Showing papers on "Acceleration published in 1995"

Method of training physical skills using a digital motion analyzer and an accelerometer

Abstract: A method of training and simulating physical skills using a digital motion analyzing device that measures the necessary and sufficient information to describe uniquely a rigid body motion. The device, comprising a programmable digital signal processor and a universal accelerometer, measures the acceleration and calculates the linear velocity, the angular velocity, the orientation, and the position of a moving object, and stores and plays back the motion using audiovisual means and compares it with other pre-recorded motions. The student can choose a model and try to imitate the model with the help of audiovisual means and biofeedback means. The device is portable. It can also be connected to a computer where the motion can be further analyzed by comparing it with a database comprising many other characteristic motions. If a projectile is involved, such as in a golf swing, the trajectory of the projectile is calculated.

Acceleration Rates and Injection Efficiencies in Oblique Shocks

Abstract: The rate at which particles are accelerated by the first-order Fermi mechanism in shocks depends on the angle, \teq{\Tbone}, that the upstream magnetic field makes with the shock normal. The greater the obliquity the greater the rate, and in quasi-perpendicular shocks rates can be hundreds of times higher than those seen in parallel shocks. In many circumstances pertaining to evolving shocks (\eg, supernova blast waves and interplanetary traveling shocks), high acceleration rates imply high maximum particle energies and obliquity effects may have important astrophysical consequences. However, as is demonstrated here, the efficiency for injecting thermal particles into the acceleration mechanism also depends strongly on obliquity and, in general, varies inversely with \teq{\Tbone}. The degree of turbulence and the resulting cross-field diffusion strongly influences both injection efficiency and acceleration rates. The test particle \mc simulation of shock acceleration used here assumes large-angle scattering, computes particle orbits exactly in shocked, laminar, non-relativistic flows, and calculates the injection efficiency as a function of obliquity, Mach number, and degree of turbulence. We find that turbulence must be quite strong for high Mach number, highly oblique shocks to inject significant numbers of thermal particles and that only modest gains in acceleration rates can be expected for strong oblique shocks over parallel ones if the only source of seed particles is the thermal background.

Relativistic ponderomotive force, Uphill acceleration, and transition to chaos.

Abstract: Starting from a covariant cycle-averaged Lagrangian the relativistic oscillation center equation of motion of a point charge is deduced, and analytical formulas for the ponderomotive force in a traveling wave of arbitrary strength are presented. It is further shown that the pondermotive forces for transverse and longitudinal waves are different; in the latter, uphill acceleration can occur. In a standing wave there exists a threshold intensity above which, owing to transition to chaos, the secular motion can no longer be described by a regular ponderomotive force.

Floating mass accelerometer

Abstract: A floating mass accelerometer having at least one elastic member contacting a mass that is supported by a low friction surface is disclosed. At least one proximity sensor is located adjacent the mass and provide an output based upon the distance between the sensor and the mass as regulated by the degree of elastic member flexion. Acceleration forces acting upon the mass cause the mass to move in response thereto, thereby causing deflection of the at least one elastic member. The change in distance between the mass and the at least one proximity sensor is relayed to a digital signal processor which processes the acceleration information and sends this information to a display and/or memory unit. In a preferred embodiment, a two axis accelerometer is disclosed wherein acceleration values greater than a predetermined level are stored in memory and may be recalled later to provide an indication as to acceleration forces encountered by the device. Alternative embodiments provide for an pre-impact monitor wherein a buffer holds acceleration information for the last time period; a shipping monitor wherein acceleration forces are time-tagged for later retrieval; a seismic monitor with an optional output relay capable of remote operations.

