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In this paper, an improved feed-forward inverse control scheme is proposed for transient waveform replication (TWR) on an electro-hydraulic shaking table (EHST). TWR is to determine whether a test article can remain operational and retain its structural integrity when subjected to a specific shock and vibration environment. Feed-forward inverse transfer function compensation is a useful technique to improve the tracking accuracy of the TWR on the EHST system due to their inherent hydraulic dynamics. Whenever a feed-forward inverse transfer function is employed, it is critical to design the identification accuracy of the inverse transfer function. A combined control strategy, which combines a feed-forward inverse transfer function compensation approach with a simple internal model control (IMC) and a real-time feedback controller, is proposed to minimize the effect of the system uncertainty and modeling error, and further to improve the tracking accuracy of the TWR. Thus, the proposed control strategy combines the merits of feed-forward inverse transfer function compensation and IMC. The procedure of the proposed control strategy is programmed in MATLAB/Simulink, and then is compiled to a real-time PC with Microsoft Visual Studio.NET for implementation. Simulation and experimental results demonstrated the viability of the proposed combined control strategy.

The Kane-Huston is adopted in this paper to build the topological structure for the working device of hydraulic excavator. And the virtual prototyping model of the working device is built by the virtual prototype analysis software. Through analysis of the mechanical properties of working device on real working condition and comparing the inverse dynamics gotten by the Kane-Huston with that gotten by the virtual prototype model in software, the correctness of the dynamic equations from the Kane-Huston is verified. Finally, fuzzy control method is used for the optimization of bucket tip trajectory and it has good control effect in the software simulation environment.

A high-gain observer based sliding mode force control system for the single-rod servo actuator is presented in this paper. In order to track the desired force, full states for feedback are needed. Since only the output force is measured, a high-gain observer with easy implementation and calibration is designed for the estimation of the unavailable states. Then the sliding mode controller is proposed and a continuously varying function instead of the traditional sign function is used to constitute the switching term of the control input which takes the distance of the system states from the sliding surface into account. So the chattering phenomena are eliminated. The stability of the closed-loop force control system is analyzed by the singular perturbation method and simulations show the effectiveness of the proposed force control method for the single-rod electrohydraulic servo actuator. INDEX TERMS High-gain observer, sliding mode control, chattering-free, servo actuator, force control.

Abstract-Based on the characteristics of wheeled, tracked and legged movements, a variable parallelogram tracked mobile robot(VPTMR) is proposed and developed to enhance its adaptability and stability in the complex environment. This VPTMR robot consists of two variable parallelogram structures, which are composed of one main tracked arm, two lower tracked arms and a chasis. The variable parallelogram structure is actuated by a DC motor. And another DC motor actuates the track rotation, which enables VPTMR robot to move in wheeled, tracked and legged mode that makes the robot to adapt to all rugged environments. The prototype(VPTMR) is developed to verify its performance on environmental adaptability, obstacle crossing ability and stability.