Showing papers in "The International Journal of Robotics Research in 1986"
TL;DR: This paper reformulated the manipulator con trol problem as direct control of manipulator motion in operational space—the space in which the task is originally described—rather than as control of the task's corresponding joint space motion obtained only after geometric and geometric transformation.
Abstract: This paper presents a unique real-time obstacle avoidance approach for manipulators and mobile robots based on the artificial potential field concept. Collision avoidance, tradi tionally considered a high level planning problem, can be effectively distributed between different levels of control, al lowing real-time robot operations in a complex environment. This method has been extended to moving obstacles by using a time-varying artificial patential field. We have applied this obstacle avoidance scheme to robot arm mechanisms and have used a new approach to the general problem of real-time manipulator control. We reformulated the manipulator con trol problem as direct control of manipulator motion in oper ational space—the space in which the task is originally described—rather than as control of the task's corresponding joint space motion obtained only after geometric and kine matic transformation. Outside the obstacles' regions of influ ence, we caused the end effector to move in a straight line with an...
6,515 citations
TL;DR: In this paper, a general method for estimating the nominal relationship and expected error (covariance) between coordinate frames representing the relative locations of objects is described. But this method can be used to answer such questions as whether a camera attached to a robot is likely to have a particular reference object in its field of view.
Abstract: This paper describes a general method for estimating the nominal relationship and expected error (covariance) between coordinate frames representing the relative locations of objects. The frames may be known only indirectly through a series of spatial relationships, each with its associated error, arising from diverse causes, including positioning errors, measurement errors, or tolerances in part dimensions. This estimation method can be used to answer such questions as whether a camera attached to a robot is likely to have a particular reference object in its field of view. The calculated estimates agree well with those from an independent Monte Carlo simulation. The method makes it possible to decide in advance whether an uncertain relationship is known accurately enough for some task and, if not, how much of an improvement in locational knowledge a proposed sensor will provide. The method presented can be generalized to six degrees of freedom and provides a practical means of estimating the relationships (position and orientation) among objects, as well as estimating the uncertainty associated with the relationships.
1,419 citations
TL;DR: This work proposes the paradigm of recognizing objects while locating them as a prediction and verifi cation scheme that makes efficient use of the shape representation and the matching algorithm, which are general and can be used for other types of data, such as ultrasound, stereo, and tactile.
Abstract: The problem of recognizing and locating rigid objects in 3-D space is important for applications of robotics and naviga tion. We analyze the task requirements in terms of what information needs to be represented, how to represent it, what kind of paradigms can be used to process it, and how to implement the paradigms. We describe shape surfaces by curves and patches, which we represent by linear primitives, such as points, lines, and planes. Next we describe algo rithms to construct this representation from range data. We then propose the paradigm of recognizing objects while locat ing them. We analyze the basic constraint of rigidity that can be exploited, which we implement as a prediction and verifi cation scheme that makes efficient use of the representation. Results are presented for data obtained from a laser range finder, but both the shape representation and the matching algorithm are general and can be used for other types of data, such as ultrasound, stereo, and tactile.
899 citations
TL;DR: This paper discusses three fundamental problems relating to grasping and manipulating objects within an articulated, multifingered hand: determining how hard to squeeze an ob ject in order to ensure a secure grasp, determining the finger- joint motions required to produce a desired motion of the object, and determining the workspace of the hand.
Abstract: This paper discusses three fundamental problems relating to grasping and manipulating objects within an articulated, multifingered hand: determining how hard to squeeze an ob ject in order to ensure a secure grasp, determining the finger- joint motions required to produce a desired motion of the object, and determining the workspace of the hand.Squeezing the object, or the application of internal grasp forces, is reduced to a linear programming problem which considers friction and joint torque limit constraints. The relationship between the finger-joint motions and the motion of the object, for the case of pure rolling between the finger tips and the object, is formulated as a set of differential equa tions. The total workspace for a hand is determinedfor spe cial cases of planar and spatial hands.
864 citations
TL;DR: The Stewart Platform is one example of a parallel connection robot manipulator as discussed by the authors, and it has been used extensively in the past several years for a variety of tasks in the field of robotics.
Abstract: The Stewart Platform is one example of a parallel connection robot manipulator. This paper summarizes work that has been done at Oregon State University over the past several years on this topic. T...
