Automated Drive Train Clutch Modulation for Slope Rolling Prevention
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Solution Overview
Problem
In motor vehicles with automated transmissions, there is a challenge in preventing unwanted movement due to slope gravity when the service brake is released, as existing methods require additional sensors and complex calculations to determine the desired drive direction and manage clutch pressure effectively.
Innovation Solution
A method that uses a control unit to automatically disengage and re-engage the drive connection based on the activation and release of the service brake, employing first and second modulation characteristic curves for clutch pressure increase, determined by the comparison of the nominal and actual drive directions, without additional sensors, ensuring the drive direction matches the driver's intention and preventing unwanted rolling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional sensors (inclination sensor, brake pressure sensor) are used to determine drive direction and manage clutch pressure, then the reliability of preventing unwanted movement on slopes is improved, but the device complexity and cost increase
Solution Approach 1:
The control unit utilizes existing sensor data (wheel rotational speeds, gear position) that are already available in the vehicle's automated transmission system to determine the nominal drive direction and detect actual drive direction during brake release, eliminating the need for additional inclination sensors or brake pressure sensors. The system serves itself by repurposing existing measurement capabilities for the additional function of slope movement prevention.
Solution Approach 2:
The control unit performs multiple functions: it manages the automated clutch engagement/disengagement for normal transmission operation, determines the nominal drive direction based on gear position, detects actual drive direction during brake release, and applies appropriate modulation characteristic curves. This multi-functionality eliminates the need for separate dedicated sensors for slope detection.
2Reliability
If clutch pressure is increased rapidly to prevent downhill rolling, then the reliability of preventing unwanted movement is improved, but the comfort of vehicle operation deteriorates due to abrupt engagement
Solution Approach 1:
The system dynamically adjusts the clutch pressure modulation characteristic based on the detected drive direction mismatch. Two different modulation characteristic curves are stored: a first curve for normal engagement and a second curve for slope conditions. The control unit selects the appropriate curve in real-time based on whether the actual drive direction during brake release matches the nominal drive direction, enabling adaptive response to different operating conditions.
Solution Approach 2:
The control unit detects the drive direction mismatch during the brake release phase, before the vehicle actually starts moving downhill. By identifying the potential slope rolling condition in advance during the brake release transition, the system can prepare and apply the appropriate second modulation characteristic curve to prevent the unwanted movement before it occurs, rather than reacting after the vehicle has already rolled.
3Ease of operation
If the drive connection is disengaged during braking to standstill, then the ease of operation is improved, but the reliability of preventing unwanted movement on slopes deteriorates
Solution Approach 1:
The control unit continuously monitors the drive direction during the brake release phase by comparing the nominal drive direction (from gear position) with the actual drive direction (from wheel rotational speeds). This feedback mechanism detects when the vehicle is on a slope and the brake release causes unwanted movement, triggering the application of the second modulation characteristic curve to correct the situation.
Solution Approach 2:
The control unit determines the nominal drive direction in advance based on the selected gear step before the brake release is complete. By having this information prepared beforehand, the system can quickly compare it with the actual drive direction during brake release and immediately apply the appropriate modulation characteristic curve if a mismatch is detected, enabling rapid response to slope 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
This method effectively prevents unwanted rolling on slopes without additional sensors, allowing for reliable recognition and reaction to the driver's intended direction, particularly during 'stop and go' maneuvers, by using existing wheel rotational speed sensors and brake light sensors, and adjusts clutch pressure accordingly to ensure safe and comfortable vehicle operation.
Implementation Method 1
a first modulation characteristic curve is used for the increase of the pressure in the clutch
Data Source
AI summary
A method for operating an automated drive train of a motor vehicle in which, upon actuation of a service brake up to a standstill of the vehicle, a drive connection between the drive machine and at least one drive axle of the vehicle is automatically disengaged by disengaging a clutch. During release of the service brake, the drive connection is automatically engaged by engaging the clutch. Based on a selected gear step, a desired drive direction of the vehicle is determined, and, during the release of the service brake, is compared with an actual drive direction. If the desired drive direction matches the actual drive direction, the pressure in the clutch is increased according to a first modulation characteristic curve. However, if the desired drive direction is different from the actual drive direction, the pressure in the clutch is increased according to a second modulation characteristic curve.