The automatic generation of assembly or disassembly sequences is needed to realize assembly or disassembly tasks with a robot. This problem can be deviled into the following three stages. They are, 1. modelling or representation of the assembly or disassembly network, 2. searching method, 3. decision of the criterion function. In earlier researches, what seems to be lacking in the problem 1 or 2 is a consideration of the task environment. Also, as for the problem 3, little attention has been given to it. In this paper, we propose a new assembly or disassembly sequence planning method. Firstly, we introduce a new assembly network representation with Petri Net graph which includes the environment in the conventional AND/OR graph. Secondly, we propose three criterion functions reflecting stability, manipulability and energy. These criterions fit well with experiences of a human operator. Also, we use the multi-objective Linear Programing to search the best sequence. Finally, we show examples to verify the validity of the proposed planning method.
Several papers focused on mobile manipulators have been already presented, but those researches assume that the robots move on a horizontal floor, and the papers do not argue disturbances which gravity gives to each joint axis including driving axis of the mobile manipulator. The influences of gravity generate directly undesirable torques around each joint axis of the mobile manipulator, and indirectly rolling resistances which are determined by the inclined angle of the slope and the figure of the mobile manipulator on the slope. For correct guidance of the mobile robot and controlling the mounted manipulator in such situation, those gravity influences would be better to be removed. This paper analyzes the dynamics of the mobile manipulator on a slope, and presents a compensation method to remove the gravity disturbances of the mobile manipulator.
Tele-existence is an advanced type of teleoperation system that enables a human operator to perform remote manipulation tasks dexterously with the feeling that he or she exists in the remote anthropomorphic robot in the remote environment. In order to extend the function of a human, an extended tele-existence system with virtual reality technology was proposed. For example, when visual information cannot be used because of smoke due to fire, then a human operator still can see the virtual environment of the scene and can control the robot. The model of the environment can be constructed from the design data of the environment. Usually, there are errors in the model of the environment. Large errors in parameters may fail operations using the virtual environment. In order to compensate for the errors, the calibration technique using model based image measurement is proposed for matching the real image and the virtual image. After the calibration, an experimental operation in the almost invisible environment was successfully conducted.
It is a major area in computer vision to recognize 3 D objects from 2 D images. One of difficulties of object recognition is caused by that 3 D objects are observed in various shapes in 2 D images. The aspect graph approach is one of available methods to solve the problem. This paper describes a new algorithm for creating aspect graphs for general polyhedral objects. In the proposed algorithm, we use a closed space centered at the origin of an object as a viewing space. We divide the viewing space into sets of viewpoints according to differences of aspects. An aspect graph is constructed by performing set operations on the sets of viewpoints. The set operations are executed by substituting solid polyhedra for the sets of viewpoints. This algorithm enables us (1) to classify aspects of a general polyhedral object under perspective projection, (2) to solve the problem of occlusion caused when an object has nonconvex parts, (3) to construct aspect graphs automatically.
This paper proposes a system to control mobile robots by applying traffic rules. The authors have constructed traffic rules to achieve safe and smooth movement of robots by collectively considering information on the work environments of mobile objects such as mobile robots and people. These traffic rules enable mobile robots to judge and control their own movements. Common rules are required to keep order in a society or group. These rules make it possible to maintain order in individuals having self-controlled will. Therefore, we propose the application of common rules for movements (traffic rules) to realize cooperative behavior of multiple mobile robots. We then consider the effects of applying traffic rules, especially the decrease in probability of collision, communication and detection range of the sensors. This paper first outlines a system of applying traffic rules for mobile robots, and explains how to construct and design the system by giving examples. The effects of the system, and how to apply the traffic rules to actual systems are then discussed. Finally, the paper examines the effectiveness of the system and describes experiments on mobile robots mounted with ultrasonic sensors.
In this paper, a dynamic trajectory tracking controller for a macro-micro manipulator system is proposed, in which the dynamics of the system is considered. The macro-micro manipulator system is a system consisting of a wide-range, low-response manipulator as a macro part, and a narrow-range, high-response micro part at the tip of the macro part. When the proposed scheme is applied to the system, the macro part is controlled by PD feedback controller for each joint, while the micro part is controlled to track the desired trajectory considering the dynamics of the whole system. An experimental result demonstrates the effectiveness of the proposed control scheme.
From the viewpoint of freedom from contamination, wafer handling systems with contactless mechanisms are required in the production of VLSI. Authors have developed a clean and vacuum-compatible wafer handling robot using an electro-magnetic suspension system. This two d. o. f. (degree of freedom) wafer handring robot can be applied to a wafer-hoist, a turn-table and a swing-arm in an ultra-high vacuum. The robot controller is fully digitalized by multi-DSP system. And the following advanced control methods are implemennted: 1) Electro-magnetic suspension control by decoupling control scheme. 2) Precise positioning by sliding mode control. The decoupling control enables to hold the position of the rotational axis precisely, regardless influence of the arm position. The sliding mode control using the coarse signal (72 pulse/rev. ) of position sensor significantly improves the overshoot at the rotational positioning. These control schemes are introduced and experimental results are shown in this paper.
This paper describes a revised optical displacement measurement method to develop tactile sensors based on a suspension shell mechanism for dextrous fingers, so that the sensor can detect arbitrary force in direction, in addition to the position and pressure of an external force. To express variables of the position and orientation of the suspension-shell, five parameters regarding circumferential, directional, and inclinational displacements, and also axial and radial displacements are defined. Then a method of measuring these five parameters using inverse of optical projection is proposed. Point source of lights are attached on a medium section of the suspension shell and lighten a pinhole to produce light spots on a 2-D photosensor through a pinhole. Vector analysis for reverting the values of parameters are shown. Also, characteristics of measurement sensitivity depending on a position of the medium section in the dynamic range of the shell is evaluated. The method is characterized by the fact that only an optical set embedded in a cylindrical body is enough to measure the displacement paramerters and to make fingers smart.
This paper describes a composition of an articulated multi-vehicle robot in pipe, structure of each vehicle, and their control systems. Output pressure versus extension characteristic of the newly developed two-stage air cylinder, reduction of the wave reflection in a wheel-type ultrasonic probe, umbilical cable assembly housing optical fibers, air tubes and electric cables are treated. The articulated robot is designed and fabricated to demonstrate its travelling performance and automatic scanning of five probes for non-destructive test of a weld bead to the longitudinal direction. The results show that the robot can travel in the pipe of radius 520-800 [mm∅] from its entrance to the distance 150 [m] . The robot can pick up surrounding color images and transmit them to the ground station's monitor with sharpness. Also, the NDT is shown to be possible except in the vicinity of elbow area of the pipe.
This paper is concerned with a direct teaching/playback method for a hybrid position and force control in a robot manipulation. By adjusting the impedance of the robot appropriately, a teaching operator can manipulate the robot tip easily in free space and constrained space by appling force to a teaching lever mounted at the tip of the robot. The operational force applied by the operator and the contact force acting on the smoothly curved constrained surface are stored in the computer as the teaching data. A given task in the playback process is to make a smooth contact with a constrained surface from the free space and to apply a specified forces while the tip of the robot is moving along the constrained surface. In the playback, the contact force is possible to follow the stored values of the contact force or the different values programmed after the teaching. To keep accuracies of the force control even when the location of the constrained surface is slightly changed from the teaching process, the well-known “hybrid control technique” is applied to obtain control laws. The method is applied to a 2-link vertical articulated direct-drive hydraulic robot. The experimental results affirm the validity of the proposed method.