Hydraulic valve-based active-heave compensation using a model-predictive controller with non-linear valve compensations

This work showcases the development and results of a model-predictive controller (MPC) for a marine active-heave compensation (AHC) system. The system utilizes a common hydraulic 4-way, 3-position proportional valve where the hysteresis, dead-band and non-linear properties have been overcome to directly control a radial piston motor in the experimental test setup. The MPC controller, with a set-point prediction algorithm, is used to actuate the unloaded hydraulic test system and the results are compared to a tuned Proportional-Integral-Derivative (PID) controller operating the same experimental setup. The MPC controller is found to track a variety of test cases and references while outperforming the tuned PID controller for all experiments. Additionally, a MATLAB Simulink model of the experimental setup is created and validated. Within the simulator, a load is then applied to the winch to test how the MPC and PID performance compare under loaded operating conditions. Based on the results of these tests, simulations of an MPC controller running in parallel with a Proportional-Integral (PI) controller are carried out for both the unloaded and loaded scenarios. For the conditions tested in this research, the resulting simulations suggest that the MPC-PI controller is able to decouple up to 99.6% of the transmitted motion.