Digital Valve Technology Applied to the Control of an Hydraulic Valve Actuator

The use of electrohydraulic actuators in engine control applications has the potential to improve engine performance and fuel economy. Digital latching valves open and shut extremely quickly. Furthermore, by using residual magnetism, the valves remain latched in the open or closed position and only use energy when transitioning between positions.

In this paper, the control issues involved with using latching valves for closed loop position control of a piston-cylinder actuator are examined. The valve design, system models and alternative controller designs are presented. The first control design is based on minimizing a cost function measure of errors and control energy usage, which quantifies a trade-off between tracking accuracy, resolution and control energy usage. The second design, which is called inner sample modulation of the valve, is based on calculating the appropriate control action as some fraction of the sampling time. Experimental data showing trajectory tracking and control commands is included. The data supports the conclusion that digital latching valves offer a competive actuation choice in terms of control performance and control energy usage.