Showing papers on "Articulated robot published in 1988"

Robot geometry calibration

Abstract: Autonomous robot task execution requires that the end effector of the robot be positioned accurately relative to a reference world-coordinate frame. The authors present a complete formulation to identify the actual robot geometric parameters. The method applies to any serial link manipulator with arbitrary order and combination of revolute and prismatic joints. A method is also presented to solve the inverse kinematic of the actual robot model which usually is not a so-called simple robot. Experimental results performed by utilizing a PUMA 560 with simple measurement hardware are presented. As a result of this calibration a precision move command is designed and integrated into a robot language, RCCL, and used in the NASA Telerobot Testbed. >

A multistage-approach to the dynamics and control of elastic robots

Abstract: The control of an elastic robot along a reference trajectory is performed in several steps. An optimal reference path for a rigid robot is generated, taking into account any restrictions and arbitrary robot/trajectory configurations. Tracking of that path is improved by regarding the elastic influences of all links and joints. For the purpose the robot is modeled as an elastic multibody system. A control scheme is added which feeds back strain-gauge measurements at the elastic arms to damp remaining oscillations. These three stages together allow high performance control of an elastic robot, which is proven by measurements at a three-degree-of-freedom laboratory robot. >

Performance in adaptive manipulator control

Abstract: The authors explore the performance issues linked to the effective implementation of adaptive controllers for manipulators, which are nonlinear time-varying MIMO systems. Specifically, they detail issues of computational efficiency and recursive implementation, the treatment of closed chains, and minimal parameterizations. The authors also discuss extensions to interactions with mobile environments, whole-arm adaptive manipulation, adaptive impedance control, and adaptive control of spacecraft and space manipulators. The development is illustrated experimentally on a four-degree-of-freedom articulated robot arm, and suggests that the range of application of adaptive tracking controllers may extend well beyond adaptation to grasped loads. >

Cleaning robot control

Abstract: A small and lightweight cleaning robot powered from the AC power supply is produced for testing purposes The robot provides a cable-length control function which prevents tangling of the cables during traveling, an ultrasonic sensor function which detects obstacles and dodges them, and a distance measuring function which makes it possible to run parallel to the wall In a simple room with few obstacles, the robot can travel even if it does not incorporate information but in areas with complicated placement of obstacles, it is necessary to teach the robot the obstacle positions and the room size in advance >

An intelligent robotic system for rehabilitation of joints and estimation of body segment parameters

Abstract: An an application of robotics in physical rehabilitation therapy, a robotic system consisting of two planar robot arms, each with two degrees of freedom, is considered. This robotic system, when coupled across a human joint, provides a vehicle for rehabilitation of the joint following surgery or trauma. A novel approach for estimation of body segment parameters is formulated that uses state and output information from the robot system to improve these estimates. In addition, redundant sensors are used to improve the accuracy of the estimates. The dynamic equations for a single robot arm are provided and the system is simulated. Therapeutic applications of the robotic system are discussed and the sensitivity of the measured forces with respect to the robot arm joint angles is studied in order to find an optimum orientation of the system for the best possible estimation. The application of this system to both rehabilitation and sports medicine is also discussed. >

Stability criteria for robot compliant maneuvers

Abstract: A nonlinear approach for the stability analysis of robot manipulators in constrained maneuvers is presented. Stability of the environment and the manipulator taken as a whole has been investigated, and a bound for stable manipulation has been derived. The authors show that for stability of the robot, there must be some initial compliancy either in the robot or in the environment. The general stability condition has been extended to the particular case where the environment is very rigid in comparison with the robot stiffness. The stability analysis has been investigated using unstructured models for the dynamic behaviour of the robot manipulator and the environment. This unified approach of modeling robot dynamics is expressed in terms of sensitivity functions as opposed to the Lagrangian behavior of all the elements of a robot manipulator (i.e., actuators, sensors, and the structural compliance of the links) in addition to the rigid body dynamics. >

