Showing papers on "Robot kinematics published in 1989"

Robot dynamics and control

Abstract: From the Publisher: This self-contained introduction to practical robot kinematics and dynamics includes a comprehensive treatment of robot control. Provides background material on terminology and linear transformations, followed by coverage of kinematics and inverse kinematics, dynamics, manipulator control, robust control, force control, use of feedback in nonlinear systems, and adaptive control. Each topic is supported by examples of specific applications. Derivations and proofs are included in many cases. Includes many worked examples, examples illustrating all aspects of the theory, and problems.

Calibration of wrist-mounted robotic sensors by solving homogeneous transform equations of the form AX=XB

Abstract: To use a wrist-mounted sensor (such as a camera) for a robot task, the position and orientation of the sensor with respect to the robot wrist frame must be known. The sensor mounting position can be found by moving the robot and observing the resulting motion of the sensor. This yields a homogeneous transform equation of the form AX=XB, where A is the change in the robot wrist position, B is the resulting sensor displacement, and X is the sensor position relative to the robot wrist. The solution to an equation of this form has one degree of rotational freedom and one degree of translation freedom if the angle of rotation of A is neither 0 nor pi radians. To solve for X uniquely, it is necessary to make two arm movements and form a system of two equations of the form: A/sub 1/X=XB/sub 1/ and A/sub 2/X=XB/sub 2/. A closed-form solution to this system of equations is developed and the necessary conditions for uniqueness are stated. >

World modeling and position estimation for a mobile robot using ultrasonic ranging

Abstract: The author describes a system for dynamically maintaining a description of the limits to free space for a mobile robot using a belt of ultrasonic range sensors. A model is presented for the uncertainty inherent in such sensors, and the projection of range measurements into external Cartesian coordinates is described. Line segments are then expressed by a set of parameters represented by an estimate and a precision. A process is presented for extracting line segments from adjacent collinear range measurements, and a fast algorithm is presented for matching these line segments to a model of the limits to free space of the robot. A side effect of matching observations to a local model is a correction to the estimated position of the robot at the time that the observation was made. A Kalman filter update equation is developed to permit the correspondence of a line segment to the model to be applied as a correction to estimated position. Examples of segment extraction, position correction and modeling are presented using real ultrasonic data. >

Direct kinematic solution of a Stewart platform

Abstract: The Stewart platform is a fully parallel, six-degree-of-freedom manipulator mechanism. Although its inverse kinematics have been extensively studied, no solutions to the direct position kinematics problem have been previously presented in the literature. A solution of the direct kinematics problem of the case in which the six limbs form three concurrent pairs at either the base or the hand member is presented. Even though it is not the most general possible configuration, this case does include many arrangements that have been used in practical robot mechanisms. >

Global path planning using artificial potential fields

Abstract: The author describes a path planning technique for robotic manipulators and mobile robots in the presence of stationary obstacles. The planning consists of applying potential fields around configuration-space obstacles and using these fields to select a safe path for the robot to follow. The advantage of using potential fields in path planning is that they offer a relatively fast and effective way to solve for safe paths around obstacles. In the proposed method of path planning, a trial path is chosen and then modified under the influence of the potential field until an appropriate path is found. By considering the entire path, the problem of being trapped in a local minimum is greatly reduced, allowing the method to be used for global planning. The algorithm was tried with success on many different realistic planning problems. By way of illustration, the algorithm is applied to a two-dimensional revolute manipulator, a mobile robot capable of translation only, and a mobile robot capable of both translation and rotation. >

Real-time application of neural networks for sensor-based control of robots with vision

Abstract: A practical neural network-based learning control system is described that is applicable to complex robotic systems involving multiple feedback sensors and multiple command variables. In the controller, one network is used to learn to reproduce the nonlinear relationship between the sensor outputs and the system command variables over particular regions of the system state space. The learned information is used to predict the command signals required to produce desired changes in the sensor outputs. A second network is used to learn to reproduce the nonlinear relationship between the system command variables and the changes in the video sensor outputs. The learned information from this network is then used to predict the next set of video parameters, effectively compensating for the image processing delays. The results of learning experiments using a General Electric P-5 manipulator are presented. These experiments involved control of the position and orientation of an object in the field of view of a video camera mounted on the end of the robot arm, using moving objects with arbitrary orientation relative to the robot. No a priori knowledge of the robot kinematics or of the object speed of orientation relative to the robot was assumed. Image parameter uncertainty and control system tracking error in the video image were found to converge to low values within a few trials. >

