摘要:

This paper deals with the hierarchical control of a class of robot manipulators. A two-level hierarchical control concept for robot manipulators is proposed. The controller is formulated based on a deterministic approach. In synthesizing the controller, it is assumed that the upper bounds on the nonlinearities, couplings and uncertainties present in the system are available. It is shown through computer simulations that the proposed control strategy is capable of withstanding the expected variations and uncertainties in the system, and will render the robot manipulator able to track a prescribed trajectory to within a small ultimate boundedness set.

ISSN:0020-7179    

DOI:10.1080/00207179508921952

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In this note, the structured H2optimization problem is defined and two methods are outlined for its solution. The first method involves a vectorization/ Kronecker product technique and reduces the optimization problem to two nested projections. To circumvent the dimension inflation implicit in this method, an iterative algorithm is proposed as an alternative. This is an application of von-Neumann's alternating projection algorithm in Hilbert space and can be shown to be applicable to the present problem under two standard rank assumptions. A short version of this paper has appeared in Halikias (1993).

ISSN:0020-7179    

DOI:10.1080/00207179508921953

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The linear continuous-time systems to be discussed are described by state space models with structured time-varying uncertainties. First, the explicit maximal perturbation bound for maintaining quadratic Lyapunov stability of the closed-loop systems is presented. Then, a robust design method is proposed. Given an open-loop, nominal system with information of the uncertainty structure, the proposed robust design method produces a linear constant output feedback control law which maximizes the perturbation bound for maintaining quadratic Lyapunov stability. Both the optimal results for robust analysis and robustness design can be obtained by using an efficient numerical algorithm (e.g. minimax of MATLAB) with analytic gradients given in this paper. Examples are investigated in some detail to show the improvements and advantages of the proposed methods over previous ones.

ISSN:0020-7179    

DOI:10.1080/00207179508921954

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper discusses the use of multi-layer perceptron networks for linear or linearizable, adaptive feedback control schemes in a discrete-time environment. A close look is taken at the model structure selected and the extent of the resulting parametrization. A comparison is made with standard, non-perceptron algorithms, e.g. self-tuning control, and it is shown how gross over-parametrization can occur in the neural network case. Because of the resultant heavy computational burden and poor controller convergence, a strong case is made against the use of neural networks for discrete-time linear control.

ISSN:0020-7179    

DOI:10.1080/00207179508921955

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A new repetitive control method is presented for semi-active vibration control of machines, such as presses and forge hammers, that are subject to nearly periodic disturbances with known periods. The vibration of the machine is controlled by actuators consisting of a proof mass, a spring, and a damper with variable damping coefficients that are treated as control inputs. The system is approximated by a bilinear state equation involving products of state variables and control inputs. Using optimal control theory a control input vector is synthesized which minimizes an objective function that trades-off the quality of isolation against relative motions of the proof masses and accounts for inequality constraints on the control inputs. The optimal control law calls for a full state feedback and feedforward of a variable dependent on future disturbances. It is therefore proposed to estimate the system disturbance based on measurements from the most recent period and, assuming the disturbance to be repetitive, to use this estimate as a predicted disturbance for the consecutive period. An observer for simultaneous estimation of the state and the disturbance is developed. Although intended for a particular application, the repetitive control theory developed in this paper is general and can be applied to other systems described by bilinear state equations. The results of simulations for a two degree-of-freedom model representing a machine with a semi-active vibration absorber and for a simple distributed parameter structure illustrate the proposed approach.

ISSN:0020-7179    

DOI:10.1080/00207179508921956

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper considers designs of decentralized controllers for continuous-time linear time-invariant multivariable control systems. The purpose is to show how to attain robust stability and robust performance of decentralized control systems by sequential design procedure. Compared with independent designs in which each controller block is designed independently of others, sequential designs can reduce conservatism associated with the controller design since they can exploit information about the other loops which have been already designed. A novel method of sequential designs for the robust performance are proposed. Moreover, an approach to a kind of failure tolerance is considered. The proposed sequential design procedure is based on expanding construction of decentralized control systems, so that the proposed methods can deal with extension of subsystems.

ISSN:0020-7179    

DOI:10.1080/00207179508921957

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

In this paper, we set a new framework for the analysis of nonlinear discrete systems, to carry out the stabilization theorem, and to design stable controllers of the systems within that framework. This framework includes many practically important systems—described, for example, by Lipschitz functions, functions with arbitrary order bounded derivatives, bilinear functions and all polynomial functions. An important existence theorem for stabilizing has been proven for this framework. The theorem basically states that under definite, rather broad conditions, the zero solution of the plants can be made stable by a nonlinear output feedback. In addition, this nonlinear feedback is from a larger class of functions than these classes given by current literature. Following these stabilization theorems, a new design procedure for the output feedback control law is presented. All results presented are easy to use and convenient to apply. The application is illustrated by several examples, including the design of stabilizing control for a bilinear control system.

ISSN:0020-7179    

DOI:10.1080/00207179508921958

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We introduce flat systems, which are equivalent to linear ones via a special type of feedback called endogenous. Their physical properties are subsumed by a linearizing output and they might be regarded as providing another nonlinear extension of Kalman's controllability. The distance to flatness is measured by a non-negative integer, the defect. We utilize differential algebra where flatness- and defect are best defined without distinguishing between input, state, output and other variables. Many realistic classes of examples are flat. We treat two popular ones: the crane and the car withntrailers, the motion planning of which is obtained via elementary properties of plane curves. The three non-flat examples, the simple, double and variable length pendulums, are borrowed from non-linear physics. A high frequency control strategy is proposed such that the averaged systems become flat.

ISSN:0020-7179    

DOI:10.1080/00207179508921959

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We design decentralized controls for interconnected non-linear dynamical systems with uncertainties. This uncertainty is (possibly fast) time-varying. It may appear in each system as uncertain parameter and input disturbance. It also may appear in the interconnections. No statistical information about the uncertainty is imposed; only its possible bound is assumed to be known. The design takes the interconnections into explicit account. That is, the interconnections are to be compensated rather than to be tolerated. Under a mild assumption, interconnections with arbitrary non-linear bound can be addressed. This renders all previous works on this theme as special cases.

ISSN:0020-7179    

DOI:10.1080/00207179508921960

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

There is a well-developed theory describing inherent design limitations for linear time invariant feedback systems consisting of an analogue plant and analogue controller. This theory describes limitations on achievable performance present when the plant has non-minimum phase zeros, unstable poles, and/or time delays. The parallel theory for linear time invariant discrete time systems is less interesting because it describes system behaviour only at sampling instants. This paper develops a theory of design limitations for sampled-data feedback systems wherein the response of theanaloguesystem output is considered. This is done using the fact that the steady-state response of a hybrid feedback system to a sinusoidal input consists of a fundamental component at the frequency of the input together with infinitely many harmonics at frequencies spaced integer multiples of the sampling frequency away from the fundamental. This fact allows fundamental sensitivity and complementary sensitivity functions that relate the fundamental component of the response to the input signal to be defined. These sensitivity and complementary sensitivity functions must satisfy integral relations analogous to the Bode and Poisson integrals for purely analogue systems. The relations show, for example, that design limitations due to non-minimum phase zeros of the analogue plant constrain the response of the sampled-data feedback system regardless of whether the discretized system is minimum phase and independently of the choice of hold function.

ISSN:0020-7179    

DOI:10.1080/00207179508921961

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor