The Rapid Prototyping Facility (RPF) was developed to meet a need for a facility which allows flight systems concepts to be prototyped in a manner which allows for real-time flight test experience with a prototype system. This need was focused during the development and demonstration of the expert system flight status monitor (ESFSM). The ESFSM was a prototype system developed on a LISP machine, but lack of a method for progressive testing and problem identification led to an impractical system. The RPF concept was developed, and the ATMS designed to exercise its capabilities. The ATMS Phase 1 demonstration provided a practical vehicle for testing the RPF, as well as a useful tool. ATMS Phase 2 development continues. A dedicated F-18 is expected to be assigned for facility use in late 1988, with RAV modifications. A knowledge-based autopilot is being developed using the RPF. This is a system which provides elementary autopilot functions and is intended as a vehicle for testing expert system verification and validation methods. An expert system propulsion monitor is being prototyped. This system provides real-time assistance to an engineer monitoring a propulsion system during a flight

Brumbaugh, Randal W.

Duke, Eugene L.

English

NASA Technical Reports Server

ReabTime Application of Knowledge-Based 
Systems 
Randal W. Brumbaugh 
PRC System Services 
Aerospace Technologies Division 
Eugene L. Duke 
NASA Ames Research Center 
Dryden Flight Research Facility 
Edwards, California 
PRECEDING PAGE BLANN NOT FILMED 
357 
https://ntrs.nasa.gov/search.jsp?R=19890015792 2020-03-20T01:33:06+00:00Z
The Rapid Prototyping Facility (RPF): A Real-Time Application of Knowledge-Based Systems. 
At the Drydcn Flight Research Facility of thc NASA Amcs Rcscarch Ccntcr, 
the Aircraft  Automation Group is cngagcd in rcscarch airncd at  applying 
expcrt  systcms technology in a real-time flight tcst environmcnt .  NASA and 
PRC rcscarchers have developed a facility which a l lows  an cxpcrt  system 
prototype to  be rapidly and safely demons t r a t ed  wi th  a tcst a i rc raf t .  
A p p l i c a t i o n s  range from monitoring and d isp lays  to outer  loop  aircraf t  
c o n t r o l .  
This  presenta t ion  is intended to document  the faci l i ty  deve lopment  and 
archi tecture ,  demonstrate  i ts  utility by presenting a typical application, and 
detail  recent accomplishments and future goals. 
358 
Rapid Prototyping Facility: Concept 
Simulation 
facility 
The development of a knowledge- based or cxpcrt system generally includes an 
early implcmentation of a prototype system. This prototype system providcs a 
means of assessing concept feasibility, examining knowledge represcntation 
and inference strategies and provides a demonstration to gain support for a 
larger, more complete program. 
The value of prototyping the major components of a knowledge - based system 
early in the development cycle is that many problems or potential problems 
can be discovered. Addressing these problems at an early stage is generally 
less costly and time-consuming than later modification. 
The facility discussed here provides a flexible, general-purpose capability for 
prototyping flight systems which contain a combination of knowledge-based 
and algorithmic components. The user has a wide choice of processors, tools 
and resources, including the Ames-Dryden real-time simulation facility and 
research aircraft, through the Remotely Augmented Vehicle (RAV) system. 
* 
A developer with a concept for a knowledge-based flight system may select 
resources and distribute applications to rapidly develop a prototype system. 
The facility then allows easy transition to simulation verification and 
validation, and possible flight test of the concept. 
Flight research 
359 
Components :  T h e  Remotely Augmented Vehicle (RAV) System 
The rapid prototyping facility is an extension of the Amcs-Drydcn RAV syslcm 
capability. The main elcmcnts of this facility, shown in thc figure, arc 
1. A specially modified aircraft 
2. An auxiliary computational facility 
3. A high fidelity simulator 
Each element serves a unique function in providing a path for rapid system 
transition from simulation to flight. It is this transition capability that 
provides the power of the facility to a prototype system developer. 
The aircraft used requires two main modifications. The first is the addition of 
sensors and a high quality instrumentation and telemetry downlink system. 
The second is the integration of a telemetry uplink system into the onboard 
systems, Uplinked data may be routed to the flight control system for closed 
