Dynamics of an Underactuated Twistcar Robotic Vehicle: Experimental and Theoretical Analysis

The Twistcar is an underactuated toy vehicle composed of two segments: a primary segment on which the child sits, and a secondary segment on which the steering wheel is mounted. Each segment has an axle with wheels. This vehicle is propelled by periodically varying the relative angle of the steering segment. The vehicle is inherently underactuated, as the input changes the shape of the vehicle rather than directly affecting the vehicle’s variables. In this study, which extends previous research on the same vehicle, the scope of Twistcar’s movement has been expanded. Previous studies examined ideal cases without slipping, with non-holonomic constraints on the vehicle’s velocity perpendicular to the wheels, and assumed zero mass and moment of inertia for the secondary segment. When simulating without any dissipation, results showed unbounded speed and diverging oscillations of the vehicle body angle, which is not physical and has been proven to not match reality in previous experiments. In this research, the vehicle’s movement was theoretically examined through simulations, considering both rolling and sliding dissipation.