820 citations
TL;DR: The decomposition of TPP is summarized by the equation TPP => PPP + VPP, and VPP is transformed to a two-dimensional PPP in path-time space with some additional constraints.
Abstract: We present a novel approach to solving the trajectory plan ning problem (TPP) in time-varying environments. The es sence of our approach lies in a heuristic but natural decom position of TPP into t...
795 citations
TL;DR: In this article, a theoretical exploration of the mechanics of pushing is presented and applied to the analysis and synthesis of robotic manipulator operations, and the results show that pushing is an essential component of many manipulator operations.
Abstract: Pushing is an essential component of many manipulator operations. This paper presents a theoretical exploration of the mechanics of pushing and demonstrates application of the theory to analysis and synthesis of robotic manipulator oper ations.
602 citations
TL;DR: In this article, the inertial parameters of manipulator rigid-body loads and links have been automatically estimated as a result of gen eral movement, and the Newton-Euler equations have been recast to relate linearly.
Abstract: The inertial parameters of manipulator rigid-body loads and links have been automatically estimated as a result of gen eral movement. The Newton-Euler equations have been recast to relate linearly ...
512 citations
TL;DR: This paper presents a system that recognizes objects in a jumble, verifies them, and then determines some essential configurational information, such as which ones are on top, by analyzing the patterns of range data predicted from all the hypotheses.
Abstract: A system that recognizes objects in a jumble, verifies them, and then determines some essential configurational information, such as which ones are on top, is presented. The approach is to use three-dimensional models of the objects to find them in range data. The matching strategy starts with a distinctive edge feature, such as the edge at the end of a cylindrical part, and then “grows” a match by adding compatible features, one at a time. (The order of features to be considered is predetermined by an interactive, off-line feature-selection process.) Once a sufficient number of compatible features has been detected to allow a hypothesis to be formed, the verification procedure evaluates it by comparing the measured range data with data predicted according to the hypothesis. When all the objects in the scene have been hypothesized and verified in this manner, a configuration-understanding procedure determines which objects are on top of others by analyzing the patterns of range data predicted from all the hypotheses. Experimental results of the system’s performance in recognizing and locating castings in a bin are presented.
481 citations
TL;DR: The relationship of backprojections to goal recognizability is discussed within the formal framework of preimages and suggests a partitioning of desired goal states into recognizable goal states.
Abstract: This paper outlines a method for planning motions in the presence of uncertainty. Tasks are modeled as geometrical goals in configuration space. The planning process consists of determining regions from which particular motions are guar anteed to reach a desired goal successfully. An algorithm is presented for backprojecting from desired goal states. The backprojection regions are computed by erecting constraints that geometrically capture the uncertainty in motion. The relationship of backprojections to goal recognizability is discussed within the formal framework of preimages. This relationship suggests a partitioning of desired goal states into recognizable goal states. Backprojections are actually per formed from this partitioning.
257 citations
TL;DR: The minimum-time path for a robot arm is presented which involves joint-space tessellation, a dynamic time-scaling algorithm, and a graph search and it was found that optimal paths tend to be nearly straight lines in joint space.
Abstract: The minimum-time path for a robot arm has been a long standing and unsolved problem of considerable interest. We present a general solution to this problem which involves joint-space tessellation, a dynamic time-scaling algorithm, and a graph search. The solution incorporates full dynamics of movement and actuator constraints, and can easily be extended for joint limits and workspace obstacles. It was found that optimal paths tend to be nearly straight lines in joint space. We discuss implementation difficulties due to the tessellation and to combinatorial proliferation of paths.
TL;DR: In this article, a shearing model is used to describe the contact friction and a spectrum of contact conditions defined by the fingertip radius and contact area relative to the object size.
Abstract: For practical reasons, compliant materials are often used on the gripping surfaces of robotic hands. Such materials are not well described by the Coulomb friction law or by simple point-contact or line-contact kinematics. In this paper, a shearing model is used to describe the contact friction. Models ofpointed, curved, flat, soft, and soft-curved fingertips are then developed and compared in terms of their contribu tion to the stiffness and stability of a simple grasp. There is a spectrum of contact conditions defined by the fingertip radius and contact area relative to the object size. This spectrum provides insights for designing and controlling robotic fingers.
