This paper proposes an object dynamics virtualization that enables a human operator to handle the object easy for a given task by changing dynamics of the object by a robot assistance. The proposed method uses a force sensor fixed between an end effector of the manipulator and an object to measure force/torque applied by the manipulator to the object. Then, force/torque applied by an operator are estimated by using a disturbance observer, which subtracts the sensing force/torque from those calculated based on the object acceleration. Using the force sensor makes implementation easier by isolating the object dynamics from those of the manipulator. By using a virtual internal model driven by the estimated force/torque, a task-oriented mechanical impedance is given to the object that is in reality heavy and unbalanced as if it were lighter and well-balanced. Experiments to virtualize dynamics of a rod with a weight at one end, i.e., an example of an unbalanced object, to be a uniform disc by a SCARA manipulator with three degrees-of-freedom were conducted, and the results showed the validity of the proposed method.

In this paper, we propose a control method to swing up and stabilize a double Furuta pendulums (DFP).The DFP is a rotational type inverted pendulum system that has a base-link and two pendulums of different length at the both ends of the base-link. The proposed method consists of three controllers for the DFP, i.e., a swinging up controller for a long pendulum, a controller to keep a long pendulum at the upright position and to swing up a short pendulum simultaneously, and a stabilization controller for both pendulums at the upright position. Since the second controller has two objectives, we use safe manual control proposed by Astrom and Akesson. This paper proposes a novel application of the safe manual control. Swinging up and stabilization of the DFP was successfully achieved by appropriately switching three controllers. The effectiveness of the proposed method was verified by simulation and experiment.

This paper proposes a simple yet effective identification method for a first-order system including a time-delay. This method is based on the Laplace transformation in real number domain and is able to estimate both coefficients of the first-order system and the time-delay simultaneously. The accuracy of the identification results was analyzed using simulation. Precise estimation of the present method was confirmed compared to an orthodox on-line estimation technique utilizing a bilinear-model. Furthermore, a guideline for tuning the parameters used in the method is shown.

This paper is concerned with the development of the capsule robot (Capsubot) which can move with no external parts. It is easy to be constructed in small scale and maybe can be used for medical uses such as the endoscope since the Capsubot moves bidirectionally. The Capsubot could move by exerting friction force through movement of inside mass. This paper shows theoretical analysis and experimental verification of the locomotion for the Capsubot. In the experiment, the motion of inner mass is generated by coils and a magnet. Displacement of the Capsubot is measured by laser sensor and also position of the inside mass is measured. Using the developed test system, the motion of the developed Capsubot is experimentally compared with the one of the theoretical model.

Human Adaptive Mechatronics consists of Human and Mechatronics, and aims to develop Mechatronics systems adapting and assisting human operations. In this paper, dynamic characteristics of human operation is identified for designing an assisting control system. The dynamic characteristics gives the information for the limitation in the human operation and the basic information to design assisting control system for the operator to obtain a skill in a complex task.

It has been observed in our bimanual operation experiment with two XY-stages that the motion of one hand effects the another hand in high frequency and this coupling becomes weaker for skilled operators. This paper explains this phenomenon from the viewpoint of decoupling control.

This paper presents our recently research results on skill acquisition for machine operation. An assistance system with force feedback for skill acquisition is designed. An operation task is to balance an inverted pendulum. For that purpose, a virtual pendulum that is calculated real-time with computer graphics is developed. A human operator manipulates an X-Y stage as the human-machine interface with haptic function. An assistant controller is designed based on the Kawato-model. An experiment result shows effectiveness of this system for developing the skill.

Two XY-stages have been designed and are ready for human bimanual cooperative operation experiments for human adaptive mechatoronics. Each XY-stage is equipped with two DC motors, a six-dimension force sensor, and two encoders. A human operator can move the XY-stage through a grip mounted on the force sensor. The human dynamic characteristics are investigated at first, based on which the XY-stage specification is determined. A PID controller with the virtual internal model of the XY-stage is designed such that the XY-stages can follow the trajectory given by the human operator's operation, including the position and force commands. The response of the XY-stage control systems is measured without the human's operation to adjust the parameters of the PID controller. Then the human operator's responses to sinusoidal signal of different frequency are measured to obtain the Bode diagram of human response. The characteristics of human operators with single hand and bimanual operations are investigated using the XY-stages experimentally.

