scholarly journals Cable Force-Balancing Distribution of the Cable-Driven Parallel Mechanism for Actuator Saturation Avoidance

2017 ◽  
Author(s):  
Youngsu Cho ◽  
Joono Cheong ◽  
Byung-Ju Yi ◽  
Wheekuk Kim
Keyword(s):  
Parallel Mechanism ◽  
Actuator Saturation ◽  
Cable Force

Projection-Based Control of Parallel Mechanisms

2011 ◽  
Vol 6 (3) ◽  
Author(s):  
Farhad Aghili
Keyword(s):  
Mechanical System ◽  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Actuator Saturation ◽  
Parallel Manipulators ◽  
Parallel Mechanisms ◽  
Dynamics Model ◽  
Minimal Order ◽  
Control Approach ◽  
System Changes

The unifying idea for most model-based control approaches for parallel mechanism is to derive a minimal-order dynamics model of the system and then design the corresponding controller. The problem with such a control approach is that the controller needs to change its structure whenever the mechanical system changes its number of degrees-of-freedom. This paper presents a projection-based control scheme for parallel mechanism that works whether the system is overactuated or not; it does not require derivation of the minimal-order dynamics model. Since the dimension of the projection matrix is fixed, the projection-based controller does not need to change its structure whenever the mechanical system changes its number of degrees-of-freedom. The controller also allows to specify lower and upper bounds on the actuator forces/torques, making it suitable not only for the control of parallel manipulators with limited force/torque capability of the actuators but also for backlash-free control of parallel manipulators as well as for control of tendon driven parallel manipulators. The stability of the projection-based controllers is rigourously proved, while the condition for the controllability of parallel manipulators is also derived in detail. Finally, experimental results obtained from a simple parallel mechanism, which changes its degrees-of-freedom, are appended. The results also demonstrate that the maximum actuator torque can be reduced by 20% if the actuator saturation is taken into account by the controller.

A Spatial Spring-Loaded Cable-Loop-Driven Parallel Mechanism

2011 ◽  
Author(s):  
Hanwei Liu ◽  
Cle´ment Gosselin ◽  
Thierry Laliberte´
Keyword(s):  
Parallel Mechanism ◽  
Degrees Of Freedom ◽  
Superposition Principle ◽  
Equilibrium Equations ◽  
Square Roots ◽  
Workspace Analysis ◽  
The Matrix ◽  
Cable Force ◽  
External Forces ◽  
Boundary Equations

A novel architecture of spatial spring-loaded cable-loop-driven parallel mechanism is introduced in this paper. In this mechanism, cable-spool actuating systems and actuation redundancy are avoided. By attaching springs to the cable loops, three degrees of freedom for spatial displacement can be controlled using only three actuators. This paper presents the inverse kinematics, the static equilibrium equations and the workspace analysis. Because all these equations are obtained based on the cable segment lengths, many square roots appear in the equations. The boundary equations for different arrangements, i.e., preload, non-zero stiffness and external forces, are obtained separately in order to simplify the analysis. The boundary equations of each cable force for any situation can be obtained by combining the equations based on the matrix superposition principle. It is verified that the mechanism has a significantly large workspace within which the cables and the springs can be maintained in tension compared to a standard mechanism actuated with three motors.

Inverse Control of Cable-driven Parallel Mechanism Using Type-2 Fuzzy Neural Network

2010 ◽  
Vol 36 (3) ◽  
pp. 459-464 ◽  
Author(s):  
Cheng-Dong LI ◽  
Jian-Qiang YI ◽  
Yi YU ◽  
Dong-Bin ZHAO
Keyword(s):  
Neural Network ◽  
Parallel Mechanism ◽  
Fuzzy Neural Network ◽  
Inverse Control ◽  
Fuzzy Neural

Statics Analysis on Planar Moving Parallel Mechanism Based on Boundary Element Method

ROBOT ◽  
2010 ◽  
Vol 32 (3) ◽  
pp. 384-389 ◽  
Author(s):  
Yumei HUANG ◽  
Xuzhao HAN ◽  
Feng GAO ◽  
Chun CHEN ◽  
Xingang YANG
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Parallel Mechanism ◽  
Element Method

Enhanced Composite Nonlinear Control Technique using Adaptive Control for Nonlinear Delayed Systems

2020 ◽  
Vol 13 (3) ◽  
pp. 396-404
Author(s):  
Sonal Singh ◽  
Shubhi Purwar
Keyword(s):  
Adaptive Control ◽  
Actuator Saturation ◽  
Input Saturation ◽  
Chemical Reactor ◽  
Control Technique ◽  
Control Law ◽  
Nonlinear Feedback ◽  
Composite Nonlinear Feedback ◽  
Delayed Systems ◽  
Analysis Of Stability

Background and Introduction: The proposed control law is designed to provide fast reference tracking with minimal overshoot and to minimize the effect of unknown nonlinearities and external disturbances. Methods: In this work, an enhanced composite nonlinear feedback technique using adaptive control is developed for a nonlinear delayed system subjected to input saturation and exogenous disturbances. It ensures that the plant response is not affected by adverse effect of actuator saturation, unknown time delay and unknown nonlinearities/ disturbances. The analysis of stability is done by Lyapunov-Krasovskii functional that guarantees asymptotical stability. Results: The proposed control law is validated by its implementation on exothermic chemical reactor. MATLAB figures are provided to compare the results. Conclusion: The simulation results of the proposed controller are compared with the conventional composite nonlinear feedback control which illustrates the efficiency of the proposed controller.

scholarly journals Type Synthesis of 1T2R Parallel Mechanisms Using Structure Coupling-Reducing Method

2019 ◽  
Vol 32 (1) ◽  
Author(s):  
Haitao Liu ◽  
Ke Xu ◽  
Huiping Shen ◽  
Xianlei Shan ◽  
Tingli Yang
Keyword(s):  
Explicit Form ◽  
Parallel Mechanism ◽  
Analytic Solutions ◽  
Forward Kinematics ◽  
Parallel Mechanisms ◽  
Type Synthesis ◽  
Real Time Control ◽  
Time Control ◽  
Topological Characteristics ◽  
Zero Coupling

Abstract Direct kinematics with analytic solutions is critical to the real-time control of parallel mechanisms. Therefore, the type synthesis of a mechanism having explicit form of forward kinematics has become a topic of interest. Based on this purpose, this paper deals with the type synthesis of 1T2R parallel mechanisms by investigating the topological structure coupling-reducing of the 3UPS&UP parallel mechanism. With the aid of the theory of mechanism topology, the analysis of the topological characteristics of the 3UPS&UP parallel mechanism is presented, which shows that there are highly coupled motions and constraints amongst the limbs of the mechanism. Three methods for structure coupling-reducing of the 3UPS&UP parallel mechanism are proposed, resulting in eight new types of 1T2R parallel mechanisms with one or zero coupling degree. One obtained parallel mechanism is taken as an example to demonstrate that a mechanism with zero coupling degree has an explicit form for forward kinematics. The process of type synthesis is in the order of permutation and combination; therefore, there are no omissions. This method is also applicable to other configurations, and novel topological structures having simple forward kinematics can be obtained from an original mechanism via this method.

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