Surgery – Antigravational systems
Reexamination Certificate
1999-02-26
2001-04-17
Michalsky, Gerald A. (Department: 3753)
Surgery
Antigravational systems
C137S014000, C137S102000, C137S487500
Reexamination Certificate
active
06217506
ABSTRACT:
BACKGROUND TO THE INVENTION
This invention relates to a method of controlling a fluid in a life support system including at least one of a G-suit and a counterpressure garment e.g. for a member of an aircrew of a high performance aircraft.
Description of the Prior Art
It is common practice in a control system to sense the effect of operating a control effector such as a valve, in order to use feedback, so that the control effector may dynamically be adjusted in order that the actual parameter being controlled e.g. fluid pressure or flow, may be brought to a desired value. Thus control of the parameter is achieved purely in response to the effect of operating the effector. Such control is insufficiently refined for many applications and there is the possibility of the actual parameter being controlled not remaining within acceptable limits.
It is also known to measure e.g. using a transducer, the position of a moveable part of a valve, such as a valve stem, in response to a control input, to monitor and control the valve operation incrementally in response to a control signal, in an effort to keep the actual parameter being controlled within acceptable limits. However physically measuring position and making the necessary calculations is too slow for application to a high performance life support system.
SUMMARY OF THE INVENTION
According to a first aspect of the invention we provide a method of controlling a fluid in a life support system including at least one of a G-suit and a counterpressure garment, the method utilising a control system including a control valve means and there being means to provide an input to the control system to cause an actuator to move a moveable part of the valve means to operate the valve means to bring a parameter of the fluid towards a desired value, and means to condition the input to provide a control signal to cause the actuator to move the moveable part of the valve means characterised in that the method comprises conditioning the input by comparing the input with reference information relating to the position of the moveable part of the valve means, and when the comparison indicates that the position of the moveable part of the valve means is not at a desired position, issuing the control signal incrementally to move the moveable part and updating the reference information so that the updated reference information is available for future comparison with the input.
Thus the input to the control system may be modified to provide the control signal without having to determine the physical condition, e.g. actual position of a moveable part, of the valve means. Rather, the input may be modified with reference to a model of the valve means, which modification can thus be achieved much faster than in a physically dependant system, for optimum dynamic behaviour.
The input may comprise a signal derived from a comparison between an instructing signal and a feedback signal, the feedback signal containing information concerning the actual value of the parameter and the instructing signal depending upon a parameter value it is desired to attain. Thus the control system may incorporate a feedback arrangement as in conventional control systems although the sensitivity of the control system will not solely be dependant upon the feedback signal.
The reference information may comprise a model which models the physical response of the moveable part of the valve means to the control signal based upon known valve means characteristics so that when the reference information is updated the updated reference information is indicative of actual valve means moveable part position.
The model may be made as complex as desired to mimic the physical response of the valve means to the control signal. In its simplest form, the model may be a simple counter which counts incremental movements of the moveable part of the valve means in response to control signals, so that the count is indicative of the moveable part position.
The method may further comprise not providing the control signal to the actuator in the event that the comparison between the reference information and the input indicates that the moveable part is less than a predetermined distance from the desired position. In this way, operation of the valve which would achieve no meaningful control can be avoided and unnecessary valve activity can be reduced or prevented altogether.
In one arrangement the actuator is a stepper motor, the method comprising applying the control signal to drive the stepper motor to move a moveable part of the valve means a predetermined number of steps, e.g. one step.
The method may be repeated a sufficient number of times to move the moveable part of the valve means incrementally until the moveable part of the valve is at or substantially at a desired position.
According to a second aspect of the invention we provide a control system controlling a fluid in a life support system including at least one of a G-suit and a counterpressure garment, the control system including a control valve means which when operated changes a parameter of the fluid in the system, and a conditioning means to condition an input provided to the system to operate an actuator of the valve means, the conditioning means being adapted to condition the input by comparing the input with reference information relating to the position of the moveable part of the valve means and when the comparison indicates that the position of the moveable part of the valve means is not at a desired position, the conditioning means issuing the control signal incrementally to move the moveable part whilst updating the reference information so that the updated reference information is available for future comparison with the input.
A so called G-suit of a life support system, is an inflatable garment worn about at least the lower part of the body to prevent pooling of blood in the lower part of the body during aircraft manoeuvres which subject the aircrew member to high G forces. The life support system typically also includes means to provide the aircrew member with breathable gas, including an upper body inflatable garment (known as a counterpressure garment) to aid breathing, breathable gas being provided at an appropriate positive pressure for a given altitude, which pressure is most beneficially related to the pressure of the upper body inflatable counterpressure garment.
Conventionally such a life support system has been controlled so that there is a fixed relationship e.g. pressure ratio, between the pressures applied to the upper and lower body inflatable garments in a high altitude environment. This is because of the complexity of controlling these two parameters independently, usually by pneumatic means, particularly as the desired parameter values can rapidly change.
By virtue of the method of the first aspect and the control system of the second aspect of the invention, the pressures in the upper and lower body inflatable garments can independently be controlled as the system is inherently more flexible and adaptable than existing control systems.
According to a third aspect of the invention we provide a life support system for a pilot of an aircraft comprising at least one of a G-suit and a breathing system including a counterpressure garment, a control system according to the second aspect of the invention responsive to an input to control the pressure in the G-suit and/or breathing system.
The method of controlling the control system may be as the first aspect of the invention.
REFERENCES:
patent: 3779280 (1973-12-01), Evans et al.
patent: 4566868 (1986-01-01), Menzies
patent: 4797834 (1989-01-01), Honganen et al.
patent: 5522416 (1996-06-01), Farrell et al.
patent: 0 540 079 A1 (1993-05-01), None
patent: 2 192 737 (1988-01-01), None
patent: WO 96/10779 (1996-04-01), None
Phillips Robert John
Stuckey Christopher John
Marshall O'Toole Gerstein Murray & Borun
Michalsky Gerald A.
Normalair-Garrett (Holdings) Limited
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