U.S. patent number 3,847,348 [Application Number 05/415,693] was granted by the patent office on 1974-11-12 for roll computer.
This patent grant is currently assigned to The United States of America as represented by the Secretary of the Navy. Invention is credited to Joseph E. Russ.
United States Patent |
3,847,348 |
Russ |
November 12, 1974 |
ROLL COMPUTER
Abstract
A ship mounted stabilizer roll tank is instrumented to generate
signals icative of the tank moment. The ship is also instrumented
to generate signals indicative of its actual roll. The measured
tank moment is weighted to yield a signal indicative of the
difference between the actual stabilized roll and the estimated
unstabilized roll.
Inventors: |
Russ; Joseph E. (Spencerville,
MD) |
Assignee: |
The United States of America as
represented by the Secretary of the Navy (Washington,
DC)
|
Family
ID: |
23646781 |
Appl.
No.: |
05/415,693 |
Filed: |
November 14, 1973 |
Current U.S.
Class: |
701/124; 114/125;
701/21; 114/122 |
Current CPC
Class: |
G06G
7/70 (20130101) |
Current International
Class: |
G06G
7/00 (20060101); G06G 7/70 (20060101); G06g
007/70 () |
Field of
Search: |
;235/150.2,151.3,151.32
;318/585,588 ;73/178R ;114/121,122,125,126 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Morrison; Malcolm A.
Assistant Examiner: Smith; Jerry
Attorney, Agent or Firm: Sciascia; R. S. Hodges; Q. E.
Claims
What is claimed is:
1. A device for determining the unstabilized roll of a ship
equipped with a roll tank comprising:
first means for developing a first electrical signal proportional
to the difference between the unstabilized roll angle and the
stabilized roll angle of the ship;
second means for developing a second electrical signal proportional
to the stabilized roll angle of the ship;
third means for adding said first and second signals to produce a
third electrical signal proportional to the unstabilized roll angle
of the ship, whereby said third signal is indicative of the
effectiveness of said roll tank when compared with said second
signal.
2. The device according to claim 1 wherein:
said first means includes a plurality of pressure sensors mounted
at various locations on said roll tank for producing pressure
representative electrical signals.
3. The device according to claim 2 wherein said first means
includes a first adder (44) connected to said pressure sensors,
said first adder including an output, whereby the signal at the
output of said first adder is representative of the instantaneous
roll tank moment.
4. The device according to claim 3 wherein said first means
includes a second adder connected to the output of said first adder
said second adder including a second output;
first and second series connected integrators connected to said
second output, each said integrator including an integrator output,
whereby said first electrical signal is present at said output of
said second integrator.
5. The device of claim 4 wherein said first means includes feedback
means connecting each said integrator output to an input of said
second adder.
6. The device of claim 1 further including selectively actuable
test means for supplying voltage signals to said first means
whereby said first means may selectively be tested for proper
operation.
Description
The invention described herein may be manufactured and used by or
for the Government of the United States of America for Governmental
purposes without the payment of any royalties thereon or
therefore.
BACKGROUND OF THE INVENTION
This invention generally relates to ships equipped with passive
roll tanks. A roll tank is a fluid filled tank mounted in a ship
and used to prevent undesired oscillations of the ship due to wave
excitation. As the ship rolls, the fluid in the tank shifts in the
direction of the roll and, in effect, changes the center of gravity
of the ship thereby inhibiting the tendency of the ship to
oscillate. The term passive is used herein to denote that type of
tank in which the amount of fluid is held constant as opposed to
other types of roll tanks in which the fluid level is changed as by
pumping in response to signals from other shipboard systems as
disclosed in prior art devices. The present invention is designed
to test the efficiency of passive roll tanks while mounted on the
ship under test. No such prior art device is believed to exist.
SUMMARY OF THE INVENTION
This invention relates to a device for determining the unstabilized
roll of a ship equipped with a passive roll tank. Signals
indicative of the stabilizer roll tank moment are generated by
instruments mounted on the stabilizer roll tank. Another signal
indicative of the actual roll of the ship is generated. The
measured tank moment is then utilized to generate a signal which is
indicative of the difference between the actual stabilized roll and
the estimated unstabilized roll. The difference signal is then
added with the actual roll signal to produce a signal indicative of
the unstabilized roll of the ship.
OBJECTS OF THE INVENTION
The object of this invention is to provide a device for estimating
the unstabilized roll of a ship which is equipped with a passive
roll tank.
Another object of this invention is to avoid the necessity of
making separate tests of the oscillatory behavior of a ship before
and after the passive roll tank is mounted.
Other objects, advantages and novel features of the invention will
become apparent from the following detailed description of the
invention when considered in conjunction with the accompanying
drawings wherein:
BRIEF DESCRIPTION OF THE DRAWINGS
The sole FIGURE is a detailed network diagram of the preferred
embodiment of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Generally, when a ship is unstabilized, i.e., not outfitted with a
roll tank stabilizer
A.theta..sub.U + B.theta..sub.U + C.theta..sub.U .congruent. F(T)
(1)
where a, b, and c are constants of proportionality, f(t) is the
roll moment of the ship due to wave excitation and .theta..sub.u is
the unstabilized roll angle of the ship. When the ship is
stabilized
A.theta..sub.S + B1/4 .sub.S + C.theta..sub.S .congruent. F(T) +
G(T) (2)
where g(t) is the moment developed by the stabilizer tank and
.theta..sub.s is defined as the stabilized roll angle. By
definition herein
.theta..sub.d = .theta..sub.u - .theta..sub.s (3)
or
.theta..sub.u = .theta..sub.s + .theta..sub.d . (4)
.theta..sub.d, therefore, represents the difference between the
unstabilized roll angle and the stabilized roll angle. It follows
from substitution of equation (4) into equation (1) that
a(.theta..sub.s + .theta..sub.d) + b(.theta..sub.s + .theta..sub.d)
+ c(.theta..sub.s + .theta..sub.d) .congruent. f(t). (5)
Since the derivative of a sum is equal to the sum of the
derivatives, it follows that
a.theta..sub.s + a.theta..sub.d + b.theta..sub.s + b.theta..sub.d +
c.theta..sub.s + c.theta..sub.d .congruent. f(t) (6)
Substracting equation (2) from equation (6), gives
a.theta..sub.d + b.theta..sub.d + c.theta..sub.d .congruent. -
g(t). (7)
It is thus seen that .theta..sub.d is a function of the moment
developed by the stabilizer tank.
