SimMechanics Environment Research Articles

РЕШЕНИЕ ПРЯМОЙ ЗАДАЧИ КИНЕМАТИКИ ДЛЯ ШЕСТИЗВЕННОГО РОБОТА-МАНИПУЛЯТОРА

The study describes steps to solve the direct kinematic problem for a six-unit robot manipulator, the FANUC Robot M-20iA/35M. The problem solving is based on modern solid CAD modeling technologies combined with a physical modeling environment, as well as Simulink’s SimMechanics multi-unit spatial mechanisms. Simulink’s SimMechanics environment is used for visualizing the dynamics of the manipulator’s operating component. The manipulator’s matrix equation can then be used for solving the inverse kinematic problem.

Active torque-based gait adjustment multi-level control strategy for lower limb patient–exoskeleton coupling system in rehabilitation training

This paper proposes an active torque-based gait adjustment multi-level control strategy for lower limb patient–exoskeleton coupling system (LLPECS) in rehabilitation training. The proposed controller has three levels of high, middle, and low sub-controllers: gait adjustment layer (high-level), interaction torque design layer (middle-level), and trajectory tracking layer (low-level). The high-level sub-controller uses an adaptive central pattern generator (ACPG) to adjust the desired gait for rehabilitation training according to the patient’s active torque. In the middle-level sub-controller, the desired interaction torque is designed with neural networks and the estimated muscle torque by utilizing nonlinear disturbance observer (NDO). In the low-level sub-controller, a time delay estimation-based prescribed performance model free control is designed for the accurate tracking performance of the exoskeleton, so as to make the actual interaction torque track the desired value. An exoskeleton virtual prototype, which is developed in SolidWorks, has been imported to MATLAB/Simulink to conduct co-simulations in the SimMechanics environment. The results of co-simulations demonstrate the effectiveness of the proposed control strategy when the patient’s muscle torque is at different recovery degrees.

FiMec tremor stabilization spoon: design and active stabilization control of two DoF robotic eating devices for hand tremor patients.

This article is about vibration-damping robotic eating devices designed for use by people who have difficulty in eating due to hand tremors due to neuromuscular system disorder. The robotic eating device has two degrees of freedom (DoF). It contains an active controller structure to absorb vibrations in the y- and z-directions. In the handle part of the robotic eating device, there are two DC motors placed on the y- and z-axis, a three-axis IMU inertia sensor, an embedded system board, and a power unit. To absorb the vibration measured from the IMU sensor, the position control of the two motors to which the spoon is connected is provided by PID controllers. The part of the spoon (the pit surface) where the food is placed is tried to be kept constant. To test the vibration-damping performance of the control method, the dynamic model of the spoon along the eating kinematic trajectory was simulated in the SimMechanics environment using vibration data from ten tremor patients. The results show that the stabilization method can absorb the vibration in the hand of the person in the range of 84-99.409% and successfully provide the stabilization of the spoon tip. This damping rate is promising for providing a healthy diet for hand tremor patients.

Pareto front generation for integrated drive-train and structural optimisation of a robot manipulator conceptual design via NSGA-II

Due to the complexity of the process, there is no single solution for determining the motors, gearboxes and structures of a robot manipulator according to the desired dynamic performance while minimising both the deflections in the structure during the dynamic motion and total robot weight. The solution of this integrated drive-train and dynamic structural optimisation problem is generalised for three degrees of freedom (DOF) robot manipulator via Non-Dominated Sorting Genetic Algorithm II (NSGA-II) to obtain the Pareto front of any desired robot manipulator overall conceptual design, including motors, gearboxes and thicknesses of the links. A flexible body dynamic simulation model was created in the MATLAB Simmechanics environment. The flexible bodies were defined via lumped parameter estimation method, which allows observation of the deflections in links during the dynamic motion. A library containing technical data related to motors and gearboxes was created to be utilised in the optimisation algorithm. The method accelerates the time-consuming iterative process for obtaining optimum conceptual design solutions for a dynamic system and allows for easy modification of design parameters and constraints. It also makes the algorithm suitable for different types of dynamic system designs.

Fuzzy logic-based tuning of PID controller to control flexible manipulators

Flexible manipulators are widely used in overhead cranes for industrial purposes and accurate control of the tip point of such a system is very difficult. Control of a 6DOF flexible manipulator is attempted in this study. Model of the manipulator is built in sim-mechanics environment of MATLAB and simulated. Joints of the manipulator are made flexible with the use of joint spring and damper. The behavior of the system was found to be unstable and a controller was used to bring the stability. For this purpose, a conventional PID controller was used and its gain values are tuned using different approaches in this study. Finally, a manually designed fuzzy logic-based approach was also used to tune the PID gains and compared with that of the conventional tuning approaches. In order to apply controller to the system, equivalent linearized transfer function of the model is derived in MATLAB. Among all the conventional tuned PID controllers applied, RRT-based method has performed best in terms of phase margin and gain margin. Also, the performance of fuzzy logic-tuned PID controller was found to be better compared to the conventional PID tuned controllers.

