2006-2007 - Kennedy Space Center Technology Transfer Office

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Generating Safety-Critical PLC Code From a High-Level ApplicationSoftware SpecificationThe benefits of automatic-application code generation are widely accepted withinSeamless Command and the software engineering community. These benefits include raised abstraction levelControl Coordinationof application programming, shorter product development time, lower maintenancecosts, and increased code quality and consistency. Surprisingly, code generationconcepts have not yet found wide acceptance and use in the field of programmable logic controller(PLC) software development. Software engineers at Kennedy Space Center recognized the needfor PLC code generation while developing the new ground checkout and launch processing system,called the Launch Control System (LCS). Engineers developed a process and a prototype softwaretool that automatically translates a high-level representation or specification of application softwareinto ladder logic that executes on a PLC.All the computer hardware in the LCS is planned to be commercial off the shelf (COTS), includingindustrial controllers or PLCs that are connected to the sensors and end items out in the field. Mostof the software in LCS is also planned to be COTS, with only small adapter software modules thatmust be developed in order to interface between the various COTS software products.A domain-specific language (DSL) is a programming language designed to perform tasks and to solveproblems in a particular domain, such as ground processing of launch vehicles. The LCS engineerscreated a DSL for developing test sequences of ground checkout and launch operations of futurelaunch vehicle and spacecraft elements, and they are developing a tabular specification format thatuses the DSL keywords and functions familiar to the ground and flight system users. The tabularspecification format, or tabular spec, allows most ground and flight system users to document howthe application software is intended to function and requires little or no software programmingknowledge or experience. A small sample from a prototype tabular spec application is shown inFigure 1.Figure 1. Sample of tabular spec formatted application.The LCS developers needed a mechanism or tool to translate application software from tabular specformat into PLC code to execute on the PLC platforms out in the field. The functionality of somerepresentative samples of tabular spec was manually coded into PLC ladder logic and tested with afield item simulator to verify the proper operation of the manually coded ladder logic. This manualprocess of conversion or translation from tabular spec representation to PLC ladder logic demonstratedthat translation points or patterns existed between portions of the tabular spec and portions ofthe PLC ladder logic.With the aid of these translation points, a few representative samples of the manually coded PLCladder logic were exported from the PLC coding Integrated Development Environment (IDE) asplain text. This exported text was then converted by hand into plain-text PLC code “libraries” withthe intent that a future automatic utility to translate tabular spec to ladder logic would use these PLCcode libraries. After some representative samples were translated from tabular spec to PLC ladder116 Command, Control, and Monitoring Technologies
Figure 2. Transition process flow.logic and after a PLC code library was manually createdfor each of the translation points contained in thesamples, a prototype automatic translation utility wasdeveloped and demonstrated. The translation capabilitiesof the utility will be expanded upon as more and moretranslation points are identified, translated manually, andthen turned into additional PLC code libraries.Figure 2 shows the simplified process flow for translatinga single “send_command” line from tabular spec toPLC code. The spreadsheet that contains the applicationsoftware in tabular spec format is exported to plain textand is used as input to the translation utility, along withthe PLC code library. The translation utility processesthese input files, using program transformation steps.This creates an output file that can be imported by thePLC coding IDE.This work successfully demonstrated that a process anda software tool can generate executable PLC code froma high-level specification representation of a safety-criticalcontrol system. This process includes some manualwork to find translation points and to create PLC codelibraries, but that up-front and one-time manual effort isovershadowed in the end by the automatic generation ofrepetitious and tedious functionality that would be difficultand error-prone to perform manually. Such a processand tool increase the quality, reliability, maintainability,and verification/validation pedigree of the PLC code overcode that is generated manually. It also provides a highlevel of PLC code consistency and could even reduceoperations and maintenance costs for the control systemafter it is deployed.Follow-on phases of development of the automatictranslation utility should include most, if not all, of thefollowing tasks:• represent as much LCS application softwarein the tabular spec format as possible withoutovercomplicating the tabular spec format,• manually implement the remaining translationpoints and any newly discovered translation points,along with the matching PLC code libraries,• add code to the translation utility to recognize andhandle the new translation points, along with thenew PLC code libraries, and• test and certify the translation utility for automaticgeneration of safety-critical PLC control logic in theLCS at KSC.Contacts: Kurt W. Leucht ,NASA-KSC, (321) 861-7594; and Glenn S. Semmel, NASA-KSC, (321) 861-2267KSC Technology Development and Application 2006-2007117
