Showing papers on "Robot published in 1983"

Conventional controller design for industrial robots — A tutorial

Abstract: Industrial robots are serial link manipulators whose dynamic characteristics are highly nonlinear. By controlling each link or joint individually, employing the conventional technique to design linear feedback controllers for the robot is possible. The gravitational force and force interactions between joints are suppressed by precalculated feedforward compensation. To ease the computational burden, the compensating signals are either approximated or their computational formulas are simplified.

Kinematics of robot wrists

Abstract: Robots for use in assembly and other interactive tasks must be able to respond to both forces and velocity com mands within their workspace. By considering a general six-joint robot we show that all such robots are limited in their ability to respond in orientation to feedback commands. We also show that it is simple to predict, if not to avoid, these regions of degeneracy in which the manipulator loses a degree of freedom.

An anatomy of industrial robots and their controls

Abstract: In the United States, commercially available industrial robots perform very well in limited areas of industrial tasks such as arc welding, paint spraying, etc. These tasks mainly involve synchronization but no task interaction. A close examination of the basic structure and controls of the robots reveals their resulting limitations which lead to unnatural specifications and inefficient performance of task interactions. It is our opinion that, to expand the range of robot tasks to include labor intensive jobs such as product assembly, sensors of multiple purposes must be added onto the robots and integrated into their control systems. Computer command language must be developed to enable nonexpert users to operate the robots, and a work-method must be available for analyzing robot time-motion so that the robots can be programmed to achieve best efficiency with least production cost.

Design of Direct-Drive Mechanical Arms'

Abstract: : This paper describes the design concept of a new robot based on the direct-drive method using rare-earth DC torque motors. Because these motors have high torque, light weight and compact size, we can construct robots with far better performance than those presently available. For example, we can eliminate all the transmission mechanism between the motors and their loads, such as reducers and chain belts, and construct a simple mechanism (direct-drive) where the arm links are directly coupled to the motor rotors. This elimination can lead to excellent performance: no backlash, low friction, low inertia, low compliance and high reliability, all of which are suited for high-speed high-precision robots. First we propose a basic configuration of direct-drive robots. Second a general procedure for designing direct-drive robots is shown, and the feasibility of direct drive for robot actuation is discussed in terms of weights and torques of joints. One of the difficulties in designing direct-drive robots is that motors to drive wrist joints are loads for motors to drive elbow joints and they are loads for motors at shoulders. To reduce this increasing series of loads is an essential issue for designing practical robots. We analyze the series of joint mass for a simplified kinematic model of the direct-drive robots, and show how the loads are reduced significantly by using rare-earth motors with light weight and high torque. We also discuss optimum kinematic structures with minimum arm weight. Finally, we describe the direct-drive robotic manipulator (CMU arm) developed at Carnegie-Mellon University, and verify the design theory. (Author)

Apparatus and method for robot calibration

Abstract: Robotic apparatus is guided by a computer 14 which is calibrated by cameras 20, 21, 22 mounted on the robot arm 11 which view targets 15, 16 fixed at a work station 13 and comprising a pattern of four dots. The viewing takes place as the robot arm approaches the work station to carry out the intended operation and the sensing of any deviation relative to a predetermined target pattern is transmitted to the computer 14 to re-set the robot's computerized guidance system.

Adaptive Visual Servo Control of Robots

Abstract: Visual servo robot control systems provide feedback on the relative end-effector position of a robot. They offer an interactive positioning mechanism which depends upon extraction and interpretation of visual information from the environment. In this paper, we characterise visual servo systems by the feedback representation mode, position-based or image-based, and the joint control mode, closed-loop or open-loop. The design problems posed by nonlinear and coupling transformations introduced by visual tracking systems are discussed, and a design strategy which utilises adaptive control, direction detection, and a logical control hierarchy is proposed.

