Dead-zone Compensation Research Articles

Position control of ultrasonic motors using MRAC with dead-zone compensation

The ultrasonic motor has a heavy nonlinearity, which varies with driving conditions and possesses variable dead zone in the control input associated with applied load torque. This dead zone is a problem as an accurate positioning actuator for industrial applications and it is important to eliminate the dead zone in order to improve the control performance. This letter proposes a new position control scheme for ultrasonic motors, to overcome the load-torque-dependent dead zone employing model reference adaptive control with dead-zone compensation. The dead zone is compensated by an observer, whereas model reference adaptive control performs accurate position control. Mathematical models are formulated and experimental results are given to validate the proposed position control scheme.

Deadzone compensation in motion control systems using neural networks

A compensation scheme is presented for general nonlinear actuator deadzones of unknown width. The compensator uses two neural networks (NNs), one to estimate the unknown deadzone and another to provide adaptive compensation in the feedforward path. The compensator NN has a special augmented form containing extra neurons whose activation functions provide a "jump function basis set" for approximating piecewise continuous functions. Rigorous proofs of closed-loop stability for the deadzone compensator are provided and yield tuning algorithms for the weights of the two NNs. The technique provides a general procedure for using NNs to determine the preinverse of an unknown right-invertible function.

Deadzone compensation in motion control systems using adaptive fuzzy logic control

A deadzone compensator is designed for industrial positioning: systems using a fuzzy logic (FL) controller. The FL approach is shown to subsume other approaches that use switching or indicator functions. The classification property of FL systems makes them a natural candidate for the rejection of errors induced by the deadzone, which has regions in which it behaves differently. A tuning algorithm is given for the FL parameters, so that the deadzone compensation scheme becomes adaptive, guaranteeing small tracking errors and bounded parameter estimates. Formal nonlinear stability proofs are given to show that the tracking error is small. The adaptive FL deadzone compensator is implemented on an actual industrial CNC machine tool to show its efficacy.

Position Control of Ultrasonic Motors with Dead-zone Compensation

The dead-zone effect for control input of ultrasonic motor arises with applied load torque. The dead-zone is a problem as a accurate positioning actuator for industrial applications and it is important to eliminate the dead-zone in order to improve the control performance. This paper proposes a position control scheme of ultrasonic motors taking dead-zone compensation into account.

Deadzone compensation in discrete time using adaptive fuzzy logic

A fuzzy logic (FL) compensator is designed for control of nonlinear discrete-time systems with input deadzone. The classification property of FL systems makes them a natural candidate for the rejection of errors induced by the deadzone, which has regions in which it behaves differently. A discrete-time tuning algorithm is given for the FL parameters so that the deadzone compensation scheme becomes adaptive, guaranteeing bounded tracking errors and parameter estimates. A rigorous proof of stability and performance is given and a simulation example verifies performance. Unlike standard discrete-time adaptive control techniques, no certainty equivalence assumption is needed.

Adaptive fuzzy logic compensation of actuator deadzones

A deadzone compensator is designed for nonlinear systems using a fuzzy logic (FL) controller. The classification property of FL systems makes them a natural candidate for the rejection of errors induced by the deadzone, which has regions in which it behaves differently. A tuning algorithm is given for the FL parameters so that the deadzone compensation scheme becomes adaptive, guaranteeing small tracking errors and bounded parameter estimates. A rigorous proof of stability and performance is given and a simulation example verifies excellent performance. It is seen that the extra signal produced by the adaptive FL deadzone compensator can be considered as an adaptive dithering term. ©1997 by John Wiley & Sons, Inc.

Adaptive fuzzy logic compensation of actuator deadzones

A deadzone compensator is designed for nonlinear systems using a fuzzy logic (FL) controller. The classification property of FL systems makes them a natural candidate for the rejection of errors induced by the deadzone, which has regions in which it behaves differently. A tuning algorithm is given for the FL parameters so that the deadzone compensation scheme becomes adaptive, guaranteeing small tracking errors and bounded parameter estimates. A rigorous proof of stability and performance is given and a simulation example verifies excellent performance. It is seen that the extra signal produced by the adaptive FL deadzone compensator can be considered as an adaptive dithering term. ©1997 by John Wiley & Sons, Inc.

Adaptive dead-zone compensation for output-feedback canonical systems

An adaptive output feedback dead-zone compensation scheme is designed for systems with an unknown dead-zone at the input of an n th-order smooth nonlinear dynamics in the output-feedback canonical form. The proposed adaptive controller employs an adaptive dead-zone inverse to cancel the dead-zone and uses a backstepping design for adaptive output feedback control. It has a new state observer parametrization that is needed to handle the dead-zone uncertainty and a new robust control law that is suitable for the parameter projection needed to implement an adaptive dead-zone inverse. The adaptive dead-zone compensation design ensures closed-loop signal boundedness and improves system tracking performance.

Analysis of Piecewise Linear Systems by the Method of Integral Equations

Analysis of piecewise linear systems may require the solution of high-order linear differential equations whose parameters are constants within a given region but change into different constants for adjacent regions. The multiple regions of such a system may be identified with discrete intervals and it is a simple matter to obtain the system response by the method of integral equations. These solutions are given in the form of convergent infinite series, the terms of which may be easily evaluated by a digital computer. The time interval of each region is found by substituting successive values of these truncated series until the required boundary conditions are satisfied. The method is applied to a third order-type two system whose sustained oscillation, when subjected to dry friction, is to be eliminated by dead-zone compensation. The system has four regions with different parameters for each region of the differential equations which are converted into Volterra integral equations of the second kind. The variables are iterated within the digital computer until a convergent solution is found for the condition of sustained oscillation. Procedures are given to determine critical values of dead zone for various ramp rates at which the system is stable.