Envelope-Based Rigid Ring Model of E-Scooter Tires: Development and Validation of Vertical Dynamics

In today’s world where the use of e-scooters as a convenient mode of transportation is on the rise, there is a need for study on their dynamics and handling. The aim of this thesis is to develop a matlab model able to compute key components of vertical dynamics involved in the motion of an e-scooter tyre going over small obstacles on the road. The obstacle enveloping behaviour of the tyre is of importance in order to accurately portray it’s motion. Hence the first step undertaken is to develop in matlab, a program that allows one to input a given road profile and to obtain the effective road profile, by using the MF SWIFT obstacle enveloping model. To analyze the vertical dynamics of the tyre, it is suitable to use the MF SWIFT rigid ring model, for which the vertical belt stiffness, belt damping and residual stiffnesses need to be computed. The tyre of a Xiaomi pro II e-scooter is used for the experiments conducted to that end. Modal Analysis is conducted on a test set up of the tyre fitted with sensors, where the tyre is hammered at different points to excite the it’s modes and analyze them using Simcenter Testlab. This yields information on the various modes of the tyre, where the radial mode is of interest for computation of the belt stiffness and damping. The tyre is also subjected to a compression test where it is set up using a clamp to an MTS machine that delivers a load to the tyre quasi statically. The displacement of the tyre is recorded with respect to the applied load. From this experiment, one obtains the total radial stiffness of the tyre, from which the residual stiffness can be extracted. Finally, the model is executed in Simulink and tested to obtain the vertical displacements, accelerations and forces exchanged, for various road profiles. The results obtained from the model are compared to experimentally obtained values for validation.