Piezoelectric actuator attached on flexure hinge is the common structure in micro manipulation system. However, it has been the fact that hysteresis is inherent in any piezoelectric actuators, especially when using voltage steering, which in turn, can degrade the performance of the system. Therefore, it should be treated carefully. In this work, a simple Dahl model is constructed to capture the hysteresis effect together with the mechanical model. For simplicity, the nature of the micro manipulator is assumed to be modelled as lumped parameters. From open-loop experimental response, a disturbance observer is constructed based on that model for estimating the hysteresis effect. Finally, some experiments are performed. Experimental result shows that the area of the hysteresis curve could be minimized significantly. However, it is still asymmetric due to the behaviour of the flexure hinge. Therefore, an integral action is added to reduce this effect. It is seen that the hysteresis could be compensated well

Our path planner is divided into two phases: First, let the robot study its maneuvering environment before giving a task, and then based on the studied map the robot is able to generate a safe and smooth path to its desired goal by using our potential field based collision avoidance algorithm. The environment exploration is done by adopting reduced generalized Voronoi graph which creates a topological map containing only GVG edges unrelated to boundary points. By setting sub-goals at meet points on the map the dead-lock problem caused by existing concave environment can be solved. The local minima problem encountered while the robot is traveling along subgoals is also solved by redefining the repulsive potential field. The system controller (look-ahead control) gives the robot a capability of controlling the distance between the reference point and the center of the robot. As a result, the potential field method performs effectively under our system and allows the mobile robot to follow a smooth trajectory in a flexible manner for attaining the desired goal autonomously whether in a static or dynamic environment

This paper investigates multiple wheeled mobile manipulators coordinating with each other for a common task such as transporting a common object. In our previous work we derived kinematic and dynamic manipulability measures for multiple mobile manipulators transporting a common object and also developed a simulation environment. The main objective of this paper is to conduct experiments with two different real robot systems, arm-type and table-type, and compare them with simulation results. Collision avoidance is also considered, in which they maneuver to avoid a collision while maintaining support for the object.

Recent surge of micro machine and nanotechnology has drawn a lot of attentions. Especially, finding of carbon nanotube has been spurring many new applications which were thought out of reach before its finding. A field dealing with how to handle parts and structures in microscale or nanoscale is called micro-manipulation or nano, respectively. A lot of research works have been done in this field and some of such research outcomes are already in market for commercial use. However, their applicability is still limited partly because of lack of flexibility in hardware as well as in software. Objective of this study is to provide hardware and software tools for such micro manipulation systems which are considered to be useful for more variety of applications. Those tools are chosen from the viewpoint of force feedback which can provide a user with a virtual feeling so that he/she can sense an actual manipulation task on his/her own hands or fingers. Providing these choices not only helps prevailing micro manipulation systems but also makes research coordination and production coordination much easier.

Investigates multiple wheeled mobile manipulators coordinating with each other under a collision avoidance situation. Yamamoto and Yun (1994, 1997, 1999) derived kinematic and dynamic manipulability measures for multiple mobile manipulators transporting a common object. The main objective of this paper is to extend the previous approach to a system consisting of two mobile manipulators carrying a common object while avoiding a collision. The two mobile manipulators dynamically change their configurations so that they do not collide with each other while not only maintaining the support for the object but also keeping the arm's configuration away from singularities.

This paper investigates the mechanism of a high-precision insertion process from the viewpoint of sensory information. Tolerance considered in the present study is approximately 5 /spl mu/m. Currently the assembly task is being conducted by skilled human workers. In order to analyze the insertion task, we focus on force and moment information and inclination measurements. A conventional approach, i.e. a position-based analysis, is not appropriate for such a narrow dimensional tolerance because it is unlikely that human operators conduct the task based on position information. This paper presents a newly developed, high-sensitivity moment sensor and experimental results in high-precision insertion tasks.

A lot of research on assembly automation problems has been made by many researchers from a variety of communities, e.g., manufacturing, artificial intelligence and so on. They mostly focused on the geometric constraints related to a considered task, e.g., relative configuration change between the peg and the hole. Such an approach, however, seems valid only when the dimensional tolerance is fairly large so that it allows the relative configuration of the two mating parts to be changed in an obvious fashion. The paper investigates how highly precise assembly tasks can be automated. Tolerance considered in the present study is in the range of 3 /spl mu/m /spl sim/ 9 /spl mu/m. Currently the assembly task is being operated by skilled human workers. In order to analyze the insertion task, we focus on force sensory information and attitude measurements involved in the high-precision peg-in-hole task of a polygon mirror unit because a position-based analysis under such a narrow dimensional tolerance seems inappropriate. A variety of insertion experiments are conducted by skilled and unskilled subjects for comparison purposes.

Giant magnetostriction materials feature include outstanding magnetostriction, high energy density, high Curie temperature and quick response. This paper presents two kinds of novel applications of giant magnetostriction materials: a compact fine positioner and a wire clamper. The former is able to achieve highly accurate positioning due to a novel structure design which substantially reduces the influence of Joule heat generated by the solenoid coil. The latter application is motivated by a great demand towards a wire clamping device for semiconductor manufacturing, which is capable of maintaining a sufficient clamping force without fatigue.

This paper presents an unified approach to the task space analysis of a wheeled mobile manipulator interacting with the environment. The system considered consists of two articulated manipulators atop a wheeled mobile platform handling a common object. We derive the task space ellipsoid, both kinematics and dynamics, for a wheeled mobile manipulator which takes into account manipulation and locomotion. The ellipsoid is able to visualize how the manipulator and the platform can contribute to a task execution by integrating the mobility of the platform with the manipulability of the arms as one unified measure. This measure can be useful not only for the task space analysis of a single mobile manipulator, but also for the coordination of multiple arms, mobile robots or mobile manipulators.

This paper deals with a coordinated task between a human and a mobile manipulator in which the human operator takes an initiative of the task execution. The task trajectory can be modified arbitrarily by the human, and the mobile manipulator will follow the trajectory while executing the task together, e.g., transporting a large object. This requires two issues to be resolved simultaneously, that is, the coordination of locomotion and manipulation and the task execution such as carrying an object. Force control scheme is integrated with the coordination algorithm of locomotion and manipulation. The force control part sustains the object while the coordination between the manipulator and the platform is maintained at position level such that the manipulator does not fully extend or retract. Computer simulations are provided to show the efficacy of the proposed approach.

A mobile manipulator composed of a manipulator and a mobile platform has a much larger workspace than a fixed-base manipulator due to the mobility provided by the platform. While the on-board manipulator reaches out and performs manipulation tasks, the role of the mobile platform is to position the manipulator in a preferred configuration. In this paper, we study the effect of the dynamic interaction between the manipulator and the mobile platform of a mobile manipulator on the task performance. We consider the task that the end point of the manipulator tracks a desired trajectory in a fixed reference frame. The effect of the dynamic interaction on the tracking performance is examined by comparing four different cases: 1) with full compensation of the dynamic interaction with each other; 2) with the mobile platform compensating the dynamic interaction caused by the manipulator; 3) with the manipulator compensating the dynamic interaction caused by the mobile platform; and 4) without any compensation of the dynamic interaction at all. Simulation results from representative trajectories are presented to illustrate the effect.

In the absence of obstacles, the study of mobile manipulators is mainly concerned with the coordination of locomotion and manipulation. In the presence of obstacles, one must simultaneously consider the obstacle avoidance problem and the coordination problem. This paper presents a control method for mobile manipulators that integrates an obstacle avoidance scheme with a coordination scheme. The obstacle avoidance scheme is based on superquadric potential functions. The coordination scheme is based on preferred operating regions. The controller allows a mobile manipulator to retain optimal or sub-optimal configurations while avoiding obstacles. Simulation results are presented to demonstrate the effectiveness of the control method.

Presents a collaborative effort to design and implement a cooperative material handling system by a small team of human and robotic agents in an unstructured indoor environment. The authors' approach makes fundamental use of the human agents' expertise for aspects of task planning, task monitoring, and error recovery. The authors' system is neither fully autonomous nor fully teleoperated. It is designed to make effective use of the human's abilities within the present state of the art of autonomous systems. The authors' robotic agents refer to systems which are each equipped with at least one sensing modality and which possess some capability for self-orientation and/or mobility. The authors' robotic agents are not required to be homogeneous with respect to either capabilities or function. The authors' research stresses both paradigms and testbed experimentation. Theory issues include the requisite coordination principles and techniques which are fundamental to a cooperative multiagent system's basic functioning. The authors have constructed an experimental distributed multiagent-architecture testbed facility. The required modular components of this testbed are currently operational and have been tested individually. The authors' current research focuses on the agents' integration in a scenario for cooperative material handling.

A mobile manipulator composed of a manipulator and a mobile platform has a much larger workspace than a fixed-base manipulator. While the on-board manipulator reaches out and performs manipulation tasks, the role of the mobile platform is to position the manipulator in a preferred configuration. In this paper, we study the effect of the dynamic interaction between the manipulator and the mobile platform of a mobile manipulator on the task performance. We consider the task that the end point of the manipulator tracks a desired trajectory in a fixed reference frame. The effect of the dynamic interaction on the tracking performance is examined by comparing four different cases: (1) without any compensation of the dynamic interaction at all; (2) with the mobile platform compensating the dynamic interaction caused by the manipulator; (3) with the manipulator compensating the dynamic interaction caused by the mobile platform; and (4) with full compensation of the dynamic interaction with each other.>

Since the dynamics of a wheeled mobile robot is nonlinear, the feedback linearization technique is commonly used to linearize the input-output map. The input-output linearized system has a nonlinear internal dynamics. In this paper, the internal dynamics of the mobile robot under the look-ahead control is first characterized. The look-ahead control takes the coordinates of a reference point in front of the mobile robot as the output equation. Using a novel Lyapunov function, the stability of the internal dynamics is then analyzed. In particular, it is shown that the internal motion of the mobile robot is asymptotically stable when the reference point is commanded to move forward, whereas the internal motion is unstable when the reference point moves backward. Simulation and experimental results are provided to verify the analysis.