Motor Speed and Position Backup Using Sensorless Resolver Fallback
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Solution Overview
Problem
Existing systems for determining the speed and position of electric motors, particularly in vehicles, face challenges in accuracy and precision, especially when resolvers are unavailable or malfunctioning, necessitating a reliable backup system for sensorless operation.
Innovation Solution
A backup system that calculates motor speed and position using a sensorless method based on metrics available when the resolver is unavailable, involving a cascaded arrangement of position and sensorless systems, including observers for angle error and flux calculations, and an initialization mode to prepare for sensorless operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a resolver is used to determine speed and position of the electric motor, then measurement precision is improved, but reliability deteriorates when the resolver becomes unavailable or malfunctions
Solution Approach 1:
The system changes the measurement parameters by switching from resolver-based measurements to sensorless control parameters (voltage and current measurements) when the resolver becomes unavailable. This allows the system to continue determining speed and position using alternative electrical parameters available from the motor itself.
Solution Approach 2:
The sensorless control system creates a virtual model (copy) of the motor's position and speed by calculating these parameters from voltage and current measurements, rather than directly measuring them with physical sensors. This computational copy enables continued operation without the physical resolver.
2Reliability
If a backup sensorless system is implemented, then reliability is improved when resolver is unavailable, but device complexity increases
Solution Approach 1:
The control system is designed with multi-functionality to operate in multiple modes: normal resolver-based control and backup sensorless control. This universal design allows the same system to perform different functions depending on resolver availability, reducing the need for completely separate backup hardware.
Solution Approach 2:
The microcontroller serves as an intermediary that manages the transition between resolver-based and sensorless control modes. It monitors resolver status and coordinates the switch to alternative measurement methods, simplifying the overall system architecture by centralizing control logic.
3Reliability
If sensorless control calculations are performed continuously, then reliability is improved, but use of energy increases due to additional processor load
Solution Approach 1:
The system performs sensorless control calculations periodically or on-demand rather than continuously. The microcontroller monitors resolver availability and only activates the more computationally intensive sensorless calculations when needed, such as during mode transitions or when resolver data becomes unavailable.
Solution Approach 2:
The system performs preliminary checks to determine whether sensorless control is needed before executing the full calculation routine. By first checking resolver availability and only then activating backup calculations, the system minimizes unnecessary processor activity and energy consumption.
Data Source
AI summary
A method and system are contemplated for determining a final speed and position of a motor used in an electric vehicle. The final speed and position is calculated as a function of a sensed position when a resolver of a position system is available and as a function of a sensorless position when the resolver is unavailable.