Hydraulic Closed-Loop Actuator with Fixed-Step Integration

This example shows two versions of the same closed-loop hydraulic actuator built of the cylinder, proportional 4-way directional valve, pressure-compensated variable-displacement pump, and the load that includes inertia, friction, spring, and time-varying force. The motion profile is generated by the Control Unit. The error signal is processed by the dynamic compensator before it is applied to the Proportional Valve Actuator.

The upper version of the actuator is built of standard SimHydraulics® blocks. In the lower version, the cylinder and the valve are replaced with their simplified versions. Both versions were developed for applications that require fixed-step integration. For this reason, the integration method for Simulink® blocks is set to ode3 (Bogacki - Shampine) method, while the Simscape™ blocks are set to the Backward Euler method with the fixed-cost runtime consistency iterations (see settings in the Solver Configuration blocks). The sample time in set to 0.001 s.

To compare the accuracy of the models, the difference between error signals is determined. It shows that the simplified model of the system is pretty close to the version built of the standard blocks, while the run time of the simplified version is at least two times faster. The example is intentionally built in such a way that the versions of the system can easily be separated and run as individual systems for comparison.

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