A new architecture for direct drive robots

Abstract: A practical architecture, using a four-bar-linkage, is considered for the University of Minnesota direct-drive robot. This statically-balanced direct-drive robot has been constructed for stability analysis of the robot in constrained manipulation. As a result of the elimination of the gravity forces (without any counterweights), smaller actuators and consequently smaller amplifiers were chosen. The motors yield acceleration of 5g at the end point without overheating. High torque, low speed, brushless AC synchronous motors are used to power the robot. Graphite epoxy composite material is used for the construction of the robot links. A four-node parallel processor is used to control the robot. The dynamic tracking accuracy with the computed torque method as a control law has been derived experimentally. >

Method for positioning a robotic work system

Abstract: A robotic work positioning system includes a programmed, powered robot, and a non-powered arm which is locatable at various positions in three dimensional space by means of the powered robot. A mating interconnection is provided on the non-powered arm whereby the non-powered arm may be accurately engaged and positioned by the powered robot for holding a part or workpiece at an accurately predetermined location. Together with the powered robot, the non-powered arm facilitates the accurate assembly of component parts. One or more non-powered arms can be used to generate three dimensional tooling which can be altered robotically.

Robot articulation joint

Abstract: An articulated robot joint includes a coupling member 13 having a hollow cylinder 13a rigidly mounted to a lower arm 2 and rotatably journaled to an upper arm 1. An offset crank 13c extends from one end of the cylinder, and has a mounting hub 13d at the end of a radial arm thereof coupled to an axially disposed output shaft of a motor and harmonic drive unit 5, 6. A power/control cable 3 is threaded through the hollow interiors of the arms, and traverses the joint via the hollow cylinder.

Multiple-articulated robot control apparatus

Abstract: A multiple-articulated robot control apparatus eliminates robot arm vibration by feedback-compensating disturbance due to interference torque when the robot arms are driven. The apparatus includes an arithmetic circuit (8) for computing mutual interference torque values for respective ones of the arms, a status observing circuit (2) for reproducing a status variable from a torque command and actual velocity of each servomotor, a conversion circuit (4) for converting an output of the status observing means into a corrective value of torque produced by disturbance acting upon the servomotor, and a correcting circuit (9) for correcting an error signal of the torque command of the servomotor by the converted corrective value and the interference torque value. Disturbance of each arm with regard to driving torque is eliminated. The apparatus is adapted to correct estimated disturbance torque.

Control of articulated robot arm with sensory feedback: laser beam tracking system

Abstract: A method for the trajectory tracking control of an articulated robot arm using sensory feedback is presented. First, a general control algorithm for such a problem is presented. To implement sensory feedback effectively, the dynamics of a robot arm is described in the task coordinate system. Then the dynamics of the robot arm in the task coordinate system are linearized using nonlinear feedback. Because the linearization cannot be done completely because of variations and identification errors of the physical parameters of a robot arm, a robust controller is designed so that the effect of parameter variations and errors can be lessened. The control law is shown to be simplified by the use of high-gain feedback. The simplification can make the implementation of the control law very easy. The proposed algorithm is applied to the trajectory-tracking control of an articulated robot arm using a laser beam. The experiments show that the proposed algorithm works well for such a sensory feedback system. >

The unified formulation of constrained robot systems

Abstract: Four types of constrained robot systems are analyzed: the robot in contact with its environment, the robot with a jig band, two robots carrying a common load, and the robot with internal constraints A unified formulation of the systems is given using singular systems of differential equations The formulation poses problems in controller design, trajectory planning, and system simulation that require further work >

The Control of an Elastic Manipulation Device using DSP

Abstract: In fast robots with conventional control, the elasticities of gears and robot arms frequently result in disturbing vibrations around the desired tracks. These vibrations can only be counteracted by means of a precise system description and a tailored control concept. Starting with a specially constructed three-joint elastic articulated robot, computer support is used to * set up the nonlinear equations of motion, * identify the system parameters, * optimize a controller structure designed for the overall system and to * implement the controller with fast DSP hardware. Experimental tests with the designed control show considerable improvements on conventional approaches when fast tracking is considered.

