Jerk-Limited Motor Speed Profiling Under Torque Slew Limits
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Solution Overview
Problem
Conventional hybrid powertrain speed control techniques suffer from torque slew limits and insufficient convergence when the target speed is changing, particularly due to limitations in belt tension hardware and the use of conventional non-electrically variable transmissions.
Innovation Solution
A software-based speed control system that utilizes jerk-based profiling to determine open-loop acceleration commands and profiled target speeds, combined with closed-loop torque adjustments, to improve vehicle responsiveness and achieve smooth, quick convergence to dynamically changing target speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional speed control techniques are used, then the system is simple to implement, but the convergence to target speed is slow and insufficient
Solution Approach 1:
The patent implements dynamics by making the control profile adaptive rather than static. The number of loops to converge (LTC) dynamically adjusts based on the speed difference between target and current state. This dynamic adjustment allows the system to converge faster when the speed difference is large while maintaining stability when the difference is small, resolving the contradiction between convergence speed and control complexity.
2Reliability
If torque slew limits are imposed, then hardware limitations are respected, but vehicle responsiveness to target speed changes is reduced
Solution Approach 1:
The patent applies parameter changes by modifying the torque command through jerk-based profiling. Instead of directly applying torque commands that may exceed slew limits, the system calculates a profiled torque that respects the maximum jerk rate of change. The acceleration command is adjusted using the formula: A = (Ntgt - Nprof_prev) / LTC, ensuring that torque changes remain within hardware limitations while maintaining responsiveness through optimized control parameters.
3Speed
If aggressive target speed changes are commanded, then vehicle performance is improved, but torque slew limits are exceeded causing instability
Solution Approach 1:
The patent implements feedback by continuously monitoring the difference between target speed and profiled speed, and using this information to adjust the acceleration command. The closed-loop feedback mechanism ensures that if the target speed changes aggressively, the system calculates an appropriate number of loops to converge (LTC) to prevent exceeding torque slew limits. This feedback loop maintains stability while allowing aggressive target speed changes: A = (Ntgt - Nprof_prev) / LTC.
Data Source
AI summary
Speed control techniques include, based on a set of target speed inputs indicative a target speed for an electric motor, determining a set of profiling inputs including (i) the target speed and (ii) a set of desired acceleration calibrations, performing jerk-based profiling based on the set of profiling inputs to determine at least one of an open-loop acceleration command and a profiled target speed, determining a closed-loop torque adjustment based on the profiled target speed and a measured speed of the electric motor, determining an electric motor torque command based on the open-loop acceleration command and the closed-loop torque adjustment, and controlling the electric motor based on the respective electric motor torque command to improve vehicle responsiveness in reaching the target speed.