Fail-safe Traction Drive Control via Dual Sensorless Estimators
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Solution Overview
Problem
Position sensorless electric traction drive systems in electric vehicles face disruptions when the mechanical wired connection to the motor windings' neutral point is lost due to wear and tear, leading to motor control disturbances and potential vehicle stalling.
Innovation Solution
A method and apparatus utilizing a limp home controller with dual sensorless speed and position estimators, one using a pulse width modulated signal modification method and another employing high frequency injection, to generate rotor position and speed signals, ensuring continuous operation even without neutral point access signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If pulse width modulated signal modification method is used for sensorless operation, then fast dynamic performance is achieved, but the system becomes vulnerable to neutral point connection loss
Solution Approach 1:
The system performs preliminary actions by implementing a supervisory controller that continuously monitors neutral point connection status and pre-prepares alternative sensorless control methods. When neutral point access is available, the system uses PWM modification method for fast dynamic performance. When connection is lost, the supervisory controller seamlessly switches to backup sensorless methods that don't require neutral point access, preventing control failure before it occurs.
Solution Approach 2:
The invention provides beforehand cushioning by implementing redundant sensorless control algorithms as backup mechanisms. The supervisory controller maintains multiple sensorless estimation methods ready to compensate for potential neutral point connection failures. This cushioning ensures that even if the primary PWM-based sensorless control fails due to connection loss, the system can transition to alternative methods, cushioning against control instability.
2Productivity
If mechanical wired connection to neutral point is used, then sensorless control with fast dynamic performance is enabled, but the connection may be lost due to wear and tear
Solution Approach 1:
The supervisory controller acts as an intermediary between the neutral point connection and the motor control system. It continuously monitors the status of the neutral point connection and mediates the control signal flow accordingly. When the connection is healthy, it enables PWM-based sensorless control for fast performance. When connection degradation or loss is detected, it intermediates by switching to backup sensorless methods that don't depend on the neutral point connection, maintaining control continuity.
Solution Approach 2:
The system applies parameter changes by dynamically adjusting control parameters based on neutral point connection status. When connection is reliable, it uses PWM modification parameters optimized for fast dynamic response. When connection reliability deteriorates, the supervisory controller changes control parameters to utilize alternative sensorless estimation methods with different characteristics that are more robust to connection issues, thereby adapting to the changing reliability conditions.
3Reliability
If dual sensorless estimation methods are implemented, then fail-safe operation is achieved, but device complexity increases
Solution Approach 1:
The control system is segmented into distinct functional modules: a supervisory controller that monitors neutral point connection status, a primary sensorless control module using PWM modification method, and backup sensorless control modules using alternative estimation methods. Each segment has a specific function, and the supervisory controller selectively activates appropriate segments based on connection status. This segmentation manages complexity by organizing functions into manageable, independently operable units with clear activation criteria.
Solution Approach 2:
The system implements dynamics by making the controller configuration adaptive rather than static. The supervisory controller dynamically determines which sensorless estimation method to use based on real-time neutral point connection status. This dynamic switching capability allows the system to optimize between fast performance (when connection is good) and reliability (when connection is poor) without requiring all complex functionality to be simultaneously active, thereby managing overall device complexity through conditional activation.
Data Source
AI summary
A method for operation of an internal permanent magnet motor having a rotor includes determining whether a neutral point access signal is received from the rotor and operating the internal permanent magnet motor using sensorless signals corresponding to a rotor position and a rotor speed derived by a first sensorless signal estimation method when the neutral point access signal is received, wherein the first sensorless signal estimation method utilizes the neutral point access signal to generate the rotor position and the rotor speed. The method further includes operating the internal permanent magnet motor using sensorless signals corresponding to a rotor position and a rotor speed derived by a second sensorless signal estimation method when the neutral point access signal is not received, wherein the second sensorless signal estimation method does not utilize the neutral point access signal to generate the rotor position and the rotor speed.