Session: Controls 3

Paper Number: 111712

111712 - A Speed-Controlled Cylinder With Pressure Control and Load-Holding Capability - an Experimental Study 

This paper contributes to implementing a speed-controlled cylinder with the lowest chamber pressure control and load-holding function in a real application characterized by overrunning loads. The load-holding function is designed to be triggered in experiments under emergencies or standstill commands.

In a speed-controlled cylinder, two hydraulic cylinder chambers are directly connected to one or two hydraulic pumps driven by electric servo motors separately. An accumulator is used to store the cylinder differential volume. The cylinder motion is controlled by the servo motor speed. There is no valve throttling in the system. Therefore, the system's energy efficiency is greatly enhanced compared to a valve-controlled system. However, the lowest cylinder chamber pressure always equals the reservoir pressure and is not controllable, which leads to low system stiffness and undermines system stability. Furthermore, the passive load-holding function enforced by legislation for hydraulic cylinders used for, for example, lifting crane booms, is also difficult to implement due to the uncontrollable lowest chamber pressure.

In this study, a speed-controlled cylinder with the lowest chamber pressure control and passive load-holding capability driving a boom crane will be investigated. A non-linear model of the boom crane driven by the proposed speed-controlled cylinder will be created in MATLAB/Simulink and experimentally validated. The degree of state coupling will be analyzed through model linearization and the relative gain array method. Feedback controllers will be designed in simulations to realize position control, lowest chamber pressure control, and load-holding under standstill command. The feedback controllers will be implemented on the test bench. The cylinder position tracking performance, lowest chamber pressure control error, and load-holding performance will be shown and analyzed.

Presenting Author: Wei Zhao University of Agder

Presenting Author Biography: The author is doing his PhD in University of Agder, specialized in mechatronics systems. His research topic is about utilizing the speed-controlled cylinder to increase the system energy efficiency. The research target is large off shore knuckle boom cranes.