Search

We perform the seismic control experiment of a flexible structure in order to investigate applicability of the model set identification methods to robust controller design. From the viewpoint of application to robust control, we identify model sets based on nominal models represented by rational transfer functions, in contrary to most existing methods based on affinely parameterized functions which tend to be high order functions. Also, we derive a less conservative error bound which takes into account of low correlation properties of input signals. Based on the model set identification method and the H/sub /spl infin// controller design method based on LMIs, we show that a closed-loop system which satisfies given design specifications is obtained systematically.

The paper presents a new control method which achieves autonomous obstacle avoidance for manipulators with rate constraints. More precisely, in order to achieve the autonomous obstacle avoidance, we exploit the freedom of the coordinate transformation for feedback linearization of nonlinear control systems. At the same time, we cope with the rate constraints by adopting the state-dependent time scale transformation. Furthermore, we apply this method to an actual two-link robot manipulator, and evaluate its effectiveness by experiment, which is the most important part of the paper.

In this paper, we present a two-degree-of-freedom controller tuning for two-mass-spring systems with friction based on the iterative feedback tuning (IFT) approach. While two-mass-spring systems are widely used as fundamental components of the mechanical servo systems, they have sometimes severe friction. In order to cope with such cases, we adopt two strategies. One is the separate tuning of feedback and feedforward controllers. In particular, the feedback controller is tuned to achieve low sensitivity rather than tracking. The other is to introduce a quasi-Newton method into a parameter renewal law. The effectiveness of the proposed method is demonstrated through numerical simulations. Furthermore, we evaluate its effectiveness by experiments.

This paper is devoted to a unified approach to trajectory tracking control of nonholonomic port-controlled Hamiltonian systems via generalized canonical transformations. The key idea is to construct an error system, which describes the dynamics of the tracking error, by a passive port-controlled Hamiltonian system. This strategy works for both holonomic and nonholonomic port-controlled Hamiltonian systems. A practical design procedure of global tracking controllers for those systems is proposed. This method is a natural extension of the conventional passivity based control and is expected to derive robustly stable control systems.

Proposes a method to generate modified reference signals for closed loop systems so as not to violate the input and state constraints of the plants. In particular, improvement of the output response is taken into account explicitly subject to the given constraints, and the method is computationally efficient because of LMI formulae. The effectiveness of the proposed method is evaluated by simulation.

The paper is concerned with the stabilization of nonholonomic systems in port-controlled Hamiltonian formulae via generalized canonical transformations. A special class of time-varying generalized canonical transformations are introduced which preserves the passivity property. Utilizing this transformation time-varying asymptotically stabilizing controllers for the nonholonomic Hamiltonian systems are derived. The proposed method is a natural generalization of passivity based control since we only employ the feedback which preserves the Hamiltonian structure of the original system.

This paper proposes a nonlinear control method for magnetic suspension systems, which combines linear H/sub /spl infin// control methodology with the control Lyapunov function (CLF) approach. The linear controller is designed by taking into account of given control specifications around the equilibrium point, and then an appropriate CLF based nonlinear compensation ensures the global stability with least efforts. The latter is designed not to work near the equilibrium point in order to enhance the merit of linear controller. The effectiveness of the proposed method is demonstrated by simulation.

This paper presents a tuning method of feedback controllers for the optimization of quadratic cost functions via Iterative Feedback Tuning (IFT), where we do not need any model of the plant to be controlled. First, we propose an IFT method in a generalized setting, where the systems are represented by Linear Fractional Transformation (LFT). Several merits of this problem setting are pointed out. Next, comparing the optimization in IFT with the iteration-based numerical computation method of the Riccati equation, we clarify some properties of the IFT method. In addition, we point out that if a certain condition is satisfied, the optimization problem in IFT becomes convex and we show how to obtain a new design parameters with I/O data only. Finally, a numerical example is given to demonstrate the usefulness of the proposed method.

This paper is concerned with the asymptotic stabilization of nonholonomic systems which are in generalized Hamiltonian formulae. First, it is shown that such systems can be transformed into canonical forms which have specified structure matrices via generalized canonical transformations. Then a concrete method to construct a non-smooth Hamiltonian function which renders the feedback system asymptotically stable is shown. Some numerical examples are also given to show the effectiveness of our technique.

This paper provides a μ analysis and synthesis method of state feedback systems. First, we derive a sufficient condition for the dynamical system to have μ less than a specified value γ by using parameter-dependent multipliers and the positive real lemma. It requires no higher order multiplier and no frequency sweep while being less conservative than former methods. Second, based on this result, we give an LMI condition for the existence of a state feedback gain which achieves that μ of the closed loop system is less than given γ. Finally, an illustrative numerical example is given.

The authors propose a controller design method for coordinative manipulation by multiple robot manipulators in which both the dynamics of the manipulator and the dynamics of the object are taken into account. In particular, the vector defined from the contact points between the object and the manipulators is adopted to express the orientation of the object globally. The proposed control system achieves the object trajectory tracking with appropriate grasping forces. Furthermore, a method for controlling the posture of the manipulators by using kinematic redundancy subject to the coordinative manipulation is presented. >

Most of the previous studies on inverse systems have treated only the case where all components of the input of the original system are recoverable. However, even when not all components are recoverable, there is still a possibility of reproducing part of the input. As a generalization of the inverse of a linear time-invariant dynamical system to include such cases, '@a-integral F-inverse' is proposed in this paper which reproduces the @ath integral of a linear function Fu of the input vector u. A necessary and sufficient condition for the existence of an @a-integral F-inverse is derived. A construction procedure of such an inverse is also given along with a numerical example.

