Showing papers on "Articulated robot published in 1987"

Kinematic modeling for feedback control of an omnidirectional wheeled mobile robot

Abstract: We have introduced a methodology for the kinematic modeling of wheeled mobile robots. In this paper, we apply our methodology to Uranus, an omnidirectional wheeled mobile robot which is being developed in the Robotics Institute of Carnegie Mellon University. We assign coordinate systems to specify the transformation matrices and write the kinematic equations-of-motion. We illustrate the actuated inverse and sensed forward solutions; i.e., the calculation of actuator velocities from robot velocities and robot velocities from sensed wheel velocities. We apply the actuated inverse and sensed forward solutions to the kinematic control of Uranus by: calculating in real-time the robot position from shaft encoder readings (i.e., dead reckoning); formulating an algorithm to detect wheel slippage; and developing an algorithm for feedback control.

An anthropomorphic robot finger for investigating artificial tactile perception

Abstract: In this paper the design, implementation, and testing of an artificial tactile sensing system incorporating an articulated robot finger are presented. It was our primary aim in this work to set up the hardware and software tools necessary for investigating basic issues in artificial tactile perception.In the first part of the paper the criteria followed in the design of the robot finger and of its motor and sensory com ponents are outlined.The second part of the paper deals with the problem of defining a hierarchical architecture for the control of the ex ploratory finger. In this context, particular attention is de voted to the description of a set of tactile subroutines that are intended to replicate some of the basic sensory motor se quences adopted by humans for tactile exploration. The main features of the high-level planner, which is supposed to super vise the execution of those tactile primitives, are also discussed.Finally, experimental results that demonstrate the capabil ity of the robotic syste...

Hybrid position/Force control for coordination of a two-arm robot

Abstract: In this paper we discuss the control of cooperating tasks being done by two robotic arms. In order to control those tasks, we extend hybrid position/force control scheme presented thus far by various researchers for a single-arm robot. The point of the extension is formulation of kinematics and statics for a two-arm robot which is new in this paper. We define a unique system of workspace coordinates and, corresponding to the unique workspace, introduce an unique jointspace vector consisting of joint-vectors of the two arms. Using these work and joint spaces, we formulate kinematics and statics. Based upon this formulation, we successfully apply the hybrid scheme to the two-arm robot. A demonstration of the theory working on a real two-arm industrial robot and experimental data of simultaneous control of position and force proves the effectiveness of our method.

Redundant robot control for higher flexibility

Abstract: The joint velocities required to move the robot end-effector with a desired speed depend on the direction of motion. Robot's mobility, i.e., its ability to move, is better in the directions requiring lower joint velocities. When the robot is near a singularity configuration, the joint velocities required to attain the end-effector velocity in certain directions are extremely high. Thus arbitrary directional changes become more difficult. Robot's flexibility, defined as its ability to change the direction of the end-effector motion, is low in the vicinity of singular configurations. Addition of redundant joints can greatly enhance their flexibility. However, this requires a proper utilization of redundancy. A control scheme is presented to improve the flexibility of redundant robots. The feasibility and effectiveness of this control scheme are demonstrated through simulation.

Statically-balanced direct-drive robot arm

Abstract: A robot (10) includes a statically-balanced direct-drive arm (14) having three degrees of freedom, all of which are independent articulated drive joints, the driving axes of two of which intersect at the center of gravity of the arm to eliminate gravity forces on the drive system without counterweights.

Quasi-minimal computation of the dynamic model of a robot manipulator utilizing the newton-euler formalism and the notion of augmented body

Abstract: Real-time dynamic control of robot manipulators requires on-line computation of the dynamic model that expresses the generalized forces to be applied to their joints, as a function of their generalized coordinates, velocities and accelerations. To do this, this paper presents a method of computation of this model that uses a quasiminimal number of elementary arithmetical operations and that can be applied systematically to robot manipulators with a simple kinematic chain structure and revolute and/or prismatic joints. To reach this quasi-minimal number, use if primarily made of the following : * a computation that is intrinsic rather than extrinsic, analytical rather than numerical and iterative rather than developed ; * the Newton-Euler formalism rather than the Lagrangian one and * the notion of augmented body, generalized to this type of structure. An example demonstrates that the computation of the dynamic model of an industrial robot manipulator with six revolute joints (the most complicated case in practice) can be effected with less than 300 arithmetical operations (adds and multiplies).

