Showing papers on "Articulated robot published in 1986"

Time-optimal motions of robots in assembly tasks

Abstract: For a cylindrical, and a spherical robot, and a robot with a horizontal articulated arm with two links, time-optimal unconstrained trajectories for arbitrary fixed initial and final positions are calculated. The exact equations of motion are utilized. The controls (torques and forces) are limited. The general structure of the optimal solution is discussed and explained physically for each robot. The importance of such analyses during the mechanical design of a robot is pointed out. The reduction of the duration of an optimal motion, compared to more straightforward and natural ones, and hence the increase of the productivity of the robot in an assembly cycle can be considerable. The numerical examples include the "Automelec ACR" and the "IBM 7535 B 04" robots.

Tutorial on robotics

Abstract: Basic fundamentals in robotics are presented in this tutorial. Topics covered are as follows: robot arm kinematics; robot arm dynamics; planning or manipulator trajectories; servo control for manipulators; force sensing and control; robot vision systems; robot programming languages; and machine intelligence and robot planning.

Dynamic Simulation of a Leadscrew Driven Flexible Robot Arm and Controller

Abstract: High performance requirements in robotics have led to the consideration of struc­ tural flexibilty in robot arms. This paper employs an assumed modes method to model the flexible motion of the last link of a spherical coordinate robot arm. The model, which includes the non backdrivability of the leadscrews, is used to in­ vestigate relationships between the arm structural flexibility and a linear controller for the rigid body motion. This simple controller is used to simulate the controllers currently used in industrial robots. The simulation results illustrate the differences between leadscrew driven and unconstrained axes of the robot; they indicate the trade-off between speed and accuracy; and show potential instability mechanisms due to the interaction between the controller and the robot structural flexibility.

Modelling and control of flexible robot arms

Abstract: This paper surveys modeling and control problems of flexible robot arm systems. The flexibilities of the robot arm system are divided into two categories, namely the flexibility due to the nonlinearity in the drive system and the flexibility due to the elasticity of the arms which has properties of distributed parameter system. For these two systems, various modeling methods and control laws are reviewed, along with a discussion of the effect of the sensor location.

Coordinate Transformation: A Solution Algorithm for One Class of Robots

Abstract: One of the most important features of an advanced control system for articulated robots is the capability of transforming the work space coordinates, which naturally characterize any robot task, into the corresponding joint coordinates, on which control actions are developed. For each task, the coordinate transformation problem consists in calculating one trajectory in the joint space which corresponds to the end effector trajectory, usually given in the Cartesian space. While simple kinematical structures allow for closed-form solutions, there is a class of robots for which this is not true. Typical articulated robot structures have three revolute joints at the end effector; the geometric parameters of these joints actually determine the spatial configuration of the last axes of motion. The large majority of today's nonredundant structures have three intersecting axes at the end effector, and closed form solutions do exist in this case. If the axes intersect two-by-two, as in some rather common arm design, an exact solution seems not to exist. A quite different solution algorithm is established, as compared to the trigonometric approach widely adopted so far, which yields solutions in case of two-by-two intersecting axes. The convergence of the algorithm along any trajectory is proved. Effectiveness of the proposed technique can be argued by the fact that it only makes use of direct kinematics, thus resulting in a contained computational burden. A robot prototype of the kind described above is taken as a reference in order to discuss digital implementation and develop numerical examples.

A methodology for specifying and controlling compliant robot motion

Abstract: A methodology is developed to integrate a sixdimensional force/torque sensor into a robot programming and control system. It consists of : [1] a formalism for specifying compliant motion tasks, based on orthogonal task frames with force, velocity, and tracking directions, and provided with tools to model the task kinematics; [2] a strategy for the task execution which makes use of external control loops closed around the robot positioning system. Several experiments show the applicability of the methodology.

Modeling and control of a mobile robot subject to disturbances

Abstract: This work is concerned with the modeling and control of a robot that is mounted on a moving platform. The platform is subjected to random disturbances along its pitch, yaw, and roll axes. A controller is designed so that the robot can carry out tasks with respect to the robot base frame. In general, the problem is to investigate the various modeling and control issues involved in robotic systems subjected to time varying disturbances.

Robotic work positioning system

Abstract: A robotic work positioning system includes 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.

Two robot arms in assembly

Abstract: When two robot arms execute coordinated motions in assembly, collision between the two end-effectors cannot be avoided. The collision effects on the robot motions are studied in this paper. Firstly, the joint velocities of the two coordinating arms have abrubt changes at the instant of collision. Secondly, an impulsive force exerted on the end-effector is generated. The magnitude and the direction of the impulsive force depend on the relative position and orientation between two collideing end-effectors. Therefore the impulsive force can be used to detect the position and orientation errors between two coordinating arms. A wrist force sensor is suggested to be installed at the wrist of each robot arm. The information produced by the wrist force sensors can then be used to adjust the relative position and orientation of the two robot arms in assembly.