Deals with the coordinated controller design for a certain kind of cooperative manipulation of an unstable object with multiple robotic manipulators. Based on the system description in the framework of differential-algebraic equations (DAEs), control problems of the object manipulation with single and two manipulators are formulated. By characterizing a hand-over operation as a result of the simultaneous solution to the both problems, a reliable-controller design technique is applied to derive the controllers. Thus formulating the hand-over control problem as a reliable control problem derives a class of the object which can be handed over at least by using the proposed control scheme and a constructive design method of the controllers. The experimental results are included.

The study of bipedal walking in the framework of humanoid robot is a recent active research area. In this paper, we apply passive velocity field control to the control of a biped walking robot which walks on the level ground by actuators. Using this method, we can change the walking speed easily by modifying a virtual energy. The validity of the proposed method is demonstrated by numerical simulations.

It has been shown that a simplest walker with suitable parameter choice can walk down a gentle slope without any control forces and generate its steady walking pattern utilizing gravity effect automatically. On the floor, however, the robot cannot exhibit passive walk, so any application methods of passive walk to active walker on the horizontal floor has not been studied yet. In this paper we introduce "virtual passive dynamic walking" with virtual gravity field which acts as a driving force for the biped robot. The robot can walk on the floor without any control torque except virtual gravity effect. Since the modified gravity field seems to be very close to real condition, the generated walking pattern seems to be natural. Further, multi-pattern walking with respect to energy level is proposed. With the proposed method, safety and energy-effective control of biped walking robot can be realized.

A new controller-design framework for cooperating manipulators is considered in this paper based on a reliable controller design concept. The objective of this paper is to derive a set of controllers for cooperating manipulation especially which can hand over an object. The key idea is to reformulate the original problem of coordinated control as reliable stabilization problem; i.e., to design a set of controllers which can stabilize a plant both jointly and alone. By introducing a kind of strict force control scheme in the workspace, the reliably stabilizing controller design technique is applied to derive the controllers. Two contributions are existing: (i) clarifying a class of the object which can be handed over at least by using the proposed control scheme and (ii) presenting a constructive design method of the controllers. Experimental results on the hand-over control of a 2D inverted pendulum with two 6-DOF manipulators are included.

In this paper we discuss pattern generations and switching for robot manipulators to perform tasks under qualitative changes of the dynamic environment. The approach is to compose continuous type artificial neural elements as an oscillator based on mutual entrainment and generate trajectories for the manipulators. Using the neural oscillator, juggling control of manipulators is considered as a concrete task, and a method to alternate patterns of the trajectories according to the change of the desired value and environment is proposed. Some numerical examples show the efficiency of the proposed method.>

In this paper we propose a technique for tele-virtual reality of dynamic mechanical models, which means that one dynamic mechanical model can be shared by peoples in distant places. Since a stabil- ity issue due to time delays arises in the system, we employed a scattering technique developed for a tele- operator system and a kind of passive adaptive con- trollers. Furthermore, restrictions due to a simple digi- tal implementation of the scattering transformation are discussed and some conditions for stability are shown. The proposed method is applied to a remote tug of war system and the effectiveness is verified.

An alternative coordinated motion control architecture for robot arms manipulating an object is proposed. The motion and the internal force of the object are resolved in the motion of each arm. Each arm's control is based on the virtual internal model so as to operate in coordination even if geometric errors exist in the robot arms and the object. The virtual internal model is a reference model driven by sensory information implemented in the controller. The proposed architecture keeps the state of the system bounded even if breakage of the manipulated object occurs. The control algorithm is experimentally applied to the coordinated motion control of two planar robot arms, each of which has three degrees of freedom. The results illustrate the validity of the proposed control architecture.>

The authors propose a parallel Newton-Euler algorithm for calculating the inverse dynamics of manipulators whose computational time is independent of the number of links. The algorithm consists of two paths: a forward path for calculating a kinematic chain, i.e., linear velocities, linear accelerations, etc.; and a backward path for determining a dynamic chain, i.e., forces and moments. In order to determine each moment or force perfectly, the paths must be tracked sequentially. Complete parallel implementation of the Newton-Euler algorithm with data buffering is proposed for constructing a control scheme whose control period can be reduced drastically and is independent of the number of links. Delays due to the data buffering are suppressed by a one-step-ahead prediction using a linear model. The effectiveness of the proposed algorithm is demonstrated by extensive numerical simulations.>

Intelligent control of an assembly robot using vision is presented. In assembling, the task is planned by the task planner, and the corresponding robot trajectory is planned as the reference trajectory. The robot should also adapt to environmental variation. To coordinate the planner and robot, a virtual internal model is used to modify the planned reference trajectory according to the environmental variation. The use of a force and vision sensor is proposed in the virtual internal model for error correction in assembly. A simple assembling task is experimentally achieved to verify the validity of the proposed method. The task considered is screwing a bolt with an open-ended wrench fixed to the wrist of the robot, where the bolt is not accurately placed at the fixed predetermined place. The experiment shows that the proposed control system works satisfactorily.>