Deadlock-free and collision-free coordination of two robot manipulators

Abstract: The authors describe a method for coordinating the trajectories of two robot manipulators so as to avoid collisions between them. It is assumed that the robots' environment is known and that the robots' paths can thus be planned in advance but that there may be significant variations in the execution time of some of the path segments. The goal is to allow the motions of each manipulator to be planned nearly independently and to allow the execution of the path segments to be asynchronous. The coordination is achieved by introducing explicit coordination commands into the path. The key problems in coordinating trajectories are to avoid collisions between the two robots and to avoid deadlock, that is, situations where each manipulator is waiting for the other to proceed. >

Adaptive control of flexible joint manipulators

Abstract: The authors present an adaptive control result for flexible-joint robot manipulators. Under the assumption of weak joint elasticity, a singular perturbation argument is used to show that recent adaptive control results for rigid robots can be used to control flexible-joint robots, provided a simple correction term is added to the control law to damp out the elastic oscillations at the joints. In this way, fundamental properties of rigid robot dynamics can be used to design robust adaptive control laws for flexible-joint robots. The implementation of the full controller requires only joint position and velocity information. Thus, robustness to parametric uncertainty is achieved without the need for acceleration and jerk measurements. >

Task-level planning of pick-and-place robot motions

Abstract: A task-level robot system named Handey, which is under development, is described. The current system is limited to pick-and-place operations, and it has successfully carried out dozens of such operations involving a variety of parts in relatively complex environments. The pick-and-place problem is described, and approximate approaches to the problem are examined. Heuristic motion planning in Handey is then discussed. >

Inverse kinematics of redundant robots using genetic algorithms

Abstract: Genetic algorithms, which are robust general-purpose optimization techniques, have been used to solve the inverse kinematics problem for redundant robots. A genetic algorithm (GA) was used to position a robot at a target location while minimizing the largest joint displacement from the initial position. As currently implemented, GAs are suitable for offline programming of a redundant robot in point-to-point positioning tasks. The GA solution needs only the forward kinematic equations (which are easily developed) and does not require any artificial constraints on the joint angles. The joint rotation limits which are present in any feasible robot design are handled directly; so any solution determined by the GA is physically realizable. Finally, the GA works with joint angles represented as digital values (not continuous real numbers), which is more representative for computer-controlled robot systems. >

The robotics review 1

Abstract: Part 1 Programming, planning, and learning: articles - motion planning in the presence of moving obstacles, Jean-Claude Latombe, minimal length curves and optimal paths, Jean-Daniel Boissonat, task level robot programming - on the HANDEY system, Jocelyne Pertin-Troccaz reviews - robot motion planning, Jean-Claude Latombe, John Canny, planar sliding with dry friction, Suresh Goyal, et al. Part 2 Sensing and perception: articles - touch sensing for robotic manipulation and recognition, Robert D. Howe and Mark R. Cutkosky, sensor planning for robotic vision - a review, Konstantinos (Dino) Tarabanis and Rober Y. Tsai, solving for 3-D model parameters from the locations of image features, David Lowe, modeling sonar sensors, Hugh F. Durrant-Whyte and John J. Leonard reviews - authenticating edges produced by zero-crossing algorithms, James J. Clark and Harlyn Baker a few steps toward artificial 3-D vision, Olivier D. Faugeras, W. Eric L. Grimson. Part 3 Kinematics and dynamics: articles - wrist singularities - theory and practice, Charles Wampler reviews - kinematic analysis and design of redundant manipulators, Joel W. Burdick and Vincent Hayward, singular configurations of parallel manipulators and Grassman geometry, Jean-Pierre Merlet and Jorge Angeles, a spatial operator algebra for manipulator modeling and control, G. Rodriquez, et al on the inverse kinematics of redundant manipulators, Daniel R. Baker, et al duality in mechanical properties of sequential and parallel manipulators, Vladimir Zamanov, et al. Part 4 Motion and force control: articles - time-optimal motions of robot manipulators including dynamics, Marc Renaud and J. Yves Fourquet, the state of the art of robot learning control using artificial neural networks - an overview, V.D. Sanchez A. and G. Hirzinger reviews - the application of model-referenced adaptive control to robotic manipulators, S. Dubowsky, et al is adaptive control necessary for manipulation robots, and if so, to what extent?, D. Stokic, et al. Part 5 Design, technology, and applications: articles - a comparative analysis of actuator technologies for robotics, John M. Hollerback, et al, microrobotics - shifting robotics technology toward a different scale world, Paolo Dario and Renzo Valleggi reviews - robotics in service, Joseph F. Engelberger and Russell H. Taylor.