Method and instrument for measuring object using multi-articulated robot

Abstract: PURPOSE: To easily and accurately measure an object by providing angle detectors which can detect the angle between turning arms to each articulation directly or indirectly through rotation transmitting sections. CONSTITUTION: Angle detectors 20 which can detect the angle between turning arms 10 are provided to each articulation directly or indirectly through rotation transmitting sections 14. Since the rotational angle of the rotary shaft 19 of the secondary measuring turning arm 10 of a reduction gear 17 can be detected directly with the detectors 20, the hysteresis quantity, such as backlash, etc., of the reduction gear 17 can be detected and no positioning error occurs. An angular moving quantity correcting section has a function for correcting a mechanism error produced in the process of manufacturing a robot, namely, a turning arm length machining error, a center deviation error between each rotary shaft 19, bending error of each turning arm 10, etc. In addition, the correcting section also has a function for correcting the extending quantity of the arm 10 due to a temperature difference if required. Therefore, a mechanism error, a bending error, and an error produced by a temperature difference can be corrected. COPYRIGHT: (C)1990,JPO&Japio

Industrial robot device including a robot and a processing machine

Abstract: An industrial robot device in which deviation between an offline-teaching instruction and an actual movement of a robot according to the instruction can be eliminated. The elimination of deviation is accomplished by adjusting absolute X, Y and Z axes of software for driving the robot with respect to those of a processing machine which operates together with the robot.

Vision Guided Robots For Automated Assembly

Abstract: A vision guided robot for assembly is defined to be a robot/vision system that acquires robotic destination poses (location and orientation) by visual means so that the robot's end-effector can be positioned at the desired poses. In this paper, the robot/vision system consists of a stereo-pair of CCD array cameras mounted to the end-effector of a six-axis revolute robot arm. From a systems point of view, accuracy issues of the vision system, the robot, and the manufacturing requirements are considered for the development of automated calibration methodologies for local and global work volumes of the robot/vision system. Resulting accuracy of local calibration on the order of 1.5 mm is sufficient for many automotive assembly applications. Multiple component assembly and robotic fastening has been demonstrated with the developed vision guided robot.

Distributed Parameter Models of Flexible Robot Arms

Abstract: The modelling of a flexible robot arm is concerned with its rigid body motion as well as its oscillation due to the elasticity of the arm [1-4]. As the elastic deformation is distributed along the arm, it is obvious that this system is a distributed parameter system. Although a set of partial differential equations is presumed to be the best model for this system, it is limited to a relatively low frequency oscillation of a homogeneous, simply shaped arm. In the case of a more complicated flexible arm, the partial differential equation model is not necessarily advantageous, and another method such as the finite element method will be used. First, this paper presents the detailed development of the partial differential equations and boundary conditions for two models of a flexible robot arm. One is a rigorous model obtained through the use of Timoshenko beam theory, which takes into account the effect of transverse shear deformation and rotary inertia; the other is a simpler and more frequently used model ...

The GEC Tetrabot-a serial-parallel topology robot: control design aspects

Abstract: GEC has developed a serial-parallel configuration robot called the 'Tetrabot' based on a geometric configuration which makes it possible to employ light but rigid moving parts. This leads to a six degree-of-freedom robot capable of very precise and rapid movements over a working volume of lm/sup 3/. In the paper the prototype robot is analysed from the viewpoint of the control engineer. The initial design of the robot incorporates a control strategy based on the assumption that the motion of each of the six joints is decoupled. Linear PID controllers are used to control the position of each joint. The effectiveness of this approach is evaluated. Proposals for future work in refining the design of the Tetrabot control system are set out.

Joint structure of industrial articulated robot for laser apparatus

Abstract: PURPOSE:To improve the safety of the laser robot by providing conduits for a laser optical path disposed to a 1st robot arm to the center of relative rotation of the 1st and 2nd robot arms and forming and disposing a wiring cable in a spiral state to the outer periphery thereof. CONSTITUTION:The 1st robot arm 26 is mounted to the peak part of a column 24 and the 2nd robot arm 28 which can swivel horizontally is disposed to the front end 26a thereof. The laser light passes the inside of a hollow stationary shaft 54 erected from the arm 26 into the arm 28 and arrives at a laser output part 34 by passing the conduits 50, 52, 90 and reflecting mirrors 84, 86, 88, 94. Further, the cable 41 enters an inlet 58a and is spirally wound around the outer peripheral surface of the hollow shaft 54, by which the cable is wired to a motor MZ in the 2nd arm 28. The laser optical path is built into the robot machine body and further the required wiring is executed without generating tension and excess force on the cable 41 and, therefore, the safety of the laser robot is improved.