Unsteady flow about a sphere at low to moderate Reynolds number. Part 2. Accelerated motion

Abstract: A full numerical simulation based on spectral methods is used to investigate linearly accelerating and decelerating flows past a rigid sphere. Although flow separation does not occur at Reynolds numbers below 20 for a steady flow, in the linearly decelerating flow separation is observed at much lower Reynolds numbers with complete detachment of vorticity possible in certain cases. The existence of a large recirculation region contributes to the result that a negative viscous force on the sphere is possible. The contribution of the pressure to the force includes a component that is well described by the inviscid added-mass term in both the accelerating and decelerating cases. The force on the sphere is found in general to initially decay in a power law manner after acceleration or deceleration ends followed by rapid convergence at later times to the steady state. For the cases examined this convergence is found to be exponential except for those in which the sphere is brought to rest in which case the convergence remains algebraic. This includes the special case of an infinite acceleration or deceleration where the free stream velocity is impulsively changed.

H ∞ Control for Seismic-Excited Buildings with Acceleration Feedback

Abstract: Recently developed H∞ control techniques are used to design controllers to suppress the effects of earthquake ground motion on the response of building structures. In particular, controllers are designed to reduce both the interstory drift and the absolute acceleration of selected floors on which sensitive equipment may be installed. Further, the H∞ control techniques are extended to include the capability of using acceleration sensors, since direct measurement of floor accelerations is the most reliable and least expensive measurement to make in earthquake engineering applications. Simulation results for a six-story building are used to demonstrate the effectiveness of the control method presented.

Rate-of-rotation sensor

Abstract: A rate-of-rotation sensor comprises an oscillatory mass on which an acceleration sensor is disposed so that the acceleration sensor can be deflected parallel to the surface of the oscillatory mass. With this arrangement, a measurement of the Coriolis force parallel to the surface of the oscillatory mass is possible.

Maneuvering target tracking using adaptive turn rate models in the interacting multiple model algorithm

Abstract: This paper presents an interacting multiple model algorithm (IMM) utilizing adaptive turn rate models to track a maneuvering target. The turning rate is calculated at each time step from the velocity and acceleration estimates of the center filter as the magnitude of the acceleration divided by the speed of the target. The comparison of the tracking performance of the proposed algorithm is made with that of an IMM algorithm, utilizing a straight line motion model in conjunction with a single turn rate model which uses an estimate of the turn rate and also to that of an IMM algorithm utilizing three constant turn rate models.

Capacitor type acceleration sensor

Abstract: A capacitor type acceleration sensor is disclosed. In this sensor, an acceleration sensing element 1 has two variable capacitors C1 and C2 that are constructed with a couple of fixed electrodes and a movable electrode located between the fixed electrodes. Electrostatic power generation/feedback means 15 applies to the fixed- and movable-electrode pairs such an electrostatic power as to set the movable electrode at a preset reference position in accordance with the output signal of capacitance-difference detector means 10. The electrostatic power is outputted as an output signal of the capacitor type acceleration sensor. In the capacitor type acceleration sensor, another fixed capacitor Cx of which the capacitance value Cx is larger than the maximum capacitance-difference between the variable capacitors C1 and C2 of which the capacitance values vary in accordance with an acceleration, is connected in parallel with the variable capacitor C2. The capacitance (C2+Cx) is larger than the capacitance of the variable capacitor C1, irrespective of the direction of acceleration.

Multi-axial accelerometer-based sensor for an implantable medical device and method of measuring motion measurements therefor

Abstract: An improved sensor and related method for multi-axial measurement of motion for an implantable medical device is disclosed. The sensor has a wide variety of applications, including use as a cardiac wall motion sensor or a physical activity sensor. The sensor includes first and second conductors over which the motion measurements are made. A first transducer provides a first motion measurement indicative of sensor acceleration during a first phase, while a second transducer provides a second motion measurement indicative of sensor acceleration during a second phase. The first and second transducers are connected in parallel so as to provide the first and second motion measurements to an implantable medical device over the first and second conductors. The first and second phases are non-overlapping periods of time so that the motion measurements from each transducer are time division multiplexed. The sensor provides motion measurements that may either be compensated or uncompensated for temperature effects. In either case, the motion sensor uses fewer conductors than conventional sensors to deliver its measurements.

Rejection of disturbances on a disk drive by use of an accelerometer

Abstract: A disk recording and/or reproduction device subject to shock and vibration. The track following function of the transducer is augmented by an acceleration responsive sensor. The acceleration responsive sensor is sampled at a different frequency than the sampling frequency of the head disk assembly position error signal. The variations in the gain of the acceleration responsive sensors can be compensated for in real time.

