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System uncertainty can arise from a number of sources including disturbances, noise, unmodeled dynamics, and nonlinearities. Linear control design techniques typically neglect uncertainty in the system response. This may result in a reduction in performance or even instability of the closed loop system. The goal of this research is to account for measured uncertainty in control design. In contrast...
This paper presents development of a new controller that allows two or more hydraulically-actuated robots to cooperatively move a rigid object along a desired trajectory while sharing the load and maintaining an acceptable internal force on the object. The effects of friction (represented by LuGre model in this paper), as well as parametric uncertainties in the manipulators' dynamics, hydraulic functions...
In this paper, a hysteresis model-based nonlinear robust controller is developed for a piezoelectric actuator, utilizing a Lyapunov-based stability analysis, which ensures that a desired displacement trajectory is accurately tracked.
An aerodynamic property of lifting bodies called "ground effect", is used in the design of vehicles for a futuristic transportation system. Fundamental design issues associated with such a vehicle are discussed from first principles with a special emphasis on dynamics and control. Mathematical models of the dynamics of such a vehicle are presented and the inherent stability of the concept...
In this paper, closed-loop controller design involving brake, tire, road and actuator modeling complexities is considered. The closed-loop is separated in two parts; the inner loop is based on optimum braking algorithm by acting on individually actuated Antilock Brake Systems and the outer loop constitutes an optimal state feedback active steering design as an additional feedback loop to guarantee...
In this paper, we extend the previous TLO results for SISO trajecotory linearization observer (TLO) to MIMO nonlinear dynamic systems. Regular perturbation and nonlinear high-gain observer theories are applied to analyze the stability and robustness of the TLO method. The high-gain observer theory has been extended from time-invariant cases to time-varying cases using a singular perturbation approach...
The problem of model-based stabilization of a nonlinear system based on its approximate discrete-time model is addressed under the assumption that both the feedforward and the feedback paths are subject to network induced constraints. These constraints include irregularity of the transfer intervals, time-varying communication delays, and possibility of packet losses. A communication protocol that...
We analyse the control output feedback sensitivity function which results from imposing the minimal signal-to-noise ratio requirement needed for stabilisability. The signal to noise ratio constraint used here includes the effect of a band limited, additive coloured Gaussian noise communication link and a (non) minimum phase unstable continuous (discrete) linear time invariant (LTI) plant with time...
This paper investigates the stabilization problem for a class of nonlinear uncertain networked control systems (NCSs) with random communication time-delays. The nonlinear NCSs are described by a set of local linear systems which are combined using a Takagi-Sugeno model. Both sensor-to- controller and controller-to-actuator random network-induced delays are considered. Markov processes are using to...
This work addresses the important problem of stochastic resilience or non-fragility of a continuous-time Luenberger observer. This is the maintenance of convergence and/or performance when the observer gain is erroneously implemented due possibly to computational errors i.e. round off errors in computing the observer gain or changes in the observer parameters during operation. The error in the observer...
Stability conditions of networked multiple mobile agents in the face of stochastic communications failure are derived. Using a graph-theoretic approach, we provide stability analysis for the case where we employ zero-order hold sampled-data controller and the information of relative positions/velocities are unavailable for certain time instants at each agent. Finally, numerical examples are provided...
Large engineering systems exist, such as air traffic control and Internet routing, for which resources must be allocated amongst a few competitive agents with significant market power. Lump-sum market mechanisms are attractive for these resource allocation problems because the ability of individual agents to manipulate market prices has been shown to be limited. This work addresses the issue of convergence...
In this paper, we consider a class of uncertain dynamic nonlinear systems preceded by unknown backlash nonlinearity. The control design is achieved by introducing a smooth inverse function of the backlash and using it in the controller design with backstepping technique. For the design and implementation of the controller, no knowledge is assumed on the unknown system parameters. It is shown that...
This work considers the stabilization problem for unstable linear input-delay systems. The main idea of the paper is to use a finite-dimensional approximation for the delay operator, which is based on non-overlapping partitions of the time delay. Subsequently, each individual delay is approximated by means of a classical Pade approximation, resulting the overall approximation in a high-order Pade...
There has been increasing interest in the stability analysis and design problems of switched systems during the past two decades. In such problems, it is usually assumed that all subsystems have a common equilibrium. Recently, switched systems without common equilibria have been observed to exhibit similar convergent behavior under appropriate switching laws. Such behavior is called practical stability...
This paper considers the closed-loop stabilization problem for discrete-time linear switched system. The state variables are assumed to be not accessible so that the feedback strategy hinges on given output variables. The solution of this problem is based on the solution of suitable matrix inequalities for the construction of a full order switched filter and the derivation of the stabilization rule...
Many multi-agent coordinated behaviors can be achieved using decentralized estimation-and-control, where each agent uses limited communication with neighbors in a network to estimate global properties of the performance of the group. This global information is used in each agent's local motion controller, creating a feedback connection between the estimators and controllers. To ensure the stability...
We study a preloaded two-bar linkage that exhibits hysteresis due to the presence of multiple attracting equilibria. The dynamics at the unstable equilibrium, through which a snap-through buckle occurs, are not linearizable due to a singularity that is solution-dependent. We stabilize the unstable equilibrium using two distinct nonlinear controllers. The feedback linearization controller requires...
A new control strategy for the end- effector trajectory tracking (EETT) of a single flexible link manipulator (SFLM) is introduced. The linear dynamic model of the SFLM is expressed in the singularly perturbed form. To reduce the EETT error, a corrective torque is added to the "computed torque control" command of the rigid link counterpart of the SFLM. This corrective torque is derived based...
In this paper we consider distributed control of n dynamic agents to optimize an overall system performance metric. Due to limited communication resources, there exist structured interconnections among the agents and the design interest is placed in synthesizing a suitably distributed control law to provide a given performance level. Based on a Youla-Kucera parameterization approach, the problem of...
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