This paper presents investigations into the applications and performance of positive and negative input shapers in command shaping techniques for the vibration control of a flexible robot manipulator. A constrained planar single-link flexible manipulator is considered and the dynamic model of the system is derived using the finite element method. An unshaped bang-bang torque input is used to determine the characteristic parameters of the system for design and evaluation of the input shaping control techniques. The positive and specified amplitude negative input shapers are designed based on the properties of the system. Simulation results of the response of the manipulator to the shaped inputs are presented in the time and frequency domains. Performances of the shapers are examined in terms of level of vibration reduction, time response specifications and robustness to parameters uncertainty. The effects of derivative order of the input shaper on the performance of the system are investigated. Finally, a comparative assessment of the impact amplitude polarities of the input shapers on the system performance is presented and discussed.
Due to time-varying effects in electro-hydraulic actuator (EHA) system parameters, a selftuning control algorithm using pole placement and recursive identification is presented. A discrete-time model is developed using system identification method to represent the EHA system and residual analysis is used for model validation. A recursive least square (RLS) method with covariance resetting technique is proposed to estimate parameters of the discrete-time model. The results show the proposed control algorithm can adapt the changes occur in model parameters compared with the fixed controller.
This paper proposes an improved robust position controller for the electro-hydraulic actuator system using the varying boundary layered sliding mode control scheme. The proposed scheme has the ability to improve the position tracking performance of the actuator in the presence of friction and internal leakage. The former is represented using the LuGre model while later is modelled as a turbulent flow. To evaluate the effectiveness of the proposed method, MATLAB simulations are carried out under friction and leakage effects. Its performance is compared with the conventional PID and fuzzy PID (FPID) methods. Finally, an experimental rig that comprises of a single-rod and double acting hydraulic cylinder is set up to validate the proposed idea. The software development is carried out in the DSpace 1104 environment using a TMS320F240 digital signal processor. The superiority of the proposed method over the PID and FPID in terms of tracking position is highlighted by simulation and experimental results.
This paper presents a new robust control scheme for a class of electro-hydraulic actuator using dynamic sliding mode control associated with nonlinear disturbance observer. Switching-gain of the sliding mode is designed to be adaptable on the estimated disturbance. A switching-gain adaptation mechanism is proposed to obtain as small as possible switching-gain to minimize chattering effect. The scheme is developed to guarantee the tracking precision of the system with robust and smooth control actions in the existence of uncertainties and the changes of external disturbance. Capability of the proposed scheme is enhanced by varying boundary layers algorithm to assist the scheme to return to its ability in a larger change of external disturbance. Capability and effectiveness of the proposed scheme are validated through experiment, where the results indicate that the proposed scheme ensures the tracking precision of the system with robust and smooth control actions in a large change of external load disturbance. Moreover, smooth control actions that are produced by the proposed control scheme offer a significant efficiency of energy in the control of electro-hydraulic actuator systems.
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