EV Motor Torque Control for Downhill Deceleration Comfort
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Solution Overview
Problem
Existing acceleration-deceleration control systems in electric vehicles fail to adequately address the uncomfortable feeling drivers experience due to excessive deceleration on downhill gradients, as they correct for road surface gradients, leading to unexpected deceleration sensations.
Innovation Solution
A control method and device that reduces the gradient correction amount on downhill roads by optimizing the gradient correction torque based on vehicle speed, using a disturbance-torque estimator and gradient correction amount adjuster to minimize uncomfortable deceleration feelings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the target acceleration/deceleration is corrected to eliminate the influence of the road surface gradient, then the vehicle can maintain uniform speed on gradient roads, but the driver experiences uncomfortable deceleration sensation on downhill roads
Solution Approach 1:
The control system applies different gradient correction strategies for different road conditions: full gradient compensation for uphill roads to maintain speed, and reduced gradient compensation for downhill roads to preserve natural deceleration sensation. This localized differentiation resolves the contradiction by tailoring the control response to specific driving scenarios.
Solution Approach 2:
The gradient correction amount is dynamically adjusted based on the detected road gradient and vehicle operating state. The system transitions from static gradient compensation to dynamic adjustment, reducing the correction amount on downhill roads while maintaining it on uphill roads, thereby adapting to driver expectations in different conditions.
2Ease of operation
If the gradient correction amount is reduced on downhill roads, then driver comfort is improved, but the vehicle speed maintenance capability is degraded
Solution Approach 1:
Instead of applying full gradient correction in all conditions, the system applies partial correction on downhill roads by reducing the gradient compensation amount. This partial action maintains sufficient speed control while avoiding excessive deceleration that would discomfort the driver.
Solution Approach 2:
The system changes the gradient correction parameter based on road gradient detection and vehicle state. By dynamically adjusting the correction amount parameter, the system optimizes both driver comfort and speed maintenance performance for different operating conditions.
3Ease of operation
If the target torque is set to obtain regenerative torque smaller than when inclination is zero on gentle down slopes, then appropriate braking force is generated, but the deceleration becomes insufficient for steeper downhill roads
Solution Approach 1:
The regenerative braking torque is dynamically adjusted based on the detected road gradient and vehicle speed. The system transitions from fixed torque settings to dynamic torque adjustment, ensuring appropriate deceleration for different downhill gradient conditions while maintaining driver comfort.
Solution Approach 2:
The control system uses feedback from gradient detection and vehicle state monitoring to continuously adjust the regenerative braking torque. This closed-loop control ensures that the braking force is optimized for current conditions, providing both comfort and sufficient deceleration capability.
Data Source
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AI summary
A control method for an electrically driven vehicle includes a motor configured to supply the vehicle with a braking force or a driving force corresponding to an accelerator operation amount. The control method is for controlling the braking force when the accelerator operation amount is less than a predetermined value and controlling the driving force when the accelerator operation amount is the predetermined value or more. In the control method, a torque target value at which the motor is caused to output a braking/driving torque corresponding to the accelerator operation amount is calculated, a disturbance torque acting on the motor as a resistance corresponding to a road surface gradient is estimated, a correction to remove the disturbance torque from the torque target value is performed, and the motor is controlled in accordance with the torque target value subjected to the correction. A correction amount in the correction is reduced in a downhill road when the accelerator operation amount is less than the predetermined value and a vehicle speed is larger than a predetermined vehicle speed.