Vehicle Drive Braking Power Control for Downhill Comfort
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Solution Overview
Problem
Existing methods for controlling drive and wheel braking systems in vehicles with driver assistance systems face challenges during downhill travel, leading to overheating of wheel braking systems and discomfort due to abrupt changes in transmission downshifting or engine torque during overrun mode transitions.
Innovation Solution
A method that composes total brake power into drive and wheel braking power, freezing the drive braking power when the gradient of total braking power exceeds a threshold, allowing maximum drive braking power while maintaining comfort and reducing brake load by setting the drive braking power to its maximum possible level and freezing it when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wheel braking system is used to provide total braking power during downhill travel, then the braking effect is achieved, but the wheel braking system becomes very hot and experiences excessive load
Solution Approach 1:
The total braking power is segmented into two independent components: drive braking power (Pdrive-wheel-setpoint) provided by the drive system and wheel braking power (Pbrake-wheel-setpoint) provided by the wheel braking system. This segmentation allows the drive system to bear the primary braking load during downhill travel, reducing the temperature and load on the wheel braking system while maintaining overall braking effectiveness.
2Reliability
If the drive system performs abrupt downshifting or changes overrun mode to provide drive braking power, then the braking effect is improved, but driver comfort deteriorates due to abrupt changes
Solution Approach 1:
The control method dynamically adjusts the drive braking power setpoint based on the gradient of the required total braking power. When the gradient exceeds a threshold, the drive braking power is frozen at its current value, preventing abrupt changes. This dynamic control strategy maintains braking effectiveness while ensuring smooth transitions that preserve driver comfort.
Solution Approach 2:
The control system continuously monitors the gradient of the required total braking power and uses this feedback to determine when to freeze the drive braking power. This feedback mechanism prevents abrupt downshifting and overrun mode changes by comparing the current gradient against a predetermined threshold, thereby maintaining comfort while achieving braking objectives.
3Reliability
If the drive braking power is increased to maximum level to reduce wheel braking load, then the wheel braking system load is reduced, but abrupt changes in engine torque and transmission occur
Solution Approach 1:
The control method applies preliminary action by freezing the drive braking power before abrupt changes can occur. When the gradient of required total braking power exceeds the threshold, the current drive braking power is frozen in advance, preventing subsequent abrupt changes in engine torque and transmission. This preliminary freezing action maintains comfort while still reducing wheel braking system load.
Data Source
AI summary
A method is provided for controlling a drive system and/or a wheel braking system of a vehicle, in which a total braking power to be exerted on the wheels of a motor vehicle is composed of a drive braking power and/or a wheel braking power. The instantaneously set drive braking power is frozen when, starting from a steady state operating mode, the gradient of the required total braking power exceeds a predetermined threshold.