Torque Control for Hybrid Electric Vehicle ISG Failure
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Solution Overview
Problem
Hybrid electric vehicles face deteriorated driving and acceleration performance due to the failure of the integrated starter-generator (ISG), as existing methods fail to accurately compensate for the drag generated by transfer torque during engine start-up, leading to inadequate mode conversion and potential safety risks.
Innovation Solution
A torque control method that detects ISG failure, calculates driver demand torque using an accelerator position sensor, and controls hydraulic pressure and clutch operation to increase engine speed, synchronize engine and motor rotational speeds, and compensate driver demand torque by calculating and compensating transfer torque from the clutch to the motor, enabling smooth mode conversion to hybrid electric vehicle mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If friction start method is used to start up the engine using clutch slip during driving, then the engine can be started up, but the drag generated by transfer torque of the clutch is not compensated, deteriorating driving performance and acceleration performance
Solution Approach 1:
The control unit calculates the transfer torque of the clutch in real-time based on the slip rotation amount and slip rotation speed, and uses this calculated value to compensate the driver demand torque. This feedback mechanism ensures that the drag generated by clutch slip is accurately quantified and compensated, resolving the contradiction between achieving engine start-up and maintaining driving performance.
Solution Approach 2:
The system performs preliminary calculation of the transfer torque before engine start-up based on predicted slip characteristics, and pre-compensates the driver demand torque. This preliminary action ensures that when clutch slip occurs during engine start-up, the drag is already accounted for in the torque calculation, preventing deterioration of driving performance.
2Adaptability or versatility
If mode conversion from EV mode to HEV mode is performed during engine start-up by ISG, then the vehicle can operate in hybrid mode, but in the event of ISG failure the engine start-up becomes difficult and driving performance deteriorates
Solution Approach 1:
The control unit detects ISG failure in advance and prepares an alternative engine start-up method using clutch slip. By calculating the transfer torque and compensating driver demand torque before the actual start-up attempt, the system cushions against the potential failure mode, ensuring reliable engine start-up even when ISG is unavailable.
Solution Approach 2:
The clutch acts as an intermediary mechanism to enable engine start-up when ISG fails. By controlling clutch slip and calculating the associated transfer torque, the system uses the clutch as a mediator to achieve engine start-up and mode conversion without the ISG, maintaining reliability despite the failure of the primary starting mechanism.
3Ease of operation
If driver demand torque calculation does not accurately reflect driver's intention, then the vehicle may be driven against driver's intention, but accurate calculation is essential for maintaining driving performance and safety
Solution Approach 1:
The control unit continuously calculates driver demand torque based on accelerator pedal position and vehicle state, and adjusts the motor torque output in real-time. By incorporating transfer torque compensation from clutch slip into the torque calculation feedback loop, the system accurately reflects driver intention while maintaining driving performance and safety even during clutch slip conditions.
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
The method improves driving and acceleration performance by accurately compensating driver demand torque and enabling seamless mode conversion from electric vehicle to hybrid electric vehicle mode during ISG failure, reducing the risk of accidents and maintaining clutch durability.
Implementation Method 1
a method of starting up an engine (friction start) using friction of an engine clutch during driving
Implementation Method 2
controlling the hydraulic pressure and operation of a clutch
Data Source
AI summary
The present invention provides a torque control method for an HEV, the method comprising: detecting an operation failure of an integrated starter-generator (ISG); calculating a driver demand torque based on a current accelerator position sensor (APS); controlling the hydraulic pressure and operation of a clutch so as to increase an engine speed to convert the driving mode of the vehicle from electric vehicle (EV) mode to hybrid electric vehicle (HEV) mode in the event that an operation failure of the ISG is detected and the driver demand torque is out of a predetermined range; and compensating the driver demand torque to a desired level based on a transfer torque from the clutch to a motor. The method can improve driving performance and power performance of HEV, in the event of ISG failure, by performing a hydraulic control for a clutch and calculating a driver request torque and a transfer torque from the clutch to a motor to compensate the drive request torque to a desired level.