Showing papers in "The International Journal of Robotics Research in 1985"
TL;DR: In this article, a measure of manipulability of robotic mechanisms in positioning and orienting end-effectors has been proposed and the best postures of various types of manipulators are given, and a four degree-of-freedom finger is considered from the viewpoint of the measure.
Abstract: This paper discusses the manipulating ability of robotic mechanisms in positioning and orienting end-effectors and proposes a measure of manipulability. Some properties of this measure are obtained, the best postures of various types of manipulators are given, and a four-degree-of-freedom finger is considered from the viewpoint of the measure. The pos tures somewhat resemble those of human arms and fingers.
2,321 citations
TL;DR: In this paper, the minimum-time manipulator control problem is solved for the case when the path is specified and the actuator torque limitations are known, and the optimal open-loop torques are found, and a method is given for implementing these torques with a conventional linear feedback control system.
Abstract: The minimum-time manipulator control problem is solved for the case when the path is specified and the actuator torque limitations are known. The optimal open-loop torques are found, and a method is given for implementing these torques with a conventional linear feedback control system. The algorithm allows bounds on the torques that may be arbitrary functions of the joint angles and angular velocities. This method is valid for any path and orientation of the end- effector that is specified. The algorithm can be used for any manipulator that has rigid links, known dynamic equations of motion, and joint angles that can be determined at a given position on the path.
1,321 citations
TL;DR: In this paper, the joint angle rates for a manipulator under the constraints of multiple goals, the primary goal described by the specified end-effector trajectory and secondary goals describ ing the obstacle avoidance criteria.
Abstract: The vast majority of work to date concerned with obstacle avoidance for manipulators has dealt with task descriptions in the form ofpick-and-place movements. The added flexibil ity in motion control for manipulators possessing redundant degrees offreedom permits the consideration of obstacle avoidance in the context of a specified end-effector trajectory as the task description. Such a task definition is a more accurate model for such tasks as spray painting or arc weld ing. The approach presented here is to determine the re quired joint angle rates for the manipulator under the con straints of multiple goals, the primary goal described by the specified end-effector trajectory and secondary goals describ ing the obstacle avoidance criteria. The decomposition of the solution into a particular and a homogeneous component effectively illustrates the priority of the multiple goals that is exact end-effector control with redundant degrees of freedom maximizing the distance to obstacles. An efficient numerical ...
1,027 citations
TL;DR: The methodology is compared with standard algorithms such as the computed torque method and is shown to combine in practice improved performance with simpler and more tractable controller designs.
Abstract: A new scheme is presented for the accurate tracking control of robot manipulators. Based on the more general suction control methodology, the scheme addresses the following problem: Given the extent of parametric uncertainty (such as imprecisions or inertias, geometry, loads) and the frequency range of unmodeled dynamics (such as unmodeled structural modes, neglected time delays), design a nonlinear feedback controller to achieve optimal tracking performance, in a suitable sense. The methodology is compared with standard algorithms such as the computed torque method and is shown to combine in practice improved performance with simpler and more tractable controller designs.
689 citations
TL;DR: An approach is suggested by which the kine matic variables may be extracted from evolving contours in an image sequence by extracting the instantaneous motion and local structure of the object along the line of sight from an evolving image sequence.
Abstract: This study concerns a new formulation and method of solu tion of the image flow problem. It is relevant to the maneu vering of a robotic system through an environment containing other moving objects or terrain. The two-dimensional image flow is generated by the relative rigid-body motion of a smooth, textured object along the line of sight to a monocular camera. By analyzing this evolving image sequence, we hope to extract the instantaneous motion (described by six degrees of freedom) and local structure (slopes and curvatures) of the object along the line of sight. The formulation relates a new local representation of an image flow to object motion and structure by twelve nonlinear algebraic equations. The repre sentation parameters are given by the two components of image velocity, three components of rate of strain, spin, and six independent image gradients of rate of strain and spin, evaluated at the point on the line of sight. These kinematic variables are motivated by the deformation of a finite ele...
