6-DOF Parallel Robot Research Articles

Modelling and Simulation of Forward Kinematics for Planar 3-DOF Parallel Robot Based on Simulink

Parallel robots are widely used in the machinery industry. In this paper, a planar 3-RRR parallel robot is researched. The forward kinematics mathematical model is established for this kind of mechanism. On the basis of it, a relevant simulation is carried out through MATLAB/Simulink. Thus, the motion rules and stress state for all parts of the mechanism are described vividly The simulation results show that this method is much more effective and efficient when the simulation is implemented for a certain machine system. Meanwhile, it provides a theoretical foundation and a better analytical approach of simulation for the design and analysis of complex multi-linkage mechanisms in the future.

Real-time Pose Measurement of Parallel Robot Based on GRNN

The real-time pose measurement of parallel robot helps to achieve the closed loop pose control and improve the control and operating performance of parallel robot. But it is difficult to implement the real-time pose measurement directly. In order to solve the pose measurement problem of a 6-DOF parallel robot, the kinematics analysis of the parallel robot is made, and a Generalized Regression Neural Network which has fast convergence and strong nonlinear mapping ability is established by setting the desired pose and its inverse kinematics results as the neural network training samples to implement the map of parallel robot from the joint variable space to the work variable space. Finally, the real-time pose measurement of parallel robot is achieved by using the trained neural network and the actual motion states of the active joints easily detected. The simulation experiment results show that the method of measuring the parallel robot pose based on the GRNN has the faster convergence rate and higher measurement accuracy than those of the BPNN and RBFNN methods. The research establishes the basis for the direct closed control of parallel robot pose. DOI: http://dx.doi.org/10.11591/telkomnika.v11i5.2455

Adaptive Controller for 6-DOF Parallel Robot Using T-S Fuzzy Inference

DOF parallel robot always appears in the form of Stewart platform. It has been widely used in industry for the benefits such as strong structural stiffness, high movement accuracy and so on. Space docking technology makes higher requirements of motion accuracy and dynamic performance to the control method on 6-DOF parallel robot. In this paper, a hydraulic 6-DOF parallel robot was used to simulate the docking process. Based on this point, this paper gave a thorough study on the design of an adaptive controller to eliminate the asymmetric of controlled plant and uncertain load force interference. Takagi-Sugeno (T-S) fuzzy inference model was used to build the fuzzy adaptive controller. With T-S model, the controller directly imposes adaptive control signal on the plant to make sure that the output of plant could track the reference model output. The controller has simple structure and is easy to implement. Experiment results show that the controller can eliminate asymmetric and achieve good dynamic performance, and has good robustness to load interference.

Remote Laboratories for Education and Research Purposes in Automatic Control Systems

This paper describes the experiences using remote laboratories for education and research in the field of Control Engineering. The use of remote laboratories for education in subjects of control is increasingly becoming a resorted method by the universities in order to offer a flexible service in schedules with greater and better operation of available resources. Nevertheless, for research activities, remote laboratories are not widely used. The aim of this contribution is thereby to apply the experience of remote laboratories in research applications in order to share complex equipments among different researchers. Some experiments are carried out to demonstrate the effectiveness of using remote laboratories in research experiments related to robotic system. The results of the implementation of remote experimentations to control a 3-DOF parallel robot by using Distance Laboratory System (SLD) are exposed. The performance of the system is evaluated by the possibilities and functionality of the proposed remote laboratory platform.

Two DOF Parallel Robot Design and Dynamics Simulation for Quick Picking

This paper presents a new design approach of parallel robot for quick grasp based on parallelogram mechanism，and derives the dynamics model. Using SimMechanics toolbox and simlink toolbox in Matlab Software, and guiding the three dimensional solid model into it, the dynamics simulation and control on two DOF parallel robot is designed and studied. The experimental results show that the design mechanism obtains the anticipated requirement.

Hardware-In-The-Loop (HIL) Simulation Used for Testing Actuation System of a 2-DOF Parallel Robot

This paper focuses on the subject of Hardware-in-the-Loop (HIL) simulations from mechatronic systems design perspective. HIL is a real-time simulation where real subsystem parts of a complex engineering system are coupled together with the numerical models of the remaining subsystems to form its complete representation. In a HIL simulation there are three main components: simulated components, dedicated hardware systems and real components. An impediment in using this method is the high cost of necessary hardware. The paper presents an economical alternative to existing dedicated hardware systems by using the development board FiO Std. Using this board, a HIL simulation aimed at analyzing the control and actuation system of a 2-DOF parallel robot is presented in this paper. The HIL simulation includes two models: a target model (running on FiO Std board) and a host model (running on MATLAB/Simulink). The dynamic model of the robot mechanical structure (simulated part) is implemented in host model and then coupled together with two servo-motors (real parts) through target model to form a complete representation of the studied system.

