Showing papers on "Robot control published in 1981"

Joint torque control by a direct feedback for industrial robots

Abstract: Based on the experimental findings of Wu and Paul [17], two joints of an industrial robot have been redesigned and fabricated to include torque sensing capability by means of strain gauges. The resulting control systems reduced the effective frictional torques of the joints from 1072 oz.in to 33.5 oz.in. The stability of the closed-loop systems was analyzed by means of the describing function for limit cycles exhibited in the system, which can be removed by an insertion of phased-lead series compensating networks.

A Structured Approach to Robot Programming and Teaching

Abstract: A structured programming and teaching system is described for a robot manipulator where stress is laid on the consistent integration of programming and teaching. In the PAL programming system being developed at Purdue University, tasks are represented in terms of structured Cartesian coordinates. Every motion statement is a request to position and orient the manipulator such that a position equation, representing a closed kinematic chain of homogeneous transformations, is satisfied. In the teaching process, the transformation which represents the position of the end of the manipulator is defined using the manipulator itself, and an equation relating any undefined transformations is obtained. By defining these equations during the interpretation of the task program and progressively solving them, the task is taught. The method is applicable both to practical industrial robot control and to intelligent robot control.

Apparatus for automatically adjusting the programmed location of a robot arm

Abstract: Apparatus for adjusting the position of a robot arm in response to coordinate data supplied by an external user process control. During the execution of a programmed cycle of operation, a robot control causes the robot arm to move to a predetermined programmed position. In response to a programmed adjust function code, the robot control requests change-of-position information from the user process control. Depending on the actual position of the robot arm, the user process control may transmit a set of adjusted coordinate data to the robot control defining an adjusted position. The robot control moves the robot arm to the adjusted position and proceeds with the programmed cycle of operation.

An Orienting Robot for Feeding Workpieces Stored in Bins

Abstract: A robot system has been tested which can acquire a class of workpieces that are unoriented in bins and transport them, one at a time, to a destination with the proper orientation. This kind of robot has numerous applications in industries which manufacture discrete-part products in batches. A variety of approaches to the design of an orienting robot have been identified. For acquisition, gripper design and vision algorithms should be considered together. A vacuum gripper which adapts to surface angle and an algorithm which finds the center of smooth regions in the bin image have been shown to form an effective combination. Knowledge of the position and orientation of the workpieces near the top of the bin is not necessary for acquisition. Collisions with workpieces in the bin whose poses are not known can be avoided by having the gripper follow a line of sight approach path. To simplify the computation of workpiece orientation, it was found to be useful to employ a gripper which locked a workpiece in one of a finite number of states and which did not obscure the workpiece. For an orienting robot which is designed to service a variety of different workpieces, using an arm with six degrees of freedom greatly facilitates workpiece transportation.

Simplified robot arm dynamics for control

Abstract: A brief summary and evaluation is presented on the use of symbolic state equation techniques in order to rapresent robot arm dynamics with sufficient accuracy for controlling arm motion. The use of homogeneous transformations and the Lagrangian formulation of mechanics offers a convenient frame for the derivation, analysis and simplification of complex robot dynamics equations. It is pointed out that simplified state equations can represent robot arm dynamics with good accuracy.

Method and apparatus for robot control

Abstract: A robot control method and apparatus of the type in which robot operations are taught in advance and the robot is subsequently actuated in accordance with the robot instruction data so taught. Areas in which the robot is forbidden to enter are established and the resulting information is stored in a memory. During the teaching of the robot operations the robot instruction data is created by moving the robot without regard to the forbidden areas. Thereafter, the robot instruction data so created is modified using the forbidden area information, the robot being controlled on the basis of the data so modified.