System for setting workpiece Cartesian coordinate system of robot

Abstract: Provided is a system for setting a workpiece Cartesian coordinate system in a robot. In teaching the nose position (TCP) of a working member (tool) mounted on the hand of an articulated robot, the user moves the tool mounted on the hand to teach a reference point, any point on a predetermined axis and a third point defining a plane together with the other two points, whereupon a single coordinate system is specified by the position data indicative of these three points P1, P2, P3. A plurality of tool coordinate systems having a fixed relationship to the reference coordinate system of the robot can be set.

Articulated head for an industrial robot and a robot equipped with a head of this type

Abstract: An articulated head for an industrial robot has three axes of rotation and three frames, the movements of rotation of which are controlled by only two driving elements carried by the fixed portion of the wrist which is connected to the robot arm.

Vertical integration for robot assembly cells

Abstract: Vertical integration of transformation of abstract assembly task descriptions into task execution commands is needed to overcome the fundamental factors which limit the widespread application of current robotic systems. These factors are the requirements for precise control of the robot task environment, custom-designed fixtures and end-effectors, and on-site robot control programming. These requirements arise because current robotic systems do not have an understanding of the robot cell environment. Further, these systems are not able to react rationally to non-deterministic events which occur during task execution. A research plan which is aimed at the systematic incorporation of limited amounts of machine intelligence into robot task planning and execution is outlined.

System for controlling acceleration and deceleration of horizontally articulated robot

Abstract: A system for controlling acceleration and deceleration of a horizontally articulated robot computes the distance from the center of rotation of the robot (A) having a plurality of arms (3, 5) angularly movable in horizontal planes to a reference position such as a wrist (51) at the distal end of the arms (3, 5), and establishes an acceleration for the movement of the distal end of the arms (3, 5). A servomotor for angularly moving the arms (3,5) can effectively be utilized and the arms (3, 5) can quickly and smoothly be moved.

Introduction to Robotics

Abstract: (Decision-making) Fig. 1.9 A set of related topics in robotics with a motion-centric theme. 1.6 Issues in Robotics Robotics, or the study of robots, is an engineering discipline. Functionally, a robot is a physical agent which is capable of executing motion for the achievement of tasks. A robot's degree of autonomy depends on its ability to perform the ordered sequence of perception, decision-making and action. As we know, a robot's dynamics in motion execution is dictated by mechanical energy consumption in connection with kinematic constraints imposed by the robot's mechanisms. Literally, the definitions of kinematics and dynamics are as follows: Definition 1.9 Kinematics is the study of motion without consideration of force and torque, while dynamics is the study of motion in relation to force and torque. Therefore, the unifying concept in robotics is motion, being a visible form of action. As illustrated in Fig. 1.9, the major issues in robotics will logically include: 1.6.1 Mechanism and Kinematics From a mechanical point of view, a mechanism is a set of linkages without an actuator. The purpose of a mechanism is to impose kinematic constraints on the types of motion the mechanism can deliver at a particular point. By default, this particular point is at the tip of an end-effector. In general, a mechanism consists of joints and links. In robotics, a link 22 The Fundamentals of Robotics: Linking Perception to Action is a rigid body inside a mechanism, while a joint is the point of intersection between any pair of adjacent links. Any changes in the relative geometry among the links will induce a specific type of motion. Therefore, it is important to study the relationship between the motion parameters of the linkages and the motion parameters of a particular point on the mechanism. This study is the object of robot kinematics. There are two problems with robot kinematics: • How do we determine the motion parameters of a particular point on the mechanism from the knowledge of the motion parameters of the linkages? This is commonly called the forward kinematics problem. • How do we determine the motion parameters of the linkages necessary to produce a desired set of motion parameters at a particular point on a mechanism? This is known as the inverse kinematics problem. In the mechanical domain, any motion is produced by the conversion of mechanical energy. The study of the relationship between motion parameters and …

Towards multi-processor and multi-robot controllers

Abstract: We describe in this paper a new approach in the design of robot controllers This system will allow the programming and the control of complex assemblies operations in which one or two robots and a positioning and force sensitive table will be involved The open hardware systems or any kind of sensor In this system, all the devices which are locally controlled by one or more processors can be programmed from a single workstation in which most of the existing tools needed to program complex robotic applications are available: robotic oriented and general purpose languages, graphic simulation, multi-window editors The proposed controller is built around a 68000 family based workstation (SM90) tied to a set of heterogeneous industrial buses, to form a hierarchical and distributed environment in which each of the physical device disposes of its own local controller

The Anatomy and Function of the Laboratory Robot

Abstract: The design and operation of a typical user-programmed laboratory robot system is discussed. A laboratory robot is defined as a integrated system of robot arm, controller and laboratory peripherals. The capabilities together with limitations of the current generation of robots and the design specifics of two typical laboratory robot systems, the Zymate and the Perkin-Elmer Masterlab, are presented.