208 citations
TL;DR: In this article, the deformation parameters are linear combinations of the Taylor series coefficients (through second derivatives) of the local image flow field, and a byproduct of their approach is a second-order polyno marginal approximation to the image flow in the neighborhood of a contour.
Abstract: In the kinematic analysis of time-varying imagery, where the goal is to recover object surface structure and space motion from image flow, an appropriate representation for the flow field consists of a set of deformation parameters that describe the rate of change of an image neighborhood. In this paper we develop methods for extracting these deformation param eters from evolving contours in an image sequence, the image contours being manifestations of surface texture seen in perspective projection. Our results follow directly from the analytic structure of the underlying image flow; no heuristics are imposed. The deformation parameters we seek are actu ally linear combinations of the Taylor series coefficients (through second derivatives) of the local image flow field. Thus, a by-product of our approach is a second-order polyno mial approximation to the image flow in the neighborhood of a contour. For curved surfaces this approximation is only locally valid, but for planar surfaces it is globally valid (...
163 citations
TL;DR: In this paper, the inverse kinematic problem with manipulators of arbitrary architecture is solved with invariants in the rotational part of the closure equations, which produces a formally overdetermined nonlinear algebraic system.
Abstract: Solved in this paper is the inverse kinematic problem asso ciated with manipulators of arbitrary architecture. Its formu lation is based on invariants in the rotational part of the closure equations, which produces a formally overdetermined nonlinear algebraic system. In the translational part, a recur sive scheme similar to that of Horner's for polynomial evalu ation is introduced. This leads to a reduced number of com putations, which allows an efficient numerical solution of the problem. Velocity and acceleration kinematic inversions are also included. The procedure is illustrated with the analysis of a six-degree-of-freedom, revolute-coupled manipulator of an architecture that makes a closed-form solution difficult. This method has been successfully applied to the analysis of 7R spatial linkages as well. Appendix A lists the nomenclature and notation used in this paper.
138 citations
TL;DR: This paper addresses the problem of efficiently computing the motor torques required to drive a manipulator arm in free motion, given the desired trajectory—that is the inverse dynamics problem and presents two "mathemati cally exact "formulations especially suited to high-speed, highly parallel implementations using VLSI devices.
Abstract: This paper addresses the problem of efficiently computing the motor torques required to drive a manipulator arm in free motion, given the desired trajectory—that is the inverse dynamics problem. It analyzes the high degree of parallelism inherent in the computations and presents two "mathemati cally exact "formulations especially suited to high-speed, highly parallel implementations using VLSI devices. The first method presented is a parallel version of the recent linear Newton-Euler recursive algorithm. The time cost is linear in the number of joints, but the real-time coefficients are re duced by almost two orders of magnitude. The second formu lation reports a new parallel algorithm that shows that it is possible to improve on the linear time dependency. The real time required to perform the calculations increases only as the [log2] of the number of joints. Either formulation is sus ceptible to a systolic pipelined architecture in which complete sets of joint torques emerge at successive intervals of f...
136 citations
TL;DR: In this paper, the finger is modeled as an infinite linear elastic half-plane to predict the measured strain for several contact types and forces, and the number of sensors required is less than has been proposed for other tactile recognition tasks.
Abstract: In order for a robot hand to grasp objects stably without using object models, tactile feedback from the fingers is sometimes necessary. This feedback can be used to adjust grasping forces to prevent a part from slipping from a hand. If the angle of force at the object-finger contact can be deter mined, slip can be prevented by the proper adjustment of finger forces. Another important tactile sensing task is finding the edges and corners of an object since they are usually feasible grasping locations.This paper describes how this information can be extracted from the finger-object contact using strain sensors beneath a compliant skin. For determining contact forces, strain mea surements are easier to use than the surface deformation profile. The finger is modeled as an infinite linear elastic half-plane to predict the measured strain for several contact types and forces. The number of sensors required is less than has been proposed for other tactile recognition tasks.A rough upper bound on sensor density ...
130 citations
TL;DR: In this paper, the authors discuss the grasping and manipulation of objects by an articulated robot hand, and the necessary conditions for the grasping ability of a robot hand are determined. But they do not consider the manipulation of the objects.
