CO-SIMULATION BASED DESIGN AND EXPERIMENTAL VALIDATION OF CONTROL STRATEGIES FOR DIGITAL FLUID POWER SYSTEMS

This work presents and experimentally validates the use of co-simulations in the virtual prototyping of control strategies for a digital hydraulic system. Co-simulations allow analysis of complex systems by partitioning the latter into a collection of well defined, interacting sub-systems and components. This approach is well suited for analysis of digital hydraulics. The system under consideration is composed of four two way, two position, on-off solenoid poppet valves connected to a double rod hydraulic cylinder actuator The control task is to schedule the opening and closing of the valves to provide precise control of the requested actuator position. The actuator and valve dynamics are modeled as lumped parameter systems given by first order Ordinary Differential Equations (ODEs). The equations are solved simultaneously using a computationally efficient Chebyshev expansion approach. All co-simulations took no more than 10 seconds of computational time to execute on a standard PC with an Intel Core i7 processor The valve and piston dynamics are fully coupled through exchange of flowrate and pressure data between the appropriate components. Coupling and data exchange were performed using the co-simulation environment CoSIM, which allows connection of arbitrary number of components in arbitrary configurations. The valve actuation strategies were based on selected versions of Bang-Bang control. The most successful was able to keep the actuator displacement with practically no oscillations about the requested set point. Preliminary results show that excellent position control characteristics can be obtained to within 2-3 percent of experimental data.