Showing papers on "Kinematics published in 1993"

Structural properties and classification of kinematic and dynamic models of wheeled mobile robots

Abstract: The structure of the kinematic and dynamic models of wheeled mobile robots is analyzed. It is shown that, for a large class of possible configurations, they can be classified into five types, characterized by generic structures of the model equations. For each type of model the following questions are addressed: (ir)reducibility and (non)holonomy, mobility and controllability, configuration of the motorization, and feedback equivalence.

Kinematic and Dynamic Simulation of Multibody Systems: The Real-Time Challenge

Abstract: Dependent Coordinates and Related Constraints Equations- Kinematic Analysis- Dynamic Analysis: Mass Matrices and External Forces-Dynamic Analysis: Equations of Motion- Static Equilibrium Position and Inverse Dynamics- Numerical Integration of the Equations of Motion- Improved Formulations for Real Time Dynamics Linearized Dynamic Analysis- Special Topics-Forward Dynamics of Flexible Systems- Inverse Dynamics of Flexible Multibodies

Biomechanics of pitching with emphasis upon shoulder kinematics.

Abstract: The American Sports Medicine Institute conducts research to increase understanding of mechanisms involved in upper extremity injuries to throwing athletes. This paper presents a qualitative overview of pitching and a detailed quantitative description of arm motion about the shoulder during this highly dynamic activity. Data on kinematics of arm motions about the shoulder are presented for 29 elite throwers. The major motion about the shoulder is external/internal rotation. Scapulothoracic and glenohumeral flexibility permit the arm to reach an externally rotated position of 175°. Approximately 30 msec before release, the arm internally rotates 80°, reaching peak angular velocities near 7,000°/sec. In rehabilitation of injured throwers, there is a need to appreciate the highly dynamic nature of this skill and to attempt to simulate these dynamic motions and loads as part of the final phase of treatment before the athlete returns to competition.

Kinodynamic motion planning

Abstract: Kinodynamic planning attempts to solve a robot motion problem subject to simultaneous kinematic and dynamics constraints. In the general problem, given a robot system, we must find a minimal-time trajectory that goes from a start position and velocity to a goal position and velocity while avoiding obstacles by a safety margin and respecting constraints on velocity and acceleration. We consider the simplified case of a point mass under Newtonian mechanics, together with velocity and acceleration bounds. The point must be flown from a start to a goal, amidst polyhedral obstacles in 2D or 3D. Although exact solutions to this problem are not known, we provide the first provably good approximation algorithm, and show that it runs in polynomial time

Models of trajectory formation and temporal interaction of reach and grasp

Abstract: Our goal was to create a principled account of a body of behavioral kinematic data on reaching and grasping. We show how to transform an optimality principle for overall hand transport into a feedback control law and then incorporate look-ahead modules in the controller to compensate for delays in sensory feedback. This model describes the kinematics of hand transport under a variety of circumstances, including target perturbations. We then develop a model for the temporal coordination of reach and grasp. We provide an optimization principle for hand preshaping that trades off the costs of maintaining the hand in an open position and the cost of accelerating the change in grip size. This yields a control system for preshaping. We then show that a model that uses only expected duration for coordination, rather than kinematic or dynamic variables, can describe the kinematics of interaction of hand transport and preshape under a variety of circumstances, including perturbations of object position an...

Nonholonomic multibody mobile robots: Controllability and motion planning in the presence of obstacles

Abstract: We consider mobile robots made of a single body (car-like robots) or several bodies (tractors towing several trailers sequentially hooked). These robots are known to be nonholonomic, i.e., they are subject to nonintegrable equality kinematic constraints involving the velocity. In other words, the number of controls (dimension of the admissible velocity space), is smaller than the dimension of the configuration space. In addition, the range of possible controls is usually further constrained by inequality constraints due to mechanical stops in the steering mechanism of the tractor. We first analyze the controllability of such nonholonomic multibody robots. We show that the well-known Controllability Rank Condition Theorem is applicable to these robots even when there are inequality constraints on the velocity, in addition to the equality constraints. This allows us to subsume and generalize several controllability results recently published in the Robotics literature concerning nonholonomic mobile robots, and to infer several new important results. We then describe an implemented planner inspired by these results. We give experimental results obtained with this planner that illustrate the theoretical results previously developed.

Motion segmentation and qualitative dynamic scene analysis from an image sequence

Abstract: This article deals with analysis of the dynamic content of a scene from an image sequence irrespective of the static or dynamic nature of the camera. The tasks involved can be the detection of moving objects in a scene observed by a mobile camera, or the identification of the movements of some relevant components of the scene relatively to the camera. This problem basically requires a motion-based segmentation step. We present a motion-based segmentation method relying on 2-D affine motion models and a statistical regularization approach which ensures stable motion-based partitions. This can be done without the explicit estimation of optic flow fields. Besides these partitions are linked in time. Therefore, the motion interpretation process can be performed on more than two successive frames. The ability to follow a given coherently moving region within an interval of several images of the sequence makes the interpretation process more robust and more comprehensive. Identification of the kinematic components of the scene is induced from an intermediate layer accomplishing a generic qualitative motion labeling. No 3-D measurements are required. Results obtained on several real-image sequences corresponding to complex outdoor situations are reported.