This paper is concerned with a test for robust stability. In order to overcome the conservativeness of usual stability test based on the small gain theorem, a new graphical test is introduced for robust stability of scalar systems, which takes account of both gain and phase information. The method is then extended to a class of multivariable systems.

The robust tracking problem in two-degree-of freedom control systems is formulated in a general setting, which includes the case where the controlled output is not available directly. A complete solution of the problem, which is an extension of previous results, is derived in a considerably simplified and transparent manner. Furthermore we show what kind of information about the output is needed to achieve robust tracking.

本論文は2本のマニピュレータによる2次元空間内の物体の協調的操りに関するものである.マニピュレータによって物体を正確だ操るためには, マニピュレータの動特性だけでなく対象物体の運動も考慮にいれる必要がある.そこで, まず, マニピュレータと物体両方の動特性を考慮にいれた上で, 2次元空間における2本のマニピュレータによる協調的操り制御のための基礎方程式を導出する.ここでは特に物体の姿勢を表すのに, オイラー角やロール・ピッチ・ヨー角などの従来の表現のかわりに簡単なベクトルを用いる.次にこの基礎方程式に基づいて, 物体の所望の位置と姿勢を独立に達成するような制御系を既存の拘束条件付き制御法を応用して設計する.最後にシミュレーションによって本制御法の有効性を示す.

In this paper we study multivariate tracking systems considering sensor dynamics. Firstly, we discuss the relation between internal models and sensor dynamics in tracking systems in order to obtain some insight into servo system synthesis. Secondly, we clarify a condition on plant and sensor under which robust control can be achieved. Finally, we propose a synthesis procedure for tracking systems with a compensation scheme for sensor dynamics, and give a numerical example.

An approach to designing controllers for dynamic hybrid position/force control of robot manipulators is presented, and preliminary experimental results are given. Dynamic hybrid control is an extension of an approach proposed by M.H. Raibert and J.J. Craig (1981) to the case where the full manipulator dynamics is taken into consideration and the end-effector constraint is explicitly given by the constraint hypersurfaces. This design method consists of two steps. The first step is the linearization of the manipulator dynamics by nonlinear state feedback. Formulation of the constraint by the constraint hypersurfaces plays an essential role in establishing the linearizing law. The second step is the design of position and force controllers for the linearized model using the concept of two-degrees-of-freedom servocontroller. The merit of this servocontroller is that it can take account of both the command response and the robustness of the controllers to modeling errors and disturbances. Preliminary experiments using a SCARA robot show the validity of the approach. >

In this paper we study linear time-invariant multivariable systems in which the compensators consist of both feedforward and feedback parts. Firstly, a necessary and sufficient condition for the system to be an internally stable robust tracking system is obtained. Secondly, the class of attainable transfer matrices from reference signal to plant output of internally stable robust tracking systems is clarified. Thirdly, a simple method is proposed for specifying two feedback properties, i.e., sensitivity and stability margin. Finally, based on these results, we propose a synthesis procedure of robust tracking systems with desirable transient responses, sensitivity and stability margin

This paper proposes a new doubly coprime factorization technique which forms a basis of algebraic control theory. This enables us to generalize a previous result on doubly coprime factorization. Furthermore, it is shown that all stabilizing compensators possess a simple model-reference structure.

In this note, we study linear time-invariant multivariable systems with two-degree-of-freedom compensators. First, we give a new parametrization of all stabilizing compensators from the viewpoint of independent design of transfer function and robustness property. Second, utilizing this parametrization, we solve a general robust tracking problem including the case of nonsquare plants, and show that "tracking" and "robustness" can be independently specified in two-degree-of-freedom control systems.

Servo problems taking into consideration the sensor dynamics are considered in the transfer matrix setting. As a preparation, we propose a new definition of internal stability, and derive a few properties of this stability. Secondly, necessary and sufficient conditions for a stable system with sensor to have tracking, robust tracking, regulation, and robust regulation capability are obtained. In order to verify the validity of usual servo system synthesis methods which utilize internal models and to have insight into servo synthesis, the relation between internal models and sensor dynamics are considered in detail.

Based on the analysis of error convergence in digital learning control systems subject to measurement noise and input saturation, a new practical design method of learning control system is proposed which achieves tracking for uncertain systems through the repetition of trials over a fixed time interval.

This paper proposes a robust control law which achieves desired command response with prescribed accuracy for uncertain nonlinear robot manipulators. The distinguish feature of our method is that (i) tracking accuracy, (ii) desired command response, and (iii) desired initial error response can be achieved simultaneously without the precise knowledge of manipulator dynamics.

This article is concerned with robust control of robot manip ulators in the case where joint torque sensors are available. First, we derive a dynamic equation of the manipulator with joint torque sensors that explicitly expresses a nonlinear mul tivariable structure. This dynamic equation makes it possible to construct the control systems of the manipulators with joint torque sensors based on a similar method used in the conven tional case without the sensors. Second. based on this dynamic equation, we propose a robust trajectory control scheme that achieves the specified tracking accuracy in the presence of modeling error, including the modeling error of actuator sys tems. The proposed method fully exploits joint torque sensor information to compensate the uncertainty of link and load parameters. Furthermore, an illustrative simulation result is given to show the effectiveness of the proposed control method.

This paper deals with a trajectory tracking problem of a class of bimodal piecewise affine systems, which have rarely been discussed so far. This would be very challenging because of the discontinuous changes of their vector fields. First, we introduce an error variable and an error system as a generalization of the tracking error and its system. As an error variable, a function switched by the mode of a piecewise affine system is adopted to overcome an inherent difficulty in trajectory tracking of piecewise affine systems. Next, we design a tracking controller which stabilizes the error system using a Lyapunov-like function, which can be applied to systems including state jumps. Finally, a numerical example is given to illustrate the effectiveness of the proposed method.