The system, designed around a commercially available process controller, is described. The hardware design, selection of the process control equipment, the design of the interface to other systems, and the analog monitor and process control assembly used to operate the equipment from the MV-3 central computer are discussed

Sniffin, R. W.

English

NASA Technical Reports Server

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31- 3 5  . .  . .  
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Monitor and Control Equipment for the MV-3 Mobile 
Very Long Baseline Interferometry Station 
R. W. Sniffin 
Telecommuntcatioos Systems Section 
A monitor and control system for the MY-3 mobile vety long baseline interferometry 
station has been designed mund  a commercially avaihble process controller. n e  signi- 
ficant features of the hardware design and the method by which this equipment will be 
operated b-v the M"3 centrcrl computer are discussed. 
1. Introduction 
One of the goals of the MV-3 project (also known as the 
ORION project) was to utilize existing technology to the 
greatest extent possible and thereby reduce the amount of 
engneering required at JPL. An area in which i t  seemed 
probable that this god could be achieved was that of monitor 
and control where recwt advances in the field of industrial 
proces; control had pronded an aburidance of equipmenr and 
systerc; from :vhich to make a selection. By pursuing this 
approa:h. JPL engin~:z:in~ r a 5  liniited tc performing the 
high-lelrel system design, selecting the process control equip- 
men!. designing the interface to other subsystems and writing 
the software to operate the process control equipment from 
the MV-3 central computer. 
II. MV-3 Monitor and Control System Design 
There are four principal monitor and control functior. 
at the MV-3 system level. These are execution of an end- 
to-end performance test. automation of frequently recurring 
actinties. detection of failures which are not immediately 
observed by the end-to-end rest and analysis of  monitor 
data for malfunction lsolation. The first function was dele- 
gated to th ' digital tone extractor of the Phase Calibration 
Subsystem. The remaining three were delegated to the Moni- 
tor and Control Subsystem to be accomplished either within 
the subsystem or through orchestration of other subsystems 
connected t a  the MV-3 cectral computer. 
Much of the equipment selected for use in the MV-3 
station had the capability for automatic control and moni- 
toring via an RS-232C serial interface. This included the 
,.tenna servo equipment, the water vapor radiometer, the 
Maik I11 Data System and the hydrogen maser The remain- 
ing equipment was either of new design or was not available 
with built-in monitor and control capability. 
The original concept was to provide each mdjor item of 
equipment in this second category with a small data acqui- 
sition system to perform the monitor and control functions. 
These would provide a standard interface to the MV-3 centrai 
computer ~~ a Hewlett Packard 1000 System, Model 40, which 
is supplied wit! the Mark 111 Data System. The disadvantage 
of this approach was that a considerable amount of redundant 
1 
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engineering would have been needed to design suitable mech- 
anical, electrical and environmental provisions in each subsys- 
tem for the data acquisiiron equipment. The concept was 
therefore rejected in favor of a single microprocessor-based 
process controller on each transporter. Figure 1 illustrates the 
MV-3 monitor and control system, as implemented, showing 
the monitor and control interfaces as well as the end-toend 
self test siplal flow. 
111. Selecting the Process Control Equipment 
Selection of the process controllers began with a vendor 
survey to determine what capabilities were available in com- 
mercial equipment. The results were used to create a list of 
capabilities ranked by the number of vendors who could 
supply them. Discussions were then conducted with subsystem 
engineers to determine the minimum subset of capabilities 
which could fulfill all MV-3 monitor and control requirements. 
This subset, listed in Table 1. was incorporated into a spedfi- 
Miion for an “Analog Monitor and Contrd Assembly” and 
submitted for competitive procurement. 
IV. Analog Monitor end Control Assembties 
The selected analog monitor anti control assemblies at.? 
manufactured b) Analog kviccs of Norwood, MA. ur.der 
the trade name of MACSYM 20. One of their mtended ieieeli 
is to serve as the interface hetweeri a host computer ; r id tip 
to 756 assortcd analog or digital monitor or iuntri.1 pttifiv. 
