Abstract
Electro-hydrostatic actuator (EHA) is an important type of power-by-wire (PBW) which is a highly integrated closed volume control system with the advantages of high reliability, high efficiency and easy maintenance. However, under heavy load conditions, a large amount of heat the EHA motor produces affects the system’s working time and even the system life, which restricts the widespread application of EHA systems. In order to solve the problem of motor heating and the contradiction between high dynamics and high efficiency of the EHA system, a novel active load-sensitive principle and structure of EHA system is proposed based on the load-sensitive principle. The active load-sensitive EHA (ALS-EHA) is a dual control variable system consisting of a motor pump main loop and a load-sensitive loop. As for the latter, the system load pressure is introduced into a special designed and optimized pressure fellow valve (PFV). The valve outlet is connected to the plunger pump swash plate variable mechanism. The EHA pump displacement is actively adjusted by controlling the current input to PFV. The two-degree-of-freedom cooperative control for the output flow of the pump can be implemented by adjusting the motor speed and the pump displacement. An energy optimal robust control law based on fuzzy and disturbance compensation is presented for the control architecture. The simulation results show that the ALS-EHA system based on the control law proposed in this paper can effectively reduce the motor heat while ensuring the dynamic performance of the system.
Highlights
With the emerging development of More/All-ElectricAircraft (MEA/AEA), PBW has become the spread trend of flight control actuation system, which has attracted extensive attention and research [1]–[4]
CONTROL ALGORITHM In order to solve the contradiction between high dynamics and high efficiency of the ElectroHydrostatic Actuator (EHA) system, we need to make the motor and the entire EHA system work as high efficiently as possible, but still increase the displacement ratio as much large as possible to improve the system Dynamic performance
Based on the above results, several advantages of active load-sensitive EHA (ALS-EHA) with the energy optimal control law based on fuzzy and disturbance compensation designed in this paper can be summarized: 1) The system efficiency is optimized in real time to ensure that the system operates in the high efficiency range; 2) Combined with fuzzy control, real-time adjustment of displacement according to working conditions, the system dynamic performance is better; 3) Introduce load disturbance compensation to avoid displacement instability caused by load disturbance, and the system has strong disturbance rejection ability; 4) For Low-speed operation, small displacement is usually used to increase the speed of the motor-pump set, avoiding the low-speed unstable region of the motor-pump set, so the system has better control performance and more stable lowspeed operation
Summary
With the emerging development of More/All-ElectricAircraft (MEA/AEA), PBW has become the spread trend of flight control actuation system, which has attracted extensive attention and research [1]–[4]. Load pressure, and angular acceleration of the motor are taken as constant values and combined with the flow rate formula, the total efficiency of the system can be expressed as a single variable with displacement. In other words, when the total system efficiency is the highest, the motor heat output is not necessarily the minimum point This is because the volume and mechanical loss of the pump cause power loss. The larger the system displacement is, the faster the speed adjustment is, and the better the dynamic performance of the system is
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