Dang Xuan Ba

An Integrated Intelligent Nonlinear Control Method for a Pneumatic Artificial Muscle

This paper proposes an advanced position-tracking control approach, referred to as an integrated intelligent nonlinear controller, for a pneumatic artificial muscle (PAM) system. Due to the existence of uncertain, unknown, and nonlinear terms in the system dynamics, it is difficult to derive an exact mathematical model with robust control performance. To overcome this problem, the main contributions of this paper are as follows. To actively represent the behavior of the PAM system using a grey-box model, neural networks are employed as equivalent internal dynamics of the system model and optimized online by a Lyapunov-based method. To realize the control objective by effectively compensating for the estimation error, an advanced robust controller is developed from the integration of the designed networks, and improvement of the sliding mode and backstepping techniques. The convergences of both the developed model and the closed-loop control system are guaranteed by Lyapunov functions. As a result, the overall control approach is capable of ensuring the systems performance with fast response, high accuracy, and robustness. Real-time experiments are carried out in a PAM system under different conditions to validate the effectiveness of the proposed method.

Time delay control of a pump-controlled electro-hydraulic actuator

This paper presents an accurate position control for a pump-controlled electro-hydraulic actuator (EHA) using time-delay estimation (TDE). The TDE technique is used to estimate nonlinear terms of EHA, which is a third order nonlinear system. The measured signal of linear encoder, and pressure of the EHA are used to implement the TDE technique. The effectiveness of the proposed controller is verified through experiment using an EHA test bench. The proposed controller shows better tracking performance compared with a PID controller.

Adaptive output feedback control of an electro-hydraulic system

In this paper, an advanced nonlinear method - adaptive output feedback (AOF) controller - is presented for position tracking control problem of a pump-controlled Electro Hydraulic System (EHS). The system uncertainties including uncertain parameters and external disturbances are covered by an adaptive law while all nonlinearities are compensated by a modified output-feedback techniques. For supplying necessary information to the controller, mathematical model of the EHS is derived in which a view of certain, an uncertain and nonlinear terms is clearly represented. The control input is then synthesized by incorporating the adaptive law with the control algorithm based on Lyapunov derivatives. Finally, effectiveness of the proposed controller is successfully verified through simulation and experimental results of different testing conditions.

An optimal controller for an electro-hydraulic system

In this paper, an advanced controller is presented for position tracking control and minimizing control energy of an electro-hydraulic system. An index function is first formulated for the closed-loop performance. The optimal control input is then calculated based on the Taylor series expansion of the index function. For providing information to the control design, mathematical model of the EHS is also derived. Finally, effectiveness of the proposed controller is successfully validated through experimental results of different testing conditions.

A Robust Simplified Backstepping Control Approach for Pump-Controlled Electro-Hydraulic Systems

Researches for improving both the control performance and energy efficiency of electro-hydraulic systems in industrial applications have been increasing in recent decades. Existence of nonlinearities, uncertainties, and unknown terms in the system dynamics are however the main obstacles to obtain the excellent performance. To contribute a high-accuracy tracking control by dealing with these problems, this paper proposes an advanced position controller for a pump-controlled electro-hydraulic system. Here, the nonlinearities are treated by a simplified backstepping technique while the unknown terms, including external disturbances and deviations of uncertainties, are covered by a robust law. An asymptotic tracking performance of the closed-loop system in the presence of bounded disturbances is then successfully validated by theoretical proof and extensive experiments.

Direct nonlinear control for an electro-hydraulic system

In this paper, an adaptive nonlinear controller is presented for position tracking control problem of a pump-controlled Electro Hydraulic System (EHS). The system nonlinearities are compensated by an advanced backstepping-based technique while all uncertainties including uncertain parameters and external disturbances are estimated directly from the state control errors. For supplying necessary information to the controller, mathematical model of the EHS is derived in which a view of certain, uncertain and nonlinear terms is clearly represented. The control input is then synthesized from candidate Lyapunov functions which are adopted to combine the adaptive law and the control algorithm. Finally, effectiveness of the proposed controller is evaluated through simulation results of different testing conditions.