This Electric Power Steering (EPS) System design includes a PWM Switching Inverter circuit that uses Toshiba TPHR7904PB Power MOSFETs. The drive includes a D-Q control algorithm, and uses space-vector modulation (SVM) to generate digital PWM signals. These control the ON/OFF state of the switches.
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, the first gain/pole-zero block (far left) specifies the amount of "torque_assist" gain (assist torque as a multiple of the vehicle operator's torque applied to the steering wheel), as well as providing compensation to improve system stability.
This design focuses on the performance of the switches in the inverter circuit, including tracking of the thermal characteristics of one representative switch. In a companion version of this design, "EPS System with PMSM - Pre-Circuit Design for Toshiba Drive", Clarke and Park Transform models are used with a continuous ideal voltage drive, and provides much faster simulation results with a focus on overall system dynamic performance.