Modeling and Validation of Moving Coil Actuated Valve for Digital Displacement Machines

This paper concerns a novel moving coil actuator integrated with a high-performance seat valve for use in digital displacement machines (DDM), which is an emerging fluid power technology that sets strict actuator requirements in order to get a high energy conversion efficiency. Hence, the mechanical switching time must be in the millisecond range and the actuator power consumption must be in range of few tens of watts. The objectives are twofold: First, establish a proof-of-concept for the integrated actuator/valve that relies on several principles and mechanisms new or uncommon in fluid power applications. Second, formulate and validate a transient numerical model describing the actuator/valve. A coupled simulation model is established to predict the switching performance in which transient electromagnetic finite-element-analysis with dynamic remeshing is coupled to a set of ordinary differential equations describing the motion dynamics. In this way, the movement induced hydromechanical fluid forces caused by rapid acceleration of the valve plunger is coupled with the electromagnetic dynamics. The proposed model is compared rigorously against measurements obtained from a series of experiments based on a fully operational valve prototype. Comparisons of, e.g., transient flux density, current, and plunger position, show that the model describes both the actuator and the valve motion very well. Finally, results are presented when testing the prototype valve in fully operational DDM to establish proof-of-concept for the proposed valve concept. The actuator/valve is shown to be capable of rapid switching in less than 4 ms, while only consuming approximately 45 W corresponding to 0.7% of the machine output power.