Abstract: This paper discusses the grasping and manipulation of ob jects by an articulated robot hand. Necessary conditions for the grasping and manipulating abilities of a robot hand are determined, and way...
98 citations
TL;DR: Using conventional robots for metal/inert-gas (MIG) arc welding on thin (1-to 2-mm) sheet steel pressings is restricted by the difficulty of maintaining accurate fit-up and fixturing as discussed by the authors.
Abstract: Using conventional robots for metal/inert-gas (MIG) arc welding on thin (1- to 2-mm) sheet steel pressings is restricted by the difficulty of maintaining accurate fit-up and fixturing. Dimensional ...
TL;DR: A mobile robot is required to navigate around barriers in an unexplored environment and some heuristic strategies to aid such navigation are discussed, showing their usefulness in obstacle avoidance.
Abstract: A mobile robot is required to navigate around barriers in an unexplored environment. Some heuristic strategies to aid such navigation are discussed here. Being heuristic, these methods can be neither exhaustively tested nor proved effec tive in all cases. However, examples are given to demonstrate their usefulness in obstacle avoidance. In a simple case of sufficient generality, the heuristics are shown to be effective.
TL;DR: In this paper, a look-ahead of a few points on the trajectory is used to generate a Cartesian trajectory of the end-effector trajectory of a robot, which is then executed on the target object.
Abstract: Robot motion is commonly specified as a Cartesian trajectory of its end-effector. For executing the end-effector trajectory on-line, a look-ahead of a few points on the trajectory is used to genera...
TL;DR: The feasibility of tracking a seam in real time is demonstrated and a general-purpose seam tracing algo rithm is developed for implementation on a robot with six de grees of freedom.
Abstract: : Seam tracking is currently accomplished by special features of the robot and a priori knowledge of seam geometry. This paper demonstrates the feasibility of tracking a seam in real-time. A general-purpose seam tracking algorithm is developed for implementation on a robot with six degrees-of-freedom. The algorithm is motivated by a physical interpretation of the t sub 6 and dt sub 6 matrices, and the assumption that three dimensional seam data are available. In the past, dT sub s matrix and inverse Jacobian solutions have been used to compute the differential changes in the joint angles. By using the inverse Jacobian , an iterative algorithm is introduced to compute both large and small changes in the joint variables. The versatile seam tracking algorithm can be applied to a multitude of robotic seam tracking activities such as gluing, surface grinding and flame cutting. (Author)
TL;DR: The robust servomechanism theory is applied to the linear system that results when the overall, nonlinear, dynamic system is split, in the standard manner, into a nominal system and a (linear) system linearized about the nominal as discussed by the authors.
Abstract: This paper describes a framework for synthesizing control laws for manipulators based on robust servomechanism theory for multivariable linear systems. This framework takes into account the coupled and nonlinear nature of the differen tial equations describing the manipulator as well as the fact that the inputs and outputs are subject to large excursions.The robust servomechanism theory is applied to the linear system that results when the overall, nonlinear, dynamic system is split, in the standard manner, into a nominal sys tem and a (linear) system linearized about the nominal. A control law for the linear system is then derived on the basis of linear quadratic regulator theory. To ensure good dynamic response, the implicit model-following technique is used to choose the weights in the resulting performance index.The theory is then applied to design a control law for a two-degree-of-freedom spatial manipulator following a pre scribed trajectory. The effect of changing the speed and iner tias of the man...
TL;DR: In this article, a joint torque sensor system is designed for a robot manipulator to provide compliance control of a high gain, wideband width torque servo system based on a torque sensor and verified by a single joint manipulator.
Abstract: The application of a robot manipulator to the task of assem bling manufacturing products requires compliance control, which means the control and monitoring of both forces and positions of the robot. To increase the operation speed of compliance control, a fast, reliable force servo system based on a proper sensing technique is imperatively needed. In this paper, current existing force-sensing techniques are analyzed, and the results suggest that a joint torque-sensing technique will give the best performance in a force servo system. A prototype joint torque sensor system is designed for our ex periment. As a result, a new, simple, high-gain, wide-band width torque servo system based on a joint torque sensor system is developed and the system's performance is verified by a single joint manipulator. To provide compliance, a method of selecting the force servo joints for a robot is also provided.
