摘要:

In this paper, we propose a robust control scheme for a free-floating space robot system where a robot arm is mounted on a free-floating base—a satellite, spacecraft or space station. The base is not controlled by external moments or forces. We model the system as an extended robot, including a pseudo-arm representing the base motion produced by six hypothetical passive joints, and a real robot arm. This model allows us to categorize the free-floating space robot system as a specific type of under-actuated system with mixed passive and active joints. We then discuss some fundamental properties of such a system. By means of an input-output linearization technique, we demonstrate that the internal dynamics of the system are nonlinear parametric and therefore, the control of the system using conventional robot control schemes is not feasible. To overcome the difficulty in controlling the internal dynamics subject to parameter uncertainty, and to avoid the measurement of the base acceleration, we develop a robust control scheme based on the second method of Lyapunov. We illustrate an example of a six-degrees-of-freedom space robot system to show the computational procedure and simulation results.

ISSN:0020-7179    

DOI:10.1080/00207179508921903

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Submarines operating at deep submergence can be considered to be in a disturbance-free environment. Under these conditions the design of depth-keeping controllers is a straightforward task. At shallow submergence under rough sea conditions and at low speed, accurate depth-keeping controller designs require particular attention. In these circumstances, the submarine is subject to severe disturbances, imposing additional restrictions on the designer. A submarine low-depth multivariable autopilot has been developed by applying classical Bode and Nyquist techniques. It is shown that a successful multivariable depth-keeping autopilot design can be produced using the framework of individual channel design. It is also shown that, the performance of the resulting linear fixed controller obtained, can be extended to a wide range of the submarine's operational envelope. This is achieved by considering the nonlinear effect of the speed on the nominal design. With such a modification, there is no need to implement a complex controller scheduling process. One advantage of the approach proposed here, is that the robustness of the multivariable control system can be stated in terms of actual gain and phase margins. The autopilot performance and robustness have also been assessed through a series of nonlinear simulations.

ISSN:0020-7179    

DOI:10.1080/00207179508921904

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A decoupled adaptive scheme is proposed for the trajectory control of robots. Under moderate constraints, the scheme is stable and robust in the presence of feedback delay and signal hold due to digital computation in the control loop. The design procedure involves a search for compensators with the aim of minimizing a quadratic performance index in order to minimize the maximum tracking error. Stability analysis of the proposed control law (the selected compensators) then provides stability bounds of disturbances, control and adaptation gains, and desired trajectories and their time-derivatives. The region of attraction is local due to unmodelled dynamics.

ISSN:0020-7179    

DOI:10.1080/00207179508921905

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Commutative controllers provide a convenient means for the systematic adjustment of the gain/phase characteristic of generalized Nyquist diagrams. Due to the irrational nature of the eigenvectors of transfer function matrices, practical commutative controllers are based on eigenvector approximations. This paper investigates the use of rational approximations, highlights stability difficulties that arise in connection with unstable fixed modes and derives the necessary and sufficient conditions that overcome these difficulties. The results of the paper are

ISSN:0020-7179    

DOI:10.1080/00207179508921906

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Aload processoris a system that has a buffer which can receive load and store it while it is waiting to be processed and has a local decision-making policy for determining if portions of its load should be sent to other load processors. Aload balancing systemis a set of such load processors that are connected in a network so that (i) they can sense the amount of load in the buffers of neighbouring processors and pass load to them, and (ii) so that, via local information and decisions by the individual load processors, the overall load in the entire network can be balanced. Such balancing is important to ensure that certain processors are not overloaded while others are left idle (i.e. load balancing helps avoid underutilization of processing resources). The topology of the network, delays in transporting and sensing load, types of load, and types of local load passing policies all affect the performance of the load balancing system. In this paper, we show how a variety of load balancing systems can be modelled in a discrete event system (DES) theoretic framework, and how balancing properties and performance can be characterized and analysed in a general Lyapunov stability theoretic framework.

ISSN:0020-7179    

DOI:10.1080/00207179508921907

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

his paper deals with residual generation for the diagnosis of faults in the presence of disturbances. The emphasis is on modelling errors, represented as multiplicative disturbances, and on parametric faults. These are both characterized as discrepancies in a set of underlying parameters. The residuals are obtained using parity equations. To address the situation when the number of uncertain parameters is too high to allow perfect decoupling, two approximate decoupling methods are introduced. One utilizes rank reduction of the model-error/fault entry matrix via singular value decomposition. The other minimizes a least squares performance index, formulated on the residuals, under a set of equality constraints. It is shown that, by the appropriate construction of the entry matrix or of the performance index and the constraints, a broad variety of structured and directional residual strategies can be implemented.

ISSN:0020-7179    

DOI:10.1080/00207179508921908

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Using the parameter-dependent Lyapunov function framework of Haddad and Bernstein this paper extends and connects some of the classical absolute stability results on discrete-time systems with monotonic and odd monotonic feedback nonlinearities to modern robust stability and performance problems for constant real parameter uncertainty. As in the continuous-time case, it is shown that an immediate application of this framework provides a generalization and reformulation of discrete-time mixedμtheory in terms of Lyapunov functions and Riccati equations while blendingH2robust performance within theμframework.

ISSN:0020-7179    

DOI:10.1080/00207179508921909

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The paper deals with the solution of the generalizedH∞. (GH∞) control problem in the presence of stochastic measurement noise and output disturbance. Because of the presence of the measurement noise, it is found that the problem cannot be solved, as in the zero measurement case, in a ‘one-shot’, but the so-called γ-iteration procedure is required to obtain the solution. The problem is approached by means of polynomial methods and the solution is achieved by solving standard polynomial diophantine equations and a single well-conditioned eigenvalue-vector problem, for whose solutions numerically reliable algorithms exist. An example of an application is given in order to show the effectiveness of the GH∞strategy in the case of very highly coloured measurement noise, with control and noise bandwidths overlapped.

ISSN:0020-7179    

DOI:10.1080/00207179508921910

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The 𝛍 analysis method is applied to a class of multivariable separable autonomous nonlinear feedback systems. The nonlinear element is replaced by its sinusoidal input describing function (SIDF) to develop a quasilinear nominal model for control analysis and design. Some properties of the ∞ -norm and structured singular values (SSVs) are shown to hold for the type of systems where the output is a function of control input-signal amplitude and frequency. The model uncertainty induced by the SDIF approximation is calculated and incorporated in the control design as an input multiplicative perturbation to the quasilinear nominal model. The 𝛍 analysis technique is then employed to study the stability and performance robustness of the nonlinear control system. Using small gain theorem, the condition for the absence of limit cycle is derived. The information obtained from this analysis is then used to design a bank of controllers using the H ∞ optimization-based 𝛍 synthesis technique. These controllers are designed such that the closed loop system is robust over a range of control-input amplitude. A simple scheme is then proposed to select the appropriate controller for the operating range. The simulation results illustrate that the proposed technique may be used to design a high performance robust controller for nonlinear systems and the absence of the limit cycle oscillation may be ensured.

ISSN:0020-7179    

DOI:10.1080/00207179508921911

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

This paper addresses the problem of relying on H2-optimization to select a controller that ensures satisfactory closed-loop responses to certain classes of persistent exogenous signals. Quadratic cost functionals are set up for each of the signal classes, corresponding to references, plant and measurement disturbances, which take into account the transient parts of the associated error and control signals. Each of the corresponding separate problems is shown to have unique solutions; this also holds for the problems obtained by combining these functionals in order to seek compromises between the objectives involved. The solutions of these problems are then quite explicitly described.

ISSN:0020-7179    

DOI:10.1080/00207179508921912

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor