Session: Controls 3

Paper Number: 109710

109710 - Control of an Asymmetric Cylinder With Two Individually Controlled Pump/Motors 

Pump-controlled asymmetric cylinders need some kind of compensation for the difference between the in- and outlet flow. This can be done by either using some kind of valve arrangement or an additional pump/motor. An advantage with using valves is that only one pump/motor is required, but it is well known that problems with mode-switch oscillations can occur when the load case is in-between resistive and driving. Architectures based on pump/motor compensation tend to have less problems with mode-switch oscillations, even though it can occur. A critical problem with pump/motor compensation is, however, that the cylinder areas must be well matched with the pump/motor displacements. This applies if the two pump/motors are fixed and connected to the same shaft, but the problem can be avoided if the two pump/motors are individually controlled, and other advantages are then also added. This paper is focusing on control of such architectures.

With individually controlled pump/motors, it is possible to control the pressure in one of the cylinder chambers and the velocity simultaneously. In turn, this means that it is possible to control the stiffness, and it makes it possible to move the points of operation to more efficient regions. Furthermore, installation and maintenance are simple compared to many other pump-controlled architectures.

There are several possible configurations for architectures based on individually controlled pump/motors, and there are many principally different possible strategies on how to perform the control of an asymmetric cylinder with two individually controlled pumps. The aim with this paper is to compare the architectures and control strategies. Focus is on dynamic behaviour for different load cases.

Presenting Author: Samuel Kärnell Linköping University

Presenting Author Biography: Received a Ph.D. in fluid power at Linköping University (LiU), Sweden, in 2022. He is currently a postdoc at LiU. His research interest primary includes pumps and pump-controlled systems.