Electric Motor Current Control Using Real-Time L/R Gain Estimation
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Solution Overview
Problem
Existing motor control devices require multiple tables for proportional and integration gains based on current and temperature, limiting accuracy due to their lack of correspondence with motor inductance and resistance, leading to suboptimal current control.
Innovation Solution
A control device and method that estimates motor inductance and resistance using a voltage equation model, determining proportional and integration gains for current control based on these estimates, thereby improving control accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple proportional gain tables and integration gain tables are created for different currents and temperatures, then the control device can cover various operating conditions, but the device complexity increases and the accuracy is limited because the tables do not exactly correspond to inductance and resistance
Solution Approach 1:
The patent changes the parameter basis from discrete current and temperature tables to continuous inductance and resistance parameters. By estimating L and R in real-time and using them to calculate proportional and integration gains, the system achieves accurate current control without requiring multiple pre-defined tables for different operating conditions.
Solution Approach 2:
The patent creates a virtual model of the motor by estimating inductance and resistance parameters through current observation. This estimated parameter model replaces the need for multiple physical gain tables, allowing the system to adapt to changing conditions through parameter estimation rather than table lookup.
2Ease of manufacture
If proportional gain tables and integration gain tables are used based on current and temperature, then the control can be simplified, but the manufacturing precision is limited because the tables do not exactly correspond to inductance and resistance values
Solution Approach 1:
The patent replaces the mechanical table-lookup approach with an electronic parameter estimation and calculation system. By substituting the discrete table-based method with continuous parameter estimation and mathematical calculation, the system achieves both simplicity and precision simultaneously.
3Reliability
If gain tables are prepared for each control target (motor and inverter individually), then the control can be optimized for specific targets, but the adaptability decreases when dealing with different motor-inverter combinations
Solution Approach 1:
The patent creates a universal control method that works across different motor-inverter combinations by estimating inductance and resistance parameters. The parameter estimation approach is target-agnostic and can adapt to any motor-inverter pair, providing both optimization and versatility simultaneously.
Data Source
AI summary
A control device for an electric motor includes a control circuit that controls an operation of an inverter circuit on the basis of a voltage command value corresponding to a difference between a current command value calculated on the basis of the position of a rotor of the electric motor, and a current flowing through the electric motor. A current estimation unit estimates the current flowing through the electric motor by substituting the voltage command value, a parameter unique to the electric motor, and a rotational speed calculated on the basis of the position of the rotor into a voltage equation serving as a model of the electric motor. An LR estimation unit estimates an inductance and a resistance of the electric motor serving as parameters on the basis of the difference between the current obtained by a current acquisition unit and the current estimated by the current estimation unit.