Convective accelerometer and inclinometer

Abstract: A convective accelerometer and inclinometer includes two temperature sensing elements (12, 14) mounted within a sealed enclosure (22) containing a gas. The application of heat to the gas within the enclosure by a heating element (16) causes the gas to flow in a predetermined pattern in free convection. When linear acceleration (18) or inclination is applied to the enclosure, the convective flow of gas is affected, causing a temperature differential between the temperature sensing elements. This temperature differential is measured as a difference in electrical resistance between the two temperature sensing elements which is proportional to the acceleration. The device can be used to measure linear acceleration, velocity, position or inclination. The device can also be used as an inclinometer for measuring the angle of gravity. The device has a wide variety of applications within the automotive field.

Apparatus and method for tripping a system for the protection of occupants of a vehicle

Abstract: An apparatus for tripping a system for the protection of occupants of a vehicle has a first sensor (10) for sensing the acceleration of the vehicle in its direction of forward motion and a second sensor (12) for sensing the acceleration of the vehicle in a direction transverse to its direction of forward motion. The two sensors are under the control of control means (14, 16) which triggers the occupant protection system in dependence upon the signals from the first and second sensors (10, 12).

Optimal path planning for a trolley crane: fast and smooth transfer of load

Abstract: Optimal speed references were designed for a trolley crane. The path planning problem was split into five phases: vertical upward movement of the load; acceleration of the trolley while still hoisting the load; horizontal movement of the trolley with maximum velocity without hoisting; deceleration of the trolley while setting down the load; and vertical downward movement of the load. Energy optimal speed references for a given transfer time were computed for the so-called diagonal movements in which the load and trolley moved simultaneously. A dynamical model of the crane mechanics and actuators was used in the formulated optimal control problem. The transfer times for the diagonal movements were made as small as possible so that the given maximal angular velocities of the actuators were not exceeded. Speed references for the three other phases were easily obtained since they involved either hoisting only, or transfer of the trolley with constant velocity without hoisting. A pilot crane experiment with a scaled-down model has been carried out, and the results are given and discussed.

Highway traffic accident avoidance system

Abstract: An accident avoidance system in which a substantially continuous data stream consisting of multiple vehicle velocity and location information is processed by means that will generate advisories to vehicles that are approaching potentially hazardous situations. These advisories are in advance of the vehicles hazard encounter so that driver corrective action can be taken to avoid collision. For each vehicle along a monitored length of highway, means are provided for computing the vehicles actual acceleration or deceleration and for computing the deceleration required for the vehicle to avoid an accident. Collision avoidance advisories are generated whenever the vehicle's acceleration or deceleration deviates from the deceleration required to avoid a collision. Means are provided for detecting vehicles that may be operated by drivers whose performance is impaired.

Free-surface flow due to impulsive motion of a submerged circular cylinder

Abstract: The impulsively starting motion of a circular cylinder submerged horizontally below a free surface is studied analytically using a small-time expansion. The series expansion is taken as far as necessary to include the leading gravitational effects for two cases: constant velocity and constant acceleration, both commencing from rest. The hydrodynamic force on the cylinder and the surface elevation are calculated and expressed in terms of bipolar coordinates. Comparisons are also made with earlier theoretical and experimental work. The theory is valid for arbitrary value of submergence depth to cylinder radius.

Process for controlling driving stability with a yaw rate sensor equipped with two lateral acceleration meters

Abstract: A control process for controlling the driving stability of a motor vehicle is provided The difference between the actual value of the yaw rate and the desired value is measured in a control process to form the additional yawing moment for stabilizing the vehicle Instead of using yaw sensors for the direct measurement of the yaw rate (yaw angular velocity), two lateral acceleration meters are provided in the sensor Advantageous variants include the use of the yaw acceleration and/or its derivative as the controlled variable, instead of the yaw rate

Maximal power and torque-velocity relationship on a cycle ergometer during the acceleration phase of a single all-out exercise.

Abstract: Seven subjects pedalled on a Monark cycle ergometer as fast as possible for approximately 7 s against four different resistances which corresponded to braking torques (TB) equal to 19, 38, 57 and 76 N · m at the crank level. Exercise periods were separated by 5-min recovery periods. Pedal velocity was recorded every 50 ms by means of a disc with 360 slots fixed on the flywheel, passing in front of a photo-electric cell linked to a microcomputer which processed the data. Every 50 ms, the time necessary to perform half a pedal revolution (t1/2) was computed by adding the 50-ms periods necessary to reach 669 slots (the number of slots corresponding to half a pedal revolution). To measuret1/2 to an accuracy better than 50 ms, this time was computed by a linear interpolation of the time-slot number relationship. Power (P) was averaged duringt12 by adding the power dissipated against braking torque and the power necessary to accelerate the flywheel. The torque-velocity (T-ν) relationship was studied during the acceleration phase of a sprint against a single TB by computing every 50 ms the relationship between ν and T (N · m), equal to the sum ofTB and the torque necessary to accelerate the flywheel at the same time. The T-ν relationships calculated from the acceleration phase of a single all-out exercise were linear and similar to the previously described relationships between peak velocity and braking force. These relationships can be expressed as follows: ν = ν0,acc (1 −T/T0,acc) where ν is pedal velocity,T the torque exerted on the crank andT0,acc and ν0,acc have the dimensions of maximal torque and maximal velocity respectively. Based on this model, maximal power (Pmax,acc) is calculated as 0.257ν0, accT0, acc. Maximal powerPmax,acc measured with the acceleration method was independent of braking torqueTB and slightly higher thanPmax calculated from the relationship between peak velocity andTB.

Apparatus for the liner acceleration of electrons, particularly for intraoperative radiation therapy

Abstract: An apparatus for the linear acceleration of electrons, particularly for intraoperative radiation therapy, including: an articulated structure for moving a radiating head that comprises an acceleration structure constituted by a plurality of cavities; a modulator for generating, controlling, and transmitting a radio-frequency to the cavities of the acceleration structure; and processing and control devices adapted to control the apparatus; the modulator is separate from the radiating head and the connection occurs by virtue of waveguide means adapted to carry the radio-frequency to the acceleration structure.

Vehicle suspension device

Abstract: PROBLEM TO BE SOLVED: To avoid signal drift due to vehicle inclination and acceleration and deceleration speed in a front/rear direction which occurs at the time of acceleration or deceleration of a vehicle by forming control signals of respective shock absorbers based on a pitch component and a roll component under such a condition as a drift component is canceled. SOLUTION: In this vehicle suspension device, a bounce component, a pitch component, and a roll component are obtained by a bounce-pitch-roll component detecting means (d), and control signals of respective shock absorbers (b) are prepared by a preparing means (e) based on the respective components. The damping force characteristics of the respective shock absorbers (b) is variably controlled by a damping force characteristics controlling means (f) based on the respective controlling signals. When acceleration and/or deceleration states of a vehicle are detected by an acceleration/deceleration state detecting means (g), the bounce component is made 0 by a correcting controlling means (h), so that the control signals of the respective shock absorbers (b) are formed based on the pitch component and the roll component under such a condition as the drift component is canceled. COPYRIGHT: (C)1997,JPO

Finite Element Model Study of Head Impact Based on Hybrid III Head Acceleration: The Effects of Rotational and Translational Acceleration

Abstract: The translational and rotational components of acceleration measured at the center of gravity of a Hybrid III dummy head were used to investigate their individual and combined effects on a two-dimensional finite element model of the human brain. Each component of acceleration generated distinct patterns of deformation. Although translational acceleration is related to pressure and rotational acceleration has a dominant effect on shear deformations, complete acceleration (combination of translation and rotation) yielded the highest values in all stresses and produced a maximum shear stress at the top of the brain.

Optical reference geometry for stationary and axially symmetric spacetimes

Abstract: We discuss the acceleration and Fermi-Walker transport for the circular motion of particles, photons and gyroscopes in stationary, axially symmetric spacetimes in terms of the optical reference geometry.