Synchronous Motor Cogging Torque Compensation via Reference Model
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Solution Overview
Problem
Synchronous motors experience cogging torques due to manufacturing tolerances and load dependency, making it difficult to compensate for these torques effectively, which disrupts smooth operation and control of motor parameters like speed and position.
Innovation Solution
A method that records no-load and load cogging torques for a reference motor, forms a differential cogging torque, and models its spectral components as a function of the operating point to generate a compensation current that counteracts the cogging torque, allowing for type-specific, load-dependent compensation without requiring individual motor testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cogging torque compensation is performed for each individual motor, then compensation precision is improved, but device complexity and costs increase
Solution Approach 1:
The cogging torque is segmented into two distinct components: a load-independent component (present at zero load) and a load-dependent component (varying with load). This segmentation allows different compensation strategies to be applied to each component, reducing overall system complexity while maintaining precision.
Solution Approach 2:
The compensation approach changes parameters by measuring cogging torque at multiple load conditions (including zero load) and using spectral analysis to identify load-dependent variations. This parameter-based differentiation enables a unified compensation model to work across multiple motors without requiring individual calibration for each motor.
2Measurement precision
If individual motor testing is performed for cogging torque compensation, then compensation accuracy is improved, but productivity decreases
Solution Approach 1:
A universal compensation model is developed that can be applied to all motors of a specific type without requiring individual testing. The model captures load-dependent cogging torque characteristics that are common across the motor type, enabling one measurement campaign to benefit multiple motors and significantly improving productivity.
Solution Approach 2:
The compensation data obtained from measuring one reference motor is copied and applied to other identical motors. By using spectral analysis to identify the load-dependent component, the system creates a reusable compensation model that can be transferred across the motor population, eliminating the need for repetitive individual testing.
3Reliability
If load-dependent cogging torque components are measured for every motor, then compensation reliability is improved, but loss of time increases
Solution Approach 1:
The load-dependent cogging torque characteristics are determined in advance through a preliminary measurement on a reference motor. This preliminary action captures the essential parameters needed for compensation, allowing rapid application to other motors without repeating the time-consuming measurement process, thus maintaining reliability while reducing time loss.
4Ease of operation
If simple compensation methods are used, then ease of operation is improved, but compensation precision deteriorates
Solution Approach 1:
Spectral analysis serves as an intermediary tool that bridges the gap between simple measurement procedures and precise compensation. By using frequency domain analysis to separate load-dependent and load-independent components, the system achieves high precision without requiring complex individual motor testing procedures, thus maintaining ease of operation.
Data Source
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AI summary
The invention relates to a method for compensating cogging torques of identical synchronous motors (1), each comprising a stator (5) and a rotor (7). For a reference motor (2) of the synchronous motors (1), a no-load cogging torque is measured as a function of the rotor position of the rotor (7), and for various operating points, a load cogging torque is measured as a function of the rotor position. For each measured load cogging torque of the reference motor (2), a differential cogging torque is calculated by subtracting the measured no-load cogging torque of the reference motor (2) from the load cogging torque. Furthermore, an operating-point-dependent spectral component of the differential cogging torque is determined, and a model function of the spectral component is generated, which models the spectral component as a function of the operating point.For each synchronous motor (1), during operation in a predefinable first operating range at an instantaneous operating point, a first compensation current is superimposed on a target current of the synchronous motor (1), which generates a compensation torque that compensates a cogging torque with the value of the model function at the instantaneous operating point.