Vehicle Motor Torque Control for Startup and Braking Judder
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Solution Overview
Problem
Electric vehicles experience juddering during startup or braking due to torsional vibrations in the transmission system, leading to reduced service life and noise issues, with existing torque control methods failing to effectively suppress these vibrations due to signal delays and interference in wheel speed signals.
Innovation Solution
A torque control system for vehicle motors using a double closed-loop linear observer to synchronize estimated angular velocities with actual velocities, compensating for signal delays through delay modules and calculating compensated torque based on these synchronized values to improve real-time performance and suppress juddering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a filter is used to extract juddering of the motor at rotational speed, then limited juddering suppression may be implemented, but the filter cannot effectively extract the juddering caused by gear clearance
Solution Approach 1:
The patent introduces wheel speed signal as an intermediary to indirectly observe motor juddering. Instead of directly filtering motor speed signal, the system uses wheel speed comparison method where wheel speed signal serves as a mediator to detect and compensate for juddering caused by gear clearance, resolving the limitation of direct filtering approaches
Solution Approach 2:
The patent replaces mechanical signal processing (direct motor speed filtering) with a computational approach using wheel speed signal comparison. The system substitutes the mechanical/direct measurement path with an indirect computational method that compares wheel speed with expected wheel speed to extract juddering components, achieving better effectiveness without increased hardware complexity
2Reliability
If the wheel speed comparison method is used for juddering suppression at zero crossing point of motor torque, then targeted suppression may be achieved, but the wheel speed signal has signal delay and low update rate
Solution Approach 1:
The patent applies preliminary action by using predicted wheel speed signal to compensate for the inherent delay in wheel speed measurement. The system calculates expected wheel speed based on motor speed and transmission ratio, then uses this predicted value as a reference for comparison, effectively compensating for the time delay before it affects control accuracy
Solution Approach 2:
The patent implements feedback by continuously comparing actual wheel speed with predicted wheel speed and using the deviation to calculate compensated motor torque. The system feeds back the juddering extraction result in real-time, adjusting motor torque to counteract detected vibrations, thereby reducing the practical impact of signal delay through continuous correction
3Productivity
If directly obtained wheel speed signal is used for torque compensation, then the compensated torque may be calculated, but the signal is susceptible to interference from road conditions causing torque fluctuation
Solution Approach 1:
The patent extracts only the relevant juddering information from the wheel speed signal by comparing it with predicted wheel speed. Instead of using the raw wheel speed signal directly for control, the system extracts the deviation component that represents juddering, separating this useful information from the noise caused by road conditions and other disturbances
Solution Approach 2:
The patent introduces predicted wheel speed as an intermediary reference that is not susceptible to road condition interference. By comparing actual wheel speed with this clean predicted reference, the system obtains a juddering signal that is free from road condition noise, enabling accurate torque compensation without the harmful effects of direct wheel speed signal usage
Data Source
Figure 1
AI summary
The disclosure provides a torque control system for a vehicle motor which includes: a target torque obtaining unit configured to obtain a target torque TRef of the motor that is associated with a vehicle pedal parameter; a compensated torque calculation unit configured to calculate a compensated torque TDmp of the motor; and a theoretical torque calculation unit configured to calculate a theoretical torque TCmd of the motor based on the target torque TRef of the motor and the compensated torque TDmp of the motor, the compensated torque calculation unit including an angular velocity acquisition module which is configured to obtain an actual angular velocity ωm of the motor that is sampled at a first frequency and an actual angular velocity ωl of a wheel that is sampled at a second frequency less than the first frequency and converted to a motor side.