Discrete Model Reference Adaptive Control Research Articles

Global Lyapunov stability and exponential convergence of direct adaptive control

The stability properties of discrete time model reference adaptive control systems are examined. Lyapunov functions and strong convergence results are given for some classes of adaptive systems. We show l 2-stability, Lyapunov stability, and finite time convergence for a set of tracking error states.

Discrete Time Model Reference Adaptive Control of an Industrial Manipulator’s Waist Joint

The current control systems adopted by most industrial manipulators are “open loop” designs based only upon kinematic consideration. Their servo gains are fixed and there is no flexibility of updating them. It is desirable, therefore, to have a robot control system that adapts to its payload and manipulator configuration in order to maintain optimal dynamic performance throughout the robot workspace, and regardless of the payload. This paper implements and evaluates the discrete time model reference adaptive control (MRAC) algorithm of robot control proposed by Horowitz and Tomizuka to a PUMA 560 industrial robot. Its original controller was overridden and the individual joint axes are controlled by a separate computer. This study shows the adaptive controller can maintain fast, consistent response regardless of the arm configuration.

Discrete Stable Model Reference Adaptive Control in the Presence of Unmodeled Dynamics

Abstract A standard adaptive control algorithm is modified using a time-dependent deat-beat parameter-adaptive structure. Under certain weakness assumptions about the influence of the unmodelled plant parameters on the response, stability of the overall scheme is guaranteed.

An Auto-Pilot System Design Using Reduced Order Model Reference Adaptive Control

In this paper, the singularly-perturbed design of an auto-pilot system of a high speed fighter aircraft, for the same authors (1985), is modified. The previous suboptimal design based on singular perturbation technique was proper only for aircraft operation near its nominal flight conditions. The new proposed adaptive design would be adequate for all possible changes of aircraft dynamics. The plant with varying parameters, representing aircraft, is controlled to behave nearly similar to a chosen first order reference model. The proposed discrete model reference adaptive control design uses an adaptive algorithm of Suzuki and Takashima (1978), based on augmented error signal concept and Popov's hyperstability theorem. Computer simulation results are presented to demonstrate the usefulness of the proposed design.

A stable adaptive control design for discrete plants with unmodelled dynamics

This paper presents a simple discrete model reference adaptive control design which maintains stability around the equilibrium of the tracking error in the presence of unmodelled dynamics. Only a weak a priori knowledge (namely, upper bounds of the absolute value of the unmodelled parameters and orders of the unmodelled dynamics) is required for the implementation. The adaptive controller has an additional parameter to protect the scheme against instability.

Rapprochement between continuous and discrete model reference adaptive control

In the literature to date there is a dichotomy between results on continuous- and discrete-time model reference control. This is highlighted in the case of continuous-time systems having relative degree greater than one. It is known that, for rapid sampling, these systems always give rise to a non-stably invertible discrete-time system and thus discrete model reference control is ruled out. On the other hand, there are many results pertaining to continuous-time model reference control of such systems. This apparent paradox can be resolved by a slight modification to the discrete-time model format as shown later. This alternative model is used to develop a new discrete model reference adaptive control law and a convergence analysis for the algorithm is presented.

Discrete model-reference adaptive control using only input and output measurements

A globally stable discrete model-reference adaptive controller design using only input and output measurements is presented. The rejection of both measurable and unmeasurable load disturbances is included in the adaptive system. The use of state-variable filters ensures that the basic scheme is applicable to a process with moderate measurement noise. With large measurement noise, an extended scheme using the technique of instrumental variable is introduced. The performance of these designs is substantiated by simulation.

未知確定外乱を考慮した離散時間モデル規範形適応制御

未知確定外乱を考慮した離散時間モデル規範形適応制御

ON THE IMPROVEMENT OF THE ADAPTATION TRANSIENTS IN ADAPTIVE CONTROL

Abstract A technique to improve the adaptation transient in discrete time Model Reference Adaptive Control (MRAC) systems is given on the basis of applying classical optimization techniques to an equivalent near-linear system to the whole adaptive scheme. The resulting optimization is finally translated into modifications of one of the parameters entering the adaptation algorithm. This allows to compute “a posteriori” values of the adaptive controller parameters previously to the generation of the input to the plant.

