Control Of Two-link Flexible Manipulator Research Articles

Sliding mode control of Two-link Flexible Manipulator for reduced vibration in the presence of unmatched uncertainty and time-varying external disturbance

Sliding mode control of Two-link Flexible Manipulator for reduced vibration in the presence of unmatched uncertainty and time-varying external disturbance

Sampled-data extended state observer-based backstepping control of two-link flexible manipulator

Currently, space robots such as planetary robots and flexible-link manipulators (FLMs) are finding specific applications to reduce the cost of launching. However, the structural flexible nature of their arms and joints leads to errors in tip positioning owing to tip deflection. The internal model uncertainties and disturbance are the key challenges in the development of control strategies for tip-tracking of FLMs. To deal with these challenges, we design a tip-tracking controller for a two-link flexible manipulator (TLFM) by developing a sampled-data extended state observer (SD-ESO). It is designed to reconstruct uncertain parameters for accurate tip-tracking control of a TLFM. Finally, a backstepping (BS) controller is designed to attenuate the estimation error and other bounded disturbances. Convergence and stability of the proposed control system are investigated by using Lyapunov theory. The benefits (control performance and robustness) of the proposed SD-ESO-based BS controller are compared with other similar approaches by pursuing both simulation and experimental studies. It is observed from the results obtained that SD-ESO-based BS Controller effectively compensates the deviation in tip-tracking performance of TLFM due to non-minimum phase behavior and model uncertainties with an improved transient response.

Back-stepping control of two-link flexible manipulator based on an extended state observer

In this paper, we consider trajectory tracking control of a two-link flexible manipulator model in space. Two variables of joint angle and elastic deformation are partly decoupled by a nonlinear decoupling feedback control method. An extended state observer is introduced to estimate nonlinear terms of the two-link flexible manipulator system. Based on a back-stepping method, a nonlinear controller is designed for the flexible manipulator system. Finally, some simulation results are given to demonstrate the effectiveness of the developed techniques in this paper.

System Identification and LMI Based Robust PID Control of a Two-Link Flexible Manipulator

This paper presents investigations into the development of a linear matrix inequalities (LMI) based robust PID control of a nonlinear Two-Link Flexible Manipulator (TLFM) incorporating payload. A set of linear models of a TLFM is obtained by using system identification method in which the linear model represents the operating ranges of the dynamic system. Thus, the LMI constraints permit to robustly guarantee a certain perturbation rejection level and a region of pole location. To study the effectiveness of the controller, initially a PID control is developed for TLFM with varying payloads. The performances of the controllers are assessed in terms of the input tracking controller capability of the system as compared to the response with PID control. Moreover, the robustness of the LMI based robust PID control schemes is discussed. Finally, a comparative assessment of the control strategies is presented.

Dynamics and Terminal Sliding Mode Control of Two-Link Flexible Manipulators with Noncollocated Feedback

Abstract This paper presents a dynamic model and a class of terminal sliding mode control (TSMC) for two-link flexible manipulators with noncollocated feedback. With the assumed mode method, the closed form dynamic model of two-link flexible manipulators is derived by using the Lagrangian approach. The TSMC technique is used to design the controller. The mode coordinate vectors of flexible manipulators are computed by noncollocated feedback. The proposed TSMC guarantees that the output tracking error converges to zero in finite time under external disturbance. Numerical simulation results of two-link flexible manipulators are provided to verify the effectiveness of the proposed control scheme.

Hybrid Control Scheme for Robust Tracking of Two-Link Flexible Manipulator

The hybrid control scheme is proposed to stabilize the vibration of a two-link flexible manipulator while the robustness of Variable Structure Control (VSC) developed for rigid manipulators is maintained for controlling the joint angles. The VSC law alone, which is designed to accomplish only the asymptotic decoupled joint angle trajectory tracking, does not guarantee the stability of the flexible mode dynamics of the links. In order to actively suppress the flexible link vibrations, hybrid trajectories for the VSC are generated using the virtual control force concept, so that robust tracking control of the flexible-link manipulator can also be accomplished. Simulation results confirm that the proposed hybrid control scheme can achieve more robust tracking control of two-link flexible manipulator than the conventional control scheme in the presence of payload uncertainty.

Robust Control of Two-Link Flexible Manipulators Using the μ-Synthesis Technique

Two-link robot manipulators are commonly used in industrial sectors such as manufacturing. Some manipulators are often bulky and their power consumption is relatively high. Others, such as the arm on the space shuttle, are driven slowly to prevent the onset of flexible oscillations. The efficiency of these manipulators can be improved by reducing the weight of some of these arms and/or increasing the speed of others. These modifications complicate the dynamic behavior of the system due to the possible onset of low frequency oscillations. This article addresses the issue of modeling and end-point robust control of two-link flexible manipulators using the μ-synthesis technique. The Timoshenko beam theory along with the assumed modes method are used to derive reference equations of motion for the flexible manipulator. Discrepancies between the control design model and the actual dynamics of the manipulator are attributed to neglected nonlinearities such as cross-coupling, which should be included in the controller design. A linear estimation of these errors will be identified and used in the control design to compensate for the unmodeled dynamics of the flexible arm and parameter uncertainties. The μ-synthesis control design techniques are then employed to synthesize controllers for the two-link flexible robot manipulator.

192 Modeling and quasi-static hybrid position/force control of two-link flexible manipulators

192 Modeling and quasi-static hybrid position/force control of two-link flexible manipulators

Modeling and Quasi-Static Hybrid Position/Force Control of Two-link Flexible Manipulators

In this paper, a method is proposed whereby both contact force exerted by a flexible manipulator and position of end-effector while in contact with a surface are controlled. We derive dynamic equations of joint angles, vibration of the flexible links, and contact force by means of Hamilton's principle. On the basis of some assumptions we derive the quasi-static equations and design the hybrid position/force controller of the flexible manipulator. A set of experiments for the hybrid control of the flexible manipulator using a force sensor has been carried out. Several experimental results are shown