Hybrid Vehicle Motor Angle Estimation via Crankshaft Variation
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Solution Overview
Problem
In hybrid electric vehicles, when a resolver fails, the coarse precision of the crank angle sensor used for motor control leads to weak field control issues, causing overvoltage in the inverter, torque fluctuations, and potential battery and capacitor deterioration, as it cannot accurately control induced voltage or torque.
Innovation Solution
A method to estimate the motor rotation angle based on the variation rate of the crankshaft revolutions, allowing for weak field control without affecting the precision of the crank angle sensor, using a control circuit to adjust switching operations in the inverter circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the crank angle sensor is used for motor control when the resolver fails, then the motor control can continue, but the precision of the detected angle becomes much coarser leading to weak field control failure
Solution Approach 1:
The invention introduces an intermediary estimation mechanism that uses crank angle sensor data combined with motor electrical angle calculations to derive a more precise effective rotation angle. The control circuit estimates the motor rotation angle by combining the crankshaft position information with the motor's electrical angle characteristics, acting as a mediator between the coarse crank angle sensor and the fine precision required for vector control
Solution Approach 2:
The invention changes the parameter representation by transforming the coarse crank angle measurements into a refined effective rotation angle through mathematical estimation. By calculating the motor electrical angle based on motor revolutions and combining it with crankshaft position data, the system transforms low-precision input parameters into high-precision control parameters
2Reliability
If vector control is performed using crank angle sensor information, then motor control continues, but the induced voltage cannot be suppressed and overvoltage occurs in the inverter
Solution Approach 1:
The estimation of effective rotation angle serves as an intermediary that enables accurate vector control calculations. By providing a refined angle value that accounts for both crankshaft position and motor electrical angle, the system can properly control the d-axis and q-axis currents to suppress induced voltage and prevent inverter overvoltage
Solution Approach 2:
The control circuit uses feedback from the estimated effective rotation angle to continuously adjust the switching operations of the inverter. This feedback mechanism ensures that the motor control adapts to the actual motor state, maintaining proper voltage control and preventing harmful overvoltage conditions
3Reliability
If the crank angle sensor with coarse precision is used, then motor control can be maintained, but torque fluctuation increases and necessary torque cannot be output
Solution Approach 1:
The invention transforms the coarse crank angle parameter into a refined effective rotation angle parameter through estimation calculations. This parameter transformation enables accurate torque control by providing the precise angular information needed for proper vector control, thereby stabilizing output torque and eliminating fluctuations
Data Source
AI summary
The present invention is directed to a method of estimating a motor rotation angle that does not affect precision of a detected angle of a crank angle sensor, which is an alternative sensor, when abnormality occurs in a resolver and a peripheral circuit, and performing a motor control without failure of an inverter or peripheral device. A vehicle system includes a motor, a resolver detecting a rotor rotation angle of the motor, a motor control circuit controlling the motor based on information on rotor rotation angle and torque command value, an engine connected to the motor through a crankshaft, and a crankshaft sensor detecting revolutions of the crankshaft, in which the motor control circuit estimates rotor rotation angle based on a variation rate of the number of revolutions of the crankshaft when abnormality of the resolver is detected, and performs a weak field control based on estimated rotor rotation angle.