Adaptive Motor Temperature Filter for Electric Power Steering
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Solution Overview
Problem
Conventional electric power steering systems face challenges in quickly and accurately detecting overheating of electric motors, particularly when high torque is requested, which can lead to motor damage due to excessive electrical current. Additionally, there is a need for systems to automatically adjust sensitivity in detecting overheating and to effectively limit current in brushless motors.
Innovation Solution
A controller that estimates motor temperature, filters the estimates to reduce noise, adjusts smoothing factors based on heating or cooling conditions, and sets limits on electrical current to prevent overheating, using a combination of temperature and current sensors and a motor current control mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a large amount of electrical current is provided to the electric motor to meet high torque requests, then the motor can provide sufficient steering force, but the motor overheats and suffers damage
Solution Approach 1:
The controller performs preliminary actions by continuously estimating motor temperature and filtering these estimates before actual overheating occurs. The temperature estimation and filtering process prepares the system in advance to detect heating trends, allowing proactive current limiting before damage happens
Solution Approach 2:
The system implements feedback by continuously monitoring estimated motor temperature, comparing filtered temperature values to detect heating or cooling trends, and adjusting electrical current limits based on this feedback. The controller modifies current provision according to the detected temperature trend, creating a closed-loop control system
2Reliability
If conventional temperature monitoring methods are used, then the system can detect overheating, but the detection is not quick or accurate enough to prevent motor damage
Solution Approach 1:
The system performs preliminary temperature estimation and filtering continuously, even when the motor is not yet overheating. This preliminary action ensures that accurate temperature data is already available when needed, eliminating detection delays
Solution Approach 2:
The invention changes the parameter being monitored from direct temperature measurement to estimated temperature based on electrical current and thermal models. This parameter change enables more frequent and accurate temperature estimation without waiting for physical temperature sensors to detect changes
3Stability of the object's composition
If the filter smoothing factor is kept constant, then the temperature estimation is stable, but the system cannot automatically adjust to different heating or cooling conditions
Solution Approach 1:
The system transitions from a static, constant smoothing factor to a dynamic, adaptive smoothing factor that automatically adjusts based on detected temperature trends. When heating is detected, the smoothing factor changes to prioritize stability; when cooling is detected, it adjusts to respond more quickly, making the system adaptive to different thermal conditions
Data Source
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AI summary
Techniques for limiting electrical current provided to a motor for an electric power steering system are provided. A first estimated temperature of the motor is determined for a first time step. The first estimated temperature of the motor is filtered to produce a first filtered estimated temperature of the motor. A second estimated temperature of the motor is determined for a second time step subsequent to the first time step. The first filtered estimated temperature is compared with the second estimated temperature to determine whether the motor is heating or cooling. The filter is adjusted in response to determining whether the motor is heating or cooling. The second estimated temperature of the motor is filtered with the adjusted filter to produce a second filtered estimated temperature of the motor. A limit on electrical current provided to the motor is set using the second filtered estimated temperature.