Electric Motor Torque Control With Safe Current Error Fallback
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Solution Overview
Problem
Existing electric motor control systems in vehicles face challenges in maintaining control due to divergence between target and actual electric current, leading to potential loss of control and safety risks, especially under varying operating conditions.
Innovation Solution
A control unit that determines a safety target torque limit based on a predetermined percentage of the target torque, replacing the target torque with a safety target torque when divergence is detected, to ensure motor vehicle controllability without complete shutdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the target torque is limited according to the characteristic curve to maximise performance, then the power and speed of the electric motor are improved, but the risk of control loss increases due to error divergence between target and actual current
Solution Approach 1:
The control unit continuously monitors the actual current and compares it with the target current to calculate the error. This feedback mechanism allows the system to detect when the error exceeds the threshold and automatically reduces the target torque accordingly, maintaining control reliability while maximizing performance during normal operation
Solution Approach 2:
The target torque is dynamically adjusted based on real-time error conditions. When the error between target and actual current exceeds the threshold, the control unit immediately reduces the target torque to a safe level, and can progressively increase it again as conditions improve, creating a dynamic response that adapts to changing operational states
2Reliability
If speed limiter or stop commands are issued to maintain safety during error divergence, then the control reliability is improved, but the ease of operation deteriorates due to forced vehicle shutdown
Solution Approach 1:
Instead of completely shutting down the motor when error divergence occurs, the control unit applies a partial action by reducing the target torque to a safe level that maintains vehicle operability. This partial correction is sufficient to restore control stability without requiring full system shutdown, allowing the driver to continue operating the vehicle safely
Solution Approach 2:
The control system prepares for potential control issues by having a pre-defined safe torque level ready to be applied immediately when error exceeds the threshold. This beforehand preparation allows for smooth transition to a safe operating state without abrupt shutdowns, cushioning the impact on vehicle operability
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A process for controlling an electric motor (4) includes determining a target torque (T*) to be delivered by the electric motor (4), associating the target torque (T*) with a control target (i*d, i*q) for a control input of the electric motor (4) according to a mapping (101) between the target torque (T*) and the control target (i*d, i*q), acquire a feedback signal of the control input, controlling the electric motor (4) with an error between the feedback signal and the control target, identifying a critical condition where the error diverges, determining a safety control target corresponding to a safety target torque according to the mapping (101), where the safety target torque is reduced relative to the target torque, and replacing the error when the critical condition is identified with a safety error between the feedback signal and the safety control target.