IPM Motor Current Command Generation via Lookup Table Segmentation
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Solution Overview
Problem
Existing electric motor control systems face challenges in accurately generating current output commands, especially at high motor speeds and high torque command inputs, due to limitations in the number of lookup tables and the time-consuming process of creating these tables through experimental measurements.
Innovation Solution
A motor drive control system that includes a processor to determine inverter current commands based on torque commands, DC power bus voltage measurements, and motor speed measurements, using a reduced number of lookup tables and extrapolation methods to interpolate current commands, thereby reducing the need for extensive table interpolation and memory storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a reduced number of lookup tables is used, then memory requirements are reduced, but current command accuracy deteriorates at high motor speeds and high torque commands
Solution Approach 1:
The patent segments the lookup table data into two distinct components: MTPA (Maximum Torque Per Ampere) data and field-weakening data. This segmentation allows each component to be stored separately in memory, reducing the overall memory requirements while maintaining the ability to accurately generate current commands by combining these pre-stored segments through mathematical operations.
Solution Approach 2:
The patent introduces a mathematical transformation approach that operates in a different dimension from traditional lookup table interpolation. By using mathematical operations to combine MTPA and field-weakening data, the system transcends the limitations of direct table lookup and interpolation, achieving accurate current command generation with fewer stored data points.
2Adaptability or versatility
If linear interpolation is used between lookup tables, then current commands can be generated for voltages between table entries, but accuracy deteriorates at high motor speeds and high torque commands
Solution Approach 1:
The patent replaces the mechanical interpolation process with a mathematical transformation system. Instead of linearly interpolating between lookup table entries, the system uses mathematical operations to combine pre-stored MTPA and field-weakening data, providing accurate current commands across the entire voltage range including high motor speeds and high torque conditions where traditional interpolation fails.
3Measurement precision
If extensive lookup tables are created through experimental measurements, then current command accuracy is improved, but the time and effort required for initial testing increases
Solution Approach 1:
The patent extracts only the essential data components needed for accurate current command generation: MTPA data and field-weakening data. By extracting and storing only these critical segments rather than creating extensive lookup tables covering all operating conditions, the system achieves high accuracy while significantly reducing the time and effort required for initial experimental measurements and table population.
Data Source
AI summary
In one aspect, an apparatus includes a motor and inverter configured to provide input power to the motor. The apparatus may also include a data store comprising at least one entry including a first torque command, a first motor speed, and a first DC voltage value, where the first torque command and the first motor speed and the first DC voltage value are associated with a first current output and a processor. The processor receives a torque input, a DC voltage input, and a motor speed input and identifies the current output associated with the torque input, the DC voltage input, and the motor speed input based on another motor speed different than the motor speed input and another DC voltage different than the DC voltage input and the motor speed input, and output the determined current output to cause the inverter to provide the input power to the motor.