On the Gibbs-Appell Equations for the Dynamics of Rigid Bodies

In this technical brief, a simple concise derivation of the Gibbs-Appell equations for the dynamics of a constrained rigid body is presented.

Symmetry and Relative Equilibria of a Bicycle System

In this paper, we study the symmetry of a bicycle moving on a flat, level ground. Applying the Gibbs – Appell equations to the bicycle dynamics, we previously observed that the coefficients of these equations appeared to depend on the lean and steer angles only, and in one such equation, a term quadratic in the rear wheel’s angular velocity and a pseudoforce term would always vanish. These properties indeed arise from the symmetry of the bicycle system. From the point of view of the geometric mechanics, the bicycle’s configuration space is a trivial principal fiber bundle whose structure group plays the role of a symmetry group to keep the Lagrangian and constraint distribution invariant. We analyze the dimension relationship between the space of admissible velocities and the tangent space to the group orbit, and then employ the reduced nonholonomic Lagrange – d’Alembert equations to directly prove the previously observed properties of the bicycle dynamics. We then point out that the Gibbs – Appell equations give the local representative of the reduced dynamic system on the reduced constraint space, whose relative equilibria are related to the bicycle’s uniform upright straight or circular motion. Under the full rank condition of a Jacobian matrix, these relative equilibria are not isolated, but form several families of one-parameter solutions. Finally, we prove that these relative equilibria are Lyapunov (but not asymptotically) stable under certain conditions. However, an isolated asymptotically stable equilibrium may be achieved by restricting the system to an invariant manifold, which is the level set of the reduced constrained energy.

Virtual Work & d’Alembert’s Principle

This chapter discusses virtual work, returning to the Newtonian framework to derive the central Lagrange equation, using d’Alembert’s principle. It starts off with a discussion of generalised force, applied force and constraint force. Holonomic constraints and non-holonomic constraint equations are then investigated. The corresponding principles of Gauss (Gauss’s least constraint) and Jourdain are also documented and compared to d’Alembert’s approach before being generalised into the Mangeron–Deleanu principle. Kane’s equations are derived from Jourdain’s principle. The chapter closes with a detailed covering of the Gibbs–Appell equations as the most general equations in classical mechanics. Their reduction to Hamilton’s principle is examined and they are used to derive the Euler equations for rigid bodies. The chapter also discusses Hertz’s least curvature, the Gibbs function and Euler equations.

Computer simulation of the dynamics of systems of solids

The paper considers an algorithm for modeling the exact differential equations of the motion of systems of solids based on the Appell equations. To implement it, a multiple calculation of the energy of the system’s accelerations is required for different values of generalized velocities and accelerations.

Conformal Invariance and Conserved Quantity of Mei Symmetry for Appell Equations in a Holonomic System with Mass Variable

For a holonomic system with variable mass, the conformal invariance and the conserved quantity of Mei symmetry of Appell equations are investigated. First, by the infinitesimal one-parameter transformation group and the infinitesimal generator vector, the Mei symmetry and the conformal invariance of differential equations of motion for Appell equations in a holonomic system with variable mass are defined, and the determining equation of Mei symmetry and conformal invariance for Appell equations in a holonomic system with variable mass are given. Then, the Mei-conserved quantity corresponding to the system is derived by means of the structure equation to which the gauge function satisfies. Finally, an example is given to illustrate the application of the result.