A single-master, multiple-slave manipulator system and its task-oriented control using VIM (virtual internal model) are proposed. By using this system, the operator no longer has to consider how to control the slave arms in coordination, so the operator can concentrate on his/her task during the operation. An experimental single-master, multislave manipulator system with two slave arms, each of which has six degrees of freedom, is described, and the concept of the system is illustrated. The experimental system does not have a bilateral function, and a master arm can specify the task-oriented variable up to six degrees of freedom. The use of bilateral feedback as well as task-oriented functions will enable the system to deal with more complex tasks.>

A motion control algorithm is presented for a robot arm having joint torque sensors that calculates part of the control input using the measurement of the torques at the joints. First, a dynamic model of each joint with a torque sensor is derived, which gives the inverse dynamics of the arm as recursive Newton-Euler equations consisting only of forward path computation. Then, using this model, a control law is designed by means of the computed torque method. The resultant control law is robust against parameter variations caused by loading and unloading operations and uncertainties in mass properties of links because the measured torques include information on them. The control law is experimentally applied to a second joint of a direct-drive arm with two degrees of freedom, and the experimental results illustrate the effectiveness of the proposed control algorithm.>

The authors propose an alternative coordinated motion control architecture for robot arms manipulating an object. The motion and the internal force of the object are resolved into the motion of each arm. Each arm is controlled, on the basis of the virtual internal model, so that they operate in coordination even if geometric errors exist in the arms and the object. The virtual internal model is a reference model driven by sensory information implemented in the controller. The proposed architecture maintains the stability of the system even if breakage of the manipulated object occurs. The control algorithm was experimentally applied to the coordinated motion control of two planar robot arms, each of which has three degrees of freedom. The results illustrate the validity of the proposed control architecture.>

An alternative method is proposed for designing a robot-controller in Cartesian coordinates using a time-scale transformation. The proposed controller achieves slow poles in the area of poor manipulative ability and fast poles in the area of good manipulative ability. Therefore, the robot can be properly controlled in the neighbourhood of singular points without reducing the performance outside the neighborhood of these points.>

This paper presents a new control method of master-slave manipulators based on the concept of Virtual Internal Model Following Control, which realizes the master-slave manipulator system with various functions which assist operators as well as bilateral feedback based on external information from sensors or others. In the proposed control system, the virtual internal model is introduced to describe a desired relation between the motion of a master and that of a slave. The external information detected by sensors or others are applied to this model, and the motions of master and slave arms are controlled based on the model. The proposed algorithm is experimentaly applied to the master-slave manipulator with force sensors, and desired response to the external information as well as bilateral feedback is realized.

An alternative architecture of a robotic servo system with external information is developed. We name it Virtual Internal Model Following Control. First, a continuous path tracking problem of a robot arm in a working coordinate system is discussed and the control problem with external information is formulated. Then the virtual internal model is defined based on the formulation. This model is used to describe a control strategy for external information. The total servo system is synthesized based on the model following servo control concept. This architecture enables a robot to utilize general external information which includes information through sensors. As an example of the proposed control architecture, mechanical impedance control problem is discussed.

In this paper, we propose an alternative method for designing a robot controller in Cartasian coordinates using a time scale transformation. We will show how a suitable choice of the time scale allows us to control the robot in the neighborhood of singular points without reducing the performance outside the neighborhoods of these points. The resultant controlled system has slow poles in the area of poor manipulative ability and fast poles in that of good manipulative ability.

We present a new algorithm that generates a suitable input for a manipulator to track the desired predetermined trajectory after repeating trials. It is ensured that the error between the desired trajectory and that of the manipulator becomes zero in a certain sense as the number of trials approaches infinite. In the proposed algorithm a kind of dual systems is used for recurrsively making new input and that system can be simply designed. The proposed algorithm is based on functional analysis.

Kinematic and dynamic analysis of robot arm is discussed from the control point of view. For the static control problem, such as the steady-state force/torque control, the kinematic property is analyzed using the condition number of the Jacobian matrix of the transformation between the joint coordinate and the task coordinate. For the general control problem, such as position and orientation control of the end effector, the kinematic and dynamic property is analyzed using the condition number of the matrix which is representative for the input-output relation of a robot arm and related to the output controllability of the robot system. A simple illustrative example shows that the analysis is also useful for the design problem of robot arms.