Motor Coil Temperature Estimation via Resistance Curves
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Solution Overview
Problem
Existing electric power assisted steering systems face challenges in accurately estimating motor coil temperature during system restart, leading to potential overheating and permanent damage, as existing methods rely on imprecise temperature measurements that take into account the entire power pack or motor temperature rather than specifically the coil temperature.
Innovation Solution
A method that involves storing resistance curves for motor coils and the ECU, measuring demand voltage and current, determining power pack and ECU resistances, and calculating motor coil temperature to accurately estimate the lost temperature increment after system restart, ensuring the motor operates within safe temperature limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the base temperature (ECU temperature) is used to estimate coil temperature after system restart, then the estimation process is simple, but the temperature estimation is inaccurate and the motor remains unprotected from overheating
Solution Approach 1:
The patent changes the estimation parameter from using only base temperature to using resistance-based temperature estimation. By measuring the resistance of motor coils and ECU components and comparing against stored resistance-temperature characteristics, the system accurately determines the actual temperature state of motor coils after restart, resolving the inaccuracy of simple base temperature estimation.
Solution Approach 2:
The patent replaces the thermal sensor-based mechanical temperature measurement system with an electrical resistance-based estimation system. Instead of relying on thermal sensors that measure ECU board temperature, the system uses electrical resistance measurements of motor coils and compares them against stored resistance-temperature characteristics to estimate coil temperature, providing more accurate and direct temperature measurement.
2Reliability
If the motor current is limited to protect the motor from overheating, then the motor is protected from damage, but the steering assist performance is reduced
Solution Approach 1:
The patent implements a feedback mechanism where the estimated coil temperature is continuously monitored and used to adjust motor current limiting. The system estimates coil temperature based on resistance measurements, compares it against safe operating thresholds, and dynamically adjusts current limits accordingly. This allows the motor to operate at full power when temperatures are safe while providing protection when temperatures exceed thresholds.
3Ease of operation
If the thermal sensor measures ECU board temperature, then the temperature measurement is straightforward, but it does not accurately reflect the motor coil temperature
Solution Approach 1:
The patent introduces electrical resistance as an intermediary parameter to indirectly measure motor coil temperature. Instead of directly measuring coil temperature with a thermal sensor, the system measures the electrical resistance of the motor coils, which correlates with temperature, and uses this resistance data to estimate the actual coil temperature, providing accurate measurement without direct thermal contact.
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 method allows for precise estimation of motor coil temperature from the start, preventing overheating and enabling robust diagnostics, thus protecting the motor from damage and improving system reliability.
Implementation Method 1
a temperature sensor integrated in the ECU measures a temperature of the ECU
Implementation Method 2
Storing a given resistance curve of the motor coils... Determining the temperature of the motor coils based on a difference between the power pack resistance and the resistance of the ECU and the stored resistance curve of the motor coils
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a method for estimation of lost temperature increment (TLostIncrement) after system restart for motor coil temperature estimation in an electric power steering apparatus (1) of a motor vehicle with a power pack (100) comprising an ECU (10) with a temperature sensor (16) and an electric motor (7), said method comprises the steps of: a) Storing a given resistance curve of the motor coils (14); b) Storing a measured resistance curve of the ECU (15); c) Measuring a demand voltage vector (Ud,d) and a demand current vector (ld,d) based on a demand motor current and a battery voltage (Ubat) during a special measurement pulse; d) Determining the power pack resistance (Rpowerpack) based on the parameters measured in step c); e) Measuring the temperature of the ECU (TECU) with the temperature sensor (16); f) Determining the resistance of the ECU (RECU) on basis of the measured temperature in step e) and the stored resistance curve of the ECU (15); g) Subtracting the resistance of the ECU (RECU) from the determined power pack resistance (Rpowerpack); h) Determining the temperature of the motor coils (Tmotorcoil) based on the value obtained in step g) and the stored resistance curve of the motor coils (14); i) and Obtaining the lost temperature increment (TLostIncrement) by subtracting the measured temperature of the ECU (TECU) from the determined temperature of the motor coils (Tmotorcoil).