loop control, or to an onboard display system if displays are desired. Once so 
configured, the aircraft requires no further modifications; changes are 
performed by altering the auxiliary computational facility. 
Range, evaluation //- Telemetry 
azimuth \ uplink 
downlink 
Ground- based 
auxiliary 
computational 
facility 
Simulation Simulation 
Simulation 
facility 
Specially modified aircraft 
Simulation facility 
Auxiliary computational facility 
- Numeric and symbolic processors 
-Duptication of flight systems in 
simulation facility 
360 
Components :  T h e  Remotely Augmented Vehicle (RAV) System 
When the telemetry links are operating, the aircraft systems essentially 
become a node in a distributed processing system which includes a suite of 
ground based computational facilities. These may include systems for 
handling TM links, for displaying, recording, or  processing data in real-time, 
o r  for performing specialized tasks such as knowledge - based control or  
monitoring. This allows processors which cannot be physically located 
onboard the vehicle due to limitations in space, ruggedization or  cooling, to act 
nearly identically to an onboard computer. 
As an alternative to the flight system, the aircraft may be replaced by the 
simulation system. The simulation facility provides modelling of the aircraft 
so that systems may be verified prior to flight operation. It is a key feature, 
and a requirement for safety, that the interface between the simulation and 
the actual aircraft TM links be identical. In this way, a concept tested in the 
simulator is provided a path to flight test experience (see previous figure). 
361 
How Fast is "Real Time" ? 
Any systcm which must providc a rcsponsc in a givcn t imc  intcrval can bc 
said to be a "real-time" system. Thc lcngth of thc timc interval varics greatly, 
depcnding on the systcm and application. I t  may even differ bctwecn 
components of a singlc system. A display proccssor will typically havc a 
slower response criterion than an aircraft flight control system, although 
both are parts of a larger systcm. Some systcms also have requirements such 
as a constant frame time, or connection to a regular clock interrupt. 
The rapid prototyping facility provides for real-time response at  several 
levels. Interactive systems must provide response at human speeds. Typically 
this applies to editors, compilers, and display systems. Outer-loop systems 
provide control of system state trajectory, and inner-loop systems are required 
for system stability. A trajectory guidance controller is an example of outer- 
loop control; a flight control system provides inner-loop functions. 
The final measure of a real-time system is that it respond "in-time." The 
developer using the RPF chooses from computing resources and tools with 
different capabilities. Efficient distribution of  processing is key to meeting 
response time specifications, but redistribution of processes is not difficult. 
Real-Time Applications Within Rapid= Prototyping 
Facility 
What does real=time mean? 
Interactive 
Outer-loop systems 
- Response at human speeds (1.0-0.1 Hz) 
- Response required to control system trajectory 
(25-1 Hz for aerospace systems) 
Inner4oop systems 
- Response required to stabilize dynamic system 
(1000-25Hz for aerospace systems) 
ln-time 
- Response provided in time required 
Goals for rapid-prototyping facility 
ln-time responses for tasks up to 25Hz 
36 2 
F l e x i b i l i t y  t h r o u g h  S t a n d a r d i z a t i o n  
The wide sclcction and flcxibility of thc rcsourccs available in thc RPF is a 
rcsult of the use of standard intcrfaccs which arc widcly recognized and 
supported by nearly ail manufacturers. Expanding or  altering the nctwork of 
computers is a quick and simple procedure. The use of standards also providcs 
access to the resources available to uscrs of the central facility computers, 
which contain a variety of printers, plotters and disk storage devices. 
The computers are linked through a network based on a thick Ethernet/IEEE 
802.3 cable. The DOD standard TCP/IP protocol is used throughout for 
communication. Standard utilities for virtual terminal emulation (telnet) and 
fi le transfer (ftp) are available to users during development. Executing 
processes transfer data in single precision IEEE 754 floating point format. 
Many processors support  this format directly; others require a simple 
conversion routine to change the data to their local floating point format. 
Communication Standards in AI-Lab 
Process layer ----------- I User data 
buffers 
I IP 
I Network 
I IEEE 802 
ANSlllEEE Standard 7454985 
IEEE Standard for Binary Floating Point 
