Isothermal Liquid Systems

How the Foundation library can be used to model systems that span electrical, mechanical and isothermal liquid domains. In the model, a hydraulic system implemented in the isothermal liquid domain controls the mechanical load position in response to a voltage reference demand. If the reference demand is zero, then the hydraulic actuator (and load) displacement is zero, and if the reference is +5 volts, then the displacement is 100 mm.

Use the Foundation library to model systems that span electrical, mechanical and isothermal liquid domains.

A two-way valve acting in a closed-loop circuit together with a double-acting cylinder implemented in the isothermal liquid domain. The controller is represented as a continuous-time transfer function plus a transport delay. The delay allows for the computational time (one discrete time period) plus the zero-order hold (half a discrete time period) when implemented in discrete time. The model is configured for linearization so that a frequency response can be generated. To configure for faster desktop simulation, comment through the transport delay and increase the solver maximum step size.

A physical system model and controller configured for HIL testing. It is derived from example Hydraulic Actuator with Digital Position Controller, ssc_isothermal_liquid_actuator_digital_control. The model has been configured for HIL testing by performing the following steps:

The effects of entrained air in a custom double acting cylinder. During the repeating cycle of oscillating pressure, the absolute pressure does not get below absolute zero as the bulk modulus of the homogeneous liquid-gas mixture decreases accordingly at low pressures.