TL;DR: The first part of the paper reviews the functional organization of the system, going through world modeling, trajectory generation, force control, and synchroni zation, and describes actual robot programming examples.
Abstract: In this paper, we present a general purpose manipulator control system. The system is run under the Unix operating system. Manipulator programs are written in the "C" lan guage and make use of primitive functions included in a library. Manipulator control is thus integrated within the lan guage in the same manner as is input-output. The system includes a world modeler and a trajectory generator that are accessed through two sets of primitive functions. The sys tem's structured world modeler is designed for an easy inte gration of sensors. The first part of the paper reviews the functional organization of the system, going through world modeling, trajectory generation, force control, and synchroni zation. The second part describes actual robot programming examples.
TL;DR: In this article, a new actuator of a joint mechanism is proposed, composed of two TiNi alloy wires, and the experiments of the position and force control systems of the actuator are carried out.
Abstract: A new actuator of a joint mechanism is proposed, composed of two TiNi alloy wires.First, the static and dynamic properties of the TiNi alloy wire that were not known are analyzed. Then the mathemati cal model of the actuator is induced. Next, the control sys tems of the actuator are synthesized by pulse width modu lated (PWM) controllers, and the mathematical models of the control systems are then obtained. Finally, the experiments of the position and force control systems of the actuator are carried out. It is proved that the theoretical models obtained are valid and that the position and force controls of this actuator are possible.Moreover, the unknown characteristics of the other well- known type of actuator composed of a TiNi alloy wire and an ordinary spring are also analyzed by the above procedure. The mathematical models are presented.
TL;DR: The symmetries studied describe motion of the body and legs in terms of even and odd functions of time to describe symmetric running for systems with any number of legs and for a wide range of gaits.
Abstract: Symmetry can simplify the control of dynamic legged systems In this paper, the symmetries studied describe motion of the body and legs in terms of even and odd functions of time A single set of equations describes symmetric running for systems with any number of legs and for a wide range of gaits Techniques based on symmetry have been used in laboratory experiments to control machines that run on one, two, and four legs In addition to simplifying the control of legged machines, symmetry may help us to understand legged locomotion in animals Data from a cat trotting and galloping on a treadmill and from a human running on a track conform reasonably well to the predicted symmetries
TL;DR: In this paper, workspace analysis is not merely a tool of volumetric analysis, but also has broad implications in the configuration synthesis of robot manipulators, using the term workspace theory.
Abstract: This paper demonstrates that workspace analysis is not merely a tool of volumetric analysis. In order to emphasize its broad implications in the configuration synthesis of robot manipulators, we use the term workspace theory. After re viewing some recent research on robot workspaces, it is shown that workspace theory leads to an anthropological observation in biomanipulation, qualitative transformations of holes and voids (central or toroidal), the geometric inversion method for the prediction of the number of solution sets, the existence of solution transition boundaries within the workspace (dex terous or total), and the influence oTjoint variable limits on the workspace and the multiplicity of solution sets.
TL;DR: In this paper, the regional structure of a manipulator, which consists of the three inboard joints and their associated members, determines the workspace shape and volume, and the orientation structu...
Abstract: Broadly speaking, the regional structure of a manipulator, which consists of the three inboard joints and their associated members, determines the workspace shape and volume.The orientation structu...
TL;DR: The zero reference position method as mentioned in this paper is a new method ofkinematic analysis of manipulators, which is easy to learn and is not prone to errors of interpretation, and it is shown that this method leads to a modular approach to the closed-form solutions for manipulators with ordinary or geared three-roll wrists.
Abstract: This paper presents a new method ofkinematic analysis of manipulators, called the zero reference position method. In this method, the description of the manipulator is in terms of the axes directions and locations in the zero reference posi tion. This position is a conveniently chosen position in which all joint variable values are defined to be zero. This type of manipulator description is easy to learn and is not prone to errors of interpretation. The governing kinematic equations of the manipulator are derived from the principle of similarity. In this paper, it is shown that this method leads to a modular approach to the closed-form solutions of manipulators with ordinary or geared three-roll wrists. Complete solutions for six types of contemporary industrial robots are included.
TL;DR: Most manipulators in use today are kinematically simple, and closed-form symbolic equations are the most efficient means of expressing their kinematics as discussed by the authors, and the analysis presented in this paper is base...