In the MV-3 application. appronmately 50-peizent o l  131s 
capacity is used. 
As shown in the block diagrm, (Fig. 3). !he aAog  muti, 
tor and control assemblies are designed around an &-bit. 280 
microprocessor with 16K bytes of random-acccss read-write 
meniory (RAM) and 16K bytes of read-only memorj (RUd J. 
The micruprocessor communicates wit!! thc host compter 
via an RS-232C serial interface and is interfaced io its signal 
conditioning cards via aq analog/digital inputioutput ( ADIO) 
con:roller. This contrnlh contains all timix:g and control 
logic for addressing the i:!dividual signal conditioniilg cards 
and a 12-bit successive-approximation AID convertpi. Input 
to the AID converter is through a sample and hold amplifier, 
a programniable gain anlpiifier rind 3 16channe: multiplexer. 
This allows 3 single set of analog-to-drgi!al conversion hard- 
wart to be shared by d1 signal conditioning cards. 
In the case of andog and low-be: digital signals, the mmi- 
tor and control intaficc is by cardcdgc connectws 31 the rear 
of thc signal cond,ticniny. cards. For digital monitor awJ con- 
trol signals i n  eye, :$ uf 24 uo!ts. !he interiace is via an optical 
isolation assembly. This assembly permits connectian to 
circuits operating at 90 to 140 Vac and 10 to  60 Vdc. Selec- 
tion of Channel characteristics is made by choosing !iom 
among four module types for installation on the optical 
isolation assembly and by throwing a switch on the appro- 
priate signal conditioning card. 
Ihe firmware supplied with the malog monitor and cmmtrol 
assemblies provides the capability to interrogate or address the 
input and output channels either one at a time or in groups of 
from 2 to 16. This is done by issuing a brief command tRst 
includcs the action to be takcn and the identity uid character- 
istics of the channel or channels. The assembly also ha5 the 
capability to perform simple mathemetid operadons and 60 
store an array of parameters and command or oj~ratiam 
sequences for later execution by kseinp the sequence number. 
w. Subsystem lnterfsoss 
Wthin each svr!-,jstem, nt ;nitc; p~ii:?~. sere srleLtsd t o  
r)(?’fli;t ri,ljfucct;.xI bohtion tq r$acealIe, ;~>assemblicu. 
1.9 gee;:rd tt.2 we; nccc-~p!i-.hed by wawemwt cf s ~ t -  
w m M y  ot.t?ut< - eitner &cc*Iy !.vk;e die r,ui;ut wa; 
1 w!tzrlt) 0;‘ II<P~ i ~ .  appro!-nvte : r a r i A x e r  t c  co;isa.i 
ti;, qvmtity h e i q  m e a u t a  into a voltage, in certain 
irphcaticnz. *hen r h ~  S U ~ ~ Z S T ‘ . ~ ~  c u t p  could not bc 
cisily verified. FPrmeterP SA+ as v . ~ J :  puw,i supplv 
ciii rx:s vxie moni’.aied from which submsembly perf01 
marse cadd be in%;ed. %;ctlon Of v t i d  points was 
struprforwar;, :t.?ih !hc od$ decision lvhich needed to 
be made relathr;; Lo cunt;cl B ~ J ~ U C  i ~ i  t’le event of a mamm 
tary faiiure of ;hr monitor ard control equipment. Mere  
i t  was desiiable to k e p  a funclinn operating in the event 
of siich a failure. a tw:J-signd (.witch on. swvjtch off) con- 
trol scheine was adopted. For other cases a single signal 
was used. 
At the andog monitor and conirok assembly end. an irlter- 
face assembly w2s designtd to conneci :he twist-loch connec- 
tors on the iiltcr-subsy:!cm cabling 13 the printedcircuit card 
edge connectors requircl: by ti- signal conditioning cards and 
die screw terminals on the opticai isolation assmbly. This 
2 
wiring established the relationship between the functions being 
monitored or controlled and the physical address of that 
function. This assembly also provided a ccmvenient place to 
separate analog monitor, digital monitor and digital control 
signals arriving in one cable from each other. 
Table 2 provides a summary of MV-3 monitor and control 
points which are assessed via the analog monitor and control 
eqgipment. Included in this list are the location arm position 
and meteorological sensor data which are not monitor data 
but rather part of the station data record. As noted in the 
table, the list does not include monitor and control data 
ot:ained directly by other subsystems. 
VI. Analog Monitor and Control 
Assembly Operation 
In order to address a fuxtloral monitor or control point it 
is necessary to know the physical address in the analogmoni- 
tor and control assembly that is the card and channel number 
tq whch the function is connected. It is also necessary to 
know whether the function is a monitor or a control point, 
whether it is analog or digital, and, for analog channels, the 
sensitivity needed to make the measurement. 
Fortunately, the command structure for the analog monitor 
and control assembliss is such that this information can be 