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ForewordSuccessful technology devel
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ContentsSpaceport Structures and Ma
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Contents (continued)Process and Hum
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IntroductionJohn F. Kennedy Space C
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Constellation SystemsSurfaceSystems
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Spaceport Structures and MaterialsK
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20181614∆ E1210Modified Sensor Be
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Initial results of the EDEM model o
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Contacts: Dr. Carlos I. Calle ,NASA
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Close examination of the corrosions
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Adhesion at Failure (psi)2500200015
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Figure 1. After 500 hours of salt f
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Contacts: Dr. Paul E. Hintze , NASA
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Figure 2. Repairs to various types
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on top of the cuvette contains the
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Figure 2. A corrugated NiTi sheet e
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The PLTD can be used to (1) calibra
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SEM images of neat MWNT fibers: (a)
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Contacts: Trent M. Smith
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Figure 1. An isometric cutaway view
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Figure 2. Quartz sand flowing in th
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Figure 2. Top images show how the e
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Sand volume fraction contour at t =
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Integrated LWRD/RVC engineering bre
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Mean relative percentage change in
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We compared the model’s predictio
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Figure 2. Three-dimensional simulat
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Figure 3. Camera calibration model.
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The sketch in Figure 2 shows alaunc
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Figure 2. Signal generator (right)
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Hail Size Distribution MappingA 3-D
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Launch Pad 39 Hail Monitor Array Sy
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Autonomous Flight Safety System - P
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The Photogrammetry CubeSpaceport/Ra
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Bird Vision SystemThe Bird Vision s
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Automating Range Surveillance Throu
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Next-Generation Telemetry Workstati
Page 80 and 81: GPS Metric Tracking UnitAs Global P
Page 82 and 83: Space-Based RangeSpace-Based Range
Page 85 and 86: Fluid System TechnologiesKSC Techno
Page 87 and 88: 0.900.850.80Discharge Coefficient,
Page 89 and 90: Composite seals for performance eva
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Page 93 and 94: Contacts: Dr. Barry J. Meneghelli ,
Page 95 and 96: 60555045Comparative k-value (mW/m-K
Page 97 and 98: a compatible spacecraft model where
Page 99 and 100: In an ongoing effort for improvemen
Page 101: Low-gravity probe prototype test.th
Page 104 and 105: Countermeasure for Radiation Protec
Page 106 and 107: Focused Metabolite Profiling for Di
Page 109 and 110: Process and Human FactorsEngineerin
Page 111 and 112: DON uses game technology to enable
Page 113 and 114: Type of mobile crane that impacted
Page 115 and 116: SALT proof-of-concept communication
Page 117 and 118: SSLM CAD model.Our design offers th
Page 119 and 120: Variables that can be integrated by
Page 121: Exploration Supply Chain Simulation
Page 124 and 125: Nanosensors for Evaluating Hazardou
Page 126 and 127: Sixty-four-Channel Inline Cable Tes
Page 128 and 129: Wireless Inclinometer Calibration S
Page 132 and 133: Spacecraft Electrostatic Radiation
Page 134 and 135: Ion Beam Propulsion StudySpacecraft
Page 136 and 137: RT-MATRIX: Measuring Total Organic
Page 139 and 140: Appendix AKSC High-Priority Technol
Page 141 and 142: Risk Assessment ToolMission Data Fe
Page 143 and 144: Appendix BInnovative Partnership Pr
Page 145 and 146: system for the Government, using th
Page 147: tracking objects after launch, and
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2006-2007 - Kennedy Space Center Technology Transfer Office

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