Su-Hau Hsu

A fully adaptive decentralized control of robot manipulators

In this paper, we develop a fully adaptive decentralized controller of robot manipulators for trajectory tracking. With high-order and adaptive variable-structure compensations, the proposed scheme makes both position and velocity tracking errors of robot manipulators globally converge to zero asymptotically while allowing all signals in closed-loop systems to be bounded, even without any prior knowledge of robot manipulators. Thus this control scheme is claimed to be fully adaptive. Even when the proposed scheme is modified to avoid the possible chattering in actual implementations, the overall performance will remain appealing. Finally, numerical results are provided to verify the effectiveness of the proposed schemes at the end.

Adaptive decentralized control of robot manipulators driven by current-fed induction motors

In this paper, an adaptive decentralized control scheme with a rotor-flux observer is proposed for the tracking control of robot manipulators actuated by current-fed induction motors. To cope with all parametric uncertainties in the electromechanical systems, an adaptive law is designed so that all the signals of closed-loop systems are bounded, and the tracking errors in position, velocity and rotor fluxes converge to a residual set.

Robust output high-gain feedback controllers for the atomic force microscope under high data sampling rate

This paper proposed a robust output feedback controller of an atomic force microscope (AFM) device for the purpose of high rate data sampling. The AFM device is modeled as a cantilever-sample system in which the interactive forces between the cantilever and the sample consists of a long range attractive force and short range repulsive force. By using the feedback linearization and the singular perturbation technique, an output high-gain feedback controller is designed such that the cantilever tip can track the surface of the sample at a high rate of data sampling even though the topology of the surface is arbitrary and not given a priori. By adopting the controller developed here, the signals to be measured are the deflection of the cantilever. Finally, a computer simulation is provided to demonstrate the effectiveness of the proposed controller.

Globally adaptive decentralized control of robot manipulators

In this paper, we develop a new adaptive decentralized controller of robot manipulator for trajectory tracking. With the nonlinear control terms, the closed-loop system is globally stable. Furthermore, the adaptive decentralized controller is considered with a /spl sigma/-modification term such that it becomes robust to the noise in practical implementation. Finally, a numerical study is provided to verify the effectiveness of the proposed scheme.

Adaptive speed/position control of induction motor with unknown load torque

The paper proposes an adaptive speed/position tracking control of an induction motor subject to unknown load torque. The controller is developed based on a dynamic model obtained from the d-q-axis model (w.r.t. the stationary reference frame) of the motor under a special nonlinear coordinate transform so that either the speed or position control objective can be fulfilled. The underlying design concept is to endow the close-loop system with the so-called maximal power transfer property while under lack of knowledge of some key system parameters, such as the rotor resistance, motor inertia and motor damping coefficient. To be rigorous, we present a thorough proof of the proposed control scheme based on Lyapunov stability theory. Experimental results are also given to validate the effectiveness of the scheme.

Globally adaptive decentralized control of time-varying robot manipulators

In this paper, we develop a globally adaptive decentralized control scheme of time-varying robot manipulators for trajectory tracking control. Since the proposed adaptive control law is in a decentralized manner, only low-cost hardware is required for implementation. Furthermore, even of the time-varying parameters of the robot manipulator change arbitrarily fast, both the position and velocity tracking errors of the manipulators will converge to zero after employment of the proposed adaptive control law. For practical implementation, the adaptive law can be combined with a leakage term so that there is no chattering in the motion of the manipulator but at the price a residual set of the tracking errors as mentioned above, of which the size can be however made smaller by use of some larger design parameters. Finally, in order to illustrate the performance of the proposed scheme, simulation results are also provided, which turn out to be quite satisfactory.

Globally fully adaptive decentralized control of robot manipulators

We develop a globally fully adaptive decentralized controller of a robot manipulator for trajectory tracking. With some nonlinear feedback terms, the proposed decentralized control law is guaranteed to drive the tracking error asymptotically to zero. Moreover, those nonlinear feedback terms not only improve the closed-loop property from semi-global stability to global stability but also make the position and velocity tracking errors approach to zero, which is a dual-goal hardly attained in the literature. The proposed adaptive law allows all signals in the closed-loop systems to be stabilized while making the tracking error converge to zero, even without any prior knowledge of the robot manipulator or the payload and the bound on the design trajectory so that the law can be claimed to be fully adaptive. Finally, a numerical study is provided to verify the effectiveness of the proposed scheme.

Adaptive decentralized compliant control of robot manipulators

In this paper, we develop an adaptive decentralized compliant control of robot manipulator. The robot manipulator is in contact with the environment and the contact force is normal to the contact plane. When the environment stiffness is given, an adaptive decentralized compliant controller is designed based on a Lyapunov based method such that both the force tracking error and the complementary position tracking error are bounded and will converge to zero asymptotically. On the other hand, when the environment stiffness is not given, the compliant controller above can be used with a motion modification generator such that the force tracking error will converges to a residual set whose size is small if the environment stiffness is large, and the complementary position tracking error is bounded and converges to zero asymptotically.

ADAPTIVE SPR SPEED/POSITION CONTROL OF INDUCTION MOTOR

Abstract This paper proposes an adaptive speed/position tracking control of an induction motor subject to unknown load torque via strictly positive real (SPR) analysis. The controller is developed under a special nonlinear coordinate transform such that either speed or position control objective can be fulfilled. The underlying design concepts are to endow the close-loop system while under lack of knowledge of some key system parameters, such as the rotor resistance, motor inertia and motor damping coefficient. The proposed control scheme comes along with a thorough proof derived based on Lyapunov stability theory. The experimental results are also given to validate the effectiveness of the presented control scheme.