Sliding Mode Set Point Control of a Six-DOF Cable-Suspended Parallel Robot With Tension Constraints and Uncertain Disturbances

2018 ◽  
Author(s):  
Ping Ren ◽  
Yunlong Sun
Keyword(s):  
Sliding Mode ◽  
Sufficient Conditions ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Set Point ◽  
Uncertain Disturbances ◽  
Point Motion ◽  
Six Dof ◽  
Six Degree Of Freedom ◽  
The Relationship

This paper presents the design of a robust sliding mode controller for a six-degree-of-freedom cable-suspended parallel robot under uncertain disturbances. The control of cable-suspended parallel robots is quite challenging due to the unidirectional constraint of cable tensions. With the aid of interval analysis, a set of algebraic inequalities is obtained to establish the relationship between the cables’ tension constraints and the controller parameters. The sufficient conditions of the controller parameters satisfying the constraints are obtained for the set point motion within the robot’s static workspace. Numerical simulations are presented to verify the effectiveness of the proposed approach.

Sliding Mode Set-Point Control of a Three-DOF Cable-Suspended Parallel Robot With Uncertain Mass and Disturbances

2019 ◽  
Author(s):  
Ping Ren ◽  
Xu Sheng
Keyword(s):  
Sliding Mode ◽  
Sufficient Conditions ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Parallel Mechanisms ◽  
Set Point ◽  
Point Motion ◽  
Actuation Scheme ◽  
Three Degree Of Freedom ◽  
The Relationship

Abstract Cable-Suspended Parallel Robots (CSPRs) utilize winches and cables as the actuation scheme instead of rigid links, which renders them advantages of both parallel mechanisms and cable mechanisms. In this paper, a robust sliding mode controller was designed for a three-degree-of-freedom CSPR with uncertain end-effector mass and external disturbances. To control the motions of CSPRs is usually challenging due to the unidirectional constraints of cable tensions. Based on interval analysis, a set of analytical inequalities is obtained which establish the relationship between the cables’ tension constraints and the controller parameters. The sufficient conditions of the controller parameters satisfying the constraints are obtained for the set-point motion subject to uncertainties. Numerical simulations are presented to verify the effectiveness of the proposed approach.

scholarly journals Potential Energy Distribution of Redundant Cable-Driven Robot Applied to Compliant Grippers: Method and Computational Analysis

Sensors ◽  
2019 ◽  
Vol 19 (15) ◽  
pp. 3403 ◽  
Author(s):  
Rodriguez-Barroso ◽  
Saltaren ◽  
Portilla ◽  
Cely ◽  
Yakrangi
Keyword(s):  
Energy Distribution ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Potential Energy Distribution ◽  
End Effector ◽  
Tension Distribution ◽  
Multibody Dynamic ◽  
Compliant Actuators ◽  
Dynamic Software ◽  
The Relationship

Cable-driven parallel robots with a redundant configuration have infinite solutions for their cable tension distribution to provide a specific wrench to the end-effector. Redundancy is commonly used to increase the workspace and stiffness or to achieve secondary objectives like energetic minimization or additional movements. This article presents a method based on energy distribution to handle the redundancy of cable-driven parallel robots. This method allows the deformation and tension of each link to be related to the total energy available in the parallel robot. The study of energy distribution expression allows deformation, tension, and position to be combined. It also defines the range of tension and deformation that cables can achieve without altering the wrench exerted on the end-effector. This range is used with a passive reconfigurable end-effector to control the position of two grippers attached to some cables which act as compliant actuators. The relationship between the actuators’ energy and their corresponding gripper positions is also provided. In this way, energy measurement from the actuators allows the grasping state to be sensed. The results are validated using multibody dynamic software.

scholarly journals Motion Reliability Analysis of the Delta Parallel Robot considering Mechanism Errors

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Yu Li ◽  
Deyong Shang ◽  
Xun Fan ◽  
Yue Liu
Keyword(s):  
Reliability Analysis ◽  
Structural Parameters ◽  
Kinematic Model ◽  
Vertical Direction ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Joint Clearance ◽  
Spherical Joint ◽  
Key Factor ◽  
The Relationship

Delta parallel robots are widely used in assembly detection, packaging sorting, precision positioning, and other fields. With the widespread use of robots, people have increasing requirements for motion accuracy and reliability. This paper considers the influence of various mechanism errors on the motion accuracy and analyzes the motion reliability of the mechanism. Firstly, we establish a kinematic model of the robot and obtain the relationship between the position of the end effector and the structural parameters based on the improved D–H transform rule. Secondly, an error model considering the dimension error, the error of revolute joint clearance, driving error, and the error of spherical joint clearance is established. Finally, taking an actual robot as an example, the comprehensive influence of mechanism errors on motion accuracy and reliability in different directions is quantitatively analyzed. It is shown that the driving error is a key factor determining the motion accuracy and reliability. The influence of mechanism errors on motion reliability is different in different directions. The influence of mechanism errors on reliability is small in the vertical direction, while it is great in the horizontal direction. Therefore, we should strictly control the mechanism errors, especially the driving angle, to ensure the motion accuracy and reliability. This research has significance for error compensation, motion reliability analysis, and reliability prediction in robots, and the conclusions can be extended to similar mechanisms.

