Abstract
Pump-controlled asymmetric cylinders need some kind of compensation for the difference between the in- and outlet flow. This can be done by using valves or additional pump/motors. An advantage with using valves is that only one pump/motor is required, but problems with mode-switch oscillations are more likely to occur. On the other hand, cylinder areas should be well matched with the pump/motor displacements for pump/motor compensation if the pump/motors are fixed and connected to the same shaft. However, this problem is avoided if the pump/motors are individually controlled. Furthermore, with individually controlled pump/motors, it is possible to control the pressure in one of the cylinder chambers and the piston speed simultaneously. This paper is focusing on such architectures. There are several possible configurations for architectures and control strategies for individually controlled pump/motors, and some are compared here. Results show that one of the configurations is more efficient than the others, but that it is less efficient than valve-compensation (assuming large valves). A controller design where one pump/motor is used to control the speed and another to control the pressure is suggested. Results show that the controller should be adapted based on the mode of operation.