Conversion of the kinematics of a car with n trailers into a chained form

Abstract: The authors propose a set of coordinates for the kinematics model of a car with n trailers with only two degrees of freedom The absolute position of the system is given by the location of the rear trailer By using these coordinates, the kinematic model is locally converted into a nilpotent, chained form Control strategies for chained systems can be applied to locally control a car with n trailers >

Inverse kinematics and geometric constraints for articulated figure manipulation

Abstract: Computer animation of articulated figures can be tedious, largely due to the amount of data which must be specified at each frame. Animation techniques range from simple interpolation between keyframed figure poses to higher-level algorithmic models of specific movement patterns. The former provides the animator with complete control over the movement, whereas the latter may provide only limited control via some high-level parameters incorporated into the model. Inverse kinematic techniques adopted from the robotics literature have the potential to relieve the animator of detailed specification of every motion parameter within a figure, while retaining complete control over the movement, if desired. This work investigates the use of inverse kinematics and simple geometric constraints as tools for the animator. Previous applications of inverse kinematic algorithms to conlputer animation are reviewed. A pair of alternative algorithms suitable for a direct manipulation interface are presented and qualitatively compared. Application of these algorithms to enforce simple geometric constraints on a figure during interactive manipulation is discussed. An implementation of one of these algorithms within an existing figure animation editor is described, which provides constrained inverse kinematic figure manipulation for the creation of keyframes.

Wrist motions in industry

Abstract: Cumulative trauma disorders (CTDs) are disorders of the body's tendons and nerves due to repeated exertions and excessive movements. Workers in industrial tasks who have to move their hands and wrists repeatedly and/or forcefully are susceptible to CTDs. One of the major research voids in the study of occupational wrist CTDs is the lack of quantification of the relationship between the known kinematic risk factors, such as wrist angle and repetition, and CTD risk. A quantitative surveillance study was performed in industry in which workers' three-dimensional wrist motions were monitored on the factory floor. A total of 40 subjects from eight industrial plants participated in this study (20 workers in each of two risk groups, low and high). The wrist motion parameters that were monitored for each subject were position, angular velocity, and angular acceleration measures in each plane of movement (radial/ulnar, flexion/extension, and pronation/supination). Descriptive analyses of these measures indicated that generally the mean of the high-risk subjects was larger in magnitude than that of their low-risk counterparts. However, only the velocity and acceleration parameters resulted in significant differences between low- and high-risk groups. These results demonstrate the importance of dynamic components in assessing CTD risk.

Inverse Kinematics of the General 6R Manipulator and Related Linkages

Abstract: This paper elaborates on a method developed by the authors for solving the inverse kinematics of a general 6R manipulator. The method is shown to be applicable to determining the joint variables associated with all series-chain manipulators and closed-loop linkages constructed in a single loop with revolute, prismatic, or cylindric joints. The method is shown to yield a single polynomial, of minimum degree, in terms of just one of the joint variables. Once the roots of this polynomial are found, the remaining variables are then usually determined from linear sets of equations. It is shown that this method works equally well for general geometries and for special geometries such as those chararcterized by intersecting or parallel joint axes.

On the Kinematic Design of Spherical Three-Degree-of- Freedom Parallel Manipulators:

Abstract: This article studies the kinematic design of different types of spherical three-degree-of-freedom parallel manipulators. The mechanical architectures presented have been introduced elsewhere. However, designs having at least one isotropic configuration are suggested here for the first time. Isotropic configurations are defined, in turn, as those configurations in which the Jacobian matrix, mapping the angular velocity vector of the effector into the joint velocities, is proportional to an orthogonal matrix. First, a review of the direct and inverse kinematics of spherical three-degree-of-freedom parallel manipulators is outlined, and a general form for the Jacobian matrix is given. Parallel manipulators with revolute or prismatic actuators are discussed. Then, the concept of kinematic conditioning is recalled and used as a performance index for the optimization of the manipulators. It is shown that this leads to designs having at least one isotropic configuration. Finally, a few examples of such designs are presented. 15 refs.

