Fluidic control system and method for calibrating same

Claim 2

A fluid control system comprising; a plurality of sources of digital signals together representing in a weighted code a digital command; a fluid chamber; a source of a fluid at a constant pressure; a receiver of the fluid at a constant pressure lower than the source pressure; means for coupling the fluid from the source to the chamber; means for coupling the fluid from the chamber to the receiver; one of the coupling means comprising one or more orifices having together a fixed cross-sectional area; the other coupling means comprising a plurality of individually actuatable, digital valve elements capable of assuming a number of different states equal to the digital values that the digital signals assume, the valve elements corresponding respectively to the sources of digital signals; means responsive to the sources of digital signals for indivIdually controlling the states of the corresponding valve elements depending upon the digital values of the digital signals to produce in the chamber a pressure that is representative of the digital command; and means for sensing the pressure in the chamber.

Claim 3

The control system of claim 1, in which the sensing means comprises a movable, pressure responsive actuator and an analog valve having a flow controlling plug mechanically coupled to the actuator, the plug position being representative of the digital command.

Claim 4

The control system of claim 1, in which there is provided another chamber maintained at one of the constant pressures by the fluid source or receiver, one of the coupling means interconnects the two chambers, and the other coupling means interconnects the first named chamber to the atmosphere, which is the other constant pressure.

Claim 5

The control system of claim 1, in which there is provided another chamber maintained at one of the constant pressures by the fluid source or receiver, the digital valve elements interconnect the two chambers, and the orifice having a fixed cross-sectional area couples the first named chamber to the atmosphere, which is the other constant pressure.

Claim 6

The control system of claim 1, in which the plurality of sources of digital signals comprises a digital computer producing a plurality of binary signals together representing in a weighted binary code the digital command, the movable member comprises an actuator and an analog valve having a flow determining plug mechanically coupled to the actuator, the control system additionally comprising a fluid network in which the analog valve is disposed to control fluid flow, means for sensing the dynamic conditions of the fluid network affected by the analog valve, and means for coupling a signal representative of the sensed dynamic conditions to the digital computer to compute the digital command.

Claim 7

The control system of claim 1, in which each of the valve elements has means for adjusting the effective orifice area.

Claim 8

The control system of claim 1, in which the constant pressure of the fluid coupled by the valve elements is sufficient to create flow through each valve element at sonic velocity over the entire range of pressure produced in the chamber.

Claim 9

The control system of claim 1, in which the constant pressure of the fluid coupled by the orifice having a fixed cross section is sufficient to create flow therethrough at sonic velocity over the entire range of pressure produced in the chamber.

Claim 10

The control system of claim 1, in which flow of the fluid through the digital valve elements and the orifice having a fixed cross-sectional area is maintained at sonic velocity over the entire range of pressure produced in the chamber.

Claim 11

The control system of claim 1, in which the orifice having a fixed cross-sectional area is a tube with a mass flow rate that is a square root function of the pressure in the chamber and the digital valve elements have a mass flow rate that is a square function of the sum of their effective areas, the two functions compensating for each other.

Claim 12

A fluid control system comprising: an element that is movable responsive to pressure; a plurality of sources of binary signals together representing in a weighted binary code a digital command for positioning the movable element; a first manifold at a regulated fluid pressure; a second manifold at an unregulated fluid pressure; a plurality of individually actuatable, bistable digital valve elements interconnecting the first and second manifolds, the bistable valve elements corresponding respectively to the sources of binary signals and having effective orifice areas weighted in accordance with the binary code; means responsive to the sources for individually opening and closing the corresponding bistable valve elements depending upon the binary values of the binary signals to produce in the second manifold a fluid pressure that is representative of the sTates of the valve elements; and means responsive to the fluid pressure in the second manifold for positioning the movable element.

Claim 13

A fluid control system comprising: an element that is movable responsive to pressure; a plurality of sources of binary signals together representing in a weighted binary code a digital command for positioning the movable element; a first manifold at a regulated fluid pressure; a second manifold at an unregulated fluid pressure; a plurality of individually actuatable, bistable digital valve elements interconnecting the first and second manifolds, the bistable valve elements corresponding respectively to the sources of binary signals and having effective orifice areas weighted in accordance with the binary code; means responsive to the sources for individually opening and closing the corresponding bistable valve elements depending upon the binary values of the binary signals to produce in the second manifold a fluid pressure that is representative of the sTates of the valve elements; and means responsive to the fluid pressure in the second manifold for positioning the movable element.

