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This paper is aimed at presenting a framework that consists of a pattern generator and a controller, which are combined together to realize continuous and dynamically equilibrated running motion on a 4-link 3-DoF one-legged robot with no passively compliant elements. Initially, we make use of a pattern generator to synthesize dynamically-consistent running trajectories in which the rotational inertia and the associated angular momentum term are characterized. As for the controller, ground reaction force constraints are imposed to the system indirectly. For this purpose, joint torque values that are corresponding to horizontal and vertical force errors are computed. Subsequently, they are inserted to an admittance filter block to obtain the associated joint displacements. These joint displacements are then fed-back to local servo controllers to implement indirect force feedback control in an actively compliant manner. Additionally, friction compensation and foot orientation controller blocks are added to enhance the system performance. In order to validate the method, running experiments are conducted on the actual one-legged robot. As the result, we satisfactorily obtained continuous, dynamically equilibrated and repetitive running cycles.

Stabilization of polynomial systems is revisited in this paper. Here, we proposed a new sufficient condition for the controller design, with guaranteed bounds on the input magnitudes. In the proposed synthesis condition, the system matrices and the Lyapunov matrices are separated, and hence parameterization of the resulting controller is independent of the Lyapunov matrices. Moreover, the proposed condition is convex in the decision variables and solvable via the sum-of-squares (SOS) technique. Main contributions of the proposed approach are twofold. Firstly, parameter-dependent Lyapunov functions can be considered in robust controller design for uncertain polynomial systems. Secondly, static output-feedback design can be addressed in a computationally efficient manner.

This paper is aimed at describing a framework to implement sensorless torque estimation and control in wearable exoskeletons, for the purpose of handling power augmentation tasks. The proposed method relies on accurately identifying and compensating the joint-level disturbance torques caused by stiction, viscous friction, and gravitational loads. Utilizing off-the-shelf techniques, the characteristics of these disturbances are primarily identified. Subsequently, additional torque inputs are superimposed to the system via feedforward loops in a way to counteract to these disturbances. Having compensated frictional and gravitational loads acting on the actuation module; we are able to estimate the external torque exerted at each joint by using disturbance observers. In this manner, torque control is enabled without any requirement of built-in torque sensing units. In order to validate the proposed framework, we conducted weight lifting and upholding experiments on able-bodied human subjects with and without wearing the upper extremity of exoskeleton suit. Comparison of EMG and IEMG signals acquired in two cases indicates that the exoskeleton system provides sufficient power augmentation reliably. In conclusion, the proposed method is validated to be efficient and it can be potentially used for rehabilitation, training and power augmentation tasks.

This work presents a new theoretical approach to hybrid position/force control. It develops a method for the design of controllers of constrained manipulators. In this work also the robustness considerations are given. It can be shown that the proposed control system has robustness properties for a class of dynamic uncertainties. In order to improve the robustness property integral controller is applied to the force control loop. The usefulness of this hybrid control system is demonstrated through simulations of a constrained two degrees of freedom robot manipulator.

A mobile manipulator is a class of mobile robot on which the multi-link manipulator is mounted. This system is expected to play an important role both in the production process of factory and in the medical care system of welfare business. To come up to this expectation, a mobile manipulator is required to simultaneously track to both the desired position trajectory and force trajectory. However, these tracking performances are subject to nonholonomic and holonomic constraints. Furthermore, mobile manipulators possess complex and strongly coupled dynamics of mobile bases and manipulators. Then, there are very few studies on the problems of stabilization position/force control for mobile manipulators. In (Chang & Chen, 2002; Oya et al., 2003; Su et al., 1999), position and force control methods for mobile robot without manipulators have been addressed. Since in these studies holonomic constraints representing the interaction between end-effector of the manipulator and environment have not been considered, those approaches could not be applied to the position/force control problems of the mobile manipulators. In (Dong, 2002; Li et al., 2007; 2008), adaptive and robust control approaches have been applied to the position/force control problems of the mobile manipulators. In these approaches, since the chained form transforms are required, synthesismethods of the control torques and adaptation laws of these approaches are too complicated to apply. On the other hand, we have derived the stabilizing controllers for a class of mobile manipulators(Narikiyo et al., 2008). In (Narikiyo et al., 2008) we have proposed robust adaptive control scheme for the system with dynamic uncertainties and external disturbances directly from the reduced order dynamics subject to both the holonomic and nonholonomic constraints. Furthermore, in (Narikiyo et al., 2009) we have developed this control scheme to control the system with both kinematic and dynamic uncertainties. In these studies usefulness of these control schemes have been demonstrated by numerical examples. However, proof of the closed loop stability has not been completed under an inadequate assumption(Narikiyo et al., 2009). In this study we complete the proof and relax the assumptions of (Narikiyo et al., 2009). Then we implement these control schemes (Narikiyo et al., 2008; 2009) experimentally and apply to the prototype shown in Fig.1 to demonstrate the effectiveness of these proposed control schemes. It is also guaranteed theoretically that the tracking position and force errors to the desired trajectories are asymptotically converged to zero by the proposed control schemes. 7

