Torque Estimation in Electric Motor Drives Using Dynamic Flux
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing motor control systems face inaccuracies in actual torque estimation due to variations in rotor flux with temperature and between individual motors, leading to reduced control precision and efficiency in hybrid systems.
Innovation Solution
A control device using a flux estimator to determine rotor flux with dynamic parameters, including quadrature axis voltage, direct and quadrature axis currents, angular velocity, stator resistance, and inductance, to improve actual torque estimation accuracy, and a method to adjust reference torque for better correspondence between input and actual torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional torque estimation methods are used, then the control system is simple, but the torque estimation accuracy is low due to rotor flux variations with temperature and between individual motors
Solution Approach 1:
The patent applies dynamics by making the rotor flux estimation adaptive rather than static. The flux estimator dynamically adjusts the rotor flux value based on real-time operating conditions including temperature variations and motor-specific characteristics. This dynamic adaptation resolves the contradiction by enabling accurate torque estimation across varying conditions without requiring a completely complex reconfiguration of the control system.
Solution Approach 2:
The patent changes the parameter being estimated from a fixed value to a dynamically calculated value. By introducing a flux estimator that computes rotor flux based on multiple input parameters (temperature, operating conditions, motor characteristics), the system achieves higher torque estimation accuracy. This parameter change approach allows the system to adapt to temperature variations and individual motor differences while maintaining a manageable control architecture.
2Measurement precision
If rotor flux is kept constant, then the control algorithm is simple, but torque control precision deteriorates due to temperature-induced flux variations
Solution Approach 1:
The patent implements feedback by continuously monitoring operating conditions and using this information to adjust the rotor flux estimation. The flux estimator receives feedback about temperature and motor state, then adjusts the flux value accordingly. This feedback mechanism enables the system to compensate for temperature-induced flux variations, maintaining precise torque control across different thermal conditions.
Solution Approach 2:
The patent transforms the static rotor flux assumption into a dynamic estimation process. Instead of keeping flux constant, the system continuously updates the flux value based on current operating conditions. This dynamic approach directly addresses temperature sensitivity by allowing the flux estimation to adapt as temperature changes, thereby maintaining torque control precision throughout the motor's operating range.
3Measurement precision
If individual motor calibration is performed for each motor, then torque estimation accuracy improves, but the complexity of motor configuration and setup increases significantly
Solution Approach 1:
The patent achieves universality by designing a flux estimator that can accommodate multiple motor types and individual variations through a single unified algorithm. Rather than requiring separate calibration procedures for each motor, the estimator uses general motor parameters and operating conditions to adapt to any specific motor instance. This multi-functional approach enables accurate torque estimation across different motors without increasing configuration complexity.
Solution Approach 2:
The patent implements self-service by enabling the control system to automatically adapt to individual motor characteristics without requiring manual calibration. The flux estimator uses readily available operating parameters and motor data to self-adjust the flux estimation for each specific motor. This self-adjusting capability eliminates the need for time-consuming individual calibration procedures while maintaining high torque estimation accuracy.
Data Source
Figure 1
AI summary
It is presented a control device for driving an electric motor, wherein a drive control signal for the electric motor is arranged to be determined using a calculated rotor flux. A direct quadrature, dq, coordinate system relating to a rotor of the electric motor is used. The control device comprises a flux estimator arranged to determine the calculated rotor flux using a quadrature axis voltage, a measured direct axis current, a measured quadrature axis current, an angular velocity, stator resistance and a direct axis inductance and an actual torque calculator arranged to obtain an actual torque estimation using the calculated rotor flux, the measured direct axis current and the measured quadrature axis current. A corresponding method is also presented.