Evaluation of the handling of a variable dynamics tilting tricycle

Abstract

The favorite way of transport for commuters is still by cars, which are designed too heavy and too wide for the average amount of passengers. Accidents without other traffic users make up a large proportion of crashes for free-tilting bicycles. Tricycles have a chance of rollover while cornering fast.Therefore, new human-powered commuter vehicles are needed that have optimized handling performance and are safer. This alternative can be the narrow tilting tricycle, with the combined advantages of bicycles and tricycles. Faster cornering can be performed than with a tricycle, and better balance and more traction can be obtained than with a bicycle. No method exists to evaluate the handling performance of a narrow tilting tricycle that gives a combined conclusion about the handling performance for multiple velocities and aspects of handling.This study evaluated the optimized handling performance for commuting for a prototype tilting tricycle. The tricycle is designed by Andrew Dressel and built by DEMO at TU Delft. The tilt mechanism incorporates tie rods that connect A-arms to the bell crank at adjustable connection points. This coordinates the tilt behaviour which changes with different connections from the tie rods to the bell crank. I created a novel handling evaluation method for commuter vehicles in a quantitative within-subjects study. I selected a moderate-speed slalom manoeuvre and a low-speed line-following manoeuvre as test manoeuvres. I have measured the maximum yaw factor, the mean absolute steer angle, and the time delay between the roll rate and steer as handling metrics using two Shimmer3 IMUs. The first metric is evaluated for the slalom manoeuvre and the second and third metrics are evaluated for the low-speed line-following manoeuvre. I scaled the metrics and combined the results into a single score. The selected metrics are able to discriminate between the performance of conventional bicycles and prototypes of tilting tricycles. For highly similar designs, it is important to add trials until statistical significance can be reached.
The analysis of the data showed the optimal handling performance of the Dressel tilting tricycle for tie rod angles halfway between free-tilting and self-stable when stationary. For commuter vehicles in city traffic, the tie rods can be fixed at 50%. Increased low-speed balance is proven for increased tie rod angles, without finding reduced performance on the moderate-speed slalom. It is not recommended to increase the tie rod angle to 75%. Uncontrollable performance has been observed in this configuration.A tie rod angle of 100% can provide complete rigidity while standing still. The tilt limit has been hit with increased tie rod angles and this limit is increased with a Matlab optimization. For the optimal configuration with tie rods connected halfway in, the bell crank should be designed 380 mm wide and connected 235 mm high from the ground.
The tilt mechanism with the optimal design parameters can make the vehicle safer because of the improved balance, without reducing the handling performance. A fixed design can make the vehicle cheaper and easier to build compared to the adaptable tilting tricycle.