Off-line programmable robot

Abstract: Machine operations are performed by a robot at a plurality of locations on a workpiece based on off-line data. The off-line data is corrected based on two levels of workpiece/robot alignment. First the robot determines the orientation of a fixture to which the workpiece is mounted by "touching-off" on known reference points (touchblocks) on the fixture. Coordinate data for the location of local features on the workpiece is corrected based on the first level of alignment and the positions of the local features are then sensed to provide a coordinate transformation for subsequent application to nominal machine operation location coordinates. The local features may be preassembly rivets and provide for individualized robot response on a workpiece-by-workpiece basis.

Vibration Absorption Control of Industrial Robots by Acceleration Feedback

Abstract: This paper describes an electrical control method of absorbing arm vibrations of industrial robots Arm vibration problems are divided into two categories: resonance vibration phenomenon depending on actuator velocity and transient oscillations caused by acceleration change of actuators Because resonance frequency of an industrial robot changes more than double due to the arm posture, mechanical vibration absorbing methods may not be easily utilized The method applied in this paper is to compose dampers as electric manners by utilizing arm acceleration feedback to actuators of an industrial robot Acceleration sensors are attached on three axes which construct a robot arm Acceleration signals are fed back to the corresponding actuators passed through phase compensation circuits By experiments applied to an industrial robot, this method has been proved to be effective in eliminating both resonance and transient vibrations According to this control, a smart motion industrial robot which does not have resonance characteristics and operates speedily and smoothly has been realized

Is Dynamic Control Needed in Robotic Systems, and, if So, to What Extent?

Abstract: The problem of dynamic control in robotic systems is considered in this paper. Robotic systems are essentially dynamic systems. The problem is whether is it necessary to take dynamics into account in controlling them, and, if so, to what extent. In cases of slow motion and mechanical configuration with weakly coupled subsystems (mechanical degrees of freedom ) it is not necessary to solve the control task dynamically. In cases of faster motion and mechanical configuration with strongly coupled subsystems, however, the control task is essentially dynamic and we suggest some control strategies which include complete dynamics of the robot. Several examples of locomotion and manipulation robots' control synthesis are presented. We present postural stabilization of biped robot, as a representative of dynami cally unstable locomotion robots. The control synthesis for three types of manipulation robots is described in order to show how the extent of inclusion of dynamics in the control depends on the mechanical ...

A System for Programming and Controlling Sensor-Based Robot Manipulators

Abstract: This paper describes an approach to programming and controlling robot manipulators which facilitates the use of sensory information. Robot actions are specified by declaring software servo processes which control the robot's various degrees of freedom. These servo processes can involve position, orientation, force, and torque information from the robot itself, or data from external sensors. Robot tasks are programmed by dynamically modifying the servo processes or by changing set points to these processes. Condition monitors, which have access to program and sensory information, detect the completion of program steps.

Robotics, applications and social implications

Abstract: Robots are expected to dramatically alter the U.S. economy in the 1980s. In this assessment of their effects on everyday life, the authors examine the scope of the robotics revolution and provide recommendations for a smooth introduction of robots into American industry.

An integrated robot system architecture

Abstract: This paper describes the architecture of a robot system designed both to work in an integrated manufacturing environment and to support continuing research in programmable automation. Major system components include a controller, robot and sensor hardware, operator's pendant, and system software. A new high-level interactive language, AML, allows the user to combine manipulation, sensing, computational, and data processing functions provided by the system. Important aspects of the system design objectives, major functional components, and the AML language are described, and examples drawn from an actual production application are used to illustrate the interrelationship of the topics discussed.

Robot Manipulator Control.

Abstract: : This report presents a synthetic approach for calculating the control of robot manipulators. The initial control problem is broken down into linear control and modelling problems. The approach allows derivation of numerous schemes (adaptive or not) of control proposed in the literature and suggests new schemes. It is shown that the problem of modelling is difficult but is less crucial if one can synthesize robust controls that are not sensitive to errors of modelling.

Model structuring and concept recognition: two aspects of learning for a mobile robot

Abstract: We present here a method for providing a mobile robot with learning capabilities. The method is based on a model of the environment with several hierarchical levels organized by degree of abstraction. The mathematical structuring tool used is the decomposition of a graph into its k-connected components (k=2 and k=3). This structure allows the robot to improve navigation procedures and to recognize some concepts, such as a door, a room, or a corridor.