In the drawing, P.sub.1, P.sub.2, P.sub.3, P.sub.4, P.sub.5, and
P.sub.6 each represent a pressure transducer mounted on the roll
stabilizer tank and an amplifier to amplify the transducer signal
output. The transducers are mounted at various locations on the
stabilizer tank depending on the particular stabilizer tank
configuration. A,B,C,D,E,F,G,H, and I denote potentiometers
utilized at various locations in the roll computer to properly
scale the signals passing therethrough. 24,26,28,30,31,32, and 8
are inverter amplifiers for inverting signals at their inputs to
provide the proper polarity signal at their outputs. 25,27,29,44,2,
and 9 are adders. 6 and 7 are inverter integrating networks. SR
denotes a unit for measuring the stabilized roll of the ship and
for providing an electrical signal proportional to the stabilized
roll angle .theta..sub.s. SR may be a gyroscope or an inclinometer
with a potentiometer.
The signals developed by pressure transducers P.sub.1 -P.sub.6 and
units 24-32 are supplied as inputs to adder 44 such that the output
of adder 44 is representative of the total roll tank moment g(t).
The instant invention provides for sensing of the fluid pressure
within the roll tank at six locations by the pressure transducers
P.sub.1 -P.sub.6 shown in the drawing, the locations of the
transducers being dependent upon the particular roll tank
configuration. Inverter-amplifier 24 inverts the pressure
indicative signal from transducer-amplifier P.sub.6 so that the
output of adder 25 is a measure of the difference between the
pressures sensed by units P.sub.1 and P.sub.6. Likewise the outputs
of adders 27 and 29 are measures of the pressure differences sensed
by transducers P.sub.2 and P.sub.5 and P.sub.3 and P.sub.4
respectively. Potentiometer C scales the pressure difference output
of adder 25 and, thereby, produces a first contribution to the
total tank moment. Similarly, potentiometers D and E scale the
pressure difference outputs of adders 27 and 29, respectively,
thereby producing second and third contributions to the total tank
moment. These tank moment contributions are inverted by inverters
30, 31 and 32 to provide the proper sign and are then summed by
adder 44. The output of 44 is, therefore, representive of the total
stabilizer tank moment, g(t). Solving equation (7) for the second
order derivative, .theta..sub.d, yields
.theta..sub.d = - g(t)/a - b/a.theta..sub.d - c/a.theta..sub.d
(8)
The purpose of adder 2 is to synthesize the right hand side of
equation (8). The output of adder 44 supplies the first input,
g(t), to adder 2. The second input to adder 2 is supplied by a
first feed back loop from the output of inverter integrator 6 since
the output of 6 is proportional to the quantity .theta..sub.d. The
third input to adder 2 is supplied by a second feedback loop from
the output of inverter integrator 7 since the output of 7 is
proportional to .theta..sub.d. Thus, each of the three quantities
in the right hand side of equation (8) is present as one of the
inputs to adder 2. Inverter integrators 6 and 7 then perform a
double integration of the output from adder 2. The output of 7,
therefore, is representative of .theta..sub.d, the difference
between the unstabilized roll angle and the stabilized roll angle.
Adder 9 adds to this signal the signal .theta..sub.s, the
stabilized roll angle. Thus, as seen in equation (4), the output of
adder 9 is .theta..sub.u. This unstabilized roll angle signal,
.theta..sub.u, and .theta..sub.s are detected by some type of
recording instruments, 100, which may take the form of a strip
chart recorder, a tape recorder, a dial gauge, or any other form of
suitable display means. .theta..sub.u may then be compared with
.theta..sub.s to determine the effectiveness of the roll tank.
Static testing of the roll computer may also be performed by means
of the test network provided. The test network comprises the
voltage supplies +V and -V, potentiometers H and I, inverter
amplifiers 4,5,16 and 17, and selectively actuable test switches S1
and S2. Switches S2 may be either ganged or independently operable.
Opening of normally closed test switch S1 removes the shunt across
the voltage supply, +V, whereby inverter amplifiers 16 and 17 are
energized to supply test signals to inverter integrators 6 and 7.
Similarly, closure of normally opened test switches S2 permits the
voltage supplies +V and -V to energize the units 24-32 and,
thereby, adder 44. Thus, the output of each of the units comprising
the roll computer may be checked statically.
Thus, a roll computer has been disclosed for developing a signal
which is an estimate of the unstabilized roll of a ship equipped
with a stabilizer roll tank.
Obviously many modifications and variations of the present
invention are possible in light of the above teachings. It is,
therefore, to be understood that within the scope of the appended
claims the invention may be practiced otherwise than as
specifically described.
* * * * *