Sensorless Motor Control Stall Detection via Acceleration
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Solution Overview
Problem
Existing sensorless position algorithms for electric motors are ineffective in detecting stall conditions due to high noise levels in estimated velocity signals at low speeds, making it difficult to reliably determine if the motor has locked or stalled.
Innovation Solution
A control system that monitors electrical voltages and currents to determine the rotational position of the motor, using parameters like estimated velocity, speed, acceleration, and demanded currents to detect stall conditions without additional hardware, and implements a stall detection algorithm that repeatedly checks for these parameters within predetermined ranges to confirm a stall occurrence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless position algorithms are used to determine motor position, then hardware complexity is reduced, but measurement precision deteriorates at low speeds due to high noise levels in estimated velocity signals
Solution Approach 1:
The patent changes the parameter being monitored from estimated velocity to estimated acceleration. By using acceleration instead of velocity, the system achieves reliable stall detection without the high noise levels that plague velocity measurements at low speeds, thus maintaining measurement precision while using sensorless algorithms.
Solution Approach 2:
The patent introduces an intermediary parameter (acceleration) that mediates between the noisy velocity signal and the stall detection requirement. By deriving acceleration from velocity and using it as the primary detection parameter, the system filters out the high-frequency noise while preserving the stall condition information.
2Difficulty of detecting and measuring
If estimated velocity signal is used for stall detection, then detection capability is simplified, but reliability deteriorates due to excessively high noise levels
Solution Approach 1:
The patent changes the detection parameter from velocity to acceleration. This parameter change fundamentally resolves the reliability issue because acceleration remains measurable and meaningful even when velocity noise is extreme, allowing reliable threshold-based stall detection.
Solution Approach 2:
The patent substitutes the direct velocity-based detection mechanism with an acceleration-based mechanism. This substitution replaces a flawed detection approach with a more robust one that is insensitive to the noise problems affecting velocity measurements.
3Reliability
If hall sensors are used to monitor rotational position, then stall detection reliability is improved, but device complexity increases
Solution Approach 1:
The patent enables the motor control system to perform stall detection using its own existing sensorless position algorithm and current measurements. The system serves itself by utilizing its operational data (voltages and currents) to detect stalls, eliminating the need for separate hall sensors or additional detection hardware.
Solution Approach 2:
The patent makes the sensorless position algorithm multi-functional by using it for both position determination and stall detection. By monitoring parameters generated during normal operation (estimated acceleration), the system performs dual functions without requiring additional dedicated detection hardware.
Data Source
AI summary
A control system for an electric motor comprises processing means arranged to perform a control process which includes monitoring electrical voltages applied to the motor and electrical currents in the motor, and determining from them the rotational position of the motor. The system is further arranged to monitor at least one parameter of the control process thereby to detect a stall condition of the motor.