Electrohydrostatic actuators (EHAs), as a class of pump-controlled hydraulic actuators, are known for energy efficiency and easy maintainability. Thus, they can be widely used in the situations where actuating pressure/force control of hydraulic actuators is essential. Examples are automotive active suspension, deep-drawing press, molding machine, and vibration isolation. However, a leaky piston seal in an EHA system can be especially problematic as it is not visually detectable, but causes internal leakage flowing across actuator chambers impairing the performance. This paper employs quantitative feedback theory (QFT) to design a robust fixed-gain linear actuating pressure controller that is tolerant to actuator internal leakage. Since QFT captures uncertainties by templates, representing frequency responses of the plant on Nichols chart, the first step, to design a QFT controller, is to establish plant templates. In doing so, a set of offline parametric system identifications are implemented, and the family of identified models, providing frequency responses, are used to design the QFT fault-tolerant controller. The controller also satisfies the prescribed design tolerances on tracking, stability and sensitivity (disturbance rejection at plant output) under different conditions, including various levels of actuator internal leakage, environmental stiffnesses, and load masses. The ability of the controller to maintain actuating pressure within the acceptable response envelope is demonstrated in experiments. The experimental results show that the system specifications are satisfied despite internal leakage up to 12 L/min.
Fault-Tolerant Actuating Pressure Controller Design for an Electrohydrostatic Actuator Experiencing a Leaky Piston Seal
Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT, AND CONTROL. Manuscript received May 7, 2016; final manuscript received November 21, 2016; published online March 22, 2017. Assoc. Editor: M. Porfiri.
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Ren, G., Song, J., and Sepehri, N. (March 22, 2017). "Fault-Tolerant Actuating Pressure Controller Design for an Electrohydrostatic Actuator Experiencing a Leaky Piston Seal." ASME. J. Dyn. Sys., Meas., Control. June 2017; 139(6): 061004. https://doi.org/10.1115/1.4035348
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