Recently an industrial multi-link robot is expected to be applied to precision machining. However, the multi-link robot manipulators are highly coupled non-linear systems and their equations of motions are hardly identified. Therefore it has been thought that precision machining using a multi-link robot is impossible. In this paper, a new type of precision machining robot in proposed. This robot consists of a multi-link robot and the machining unit for micro-positioning. The control system of this robot is modelled as the singular perturbed system and is applied to the position control and electric discharge machining (EDM) control.

Various types of linear motor have been developed. However, most of them are only applied to positioning control. High compliance property of the linear motor has not been used effectively. Then there are few types of linear motor which can be applied to manufacturing unit.In this study, we developed a differential linear motor which has some advantages suitable for manufacturing unit. The new type of the linear motor has been expected to be applied not only to positioning unit but also to active compliance unit of robot manipulators. Therefore, we applied pseudo diagonalization method to the position and compliance control of the developed differential linear motor. In the position control part dither signal was used after diagonalization. Amplitude of the dither signal was modified by error signals. In the compliance control part PID controller was used. The effectiveness of the proposed control system was shown through experiments.

Pneumatic actuators are less expensive and have higher power/weight ratio than other types of actuators. On the other hand, it is very difficult to control the pneumatic actuators because of uncertainties caused by the nonlinear pneumatic circuit and large friction caused by mechanical contact between piston-ring and cylinder. Then the pneumatic actuator has hardly applied to precise positioning and smooth drive control.In this paper we applied optimal control theory and model feedback control scheme to control of the pneumatic cylinder in order to realize both the precise positioning and the smooth driving. The effectiveness of the proposed control system is shown through experiments. Results of these experiments are compared with the results which were carried out by fuzzy control logic.

This work presents a new robust control methodology for hybrid position/force control. The control input of this methodology consists of a nonlinear and a linear part. The nonlinear control part gives a new coordinate system. Using this coordinate system. robot dynamics is decoupled and input spaces are divided into two orthogonal spaces of position and force control. The linear control part improves robustness properties of the nonlinear hybrid control scheme. A model feedback control scheme is applied to the linear part or position control and integral control is used in the linear part of force control. The robustness properties of the nonlinear robust hybrid control algorithm are demonstrated through simulation of a constrained two degrees of freedom robot manipulator.

In this paper we study the robust D-stability of single-parameter polynomially-dependent matrices. D-stability of a matrix means that all the eigenvalues are in a prescribed open region, which is symmetric with respect to the real axis in the complex plane. We propose a method based on generalization of the stability feeler. By using this method, we can obtain complete D-stability intervals for a class of single-parameter polynomially-dependent matrices. This method does not require that a nominal matrix is stable. Moreover, we show an application to the analysis of robust D-stability in a physically motivated example.

Robust semidefinite programs (robust SDPs in short) with functional variables are revisited in this paper. We firstly consider the approximate approach suggested by Jennawasin and Oishi (in Proceedings of the 17th IFAC World Congress, Seoul, Korea, July 2008), and then provide a numerically computable condition to verify when the optimal value of an approximate problem is actually equal to that of the original robust SDP. The idea is based on capturing some special structure of a dual feasible solution of the approximate problem.