Vector-algebra approach to extract Denavit-Hartenberg parameters of assembled robot arms

Abstract: The Denavit-Hartenberg parameters characterize the joint axis systems in a robot arm and, naturally, appear in the transformation matrices from one joint axis system to another. These parameters are needed in the control of robot arms and in the passage of sensor information along the arm. This paper presents a vector algebra method to determine these parameters for any assembled robot arm. The idea is to measure the location of the robot hand (or extension) for different joint angles and then use these measurements to calculate the parameters.

Concurrent programming of intelligent robots

Abstract: Real time intelligent robots usually consist of more than one processing unit (pu) to ensure parallel operation of several functions. Each pu in a robot executes repetitive monitoring and controlling operations as well as information exchange to and from other pu's. Since timing of each operation is independent of others, if the robot operating software supports concurrent process facilities, it would be helpful in robot programming. A self-contained robot "Yamabico 9" has been constructed to be a tool for investigating how a mobile robot understands the outer world. In order to support software production on the robot, Robot Control System (RCS) has been implemented, including simple job commands and a supervisor call (SVC) system. The concurrent process monitor is a part of RCS and some of SVC's are for these facilities. The monitor adopts a "message sending" method to synchronize execution of two processes and to exchange information between processes and pu's. An example of a concurrent process program, "walk along left walls", is given to demonstrate the describing power of our system.

Velocity method of controlling industrial robot actuators

Abstract: A method of controlling an industrial robot wherein velocities of the actuators for the robot are based on the velocity of a robot hand moving along a predetermined path of travel. When the velocity of any single actuator exceeds its ability, the velocities of the actuators are revised so as to bring the velocities of all the actuators within their abilities, thereby revising the velocity of the robot hand along its path of travel. Calculation of the velocity of each actuator may be carried out based on the position and posture of the robot hand and a Jacobian matrix.

Auxiliary function command presequencing for a robot controller

Abstract: A control system for a work robot having a number of articulated links including a controller for driving the links under closed loop servo control in response to a sequence of recorded link position commands read from a robot program memory The sequence of link position commands is produced in a training session by an operator manually manipulating a robot simulator, or training arm, through a series of work-performing motions which are to be duplicated by the work robot The sequence of link position commands produced by manual manipulation of the training arm during the training session is stored in the robot program memory When the work robot is subsequently driven under closed loop servo control in response to the program stored in the robot memory, the controller also executes auxiliary functions, such as movement of a work piece operated upon by the work robot, in response to auxiliary function commands which are also stored in the robot program memory In order to properly store the auxiliary function commands in the robot program memory, the auxiliary function commands are loaded in an auxiliary function memory prior to a training session so that they can be read out in a desired sequence

Device for compensating errors on machine tools or measuring machines and on industrial robots

Abstract: The invention relates to a device for compensating errors on machine tools or measuring machines and on industrial robots with at least one path-measuring system and a device for display or a machine control for further processing of the measured values. In order, without complicated and additional adjusting devices, to compensate on the machine manufacturing-dependent, load-dependent and temperature-dependent dislocations, with the aid of microprocessor technology, the path-measuring system of the machine tool or measuring machine or of the industrial robot has a computer connected downstream, which overlays the actual values measured by the path-measuring system, before their display or further processing, with correction values which are worked out beforehand for all possible positions, thermal states and load conditions and are stored in memories assigned to the computer responsible for the compensation function or are calculated by this computer depending on the prevailing operating parameters.

Reasoning about the spatial relationships derived from a RAPT program for describing assembly by robot

Abstract: The network reduction systen of RAPT, an offline object level language for programming robot assembly tasks is described in this paper. The task description is converted into a relational network with the positions of bodies as nodes, and relationships between positions as links. Rewrite rules based on the intersection and conposition of relations are used to simplify the network.