Limp Home Controller for Electric Motor Resolver Failure
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Solution Overview
Problem
Electric motor systems in electric or hybrid vehicles face operational challenges when a resolver fails, as it cannot provide necessary position and speed signals for motor control, leading to potential vehicle stall conditions.
Innovation Solution
A limp home controller with a sensorless speed and position estimator and signal selector is implemented, allowing the system to generate and use sensorless rotor position and speed signals when the resolver fails, ensuring continuous operation by determining resolver failure and switching between resolver and sensorless signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resolver is used to generate rotor position and speed signals, then the electric motor system can provide accurate position and speed signals for control, but the system reliability deteriorates when the resolver fails
Solution Approach 1:
The patent changes the operational parameters by switching between two different signal generation methods: resolver-based signals under normal conditions and sensorless estimator-based signals when the resolver fails. This parameter change allows the system to adapt to different operational states and maintain reliability while preserving measurement precision through the appropriate method
Solution Approach 2:
The patent introduces a signal selector as an intermediary component that receives both resolver signals and sensorless estimator signals, determines which source is reliable, and selects the appropriate signals for motor control. This intermediary mechanism resolves the contradiction by automatically switching between signal sources based on resolver health status
2Ease of operation
If the system operates using resolver signals, then accurate motor control is achieved, but the system cannot continue operation when the resolver fails
Solution Approach 1:
The patent implements preliminary action by pre-establishing a sensorless estimator that can generate rotor position and speed signals independently of the resolver. This backup capability is prepared in advance and can be activated immediately when the resolver fails, ensuring continuous operation without interruption
Solution Approach 2:
The patent applies beforehand cushioning by creating a redundant signal generation path through the sensorless estimator. This cushioning mechanism ensures that when the primary resolver-based signal path fails, the system can transition to the backup path and maintain operational duration without complete system failure
3Reliability
If a backup sensorless estimation system is added, then system reliability improves during resolver failure, but device complexity increases
Solution Approach 1:
The patent applies universality by designing the sensorless estimator and signal selector to work within the existing controller architecture. The sensorless estimator uses the same motor parameters and electrical measurements already available in the system, and the signal selector integrates with the existing control signal paths, thereby improving reliability while minimizing additional complexity
Solution Approach 2:
The patent merges the sensorless estimation functionality with the existing resolver-based control system through a unified signal selection mechanism. Both signal sources feed into a common control pathway, and the signal selector integrates both sources into a single coherent control signal path, reducing the overall system complexity compared to completely separate control systems
Data Source
AI summary
Methods and apparatus are provided for a limp home operational mode for an electric motor system. The method includes determining whether a resolver has failed. When the resolver has not failed, operation of the electric motor system uses resolver signals. When the resolver fails, operation of the electric motor system uses sensorless rotor position and rotor speed signals.