A study is presented of measuring method for flat form errors by 2D least square serial 3point method. This method is extensively improved on a serial 3point method. Consequently, this approach can compensate the measuring errors which are caused by fluctuations of 9 displacement sensors implemented on a measuring head. Here, the measuring errors in this case are parallel motion errors and rotatory motion errors of the head. Furthermore, accidental errors which are involved in the measuring values are reduced by least square method. In experimental analysis, a laser interferometer is used as the measuring head. And the influence of form errors of reference surface are removed by calculating data. In this paper the following results are revealed by some simulations and several experiments. (a) The repeatability of this experiment is about 40nm (2σ). (b) Measuring values of this method sufficiently coincide with those obtained by 2D least square serial 2point method.

Precise control of manipulators in contact with constrains in their environments is a prerequisite to feasible application of robot manipulators to complex handling and assembly problems in industry and space. An important step toward achieving such control is to control simultaneously position and force trajectory. Through recent advances in robotics technology many control design methodologies have been proposed for the control of robot manipulators. The hybrid technique is well known technique in these methodologies. In this technique coordinate system on the constrains plays an important role. But decision scheme of the coordinate system has not been proposed clearly.This paper analyzes the hybrid technique based on the constrained control system and proposes a new conceptually simple approach to the hybrid technique. The new approach is able to control simultaneously manipulator impedance and position trajectories on the constrains. The coordinate system is appropriately selected and divided into two coordinate systems. These two coordinate systems represent two independent input spaces where the hybrid technique is realized.Finally we also present the results of experiments that explore application of the hybrid technique to a control of a two degrees of freedom manipulator.

In parallel mechanisms with redundant actuators, actuator forces are underspecified because of redundancy. In this paper, the method to minimize a maximum actuator force was proposed. At first, parallel mechanism with two redundant actuators and Stewart platform model using the linear shaft motor were developed. This redundant parallel mechanism was consists of Stewart platform and additional 2 redundant actuators. Inverse dynamics of each mechanisms were formulated. Secondly, effectiveness of dynamic control of Stewart platform was experimentally confirmed. Finally, the method to minimize a maximum actuator force using Linear Matrix Inequality (LMI) was proposed. And the effectiveness of the proposed method was confirmed by simulation.

This paper presents a new controller design method based on the data-mining polynomial algorithm. We show application of a polynomial data-mining algorithm to controller design, where an input-state linearized polynomial vehicle model is developed for a very low speed operation and without introducing any process with fudge factor, control inputs of nonlinear system are obtained in the original coordinate. We verify the developed modeling method and controller design method through some numerical experiments.

A framework of adaptive controls to compensate for uncertain nonlinear parameters in robot manipulators is developed. The proposed adaptive controllers with a linear parameter-like structure guarantee global boundedness of the overall system and tracking of a given trajectory within any prescribed accuracy. Our design approach takes advantage of a Lipschitzian condition with respect to the nonlinear parameters of the plant dynamics. This allows our approach to solve a very broad class of nonlinearly parameterized adaptive control problems for robot manipulators. Another feature of the proposed method is the design of low-dimensional observers, even one-dimensional, whose dimension is independent of the dimension of unknown parameters. Comparative simulations and experiments confirm the advantages of the proposed adaptive controls for a friction compensation task in low-velocity tracking of a 2 DOF planar robot.

A decorrelator using the traditional linear equation solution has a computational complexity O(K/sup 3/) for a CDMA system with K active users. This paper introduces optimization-based decorrelating algorithms with a lower complexity O(K/sup 2/). Simulation results show that the proposed algorithms can achieve the performance of the traditional decorrelator in a synchronous CDMA system on an AWGN channel.

This study discusses the positioning and vibration control of time-varying vibration systems whose parameters are time-varying. We assume that the time-varying parameter of a vibration system is detected by an on-line measurement or Wavelet analysis. This paper treats two control methods based on nonstationary optimal regulators (NORs) for this problem. The first method is a gain-scheduling of NORs. An actual controller is obtained by the interpolation of plural NORs designed a priori. The other one is an NOR design based on Wavelet analysis of the vibration system. In the second case, single NOR derived from the analysis result is applied. This study shows the effectiveness of these methods by numerical calculations and experiments. From the comparison of these methods, this paper suggests suitable applications of NOR according to the characteristics of each control problem.Copyright © 2003 by ASME

In this paper, a simple control methodology for macro/micro manipulator system is proposed. The macro/micro manipulator system consists of a multi-link rigid body manipulator as a macro manipulator and a machining unit mounted on the end-effector of the macro manipulator as a micro manipulator. It is shown that the state equations of the proposed macro/micro manipulator system are identical with the singular perturbed system. A simple method of control system design of this system can be derived from the singular perturbation theory. Simulation results show that the proposed control scheme perfectly compensates the tracking errors. An experimental verification of the proposed control algorithm is shown by applications to electrodischarge machining. >

Since system uncertainties are unavoidable in the modeling, control systems are generally required to be insensitive to these uncertainties. In this paper, the problem of control system design which is insensitive to these uncertainties is studied, and a structure of system uncertainties which do not affect the control performance is clarified.

