Brake Test Stand Wheel Decoupling for Accurate Braking Force Measurement
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Solution Overview
Problem
Conventional brake test stands struggle to accurately determine the braking effect of individual brakes in vehicles with multiple driven axles, particularly four-wheel drive vehicles, due to issues like unequal rotational speeds and force transmission between axles, leading to incorrect measurement results.
Innovation Solution
A method and device that automatically detect whether a vehicle has two driven axles by actuating one drive motor to turn a wheel in one direction and checking for a small jerk in the opposite direction, using separately controllable drive motors to maintain equal rotational speeds and prevent force transfer between axles during braking tests.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional brake test stands with two pairs of rollers are used to test vehicles with two driven axles, then the braking forces can be measured, but the rigid or quasi-rigid drive system causes the rear wheels to be driven when testing front wheels, resulting in the vehicle pushing itself out of the test bench and transferring braking effects between axles
Solution Approach 1:
The test bench is divided into four independently controllable drive devices, one for each wheel. This segmentation allows each wheel to be tested independently without force transmission from other wheels through the drive system, eliminating the harmful effect of inter-axle force transfer while maintaining accurate braking force measurement.
Solution Approach 2:
The drive devices are designed with dynamic speed control capability, allowing each wheel to be rotated at potentially different speeds. This dynamic adjustment prevents the rigid drive system from transferring forces between axles during testing, as each wheel can operate independently at its required test speed.
2Object-generated harmful factors
If the wheels of the tested axle are rotated in opposite directions to stop the rigid drive system, then the vehicle no longer pushes out of the test bench, but different wheel circumferences cause unequal rotational speeds and power transfer between wheels, falsifying braking values
Solution Approach 1:
By providing separate drive devices for each wheel rather than coupling wheels in pairs, the system can independently control each wheel's rotation. This eliminates the problem of unequal speeds causing power transfer, as each wheel's drive device operates independently without mechanical coupling that would transfer forces between wheels.
Solution Approach 2:
The control device acts as an intermediary that coordinates the four independent drive devices. It monitors and adjusts each drive device's operation to ensure wheels rotate at appropriate speeds while preventing harmful force transfers, resolving the contradiction between stopping vehicle movement and maintaining measurement accuracy.
3Measurement precision
If four pairs of rollers are provided to test all wheels independently, then accurate braking measurement is possible, but the device complexity increases significantly
Solution Approach 1:
Each of the four drive devices is designed as a universal, identical unit that can independently test any wheel. This modular approach allows the system to maintain high measurement precision through independent wheel testing while managing complexity by using repeated, standardized components rather than complex custom mechanisms.
Data Source
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AI summary
The method involves having two driven axles (12, 14) during which the wheels of one axle are firstly driven onto two sets of rollers of a roller type test stand. One wheel (60L, 60R, 66L, 66R) is then driven with a desired speed by the one pair of rollers whereas the respective other wheel is driven over a range of speed that normally contains the desired speed. The speed for the respective other wheel is then determined at which the rolling resistance is lowest. The pair of rollers is then driven at this speed. An independent claim is included for a device.