A Method for Optimal Clutch Torque Neutralization for Quick Disengagement on Suspended Multispeed Transmissions Using System-Identification and Linear Quadratic Regulation

This paper describes an optimal control method utilizing a Linear Quadratic Regulator (LQR) to control the torque during the gear shift on a multispeed electrified transmission to optimize for clutch actuator durability and shift performance. The dynamic state-space model of the system has been obtained using System-Identification. An LQR controller is formulated to minimize driveline oscillations and transmission-input-torque using the model by manipulating the electrical torque applied by the traction motor at the transmission input. The LQR controller is implemented in a simulation framework wherein the impact of vehicle parameters on the shift quality metrics is also assessed. Subjective and objective requirements are considered in the tuning process for the LQR controller. The LQR controller is utilized to generate profiled torque table calibrations. These calibrations are then deployed onto a production ready Transmission Control Unit and experimentally validated on a Class-8 Heavy Duty vehicle retrofitted with an electrified multispeed transmission. Experimental validation is performed at multiple Gross-Combination-Vehicle Weight (GCVW) configurations. Significant reduction of clutch actuation effort, shift time while maintaining adherence to subjective and objective shift quality metrics has been demonstrated compared to traditional S-Shaped torque profiling.