scholarly journals Backstepping Sliding Mode Robust Control for a Wire-Driven Parallel Robot Based on a Nonlinear Disturbance Observer

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Yuqi Wang ◽  
Qi Lin ◽  
Lei Zhou ◽  
Xinxin Shi ◽  
Lei Wang
Keyword(s):  
Robust Control ◽  
Disturbance Observer ◽  
Control Method ◽  
Sliding Mode ◽  
Design Method ◽  
Parallel Robot ◽  
Parallel Robots ◽  
End Effector ◽  
Nonlinear Disturbance Observer ◽  
Nonlinear Disturbance

Based on a nonlinear disturbance observer, a backstepping sliding mode robust control is proposed for a wire-driven parallel robot (WDPR) system used in the wind tunnel test to dominate the motion of the end effector. The control method combines both the merits of backstepping control and sliding mode robust control. The WDPR is subject to different types of disturbances, and these disturbances will affect the motion precision of the end effector. To overcome these problems, a nonlinear disturbance observer (NDO) is designed to reject such disturbances. In this study, the design method of the nonlinear disturbance observer does not require the reliable dynamic model of the WDPR. Moreover, the design method can be used not only in the WDPR but also in other parallel robots. Then, a backstepping design method is adopted and a sliding mode term is introduced to construct a desired controller, and the disturbances are compensated in the controller to reduce the switching gain and guarantee the robustness. For the sake of verifying the stabilization of the closed-loop system, the Lyapunov function is constructed to analyze the stabilization of the system. Finally, the feasibility and validity of the proposed control scheme are proved through both simulation and experimental results.

scholarly journals Parallel robot with fuzzy neural network sliding mode control

2018 ◽  
Vol 10 (10) ◽  
pp. 168781401880126 ◽  
Author(s):  
Jiangmin Xu ◽  
Qi Wang ◽  
Qing Lin
Keyword(s):  
Neural Network ◽  
Control Theory ◽  
Sliding Mode Control ◽  
Fuzzy Neural Network ◽  
Sliding Mode ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Adaptive Sliding Mode Control ◽  
Mode Control ◽  
Fuzzy Neural

With the advancement in research on parallel robots, control theory is increasingly applied in the field of robotics. Owing to its robustness, sliding mode variable structure control is extensively used in parallel robots. This article presents an adaptive sliding mode control method for nonlinear systems. A parallel robot control model with adaptive fuzzy sliding mode control was designed based on a fuzzy neural network control theory, and simulation results demonstrate its effectiveness of the method.

Stiffness Analysis for a Novel Parallel-Robot Based High-Precision Flexible Assembly Fixture

2007 ◽  
Vol 364-366 ◽  
pp. 327-332 ◽  
Author(s):  
Hong Jian Yu ◽  
Bing Li ◽  
Xiao Jun Yang ◽  
Ying Hu ◽  
Hong Hu
Keyword(s):  
Stiffness Matrix ◽  
Screw Theory ◽  
System Modeling ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Stiffness Analysis ◽  
Flexible Assembly ◽  
Global Stiffness Matrix ◽  
The Relationship ◽  
Assembly Fixture

In this paper, a novel parallel mechanism (3-RRRS/UPR) used in flexible fixture with configuration composed of two parallel robots (2-RR and 3-RRRS/ UPR) is presented. First, system modeling including the mobility study is conducted. Then a novel methodology is proposed that makes use of screw theory to analyze the deformation and stiffness of the mechanism: firstly we identified the existence of the deformation of the subchain, in terms of the relationship between the effective screw and deformation screw; then we took the deformation as an infinitesimal motion of the mechanism, and the stiffness matrix corresponding to the deformation can be deduced. Finally the global stiffness matrix of the whole mechanism is modeled by assembling different stiffness characters based on the presented methodology.

Modified PID like fuzzy servo control applied to smart actuator based miniature Parallel Robot

2021 ◽  
pp. 1-21
Author(s):  
R. Ranjith Pillai ◽  
Ganesan Murali
Keyword(s):  
Shape Memory ◽  
Trajectory Tracking ◽  
Fuzzy Controller ◽  
Sliding Mode ◽  
Parallel Robot ◽  
Electrical Circuit ◽  
Parallel Robots ◽  
Smart Actuator ◽  
Set Up ◽  
General Response

Miniature flexible parallel robots, popularly used for micro positioning application demands the use of non conventional actuators. Shape memory alloys (SMA) are popular smart actuators because of its light weight, integration compatibility, ease of actuation and high power density. Inclusion of shape memory alloy actuators to the parallel robot brings in control challenges due to its nonlinearity, coupling effects and cocontraction of antagonistic pair of actuators in the mechanism in order to achieve bi directional motion. In this paper, a PID like fuzzy controller is designed and applied to a nonlinear SMA spring actuator connected to a symmetric 2 DOF miniature parallel robot. The fuzzy rules are designed from the general response plot and modified to be applied to a parallel mechanism which involves cocontraction of antagonistic actuators. The paper has also presented the control and electrical circuit design used in the experimental set up. The fuzzy control is implemented in the hardware controller with model based position feedback and tested for the trajectory tracking characteristics of the end effector with disturbances. Experimental results are presented with quantitative analysis to show the effectiveness of the proposed controller in handling nonlinearities and disturbances compared to the conventional PID control and nonlinear Sliding mode control (NSMC). The test results has demonstrated the superior nature of proposed control over other controllers in the trajectory tracking with disturbances and also linearizing the hysteresis of controlled system.