グラインディングロボットにおいて, マニピュレータに取りつけられたグラインダは, マニピュレータの剛性が低いために, 振動姓じやすく, そして時には, 不安定にさえなる.その振動は研削面を荒くしまた, 鞍定状態はマニピュレータを破損に至らしめることがある.本論文は, 研削時のグラインダの安定性について議論している.加工物の平面部が研削されるとき, 加工面の接線方向に対するグラインダの運動は線形微分方程式で記述される.この式から, グラインダの安定性は, マニピュレータの剛性マトリックス, 被削面の傾斜角, 加工物とグラインダの摩擦係数に依存することが示される.一方, 曲面上の研削の場合, 微分方程式は非線形になる.その場合, 研削の安定限界は, 被削面の曲率の影響を強く受ける.グラインディングロボットの曲面研削においては, グラインダを安定に支持するために, マニピュレータのリストが曲面に応じて制御されなければならないことが示されている.

This paper considers theoretically and experimentally the control problem of the biped locomotion system on the double support phase. The motion on the double support phase is described by the constrained dynamic system with two static constraints. The reduced order equations are derived by eliminating Lagrange's multiplier from the constrained equations, and a control algorithm for stabilizing the motion is obtained in reduced space. Finally, this algorithm is applied to an actual robot constructed in our laboratory and its usefulness is shown.

When an industrial robot grinds a curved surface of a workpiece, an operator must teach the robot the contour of the surface accurately. This instruction, however, is a very troublesome job because of the large number of teaching points. This paper proposes a grinding robot that requires no teaching. The robot system consists of a manipulator mounted on a cylindrical grinding wheel on the end effector, instruments to measure the three different forces and a computer equipped with an A/D converter. The force information consists of the grinding torque and the two components of the grinding force which is applied to the grinding wheel from the workpiece. The coordinates of the points where the wheel contacts the workpiece are calculated from the force information by the computer. Therefore, the robot is able to recognize the contour of the workpiece and to grind it without teaching. Experiments using an articulated robot arm with five degrees of freedom show that the proposed robot system is applicable to t...

産業用ロボットが加工物の曲面を研削するとき, オペレータは研削面の形状を正確に教示しなければならない.しかしながら, この教示工程は, 教示点数が極めて多いために大変やっかいな作業である.本論文は, そのめんどうを除くために, ティーチングレス形のグラインディングロボットを提案している.このロボットシステムは, 手先に円柱状の砥石を取り付けたマニピュレータと, 3種類の力を測定する装置と, AD変換器をもつ計算機から構成されている.力情報の1つは, 研削トルクであり, 他の2つは, 砥石が加工物から受ける研削抵抗力の2成分である.砥石が加工物に接触する点の座標は, この3つの力情報から計算機で求められる.それゆえに, ロボットは加工物の曲面形状を認識することが出来て, ティーチングなしで加工物を研削することが出来る.5自由度の多関節型ロボットを用いて実験した結果, 提案したロボットシステムは加工物の連続的な曲面を研削できることがわかった.

It is a very time-consuming task to teach a grinding robot the contour of a workpiece accurately. Therefore, we have proposed a self-teaching grinding robot. This robot system measures three moments which are produced by the grinding force at the wrist of a manipulator, calculates the grinding points on a cylindrical grinding wheel, and recognizes the contour of the workpiece. In order to develop this technique practically, we have studied the determination of grinding points on grinding wheels of various shapes. The results of the analysis and experiments indicate the following: (1) If the shape of the grinding wheel is known and is invariant without wearing away, the grinding points can be calculated from only three components of the moment produced by the grinding force. (2) The calculation is, however, very difficult when the radius of the grinding wheel is not a linear function of the distance along the rotational axis of the wheel. Therefore, one component of the thrust has to be detected to simplif...