Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to a system for counteracting
the effect of helicopter vibrations on a seat in the
helicopter, which seat includes a plenarily of controllable
air cells. More specifically, the invention relates to
such a system wherein the effects of the vibrations are
counteracted by controllable adjusting the pressure in
the air cells to counteract the changes in pressure in
the air cells due to the vibrations.
Sustained helicopter vibration can have harmful
and injurious effects to the pilot of the helicopter and
can adversely affect the putts comfort and performance.
As eliminating or even reducing the vibrations is Defoe-
cult and possibly even impossible, the only feasible
approach to eliminating the harmful effects to the pilot
is to counteract the effect of helicopter vibrations.
The most reasonable approach is to counteract the effect
of vibrations on the pilot seat in the helicopter.
or this purpose, an "active" seat is proposed,
that is, a seat having a plurality of controllable air
cells Such seats are known in the art as illustrated in,
for example U. S. Patent 3,270,440, Radosevic, Jr.,
September 6, 1966, U. S. Patent 4,059,909, Ron,
November 29, 1977, U. S. Patent 3,983,640, Cowardly et at,
October 5, 1976, and U. S. Patent 4,164,079, Ash worth,
August 14, 197g. The above patents all relate to seats
for flight simulators, and the pressllre of the controllable
air cells is typically varied by, for example, hydraulic
actuators and bellows. However, the seats are controlled
to simulate pressures which would be felt due to the
forces of acceleration of an aircraft in a simulated
situation, and the pressures are controlled by computers
which control the pressure in the air cells and in concert
control other parameters of the flight simulators to give
the impression of an aircraft in flight.
A similar approach is used in US. Patent 3,097,43~,
Gauche, July 16, 1963 except that here the pressure of
fluid sacs which are attached to fixed walls in the simulator
are used to provide the users of the simulator with a Sims-
fated feeling of motion.
Various approaches are known in the art for is-
feting a first body, which is connected to a second body,
from the effects of vibration of the second body. One
such approach is illustrated in U. S. Patent 3,202,388.
However, as can be seen, this is an entirely mechanical
approach and would not be suitable for use in a helicopter
environment.
A further approach from isolating a first body
from a second body is illustrated in U. S. Patent 3,701,499,
Schubert et at, October 31, ].972. This patent teaches an
aircraft with an active seat, that is a seat which is adapted
to be manipulated so as to reduce the effects of vibrations
of the aircraft on the pilot sitting in the seat. However,
in this case, it is the seat itself which is isolated from
the aircraft. In fact, the pilot and the seat are considered
as a single integral unit.
Although the approach in U. S. Patent 3,701,499
yields satisfactory results, it is a difficult and expensive
approach to implement. In fact, it requires a new seat
mounting. As the position and nature of the seat mounting
is a structural effect, implementing a seat of the type
as taught in the patent requires not only a redesign of the
seat but of the entire helicopter structure. us can be
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appreciated, substantial costs are involved in implementing
this approach.
In addition, the seat in this approach remains
unchanged so that it is not possible with the teachings
of the 3l701,499 patent, to provide differential pressures
to different parts of the body of the pilot in the seat.
As will also be appreciated, it would be impossible
to use the approach of U. S. Patent 3,701,499 for the purpose
of simply retrofitting helicopters, or, more specifically,
the seats in the helicopters. As mentioned, because of
the structural effect of implementing this approach, and
not only the seat, but the entire helicopter, must be no-
designed.
It is therefore an object of the invention to
provide a system for counteracting the effect of helicopter
vibrations on a seat in the helicopter, which seat includes
a plurality of controllable air cells.
It is a more specific object of the invention to
provide such a system wherein the effects of the vibration
are counteracted by controllable adjusting the pressure in
the air cells to counteract the changes in pressure in the
air cells due to the vibrations.
In accordance with a particular embodiment of
the invention there is provided a system for counteracting
the effect of helicopter vibrations on a seat in the heft-
copter, the seat comprising a plurality of controllable
air cells. The system includes a means for fixedly connect-
in the seat to the helicopter during operation thereof and
means for varying the pressure of the cells. Vibration
transducer means sense pressure in at least one of the cells
and provide electrical signals representative thereof.
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Control means provide signals for controlling the means for
varying and processing means process the electrical signals
and provide driving signals for driving the control means.
An output of the transducer means is connected to a first
input of the processing means, and an output of the process-
in means is connected to an input of the control means.
An output of the control means is connected to the means
for varying and the means for varying is physically connected
to the controllable ax cells. Thus, the effects of heft-
copter vibrations are counteracted by counteracting the
changes of pressure in the air cells due to the vibrations
and thereby reducing or eliminating the changes in pressure
of the air cells.
The invention will be better understood by an
examination of the following description, together with the
accompanying drawing, in which:
There is illustrated in block diagram form an
embodiment of the inventive system.