Improving the performance of parallel robots by applying distinct hybrid control techniques

Robotica ◽  
2021 ◽  
pp. 1-25
Author(s):  
André G. Coutinho ◽  
Tarcisio A. Hess-Coelho
Keyword(s):  
Sliding Mode Control ◽  
Hybrid Control ◽  
Sliding Mode ◽  
Control Strategies ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Control Laws ◽  
Control Techniques ◽  
Mode Control ◽  
And Control

Abstract During the last two decades, parallel robots have become more ubiquitous, employed in a great variety of sectors, from food to aerospace industries. In fact, they are much more efficient than their serial counterparts in terms of performing fast motions and consuming less energy. However, due to their mechanical complexity, they present a highly complex non-linear dynamics, which makes the modelling and control tasks difficult. Aiming to improve the performance and robustness of the control laws already used to control this type of mechanisms, this paper proposes two hybrid control techniques. The first hybrid control is derived from the combination of a pure PD control with a modified Sliding Mode control. The second hybrid control, in its turn, combines a pure Computed Torque with the altered Sliding Mode control. The proposed modifications in the Sliding Mode control aim to achieve a considerable reduction of the tracking errors and chattering. A stability analysis of the proposed control techniques and an experimental validation are carried out, comparing the performance of the pure and hybrid control laws in a 5R parallel mechanism. Moreover, simulations are also conducted to evaluate the behaviour of a 3-dof spatial parallel robot, when performing a 3D-path. Analysing the simulations and the experimental results, it is possible to observe a significant reduction of the path tracking and steady-state errors in both hybrid control strategies.

scholarly journals Finite-Time Dynamic Tracking Control of Parallel Robots with Uncertainties and Input Saturation

Sensors ◽  
2021 ◽  
Vol 21 (9) ◽  
pp. 2996
Author(s):  
Mengyang Ye ◽  
Guoqin Gao ◽  
Junwen Zhong ◽  
Qiuyue Qin
Keyword(s):  
Sliding Mode Control ◽  
Finite Time ◽  
Sliding Mode ◽  
Input Saturation ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Auxiliary System ◽  
Terminal Sliding Mode ◽  
Time Dynamic ◽  
Mode Control

This paper considers the finite-time dynamic tracking control for parallel robots with uncertainties and input saturation via a finite-time nonsingular terminal sliding mode control scheme. A disturbance observer is designed to estimate the lumped disturbance in the dynamic model of the parallel robot, including modeling errors, friction and external disturbance. By introducing the fractional exponential powers into the existing asymptotic convergent auxiliary system, a novel finite-time convergent auxiliary system is constructed to compensate for input saturation. The finite-time nonsingular terminal sliding mode control is proposed based on the disturbance estimation and the state of the novel auxiliary system, so that the convergence performance, control accuracy and robustness are improved. Due to the estimation and compensation for the lumped disturbance, the inherent chattering characteristic of sliding mode control can be alleviated by reducing the control gain. The finite-time stability of the closed-loop system is proved with Lyapunov theory. Finally, simulation and experimental research on the dynamic control of a conveying parallel robot are carried out to verify the effectiveness of the proposed method.

scholarly journals Cable-Driven Parallel Robot with Reconfigurable End Effector Controlled with a Compliant Actuator

Sensors ◽  
2018 ◽  
Vol 18 (9) ◽  
pp. 2765 ◽  
Author(s):  
Alejandro Rodriguez-Barroso ◽  
Roque Saltaren ◽  
Gerardo A. Portilla ◽  
Juan S. Cely ◽  
Marco Carpio
Keyword(s):  
Degrees Of Freedom ◽  
Parallel Robot ◽  
Parallel Robots ◽  
Degree Of Freedom ◽  
Elastic Model ◽  
Dynamic Simulations ◽  
End Effector ◽  
High Tension ◽  
Compliant Actuator ◽  
The Relationship

Redundancy in cable-driven parallel robots provides additional degrees of freedom that can be used to achieve different objectives. In this robot, this degree of freedom is used to act on a reconfigurable end effector with one degree of freedom. A compliant actuator actuated by one motor exerts force on both bodies of the platform. Due to the high tension that appears in this cable in comparison with the rest of the cables, an elastic model was developed for solving the kinestostatic and wrench analysis. A linear sensor was used in one branch of this cable mechanism to provide the needed intermediate values. The position of one link of the platform was fixed in order to focus this analysis on the relationship between the cables and the platform’s internal movement. Position values of the reconfigurable end effector were calculated and measured as well as the tension at different regions of the compliant actuator. The theoretical values were compared with dynamic simulations and real prototype results.

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