Hydrostatic Actuator Drive Control with Pump Leakage Compensation

Abstract

The paper presents research of the hydraulic cylinder drive system equipped with gear pump driven by asynchronous motor fed by the frequency inverter using a developed method of pump leakage compensation (LPC) to control the flow. The pump parameters at various pressures and various angular speeds of the asynchronous motor, including in the speed range below the minimum recommended by the pump manufacturer, have been tested. The obtained pump characteristics showed the presence of two components of internal pump leakage - independent and dependent of pressure. The linear internal leakage model was developed for the pump. This model has been implemented to the verified model of the drive system of the variable ratio mechanism driven by a hydraulic cylinder - scissor lift. The pump flow correction algorithm has been added to the previously developed hydraulic cylinder speed control system. This correction was aimed at improving the mapping of the assumed speed of the hydraulic cylinder. The compensation block has been added to the hydrostatic drive of the scissor lift equipped with an open control system - developed in the LabView environment. Experimental tests confirmed the improvement in mapping of the hydraulic cylinder assumed speed regardless of its variable load resulting from the scissor system geometry and the weight of the load on the scissor lift platform. The developed leakage compensation system on the pump can be used in hydrostatic systems with fixed or variable ratio, regardless of the load on the hydraulic cylinder.