Electric Power Steering Coil Temperature Estimation
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Solution Overview
Problem
Conventional electric power steering apparatuses face challenges in accurately estimating coil temperature, especially when abnormalities occur, due to the lack of consideration for heat transfer between phase coils and the control substrate, leading to potential errors in temperature estimation.
Innovation Solution
An electric power steering apparatus that includes a temperature sensor to detect the substrate temperature and a coil temperature estimating section, which calculates coil calorific values and substrate calorific values using motor current data, correcting these values when abnormalities occur to estimate coil temperature based on heat transfer phenomena expressed by differential equations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If heat transfer between phase coils and control substrate is not considered in temperature estimation, then the estimation process is simpler, but the temperature estimation accuracy deteriorates
Solution Approach 1:
The temperature estimation model is segmented into multiple independent heat transfer paths: heat generation in each phase coil, heat transfer from coil to substrate, and heat transfer from substrate to environment. Each path is modeled separately with its own differential equation, allowing accurate representation of complex thermal behavior while maintaining manageable computational complexity through modular structure
Solution Approach 2:
The control substrate is introduced as an intermediary thermal element between the phase coils and the environment. The substrate acts as a heat transfer medium that receives heat from multiple coil phases and dissipates it to the environment, enabling accurate modeling of heat transfer phenomena that would be difficult to capture if coils were modeled directly interacting with ambient air
2Reliability
If conventional temperature estimation methods are used without substrate temperature detection, then the system structure is simpler, but the temperature estimation accuracy deteriorates under abnormal conditions
Solution Approach 1:
A temperature sensor is installed on the control substrate to detect substrate temperature in advance. This preliminary temperature measurement provides critical boundary condition data for the heat transfer model, enabling accurate coil temperature estimation even when abnormal conditions occur and making real-time corrections to the estimation algorithm
Solution Approach 2:
The substrate temperature detection creates a feedback loop where the measured substrate temperature is continuously fed into the temperature estimation model. This feedback allows the system to dynamically adjust temperature estimates based on actual thermal conditions, significantly improving reliability under abnormal operating conditions
3Measurement precision
If heat transfer phenomenon between coil and control substrate is considered, then temperature estimation accuracy is improved, but the calculation complexity increases
Solution Approach 1:
The heat transfer model uses parameter changes to simplify calculations: thermal resistance and thermal capacitance parameters are defined for each heat transfer path, transforming complex partial differential equations into more manageable ordinary differential equations that can be solved efficiently with standard numerical methods while maintaining high accuracy
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 approach enables more precise and accurate estimation of coil temperature, even during abnormal conditions, by considering heat transfer between the control substrate and coils, ensuring safe operation and preventing overheating.
Implementation Method 1
a temperature sensor (105) that detects a substrate temperature of the control substrate
Implementation Method 2
estimates a coil temperature of the phase by the coil calorific value, the substrate calorific value and the substrate temperature based on a heat transfer phenomenon between the respective phases that is caused by a difference in temperature between coils of the respective phases and a heat transfer phenomenon between the coil and the control substrate
Implementation Method 3
obtains coil calorific values of respective phases of the poly-phase motor and a substrate calorific value of the control substrate by a motor current of the phase
Data Source
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AI summary
[Problem] An object of the present invention is to provide an electric power steering apparatus that enables more precise estimation of a coil temperature by considering a heat transfer phenomenon between a control substrate and a coil in addition to a heat transfer phenomenon between respective phases of a poly-phase coil for a poly-phase motor having a multi-system motor winding, and enables the estimation of the coil temperature even when an abnormality occurs in any of the systems. [Means for solving the problem] An electric power steering apparatus comprises a temperature sensor that detects a substrate temperature of the control substrate; and a coil temperature estimating section that obtains coil calorific values of respective phases of the poly-phase motor and a substrate calorific value of the control substrate by a motor current of the phase, and estimates a coil temperature of the phase by the coil calorific value, the substrate calorific value and the substrate temperature based on a heat transfer phenomenon between the respective phases that is caused by a difference in temperature between coils of the respective phases and a heat transfer phenomenon between the coil and the control substrate; the coil temperature estimating section estimates the coil temperature by values that are obtained by correcting the coil calorific value and the substrate calorific value that are obtained in a normal system, and the substrate temperature, when an abnormality occurs in any of systems; and the heat transfer phenomenon is expressed by a differential equation.