The Use of Robotics Technology to Study Human Joint Kinematics: A New Methodology

Abstract: Robotics technologies have been modified to control and measure both the force and position of synovial joints for the study of joint kinematics. One such system was developed to perform kinematic testing of a human joint. A 6-axis articulated robotic manipulator with 6 degrees of freedom (DOF) of motion was designed and constructed; a mathematical description for joint force and position was devised; and hardware and software to control forces applied to the joint, as well as position of the joint, were developed. The new methodology was utilized to simulate physiological loading conditions and to perform an anterior-posterior (A-P) translation test on a human cadaveric knee. Testing showed that this new system can simulate complex loading conditions and also measure the resulting joint kinematics.

Kinematic analysis of a Stewart platform manipulator

Abstract: The Stewart platform manipulator is a fully parallel kinematic linkage system that has major mechanical differences from typical serial link robots. Its closed kinematic chain and parallel linkage structure give it greatly rigidity and a high force-to-weight ratio. However, due to the lack of efficient algorithms for solving the kinematic equations, its potential application as a robotic manipulator is difficult to realize. A simplified algorithm for solving the forward kinematics of a six-link, six-degrees-of-freedom Stewart platform is proposed. The algorithm involves solving only three nonlinear simultaneous equations. Explicit expressions for some special configurations that can directly give the geometric limitations to motion (such as the highest position, lowest position, most titled position, most twisted position, etc.) in terms of the geometric dimensions of the platforms and the legs are derived. This information is being used to direct the design of an actual Stewart platform. >

Internal force-based impedance control for cooperating manipulators

Abstract: An internal force-based impedance control scheme for cooperating manipulators is introduced which controls the motion of the objects being manipulated and the internal force on the objects. The controller enforces a relationship between the velocity of each manipulator and the internal force on the manipulated objects. Each manipulator is directly given the properties of an impedance by the controller; thus, eliminating the gain limitation inherent in the structure of previously proposed schemes. The controller uses the forces sensed at the robot end effectors to compensate for the effects of the objects' dynamics and to compute the internal force using only kinematic relationships. Thus, knowledge of the objects' dynamics is not required. Stability of the system is proven using Lyapunov theory and simulation results are presented validating the proposed concepts. The effect of computational delays in digital control implementations is analyzed vis-a-vis stability and a lower bound derived on the size of the desired manipulator inertia relative to the actual manipulator endpoint inertia. The bound is independent of the sample time.

SMART/sup Wheels/: development and testing of a system for measuring manual wheelchair propulsion dynamics

Abstract: The purpose of this project was to develop a system for dynamically sensing pushrim propulsion forces and torques and to collect kinetic data with the device. A system was developed to detect the forces and torques applied to the wheelchair pushrim, record, store, and process the measured data, and display the kinetic information for analysis. Ten adults, including four male wheelchair users, three ambulatory men, and three ambulatory women, pushed a wheelchair with the SMART/sup Wheel/ on a dynamometer while their kinematics were videotaped. The kinetic data collected with the authors' wheel were correlated with stick figure representations of digitized kinematic data obtained through video analysis. The close agreement between the kinetic results and the kinematic results provided a temporal validation of the ability of the wheel to detect forces and torques applied to the wheelchair pushrim. The recorded forces and torques were in agreement with previously reported magnitudes. >

The geometry of the plate-ball problem

Abstract: A ball rolls without slipping between two horizontal plates separated by the distance equal to the diameter of the ball. It is assumed that the lower plate is fixed, and that the ball is rolled through the horizontal movement of the upper plate. The problem is to transfer the ball from a given initial position and a given initial orientation to a prescrived final position and final orientation along a certain path

Direct kinematics of parallel manipulators

Abstract: The determination of the direct kinematics of fully parallel manipulators is in general a difficult problem but has to be solved for any practical use. Various methods are presented to solve this problem: two kinds of iterative schemes, a reduced iterative scheme, and a polynomial method. The computation time of these methods are compared and their various advantages are shown. >

Kinematic design of serial link manipulators from task specifications

Abstract: The Reconfigurable Modular Manipulator System (RMMS) consists of modular links and joints that can be assembled into many manipulator configurations. This capability allows the RMMS to be rapidly reconfigured to custom tailor it to specific tasks. An important issue related to the RMMS is the determination of the optimal manipulator configuration for a specific task. This article addresses the problem of mapping kinematic task specifications into a kinematic manipulator configuration. For the design of two-degrees-of-freedom (2- DOF) planar manipulators, an analytical solution is derived. Because analytical solutions become impractical for problems with more than two design parameters, we have also developed a numerical approach for the design of 6-DOF manipulators. The numerical procedure determines the Denavit-Hartenberg (D-H) parameters of a nonredundant manipulator with joint limits that can reach a set of specified positions/orientations in an environment that may include parallelepiped-shaped obstac...

A Computational Model of the Simplest Motor Program.

