Brake Roller Testing for AWD Axles Without Differential Torque Transfer
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Solution Overview
Problem
Conventional brake testing devices are inadequate for vehicles with multiple driven axles, particularly all-wheel drive vehicles, as they fail to accurately measure braking effects due to torque transmission issues and wheel circumference differences, leading to falsified measurement results.
Innovation Solution
A brake testing device equipped with sensor devices on both sides of the tested axle that measure rotational speeds and control motor-driven rollers to maintain wheel speed differences within the backlash of the differential, ensuring accurate measurement of individual braking torques without power transfer between wheels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional brake testing devices are used on all-wheel drive vehicles, then the testing process is simple, but the measurement results are falsified due to torque transmission through the rigid drive system
Solution Approach 1:
The testing device segments the drive system by providing separate motor-driven roller devices for each wheel, allowing independent control of each wheel's rotation. This segmentation prevents torque transmission through the differential and rigid drive system, enabling accurate measurement of individual brake effects without interference from the vehicle's powertrain.
Solution Approach 2:
The device applies local quality by making each roller device independently controllable with its own motor, allowing precise local control of wheel rotation speeds. This enables the system to maintain different rotational states for different wheels, preventing power transfer while ensuring accurate local measurement at each wheel position.
2Measurement precision
If wheels are driven at different rotational speeds to prevent torque transfer, then measurement accuracy improves, but control complexity increases
Solution Approach 1:
The control system incorporates feedback mechanisms that continuously monitor the rotational speeds of the wheels and adjust the motor-driven rollers accordingly. This feedback control ensures that wheels are driven at precisely controlled speeds, maintaining the condition where no torque is transferred through the differential while enabling accurate braking torque measurement.
Solution Approach 2:
The system dynamically adjusts the rotational speeds of individual wheels during the testing process. By making the wheel speeds variable and controllable rather than fixed, the system can adapt to different testing conditions and maintain optimal measurement conditions throughout the brake test, preventing torque transfer while ensuring measurement accuracy.
3Ease of operation
If motor-driven rollers are used to control wheel rotation, then wheel speed control is achieved, but device complexity and cost increase
Solution Approach 1:
Each motor-driven roller device serves multiple functions: it drives the wheel at controlled speeds, prevents torque transfer through the differential, and enables accurate braking measurement. This multi-functionality reduces the need for additional separate systems, making the increased complexity worthwhile by achieving precise control and accurate measurement in a integrated manner.
Data Source
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AI summary
A brake testing device and a brake testing procedure are provided for a vehicle equipped with at least one driven axle with a differential and a drive for the differential, the drive of which is rotationally fixed during the brake test. The wheel or wheels on one side of the tested axle are driven in a forward direction by a pair of rollers driven by a motor, while the other wheel or wheels on the opposite side of the tested axle are driven in the opposite direction by another pair of rollers driven by a motor. A sensor device is provided for each side of the tested axle, which can be mounted on the respective wheel in any orientation and which generates a rotational angle vector of the wheel about an axis that is at least substantially horizontal.A control system regulates the rotational speeds of the motors in such a way that the difference in the angle of rotation of the wheels on both sides of the tested axle corresponds at least essentially to a maximum of the backlash of the tested axle.