Arithmetic 
Transmission Control Protocol MIL=STD=I 778 
Connection Oriented Transport Control 
Specification 
Internet Protocol MIL=STD=1777 
Protocol for Providing the Connectionless 
Mode Network Service 
IEEE 802.2 Logical Link Control 
IEEE 802.3 CSMAlCD Media Access 
Control Protocol for Bus Topology 
363 
C u r r e n t  A r c h i t e c t u r e  
The computcr systcms in thc RPF arc dividcd into two groups. Thc first is the 
computcr systcms of thc Aircraft Automation group; the othcr is the systems of 
the Ames-Dryden Simulation/ RAV facility. 
T h e  s imulat ion/RAV computers are  shown on  the right s ide of the figure. 
These  are  very high speed FORTRAN processors.  The  systems shown are 
typical. T h e  facility contains several systems used for development,  simulation 
and RAV. Each system contains two computers connected by a high-speed 
shared memory link. These systems provide simulation, cockpit interfaces and 
displays,  connection to hardware-in-the-loop simulation components  and RAV 
l i n k a g e .  
T h e  majority of  the remaining computers  are  general  purpose U N I X -  based 
workstations with high resolution graphics interfaces. These provide general  
purpose computing and development resources. Several  languages and tools 
are available to users including C, FORTRAN and CLIPS. 
The  VAX 11/750 is used primarily for its disk storage and tape facilities. It also 
hosts several  tools for expert  system development including C, FORTRAN,  
Common LISP, OPS5 and CLIPS. 
T h e  TI Explorer  LX is a multi-processor system designed for applications 
requiring close integration of symbolic and numeric computing, T h e  primary 
processor is a symbolic processing architecture with LISP, ART and a graphics 
interface. It communicates through shared memory o r  data  s t reams with a 
conven t iona l  processor running  appl ica t ions  unde r  t h e  U N I X  ope ra t ing  
s y s t e m .  
Bridge to outside world 
EthernetllEEE 802.3 net I--+ 
piil 
11 /750 
I 
[MASSCOM P I 
5400 
1
Shared 
memory 
SEL SEL 
1 2 7 1  1 2 7 1  uu
Shared 
memory 
Telemetry 
link 
I 364 
An Applicat ion:  T h e  Automated Fl ight  T e s t  Management  System 
( A T M S )  
The ATMS system, developed by Sparta, Inc., is designed as thc premier 
application for the rapid prototyping facility. This system demonstrates many 
of the capabilities of the RPF for use in planning, monitoring and control 
tasks involving several cooperating resources. It includes expert systems, 
numerical algorithms, graphics, simulation, control, monitoring and use of 
RAV capability. 
The ATMS aids engineers in a flight test environment by using expert system 
technology to optimize flight maneuver lists to fit time and range constraints. 
It is designed to aid both in pre-flight planning and in in-flight execution and 
monitoring. It  is designed to benefit flight test engineers, researchers and 
pilots so that the best data possible is obtained at minimum cost and time. 
Flight test planning 
- Program planning 
- Block planning 
- Preflight planning 
Flight test trajectory control 
Flight test maneuver monitor 
In-flight re-planner 
365 
ATMS: Final System 
The final ATMS system implementation will provide f u l l  flight planning, 
monitoring and control capabilities. The system USCS knowledge of a flight 
project's goals, priorities and needs to formulate a plan for blocks of flights, 
individual flights, and finally chooses lists of maneuvers for each flight. The 
maneuvers for a specific flight are ordered to optimize use of available time. 
range, space and fuel. 
After the FTE and system have defined a flight card containing an ordered list 
of maneuvers to be performed during the flight, the flight can be simulated 
either with a 3 degree-of-freedom simulation, or  a more correct 6 degree-of- 
freedom simulation. 
During the flight, the selected maneuvers can be flown by a research pilot or 
by a flight test trajectory controller through the RAV link. As each maneuver 
is performed, the monitor function checks data to be sure that i t  is of 
acceptable quality for research requirements. It also monitors constraints 
such as range boundaries and restrictions and aircraft structural limits to be 
sure they are not violated. 
If a maneuver is  stopped or unacceptable, the ATMS recommends a course of 
action: drop the maneuver, repeat it, or  reschedule during a subsequent flight. 
Based on interaction with the FTE, a new plan can then be formulated in- 
f l i g h t .  
Preflight planning 
functions 
Block 
planning 
Preflight 
In-flight monitoring, controlling, 
and replanning functions - 
I I 
I A 
