Modeling and Control Design for an Inlet Metering Valve-Controlled Pump Used to Control Actuator Velocity Via H-Infinity and Two-Degrees-of-Freedom Methods

Abstract

Using a unique inlet metering pump with fixed displacement and speed, this work introduces a new way to control a linear hydraulic actuator velocity. The inlet metering system consists of an inlet metering valve that adjusts the hydraulic fluid flow that enters the pump and a fixed displacement pump. Fluid is supplied to the inlet metering valve at a fixed pressure. Energy losses associated with flow metering in the system are reduced because the pressure drop across the inlet metering valve can be small compared to a traditional valve-controlled system. A velocity control system is designed using the inlet metering pump to control the fluid flow into a hydraulic cylinder. First, the valve dynamic model is ignored, the open-loop response is studied, and closed-loop proportional and proportional derivative controllers are designed. Next, the valve dynamic model is included and closed-loop proportional integral derivative, H∞, and two-degrees-of-freedom controllers are designed. Designs with the goals of stability and performance of the system are considered so that a precise velocity control system for the hydraulic cylinder is achieved. In addition to the potentially high efficiency of this system, there is potential for low-cost, fast-response, and less complicated dynamics compared to other systems. The results show that the velocity control system can be designed so that the system is stable for all cases and with 0% overshoot and no oscillation depending on valve dynamics using the two-degrees-of-freedom controller for tracking the desired velocity.

Design of uncertain displacement controlled velocity control system for hydraulic actuator

“…The leakage losses within the system are represented by the leakage coefficient, denoted as . In this analysis, the leakage coefficient is assumed to remain constant and its value is taken as one-tenth of the ratio of the maximum volumetric flow rate to the maximum pressure, [ 21 ].…”

H∞ Loop Shaping Control Design of the Rotational Velocity of a Hydraulic Motor

“…(3) where is the supplied volumetric flow by the pump which is defined as, The coefficient of leakage, , was supposed to be a constant. It is suggested by the literature that a sensible value for this coefficient is [14].…”

“…2 by relating the external inputs ( and ) to the outputs z1 and z2 while ignoring the uncertainty (letting Δ=0). For this to be done, Equation ( 20) should be satisfied [14].…”

“…In [13], sliding mode control was used to control the motion of a hydraulic actuator. In [14], H-infinity controller, two degrees of freedom controller (2DOF), and PID controller were designed to control the velocity of a linear hydraulic actuator. Inlet throttled pump was used for the flow control purposes.…”

Analytical Position Control System of a Linear Hydraulic Actuator Used in Aircraft Applications

“…There are two main techniques by using of which the flow is controlled; valve control systems and pump controlled systems. In valve controlled systems, the flow of a fixed displacement and speed pump is controlled using throttling valve that is placed either at the pump outlet [1,2] or at the pump inlet [3][4][5] while in pump control systems the flow is controlled by adjusting either the displacement [6][7][8] or the speed of the pump [9,10]. Valve control systems suffer from low efficiency due to the power lost across the valves.…”