Torque Sensor Calibration for Variable Speed Drive Transients
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Solution Overview
Problem
Conventional variable speed drives for asynchronous electric motors face challenges in accurately measuring dynamic torque, leading to limited reliance on torque measurement for precise control, especially during transient phases, which affects the motor's ability to reach desired accelerations.
Innovation Solution
A method involving a predetermined torque sequence is performed by the electric motor, measured by a torque sensor, and compared to determine torque sensor transfer function parameters such as delay, gain, and bandwidth, enhancing dynamic torque measurement precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a torque sensor is used to measure dynamic torque in a variable speed drive, then torque measurement capability is provided, but measurement precision is insufficient during transient phases due to sensor delay and bandwidth limitations
Solution Approach 1:
The system performs preliminary identification of torque sensor transfer function parameters (delay, gain, bandwidth) by applying a predetermined torque sequence before normal operation. This preliminary characterization enables the system to compensate for measurement delays and inaccuracies during transient phases, improving torque measurement precision without adding physical hardware.
Solution Approach 2:
The system implements feedback by comparing the predetermined torque sequence with the measured torque sequence from the sensor. This comparison enables the system to identify and characterize the torque sensor's transfer function parameters, which are then used to compensate for measurement delays and improve the accuracy of dynamic torque measurements during motor control.
2Manufacturing precision
If torque measurement is relied upon for precise control during transient phases, then control precision is improved, but the measurement reliability is insufficient due to slow sensor response
Solution Approach 1:
The system performs preliminary identification of torque sensor transfer function parameters (delay, gain, bandwidth) by applying a predetermined torque sequence before normal operation. This preliminary characterization enables the system to compensate for measurement delays and inaccuracies during transient phases, improving torque measurement precision without adding physical hardware.
Solution Approach 2:
The system changes the parameters used for torque control by incorporating identified transfer function parameters (delay, gain, bandwidth) into the control algorithm. This allows the system to adjust for sensor limitations and improve measurement reliability during transient phases, enabling more precise control without relying solely on raw sensor data.
3Measurement precision
If the torque sensor transfer function parameters are determined through comparison of predetermined and measured torque sequences, then measurement precision is improved, but the device complexity increases
Solution Approach 1:
The system performs preliminary identification of torque sensor transfer function parameters (delay, gain, bandwidth) by applying a predetermined torque sequence before normal operation. This preliminary characterization enables the system to compensate for measurement delays and inaccuracies during transient phases, improving torque measurement precision without adding physical hardware.
Solution Approach 2:
The system performs self-identification of the torque sensor's transfer function parameters by comparing its own predetermined torque sequence with the measured sequence from the sensor. This self-characterization process eliminates the need for external calibration equipment or complex additional hardware, improving measurement precision through software-based identification.
Data Source
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AI summary
Examples include a method for controlling a variable speed drive of an electric motor. The variable speed drive is connected to a torque sensor for sensing a torque supplied by the electric motor. The method comprises performing, by the electric motor, a predetermined torque sequence. The method also comprises measuring, by the torque sensor, a measured torque sequence corresponding to the predetermined torque sequence, and comparing the predetermined torque sequence and the measured torque sequence. As a result of the comparison, one or more torque sensor transfer function parameters are determined.