ON THE CLASSIFICATION OF ACCELEROMETERS USED TO MEASURE LINEAR ACCELERATIONS

A. M. Malyshenko

(Presented by the scientific seminar of the Faculty of Automation and Computer Engineering)

Despite the large number of patented types of accelerometers described in the literature and their broad use in engineering, there is still no sufficiently complete and generally accepted classification of them.

As a rule, accelerometers are classified according to some single feature, for example, according to the nature of the dependence of the output quantity on the acceleration measured by the instrument [1, 2], according to the type of displacement sensor of the inertial mass [3], and so on. Such classifications do not give a complete picture of the principle of operation and the design of a particular accelerometer. In our view, the classification proposed by I. A. Gorenshtein, I. A. Shulman, and A. S. Safaryan [4] is the most successful; however, it too is not complete.

In the present work a classification is proposed for accelerometers used to measure linear accelerations. It is based on the division of accelerometers according to their purpose, characteristic features, and design factors.

All accelerometers used to measure linear accelerations may be classified according to the following features:

1. By purpose:

a) accelerometers for measuring linear accelerations under impacts (measurement of accelerations of a sharply expressed impulse type);

b) accelerometers for measuring accelerations of devices whose motions are spatially limited (for example, for measuring accelerations of the motion of individual parts of mechanisms);

c) accelerometers for measuring accelerations of moving objects (aircraft, rocket, ship, etc.).

1. By the measured value of the controlled acceleration:

a) accelerometers measuring the instantaneous value of the acceleration of the controlled motion;

b) accelerometers measuring the mean value of the acting acceleration over some short interval of time;

c) accelerometers measuring the maximum value of the controlled acceleration (so-called “peak accelerometers”).

1. By the number of measured components of acceleration:

a) accelerometers measuring the component of acceleration along one axis (single-component accelerometers);

b) accelerometers that measure the components of acceleration along two mutually perpendicular axes (two-component accelerometers);

c) accelerometers that measure the components of acceleration along three mutually perpendicular axes (three-component accelerometers).

1. According to the nature of the change over time of the output quantity:

a) accelerometers with an output quantity of a continuous nature;

b) accelerometers with an output quantity of a discrete nature.

1. According to the nature of the dependence of the output quantity on the acceleration being measured:

a) accelerometers with an output quantity proportional to the magnitude of the acceleration being measured;

b) accelerometers with an output quantity proportional to the time integral of the acceleration being measured;

c) accelerometers with an output quantity proportional to the double time integral of the acceleration being measured.

Accelerometers of the first group may be called nonintegrating accelerometers; instruments of the second group—single-integrating, and instruments of the third group—double-integrating accelerometers.

1. According to the structural scheme:

a) accelerometers with an open-loop action chain (accelerometers of the noncompensating type);

b) accelerometers with a closed-loop action chain (accelerometers of the compensating type).

1. According to the type of inertial mass used:

a) accelerometers with an inertial mass made of a solid body;

b) accelerometers with a liquid inertial mass;

c) accelerometers using the inertial properties of the motion of charged particles and electrons.

1. According to the state of the inertial mass in the absence of accelerations:

a) accelerometers in which, in the absence of accelerations, the inertial mass is at rest relative to the base of the instrument;

b) accelerometers in which, in the absence of accelerations, the inertial mass is in uniform motion relative to the base of the instrument.

1. According to the nature of the displacement of the inertial mass under the action of accelerations:

a) accelerometers with linear displacement of the inertial mass;

b) accelerometers with rotational displacement of the inertial mass (so-called “pendulum accelerometers”).

1. According to the method of suspension of the inertial mass*:

A. Accelerometers with linear displacement of the inertial mass:

a) accelerometers with free seating of the inertial mass on a guiding axis;

b) accelerometers with elastic suspension of the inertial mass (suspension on stretch elements, springs, membranes, etc.);

c) accelerometers with aerodynamic suspension of the inertial mass;

d) accelerometers with hydraulic (hydrostatic or hydrodynamic) suspension of the inertial mass;

e) accelerometers with electromagnetic suspension of the inertial mass;

f) accelerometers with electrostatic suspension of the inertial mass;

*) Item 10 of the classification applies to accelerometers with a solid inertial mass, which is used in the overwhelming majority of instruments.

g) accelerometers with a combined (from among those listed above) suspension of the inertial mass;

B. Accelerometers with rotational displacement of the inertial mass:

a) accelerometers with the inertial mass mounted on a lever having a support for rotational motion (bearings, prisms, etc.);

b) accelerometers with the inertial mass mounted on an elastic hinge;

c) accelerometers with electromagnetic suspension of the inertial mass;

d) accelerometers with hydrostatic suspension of the inertial mass (in combination with the suspensions of groups a, b, and c).

1. According to the nature of the forces balancing the action of the acceleration on the inertial mass:

a) accelerometers with balancing by forces of elastic elements;

b) accelerometers with balancing by hydrodynamic forces;

c) accelerometers with balancing by electromagnetic forces (by means of devices of the magnetoelectric or electromagnetic type);

d) accelerometers with balancing by electrostatic forces;

e) accelerometers with balancing by centrifugal forces;

f) accelerometers with balancing by gyroscopic moments;

g) accelerometers with combined (from among those listed above) balancing.

1. According to the type of displacement transducer of the inertial mass:

a) accelerometers with potentiometric-type transducers;

b) accelerometers with inductive-type transducers;

c) accelerometers with capacitive transducers;

d) accelerometers with induction transducers;

e) accelerometers with piezoelectric transducers;

f) accelerometers with optical-type transducers;

g) accelerometers with tube (electronic) displacement converters (so-called “electronic accelerometers”—[5]);

h) accelerometers with string-type transducers, etc.

1. According to the physical nature of the output quantity:

a) accelerometers with an output quantity of a mechanical nature (angular or linear displacement);

b) accelerometers with an output quantity of an electrical nature (voltage, current);

c) accelerometers with an output quantity of a temporal nature (period, frequency).

The above-listed features, according to which the classification has been made, are the principal ones in characterizing accelerometers. In our view, they give a sufficiently complete idea both of the principle of operation and of the structural design of the instrument.

REFERENCES

1. J. M. Slater. Measurement and integration of acceleration in inertial navigation, Trans. ASME, vol. 79, N 7, 1957.

2. B. P. C. Collinson. Inertial navigation of 1960, Flight, 19, Febr. 1960.

3. A. Orlacchio, D. Hieber. Trends in acceleration measurement, IRE Trans. on Instrumentation, vol. 1—6, N 2, 1957.

4. I. A. Poreshin, I. A. Shul’man, A. S. Safaryan. Inertial Navigation, Sovetskoe Radio Publ., 1962.

5. L. A. Goncharskii. Electronic accelerometers, Elektrichestvo, No. 1, 1952.