elements Analysis. The magnetorheological fluid is modelled as a Non-Newtonian fluid and Herschel-Bulkley viscosity model is used to determine the apparent viscosity. Magnetic field is modelled for a constant current which generates different magnetic flux densities inside the absorber body. The Computational Fluid Dynamics and Finite Elements Analysis solutions are coupled in a two-dimensional axisymmetric domain and the results are revealed. The coupled solution of both are realized for the first time in the literature by means of an apparent viscosity approach. The numerical solution is compared with the experiments. A good agreement is observed between both results.

While the machine is running, damaged components of the bearing trigger vibrations in the structure of the machine when it contacts other surfaces. These components appear at specific frequencies dictated by the geometry of the bearing and its rotation frequency. An autonomous fault detection method is therefore needed to improve the performance and the reliability of the mechanical system. This article aims to present an autonomous bearing fault detection process. This process takes into account the slip phenomenon by calculating a normalized indicator related to the existence of a bearing fault in a narrow band centered at the theoretical frequency. The latter is calculated from the geometry of the bearing, after preprocessing steps in order to equalize the baseline spectrum and to set an appropriate statistical threshold. An application on real data from the IMS database will be held at the end in order to detect and classify mechanical faults.

The aim of this paper is to present a sensitivity study of the effect of the geometrical changes on the vibration behavior of an electric machine at the stator level. A wound rotor synchronous machine is chosen here. A finite element model (FEM) of tetrahedral elements of the stator is created using ANSYS-APDL. This paper, based on the changed geometrical parameter, presents 2 studies: Variation of the stator yoke thickness and the variation of the stator yoke thickness while keeping the same mass. In both studies, the decrease in the yoke thickness leads to the decrease in the natural frequencies although the mass remained constant. The decrease in the yoke thickness increases the stator flexibility which means that the stiffness is more effective than the mass.

This paper deals with control of parallel robots, where different controllers are proposed and compared. It demonstrates the strength of model-based controllers over the non-model-based ones when dealing with parallel kinematic manipulators known with their high nonlinearity, time-varying parameters and uncertainties. More precisely, adaptive model-based algorithms are the preferred control solutions for such kind of manipulators, thanks to their adjustable-parameters feature which is more adequate to the varying and non-accurate nature of parallel kinematic manipulators. These facts are fulfilled here by numerical simulations and real-time experiments on a four-degree-of-freedom parallel robot named VELOCE.

This paper presents a delta robot used in a waste sorting system, where its role is to separate plastics and glass from the main waste line. A special detector gives the position and the timing. The trajectory of the picked parts respects the continuity of velocity and acceleration. The pick and place algorithm aims to reach the maximum number of removed items per minute. The inverse kinematics model helps to find the trajectory in the joint space as well as the maximum value of the acceleration. Finally a prototype of the model is presented.

Structural synthesis of kinematic chains and multiple DOF multiloop mechanisms with specified input parameters is the first and the most important stage in the mechanical conceptual creative design of robots. This paper proposes a new approach to structural synthesis and creative design of closed-loop robotic mechanism with simple and multiple joints based on an original addition synthesis method. First, the structural synthesis method of non-fractionated and fractionated multiple joint kinematic chains with the smallest closed loop is presented. Then, the complete atlas database of all feasible 12 types of 2-DOF, 7-link, 2-basic (independent) loops generalized simple and multiple joint kinematic chain and corresponding atlas of hinged mechanisms are obtained. Third, based on classified atlas databases of kinematic chains and mechanisms with simple and multiple joints, a creative design method is proposed to obtain all the feasible mechanisms for a specified task. Finally, examples of the creative design of single arm robot manipulators are also conducted to demonstrate the effectiveness of the proposed method.

In this paper, the systematic method is developed to synthesize planar closed kinematic chains with all the possible kinds of multiple joints according to given K-independent loops and up to total multiple joint factor V_max. First, the structural synthesis method of multiple joint kinematic chains based on the combination of corresponding simple and multiple joints is presented. Then, the complete atlas database containing all valid multiple joints in closed fractionated kinematic chains with up to 5 independent loops and up to 12 links is established and illustrated. Further, corresponding all possible 14 types of multiple joint assortments up to K = 5 and up to total multiple joint factor V_max = 8 are obtained and classified in the tables for the first time. Next, the structural analysis of multiple-jointed fractionated kinematic chains with various total multiple joint factors is conducted, and main structural parameters are determinated. Finally, based on atlas database of synthesized kinematic chains with multiple joints, the examples of creation of robot manipulators are provided.

