A multipurpose microprocessor controller for hydraulic pumps

Hydraulic pump/motor units have a wide range of commer-cial applications, each requiring a separate bolt-on hydraulic controller. This paper outlines the results of laboratory feasibility tests, aimed at replacing these hydraulic con-trollers with an electromechanical valve actuated by a universal microprocessor based controller. Since the majority of controller functions include a pressure override capability, the constant pressure override control (CPOC) function has been investigated in detail. The CPOC controller varies the pump flow rate to ensure that the hydraulic pipeline pres-sure remains constant despite variations in load. The micro-processor required an accurate measure of average line pressure. Preliminary tests showed that the axial pump superimposed large synchronous pressure ripples onto this average level. The results show that if careful signal con-ditioning is used to remove this ripple, a microprocessor based control unit can mimic the main control function of existing hydraulic controllers successfully. Design features required for a suitable prototype controller necessary for field trials are discussed.