Coordinate Control of Energy Saving Programmable Valves

As applications of electro-hydraulic systems become increasingly widespread, the demand for low cost, high-level control performance and significant energy saving schemes gets stronger and stronger. The recently developed energy-saving programmable valves, a unique configuration of five independently controlled poppet type cartridge valves, provide hardware possibility to meet the demand. Preliminary research work has shown that the program valves' increased flexibility and controllability lead to significant energy-saving, due to the reduced working pressures of the hydraulic actuators and the full use of free regeneration cross-port flows. However, the increased hardware flexibility also results in increased complexity in controlling the system: for each system, instead of one control input to be synthesized to meet the sole objective of control performance, five control inputs have to be simultaneously determined for all five poppet valves to achieve the dual objectives of both high precision control performance and significant energy saving. This paper proposes a two-level coordinated control scheme: the task-level configures the valve usage for maximal energy saving and the valve-level utilizes adaptive robust control (ARC) technique to guarantee the closed-loop system stability and performance under various model uncertainties and disturbances. Comparative experimental results were obtained to show the high precision control performance and significant energy saving achieved with the proposed low-cost programmable valves.