25,153 research outputs found
Nonlinear Receding-Horizon Control of Rigid Link Robot Manipulators
The approximate nonlinear receding-horizon control law is used to treat the
trajectory tracking control problem of rigid link robot manipulators. The
derived nonlinear predictive law uses a quadratic performance index of the
predicted tracking error and the predicted control effort. A key feature of
this control law is that, for their implementation, there is no need to perform
an online optimization, and asymptotic tracking of smooth reference
trajectories is guaranteed. It is shown that this controller achieves the
positions tracking objectives via link position measurements. The stability
convergence of the output tracking error to the origin is proved. To enhance
the robustness of the closed loop system with respect to payload uncertainties
and viscous friction, an integral action is introduced in the loop. A nonlinear
observer is used to estimate velocity. Simulation results for a two-link rigid
robot are performed to validate the performance of the proposed controller.
Keywords: receding-horizon control, nonlinear observer, robot manipulators,
integral action, robustness
Sensitivity analysis of hybrid systems with state jumps with application to trajectory tracking
This paper addresses the sensitivity analysis for hybrid systems with
discontinuous (jumping) state trajectories. We consider state-triggered jumps
in the state evolution, potentially accompanied by mode switching in the
control vector field as well. For a given trajectory with state jumps, we show
how to construct an approximation of a nearby perturbed trajectory
corresponding to a small variation of the initial condition and input. A major
complication in the construction of such an approximation is that, in general,
the jump times corresponding to a nearby perturbed trajectory are not equal to
those of the nominal one. The main contribution of this work is the development
of a notion of error to clarify in which sense the approximate trajectory is,
at each instant of time, a firstorder approximation of the perturbed
trajectory. This notion of error naturally finds application in the (local)
tracking problem of a time-varying reference trajectory of a hybrid system. To
illustrate the possible use of this new error definition in the context of
trajectory tracking, we outline how the standard linear trajectory tracking
control for nonlinear systems -based on linear quadratic regulator (LQR) theory
to compute the optimal feedback gain- could be generalized for hybrid systems
- …