Abstract: Most manipulators in use today are kinematically simple, and closed-form symbolic equations are the most efficient means of expressing their kinematics. The analysis presented in this paper is base...
TL;DR: The redundancy is utilized for enabling collision-free motion for a given tra jectory of a manipulator hand by calculating the corre sponding trajectory in the space of joint coordinates using several performance criteria that take into account the vicinity of the obstacles.
Abstract: The redundancy of robot manipulators plays an important role in increasing their flexibility and versatility, especially in an environment with obstacles. In this paper, the redundancy is utilized for enabling collision-free motion for a given tra jectory of a manipulator hand. The calculation of the corre sponding trajectory in the space of joint coordinates is per formed using several performance criteria that take into account the vicinity of the obstacles. The advantages and shortcomings of the proposed algorithms are discussed. The implementation of the algorithms is real-time due to modest computational complexity.
TL;DR: In this article, a method for determination of the configurations of a manipulator and associated displacement functions that are based on the determination of singularities in motion of the mechanical system is presented.
Abstract: A manipulator is considered as a system of rigid bodies interconnected by joints that permit relative motions with certain degrees of freedom. Nonlinear equations that relate the parameters of relative motions generally do not provide unique solutions, and consequently the bodies (links) of the mechanical system may form various configuratxons.The authors propose a method for determination of the configurations of this mechanical system and associated displacement functions that are based on the determination of singularities in motion of the mechanical system. Applica tion to the execution of prescribed trajectories by the Uni mation Puma Manipulator is also presented.
TL;DR: This paper examines the geometry of a group of closed-loop manipulators with structures based on a planar, revolute jointed, five-bar chain and some general guidelines are laid down to assist the designer in making rational choices in selecting manipulator link lengths.
Abstract: This paper examines the geometry of a group of closed-loop manipulators with structures based on a planar, revolute jointed, five-bar chain. Of primary interest is the influence of the link lengths on the reachable workspace of the manipula tor. Unlike the commonly used open-loop manipulators, the entire workspace for a closed-loop manipulator will not be freely reachable, in general. The issues pertaining to the independent mobility of the driving links are discussed at length. A classification is made based on mobility criteria, and these mechanisms are further categorized into two types depending upon the influence of the link lengths on the ma nipulator's workspace. Based on this analysis, some general guidelines are laid down to assist the designer in making rational choices in selecting manipulator link lengths.
TL;DR: A system which locates and grasps parts from a pile using photometric stereo and binocu lar stereo as vision input tools and a collision-free grasp configuration is computed and executed using the attitude and range data.
Abstract: This paper describes a system which locates and grasps parts from a pile. The system uses photometric stereo and binocu lar stereo as vision input tools. Photometric stereo is used to make surface ...
TL;DR: In this paper, a method for identifying conditions governing all singular configurations of simple six-link ma nipulators whose inverse kinematic position problems have closed-form solutions is presented.
Abstract: This paper presents a new method for identifying conditions governing all singular configurations of simple six-link ma nipulators whose inverse kinematic position problems have closed-form solutions. The method is developed based on the concepts of service sphere, free service region, and dextrous wrist. For a simple six-link manipulator, we identify its singular state with finite internal degrees of freedom by using the conditions that cause the manipulator's inverse solutions to be indeterminate. Meanwhile its singular state with infini tesimal internal degrees of freedom can be identified by examining the determinant of the Jacobion of the first three links. This simple and straightforward method is illustrated by three examples.
TL;DR: In this paper, it is shown that if two objects in contact can be moved to another configuration in which they are in contact, then there is a way to move them from the first configuration to the second configuration such that the objects remain in contact throughout the motion.
Abstract: The use of computers in the design, manufacture, and ma nipulation of physical objects is increasing. An important aspect of reasoning about such actions concerns the motion of objects in contact. The study of problems of this nature requires not only the ability to represent physical objects but also the development of a framework or theory in which to reason about them. In this paper such a development is in vestigated and a fundamental theorem concerning the motion of objects in contact is proved. The simplest form of this theorem states that if two objects in contact can be moved to another configuration in which they are in contact, then there is a way to move them from the first configuration to the second configuration such that the objects remain in contact throughout the motion. This result is proved when translation and rotation of objects are allowed. The problem of more generalized types of motion is also discussed. This study has obvious applications in compliant motion and in motion planning.
