This design includes an ideal Permanent Magnet Synchronous Machine (PMSM) model, as well as a continuous D-Q controller and drive circuit. The mechanical load model includes static and kinetic friction, a steering force that varies with rack displacement, as well as various mass, inertia, damping and spring/stiffness elements of the steering system. The steering torque, applied by the vehicle's driver, is assisted by torque from the motor scaled by the gear ratio. For the control, a non-linear gain profile is specified in the "torque_assist_table" function, and a lead-lag compensator is used to improve system stability.
Note that this is a "tunable" design. Many of these system parameters can be changed by the user. Then a new simulation can be run and the updated results can be observed in the waveform viewers.
In a companion versions of this design, "EPS System with MotorSolve Generated PMSM Model and Ideal Drive", the ideal PMSM is replaced with a more realistic motor model generated by MotorSolve, the motor design tool. That model includes cogging torque, saturation and torque ripple behavior, which is seen to have a significant effect in this power steering application.
A second companion design, "EPS System with MotorSolve Generated PMSM Model and DQ/SVM Drive", uses both the MotorSolve motor model and also a sampled-data D-Q control algorithm and space-vector modulation (SVM) to control the switches in a power electronics circuit. This shows the ability to develop motor control and drives at the abstract level and also at the circuit level.