TL;DR: In this paper, a tactile sensor array de signed to provide sensory feedback for a robot manipulator system is described, which enables humans to distinguish between different materials based on how "cold" or "warm" they feel.
Abstract: This paper describes a new type of tactile sensor array de signed to provide sensory feedback for a robot manipulator system. It is modeled on the thermal touch sense, which enables humans to distinguish between different materials based on how "cold" or "warm" they feel. The essential parts of the sensor are a heat source and a thin layer of sili cone rubber with a 2 X 10 array of miniature thermistors embedded in its surface. Some results are presented that demonstrate the ability of thermal sensors to produce images of touched objects and to discriminate the different materials used in their construction.
TL;DR: In this paper, a technique has been developed for the precise adjustment of gear backlash of the joints of an industrial robot, which can be used for both the adjustment of the joint gears and the periodic automatic inspection of their condition.
Abstract: A technique has been developed for the precise adjustment of gear backlash of the joints of an industrial robot Bandli mited random excitation signals were injected into the drive system of the joint under test, and the output response of the joint link was monitored using an accelerometer The coher ence function was measured and used to adjust the joint gear backlash to minimize the effect of the backlash nonlinearity on the joint drive system Tests were performed while the joint was both loaded and unloaded and for several different steady-state positions The test results indicate that this technique can be used for both the adjustment of the joint gears and the periodic automatic inspection of their condition
TL;DR: In this article, a non-degenerate kinematic solution is proposed for a kinematically simple seven-jointed robot manipulator with six independent degrees of freedom, which guarantees that the manipulator is capable of positioning and orienting its end-effector within the workspace without ever finding itself in a degenerate configuration.
Abstract: Kinematically simple manipulators with six joints have unavoidable degenerate configurations that correspond to certain positions or orientations of the end-effector within the workspace In these degenerate configurations, the end-effec tor of the manipulator is not capable of a motion with six independent degrees of freedom Such a manipulator reduces the flexibility of a manufacturing system because manufac turing processes need to be planned so that positions or ori entations of the end-effector that correspond to degenerate configurations of the manipulator are not requiredIn this paper a nondegenerate kinematic solution is devel oped for a kinematically simple seven-jointed robot manipu lator The solution guarantees that the manipulator is capa ble of positioning and orienting its end-effector within the workspace without ever finding itself in a degenerate configu ration The nondegenerate kinematic solution is in closed form and is developed from well-known methods and results in three-dimension
IBM1
TL;DR: This paper develops a high-level control system (CS) language that allows one to specify compliant control tasks as vector equa tions and inequalities that relate sensed and controlled vari ables such as f · v = 0 and f X v =0 .
Abstract: Current robot control techniques are primarily concerned with position control and, recently, with force control, where a motion planner is used primarily to compute set point changes. The actual control system is fixed and internal and cannot be modified easily through software. Current robot languages are also limited in their ability to specify changes to the control structure. For compliant motion, such as as sembly, more flexibility is needed in the control system, that is, an ability to tailor the controller to the task. This paper develops a high-level control system (CS) language that allows one to specify compliant control tasks as vector equa tions and inequalities that relate sensed and controlled vari ables such asf·v = 0 andfXv=0 . We show how such requirements can be reformulated as an objective function of an optimization process subject to constraints arising from the dynamic equations involved. Specifically for the two examples above, we show how such requirements can be re formulated as ...
Journal Article•
TL;DR: In this article, a digital controller for a three-degree-of-freedom mechanical manipulator is developed, which uses linear quadratic optimal control theory to design the controller with integral and preview I actions.
Abstract: i The design of a digital controller for a three-degree-of freedom mechanical manipulator is developed. After linearizing and decoupling the manipulator dynamics by using the estimate of inertia matrix, the linear quadratic optimal control theory is applied to design the controller with integral and preview I actions. The preview action utilizes the future reference trajectory known in advance to make the manipulator joints follow the reference inputs with small tracking errors and lower peak torque 1 inputs during the transient. The performance of the manipulator with the proposed controller is examined by I computer simulation.