Inverter Temperature Estimation for Electric Power Steering
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Solution Overview
Problem
Existing rotary electrical machine control systems struggle to accurately estimate inverter temperatures, especially when multiple systems are used, and do not provide clear guidance on sensor placement for temperature estimation.
Innovation Solution
A rotary electrical machine control apparatus is designed with multiple inverters and a temperature detection element, where the thermistor is placed closer to the inverter with lower on-resistance, allowing for accurate estimation of inverter temperatures by detecting a base temperature and temperature change amounts, and adjusting parameters for single system operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor is placed to detect base temperature for inverter temperature estimation, then temperature estimation can be performed, but placement position affects estimation accuracy due to different on-resistances of switching elements
Solution Approach 1:
The patent applies local quality by placing the temperature sensor in a specific location closer to the first inverter (with lower on-resistance switching elements) rather than using a uniform placement approach. This localized placement strategy accounts for the different thermal characteristics of each inverter system, enabling more accurate temperature estimation for the first inverter while acknowledging that each inverter's thermal environment is unique and requires tailored sensor positioning.
2Reliability
If multiple inverters are used in a rotary electrical machine system, then system reliability is improved, but temperature estimation becomes more difficult due to different on-resistances
Solution Approach 1:
The patent applies segmentation by treating each inverter system as a separate entity with its own temperature estimation characteristics. Instead of attempting to create a single unified temperature estimation model for multiple inverters, the system segments the temperature detection approach by placing sensors and creating estimation models specific to each inverter's thermal characteristics, thereby simplifying the overall detection complexity while maintaining high reliability.
3Reliability
If current limiting is performed based on temperature estimation, then overheating is prevented, but estimation errors reduce the effectiveness of current limiting
Solution Approach 1:
The patent applies feedback by continuously monitoring the base temperature through the temperature sensor and using this information to dynamically adjust current limiting decisions. The temperature estimation section continuously updates temperature estimates based on sensor readings and thermal models, and this feedback loop ensures that current limiting actions are timely and accurate, compensating for any estimation errors and maintaining reliable overheating prevention.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables precise temperature estimation and effective current limiting, ensuring reliable operation even when anomalies occur in one system, maintaining high accuracy and reducing estimation errors.
Implementation Method 1
a temperature detection element that detects a base element that is used as a base for estimation of inverter temperatures
Implementation Method 2
a temperature change amount generated due to current application to the inverters
Data Source
AI summary
A rotary electrical machine control apparatus is provided which controls drive of a rotary electrical machine having a plurality of winding sets. The apparatus includes inverters that are provided so as to respectively correspond to the winding sets, a temperature detection element that detects a base element that is used as a base for estimation of inverter temperatures, which are temperatures of the inverters, and a control section that has a temperature estimation section that estimates the inverter temperatures based on the base temperature and a temperature change amount generated due to current application to the inverters. On-resistance of the switching elements of the first inverter is smaller than on-resistance of the switching elements of the second inverter. The temperature detection element is disposed in an area, a distance between the area and the first inverter being shorter than a distance between the area and the second inverter.