Electric Vehicle Torque Control with Feedforward Vibration Suppression
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Solution Overview
Problem
Existing control systems for electric vehicles face instability and insufficient vibration suppression due to lag times in computation, detection, and torque response, leading to divergence and inadequate vibration reduction when feedback gains are lowered to prevent divergence.
Innovation Solution
A device for controlling electric vehicles that includes a feedforward computation unit and a motor torque control unit, utilizing a vehicle model and drive shaft torsional angular velocity feedback model to compute a first torque target value, which reduces drive shaft torsional vibrations by accounting for system lags and backlash characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If feedback gain is increased to improve vibration suppression, then vibration suppression function is improved, but control system stability deteriorates due to lag times causing divergence
Solution Approach 1:
The patent applies feedforward computation that calculates torque target values in advance based on the torque instruction value and drive shaft torsional angular velocity, before the actual torque application occurs. This preliminary action allows the system to compensate for vibrations proactively rather than reactively, avoiding the stability issues caused by high feedback gains while still achieving effective vibration suppression.
Solution Approach 2:
The patent implements a feedback mechanism where the drive shaft torsional angular velocity is measured and fed back to the feedforward computation unit. This feedback is used to adjust the torque target value dynamically, allowing the system to adapt to actual vibrations while maintaining stability through the feedforward control framework.
2Stability of the object's composition
If feedback gain is decreased to maintain control system stability, then control system stability is improved, but vibration suppression function deteriorates
Solution Approach 1:
By computing the torque target value in advance using feedforward computation that incorporates drive shaft torsional angular velocity information, the system achieves effective vibration suppression without relying on high feedback gains. This preliminary action enables low feedback gains to be used while maintaining both stability and vibration suppression performance.
3Speed
If lag times in computation and detection are reduced to improve control response, then control response speed is improved, but system complexity increases
Solution Approach 1:
The feedforward computation unit performs calculations in advance to determine torque target values, which reduces the need for rapid real-time computations during torque application. This approach improves effective control response speed without significantly increasing system complexity, as the computation is distributed over time rather than concentrated in real-time critical paths.
Data Source
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AI summary
A device for controlling an electric vehicle includes: a feedforward computation unit that is configured to input a motor torque instruction value and compute a first torque target value by feedforward computation; and a motor torque control unit that is configured to control a motor torque according to the first torque target value. The feedforward computation unit includes: a vehicle model which is configured to input the motor torque instruction value to model a characteristic from the motor torque to a drive shaft torsional angular velocity; and a drive shaft torsional angular velocity feedback model which is configured to feed back the drive shaft torsional angular velocity output from the vehicle model to the motor torque instruction value to compute the first torque target value.