Showing papers on "Kinematics published in 1974"

On the Design of Computer Controlled Manipulators

Abstract: In connection with researches in the area of Artificial Intelligence, several studies have been made of mechanical manipulators for use under computer control This paper summarizes these results, and gives the reader an overview of problems associated with the design, kinematics and control of mechanical manipulators Some new results on kinematics are presented

Near-field motions from kinematic models of propagating faults

Abstract: Adaptation of existing solutions to the problem of edge and screw dislocations, which propagate with constant velocity along the fault plane, leads to very compact expressions that can be used as elementary solutions in the construction of near-field motions from arbitrarily complicated faulting in a uniform material. Two obvious limitations, two-dimensionality and the approximation of the free surface, may not be as severe a restriction on the applicability of the method as commonly assumed. Application of the method includes calculation of a profile of displacement, velocity, and acceleration wave forms over a dipping thrust fault. The variation of peak amplitudes with distance for these profiles suggests that the difference in intensity of ground motion on either side of a dipping fault decreases with an increase in the predominant frequency of the motion; hence, particle velocity shows less difference than particle displacement. Other applications include interpretations of near-fault strong-motion recordings. These studies point up the importance of the component of motion perpendicular to the fault. The amplitude of this motion is a strong function of the ratio of rupture to shear velocity and can dominate the near-field motions. As a final application, the spectra of the motions show that the simple near-field spectrum proposed by Brune (1970) on the basis of instantaneous rupture does not hold, even for the parallel component of motion at a small distance from the fault. Brune's modifications for finite rupture propagation seem to be qualitatively correct: the modulation produces an additional ω −1 factor in the spectrum. This will have the effect of limiting the maximum particle acceleration, which, according to simple source theory, can be infinite even with modest stress drops.

An Experimental Study of the Kinematics of Flow Through Hoppers

Abstract: An experimental study of the kinematics of the gravity flow of granular materials through hoppers is presented. A radiographic technique was employed to determine simultaneously the velocity and porosity fields in a granular material flowing through a model hopper. It was found that the flow of granular materials through hoppers is characterized by regions of rigid body motion interspersed with narrow bands of drastic change in void ratio and velocity. A major conclusion of this study is that the kinematic assumptions employed in previous theoretical analyses of granular materials flowing through hoppers or in converging channels are not consistent with the salient kinematic phenomena observed. Knowledge of the kinematic phenomena detailed here is basic to the proper analysis and design of hoppers.

Interplanetary stream magnetism: Kinematic effects

Abstract: The particle density, and the magnetic field intensity and direction are calculated in corotating streams of the solar wind, assuming that the solar wind velocity is constant and radial and that its azimuthal variations are not two rapid. The effects of the radial velocity profile in corotating streams on the magnetic fields were examined using kinematic approximation and a variety of field configurations on the inner boundary. Kinematic and dynamic effects are discussed.

Kinematics of small angle scattering

Abstract: In beam‐recoil measurements of the scattering of molecules by electrons or photons, deflected molecules are observed at very small angles, comparable to the angular divergences of the observed and crossing beams. A kinematic analysis is presented that explicitly includes the effects of these divergences. Distinguishing features of the analysis include the transformation to apparatus fixed vs ``laboratory'' coordinates and the calculation of the integrals over a finite detector in center of mass coordinates. The latter feature permits a simple recipe for inversion of laboratory observations to obtain a center of mass differential cross section.

Kinematics of the MIT-AI-VICARM Manipulator

Abstract: This paper describes the basic geometry of the electric manipulator designed for the Artificial Intelligence Laboratory by Victor Scheinman while on leave froin Stanford University. The procedure for finding a set of joint angles that wi l l place the terminal device in a desired position and orientation is developed in detail. This is one of the basic primitives that an arm controller should have. The orientation is specified in terms of Euler-angles. Typically eight sets of joint angles wi l l produce the same terminal device position and orientation. This report describes research done at the Artificial Intelligence Laboratory of the Massachusetts Institute of Technology. Support for the laboratory's artificial intelligence research is provided in part by the Advanced Research Projects Agency of the Department of Defense under Office of Naval Research contract N00014-70-A0362-0005. Working Papers are informal papers Intended for Internal use.

Perturbation formulations for satellite attitude dynamics

Abstract: Two analytical developments for the arbitrarily torqued motion of an asymmetric rigid body, both of which utilize a new torque-free solution as the reference motion, are presented. The first is an Encke-type perturbation formulation in which differential equations for the angular velocity and orientation departures from Poinsot motion are derived. The second technique is a variation of parameters scheme in which an analogue of Herrick's two-body perturbative differentiation technique is employed. The torque-free motion constants selected for variation are initial orientation and initial angular velocity; differential equations which specify the time variation of these parameters are developed, so that the torque-free solution is then instantaneously valid in the presence of arbitrary torques. Both developments are motivated by classical perturbation theories in orbital mechanics. Extensive use is made of the Euler parameter description of body orientation and kinematics rather than the more conventional Euler angles in order to avoid the geometrical singularities implicit in the latter.

