The class of mechanical control systems is interesting because (1) it provides a challenging collection of nonlinear control problems which possess enough structure that one can make some progress answering basic questions and (2) it contains many interesting examples. In this talk I shall present an approach for investigating mechanical control systems with "kinetic minus potential energy" Lagrangians, input forces which are dependent on configuration, and which (might) have nonholonomic constraints. To illustrate the efficacy of the methodology, I present some results concerning nonlinear controllability, along with a condition for the simplification of a given mechanical control system to a driftless control system.

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