Measuring and testing – Speed – velocity – or acceleration
Patent
1998-06-23
1999-11-23
Williams, Hezron
Measuring and testing
Speed, velocity, or acceleration
702141, 367117, 367129, G01S 172
Patent
active
059879831
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for measuring acceleration of a moving object.
BACKGROUND OF THE INVENTION
Acceleration (rate of change of velocity) is generally measured indirectly, by measuring the force exerted by, or restraints that are placed on, a reference mass to hold its position fixed in an accelerating body. Acceleration is computed using the relationship between restraint force and acceleration given by Newton's Second Law of Motion: the force is equal to the product of the mass and acceleration. Therefore, the precision by which acceleration can be determined is directly related to the precision by which force and mass can be measured.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a novel method and apparatus for measuring acceleration, which method and apparatus are capable of very high precision and which are not subject to the above limitations.
According to one aspect of the present invention, there is provided a method of measuring acceleration of a moving object, comprising: therewith, a body capable of transmitting pulses of energy; first location on the body in a second location on the body at a known distance from the first location; second location; and between the first and second locations, for determining acceleration of the body and thereby of the moving object.
It will thus be seen that the novel method is not based on the conventional approach for measuring acceleration by measuring a force, but rather is based on measuring the transit time of an energy pulse. The basic mechanism of operation can be considered to be analogous to two persons at opposite ends of a moving train car spaced by a distance S throwing a ball between them. As long as there is no acceleration, i.e. the car is moving at constant velocity, the transit time T of the ball from one end to the opposite end will be constant. However, when the velocity changes, i.e. the train accelerates or decelerates, a receiver of the ball will appear to be farther (upon acceleration) or closer (upon deceleration) from a thrower of the ball by "virtual distance change" .delta.s, which varies in magnitude and sign according to the acceleration. Thus, when the acceleration is positive in the direction in which the ball is thrown, the transit time T will be increased by .delta.t corresponding to the "virtual distance change" .delta.s, and, when it is negative, it will be decreased by .delta.t.
While the above method theoretically may be implemented by the use of electromagnetic pulses, it is particularly applicable when using the lower-velocity sonic pulses, and is therefore described below with respect to sonic pulses. In the above analogy, therefore, the ball corresponds to the sonic pulse. Although the transmission of a sonic pulse through a medium does not involve movement of mass particles through the medium in the same manner as in the ball analogy, it does involve movement of the energy of mass particles through the medium. Thus, as shown by the classical demonstration of Newton's Third Law of Motion ("to every action there is always an equal and opposite reaction") utilizing a line of suspended spherical balls in contact with each other, holding the first ball at one end of the line away from the next ball in the line, and releasing it to impact the next ball in the line, will produce an equal movement of the last ball at the opposite end of the line. The transmission of this energy from the first ball to the last ball is by a compressional, longitudinal (i.e. sonic) pulse. When the pulse is of electromagnetic energy, there is an analogous transmission of the energy through the body, although of course at a much higher velocity than the transmission of a sonic pulse.
As in the ball analogy, therefore, when a body is subjected to acceleration, a pulse transmitted through such a body will experience a transit time t.sub.B when not subjected to acceleration, an increased transit time t.sub.B +.delta.t corresponding to the "virtual distance cha
REFERENCES:
patent: 4094306 (1978-06-01), Kossoff
patent: 4095547 (1978-06-01), Benington
patent: 4408290 (1983-10-01), Kubo et al.
patent: 5659617 (1997-08-01), Fischer
Ariav Aryeh
Ravitch Vladimir
Kwok Helen C.
Williams Hezron
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