A Robotic Cadaveric Gait Simulator With Fuzzy Logic Vertical Ground Reaction Force Control

Lower limb dynamic cadaveric gait simulators are useful to investigate the biomechanics of the foot and ankle, but many systems have several common limitations, which include simplified tendon forces, nonphysiologic tibial kinematics, greatly reduced velocities, scaled body weight (BW), and, most importantly, trial-and-error vertical ground reaction force (vGRF) control. This paper presents the design, development, and validation of the robotic gait simulator (RGS), which addresses these limitations. A 6-degrees-of-freedom (6-DOF) parallel robot was utilized as part of the RGS to recreate the relative tibia to ground motion. A custom-designed nine-axis proportional-integral-derivative (PID) force-control tendon actuation system provided force to the extrinsic tendons of the cadaveric lower limb. A fuzzy logic vGRF controller was developed, which altered tendon forces in real time and iteratively adjusted the robotic trajectory in order to track a target vGRF. The RGS was able to accurately reproduce 6-DOF tibial kinematics, tendon forces, and vGRF with a cadaveric lower limb. The fuzzy logic vGRF controller was able to track the target in vivo vGRF with an average root-mean-square error of only 5.6% BW during a biomechanically realistic 3/4 BW, 2.7-s stance phase simulation.

The Research on the Quick Method for 6-DOF Parallel Robot Forward Kinematics

6-DOF parallel robot forward kinematics can be achieved by Newton-Raphson method with more accurancy, but the result depends on the offer of initial value. It can definitely calculate the result by genetic algorithm, however, more evolved algebra is needed to make it more accurate, and sometimes it hardly meets the requirement by concurrent control. This article points to use the result of genetic as the initial value of algorithm, and ultimately make use of iteration to complete the forward kinematics. High accuracy and speed are the main features of this calculation, and another one is interpreting from the implementation point of view, which is very practical and meet the concurrent control through experiment.

Research on High-Precision Measurement of Position and Orientation of 6-DOF Parallel Robot Based on Stereo Vision and Positional Solution

In the paper, both stereo vision and positional solution are used to measure the position and orientation of 6-DOF parallel robot. Firstly, moving platform is segmented from the background based on temporal and spatial union algorithm, rough position and orientation of moving platform are obtained by feature point extraction and match; secondly, rough length of supported leg is calculated according to rough position and orientation of moving platform; finally, accurate position and orientation of parallel robot are calculated using both actual length measured by sensors and positional solution. Experiment results demonstrate that the position and orientation calculated by the above algorithm have high accuracy.

Motion Error Analysis for A 3-DOF Parallel Robot

Motion accuracy is one of the key point for parallel robots. In the paper, error modeling and motion error analysis of a 3-DOF parallel robot 3-PRS has been studied in this paper. First, the 3-PRS parallel robot and its kinematics has been introduced with its kinematics analysis. Based on the reverse kinematics analysis of 3-PRS, the motion error has been modeled. Then, motion error analysis has been performed for 3-PRS. The analysis results show the clear tendency of structural error effects on the motion errors.

Design and analysis of a 6-DOF mobile parallel robot with 3 limbs

Mobile parallel robots (MPR), which structurally configured a moving platform and several parallel limbs with an actuating wheel at the end of each limb, exhibit advantages in high mobility, high load capability and high flexibility in complex task environments. In this paper, a 6-DOF MPR with 3-PPUU (Prismatic-Prismatic Universal-Universal) limbs is proposed. The structural scheme and inverse kinematics are first presented; the orientational workspace and the dexterity of the MPR are analyzed in detail. A parametric optimal design model is then developed; the optimal scheme of the MPR is obtained. The constant-posture control scheme and algorithm are also proposed in this paper. A prototype of the 3-PPUU MPR with omni-orientational wheels is developed and the precision for both translation and orientation of the prototype is measured by experiments, which verify the feasibility of the proposed MPR scheme.

Actual Motion of 3-DOF Parallel Robot

The Lower DOF parallel robot rely on strictly geometrical constraints of axis of pairs in and between limbs to obtain the reduced number of DOF .In practice ,these constraints will never been perfectly fulfilled due to the inevitability of errors, and hence produce series bad effects and problems. Using screw theory and set theory as mathematical tools, the DOF and constraint system of 3-CRR parallel robot, were systematically summarized and in-depth studied. Kinematics design of a limited DOF parallel robot, a 3-CRR pure translational parallel robot, is presented that takes into account the error. The errors presented in the paper consist of two kinds. The errors is defined as the position error of rotation center of the platform caused by errors in the kinematics constants, such as axis error The above research results provided an insight into the error of 3CRR parallel robot.

