Torque Ripple Cancellation with Voltage Saturation Prevention
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Solution Overview
Problem
Existing torque ripple cancellation methods in electric motor control systems, particularly for EPS applications, rely on offline lookup tables that do not account for real-time operating conditions, leading to suboptimal performance and high memory usage due to open-loop approaches and voltage saturation issues.
Innovation Solution
A closed-loop system with a ramp-down command generator module that adjusts torque ripple cancellation commands based on a voltage saturation indicator, generated from supply voltage and motor voltage commands, to proactively limit torque ripple cancellation and prevent voltage saturation, using both feedforward and feedback voltage signals for accurate scaling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an offline lookup table approach is used for torque ripple cancellation, then the implementation is simple, but the performance is suboptimal and memory usage is high
Solution Approach 1:
The patent implements a closed-loop feedback mechanism where the torque ripple cancellation command is continuously adjusted based on actual motor operating conditions. The current regulator monitors real-time currents and dynamically modifies the cancellation command, replacing the open-loop lookup table approach with adaptive feedback control that optimizes performance for each operating point.
Solution Approach 2:
The system transitions from a static lookup table to a dynamic control approach where the torque ripple cancellation command is continuously adapted based on real-time operating conditions. The cancellation command varies dynamically with motor speed, torque, and current state, enabling optimal performance across the entire operating range rather than relying on pre-calculated fixed values.
2Reliability
If a pulsating voltage command is used for torque ripple cancellation, then torque ripple is reduced, but voltage saturation occurs degrading system performance
Solution Approach 1:
The system proactively prevents voltage saturation by monitoring the voltage command magnitude and applying preliminary counter-actions. When the pulsating voltage command for torque ripple cancellation approaches the supply voltage limit, the system automatically reduces the cancellation command amplitude before saturation occurs, ensuring the total voltage command remains within available supply voltage bounds.
Solution Approach 2:
The system dynamically adjusts the amplitude parameter of the torque ripple cancellation voltage command based on the operating point and available voltage headroom. By changing the cancellation voltage amplitude parameter in real-time according to motor speed, torque, and supply voltage availability, the system maintains effective torque ripple cancellation while preventing voltage saturation.
3Reliability
If the torque ripple cancellation command is increased, then torque ripple is reduced, but the system approaches voltage saturation limit
Solution Approach 1:
The system implements dynamic adaptation of the torque ripple cancellation command based on real-time voltage headroom assessment. The cancellation command amplitude is continuously adjusted according to the difference between available supply voltage and voltage required for torque production, enabling maximum torque ripple cancellation effectiveness while maintaining sufficient voltage headroom for operational flexibility.
Data Source
AI summary
A system for reducing a torque ripple cancellation command is provided and includes a current regulator that provides motor voltage commands to a motor, and a torque ripple cancellation module that generates a torque ripple cancellation command based on input currents to the current regulator. A ramp-down command generator module that provides a ramp-down command to the torque ripple cancellation module is also provided. The ramp-down command is based on a voltage saturation indicator, and a voltage saturation indicator generator that generates a voltage saturation indicator signal. The voltage saturation indicator signal is based on a supply voltage signal and a motor voltage command.