Position shift correcting system of welding robot

Abstract: PURPOSE:To provide the titled position shift correcting system by detecting the shifting quantity from the standard position of a work position with utilizing the detecting means to detect the work position from the electrifying condition between a welding torch and work and by enabling to correct suitably the taught welding line. CONSTITUTION:The position shift correcting system 1 of said welding robot is composed of an articulated robot 2 and the welding torch 4 fitted to the wrist part 3 of the robot 2 and a control means 5 and is to weld a work W. The means 5 memorizes the position data of the standard welding line in the work W being placed on a standard position by the electric circuit having a microcomputor as its center, also equips the detecting function to detect by a short circuit current whether the tip 4a of the torch 4 touches the work W or not. The means 5 provides further the position shift correcting function to motion as shown in figures a, b. Due to the taught welding line being corrected with setting to the position shift therefore even when the position of the actual work W position is shifted from the prescribed standard position, the welding can be performed correctly along the necessary welding line.

Control system for robot

Abstract: PURPOSE: To command a control signal for accurate driving torque to a servo- motor by judging whether or not a robot grips a work on an on-line basis and varying a motion equation. CONSTITUTION: The driving torque of the servo-motor which drives a manipulator through the intervention of a robot arm is computed from a motion equation corresponding to the weight of the work. In an assembly line where the robot is used actually, the weight and inertia of many works gripped by the hand of the robot are computed and stored previously and whether or not the robot hand grips the works or the kind of the works is judged to read corresponding inertia data, thereby compensating a driving torque command to the servo-motor. Consequently, the robot is easily controlled and arithmetic processing is also performed speedily. COPYRIGHT: (C)1988,JPO&Japio

System for controlling articulated robot

Abstract: A system for controlling articulated robot wherein a cycle which receives serial data from an external instruction device and a cycle which reversely converts the received serial data into correction data on each of the axes from orthogonal coordinates and distributes them, are executed in parallel by first and second operation units (CPU-a, CPU-b) in a robot control unit which is served with control target information on the articulated robot via a serial interface (11), in order to produce in real time a robot drive instruction that corresponds to said control target information maintaining a sufficiently short interpolation interval, and in order to control the operation of each of the axes.

Computer coordination of motion for omni-directional hexapod walking machines

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Articulated robot control device

Abstract: PURPOSE:To improve the productivity and the quality by detecting an arm position by a coordinate position detecting means, and detecting a coordinate position of a prescribed part on a rotary table by a prescribed part coordinate detecting means. CONSTITUTION:An articulated robot control device RC executes a prescribed work by making an articulated robot cooperation with a rotary table T. This control device RC is constituted of a coordinate position detecting means C1, a prescribed part coordinate detecting means C2, and a rotary table attitude calculating means C3. The coordinate position detecting means C1 detects an arm moving device RA of the robot R as a coordinate position of its coordinate system (R-XYZ), and the prescribed part coordinate detecting means C2 detects a prescribed part TA on the rotary table T by the coordinate system (R-XYZ). From plural prescribed part coordinates which have been detected in this way, an attitude of the rotary table T in said coordinate system is calculated by the calculating means C3. In this way, a data of the rotary table T can be converted to a data of the robot R, and they can be made to cooperate with each other smoothly.

Laser Sensor For Adaptive Welding

Abstract: An autosynchronized laser scanning mechanism is integrated in a compact, mobile unit mounted on a six axis, articulated robot wrist. This camera combines a new geometrical arrangement for improving the performance of optical triangulation with the latest solid-state laser and CCD sensor technology. The camera enables in-process, 3D mea-surements of the welded workpiece and the optimization of the robotic arc welding process. Joint and weld geometry analysis can be performed in real time with high precision, even during high current arc welding. This provides information about weld joint geometry in front of the arc (e.g. seam tracking) and behind the weld pool (e.g. inspection of finished welds), both of which are required for closed loop adaptive welding. High dimensional resolution combined with high signal to noise ratio provides an ideal tool for the further development of expert welding systems. Furthermore, the vision system can be used for the generation of 3D object data, which can be used in conjunction with a computer graphics system for offline robot programming.

Operation control device of articulated robot

Abstract: PURPOSE:To execute control easily and exactly to a desired operating direction and attitude by providing an operating means, and starting attitude pattern control means by designating an operating axis of an articulated robot. CONSTITUTION:An articulated robot 2 is constituted of a base 3, a swiveling base 4, wrist axes 7, 8, etc., and driven by an operation control device 1. This operation control device 1 is constituted of an operating means 10 for applying various operating signals to the robot 2, an operation control means 11, a present state storage means 15, an attitude pattern storage means 19, an attitude pattern control means 18, etc., as shown in the figure. In this state, the attitude pattern control means 18 is started, and the attitude of an operating axis of the robot 2 is made to coincide with the corresponding attitude stored in the attitude pattern storage means 19. In this regard, a position and an attitude of an operating point of the robot 2 obtained by the attitude pattern control means 18 and a manual control means 12 are stored in the present state storage device 15, and it is stored successively in a teaching state storage means 16 by an operation of a teaching control means 13 which has passed through the operation control means 11.

A data structure and data base design for model driven robot programming

Abstract: A data structure is presented for model driven robot programming and motion simulation. Handling of device parallelism and construction of data bases containing the description of one or more robots, the world in which they operate and parts that are being handled are also presented. The system structure of the model driven robot programming and simulation system STAR (Simulation Tool for Automation and Robotics) incorporating this data structure is described.