AN ANALOG-DIGITAL HYDRAULIC CYLINDER VELOCITY CONTROL SYSTEM FOR MOBILE MACHINES

Abstract

Hydrostatic drive systems with linear actuators are commonly used in variety of mobile machines and vehicles. One of important aspect of its operation is cylinder velocity control in variable operating conditions, such as different load, pump pressure and engine rotational velocity. The aim of this article is to create an algorithm, which would control velocity of a hydraulic cylinder used in such systems. One way to create cylinder velocity control system is to perform an identification, which would characterize this system. To do this work it was appropriate to use test stand with excavator equipment. The first part of the article includes the description of the stand and enumerates parts that compose it. Correct work of the control system is possible through use of a proper controller. For achieving a desired purpose, a PID controller was used with some modifications improving system's operation. The controller parameters were tuned based on the model of the system, obtained on the basis of estimation, for different operational conditions. To do this, a tool of MATLAB Simulink called Parameter Estimation was used. The control algorithm, in automatic mode, makes system tuning based on coefficients array. The final stage of the research work was to conduct verification tests, which let to assess a correctness of the created and proposed control system.