DYNAMIC ANALYSIS OF THREE DIFFERENT HIGH BAR DISMOUNTS IN THE SIMMECHANICS ENVIRONMENT

This study compares certain kinematic and kinetic parameters in giant circles performed before twisting, double stretched and double tucked dismounts using the dynamic model in the SimMechanics environment. The joint moments calculated using the designed model were investigated for the three different dismounts. The study included a 13-year-old voluntary national gymnast with seven years of training history. Markers were placed on the wrist, elbow, shoulder, hip, knee and ankle joints of the gymnast. The gymnast was asked to perform twisting, double stretched and double tucked dismounts. MATLAB and SimMechanics were used to calculate joint moments. The moves were simulated and the joint moments during the moves were calculated using the SimMechanics toolbox. The study observed that the highest joint moment was in the wrist joint in all three dismounts, in line with the findings of previous studies. However, unlike other studies, higher joint moments were calculated in the accelerated giant circle performed together with thrusts, compared with the regular giant circle. While there were similar maximum moment values in twisting dismounts and double tucked dismounts, an almost three times higher moment was observed in double stretched dismounts. In terms of joint moments, stretched dismount is obviously the most difficult move, which is consistent with the difficulty levels. A recorded performance of the mechanical model created in the SimMechanics environment was investigated in terms of the twist angle and moments generated on the bar, and found to be sufficient and useful. However, there are certain restrictions regarding the methods employed in this study. We concluded that the mechanical model will allow for the performance of kinematic and kinetic analyses of different gymnasts and types of moves thanks to its flexible structure.

Evaluation of inverse dynamics of hexarot-based centrifugal simulators

Dynamic modeling is necessary for design, optimization, simulation and control of mechanisms. This paper presents the evaluation of the inverse dynamics model which has recently been developed based on the Newton–Euler approach for a hexarot manipulator. The evaluation is performed under SimMechanics environment. By comparing the results of the analytical and SimMechanics models, it is found that the both the models are accurate and reliable.

Modeling the dynamics and control of rehabilitative exoskeleton with robotic crutches

Rehabilitative robotics is an area in the medical field, where one can see a variety of different robotic applications, one of which is the use of robotic exoskeleton in rehabilitation of paraplegics. Current developments are only able to support paraplegics at most and require manual operation of crutches by the patient. In order to overcome this limitation, a theoretical model of a robotic device with actuated robotic crutches is proposed, which can be used to support people with high-level disability, such as quadriplegics who cannot use the existing solutions to perform walking gaits. This work presents kinematic trajectory planning of the proposed model and dynamic analysis of main movement stages. Finally, we present an open-loop control scheme that uses time scaling in order to track the desired joint trajectory of the under-actuated motion stage of crutch swinging. A simulated robotic model has also been developed using Simulink [version R2012b to R2014a]/SimMechanics ([version first generation] developed by Mathworks inc.) environment and has been used for verifying dynamic computations and simulating the robotic device movement under the open-loop control commands of joint torques.

LMI-based 2-DoF control design of a manipulator via T-S descriptor approach

Abstract This paper presents a method for the control design of a manipulator. The design goal is to achieve a guaranteed H∞ model reference tracking performance with respect to bounded reference inputs through a 2-DoF control scheme. To achieve this goal, the manipulator system is represented by a Takagi-Sugeno fuzzy model in descriptor form. The control scheme is based on a parallel distributed compensation controller. Furthermore, the stability of the nonlinear system is also guaranteed. Based on Lyapunov stability theory, the control design is formulated as an LMI optimization problem which can be effectively solved with numerical solvers. Simulation results carried out with the SimMechanics environment clearly demonstrate the effectiveness of the proposed method.

Improvement of the method of calculation of the parameters of the universal current collector with the increased motion speeds

The paper considers the main stages of development of a computer model of current collectors of an electric rolling stock. The original description of the kinematic scheme of a universal measuring current collector with the subsequent implementation of mathematical model in Matlab SimMechanics environment is offered. The model is based on the use of the method of homogeneous coordinates to represent the kinematic scheme of the current collector. It is shown that the computer model accurately and adequately describes the processes occurring with the current collector, is a universal instrument for simulating any types of current collectors, allows changing a wide range of parameters and characteristics incorporated in it.

