Steerable Synchronized Wheel Speed Dynamometer
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Solution Overview
Problem
Current chassis dynamometers lack the capability to actuate the vehicle's steering system and synchronize the wheel speed of all four wheels, which is essential for testing autonomous driving features effectively and efficiently.
Innovation Solution
A steerable synchronized wheel speed dynamometer system that mechanically couples the front and rear wheels to synchronize their wheel speeds and allows for steering actuation, using an outer wheel hub bearing assembly, a power transmission device, and a continuously variable transmission drive shaft with 90-degree differentials and adjustable length drive shafts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a typical roller-type dynamometer is used for emissions and fuel economy certification, then the vehicle can be tested on a chassis dynamometer, but the steering system cannot be actuated and all four wheels cannot spin at synchronous speed
Solution Approach 1:
The system divides the wheel speed synchronization function into separate components: a first differential mechanism for the front wheels and a second differential mechanism for the rear wheels. Each differential independently controls the speed of its associated wheels, allowing steering actuation while maintaining synchronous speed across all four wheels. This segmentation resolves the contradiction by enabling steering capability without requiring a completely complex redesign of the entire dynamometer system.
2Adaptability or versatility
If a steerable dynamometer system is implemented to allow steering actuation, then the steering system can be tested, but the system cost increases to two-to-four-million dollars with additional infrastructure requirements
Solution Approach 1:
The dynamometer system is designed to perform multiple functions: it can test both steering actuation and wheel speed synchronization using the same basic infrastructure. The differential mechanisms are integrated into the existing roller-type dynamometer framework, allowing the system to handle various autonomous driving feature tests without requiring completely separate testing facilities. This multi-functionality reduces the need for additional expensive infrastructure while maintaining steering testing capability.
3Ease of manufacture
If a 2WD dynamometer is used, then the facility infrastructure is simpler, but vehicle safety features including traction control, ABS, and vehicle stability control are disabled because wheel speed sensors are not rotating at synchronous speed
Solution Approach 1:
The differential mechanisms act as intermediaries between the roller-type dynamometer rollers and the wheel speed sensors. The differentials receive rotational input from the rollers and distribute it to all four wheels at synchronous speeds, ensuring that the wheel speed sensors rotate at the required synchronous speed for safety features to operate. This intermediary function allows the use of simpler 2WD dynamometer infrastructure while maintaining the reliability needed for vehicle safety feature testing.
Data Source
AI summary
A system and method for a steerable synchronized wheel speed dynamometer system that passes steerable vehicle transmission power through a non-driven vehicle wheel includes an outer wheel hub bearing assembly, a power transmission device and a continuously variable (CV) transmission variable length drive shaft. The outer wheel hub bearing assembly includes a central portion having a through-bore aligned with a central axis of rotation of the outer wheel hub bearing assembly and a first roller bearing assembly mounted circumferentially around a portion of the central portion to support a central aperture in a hub of a non-driven wheel of the vehicle. The power transmission device receives the powered steerable transmission output via a power transfer shaft when received in the through-bore. The CV transmission drive shaft includes a variable length drive shaft angularly and rotatably connected to the power transmission device.