An essential task for a mobile robot is path planning. This paper introduces a new dynamical representation of 2-dimension environment for a mobile robot. The representation can be easily updated when environment is not completely known or is dynamically changing, and the task of path planning can be done easily with the representation.
We consider control issues of robotic systems composed of several subsystems which are connected one another through some communication channels. Such complex systems involve random delays due to communications in addition to casual ones, for example, in measuring and signal processing. Thus we have randomly sampled robotic systems. In this paper, it is assumed that computed torque controllers are used for randomly sampled robotic systems and the asymptotic stability with probability one is studied. First, an approximate equation of error vectors from desired trajectories are derived. Using the equation, it is shown that randomly sampled robotic systems is always stabilizable by computed torque PD controllers and PID controllers if the distribution of sampling intervals are bounded. It is also shown that conventional critical damping controllers are robust for uniform distributions in terms of the stability, but they are not so for wide distributions in the communication. Hence a design method is proposed to select feedback gains in order to make the system asymptotically stable with probability one under given distribution of sampling intervals. Experimental results are also shown.
This paper describes a novel bilateral master control device for advanced teleoperation and discusses man-machine interaction method using the instruction device. The intervention tool is a 1-DOF bilateral master-slave dial designed to support remote execution of tasks in advanced teleoperation systems. Two kinds of intervention methods are proposed and have been implemented: predictive assistance and interruptive assistance. A teleoperation system integrating the intervention tool and the direct-drive manipulator ETA-3 has been developed. The system provides the operator the ability of real-time remote assistance of manipulator movement for error avoidance and recovery. A diaphragm exchanging task has been completed successfully using the assistance technique. The system configuration and experimental results are also described.
This paper treats a practical method to generate assembly strategies applicable to part-mating tasks that are of particular interest. The difficulties in devising reliable assembly strategies results from various forms of uncertainty such as an imperfect knowledge of the parts being assembled and limitations of the devices performing the assembly. Our approach to cope with this problem is to have the robot learn the appropriate control response to measured force vectors, that is, the mapping relation between sensing data and corrective motion of robot, during task execution. In this paper, the mapping is acquired by using a learning algorithm and represented with a binary tree type database. Remarkable features of the proposed method are the use of a priori knowledge and accomplishment of the task with little human trouble. Experiments are carried out by taking acount of practical production facilities. It is shown by experimental results that an ideal mapping is acquired effectively by using the proposed method and the assembly task is carried out smoothly.
In cooperative motion of multi-arm robotic mechanisms or in the case of the grasping by robot hands, internal forces which balance inside the mechanisms are generated. The internal forces have some effect on the characteristics of the mechanisms, while they produce no resultant forces which affect the environment. This paper deals with the effect of such forces on structural stiffness of the mechanisms. Firstly it is made clear that the change of the stiffness is caused by the change of lines of the internal forces due to the deformation of the mechanisms. As an example, the structual stiffness of the spring supported system was analyzed. It was pointed out that, when the internal force is in compressive form the mechanisms may have negative stiffness leading to the unstability in grasping operation. It was also cleared for four-bar mechanisms that the stiffness of the mechanisms change due to the internal forces, though the internal force problems have never discussed for such fundamental mechanisms. It was shown that the effect of the internal forces changes according to the configuration of the mechanism and it is preferable to grasp objects with the configuration of the fingers closed to the rectangular form.