All-Wheel Drive Drag Torque Detection via Angular Acceleration
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Solution Overview
Problem
Existing methods for operating all-wheel drive vehicles struggle to accurately determine drag torque without sensors, particularly the lubricating oil temperature, making it difficult to detect bearing defects and ensure smooth transitions between two-wheel and all-wheel drive modes.
Innovation Solution
Measure the rotational speed of uncoupled components when the all-wheel drive is disabled, calculate the angular acceleration, and use this to determine the drag torque, allowing for early detection of bearing defects and optimal torque control during mode transitions, even without temperature sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the all-wheel drive is disabled to minimize fuel consumption, then power losses and drag torque are reduced, but the rotational speed of uncoupled components decreases to zero causing difficulty in smooth re-engagement
Solution Approach 1:
Before disabling the all-wheel drive, the control unit stores the current rotational speed of the uncoupled components. This preliminary action enables the system to later reactivate the drive smoothly by using the stored speed information to control the re-acceleration process, avoidingjolts and ensuring comfortable transition between drive modes.
2Device complexity
If temperature sensors are removed to reduce device complexity and cost, then the system becomes simpler, but the ability to accurately determine drag torque and detect bearing defects is compromised
Solution Approach 1:
The control unit replaces temperature sensors with a mathematical model that calculates drag torque based on measured rotational speeds and angular accelerations of uncoupled components. This substitution eliminates the need for additional temperature sensing hardware while achieving accurate drag torque determination through physics-based calculations.
Solution Approach 2:
The system uses its own operational data (rotational speeds and angular accelerations of uncoupled components) to self-determine the drag torque without requiring external temperature sensors. The uncoupled components themselves provide the measurement data needed to calculate the drag torque, making the system self-sufficient.
3Reliability
If rotational speed is measured in a time interval to calculate angular acceleration, then bearing defects can be detected early, but the measurement and calculation process becomes more complex
Solution Approach 1:
The control unit continuously measures rotational speeds at different points in time, calculates angular accelerations, and compares these values against threshold criteria to detect bearing defects. This feedback mechanism enables early defect detection by monitoring changes in rotational behavior, while the evaluation criteria keep the assessment process systematic and manageable.
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
Enables early detection of bearing defects and smooth transitions between drive modes by accurately calculating drag torque, reducing the need for temperature sensors and improving comfort and efficiency.
Implementation Method 1
the control unit (14) measures the rotational speed of one of the uncoupled components (10, 16, 22) in a time interval, and determines an angular acceleration alpha of the uncoupled components (10, 16, 22) from the measured rotational speed
Implementation Method 2
determines an angular acceleration alpha of the uncoupled components (10, 16, 22) from the measured rotational speed
Implementation Method 3
Because the components are decelerated by an applied drag torque, their rotational speed gradually decreases to zero
Implementation Method 4
The drag torque comprises decelerating torque components, which result, among other things, from the oil sloshing of a crown wheel of the axle drive of the secondary or rear axle as well as the bearing friction of the connecting shaft
Implementation Method 5
The applied drag torque depends on multiple parameters, namely the rotational speed of the components, the oil level in the clutches and in the axle drive, the temperature of the lubricating oil in the axle drive
Data Source
AI summary
A method for operating a motor vehicle including an all-wheel drive that can be enabled and disabled, and a drive train including two clutches actuated by a control unit for enabling and disabling the all-wheel drive, and components rotating between the two clutches, which components are driven when the all-wheel drive is enabled and are uncoupled from the remaining drive train when the all-wheel drive is disabled. In order to allow early detection of defects and, in particular, bearing defects of the rotating components, and to determine the applied drag torque even without knowing the oil temperature, in one embodiment, when the all-wheel drive is disabled, the rotational speed (n) of at least one of the uncoupled components is measured in a time interval, and an angular acceleration of the uncoupled components is determined therefrom.