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Electric skateboards have gained significant popularity in urban transportation, especially amongst younger demographics such as on university campuses. The electric drive system has greatly increased the speed achievable on the skateboard platform, driving the need for investigation into the dynamic instabilities associated with this unique mode of transportation. At high speeds, the skateboard system encounters a bifurcation, at which point the rider becomes unstable as a result of the interactions between the centrifugal effects on the rider and the tilt-steering mechanism. This instability commonly results in the rider being thrown from the board onto the pavement at very high speeds.
In this thesis, a novel three-dimensional, four-degree-of-freedom skateboard-rider model is proposed to address the limitations of existing skateboard dynamic models. The proposed model combines the balancing efforts of a physiologically accurate rider with a spherical inverted pendulum model under the effects of fictitious forces resulting from the acceleration of the non-inertial reference frame due to the steering action of the skateboard. The proposed model is simulated and analyzed at varying velocities, truck stiffnesses, and board lengths to better understand the effects of various skateboard design parameters on stability. The model’s skateboard-referenced frame facilitates its application to control system design.
Using the dynamics derived from the proposed skateboard-rider model, several nonlinear control laws are proposed. The goal of these control strategies is to neutralize the highspeed instability using common-mode and differential motor torque as control inputs. The effectiveness of these control laws is compared using time-domain simulations and region of attraction analysis. The final optimal control law is implemented and tested on an electric skateboard apparatus at a range of velocities in order to verify control performance and model accuracy.
When tested at low speeds, the control law is able to successfully stabilize the rider across a wide range of initial conditions, with experimental performance loosely aligning with the expected, simulated performance. High-speed testing was not conducted due to the safety concerns of the rider.