Coordinated motion control of robot arms based on the virtual internal model

Abstract: The authors propose an alternative coordinated motion control architecture for robot arms manipulating an object. The motion and the internal force of the object are resolved into the motion of each arm. Each arm is controlled, on the basis of the virtual internal model, so that they operate in coordination even if geometric errors exist in the arms and the object. The virtual internal model is a reference model driven by sensory information implemented in the controller. The proposed architecture maintains the stability of the system even if breakage of the manipulated object occurs. The control algorithm was experimentally applied to the coordinated motion control of two planar robot arms, each of which has three degrees of freedom. The results illustrate the validity of the proposed control architecture. >

Blanche: Position Estimation For An Autonomous Robot Vehicle

Abstract: This paper describes the position estimation system for an autonomous robot vehicle called Blanche, which is designed for use in structured office or factory environments. Blanche is intended to be low cost, depending on only two sensors, an optical rangefinder and odometry. Briefly, the position estimation system consists of odometry supplemented with a fast, robust matching algorithm which determines the congruence between the range data and a 2D map of its environment. This is used to correct any errors existing in the odometry estimate. The integration of odometry with fast, robust matching allows for accurate estimates of the robot’s position and accurate estimates of the robot’s position allow for fast, robust matching. That is, the system is self sustaining.

An adaptive approach to motion and force control of multiple coordinated robot arms

Abstract: An approach to motion and force control of multiple coordinated robot arms based on an adaptive scheme is developed. The adaptation law uses Popov hyperstability theory to estimate online the uncertain parameters of multiple robot arms and payload. The approach can be used to control the motion of an object held by the arms, the contact forces between the object and the environment, and the internal forces that do not contribute to the motion and the contact forces. Three subsystem error equations are generated, i.e. a position error subsystem, a contact force error subsystem, and an internal force error subsystem. The unknown parameters of the multiple coordinated robot arms and the object are estimated in terms of the three error subsystem equations. It is shown that the proposed adaptive control scheme improves the position and internal and contact force tracking accuracy of a class of systems with an uncertain knowledge of the dynamic model. >

On the Robot Compliant Motion Control

Abstract: The work presented here is a nonlinear approach for the control and stability analysis of manipulative systems in compliant maneuvers. The general stability condition has been extended to the particular case where the environment is very rigid in comparison with the robot stiffness. A fast, light-weight, active end-effector (a miniature robot) which can be attached to the end-point of large commercial robots has been designed and built to verify the control method

Dynamic modeling of closed-chain robotic manipulators and implications for trajectory control

Abstract: A simple, physically insightful method for dynamic modeling of manipulators containing closed kinematic chains is presented. Founded on D'Alembert's principle, the method centers around a transformation from the well-understood dynamics of serial and open-chain mechanisms to closed-chain dynamic robot models. The framework for the closed-chain dynamic robot model fosters straightforward extensions of serial robot engineering activities in the areas of digital simulation, real-time control, parameter identification, and optimal path planning to closed-chain manipulators. The algorithms needed to realize these extensions are detailed, and the important concepts are highlighted with an example. >

Coupled drive of the multi-DOF robot

Abstract: A robot system design to minimize the robot weight while producing multi-degree-of-freedom (DOF) functioning is proposed. This method aims to couple mutually the degrees of freedom of the robot in such a way that, so far as possible, they can be jointly driven in the robots most common modes of operation. The method is called coupled drive. As an evaluation function for the coupled drive, an actuation index, which is the ratio of the power for the actuation to the whole output power to be provided to the robot system, is introduced. A simulation experiment involving a quadruped walking robot with suckers ascending the vertical surface of a wall is carried out. The experiment deduces by linear programming a walk by which the actuation ratio of the robot is maximized when specific configurations or gaits of the walking robot are given. >

Motion and force control for multiple cooperative manipulators

Abstract: The authors address the problem of motion and force control of multiple robot arms manipulating an object. A general control paradigm that decouples the motion and force control problems is introduced. For motion control, different control strategies are constructed on the basis of control input variables. There are three natural choices: joint torques, arm tip force vectors, and the acceleration of a generalized coordinate. The first choice allows relatively model-independent control by exploiting the Hamiltonian structure of the open-loop system. The latter two require the full model information but produce simpler control design problems. The motion control determines the joint torque only to within a manifold, owing to the multiple-arm kinematic constraint. To resolve the nonuniqueness of the joint torques, two methods are introduced. If the arm and object models are available, the allocation of the desired end-effector control force to the joint actuators can be optimized. The other possibility is to control the internal force about some set point. Effective force regulation can be achieved with little model information. >

