Characterization and Attenuation of Sandwiched Deadband Problem Using Describing Function Analysis and Its Application to Electro-Hydraulic Systems Controlled by Closed-Center Valves

Sandwiched deadbands can be seen in a wide variety of systems, such as electro-hydraulic systems controlled by closed-center valves. In such a system, the deadband is between the plant and actuator dynamics and therefore can not be compensated directly like an input deadband. Though this sandwiched deadband problem may be attenuated to certain degree through sophisticated advanced control techniques, the increased cost and the necessity of actuator state feedback prohibit their widespread application in the industry. An economical and popular method is to add an inverse deadband function in the controller to cancel or compensate the highly nonlinear behavior of the deadband. However, such a solution requires that the dynamics before the deadband (eg. the valve dynamics) is fast enough to be neglected — a requirement that can not be met in reality unless the closed loop bandwidth of the overall system is limited very low. To raise the achievable closed loop bandwidth for a much improved control performance, it is essential to be able to precisely characterize the effect of this sandwiched deadband on the stability and performance of the overall closed-loop system, which is the main focus of the paper. Specifically, a describing function based nonlinear analysis will be conducted to predict when the instability will occur and how the resulting limit cycle depends on the actuator dynamics and the targeted closed-loop bandwidth. Based on the analysis, the optimal closed-loop bandwidth can be determined to maximize the achievable overall system performance. The technique is applied to an electro-hydraulic system controlled by closed-center valves to optimize the controller design.Copyright © 2004 by ASME

[1]  George T.-C. Chiu,et al.  Adaptive robust motion control of single-rod hydraulic actuators: theory and experiments , 2000 .

[2]  Gang Tao,et al.  Neural-hybrid control of systems with sandwiched dead-zones , 2001, Proceedings of the 2001 American Control Conference. (Cat. No.01CH37148).

[3]  Gang Tao,et al.  Adaptive Control of Systems with Actuator and Sensor Nonlinearities , 1996 .

[4]  Wayne J. Book,et al.  Practical Implementation of a Dead Zone Inverse on a Hydraulic Wrist , 2002 .

[5]  Song Liu,et al.  Energy-Saving Control of Single-Rod Hydraulic Cylinders with Programmable Valves and Improved Working Mode Selection , 2002 .

[6]  Arthur Gelb,et al.  Multiple-Input Describing Functions and Nonlinear System Design , 1968 .

[7]  Fanping Bu,et al.  Nonlinear adaptive robust control of hydraulic actuators regulated by proportional directional control valves with deadband and nonlinear flow gains , 2000, Proceedings of the 2000 American Control Conference. ACC (IEEE Cat. No.00CH36334).

[8]  Bin Yao,et al.  High performance adaptive robust control of nonlinear systems: a general framework and new schemes , 1997, Proceedings of the 36th IEEE Conference on Decision and Control.

[9]  Masayoshi Tomizuka,et al.  Adaptive robust control of SISO nonlinear systems in a semi-strict feedback form , 1997, Autom..

[10]  Gang Tao,et al.  An adaptive dead-zone inverse controller for systems with sandwiched dead-zones , 2001, Proceedings of the 2001 American Control Conference. (Cat. No.01CH37148).

[11]  Bin Yao,et al.  Programmable valves: a solution to bypass deadband problem of electro-hydraulic systems , 2004, Proceedings of the 2004 American Control Conference.