Monitor 3 or 6 DOF simulation 
or aircraft 
366 
ATMS: Current Functions 
* Preflight planning . 
The current ATMS system (Phasc I )  implements a carcfully sclcctcd subsct of 
the final system design. The parts selected for implementation are designed to 
demonstrate distribution of processing, real-timc control in a simulation 
environment, and limited planning and monitoring capability.  This  system 
was presented in a demonstration in June, 1988..  
Controller 
Pref I ig ht 
planning 
functions In-flight monitoring, controlling, 
and replanning functions 
Monitor 3 or 6 DOF simulation 
367 
ATMS: Workstation Configuration 
Experf sysfem Tralecfory 
r M-M interfaces \ r m a n a g e r  \ f 
Man- 
Expert systems machine checker 
Interface 
The following thrcc figures depict thrcc diffcrcnt configurations of the ATMS, 
showing how tasks are distributcd among the proccssors. The configurations 
progress from planning to validation to flight test. 
- 3 . 0  Planner -I Dlsplays 
Interface 
software 
Monltor 
- n - 
LISP processor 
The first shows how tasks are partitioned for the flight test engineer 
workstation. This system allows the FTE to enter maneuvers, simulate 
maneuvers to estimate time, space and fuel used, and suggests an order for 
flight. The simulations are performed in a local workstation rather than the 
simulation facility to avoid scheduling time on the simulation computers until  
a more refined flight plan has been constructed. 
I I 
Flight test trajectory 
controller 
generator 
MASSCOMP 5400 I 
368 
ATMS: Flight Configuration 
Once satisfied that the flight card is acccptablc. the flight is conducted. The 
system can monitor data and rangc constraints. perform maneuvers. or both. 
The aircraft with RAV links is inscrtcd in place o f  the simulation computers. 
Knowledge engineering Displays User 
programming A inputs 1 fExpert system 
M-M interlaces 
Expert systems 
interface 
Displays 
1Ih-zk-l interface 
LISP processor t 
Tra jecfory 
r m a n a g e r  -1 
I I 
Interface 
software 
I J 
TI Explorer r
- Trajectory 
controller 
I Flight test trajectory con t ro I ler 
I Ma);zver 
SEL 32/27 control 
law computer 
1 1  G m ~ m a n d  1 
generator 
I I storage I I 
I 1 Data-track 
monitor 
Shared 
memory Engineering units 
conversion 
SEL 32/27 
engineering units I computer 
369 
ATMS: Validation Configuration 
T h e  s imulat ion validation systcm a d d s  thc  Amcs-Dryden real- t ime s imula t ion  
facility computcrs  and cockpi ts  in place o f  the  workstation. In this  modc,  the 
FTE can  preview the f l ight  with a research pilot ,  o r  ob ta in  very  accura te  
information about  the fuel and range requirements .  
Knowledge engineering DisDlavr User 
programming inputs 
Expert system 
M-M interlaces 
I Expert systems machine 
software 
LISP processor f J 
L Trajectory 
manager 
Constraint y ‘““;I 
Executive F=?i 
Interface Trajectory 
data files 
68020 
TI Explorer 1 I I 
U 
Ethernet 
Trajectory 
controller 
Interface 
I I 
Flight test trajectory 
controller 
generator 
SEL 32/27 control 
law comtwter 
Shared 
simulation 
370 
S t a t u s  of t h e  Rapid Prototyping Faci l i ty  
The Rapid Prototyping Facility was dcvcloped to meet a nced for a facility 
which allows flight systcms concepts to be prototyped in a manner which 
allows for real-time flight test experience with a prototype systcm. This need 
was focused during the development and demonstration of the expert system 
flight status monitor(ESFSM). The ESFSM was a prototype system developed on 
a LISP machine, but lack of a method for progressive testing and problem 
identification led to an impractical system. 
The RPF concept was developed, and the ATMS designed to exercise its 
capabilities. The ATMS Phase -1 demonstration provided a practical vehicle for 
testing the RPF, as well as a useful tool. ATMS Phase I1 development continues, 
A dedicated F-18 is expected to be assigned for facility use in late 1988, with 
RAV modifications. 
A knowledge-based autopilot is being developed using the RPF. This is a system 
which provides elementary autopilot functions and is intended as a vehicle 
for testing expert system verification and validation methods. 
An expert system propulsion monitor is being prototyped. This system 
provides real-time assistance to an engineer monitoring a propulsion system 
during a flight. 
Demonstration of expert system flight status 
monitor (10186) 
Demonstration of Phase I ATMS (6/88) 
F-18 identified for facility (expected by 10188) 
KBS autopilot 
Engine monitor 
371 


Real-time application of knowledge-based systems

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