Referring to the drawing, an "active" seat
comprises a plurality of controllable air cells as is well
known in the art. Disposed in the seat/ and specifically
in each air cell of the seat, is transducer means 3 for
detecting the pressure in the air cell and for providing an
electrical signal representative of this pressure Only
one transducer has been shown, however, as will be apple-
elated, it is possible to measure the pressure in more
than one, in fact each air cell so that a separate trays-
dicer can be provided for each air cell of the seat.
Means are provided for fixedly attaching the
seat to the helicopter during operation. Although adjust-
mint means may be provided for adjusting the position of the
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sea-t, it will nevertheless be fixed in position during
operation. The significance of this will be discussed
below.
The outputs of the transducers are fed to inputs
of a processing circuit 7. The processing circuit 7 could
be, for example, a controllable amplifier - inventor.
As will be seen below, the output of 7 provides a signal for
driving a control circuit. The processing circuit 7 insures
that the transducer signal is converted to its proper
polarity and amplitude for effectively driving the control
circuitry to reduce the effects of helicopter vibrations
on the helicopter seat.
The output of the processor circuit 7 is fed
to an input of system control circuit 9 whose output is, in
turn, fed to an input of servo control circuit 11. The
function of 9, in addition to that of controlling 11, will
be discussed below.
The output of the servo control system 11 is fed
to the inputs of hydraulic actuators 13, and the hydraulic
actuators, which are physically connected to bellows 15,
will, in turn, drive respective ones of bellows 15. As will
be understood, there will be a separate bellow for each
controllable air cell in the seat so that the pressure
of each air cell can be separately controlled. separate
hydraulic actuator is, in turn, connected to each respective
bellow.
Power supply 17, wick provides power for the
electronic circuits, is fed from the helicopter power pack
19 which also provides power for the hydraulic pup station
21. The system control circuit provides control through the
power pack 19 for the hydraulic pump station 21.
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In operation, the system worms as follows:
The purpose of the exercise is to maintain a
steady air pressure in all of the air cells of the helicopter
seat, that is to maintain a zero change in air pressure in
the seats. Pressure in the air cells will be varied due to
the effects of helicopter vibrations, so that the purpose
of the system is to provide signals for driving the bellows,
which signals are opposite in effect to the vibration effect
so that the net change in pressure of the air cells will
be equal to zero or will approximate zero.
A closed loop is formed by the transducers 3,
the processor 7, the control means 11, the hydraulic pump
station 21, the hydraulic actuators 13, and the bellows 15.
When the helicopter is subject to acceleration forces,
these forces will be applied to the pilot who will then
differentially effect the air cells 3 so as to change the
pressure in the air cells. This change of pressure will
be detected by respective ones of the transducers 3, and
these changes in pressure will be communicated to the
processor 7. The processor will then instruct the control
system to actuate the bellows so as to eliminate these
changes in air pressures of the respective cells.
As the seat per so remains fixed during the open-
anion, and as only the pressure in the cells is varying, it
can be seen that in the present arrangement, the pilot is
isolated from the helicopter acceleration forces. If it
was the seat itself that was moved, then obviously it would
be the seat which was being isolated from the helicopter
forces as per the teachings of I. S. Patent 3,701,499.
As above-mentioned, the performance of the '~99
patent does not differ greatly from the performance
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of the present arrangement. However, with the present
arrangement, it is possible to retrofit any existing heft-
copters by simply placing the air cells on the seat and by
installing the controlling circuitry in the helicopter.
Such a retrofit, as above-mentioned, is not possible with
the system of the '~99 patent.
In addition, as also above-mentioned, it is
possible to redesign the seat of the helicopter with the
present arrangement without redesigning the entire helicopter
structure
As it is possible that some of the cells will
be over inflated while others of the cells are under inflated
due to the action of the bellows, the processing circuit must
also include means for "averaging" the total effect on all
of the air cells on providing an appropriate driving signal.
However, in the most likely situation, all of the air cells
will be effected in the same way by the vibrations and
if this assumption can be made, then it is sufficient to
provide a single transducer 3 in, for example, a centrally
located air cell. Processing circuits for performing the
above functions are well known in the art and require no
further description.
The system control circuit 9 and the servo control
circuit 11 are also of the type well known in the art and
could, for example, be similar to systems used in simulators
wherein seats comprising a plurality of controllable air
cells are utilized as in the above-mentioned references.
however, in the present system, instead of having the control
circuits driven by an output of a computer to simulate
motion, the control circuits herein are driven by a signal
which is a function of the helicopter vibrations.
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Although a particular embodiment has been desk
cried, this was for the purpose of illustrating, but not
limiting, the invention. Various modifications, which
will come readily to the mind of one skilled in the art,
are within the scope of the invention as defined in the
appended claims.
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