Applications of the passive systems approach to the stability analysis of adaptive controllers for robot manipulators

Abstract: Utilizing the fact that a manipulator composed of rigid links is a passive system, an approach based on the properties of interconnected passive systems is proposed for the analysis and synthesis of fixed and adaptive controllers for robot manipulators. This approach clarifies the rationale behind the various fixed and adaptive control laws synthesized using Lyapunov functions and provides new adaptation algorithms.

Robust Control of Robotic Manipulators

Abstract: This paper introduces a new control system design methodology that allows the use of linearly controlled manipulators in fast, more complex maneuvers. This is made possible by guaranteeing a prescribed degree of relative stability while constraining the system state variables and inputs. The closed-loop linear system is also assigned desirable eigenvectors. The robustness of the system is evaluated using a new measure of robustness. The design methodology is applied to a 2-D.O.F. robotic manipulator. Simulation results demonstrate that the final design must be a compromise between robustness, relative stability, and other considerations.

A generalized kinematic modeling method for modular robots

Abstract: Modular robots can be defined as reconfigurable mechanical arms which can be automatically controlled using suitable motion control software. In this article, a generalized kinematic modeling method is presented for such modular robots. This method can be used to derive the individual kinematic models of all the mechanical elements that make up the inventory of modular units, independently of their geometry and sequence of assembly into a robot. A general procedure is also presented to derive a global kinematic model of any robot configured using these modular units. The kinematic modeling technique of the units is based on Denavit-Hartenberg (D-H) parameter notation. A provision is also presented for converting “non D-H” parameter transformations, obtained in assembling the kinematic chain, into D-H transformations. This D-H conversion feature allows the modeling technique to preserve its generality when a kinematic model is obtained for the specific robot configuration at hand. The conceptual design of modular robot units that is under development in the Computer Integrated Manufacturing Laboratory (CIML) is also presented to show the feasibility of a modular approach to robot design and to clarify some of the mathematical for mulations developed in the article.

Design and analysis of the statically balanced direct-drive robot manipulator

Abstract: A practical architecture, using a four-bar linkage, is considered for the University of Minnesota direct-drive robot (Kazerooni, H., Kim, S.: A new architecture for direct drive robots. In Proc. IEEE International Conference on Robotics and Automation, Philadelphia, Pennsylvania, April 1988). This statically balanced direct-drive robot has been constructed for stability analysis of the robot in constrained manipulation (Kazerooni, H. et al.: Fundamentals of robust compliant motion for robot manipulators. IEEE J. Robotics Automation 2: 1986; Kazerooni, H.: On the robot compliant motion control. ASME J. Dynamic Systems Msmt Control; 111 (3): September 1989. Kazerooni, H. et al.: Theory and experiments on robot compliant motion control. ASME J. Dynamic Systems Msmt Control, June 1990). 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 5 g at the robot 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 construction of the robot links. A 4-node parallel processor has been used to control the robot. A compliant motion control method has been derived and experimentally verified to guarantee stable constrained maneuvers for the robot. As part of the research work, a general criterion has been derived to guarantee the stability of robot manipulators in constrained maneuvers.

Open-loop stiffness control of overconstrained mechanisms/robotic linkage systems

Abstract: A novel approach for the control of task-space stiffness characteristics in systems consisting of a superabundance of kinematically dependent inputs is proposed. When there are more input actuations than operational degrees of freedom, internal preloads can be generated that produce effective restoring forces in the face of displacement or disturbances imposed on the system. Examples of this excessive actuation can be found in certain modes of structurally overconstrained parallel manipulators and in antagonistically structured serial manipulators. The input loads are synthesized offline (prior to operation) and entered as a feedforward component so that the desired effective loads on objects are obtained, and (simultaneously) significant disturbances at the task level can be largely rejected in an open-loop fashion. This reduces the burden and shortcomings of standard feedback schemes. Moreover, a layered feedback scheme is used to compensate for small perturbations and unmodeled dynamics. The open-loop task-based stiffness control scheme as applied to structurally parallel mechanism/robotic linkage systems is investigated. The scheme's applicability as a programmable active compliance device is also discussed. >

