The authors have been conducting research on an autonomous system for loading operation by wheel loader. Experimental results at a field test site using full-size model (length: 6.1m) will be described in this paper. Basic structure of system consists of three sub systems: measuring and modeling of environment, task planning and motion control. The experimental operation includes four cycles of scooping and loading to dump truck. The experimental results prove that the developed system performed the autonomous operation smoothly and completed the mission.

Nonstop update (NSU) is a service robot architecture to upgrade running robot controllers without suspending the services of robot systems. Its target application is mobile robots operating in remote or hazardous environments where suspension of ongoing missions is unacceptable or human intervention for changing or debugging programs is not easy. The present paper introduces NSU from a point of view of both safety and performance. The present paper defines the safety in NSU as a property that controller programs should not suspend or run away because of update-related sources. Safety issues such as deadlocks, module dependency, discontinuity of behavior between before and after update, and delays due to update overhead time are addressed. Safety and performance of NSU is examined and demonstrated by using three practical mobile systems: a mobile manipulator for a power assist system, a hexapod legged mobile robot, and a biped walking robot with wheeled legs.

In this paper, a novel mechanism of remote actuation was proposed and its mechanical problems were discussed. This mechanism consists of leverage and parallelogram mechanism and transmits 3 d.o.f translational and 3 d.o.f rotational motions from the input to output. Such a remote actuation is significantly useful for robotic assist around MRI where the strong and precise magnet is used for imaging, because mutual effect between MRI and robot are inverse proportional to the distance. In this paper, the basic ideas of mechanism were introduced firstly. The discussions of its stiffness and workspace conclude their trade-off. Our new idea of workspace control for mechanical safety is preliminary discussed.

Describes dual mode control of walk and manipulation of a prototype hexapod with integrated limb mechanism, named MELMANTIS-1. MELMANTIS-1 uses six-bar linkages with four degrees-of-freedom as an integrated limb mechanism with dual use for a leg and for an arm. Omni-directional drive control is introduced to the hexapod walk with alternative tripod gait. The transformation from hexapod walking style into the combination of dual arms and quadruped platform is introduced. A remote control to handle an object by dual arms is experimented with in a simple application of a trash pitcher.

A dexterous micro-manipulation system was developed for applications such as assembling micro-machines, manipulating cells, and micro-surgery. We proposed a concept of a two-fingered micro-hand, and designed and built a prototype. We succeeded in performing basic micro-manipulations, including the grasp, release, and rotation of a microscopic object. The micro-hand is controlled by a position controller only. The accuracy of the micro-manipulation depends on the skill of the operator. For automatic manipulation, it is necessary to measure the micro-forces between the finger and the object. A micro force sensor has developed for the force control in micro-manipulation. In this paper, we describe the micro force sensor and perform an automatic micro-manipulation and force control with the sensor. The basic experiment performed shows excellent micro-capability.

Describes the development of a leg-wheel hybrid mobile robot and its step-passing algorithm. The authors have been developing a mobile robot named "Walk'n Roll". It has a leg-wheel hybrid locomotion mechanism. The robot has four legs, and a wheel is attached at the end of each leg. Legged locomotion has high adaptability for rough terrain, and wheeled locomotion possesses speed and efficiency. One of the obstacles that a wheeled vehicle can not pass is a step. A control algorithm for the leg-wheel hybrid mobile robot to pass a step is considered. The developed algorithm is implemented on Walk'n Roll, and is evaluated experimentally.

Biped robots have better mobility than conventional wheeled robots, but they tend to tip over easily. To be able to walk stably in various environments, such as on rough terrain, up and down slopes, or in regions containing obstacles, it is necessary for the robot to adapt to the ground conditions with a foot motion, and maintain its stability with a torso motion. When the ground conditions and stability constraint are satisfied, it is desirable to select a walking pattern that requires small torque and velocity of the joint actuators. We first formulate the constraints of the foot motion parameters. By varying the values of the constraint parameters, we can produce different types of foot motion to adapt to ground conditions. We then propose a method for formulating the problem of the smooth hip motion with the largest stability margin using only two parameters, and derive the hip trajectory by iterative computation. Finally, the correlation between the actuator specifications and the walking patterns is described through simulation studies, and the effectiveness of the proposed methods is confirmed by simulation examples and experimental results.

Since a biped robot tends to tip over easily, stable and reliable biped walking is a very important achievement. In this paper, we propose a balance control method based on an off-line planned walking pattern with real-time modification. First, a method of generating a highly stable, smooth walking pattern is presented. Then, a method of real-time modification consisting of body posture control, actual zero moment point control and landing time control based sensor information is proposed. By combining the proposed off-line walking pattern with real-time modification, the biped robot can walk smoothly and adapt to unknown environments. The effectiveness of the proposed method is confirmed by dynamic simulator such as walking on unexpected irregular rough terrain, soft ground and in environments in the presence of disturbances.

