Load control of electrically controlled hydraulic pump´s flow/pressure characteristics testing with direct drive servo-proportional valve

To obtain a fast, precise and data-comparable flow/pressure characteristics test method for electrically controlled hydraulic pump (ECHP), we summarized the disadvantages of the manually-operated throttle valve loading method, which is recommended by ISO 17559-2003, and introduced a new loading method, which loaded the tested ECHPs with direct drive servo-proportional valve (DDV). After analyzing the mathematic model of the DDV loading system, we loaded the tested pump in constant-delivery-flow operating mode (CDFOM) with pressure-feedback control algorithm to control the load, i.e. the pump´s output pressure, and in constant-pressure operating mode (CPOM) with DDV-spool-position open-loop control algorithm to adjust the pumps output flow. Especially we adopted feed-back linearization and PI control algorithm to make the tested pump´s output pressure accurately tracking a certain slope command, whose slope had serious effect on the measurement of pump´s output flow in CDFOM. The experiment results show that, with pressure feedback control, the new loading method can stably control the load of the tested pump, so that the repeatability of the load can be dramatically improved. With the aid of computer, the new loading method can also be easily automated, and can quicken the flow/pressure characteristics test process remarkably.