Claim 14

The control system of claim 11, in which the second manifold is coupled to the atmosphere by one or more orifices having a resultant fixed cross-sectional area, the control system additionally comprising a source of fluid under pressure and a pressure regulator coupling the source to the first manifold so as to maintain the first manifold at a substantially constant fluid pressure.

Claim 15

The control system of claim 12, in which the means for positioning the movable element comprises a pressure responsive actuator mechanically coupled to the movable element and the movable element comprises the plug of an analog valve.

Claim 16

The control system of claim 13, in which the plurality of sources of binary signals comprises a digital computer having an output in the form of binary signals.

Claim 17

The control system of claim 14, additionally comprising means for sensing dynamic fluid conditions affected by the position of the plug of the analog valve and means for coupling to the digital computer a plurality of binary signals together representing in a weighted binary code digital feedback for changing the digital command represented by the binary signal output of the computer.

Claim 18

The control system of claim 15, additionally comprising a bleed orifice having a fixed cross-sectional area coupling the first and second manifolds.

Claim 19

The control system of claim 16, in which the orifice coupling the second manifold to the atmosphere is a tube, the mass flow rate through the tube being a square root function of the pressure in the second manifold, the regulated pressure in the first manifold being such that the mass flow rate through the open digital valve elements is approximately a square function of the sum of their effective orifice areas that compensates for the square root function of the tube so the pressure in the second manifold is a linear function of the sum of their effective orifice areas.

Claim 20

The control system of claim 16, in which the regulated pressure in the first manifold is such that flow through the open digital valve elements is at sonic velocity for all the combination of states of the digital valve elements.

Claim 21

The control system of claim 18, in which the flow through the orifice coupling the second manifold to the atmosphere is at sonic velocity for all the combinations of states of the digital valve elements.

Claim 22

A fluidic control system comprising: an analog valve having a plug the position of which controls the flow rate therethrough; a plurality of sources of binary signals together representing in a weighted binary code a digital command for positioning the movable element of the analog valve; a first manifold; a source of fluid under pressure; a pressure regulator coupling the source to the first manifold so the pressure of the fluid in the first manifold is constant; a second manifold; a plurality of individually actuatable, bistable digital valve elements interconnecting the first and second manifolds, the bistable valve elements corresponding respectively to the sources of binary signals and having effective orifice areas weighted in accordance with the binary code; an exhaust tube coupling the second manifold to the atmosphere, the dimensions of the exhaust tube being selected to offset the nonlinearity between the flow rate through the open digital valve elements and the sum of their effective orifice areas; means responsive to the sources for individually opening and closing the corresponding bistable valve elements depending upon the binary values of the binary signals to produce in the second manifold a fluid pressure that is representative of the states of the valve elements; and means responsive to the fluid pressure in the second manifold for positioning the plug of the analog valve.

Claim 23

A fluidic control system comprising: an analog valve having a plug the position of which controls the flow rate therethrough; a plurality of sources of binary signals together representing in a weighted binary code a digital command for positioning the movable element of the analog valve; a first manifold; a source of fluid under pressure; a pressure regulator coupling the source to the first manifold so the pressure of the fluid in the first manifold is constant; a second manifold; a plurality of individually actuatable, bistable digital valve elements interconnecting the first and second manifolds, the bistable valve elements corresponding respectively to the sources of binary signals and having effective orifice areas weighted in accordance with the binary code; an exhaust tube coupling the second manifold to the atmosphere, the dimensions of the exhaust tube being selected to offset the nonlinearity between the flow rate through the open digital valve elements and the sum of their effective orifice areas; means responsive to the sources for individually opening and closing the corresponding bistable valve elements depending upon the binary values of the binary signals to produce in the second manifold a fluid pressure that is representative of the states of the valve elements; and means responsive to the fluid pressure in the second manifold for positioning the plug of the analog valve.

Claim 24

The control system of claim 20, additionaLly comprising means for adjusting the effective orifice areas of the individual digital valve elements.

Claim 25

The control system of claim 21, additionally comprising a bleed orifice between the first and second manifolds and means for adjusting the effective orifice area of the bleed orifice.

Claim 26

The control system of claim 20, additionally comprising a bleed orifice between the first and second manifolds and means for adjusting the effective orifice area of the bleed orifice.

Claim 29

The method of claim 24, in which at least some of the valve elements have different cross-sectional orifice areas, the opening step comprising opening each valve element in the order of increasing cross-sectional orifice areas without closing any of the previously opened valve elements.

Claim 30

The method of claim 24, in which the first recited adjusting step comprises adjusting the regulator setting.

Claim 31

The method of claim 24, in which the first recited adjusting step comprises adjusting the effective orifice area of the bleed orifice.