Rotational acceleration detector with microdot coding

A system for detecting angular, radial and axial accelerations of rotating machinery parts to facilitate vibrational analysis of the parts. An annular array of micro dots is disposed on the rotating machinery part generally concentric with the axis of rotation of the part. A stationary high resolution photodetector is located for reading the micro dot patterns of movement of the annular array of dots as the array tangentially passes the photodetector. A conditioning circuit is coupled to the detector for conditioning a signal received from the detector.

FIELD OF THE INVENTION 
This invention is directed to a rotational acceleration system to detect 
the motion of a micro dot array attached to a rotating device. 
BACKGROUND OF THE INVENTION 
The development of quiet rotating machinery is extremely difficult because 
the static measurement of fabrication accuracy does not always correlate 
to how quiet or noisy a component will be during operation. Noise usually 
is created in rotating parts of machinery when the parts are not balanced 
and do not rotate about their intended axis of rotation or about their 
center of mass. 
Vibrational analysis of a machine and/or its rotating parts in operation 
does not always pinpoint imbalance problems. General vibrational data can 
be made available to generally locate design or fabrication problems, 
somewhat similar to known vehicular tire balancing appartus. However, 
attempts at analyzing detailed motion of rotating parts of machinery is 
rarely attempted. Consequently, expensive high tolerance parts often are 
substituted where they might not actually be required if detailed motion 
of the rotating parts could pinpoint the design or fabrication problems. 
There is a need for a device or system to facilitate the analysis of and/or 
measuring of angular, radial and axial accelerations of a rotating body 
that would have the capability of detecting high frequency motions caused 
by gear, bearing and balance problems. 
This invention is directed to satisfying such a need and solving the 
above-identified problems in rotating machinery. 
SUMMARY OF THE INVENTION 
An object, therefore, of the invention is to provide a system for detecting 
angular, radial and axial accelerations of rotating machinery parts and 
the like to facilitate vibrational analysis of the parts. 
Generally, the invention contemplates providing an annular array of micro 
dots on the rotating machinery part generally concentric with the axis of 
rotation thereof. A stationary high resolution photodetector is located 
for reading the micro dot patterns of movement of the annular array as the 
array tangentially passes the photodetector. Conditioning means are 
provided for conditioning a signal received from the photodetector. 
The invention also contemplates the disposition of the micro dots on a 
separate strip, as by laser etching the array of dots in a high density 
pattern on the strip. The strip then can be placed at various locations on 
various shaped machinery parts. For instance, the strip may be wrapped 
around the outer surface of a cylindrically-shaped rotating part, such as 
a shaft. The strip may be placed in a circular array on an axial face of a 
disc-shaped rotating part, such as a gear. The annular array of micro dots 
may be laser-etched directly on the surface of the rotating part itself. 
The conditioning means include amplification means and a pulse 
discriminator. 
Other objects, features and advantages of the invention will be apparent 
from the following detailed description taken in connection with the 
accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawings in greater detail, and first to FIG. 1, the 
invention is directed to a rotational acceleration detecting system for 
detecting angular, radial and axial accelerations of rotating machinery 
parts, such as a machinery part, generally designated 10, in order to 
facilitate vibrational analysis of the rotating part. The machinery part 
may comprise a variety of components, such as gears, bearings, shafts, 
turbines or the like. As for example, FIG. 1 shows a shaft 12 for rotating 
a component 14. Component 14 may be a gear, a turbine, a larger diameter 
shaft, or a variety of other machinery parts. 
The invention contemplates disposing an annular array 16a,16b of high 
density micro dots on the machinery part, the array to be read by a high 
resolution photodetector 18a,18b. FIG. 1 is a somewhat schematic 
illustration and the showing of two micro dot arrays 16a and 16b along 
with their respective photodetectors 18a and 18b is somewhat redundant The 
depiction is for illustration purposes to show the application of the 
invention on various types of machinery parts. 
Specifically, micro dot array 16a is shown as a band about the outer 
diameter surface of cylindrically shaped shaft 12. Micro dot array 16b is 
shown in a circular array as disposed on a flat face 20 of a gear, for 
instance. In either event, the arrays are intended to be concentric about 
the axis of rotation 22 of the machinery part 
Furthermore, the invention contemplates the disposition of the dot patterns 
on a strip, such as a plastic film, which can be attached to the rotating 
part. The dot patterns may be generated by a laser beam on the plastic 
film and then attached to the rotating part at appropriate locations, as 
described in relation to arrays 16a wrapped about shaft 12 and 16b on the 
face of gear 20. The dot patterns also may be generated by a laser beam 
directly onto a properly prepared surface of the rotating part itself 
Photodetectors 18a,18b are high resolution, micro-chip photodetectors which 
are located such that the respective micro dot patterns pass the head 24 
of the photodetector in a tangential direction. The photodetectors are 
stationary and read the micro dot patterns of movement of the array of 
micro dots 16a,16b as the array tangentially passes the detector during 
rotation of the parts. The detector(s) generates an electronic signal, as 
at 26 (FIG. 1). 
In essence, photodetectors 18a,18b sense or detect minute variations from 
the mean angular velocity of the micro dot patterns tangentially passing 
the detector In other words, axial, radial and angular variances can be 
detected and the microchips accordingly generate electronic signals as the 
detector(s) tracks the movement of the micro dot patterns in relation to a 
mean parameter. 
FIG. 2 shows one type of conditioning means for conditioning signal 26 from 
one of the microdetectors 18a, 18b. The conditioning means include an 
amplifier 30 coupled to a pulse discriminator 32 which, in turn, is 
coupled to a phase-locked loop 34. The phase-locked loop includes a loop 
error circuit 35 whereupon the signal is fed to a second amplifier 36. The 
result is that signal 26' coming from the photodetector is conditioned 
through the circuit as indicated graphically at 38a,38b,38c,38d as the 
signal is conditioned through the circuit to a usable mode indicating 
acceleration. This signal then can be measured and/or compared to a mean 
signal to determine appropriate variances or imbalances. Speed and 
acceleration can be measured by digital signal counting, i.e. as the dots 
pass the detector. 
It will be understood that the invention may be embodied in other specific 
forms without departing from the spirit or central characteristics 
thereof. The present examples and embodiments, therefore, are to be 
considered in all respects as illustrative and not restrictive, and the 
invention is not to be limited to the details given herein.