A Reduced and Linearized High Fidelity Waveboard Multibody Model for Stability Analysis

In this paper, the stability of a waveboard, a human propelled two-wheeled vehicle consisting in two rotatable platforms, joined by a torsion bar and supported on two caster wheels, is analysed. A multibody model with holonomic and nonholonomic constraints is used to describe the system. The nonlinear equations of motion, which constitute a Differential-Algebraic system of equations (DAE system), are linearized along the steady forward motion resorting to a recently validated linearization procedure, which allows the maximum possible reduction of the linearized equations of motion of constrained multibody systems. The approach enables the generation of the Jacobian matrix in terms of the geometric and dynamic parameters of the multibody system, and the eigenvalues of the system are parameterized in terms of the design parameters. The resulting minimum set of linear equations leads to the elimination of spurious null eigenvalues, while retaining all the stability information in spite of the reduction of the Jacobian matrix. The linear stability results of the waveboard obtained in previous work are validated with this approach. The procedure shows an excellent computational efficiency with the waveboard, its utilization being highly advisable to linearize the equations of motion of complex constrained multibody systems.

Third-Order Differential-Algebraic Equations for Improved Integration of Multibody Dynamics

This paper introduces the concept of third-order differential-algebraic equations (DAE) for dynamics of constrained multibody systems. Third-order DAE provide jerk of components which can be integrated simultaneously with acceleration to provide improved simulation accuracy. A new Obreshkov predictor-corrector multistep integrator was developed to test this concept. Results from simulations of two planar mechanisms indicate that third-order DAE can reduce computation time by a factor of ten with equivalent accuracy compared to classical methods.