Open-Loop Voltage Control for Permanent Magnet Machine Sensor Failure
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Solution Overview
Problem
Conventional closed loop current control techniques for multi-phase permanent magnet machines are inadequate when current sensors fail or provide unreliable data, necessitating a method to generate voltage commands independently to maintain vehicle operation in a 'limp home' mode with limited speed and torque.
Innovation Solution
A method for generating synchronous reference frame voltage command signals based on torque commands, angular rotation speed, and DC input voltage, with the option to update voltage commands at different rates depending on selection signals, allowing for modified voltage commands to be computed and adjusted to ensure accurate torque production without relying on current feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If closed loop current control techniques are used, then accurate torque control is achieved, but the system becomes unreliable when current sensors fail
Solution Approach 1:
The patent extracts the current sensor dependency from the control system by developing an open-loop voltage control method that generates voltage commands directly from torque commands, angular rotation speed, and DC input voltage without requiring current feedback. This eliminates the harmful dependency on current sensors while maintaining torque control capability.
Solution Approach 2:
The patent creates a simplified control model that copies the essential torque-producing functionality of the closed-loop system without replicating its sensor-dependent current control architecture. The voltage command generation mimics the torque-current-voltage relationship through mathematical modeling, achieving similar control objectives without the complex sensor feedback loop.
2Manufacturing precision
If voltage commands are updated at high rate, then torque control precision is improved, but computational complexity increases
Solution Approach 1:
The patent implements dynamic voltage command update rates by selecting between different update frequencies (first rate or second rate) based on operating conditions. This allows the system to adapt the computational workload to match the actual torque control requirements, maintaining precision when needed while reducing complexity during steady-state operation.
Solution Approach 2:
The patent changes the update rate parameter of voltage commands based on selection signals that reflect system state. By dynamically adjusting this temporal parameter, the system optimizes the balance between torque control precision and computational resource utilization without requiring complex hardware upgrades.
Data Source
AI summary
Embodiments of the present disclosure relate to methods, systems and apparatus for generating voltage commands used to control operation of a permanent magnet machine.