Method of directly teaching a horizontal arm type multi-articulated robot and an apparatus for carrying out same

Abstract: An articulated industrial robot has an articulated horizontal arm assembly which includes horizontal arms (20), a vertically movable shaft (20) mounted on the extremity of the horizontal arm assembly, and a motor for driving the vertically movable shaft. When directly teaching motions to the vertically movable shaft through a direct teaching operation by an operator, the current control unit of a motor control unit for driving the motor for driving the vertically movable shaft is disconnected from a signal line connected to a robot control unit, and a torque calculating circuit is provided for deciding a motor torque corresponding to the sum of the weight of the vertically movable shaft and the respective variable weights of an end effector attached to the lower end of the vertically movable shaft. A workpiece held by the end effector is connected to the current control unit to compensate the load torque of the vertically movable shaft with the torque of the motor so that the operator is able to carry out the direct teaching operation while substantially no load is imposed on the operator.

Articulated robot controller.

Abstract: An articulated robot controller of the invention removes vibration from the robot arm by feedback compensation of the disturbance caused by interference torque when the robot arm is driven. The controller comprises operation means (8) which operates mutual interference torque value for each arm, condition observation means (2) for reproducing condition variables from the torque instruction of the servo-motor and the real speed thereof, conversion means (4) which converts the output of the condition observation means into a corrected value of torque caused by disturbance to the servo-motor, and correction means (9) which corrects a deviation signal of torque instruction in the servo motor relying upon the corrected value thus converted and the above interference torque value.

Direct-drive-type multi-articulated robot

Abstract: A direct-drive-type multi-articulated robot comprising: a stationary support shaft (14), a cylindrical rotary casing (16) surrounding the stationary support shaft (14), a first robot arm (18) joined to the upper end (16a) of the rotary casing (16), a second robot arm (20) pivotally joined to the extremity of the first robot arm (18), a direct-drive motor (Mθ) interposed between the lower end of the rotary casing (16) and the lower end of the stationary support shaft (14) to drive the rotary casing (16) and the first robot arm (18) together for turning motion, a brake gear (24) interposed between the upper end (14a) of the stationary support shaft (14) and the first robot arm (18) to arrest the turning motion of the first robot arm (18), and an encoder (26) for detecting turning motion, interposed between the upper end (14a) of the stationary support shaft (14) and the first robot arm (18).

Robot arm structure of horizontal, articulated robot

Abstract: PURPOSE: To make it possible to use a robot for both on-the-floor-position and hanging- position only through reattaching the robot arm by allowing a static, outer casing of a swing-driving-mechanism, which is attached to the rear, end part of the second robot arm, to freely be attached to or detached from an upper installing surface or a lower installing surface, which is formed on the upper-end or lower-end of the first robot arm. CONSTITUTION: When a horizontal, articulated robot 10 is installed on the floor, an installing surface 48a, which is provided on a static, outer casing 44 of a swing driving mechanism 44 of the second robot arm 42, is abutted on and connected to the lower installing surface 28b of the first robot arm 12, and bolts 30 are inserted into the casing 48 from the upper, installing surface (28a) side to fix the casing 48. Meanwhile, when the horizontal, articulated robot 10 is installed onto the ceiling surface, the installing surface 48a of the static, outer casing 48 of the swing driving mechanism 44 is abutted on and connected to the upper, installing surface 28a of the first robot arm 12, and bolts 30 are inserted into the casing 48 from the lower, installing surface (28b) side. This structure for reversely connecting the static, outer casing 48 to the installing surface 28a or 28b gives highly precise connection, thereby preventing the torsion or off-centered connection between two robot arms. COPYRIGHT: (C)1989,JPO&Japio

Systematic optimisation of a robot arm structure

Abstract: To achieve high working speed and high positional accuracy, the weight of a robot arm must be reduced.