The robot builder's bonanza: 99 inexpensive robotics projects

Abstract: The robot experimenter anatomy of a robot tools and supplies getting parts building robots of plastic building a basic wooden robot platform building a metal platform constructing high tech robots from toys build a Robotix-based robot build a Lego technic-based robot building a functionoid with Lego mindstorms all about batteries choosing the right motor for the job locomotion with DC motors locomotion with Stepper motors locomotion white Servo motors build a RoverBot build a six-legged walking robot build the HydraBot - walk'n roll! advanced locomotion systems an overview of arm systems build a revolute coordinate arm build a Servo motor-based robotic arm build a polar coordinate arm experimenting with Gripper designs adding the sense of touch fire detection systems robotic eyes collision detection and avoidance navigating through space remote control systems robot control via PC parallel port an overview of robot "brains" using the BASIC stamp and other microcontrollers robot control with 8051 single board computer creating your own PIC-based "Robobug". Appendices: sources reading robot information on the Internet interfacing Logic families and Ics construction charts.

Gross motion planning for a simple 3D articulated robot arm moving amidst unknown arbitrarily shaped obstacles

Abstract: This work continues the approach to sensor-based robot motion planning in an unknown environment first studied in [2,3] and further developed for various configurations of planar robot arms in [4,10]. The main idea of the approach is to reduce the problem to the analysis of simple closed curves on an appropriate two-dimensional (2d) manifold. We extend the same ideas to simple 3d arms with two revolute joints whose endpoints travel along 2d manifolds whereas their bodies operate in a "normal" 3d space. For such an arm, a path planning algorithm is described, its convergence is shown, and an example of the algorithm performance is given.

Robot arm having motion-limiting tether

Abstract: An electrical power interrupting tether system for a multiple-joint, anthropomorphic robot arm that substantially improves robot arm operational safety. The tether system includes a robot arm and auxiliary equipment power-interrupting electrical robot arm member by a set of braided steel wires. A pair of conventional robot arm and auxiliary equipment power-interrupting limit switches actuated by excessive rotational robot arm movement are also provided. Movement of the robot arm beyond a predetermined safety zone defined by each arm-member-tethering wire and the limit switch pair will cause electrical power interruption to both the robot arm and to auxiliary equipment associated therewith to thereby preclude potentially unsafe movement of the robot arm beyond the above-defined safety zone.

Unpositioned Workpieces Handling Robot with Visual and Force Sensors

Abstract: A robot which can handle unpositioned workpieces using a three-dimensional (3-D) vision sensor and a force sensor has been developed. It can pick up an unpositioned small connector and mount it correctly on a printed circuit board. This paper presents the robot system configuration and its operation

Computation of the effects of link deflections and joint compliance on robot positioning

Abstract: Actual trajectories of robot manipulators usually differ from the planned trajectories partially because of the effects of link deflections and joint compliance. This paper presents an efficient computation scheme to calculate the actual positions and orientations of the end-effectors of manipulators consisting of straight thin-walled hollow links and revolute joints, of which most contemporary robots are made up. Local principal coordinate frames are defined for deflection analysis. Displacements are computed using formulae derived from classical beam theory. For compliance analysis, the robot joints are considered as torsional springs, where the first order approximation is applied. A hypothetical two-link robot is used to demonstrate the techniques. Results are verified by analytical solutions, and the differences are less than 1% of the deflections.

Teachingless grinding robot depending on three force information

Abstract: When an industrial robot grinds a curved surface of a workpiece, an operator must teach the robot the contour of the surface accurately. This instruction, however, is a very troublesome job because of the large number of teaching points. This paper proposes a grinding robot that requires no teaching. The robot system consists of a manipulator mounted on a cylindrical grinding wheel on the end effector, instruments to measure the three different forces and a computer equipped with an A/D converter. The force information consists of the grinding torque and the two components of the grinding force which is applied to the grinding wheel from the workpiece. The coordinates of the points where the wheel contacts the workpiece are calculated from the force information by the computer. Therefore, the robot is able to recognize the contour of the workpiece and to grind it without teaching. Experiments using an articulated robot arm with five degrees of freedom show that the proposed robot system is applicable to t...