A hybrid cylinder/cable drive parallel arm and its motion control are discussed. The basic idea of the hybrid parallel arm is to make the best use of the mixture of the high power cable drive and the cylinder actuation to obtain a heavy-duty manipulator in construction and ship building applications. A prototype arm has been designed and built based on the analysis and the comparative study of several types of hybrid drive mechanisms, the Stewart platform, and a wire drive mechanism. The tension of wire has to be maintained properly in the hybrid mechanism during its motion. The proposed hybrid arm is a kind of actuation-redundant mechanism and its internal force can be freely controlled. The proposed control algorithm is to give wires proper tension during its motion by exploiting the internal force, The required tension and cylinder force can be obtained by compensating each link position command based on its compliance. The repeatability tests show the effectiveness of the proposed algorithm in maintaining the overall stiffness of the arm.

We apply the matrix method to kinematic analysis of our translational 3-DOF micro parallel mechanism for an instance of general flexure mechanisms. The matrix method has been well developed in architecture to analyze a frame structure. We found that this method is well applicable to such a flexure mechanism with circular notched hinges as our micro parallel mechanism because it is approximate to the Rahmen structure. Our matrix method can calculate a compliance matrix with less nodes of matrix than conventional finite element method. First, the compliance matrices of a circular notched hinge and some other beams are defined and the coordinate transformations of compliance matrix are introduced. Next, an analysis of our micro parallel mechanism is demonstrated.

In order to develop a high performance working robot, we design and develop a new robot based on the concept of "limb mechanism " for integration of legged locomotion and arm manipulation. The robot developed has six limbs which can be used for both locomotion and manipulation. The six limbs are set on vertices of regular hexagonal body so that this robot can have omnidirectional manipulability and mobility. We evaluate the stroke and the stability margin in all walking directions on six-legged and four-legged locomotion. As a result, this robot has higher omnidirectional mobility than conventional mechanisms.

Biped robots have better mobility than conventional wheeled robots, but they tip over easily. In order to walk stably in various environments such as rough terrain, up and down slopes, or regions containing obstacles, it is desirable to adapt to such ground conditions with a suitable foot motion, and maintain the stability of the robot by a smooth hip motion. We propose a method to plan a walking pattern consisting of a foot trajectory and a hip trajectory. First, we formulate the constraints of a foot trajectory, and generate the foot trajectory by 3rd order spline interpolation. By setting the values of constraint parameters, it is easy to produce different types of foot motion. Then, we formulate a hip trajectory using a 3rd order periodic spline function, and derive the hip trajectory with high stability. Finally, the effectiveness of the proposed method is illustrated by simulation examples.

Describes the mechanism and control of a leg-wheel hybrid mobile robot. Legged locomotion has high adaptability for rough terrain, and wheeled locomotion possesses speed and efficiency. A locomotion mechanism that combines legs and wheels is proposed, and a prototype mobile robot that adopts the mechanism is introduced. The robot has four legs, and a wheel is attached at the end of each leg. The front leg has three joints and a passive wheel. The rear leg has one joint and an active wheel. In order to make the best of the mechanism, three locomotion modes, wheel mode, hybrid mode, and step mode, are developed. In the wheel mode, four wheels are used on flat terrain. On rough terrain, the hybrid mode is selected, and two legs and two active wheels are used for locomotion. To climb or descend a large step, the step mode is used.

Since most conventional robots cannot easily be adapted to environments designed for humans, a human-size biped robot is expected to be able to play an important role in assisting human activities. The selection of suitable joint actuators is an important point when developing a human-size biped robot. In order to select suitable actuators and effectively utilize the selected actuators, it is necessary to clarify the relationship between walking patterns and the specifications of each joint actuator, and this is the issue tackled in the paper. First, a method of generating a high stability, smooth walking pattern is presented, and it is shown how various walking patterns can be produced by setting a series of defined walking parameters. Then, the dynamics of the robot, including the reaction force between the feet and the ground, are formulated. Finally, by simulation studies, the correlation found between actuator specifications and walking patterns is described, and the effectiveness of the proposed method is suggested.

We propose a special structure for an active catheter: a spiral structure. It consists of a flexible belt on which actuators, sensors, and/or control units are built. The belt is spiraled or put spirally around flexible tube to work as a catheter. The actuators on one roll of the spiral move the next roll to realize the bending, twisting, and/or expanding motion of the catheter. With this method, minute and complicated actuators, sensors, and circuits can be precisely machined with very high density, fabricated and wired together in one continuous plane with silicon processes. The advantage of this method will be simple and high-density fabrication. In the paper, the overview and kinematic analysis of the spiral-structure active catheter are discussed and some types of active catheters are proposed.

A dexterous micro manipulation system was developed for applications such as assembling micro machines, manipulating cells, and micro surgery. We have proposed a concept of a two-fingered microhand, and designed and built a prototype. We succeeded in performing basic micro manipulations, including the grasp, release, and rotation of a microscopic object. The two-fingered micro hand prototype should be more miniaturized for higher accuracy and combination in small chamber of SEM. In this paper, we will propose a small-sized 3-DOF finger module with a parallel mechanism. An optimized link mechanism for miniaturization is used to the finger module. A photo fabrication system is used to fabrication of the finger module. Basic experiment shows excellent micro capability.

