Here are some guidelines to assist in the process of building a multi-domain physical model that connects a hydraulic motor from SimHydraulics 1.5 (R2009a) and an induction motor from SimPowersystems 5.1 (R2009a) together. An example model titled "hydraulic_and_induction_motor_coupling" which demonstrates this coupling is included below.
In this task, our goal is to connect 'hydraulic motor' and 'induction motor' blocks that are in two different physical domains, namely hydraulic and electric. While building multidomain physical models, it is recommended to use Simscape and associated vertical products together. In view of that a general recommendation is to use blocks from SimElectronics (such as induction motor block) in multidomain modeling instead of SimPowerSystems as SimElectronics is based on Simscape while SimPowerSystems is not. This allows direct physical connections between the domains and the entire physical network to be computed under a single solver.
However, SimPowerSystems is better equipped to model three-phase or other multi-phase electrical systems than SimElectronics. Therefore, this example uses a hydraulic motor from SimHydraulics and a 3-phase induction motor from SimPowerSystems.
To connect blocks from these different products together, one will need to use a number of converter blocks which convert bi-directional signals in SimPowerSystems to unidirectional Simulink signals and then from Simulink signals to the bi-directional physical signals used in Simscape/SimHydraulics. Similarly, another set of converter blocks must be used to convert signals from Simscape/SimHydraulics through Simulink to SimPowerSystems.
The conversion of Simulink signals to physical signals and its reverse can be achieved using "S-PS" and "PS-S" converter blocks, respectively. These blocks are available in the Simscape-->Utilities library. The measurement signals of SimPowerSystems based blocks provide a Simulink signal as their output directly.
Since we are building a model that is composed of blocks from SimPowerSystems, SimHydraulics/Simscape, and Simulink, three different solvers would be used to solve different parts of the multi-domain system. The POWERGUI block/solver will be used to solve the electrical part of the system that is developed using SimPowerSystems blocks while the Simscape Solver would be used to solve the Simscape/SimHydraulics part of the system. A Simulink solver would then simulate the entire system consisting of SimPowersystems and SimHydraulics blocks. For solving the nonlinear dynamics presented by the use of SimPowerSystems and SimHydraulic blocks, use of a stiff solver such as 'ode23t' is recommended.
As the shafts of the two motors are to be coupled together, the two motors are expected to be running at the same speed. This is simulated by sensing the speed of the hydraulic motor and using it as a velocity input for the induction motor. The torque output of the induction motor is inturn used to drive hydraulic motor. A physical coupling between the two motors is simulated using a rotational spring-damper system constructed using Simscape blocks.
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