Use of an orthogonal parallel robot with redundant actuation as an earthquake simulator and its experiments

In this article, an orthogonal 6-degree-of-freedom (DOF) parallel robot with redundant actuation is studied as an earthquake motion simulator. Taking the practical simulation of earthquake waves into consideration, the general characteristics of natural earthquakes are analysed and complexity and variety of seismic waves, three-dimensional and multi-DOF movement, and strong devastating force are regarded as the three obvious features in this article. Based on the characteristics of this orthogonal 6-DOF parallel robot with redundant actuation and the features of earthquakes, the feasibility of using this parallel robot as an earthquake motion simulator is analysed from three aspects: orthogonal 6-DOF structure, decoupling feature, and redundant actuation module. In order to simulate an earthquake motion using this parallel robot, its inverse kinematics and dynamics models are derived. The control system of this earthquake simulator is developed based on the PXIbus development platform. The computed-torque control algorithm based on the inverse dynamics is used in the controller of this equipment. A typical three-directional earthquake motion, the El Centro earthquake, is simulated on the end-effector of this parallel robot by means of its mathematical models and control system. Three main motion parameters of simulated seismic waves, displacements, velocities, and accelerations, are measured, respectively, by laser tracker and acceleration sensors. The experimental results show this equipment is appropriate to be used as an earthquake simulator.

Singularity Analysis of a Plane-Symmetry 3-RPS Parallel Robot Based on Translational/Rotational Jacobian Matrices

Firstly, 3-DOF parallel robots were classified into different types from the view of moving form. A new method of analyzing the singularity of 3-DOF parallel robots was introduced, which is based on translational Jacobian matrix and rotational Jacobian matrix. The singularity of parallel robots with pure translational form and pure rotational form was introduced summarily. Secondly, the process of solving the plane-symmetry 3-RPS parallel robot with combined moving forms was focused on, through which translational Jacobian matrix and rotational Jacobian matrix were adopted. Finally, the solving results were compared with the axis-symmetry 3-RPS parallel robot, which showed more general singularity can be solved through the new method.

Decoupling control for spatial six-degree-of-freedom electro-hydraulic parallel robot

This paper presents a decoupling controller equipped with cross-coupling pre-compensation for an electro-hydraulic parallel robot, in order to weaken system dynamic coupling effects usually ignored on the design of advanced controllers and improve system control performance. The mathematical model of the electro-hydraulic parallel robot is built using the Kane method and a hydromechanics approach, and the kinematical model is established with a closed-form solution and the Newton-Raphson method. The feedback linearization theory is applied to reduce coupling effects stemmed from system dynamics of the parallel robot via incorporating force-velocity control with cross-coupling pre-compensations. The control performance involving stability, accuracy, and robustness of the proposed controller for spatial 6-DOF parallel robot is analyzed in theory and experiment. The experimental results illustrate that the proposed controller can highly improve the control performance by weakening system dynamic coupling effects of the electro-hydraulic parallel robot, especially for trajectory tracking performance.

Configuration Design and Kinematic Analysis on Some New 2R1T 3-DOF Parallel Robots

Based on the screw theory,the paper presents a systematic method for structural synthesis of the two rotations and one translation parallel robot.According to the reciprocal product between kinetic screw and constrainted screw in screw theory.This method firstly creats possible branch structures and then generates diferent models of mechanism.By this method,the paper carries on the structural synthesis of the two rotations and one translation parallel robot,and also lists some of the mechanisms including a few new ones. Analyzsis solution of direct and inverse position.The dynamic simulation was conducted using the software of Adams.

Fuzzy Sliding Mode Control for 6-DOF Parallel Robot Based on Support Vector Machines

To realize the trajectory tracking control for six degrees of freedom parallel robot, a fuzzy sliding mode control strategy based on support vector machines is presented. Sliding mode control algorithm has complete adaptability to system disturbance and siring in sliding mode, which is used to automatically track the uncertainty of system parameters and external disturbance. Fuzzy algorithm is applied to improve the sliding mode control performance. Fuzzy support vector machines have strong treatment of non-linear signal and generalization ability, which is used to reduce the chattering in sliding mode control. The parameters of fuzzy support machines controller are optimized by hybrid learning algorithm, which combines least square algorithm with improved genetic algorithm, to get the optimal control performance for the object. The simulation results demonstrated that the control strategy designed gets tracking effect with high precision and speed, as well as reduces chattering of control under the condition of model error and external disturbance.

Simulation of 6-DOF Parallel Robot for Coupling Compensation Method

Simulation of 6-DOF Parallel Robot for Coupling Compensation Method

Fuzzy Support Vector Machines Control for 6-DOF Parallel Robot

In order to realize the trajectory tracking control of six degrees of freedom parallel robot, the dynamics equation of six degrees of freedom parallel robot was established. The parallel robot has obvious nonlinear, uncertainty characteristics and external disturbance, so the sliding mode variable structure theory was introduced into the system control. A fuzzy support vector machines control strategy based on sliding mode control was designed to reduce the oscillation of the sliding mode control. Parameters of fuzzy support vector machines controller were optimized by hybrid learning algorithm, which combines least square algorithm with improved genetic algorithm, to get the optimal control performance for the controlled object. The controller designed consists of a fuzzy sliding mode controller and a fuzzy support vector machines controller, and the compensation controller is selected by comparing switching function with the thickness of boundary layer. Simulation results show that under the condition of model error and external disturbance, the control strategy designed gets tracking effect with high precision and speed.

Coupling Compensation of 6-DOF Parallel Robot Based on Screw Theory

Coupling Compensation of 6-DOF Parallel Robot Based on Screw Theory