The effect of kinematic model complexity on manipulator accuracy

Abstract: A pose measurement system consisting of a small coordinate measuring machine, an IBM personal computer, and several fixtures is described. The pose measurement system is used to collect two data sets of 45 poses each. These data are then used to identify the parameters in five manipulator models of increasing complexity. The models consist of a nominal model, a model with six parameters to determine the actual robot location, a 12-parameter model including robot location and joint offsets, a 30-parameter kinematic model, and a 32-parameter model including compliance in two joints. The pose measurement system is used to evaluate the accuracy of each of the five models. The results demonstrate that, in general, increases in model complexity lead to enhanced accuracy, although the degree of improvement at any level is dependent on the particular robot under study. >

Accelerated convergence in the inverse kinematics via multilayer feedforward networks

Abstract: A hybrid approach to the iterative solution of robotic manipulators is presented. In this method a multiplayer feedforward network (MFN) is trained to provide an approximate solution to the inverse kinematic problem of a robot. This approximate solution is then utilized as the initial guess to the iterative procedure which provides the solution within some specified tolerance. Examples involving the PUMA 560 robot are given. Since the time taken by the MFN to provide the initial estimate is only a fraction of the time taken by the iterative procedure taken to reach a solution, this combination can be usefully employed in order to decrease the time for obtaining the solution to the inverse kinematic problem in robotics. >

Navigation Strategies For Multiple Autonomous Mobile Robots Moving In Formation

Abstract: The problem of deriving navigation strategies for a fleet of autonomous mobile robots moving in formation is considered. Here, each robot is represented by a particle with a spherical effective spatial domain and a specified cone of visibility. The global motion of each robot in the world space is described by the equations of motion of the robot's center of mass. First, methods for formation generation are discussed. Then, simple navigation strategies for robots moving in formation are derived. A sufficient condition for the stability of a desired formation pattern for a fleet of robots each equipped with the navigation strategy based on nearest neighbor tracking is developed. The dynamic behavior of robot fleets consisting of three or more robots moving in formation in a plane is studied by means of computer simulation.

Dynamic coordinated control of two robot manipulators

Abstract: The dynamic coordinated control of two robot manipulators grasping a common object is studied. A dynamic coordinated control model for two robot manipulators which is suitable for the purpose of system control analysis is derived. The model takes into account kinematic and dynamic constraints between two manipulators and is explicitly described by nonlinear state equations and nonlinear output equations. Since coordinated control requires control of forces applied to the object by manipulators, the output equations include both position components and force components. While it is true that robotic systems with position outputs can be linearized by using a nonlinear feedback, linearization of force outputs has not been established. The differential geometric control theory on exact linearization and output decoupling of nonlinear systems is used to find a dynamic nonlinear feedback that, together with a diffeomorphic state-space transformation, linearizes and simultaneously output-decouples the nonlinear model of two robot manipulators. Dynamic coordinated control of two robot manipulators is converted into a control problem of linear systems. >

Dual-drive force/velocity control: implementation and experimental results

Abstract: The authors present the dual-drive control concept, which is a form of hybrid force/velocity control in which the constraint frame is automatically determined from feedback information. This allows compliant tasks to be conveniently specified in terms of a desired (normal) force and a desired (tangential) velocity. The proposed control algorithm is appropriate for compliant tasks that require motion orthogonal to the contact force; for example, turning a crank or tracking a surface. These basic tasks can be performed without the continuous involvement and corresponding overhead of a high-level planner. This is accomplished by the definition of a plane on which compliant motion is to occur and a point with which force and velocity directions are determined. The dual drive controller has been implemented on the SIERA system and is being used to control an IBM 7565 robot. Experimental results for crank-turning and surface-tracking problems are provided to illustrate the algorithm. >

A modular architecture for inverse robot kinematics

Abstract: A modular architecture for general-purpose inverse robot kinematics is developed. The authors synthesize kinematic modules for the robot arm and wrist and develop computational blocks to describe their respective functions. They then present an analytical framework that defines the inverse kinematic problem in terms of the proper coordination of the kinematic modules to accomplish the desired robot task. In this general-purpose framework, the inverse kinematics problem is always solvable in the feasible regions of the robot workspace, irrespective of whether the solution is analytically tractable. The modular architecture is based upon a nonlinear equation solver for which the Banach fixed-point theorem provides the theoretical basis. The proposed framework allows for the mathematical definition of the region in the robot workspace where convergence to the correct solution is guaranteed. It is insensitive to the initial estimates and provides for the computation of multiple solutions. >