Conventional trajectory planners most widely used is based on a trapezoidal pattern of a end-effector velocity on the desired path in a task space. This method can be implemented on real time. However, the motion planned by this method usually leads to a very slow motion, because it is difficult to take into consideration a constraints on the magnitude of joint velocities or joint torques. In this paper, we propose a new trajectory planner for 3 d. o. f. manipulators based on a kinetic energy of manipulators. The supplied electric power for the manipulators mainly depends on the differenciation of kinetic energy. Therefore, , the proposed method can take into consideration the constraints on the magnitude of a supplied electric power and joint velocities, in other words, we can realize a“high speed motion”under the constraints on the supplied electric power and the joint velocity. Also the proposed method dose not require so much calculation amount, and can be implemented on real time.
This paper describes a six-axis force sensor for robot manipulators, which consists of a cross-shaped plate spring formed from a 160 mm×160 mm beryllium-coper plate 1 mm thick. The plate spring is twisted through an angle of 90°at mid-point of each branch of the cross- shaped spring, so that it consists of eight flat springs aligned on two orthogonal axes. Six components of the force/torque vector acting on the end-effector are measured using strain gauges cemented on sixteen locations of the plate spring. Optimal locations of strain gauges are determined through the calculation of strairk distribution caused by each component of the force/torque vector. A simple setup for calibraition of the sensor, which consist of a pair of commercial linear guides, a pair of force indicating meters, and a pair of micrometer heads, is presented. Performance characteristics of the sensor are examined in detail.
When multiple mobile robots are working in the same environment, it is necessary to plan such motions for the robots that they never collide each other. This paper proposes a useful algorithm for planning a collision-free coordination for two mobile robots in an unknown environment on the basis of local information from their sensors. This algorithm conquers the problem of coordination planning by a two-levels strategy. In the case that no collision between two robots is detected, the robots are independently guided by the motion planning algorithm proposed by V. Lumelsky. However, in the case that a potential collision is expected, their motions are coordinated to avoid the collision. To coordinate the robots, a two-dimensional task space (T-space) and a point automaton are introduced. By controlling the motion of the automaton in the T-space, any collision between the robots can be successfully aboided. Convergence of the proposed algorithm is proved, and its usefulness is shown by a simulation.
This paper discusses a control for a non-linear distributed-parameter system of a flexible arm with a suspended load, taking mass and stiffness distributions of the arm into consideration. The fact that the rest system has null potential and kinetic energy is employed to derive an asymptotically stable control law which suppresses both the load-swing and the elastic vibration of the link and controls the angular position of the arm. The approach needs neither linealization of the system dynamics nor the modal decompositon of the dynamics. Therefore, the resultant control law does stabilize the non-linear dynamics of the system free from the traditional spillover problems. The validity of the proposed approach is demonstrated by several experiments, and then the effectiveness of the controller is shown.
In assembly process visual features of a target object often occluded by not only surrounding objects but also the object itself or the robot hand. In this paper we propose planning functions of visual measurement to solve this problem. The planning system selects features which are appropriate for the measurement purpose using the object model and the vision sensor model. Under planning the system uses active measurement strategies such as (1) if the target object's features are not available, the scope of candidate feature is expanded to featuses of the objects which rigidly connect to the original object or the robot hand, (2) if needed the system selects the best hand pose to measure the ripped object. These planning functions are implemented in a hand-eye system which uses light plane intersecting method. Measurement experiments showed effectiveness of the methods.
A new teleoperated grinding bobot has been developed which can safely and efficiently carry out grinding tasks in hostile environments using remote control and automatic control. This robot system incorporates a new method for the measurement of the grinding force, in which the grinding force is measured from a moment about the grinder head's center of gravity. The influence of inertial forces caused by translational motion is removed so that high stability is achieved. Furthermore, this robot can change the grinder's orientation to follow the surface of an object automatically, and can also grind the surface of an object into a desired shape. In this paper, We propose a new method for the measurement of the grinding force and also force control methods for unstructured grinding tasks.
The mobile robot wil meet various situations while it moves in the real environment. The occurrence of such situations are caused by the uncertainty of the real environment, and it's impossible to determine the exact timing of the occurrence before robot's moving. Therefore, the mobile robot must watch environment by its sensors and change its motion dynamically dealing with the occurred situations. In this paper, the concept of Action mode is introduced to analyze and represent such behavior of the mobile robot. Action mode is defined by motion commands to the actuator controller, the conditions to watch various situations and motion selection to deal with occurred situations. The robot behavior is represented by transition of Action modes. The robot control language ROBOL/0 based on the Action mode representation is proposed. The navigation of a mobile robot in the real world using the sensor and map information is treated as an example.
The self-reproduction capability of machines can enhance manufacturing efficiency and contribute to reliability since it enables the machines to fabricate themselves in geometric progression while testing their functionality through the reproduction process. In addition, a part of the process can be utilized as a self-repair process. This paper discusses the method of its realization on the basis of machines composed of identical autonomus cells. The proposed concept includes the specialization of cells according to their positions, growing in size by capturing new cells, transferring genetic data to the new cell, and splitting into two independent halves after grown up. Experiments have demonstrated the self-reproduction of mobile machines each of which is composed of multiple cells connected one another in a row, one-dimensionally.
This paper describes a method of planning grasps for parallel two-fingered grippers in order to pick up user-specified objects and place them at user-specified configurations. This system presents the following features : (1) By characterizing local space around gripping positions, it can plan grasps where the hand can move as freely as possible and then easily plan a path. (2) It can plan regrasping where the grasps themselves and the regrasping placements are computed flexibly according to the environment. (3) It can plan minimal sequences of regraspings for the objects that have rotational symmetries.
The design and motion experiments of the newly constructed crawler vehicle HELIOS-II with four track are discussed. The features of HELIOS-II are as follows; (i) The introduction of an equilibrium crawler which is supported at the central part of the tracks and is able to swing independently. (ii) The introduction of coupled drive system to increase the output power of installed actuator. (iii) The development of a new torque sensor consisting of a photosensor mounted onto a ring gear of a planetary gear reduction mechanism. (iv) The introduction of a new compliant nipple. (v) The introduction of impedance control scheme to maintain the horizontal posture of the carrier. The motion experiments of the HELIOS-II to crawl over an obstacle, climb and descend stairs, and rotate on the spot are shown and the validity of the introduced control is demonstrated.
This paper describes the development of second proto-type system of patient lifting arm (PLA) . This is battery-powered and has built-in type control system. The PLA, to realize the low power consumption, the shape of the insertion board and sequential motion of patient lifting is optimized, and the pnewmatic spring power assist system is used. Decentralized type control system layout is employed for realizing the built in control system. The compact controller (local controller) is set up on a part of the robot. The loop type serial communication line is developed for the data communication between the local controllers. The robot was tested in the medical facilities. We discuss the future of the patient care robot under the testing results.