TL;DR: The use of ultrasonic range finding to gather data about object surfaces in an air transmission medium poses several problems as discussed by the authors, such as there is very little information returned in a single range measurement.
Abstract: A generic range sensor is a member of a collection of sensors that provide surface location information. This collection includes ultrasonic, laser, structured light, and tactile sensors. The tactile sensor can be viewed as a degenerate range sensor when in contact with the surface. This paper will deal pri marily with the ultrasonic range sensor, which is probably the most difficult to handle, but extension of the techniques to other sensors is apparent.The use of ultrasonic range finding to gather data about object surfaces in an air transmission medium poses several problems. First, there is very little information returned in a single range measurement. One range measurement tells us that some surface exists, approximately orthogonal to the transmission axis of the transducer, at the measured range. However, the surface can lie anywhere within the sensitivity pattern of the transducer, and it can be oriented at any angle that reflects energy back to the transducer. Moving the trans ducer adaptively al...
TL;DR: In this paper, the authors present a new approach to design a simple manipulator with better dynamic behavior based on eliminating coefficients of nonlinear terms in the system's kinetic and potential energy equations.
Abstract: This paper presents a new approach to designing a simple manipulator with better dynamic behavior. The method is based on eliminating coefficients of nonlinear terms in the system's kinetic and potential energy equations. Accordingly, a set of design criteria regarding the link's inertia distribu tion can be established for each robot type. A robot designed to satisfy these criteria will result in much simplified dy namics. Also we find that for some configurations of three- and four-link robots, it is possible to design for completely linearized dynamic equations.
TL;DR: In this paper, the closure equations of a robot manipulator were used to solve the angular or linear displacements required at each of the joints of a manipulator to attain a specified position and orientation of its hand.
Abstract: The angular or linear displacements required at each of the joints of a robot manipulator to attain a specified position and orientation of its hand are obtained by solving the closure equations of the manipulator These equations express the fact that the sequence of coordinate transformations between each link of the manipulator from its hand to its base must equal the transformation from the hand to the base directly It is well known that the 4 X 4 homogeneous form of the point coordinate transformation matrix together with special coor dinate frames adapted to the structure of a manipulator yield a standard form of these coordinate transformation matrices known as the Denavit-Hartenberg matrix (Paul 1981) It is not so well known that the transformation equations of the coordinates of lines in these special coordinate frames may be used as well (Pennock and Yang 1985) Furthermore, by introducing dual numbers, the 6 X 6 matrices that arise col lapse into 3 X 3 orthogonal matrices with dual number ele
TL;DR: In this paper, a wrist mechanism with a large angular work space without any singularities is presented. But, although the singularities exist, they are allocated to a single wrist position outside the mechanical limits.
Abstract: A robot that responds to sensed changes in its environment needs well-conditioned kinematics to maintain adequate dynamic performance and to avoid practical difficulties with flexible cables and actuator limits. We show that it is possi ble to design a wrist mechanism with a large angular work space without any singularities. Although the singularities exist, they are allocated to a single wrist position outside the mechanical limits. The kinematics of the mechanism show that, although the degeneracy cone is larger than for the other wrist mechanisms, it is also largely outside the me chanical limits. Some extensions of the established concept of singularity cones are required. We introduce the concept of "least favorable reorientation " to define the usable workspace of the wrist. Dynamic performance specifications for the wrist are framed in terms of desired single actuator responses under given worst-case situations. Lightweight linear hydrau lic actuators have been used; however, the design can be rea...
TL;DR: The internal structure and the mathematical basis of a generalized computer program developed for this purpose and methods based on truncated trigonometric series for the off-line planning of robot trajectories and methods for the planning of multiple-segment robot motions with minimum cycle times are presented.
Abstract: Off-line planning of tasks and robot motion via the computer- graphics simulation of the robot and its environment is dis cussed. The internal structure and the mathematical basis of a generalized computer program developed for this purpose are described. Methods based on truncated trigonometric series for the off-line planning of robot trajectories and methods for the planning of multiple-segment robot motions with minimum cycle times are presented. The dynamic aspects of motion trajectories are discussed in relation to the generation of these time-optimal motions.