Feedback Synthesis For Underactuated Systems Using Sequential Second-Order Needle Variations
This provides a method for controlling underactuated systems, which is incremental but addresses specific bottlenecks in nonlinear controllability.
The paper tackles the problem of synthesizing nonlinear feedback control for underactuated systems by using second-order needle variations, which enables control solutions when first-order methods fail, as demonstrated in simulations with vehicles like a differential drive cart and an underwater model showing convergence in a velocity field.
This paper derives nonlinear feedback control synthesis for general control affine systems using second-order actions---the second-order needle variations of optimal control---as the basis for choosing each control response to the current state. A second result of the paper is that the method provably exploits the nonlinear controllability of a system by virtue of an explicit dependence of the second-order needle variation on the Lie bracket between vector fields. As a result, each control decision necessarily decreases the objective when the system is nonlinearly controllable using first-order Lie brackets. Simulation results using a differential drive cart, an underactuated kinematic vehicle in three dimensions, and an underactuated dynamic model of an underwater vehicle demonstrate that the method finds control solutions when the first-order analysis is singular. Lastly, the underactuated dynamic underwater vehicle model demonstrates convergence even in the presence of a velocity field.