Abstract: A computational procedure (program) is defined to generate control signals for the motoneuron pools of agonist and antagonist muscles that will move a limb segment from one stationary position to another. The program accounts for the ability to move different distances with different inertial loads and for the influence of instructions concerning movement speed and accuracy. These motor commands allow the program to produce EMG patterns as well as force and kinematic trajectories that are consistent with much of the data found in the literature of these movements. The program is premised on the notion that kinematically defined tasks are accomplished by programming commands to the motoneuron pools, based on only a few cognitively recognized kinematic and dynamic features of the task. Most of the features found in EMG and kinematic patterns can be considered consequences of the program's algorithmic procedures rather than specifically planned features of those movements.

An efficient method for inverse dynamics of manipulators based on the virtual work principle

Abstract: The computational efficiency of inverse dynamics of a manipulator is important to the real-time control of the system. For serial manipulators, the recursive Newton-Euler method has been proven to be the most efficient. However, for more general manipulators, such as serial manipulators with closed kinematic loops or parallel manipulators, it must be modified accordingly and the resultant computational efficiency is degraded. This article presents a computationally efficient scheme based on the virtual work principle for inverse dynamics of general manipulators. The present method uses a forward recursive scheme to compute velocities and accelerations, the Newton-Euler equation to calculate inertia forces/torque, and the virtual work principle to formulate the dynamic equations of motion. This method is equally effective for serial and parallel manipulators. For serial manipulators, its computational efficiency is comparable to the recursive Newton-Euler method. For parallel manipulators or serial manipulators with closed kinematic loops, it is more efficient than the existing methods. As an example, the computations of inverse dynamics (including inverse kinematics) of a general Stewart platform require only 842 multiplications, 511 additions, and 12 square roots.

Dynamics of Bipedal Gait: Part I—Objective Functions and the Contact Event of a Planar Five-Link Biped

Abstract: This article presents an approach that can be followed to formulate objective functions which can be used to prescribe the gait of a planar, five element, bipedal automaton during single support phase. The motion of the biped is completely characterized in terms of progression speed, step length, maximum step height, and stance knee bias. Kinematic relations have been derived and the inverse problem has been solved to perform a parametric study that correlates the regions of the four dimensional parameter space with the respective gait patterns

Use of a kinematic constraint in tracking constant speed, maneuvering targets

Abstract: The use of a kinematic constraint as a pseudomeasurement in the tracking of constant-speed, maneuvering targets is considered. The kinematic constraint provides additional information about the target motion that can be processed as a pseudomeasurement to improve tracking performances. A new formulation of the constraint equation is presented, and the rationale for the new formulation is discussed. The filter using the kinematic constraint as a pseudomeasurement is shown to be unbiased, and sufficient conditions for stochastic stability of the filter are given. Simulated tracking results are given to demonstrate the potential that the new formulation provides for improving tracking performance. >

Dynamic control of 3-D rolling contacts in two-arm manipulation

Abstract: When two or more arms are used to manipulate a large object, it is preferable not to have a rigid grasp in order to gain more dexterity in manipulation. It may therefore be necessary to control contact motion between the object and the effector(s) on one or more arms. This paper addresses the dynamic control of two arms cooperatively manipulating a large object with rolling contacts. In the framework presented here, the motion of the object as well as the loci of the contact point either on the surface of each effector or on the object can be directly controlled. The velocity and acceleration equations for three-dimensional rolling contacts are derived in order to obtain a dynamic model of the system. A nonlinear feedback control algorithm that decouples and linearizes the system is developed. This is used to demonstrate the control of rolling motion along each arm and the adaptation of grasps to varying loads.

A three‐dimensional cinematographical analysis of the volleyball spike

Abstract: The objectives of this study were to describe the volleyball spiking actions used by players in top‐level competition, and also to examine the interrelationships between upper limb, lower limb and whole body kinematic variables, and post‐impact ball speed in the spiking technique. Two Photosonics Biomechanics 500 cine‐cameras operating at a nominal frame rate of 100 Hz were used to film the spiking actions of 10 male senior international volleyball players at the XVI Universiade (1991 World Student Games). Three‐dimensional object space co‐ordinates of digitized image co‐ordinates were obtained using a DLT algorithm and an array of calibration points in the filmed volume. Relationships between lower limb angular kinematics at take‐off, centre of mass vertical velocity at take‐off and centre of mass vertical displacement (jump height) were examined. Relationships between angular kinematics of the hitting arm and post‐impact ball speed were also determined. The mean (± S.E.) centre of mass vertical velocity...

Closed-form resolution of the direct kinematics of parallel manipulators using extra sensors data

Abstract: In the most general case the measurement of the link lengths of a six-degree-of-freedom parallel manipulator is not sufficient to determine the actual unique posture of its platform. It is shown that by adding four sensors on the passive joints, a unique closed-form solution of the posture of the end-effector can be obtained for the most general case. It is shown that three sensors are sufficient for a particular mechanical architecture. >