PROGRESS--A graphical robot programming system

Abstract: A graphical off-line robot programming system should not only be able to simulate various types of robot movement graphically, it should also be able to use graphics to interact with binary sensors, actuators and etc., in order to simulate logic-related and other functions of robot languages, such as testing and branching, looping, communication and external event handling graphically. We present a graphical off-line robot programming system which has some of these additional features. In particular, it incorporates a geometrical representation of logical conditions into the geometrical representation of the robot and workspace and it allows conditional statements to be programmed in a geometric setting.

Articulated body mobile robot

Abstract: 多関節構造からなる新しい移動ロボットの提案を行う.提案する形態は車や無限軌道車, 脚方式と並んで移動ロボットを構成する基本形態の一つであり, 特に移動ロボットが狭い空間を多量の物資を積載して移動しなければならない場合に有効である.実際に全6節, 16自由度, 全長1, 391mm, 全重量27.8kgの機械モデルKR-Iを試作し, その駆動制御実験により提案する移動ロボットがある程度の高速移動性と対地適応性を有することを示す.

Various Approaches for the Modeling of Flexible Robot Arms

Abstract: Increasing demands on velocity and accuracy of robot motions require the consideration of the elasticity of robot arms in the control and structural design. The first and most essential step is the mathematical modeling. The transmission flexibility and the torquer dynamics can easily be modeled by proven rigid body formalisms. The structural elasticity of robot arms, however, has to be regarded with more detail.

Controller for articulated robot

Abstract: PURPOSE: To surely eliminate the vibrations of a robot arm by calculating the interference torque value and at the same time estimating the disturbance torque value by an observer to use these torque values as the correction terms of each joint so that the feedback compensation is given to the disturbance torque value that produces the arm vibrations. CONSTITUTION: An arithmetic means 5 is used for calculation of the mutual interference torque value of each arm together with a state observation means 2 which regenerates a state variable from the torque command of each servomotor 7 and its real speed. Furthermore a conversion means 8 is added to convert the output of the means 2 into the correction value for the torque produced by the disturbance given to the motor 7 together with a correction means 6 which corrects the deviation signal of the torque command for the motor 7 based on said converted correction value and interference torque value. As a result, the interference torque value that produces the vibrations of the robot arms can be calculated at a high speed for each axis. Thus the arm vibrations are surely eliminated. COPYRIGHT: (C)1988,JPO&Japio

Real-time path planning for robot arms

Abstract: This thesis presents two new methods for the automatic programming of robots, which were developed at the University of Durham. A model of the robot and its surroundings is held in the computer memory in a form which can be accessed quickly by the path generation algorithm. Information is fed to the computer which defines a task for the robot to perform. The path generation algorithm then calculates the coordinates for the movement of the robot, avoiding obstacles. Finally, the information is down-loaded into the robot control computer in its own language. An important feature of the method is the high speed of calculation and data transfer, which is designed for real-time operation. The world model is represented as a collection of spheres, some overlapping, and the robot is represented by connected cylinders. This simplified representation is the key to the speed of calculation of the path. Different criteria are used for the optimal path selection, such as minimisation of the overall time taken, the distance travelled and the joint rotation. Two path planning methods have been developed. The first incorporates a local method of trajectory calculation and the second uses a global method. Both methods are suitable for real-time applications, but they have different properties which can be exploited in different applications. The relative merits of the two methods are discussed. These methods provide an on-line, real-time capability for collision free path calculation in a flexible manufacturing environment.

Voice command control system for robot

Abstract: PURPOSE:To stop a robot quickly by adding a sound pressure level measurer which outputs a stop signal, which stops the robot, through a controller if a voice input is higher than a set level and stopping the robot with this stop signal. CONSTITUTION:An operator 6 inputs a voice command to a voice recognizing device 2 through a voice input device 1 and the voice recognizing device 2 inputs the recognition result to a target value operator 3. The target value operator 3 calculates a target value for a desired operation of the robot based on this input and causes an articulated robot arm 5 to perform the desired operation through a controller 4. The voice inputted to the voice input device 1 is sent to a sound level measurer 10 simultaneously, and the sound level measurer 10 outputs the stop signal when the level of the inputted voice exceeds a set value. The stop signal outputted from the sound level measurer 10 is inputted to the target value operator 3, and the target value operator 3 calculates the target value for stop of the arm 5, and the arm 5 is stopped through the controller 4.

