Nonlinear closed loop control system to regulate the pressure in a cryogenic environment is described. System employs four position contactor with two control bands to react to the signals. Diagrams of element transfer function and required equipment are included

Goudie, L. A.

Huguley, J. C.

English

NASA Technical Reports Server

—4.12
July 1972	 B72-10390 
NASA TECH BRIEF 
Manned Spacecraft Center	
--a 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
A Closed Loop Cryogenic Environment 
Pressure Regulating System 
Figure 1. Element Transfer Function for 4-Position 
Nonlinear Contactor 
ft
The problem: 
To control pressure automatically within ±6860 N/rn2 
of a 27.4 X 104 N/rn2 absolute pressure setpoint with 
minimum overshoot and quick damping, the system must 
have stable control at low flow rates and allow transition 
from low to high flow rates with no degradation in 
transient or steady state response. Supply pressures and 
temperatures range from 27.4 X iO N/m 2 absolute to 
68.6 X 105
 N/rn2 absolute and from —1570Cto121°C. 
The solution: 
A nonlinear closed loop control system utilizes an 
electronically controlled throttle valve to achieve the 
desired pressure regulation. The electronic control (con-
troller) sets the throttle valve condition in relation to the 
pressure/flow characteristics and generates a discrete 
command signal to counteract disturbances.
How it's done: 
The nonlinear closed loop control system uses a four-
position contactor with two control bands, defined 
mathematically as follows: 
D = +2, I(s) - 0(s) >_ 4.12 X 104 N/rn2 , full undamped 
signal from pneumatic transmitter; 
D = + 1, I(s) - 0(s)> 6860 N/rn 2 , damped signal from 
pneumatic transmitter; 
D —1, I(s) - 0(s) <-6860 N/rn 2 , damped signal from 
pneumatic transmitter; and 
D =-2, I(s) - 0(s):5-4.12 X 10 N/m 2 ,full undamped 
signal from pneumatic transmitter 
where D is the output signal generated by the nonlinear 
contactor; I(s) is the input signal to the controller, i.e., 
setpoint; 0(s) is the controller variable feedback signal; 
and s is the Laplace operator, for sinusodial case s = jw. 
(continued overleaf) 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19720000389 2020-03-17T03:37:21+00:00Z
Bridge Type 
Transducer
Dump 
Valve 
Throttle 
Valve 
gu lated
60 
Actuator
Mechanical 
Linkage 
Full Open
	
'cjr Metering Solenoid 
Valve	 Lji Valve  
21 X 10 —104 X 10 N/rn 2 N2(g) 
207 X 10 N/rn 2 N2(g) 
P Control	 ressure 
Pneumatic	 Signal 
Transmitter	
i
	
gController 	 ulIuII	
Signal 
Four-Position 
Open-Close Signal Nonlinear 
Solid State 
Contactor
to 
	
When the output controlled variable, 0(s), is outside 	 Note: 
	
the ±4.12 X 10 4 N/rn2 band, as shown in Figure 1, a 	 Requests for additional documentation may be 
	
command signal of the form 1/(T 1 s + 1) with small T 1	 directed to: 
	
is desired, where T is the time constant of the transfer	 Technology Utilization Officer 
	
function. When 0(s) is within the ±4.12 X 10 4
 N/rn2	 Manned Spacecraft Center 
	
band, a command signal of the form 1/(T2 s + 1)	 Code JM7 
	
is desired with large 12 to prevent overshoot. Within the	 Houston, Texas 77058 
	
design limits of ±6860 N/rn 2 , no correction signal is	 Reference: TSP72-10390 
generated. Figure 2 shows the closed loop system.
Patent status: 
No patent action is contemplated by NASA. 
Source: J. C. Huguley and L. A. Goudie 
Brown & Root - Northrop
under contract to
Manned Spacecraft Center 
(MSC-13880) 
B72-10390	 I Category 02


A closed loop cryogenic environment pressure regulating system

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server