Self-teaching robot feedback system

Abstract: A self-teaching RCC device robot feedback system including: a robot mechanism; an RCC device carried by the robot mechanism; a robot driver unit for directing motion of the RCC device in an environment; means for determining the displacement of an RCC device with respect to the robot; and an adaptive learning system, responsive to the means for determining displacement, for detecting a pattern of displacements of the RCC device relative to its environment and generating commands to the robot driver unit to direct motion of the RCC device

Tactile sensation for robots

Abstract: In this paper we provide a brief discussion of the relationship of tactile sensation to other sensory modalities currently showing prominence in industrial robots. A tactile sensor is presented which provides a matrix of the forces existing between it and the object with which it is in contact. The possible uses of this information in the control of the manipulation of objects by a robot arm/hand system are considered. Examples of the data retrieved from the sensor are given and possible initial processing steps are discussed.

Apparatus for automatically moving a robot arm along a nonprogrammed path

Abstract: Apparatus for moving a robot arm through a series of nonprogrammed points defining a nonprogrammed path in response to coordinate data supplied by an external device. During the automatic execution of a programmed cycle of operation, a robot control causes the robot arm to move to a predetermined programmed position; and in response to a programmed external path control code, an external path control generator serially provides position data defining the nonprogrammed points. The robot control moves the robot arm through the nonprogrammed points, after which the programmed cycle of operation is continued.

Method of sensing abnormal condition in robot control apparatus

Abstract: Disclosed is a method of sensing an overload abnormality in a robot control apparatus for controlling a robot on the basis of instructive data. A motor for driving the robot has the upper and lower limits of its drive current or of its driving power set in advance. Then, when the robot is operating in the playback mode, the value of the drive current or power is monitored, and an operation is performed to check whether the value of the motor drive current or power is within the range of the set limit values, enabling an overload abnormality to be sensed. In accordance with the inventive method an instruction for checking the motor drive current or power is inserted beforehand at a proper location in the instructive data. When said instruction is read, a discrimination operation is performed to determine whether the drive current or power is within the range of the limit values.

A locomotion control system for mobile robots

Abstract: This paper discusses how to control and describe the smooth movement of a mobile robot which has two independent driving wheels (iDWs) that perform both steering and moving functions. Robots which have an IDW leg system can move to any point by using any combinations of two basic operations: revolving and going straight. It is easy to describe movement with two basic operations only, but this may not be sufficient to guarantee smooth motion. For instance, when the robot is moving, a slight modification to its track direction is impossible without stopping it. Smooth motions are also needed for minimizing the time required to complete the movement. Theoretically, an IDW leg system can draw a circular track with radius 0 - ≪ if one controls the ratio of the two wheel speeds. This principle underlies much of the design of this control system. The control system described in this paper uses three basic motion commands, supplemented by other commands that support these. A language has been designed for describing leg control algorithms. Examples of the usage of these commands and the language are shown here.

A Computer-Aided Robotic Arm/Worktable System for the High-Level Quadriplegic

Abstract: Opening the door to self-reliance for quadriplegics, this system provides manipulative capability for doing several tasks without assistance—including typing and using a computer.

The multi‐sensors which help a mobile robot find its place

Abstract: A comprehensive multi‐sensor system using three‐dimensional vision, a laser range‐finder, an ultrasonic proximity sensor, and an infra‐red radar for position location, have been built into a mobile robot.

Robots and manipulators

Abstract: Robots are defined and described for various applications. The key feature of robots is programmability, which allows teleoperation, repair work in hazardous situations, and unsupervised operation in industrial functions. Two types of robots now exist: special purpose, with equipment for a specific task; and general purpose, which include nonservo-controlled robots, servo-controlled robots, and sensory control robots. Sensory robots are the most sophisticated, and are equipped with both internal control sensors and external sensors such as TV cameras, pressure detectors, laser range finders, etc. Sensory feedback to a central computer enables the robots to make appropriate modifications to the control program to adapt to new situations. Pattern recognition and scans for size are features of the TV sensors, and programs to develop a universal effector (hand) are outlined. Finally, robot programming in terms of manual, walkthrough, and textual methods are described, and the potential uses of robots for space and undersea construction and repair are discussed.

Learning of sensory-motor schemas in a mobile robot

Abstract: A learning system is described which was used to control a simple robot vehicle and to autonomously learn behaviour patterns The system is loosely based on Becker's model of Intermediate Cognition