Studies on the wobble mode stability of a three-wheeled vehicle

Abstract

A wobble instability is one of the major problems of a three-wheeled vehicle commonly used in India, and these instabilities are of great interest to industry and academia. In this paper, we studied this instability using a multi-body dynamic model and with experiments conducted on a prototype three-wheeled vehicle on a test track. The multi-body dynamic model of a three-wheeled vehicle is developed using the commercial software ADAMS/Car. In an initial model, all components including main structures such as the frame, the steering column and the rear forks are assumed to be rigid bodies. A linear eigenvalue analysis, which is carried out at different speeds, reveals a mode that has predominantly a steering oscillation, also called a wobble mode, with a frequency of around 5-6 Hz. The analysis results shows that the damping of this mode is low but positive up to the maximum speed of the three-wheeled vehicle. However, the experimental study shows that the mode is unstable at speeds below 8.33 m/s. To predict and study this instability in detail, a more refined model of the three-wheeled vehicle, with flexibilities of three important bodies, was constructed in ADAMS/Car. With flexible bodies, three modes of a steering oscillation were observed. Two of these are well damped and the other is lightly damped with negative damping at lower speeds. Simulation results with flexibility incorporated show a good match with the instability observed in the experimental studies. Further, we investigated the effect of each flexible body and found that the flexibility of the steering column is the major contributor for wobble instability and is similar to the wheel shimmy problem in aircraft.

Shimmy model for electric vehicle with independent suspensions

“…By contrast, the shimmy models of Wang et al, 11 Wei and Jiang, 12 Lu et al, 8 Li and Lin 9 and Wei et al 10 are based on real vehicle-related multi-DoF systems with emphases either on the influence of different parameters of the model with independent suspensions or on the analysis of the model with dependent suspension. Karanam and Ghosal 13 established a multi-body dynamic model of a three-wheeled vehicle, the simulation results of which showed that the flexibility of the steering column can cause system instability. The shimmy of aircraft nose landing gear has also received a lot of attention.…”

Modelling the Dynamics of a Three-wheeled Racecar: A Pilot Study to Establish the Feasibility of Developing a ‘Delta’ Configuration Performance Car

“…The results are verified by simulation, and should eventually be validated against physical tests. Additional analysis such as those for 'wobble' (seen on three-wheeled rickshaws) [14] are neglected here.…”

Rollover stabilities of three-wheeled vehicles including road configuration effects

“…15 In addition, they are already an important part of transportation vehicles in some Asian countries. 16 3W vehicles can be designed with two different configurations. 17,18 The first configuration, called the delta configuration, has one wheel in the front and two wheels in the rear.…”