A Discrete Time Multivariable Model Reference Adaptive Control Algorithm with Application to a Real Plant

A practical method for designing a discrete time multivariable model reference adaptive control system is presented. This method is applicable to a real plant which lias the non-minimum phase characteristics. Moreover, in the proposed method, the restriction of the amplitude of the plant input and an unknown deterministic disturbunce are taken into consideration, and the fast convergence is attained using an appropriate plant representation and an adaptation algorithm. In order to illustrate the effectiveness of the proposed method, computer simulation and on-line computer experiments are carried out using the plant testing the performance of refrigerant compressors. It is shown that the proposed method can be successfully applied.

未知むだ時間系に対する離散値モデル規範形適応制御系の一設計

未知むだ時間系に対する離散値モデル規範形適応制御系の一設計

Noninvertible Digital Transfer Functions Arising From Minimum Phase Analog Process Models

Current approaches to discrete model reference adaptive control (MRAC) [1–6] require the inverse of the discretized process model to achieve the desired model following. The objective of this paper is to illustrate that the step-invariant transformation of a minimum phase, physical analog process model (based upon a machine tool position controller) leads to a nonminimum phase discrete-time model and thus precludes the possibility of obtaining a stable inverse for the discrete-time process model. This example illustrates the shortcomings of applying discrete MRAC to higher-order processes and indicates the need for alternative MRAC approaches which do not require the adaptive cancellation of process zeros.

拡張誤差を用いない直接法離散時間MRACSの一般的構造と漸近安定性

拡張誤差を用いない直接法離散時間MRACSの一般的構造と漸近安定性

A discrete model reference adaptive control system for a plant with input amplitude constraints

This paper considers the stability of a model reference adaptive control system with input amplitude constraints. The conditions given in this paper guarantee the stability of the error between the plant output and the reference sequence. The validity of the theoretical results is demonstrated by numerical examples.

A Discrete Model Reference Adaptive Control Using an Autoregressive Model with Dead Time of the Plant

A new method for designing a discrete model reference adaptive control system is presented. This method avoids the restriction of the minimum phase system by the adaptive controller designed for an autoregressive model with dead time of the plant. First, a stable adaptive control system is designed for an AR model with dead time, based on Lyapunov's direct method. The derived adaptation control algorithm can be implemented using only the available input-output data of the plant. Next, in order to illustrate the effectiveness of this model for many different types of plants, the results of computer simulation are given. Finally, the design parameters of the model are discussed.

Direct and indirect schemes for discrete model reference adaptive control systems

Direct and indirect schemes for discrete model reference adaptive control systems

Unification of discrete time explicit model reference adaptive control designs

Various discrete time explicit MRAC designs based on stability considerations are presented from a unified point of view. A general structure and a design procedure are given, which contain as particular cases various possible designs. Some of these designs have been already given in the literature but some are new. The general structure considered removes some of the restrictions encountered in previous designs and solves the important problem of independent specification of tracking and regulation objectives. The proof of boundedness of the control variables is also given. Simulations are included in order to evaluate the various designs in a deterministic environment.

Redesign of explicit and implicit discrete time model reference adaptive control schemes

The design of MRAC for achieving independent tracking and regulation objectives with a unique equilibrium point in the controller parameter space is presented. The corresponding schemes can use either an explicit reference model or an implicit reference model. The design is done from a stability point of view by extending an appropriate control configuration used for the case of known plant parameters. The result of the design is a simple control scheme using a linear constant feedforward controller and a non-linear feedback controller. The stability of the system and boundness of various variables do not require any positivity condition. The performances of the control structure in tracking and regulation are evaluated by simulations.

非最小位相系に対する離散時間モデル規範形適応制御系の一設計法

非最小位相系に対する離散時間モデル規範形適応制御系の一設計法

Direct and Indirect Schemes for Discrete Model Reference Adaptive Control Systems

Direct and Indirect Schemes for Discrete Model Reference Adaptive Control Systems