Closed-Loop Hydraulic Actuator Model for Real-Time Simulation

The actuator consists of a proportional 4-way directional valve driving a double-acting hydraulic cylinder. The cylinder drives a load consisting of a mass, viscous and Coulomb friction, constant force, and a spring. The actuator is powered by a variable-displacement, pressure-compensated pump, driven by a constant velocity motor. Pipelines between the valve, cylinder, pump, and the tank are simulated with the Hydraulic Pipeline blocks.

Abstract variants of the hydraulic cylinder and of the valve and pump unit are also included in the model. The model can be configured to use these abstract variants, which neglect effects such as compressibility and use simpler equations that are numerically more efficient. The model can also be configured for simulation with a fixed-step solver, as would be used in hardware-in-the-loop testing.

Model

Valve and Power Unit, Abstract Variant

Valve and Power Unit, Detailed Variant

Simulation Results from Simscape Logging

The plots below show the pressure difference between cylinder chambers A and B, as well as the position of the piston.

The plots below show the behavior of the abstract models and the detailed model. The results are very similar, indicating that the abstract models can be used without a significant loss of accuracy.

The plots below show the behavior during a simulation with a variable-step solver (Simscape™ local solver off) and a fixed-step solver (Simscape local solver on). The results are very similar, indicating that a fixed-step solver can be used without a significant loss of accuracy, and that the models can be used for hardware-in-the loop simulation.