EV Hill-Start Torque Control With Simulated Gear Shifting
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Solution Overview
Problem
Existing battery electric vehicles experience uncomfortable discontinuous drive wheel torque changes when the brake is suddenly released on a sloping road, leading to rearward or forward movement due to gravity, which affects the driving experience.
Innovation Solution
A battery electric vehicle equipped with an electric motor, a simulated gear shifting operation member, and a control device that calculates driver demand torque based on accelerator and gear shifting operations, applies a hold assist torque opposite to gravity, and smoothly transitions to driver demand torque when necessary, preventing rearward or forward movement on sloping roads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the brake is actuated to prevent vehicle movement on a sloping road, then the vehicle stability is improved, but the drive wheel torque changes discontinuously when the brake is suddenly released, causing driver discomfort
Solution Approach 1:
The system dynamically adjusts the brake actuation strategy based on driving conditions. When a manual shift operation is detected on a sloping road, the brake is actuated to prevent vehicle movement. The system then dynamically transitions from brake holding to driver demand torque when the clutch engagement state changes, ensuring smooth torque transfer and eliminating sudden torque changes that would cause driver discomfort.
Solution Approach 2:
The control system continuously monitors the clutch engagement state and driving conditions to determine when to actuate the brake and when to transition to driver demand torque. This feedback mechanism ensures that the brake is released at the optimal moment, preventing discontinuous torque changes and maintaining driver comfort while preserving vehicle stability on sloping roads.
2Productivity
If the brake is suddenly released when driver demand torque is sufficient, then the hold assist function is completed, but the discontinuous torque change causes uncomfortable feeling for the driver
Solution Approach 1:
The system prepares for the transition from hold assist to driver demand torque by monitoring the clutch engagement state in advance. When the clutch engagement state changes, indicating that the driver is ready to take control, the system smoothly transitions the torque delivery from brake holding to driver demand, preventing sudden torque changes and ensuring driver comfort while maintaining hold assist efficiency.
3Adaptability or versatility
If a simulated gear shifting operation member is added to imitate manual transmission, then the adaptability to different driving modes is improved, but the device complexity increases
Solution Approach 1:
The system uses a simulated H-shifter that replicates the appearance and basic operation of a traditional manual transmission shifter without requiring actual mechanical transmission components. This copying approach allows the vehicle to offer manual shift mode functionality and detect shift operations for hold assist control while avoiding the complexity of a real mechanical transmission system.
Data Source
AI summary
A battery electric vehicle includes a driving operation member including an accelerator pedal, a simulated gear shifting operation member, and a control device. The control device is configured to execute, by selection by a driver, a control mode in which a driver demand torque for driving an electric motor is calculated based on an operation amount of the accelerator pedal and operation of the simulated gear shifting operation member, and perform a hold assist when the control device detects that the battery electric vehicle is stopped on a road surface having a gradient. The hold assist includes outputting a hold assist torque that is a drive wheel torque in an opposite direction of gravity, and ending the output of the hold assist torque and performing switching to output of the driver demand torque, in response to exceedance of the driver demand torque over the hold assist torque.