Studies on Stewart platform manipulator: A review

This paper presents a compilation of previous studies on the Stewart platform, which is a class of six degree of freedom parallel manipulators. The abstraction of a parallel manipulator is appropriated for the entire class of it. The paper focuses on the studies in the different fields which are closely checked to determine the direction of research and identify the solved problem areas. A significant investigation has been presented to discuss the existing methods for the analysis of the Stewart platform manipulator due to their unique applications. Studies on analysis and design of the Stewart platform manipulator using flexible joints are included. Modeling and analysis of parallel manipulators by Matlab SimMechanics environment are also highlighted.

DYNAMIC MODEL AND SIMULATION OF ONE ACTIVE JOINT ROBOTIC FISH

This study considers the dynamic model of one active joint robotic fish by using Lagrange method and simulation of the robotic fish model in MATLAB/SimMechanics environment. Compared results of these two different models are given in the study. The mathematical model of the system is derived from Lagrange energy equations of the robotic fish inspired from a real carangiform fish. The Computer Aided Design (CAD) model of the robotic fish is designed by using SolidWorks and it is transferred to the SimMechanics environment. The hydrodynamic effects, which are linear and nonlinear drag force, are also adapted and head motion, one active joint, and one passive joint angles found by using MATLAB Simulink environment. Obtained results for joint angles from both dynamic and SimMechanics models are compared and proved with animation video of the robotic fish.

Kinematic Modelling and VR Simulation of a 3DOF Medical Parallel Robot with One Decoupled Motion

The robot studied in the paper has a 3DOF parallel structure of type 1PRRR+2PRPaR, with two coupled motions and one decoupled motion, composed by a mobile platform connected to the fixed base by three kinematic chains (one open kinematic chain of Prismatic Revolute Revolute Revolute type and two kinematic chains of Prismatic Revolute Parallelogram Revolute type). An analytical kinematic modelling of the parallel robot of type 1PRRR+2PRPaR is firstly presented in this paper, followed by a numerical simulation of the closed-form kinematic model and by a Virtual Reality (VR) application with control aspects. An innovative user interface for high-level control of the parallel 1PRRR+2PRPaR type robot is developed in MATLAB - Simulink and SimMechanics environment.

ANÁLISIS Y MEJORAS EN EL DISEÑO DE UN MECANISMO CINEMATICO DE ALTA PRECISIÓN

A new design for reducing the kinematic mechanism error is presented in this paper. Firstly, a prototype having a universal joint is presented and the kinematic model in the Simmechanics environment of Matlab is described, studying the system behaviour by means of simulation. Then, the manufacturing and assembly of the platform is performed and the mechanism performance is evaluated. To do this, different tests are carried out in which the mechanism backlash and the influence of the elevation angle and the misalignment in every axis due to backlash are analyzed. Finally, the mechanism design is improved by replacing the universal joint with a new element that consists on bearings and precision locknuts. This element allows us to obtain the two desired degrees of freedom. The replacement of the commercial universal joint by the developed element implies a considerably increment of the mechanism accuracy. The developed platform has many applications in the industry, such as, machining tool processes, high range metrology, holder base for measurement tools such as topography instruments, mirror orientation in telescopes, etc.

Validation of Contact Wire Simulations on the Basis of Scaled Down Contact Wire Cutting Experiments

As the requirements for overhead contact line systems increase due to higher train speeds, the need of safety equipment for these systems increases as well. Developing a component for the case of a contact wire cut to prevent further damage from the overhead contact line system requires an extensive knowledge about the system behaviour. Therefore, a comprehensive multi body system model (MBS) is developed in Matlab SimMechanics environment. In order to validate the datas generated from the simulations, a contact wire test stand has been constructed where cutting experiments can be run by releasing a pretensioned wire. Consequently, the force distribution during the contact wire cut is analyzed and these values are compared with the simulation results. For the comparisons, much attention is given to the period after the contact wire cut.

Comparative Dynamic Analysis of Two Parallel Robots

The paper presents a comparative dynamic modeling and VR (virtual reality) simulation for two 3 DOF medical parallel robots: a three coupled motions structure (Orthoglide robot) versus two coupled motion parallel structure (robot of type 1PRRR+2PRPaR). Kinematical and dynamical models, followed by a VR application with control aspects are presented for these two parallel robots. The innovative user interface for high-level control of the two parallel robots, presented in the paper, was developed in MATLAB - Simulink and SimMechanics environment, while the closed form dynamic models were obtained in MAPLE program. This kind of parallel robots can be successfully applied for medical applications where accuracy and high dynamic behavior are required. This research will lay a good foundation for the development of medical parallel robots.