Robot Base Research Articles

Base reaction control for space-based robots operating in microgravity environment

Specialized robots are needed for space stations to conduct experiments and operations without disturbing the microgravity environment through base reactions and/or base motions. Approaches for controlling the robot base include 1) manipulators with redundant degrees of freedom, 2) actuators at the robot base, and 3) a redundant (balancing) arm. An approach making use of manipulator kinematic redundance is explored in detail and both locally and globally optimal trajectory management schemes are discussed. The inverse kinematic problem is solved at discrete time steps simultaneously with the minimization of the robot's base reactions. Numerical examples are presented including various robotic configurations and degrees of manipulator kinematic redundance. A significant reduction in base reactions is observed in each case.

Effect of Image Processing on Recognition of Weld Line and Automatic Tracking by Welding Robot with a Visual Sensor.

In automatic welding of thin plates, it is well known that the application of an arc sensing system for the recognition of a weld line is relatively difficult. Therefore, an intelligent welding robot with a visual sensing system has been recently sought. However, it is not always easy to recognize the weld line clearly, because the weld line is sometimes very fine and the machined surfaces of steel plates have irregular brightness distribution. Therefore, a basic Cartesian-coordinate welding robot system with a visual sensor was constructed in order to investigate the recognition and automatic tracking of the weld line of machined steel plates. In this study, the effects of surface conditions of plates and the image processing of brightness distributions on the recognition of weld line were discussed, and moreover the effectiveness of the processes was experimentally confirmed.

Adaptive control of space-based robot manipulators

A control method is presented that achieves globally stable trajectory tracking in the presence of uncertainties in the inertial parameters of the system. The 15-degree-of-freedom (DOF) system dynamics are divided into two components: a 9-DOF invertible portion and 6-DOF noninvertible portion. A controller is then designed to achieve trajectory tracking of the invertible portion of the system, which consists of the manipulator joint positions and the orientation of the base. The motion of the noninvertible portion is bounded but otherwise unspecified. This portion of the system consists of the position of the robot's base and the position of the reaction wheels. A simulation is presented to demonstrate the effectiveness of the controller. A quadratic polynomial is used to generate the desired trajectory to illustrate the trajectory tracking capability of the controller.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Les apports respectifs des langages symboliques et de la cao en programmation des robots

SUMMARYA high-level robot programming language constitutes a general purpose interface for accessing the basic functional capabilities of a robot. On the other hand, CAD facilities give the possibility of using a subset of these capabilities in an easier fashion. In this paper, we show how a robot programming language and CAD facilities can be combined to obtain a robot programming system satisfying the need for generality, and allowing an easy connection with the basic robot programming functions. Such a connection is based on a “complete” simulator providing facilities for executing robot control programs on a graphic display, for describing manipulation tasks using interactive graphic tools, for simulating the physical world and its perception through sensors, and for displaying three-dimensional scenes as shaded pictures.

A New Silhouette-Related Algorithm for Improving Vision-Aided Robot Applications

A new algorithm for robot vision applications is presented which relies on an error analysis of chain code approximations. Silhouette information of objects presented is obtained from simple calculations with a high potential for hardware implementation. Experiments with simple geometric shapes are discussed. The experimental setup includes an industrial robot and a basic robot vision system developed by the authors, and demonstrates flexible component handling aided by vision sensing using the new algorithm.

パルスＭＩＧ溶接における溶融池の画像処理とデジタル制御

It is important as a basis of research in automatic arc welding to control the weld pool shape against the disturbance and the variation of system parameters. For this purpose it is useful to control the weld pool width. A basic visual robot is proposed for observing and controlling the weld pool shape by using the pulsed current.It has been difficult to observe the weld pool with a TV camera, since the arc light is too strong to watch the molten metal under the arc. The authors tried to make periodically the current low enough to watch clearly the weld pool with CCD (Charge coupled device) camera without after image.The weld pool is recognized by taking advantage of the feature on the brightness of the weld pool and its outskirts. A personal computer calculates the weld pool width and area in real time. The authors study the transient response of the weld pool width and area.The welding current is determined to get a desired response of the weld pool. It is shown how to determine the digital controller characteristic. Small variations of system parameter during operation caused by the change in the base metal thickness, heat conductivity, temperature rise are allowed while the prescribed control performance is maintained.Experiments demonstrate the good controllability of the adjustable weld pool formation with the digital controller.

ＩＴＶ画像処理システムによるパルス溶接のサンプル値制御

The problem for measuring and controlling the arc length and the torch height is important as a basis of research in automatic arc welding systems. Improvement of welding quality requires to keep constant optimum values of the length and current of the arc. In this paper, we discuss the stability and adaptability of the arc length in the MIG pulse arc welding system with a constant feeding speed of the electrode wire. Consequently, it is necessary to control the height of welding torch so as to keep the electrode extension constant for controlling both the current and length of the arc. We construct a basic visual robot which measures and controls the arc length and the torch height, using the personal computer, image processing device, and ITV camera as a sensor. Furthermore, we describe how to determine the characteristic of the digital controller, which controls the welding current and the digital servo motor for controlling the arc length and the torch height. We also introduce a basis of the electric techniques which incorporate the personal computer, image processing device, digital-analog converter, programmable current source, and digital servo motor.

Robot application simulation

This paper represents a continuation of the earlier work as reported in Refs. More realism has been achieved and an increasing number of basic robots and “building blocks” have been developed. The rapidity with which Robot/ Workplace situations can be analyzed and performances evaluated ensures that this method is a practical tool for assisting the exploitation and promotion of Industrial Robot Technology.