Inertia is one of the most annoying problems in robotics. Cable driven mechanisms are characterized by their low inertia. However, when an epicyclic train is used, kinematics becomes very complicated. This paper shows a wrist, driven by a pulley tendon system. A generalized form for the Willis formula is developed. The pulley arrangement is done, such as, there is a direct driving between the fixed actuator on the frame and the link connected to the last pulley.

In this paper, an Active Fault Tolerant Control (AFTC) scheme for quadrotor UAVs suffering from actuator loss of effectiveness fault is presented. The AFTC is based on Passive Fault Tolerant Controller (PFTC) bank that contains a group of Sliding Mode Controllers, each one tuned to give the best performance for a specific fault. Whenever a fault is detected and identified, the relevant PFTC is activated resulting in the fault effect kept minimum. State estimation is ensured using an Extended Kalman Filter, and fault detection and estimation process is realized using a Fault Detection and Identification (FDI) unit that examine the changes in the control signals. Simulation results using an Astec Pelican quadrotor model emphasize the effectiveness of the proposed controller in the presence of multiple actuator faults.

Quadcopter positioning in indoor environments is considered a major problem because of the difficulty of estimating a reliable position. Moreover, the positioning system is expected to work in real-time and to be accurate and cost-effective. In this paper, a combination of image processing techniques and neural networks is proposed to obtain the quadcopter position along the X, Y and Z coordinates. Three neural networks were used, one for each dimension. The proposed neural network based technique estimates the quadcopter target position along X, Y, and Z from two image points extracted from images captured by two low-cost IP cameras. The offered positioning system has been implemented on a locally designed and assembled quadcopter. Hovering experiments on the quadcopter have been performed in an indoor lab based environment. The results show that combining image processing techniques with neural network-based method achieves a low-cost accurate positioning system within a precision of a few centimeters with a frequency of 16 Hz.

Correct mobile robot localization requires precise knowledge of the robot’s pose in plane, i.e. the Cartesian x and y coordinates and yaw angle \( \theta \). Mobile robot pose information estimated from on-board odmetry sensors is not fully trusted and it suffers from unceratinties exerted by the robot incorporated with actuators nonlinearities and robot mechanical complexities which lead to a low degree of believe (DoB) of the robot localization. The present paper provides Unscented Kalman Filter (UKF) based approach assisted robot localization to provide trusted information with high DoB for the mobile robot’s pose. Particularly, estimating the current situation of the robot navigation system is complex due to the above mentioned phenomenons. An efficient and accurate estimation technique which applies probabilistic algorithm based UKF is proposed. The proposed technique is implemented and verified using MATLAB/SIMULINK®. Both practical and simulation results have demonstrated the vitality of the proposed estimation approach.

Recently trajectory tracking control of a quadcopter has been paid attention by academic and industry. This paper proposes two different strategies for trajectory tracking control of a quadcopter system implementing nonlinear control theory. The first approach is based on the integral backstepping technique, the second proposed one is an LQI (Linear Quadratic Integral) optimal controller with a feedback linearization so as to deal with the nonlinearity and the coupling components of the quadcopter state variables. The control laws for trajectory tracking using the proposed two strategies were validated by simulation and experimental results obtained from a quadcopter test bench. Simulation results show a comparison between the performance of each of the two control laws depending on the nonlinear model of the quadcopter system under investigation; the trajectory tracking has been achieved properly for different types of trajectories in presence of unknown disturbances. Simulation and practical results have shown coincided tracking with the command signals of the desired attitude. Superior tracking control has been exhibited with the proposed LQI optimal controller. It has been also noted that the proposed control approach exhibits an inherited decoupling control action, for which the control of one axis angle has relieved the dynamic coupling effect on the other two axes. Furthermore, intensive practical results have demonstrated the robustness of the proposed controller.