retrieved from the palanieter array by calculating one or more 
indices into tke array. Thus a single integer number corre- 
sponding to a function can be transmitted to the analog moni- 
tor and contro! assembly followed by an instruction sequence 
number. By following the instruction sequence previously 
stored, the physical address and characteristics of the fuct ion 
can be determined and the appropriate operation performed. 
Values of monitor points are returned to the central computer 
by using additional instruction sequences. 
The process of initializing the d o g  monitor and control 
assemblies to perform these operations consists of down- 
loading two text fdes from the central computer. The first fde 
coctains command sequences whereas the second fde contains 
the d u e s  to be stored in the parameter array. The process is 
performed once when the central computer software is initial- 
ized and again if an expected response is not received. The cen- 
tral computer software is notified of a failure if no response is 
received after reinitialization. 
As data are received they are put into a common area of 
storage in the central computer. It takes between IS and 20 
seconds to completely update this area with data - the varia- 
tion being cawed by the data values themselves. This tech- 
niqw provides easy access by applicatims programs which are 
performing such activities as performance monitoring, station 
automation and malfunction isolation. 
VII. Conclusion 
A monitor and control system has been successfully desigwd 
and implemented using two industrial process controllers. Tbe 
amount of engineering effort to S U P F O ~ ~  this activity has proven 
to be in close agreement with initial estimhtes. Additional 
benefits are expected during the development of applications 
software because of the versatility of the command language 
firmware provided with these controllers. 
Biblrography 
1. Brunn, D. L., et al., “ORIOK Mobile Unit Design,” in TDA &ogress Reporr 42-60, Jet 
Propulsion Laboratory, Fasadena, Calif., Dec. IS, 1980. 
2. Sigman. E. H., and Parks, G. S., “Use of a Digital Tone Extractor for Red-Time Phase 
Ar,alysis,” in hoc. of the 1979 American Geophysical Union/NASA Conference on 
Radio Interferometry Techniques for Geodesy. 
3 
Table 1. Minlmum capability lla for MV-3 monitor urd control 
Parameter Required capability 
Analog inpu t 
Number of channels 64 
Confeuration Differentml 
Sensitivities 
Resolution 12-bit 
0 to * 10 Vdc and 0 to t ; Vd&) 
Digital input 
Number of channels so 
Logic levels supported 
Simultaneous read capability I6 channels 
TTL, 26 Vdc/O Vdc, 1 IS Vac/O Vac 
Digital output 
Number of channels 
Logic levels supported 
Physical 
Configuration 
Maximum dimensions 
Fnvironmental 
Operating tempcraturc 
Storqr. temperature 
Opera tinp JI t i  tude 
27 
1 I5 Vac V 1.8 Aac, 26 Vdc (4’ 1.8 Adc 
Rack mount with slides 
26, mm (10.5”) H x 521 mm (20.5’3 D(?) 
0 to 45’c 
-45 to 66’C 
Ser level to  3048 m (10,000 ft) 
( I )  Selected unit has wnsitivities o; +IO, t 5 .  t7.5. 21.25. ?0.625 Vdc. etc., to t4.88 mVdc 
( 2 )  Selected unit vertical dimension IS 222 m a  (8.75“) 
4 
Subsystem and assembly 
Monitor Control 
points points 
Microwave Subsystem 
Low-wise amplifiers 
Cryogenics 
Power supplies 
Miscellaneous 
Receiver Subsystem 
Down-converters 
Power supplies 
Cable stabilizer 
Comb generators 
Noi.. adding radiometer 
Power supplies 
An!enna Subsystem(') 
Locator a m  
Emergency stoplmovement warning 
Facilities Subsystem 
Power generaition 
Power distribution 
Environmental control 
Data Acqbisition Subsyted2)  
Mark 111 Dsta System 
recorders 
Distribution amplifiers 
Cesium qtandard 
Instrumentation 
Sensor data 
Power supplied 
Phase Calibration Subsystem 
Frequency and Timing Subsystem(') 
Meteorological equipmen: 
Water vapor radiomete#"' 
5 4 
6 7 
2 
3 
- 
- 
9 
6 
- 
- 
6 
2 2 
1 
8 
- 
- 
- 
9 2 
1 2 
5 
2 10 
22 
- 
- 
9 
22 
- 
- 
4 
4 
- 
- ~ . .  - .- 
NOTES. 
( I )  Momtor and control of antenna controller and sewns are by 
self-contained equipment. 
(2) Confwuration monitor and coctrol of Mark 111 Data System 
and recorders are by self-contained equipment. Listed mwitor  
points are power supply voltages. 
(3)  Monitor and control of hydrogen maser. frequency standard room 
temperature monitor and part of the frequency standard perfor 
mance monitor ar t  by self-contained equipment. 
(4) Monitor and control of water vapor raliometer is by wli- 
contained equipment. 
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Monitor and control equipment for the MV-3 mobile very long baseline interferometry station

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