A new hybrid cylinder/wire drive parallel arm (simply called "a hybrid arm") for manipulating heavy materials in construction and ship building works is proposed. Various hybrid arms with different combination of cylinders and wires are compared with the conventional Stewart platform and a multiwire drive mechanism. Their workspaces considering orientation are evaluated. The most suitable hybrid arm for heavy material handling is the mechanism with three cylinders, four wires, and one connecting rod between the cylinders and the end plate. This hybrid arm is modified into a mechanism with a variable length rod for the application of manipulating a precasting concrete board with a size of 3/spl times/6/spl times/0.2 m/sup 3/ and a weight of 10 t which is used in automatic building construction systems; a prototype of this arm has been designed and developed.

This paper describes a walking control scheme for a quadruped robot. In conventional walking control scheme, the leg motion is generated from the robot moving trajectory beforehand and it is difficult to control in real time. The proposed control scheme employs a real time command from a human operator instead of the moving trajectory. The operator gives a current planar moving velocity command to the robot. Body propulsive action is basically continued according with the command unless a problem arises. When a foot reaches the border of the work space of the leg, the body propulsive actions is interrupted and a supporting foot pattern is changed. That is, a foot's arrival at the border is considered as an event to trigger a recovery action for the body propulsion. The recovery actions are decided to converge to the intermittent crawl gait when straight walking command is continued. The proposed control scheme is evaluated using actual walking robot.

High speed motion and positioning accuracy are the most important performance requirements of robot manipulators for the pick and place and assembly tasks. This paper focuses on the kinematic central system applied to a new parallel manipulator (NPM) with fixed linear direct drive actuators specially designed for high-speed trajectory applications. An optimal velocity based control method for high speed straight line trajectory of the NPM is proposed. The method is based on the maximum velocity zones analysis consisting of algebraic inequalities describing the constraints on the kinematics model. The proposed control algorithm is then implemented in off-line trajectory planning and in real time position servoing for kinematic control in the sense of achieving optimal trajectory performance. Digital PD control structure of the NPM is presented in order to satisfy the requirements in the actual manufacturing automation. The experimental straight line trajectory is satisfactorily controlled at a speed of 1.5 m/s with no reduction in accuracy.

This paper describes a control method of a manipulator mounted on a quadruped walking robot. One of the advantages of legged robots is the capability to change the body position and posture without changing the foot points. When a manipulator is mounted on a legged robot, it obtains extra motion from the body. By coordinating leg motion and manipulator motion, the end-effector has more sophisticated motion. When six degrees of freedom velocity command of the end-effector is supplied the proposed control method gives each joint velocity of the manipulator and the legs. This control method is experimentally evaluated using actual robot.

This paper describes the mechanical design and basic control of a prototype hexapod with "integrated limb mechanism", named MELMANTIS. MELMANTIS uses a six-bar linkage with four degrees of freedom as an example of integrated limb mechanism with both advantages for leg and for arm. The kinematic analysis is done for mechanical design. Basic control program of MELMANTIS is developed to experiment simple walking motion and transformation from a leg into an arm.

The concept of "limb mechanism" is proposed, consisting of several common link mechanisms which can be used for either arm or leg, selectively. Integrated kinematics is introduced for r legs and one arm mechanism. Based on the derived kinematics evaluation criteria are introduced in order to design the mechanism itself as well as a motion controller. Simulation results show how the proposed methods work effectively to analyze motion of the integrated mechanism.

This paper provides a new concept for the integration of locomotion and manipulation, "the integrated limb mechanism". The concept covers the technical fields both of the control integration and of the mechanism integration necessary for the practical working robot. Here, a six-bar linkage mechanism with four degrees-of-freedom is introduced as an example of the integrated limb mechanism with both advantages for leg sand for arms. Computer simulation with a dynamic model is performed to verify the transformability from leg posture into arm posture of this mechanism. The kinematic analysis is done for this mechanism, and it is suggested that the kinematic analysis is useful for the geometric and mechanical design. The possibility of dual arms or triple arm work is analyzed.

An excavation robot is required to build a large scale underground dome. The excavation robot is developed which is composed of a parallel manipulator and four legged locomotion machine. Although the parallel manipulator has a nice feature of producing large force required for the excavation, cooperative control should be considered to achieve effective excavation. This paper discusses integrated kinematics for r legs and parallel arm mechanism for analysis of the mechanism and its control. Based on the derived kinematics, evaluation criteria are introduced in order to design the mechanism itself as well as the motion controller. Numerical examples show how the proposed methods work effectively to analyze motion of the integrated mechanism.

This paper introduces a new concept for the integration of locomotion and manipulation. "the integrated limb mechanism" covers the technical fields of both the control integration and the mechanism integration necessary for the practical working robot. Here, a six-bar linkage mechanism with four degrees-of-freedom is introduced as an example of integrated limb mechanism. Kinematic analysis for the geometric and mechanical design suggests that the mechanism satisfies a contradictory conditions, not only for leg with slow heavy motion in downward posture, but also for arm with fast light motion in upward posture. The work space that two or three arms can reach is analyzed and evaluated by volume numerically for dual arm work and triple arm work. According to these analysis, a prototype hexapod with integrated limb mechanism, "MELMANTIS", was made.