9,831 research outputs found
A decentralized proportional-integral sliding mode tracking controller for a 2 D.O.F robot arm
Trajectory tracking with high accuracy is a very challenging topic in direct drive robot control. This is due to the nonlinearities and input couplings present in the dynamics of the arm. This paper deals with the tracking control of a class of direct-drive robot manipulators. A robust Proportional-Integral (PI) sliding mode control law is derived so that the robot trajectory tracks a desired trajectory as closely as possible despite the highly non-linear and coupled dynamics. The controller is designed using the decentralized approaches. Application to a two degree of freedom direct drive robot arm is considered
Discrete Robust Control of Robot Manipulators using an Uncertainty and Disturbance Estimator
This article presents the design of a robust observer based on the
discrete-time formulation of Uncertainty and Disturbance Estimator (UDE), a
well-known robust control technique, for the purpose of controlling robot
manipulators. The design results in a complete closed-loop, robust,
controller--observer structure. The observer incorporates the estimate of the
overall uncertainty associated with the plant, in order to mimic its dynamics,
and the control law is generated using an auxiliary error instead of state
tracking error. A detailed qualitative and quantitative stability analysis is
provided, and simulations are performed on the two-link robot manipulator
system. Further, a comparative study with well-known control strategies for
robot manipulators is presented. The results demonstrate the efficacy of the
proposed technique, with better tracking performance and lower control energy
compared to other strategies.Comment: 20 pages, 7 figures, 1 tabl
Robust control of robot manipulators using hybrid H∞/adaptive controller
A robust hybrid control method for robot manipulators is proposed which integrates an H∞ controller and an adaptive controller. The H∞ controller is used to minimize the effect of parameter uncertainties of the robot model on the tracking performance, while the adaptive controller continuously adjusts the model parameters to reduce the model error. Simulations show that disturbances generated from the model error will be quickly compensated and so small tracking errors can be achieved.published_or_final_versio
A Stability Analysis for the Acceleration-based Robust Position Control of Robot Manipulators via Disturbance Observer
This paper proposes a new nonlinear stability analysis for the
acceleration-based robust position control of robot manipulators by using
Disturbance Observer (DOb). It is shown that if the nominal inertia matrix is
properly tuned in the design of DOb, then the position error asymptotically
goes to zero in regulation control and is uniformly ultimately bounded in
trajectory tracking control. As the bandwidth of DOb and the nominal inertia
matrix are increased, the bound of error shrinks, i.e., the robust stability
and performance of the position control system are improved. However, neither
the bandwidth of DOb nor the nominal inertia matrix can be freely increased due
to practical design constraints, e.g., the robust position controller becomes
more noise sensitive when they are increased. The proposed stability analysis
provides insights regarding the dynamic behavior of DOb-based robust motion
control systems. It is theoretically and experimentally proved that
non-diagonal elements of the nominal inertia matrix are useful to improve the
stability and adjust the trade-off between the robustness and noise
sensitivity. The validity of the proposal is verified by simulation and
experimental results.Comment: 9 pages, 9 figures, Journa
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
An addendum on "Robust control of robots by the computed torque method"
We reinterprete and improve recent results on robust control of robots by the computed method. The methods and ideas used are inspired by `passivity based¿ control methods for robot manipulators and lead to a significant increase in freedom of controller implementation, thereby providing more flexibility to the designer of robot control systems
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Multiobjective control of a four-link flexible manipulator: A robust H∞ approach
Copyright [2002] IEEE. This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of Brunel University's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.This paper presents an approach to robust H∞ control of a real multilink flexible manipulator via regional pole assignment. We first show that the manipulator system can be approximated by a linear continuous uncertain model with exogenous disturbance input. The uncertainty occurring in an operating space is assumed to be norm-bounded and enter into both the system and control matrices. Then, a multiobjective simultaneous realization problem is studied. The purpose of this problem is to design a state feedback controller such that, for all admissible parameter uncertainties, the closed-loop system simultaneously satisfies both the prespecified H∞ norm constraint on the transfer function from the disturbance input to the system output and the prespecified circular pole constraint on the closed-loop system matrix. An algebraic parameterized approach is developed to characterize the existence conditions as well as the analytical expression of the desired controllers. Third, by comparing with the traditional linear quadratic regulator control method in the sense of robustness and tracking precision, we provide both the simulation and experimental results to demonstrate the effectiveness and advantages of the proposed approach
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