Coordination of multiple robot arms

Abstract: Kinematic resolved-rate control from one robot arm is extended to the coordinated control of multiple robot arms in the movement of an object. The structure supports the general movement of one axis system (moving reference frame) with respect to another axis system (control reference frame) by one or more robot arms. The grippers of the robot arms do not have to be parallel or at any pre-disposed positions on the object. For multiarm control, the operator chooses the same moving and control reference frames for each of the robot arms. Consequently, each arm then moves as though it were carrying out the commanded motions by itself.

Controlling a Robot with Sonic and Ultrasonic Means

Abstract: A robot controlled by connected speech commands uses an ultrasonic range finder to learn about objects in its workspace. Speech synthesis allows the robot to carry on conversations with the user. The robot learns the location, size, shape, and color of objects in the workspace using the range finder and asking questions of the user. The robot is then able to navigate in its environment, manipulating objects and avoiding obstacles, commanded with natural language sentences such as "Move the large red cylinder to the left of the small green block." A lisp machine database maintains the robot's knowledge of its world.

Dynamical modelling of coordinated multiple robot systems

Abstract: The state of the art in the modeling of the dynamics of coordinated multiple robot manipulators is summarized and various problems related to this subject are discussed. It is recognized that dynamics modeling is a component used in the design of controllers for multiple cooperating robots. As such, the discussion addresses some problems related to the control of multiple robots. The techniques used to date in the modeling of closed kinematic chains are summarized. Various efforts made to date for the control of coordinated multiple manipulators is summarized.

Control strategy for a dual-arm maneuverable space robot

Abstract: A simple strategy for the attitude control and arm coordination of a maneuverable space robot with dual arms is proposed. The basic task for the robot consists of the placement of marked rigid solid objects with specified pairs of gripping points and a specified direction of approach for gripping. The strategy consists of three phases each of which involves only elementary rotational and translational collision-free maneuvers of the robot body. Control laws for these elementary maneuvers are derived by using a body-referenced dynamic model of the dual-arm robot.

Teaching data generating device

Abstract: PURPOSE:To generate efficiently desired teaching data by moving a robot model displayed on a display means in accordance with each extent of displacement outputted from a simulating robot arm. CONSTITUTION:A teaching data generating device consists of a computer equipped with a work environment model generating means 1 which generates a work environment model as data on a basis of shape dimensions obtained from a design drawing by the operation of a keyboard or the like a display means 3 on which said model is displayed, simulating robot hand 4, a robot model generating means 2, an attitude data generating means 5, a joint angle generating means 6, and a teaching data storage means 7. An operator operates the hand 4 until confirming that a articulated robot model displayed on the display device 3 is placed in the work environment model in a desired attitude, and the oiler angle of a parameter which prescribes the attitude of the articulated robot model is set.

A control scheme for two cooperating robot arms

Abstract: The results of an experiment for controlling two robot arms in a cooperative manner are presented. The purpose is to move an object by grasping it at two different points using two separate robot arms. Once a path of the object is determined, the differential increments of the Cartesian trajectories of the two robot hands are obtained from the differential increments of the object. Then, the corresponding differential changes of the joint variables of the two robot arms are calculated and are used to control the movement of each robot joint.

The use of computer graphic simulation in the development of on-orbit tele-robotic systems

Abstract: This paper describes the use of computer graphic simulation techniques to resolve critical design and operational issues for robotic systems used for on-orbit operations. These issues are robot motion control, robot path-planning/verification, and robot dynamics. The major design issues in developing effective telerobotic systems are discussed, and the use of ROBOSIM, a NASA-developed computer graphic simulation tool, to address these issues is presented. Simulation plans for the Space Station and the Orbital Maneuvering Vehicle are presented and discussed.