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A typical pattern of city driving includes many accelerations and decelerations. A significant portion of the fuel energy is spent to accelerate a vehicle. This energy is typically wasted during subsequent decelerations. Capturing and reusing some of this energy would improve fuel economy. At present, it is generally accepted that electric hybrids represent a proven technology capable of capturing and reusing a portion of the braking energy. The major drawback of electric hybrids remains the high initial cost of hybrid drivetrains. An Air-Power-Assist (APA) engine, also known as “air hybrid”, accomplishes the same general type of energy storage and reuse as an electric hybrid but with greater simplicity [1, 2, 3, 4, 5].

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.