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

Unlike input deadband, the sandwiched deadband between actuator and plant dynamics is very difficult to be explicitly compensated for due to the proceeding actuator dynamics whose effect may not be negligible. The paper presents a practical way to overcome the design conservativeness of existing methods in dealing with sandwiched deadband. Specifically, a describing function based nonlinear analysis method is proposed to characterize the effect of the sandwiched deadband on the stability and performance of the overall closed-loop system. The analysis results can be used to determine the highest closed-loop bandwidth that can be achieved without inducing residual limit cycles and instability. Optimal controller parameters can then be found to maximize the achievable closed-loop control performance. The technique is applied to an electrohydraulic system controlled by closed-center valves and a nonlinear feedback controller. Simulation results showed severe oscillations as the feedback control gains are increased to the predicted threshold values. Comparative experimental results also showed the effectiveness of the proposed method in reducing the conservativeness of traditional design and the improved closed-loop control performance in implementation.

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

[2]  Gang Tao,et al.  Neural‐hybrid control of systems with sandwiched dead‐zones , 2002 .

[3]  Song Liu,et al.  Coordinate Control of Energy Saving Programmable Valves , 2008, IEEE Transactions on Control Systems Technology.

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

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

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

[7]  Gang Tao,et al.  An adaptive dead-zone inverse controller for systems with sandwiched dead-zones , 2003 .

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

[9]  H. E. Merritt,et al.  Hydraulic Control Systems , 1991 .

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

[11]  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.

[12]  Miroslav Krstic,et al.  Nonlinear and adaptive control de-sign , 1995 .

[13]  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).

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