Biomechanics of Walking Up Stairs

Abstract: Some results concerning the kinematics and dynamics of walking up stairs are presented. In particular the kinematics variables are analysed by a Fourier series expansion, and the muschular moments at the lower limbs articulations are computed according to a mechanical model of the system: some energetical considerations are also included.

Applied mechanics for engineering technology

Abstract: I. STATICS 1. Introduction 2. Forces, Vectors, and Resultants 3. Moments and Couples 4. Equilibrium 5. Structures and Members 6. Three-Dimensional Equilibrium 7. Friction 8. Centroids and Center of Gravity 9. Moment of Inertia II. DYNAMICS 10. Kinematics: Rectilinear Motion 11. Kinematics: Angular Motion 12. Plane Motion 13. Kinetics 14. Work, Energy, and Power 15. Impulse and Momentum Answers to Problems Index

Kinematic effect in the classical domains and the redshift phenomena of extragalactic objects

Abstract: Starting from the principle of relativity and the local constancy of the light velocity, in this paper we establish a space-time model with the classical domain D λ (1, 4). We discuss the kinematic effect in it and calculate the frequency shift of the spectral line, and also under the assumption of uniform distribution we compare our result with the observational data of the quasar N-Z relation. Our result shows that the large red shift in the extragalactic objects perhaps is not caused mainly by the Doppler effect, but to a large extent is a distance effect in the λ λ (1, 4) [its group of motion being SO (3,2)] is possibly a better model for large-scale space-time.

Slip Line Field of Anisotropic Soil

Abstract: Slip lines in any media should represent kinematic lines along which relative displacement of the material is possible. To determine velocity characteristics, equations governing the distribution of velocities must be formulated. Using the two equations for the velocity components in plastic flow, authors derive the differential equation for the isotropic case and for plastic-rigid media, and investigate several velocity equations along the slip lines, then determine the stress and velocity field for the Prandtl problem in anisoptropic media. They concluded that the equilibrium equations and the velocity equations are hyperbolic for the yield function when the second invariant of the stressed state increases linearly with p. In perfectly-plastic-rigid media the velocity characteristics coincide with the stress characteristics. Applications for engineering problems of plane-strain nature may be made using the conventional method of the isotropic case together with the relevant relationships along the characteristics as derived in the paper. /Author/

Design considerations for vehicle state control by the point- follower method

Abstract: This paper examines some considerations in the design of point- follower control, a technique in which vehicles are constrained to follow hypothetical points which move along the guideway in a synchronous manner. In addition, a control system design is presented for a particular vehicle model and for a propulsion system model based on a D. C. motor. A kinematic analysis is presented which is used to establish constraints on the velocity trajectories of moving points during speed transitions or during point-skipping maneuvers. This is followed by a discussion of point-follower dynamics.

A general method for sensitivity analysis of plane mechanism

Abstract: The paper describes a general method for the sensitivity analysis of plane mechanisms, particularly suited for use with automatic computation facilities. The sensitivity coefficients are computed through “macros”, thus greatly reducing the effort and the background required by the designer. The problem is solved by reducing it to a subcase of kinematic analysis of the general equivalent kinematic chains of the macros. The method can be applied to tolerance analysis, and to dynamic analysis in order to determine the forces (virtual work theorem) or the law of motion (Lagrande equations).

Kinematics Of Knee Motion During A Simulated Car Crash

Abstract: The human legs provide strong resistance to motion during a car crash. Laboratory simulators of large deceleration accidents typically utilize anthropomorphic dummies in place of human volunteers. In order to better understand the biomechanics of car crash injury and to develop more realistic dummies, improved knowledge of knee kinematics must be obtained. Most mathematical and physical analogs of human knees consider the motion to be modeled by a hinge or pin type joint. In recent years, many complex models have been suggested to better approximate the knee in walking. The present research suggests that the simplicity of a pinned joint be retained, but that the pin location be chosen to best simulate the in-plane motion of the human knee. High speed flash x-rays of the knee region were photographed during a highly simplified mock car crash. The relative positions of a rotating femur about a fixed tibia were observed over a 25° range or rotation. Using an optimization method, an effective pivot location was found that most closely matched the complex motion of the actual knee. The results of this preliminary study show this optimum pin position to be nearly 2.5 cm from the pin location that would have been obtained by constraining the location to lie along the tibia centerline (a geometric center). Also, the appropriate pin position was located more anterior than for tests with non-weight bearing and cadaver subjects.© (1974) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Synthesis of Complex Cam Mechanisms

Abstract: General equations are developed describing the kinematic behaviour of two rigid bodies in contact. The case of planar motion is then considered in more detail and the equations are developed in a form which is useful in synthesizing cam mechanisms.Examples of the application of the general equations to synthesizing the profiles of rolling contact cams and of cam profiles for use with flat and circular followers are given. Use of the general equations in cases where the follower has a complex profile is also described.