External Speed Control of Automotive Back-to-Back Test Benches Utilizing Embedded Drivability Functions

Symmetrical back-to-back electric drive test benches provide compact and cost-effective infrastructure for automotive drivetrain testing. Still, their practical use becomes challenging when the tested production drive units are treated as black-box systems. In the investigated industrial setup, the tested drive units did not provide a speed-control interface that could be used directly on the test bench. This study develops and experimentally evaluates an external speed-control architecture implemented on a rest-bus simulation unit, using reported signals of the electronic control units without additional feedback sensors. The proposed control combines feedback control with disturbance-torque compensation, inertia feedforward based on identified parameters, utilizing the tested drive units’ built-in anti-jerk function for torsional vibration damping. A reduced-order two-mass model and multirate simulations compare local damping with communication-limited external differential-speed feedback. Both approaches attenuated torsional oscillations under nominal conditions, but external damping became less beneficial with additional communication delay. Experimentally, inertia feedforward reduced speed-ramp overshoot from approximately ten per cent to two per cent. During a fast torque ramp, speed deviation decreased from approximately fifty per cent without disturbance feedforward to ten per cent with actual-torque feedforward and to four per cent with setpoint-based feedforward. Enabling anti-jerk damping reduced relative-speed oscillation amplitude by approximately 90 per cent at the investigated operating point. The findings support allocating speed tracking and disturbance compensation to the external controller while utilizing existing embedded functions for torsional damping.