Pilot studies are customer-driven applications that demonstrate the feasibility of applying the Simplex Architecture to a specific problem area.

The Simplex Applications have been developed by other organizations with the cooperation of the SEI. These applications use the Simplex Architecture to address a domain-specific problem.

Video introduction to the Simplex Demonstrations (1:12 minutes, 429 Kb, RealNetworks™ RealVideo® format)

A RealVideo media player can be downloaded from the RealNetworks web site.

Quick Index

• Simplex Demonstrations
• Singleton Demonstration - Simplex on a single CPU
• Legacy Demonstration - replace an old, undocumented system
• Multiprocessor Demonstration - hardware fault tolerance using peer voting
• Simplex Pilots
• Distributed Demonstration - fault tolerant, COTS based, conceptual prototype for the U. S. Navy
• Coordinated Prototype - coordinated motion in the face of communications disruption
• Simplex Applications
• PECVD Application - silicon wafer production
• INSERT - autopilot upgrade to an F-16 simulator

Simplex Demonstrations

Singleton Demonstration

Overview

Using the Simplex Architecture, real-time control software is tested, altered, and replaced without halting the application and without losing control of an unstable inverted pendulum. This was the first Simplex demonstration completed, serving as proof of concept.

System Characteristics

Single commercial-grade PC computer
• POSIX .1b compliant operating system - LynxOS
• Inverted pendulum

Simplex Features

• A single platform for simultaneous code development and test
• Software can be modified without halting operations
• Active system can switch between programming languages (C and Ada95)
• System tolerates faults in the modified control software

Legacy Demonstration

Overview

The Simplex Architecture is applied to the problem of replacing an old, undocumented legacy application, which has reached the end of its useful life. In this demonstration the Simplex Architecture is used to replace inverted pendulum control software without modification to the the legacy application or the computer that runs it. The new real-time control software is tested, altered, and replaced using the old software as a backup controller. After testing, the old system can be completely removed.

Derived from the Singleton Demonstration, the Legacy Demonstration uses the same inverted pendulum, with the vendor-supplied control software serving as the legacy application. A custom switch circuit allows the two systems to simultaneously share sensor data and to select one of the systems to control the pendulum.

System Characteristics

• Legacy PC: 80286 CPU running a DOS real-time application
• Simplex PC: Commercial grade system running a real-time Unix based operating system
• System switch
• Inverted pendulum

Simplex Features

• Faults in new system's control software are tolerated
• No modification to legacy hardware or software required
• Legacy system can be removed after testing

Multiprocessor Demonstration

Overview

The Multiprocessor Demonstration was developed to explore solutions to the upgrade paradox problem in a multiprocessor, fault-tolerant system. The upgrade paradox can occur when functionality is partially altered in a multiprocessor system which determines correct behavior by comparing processor output, expecting near or complete agreement. A three-way voting system is a typical example: there is no way to safely introduce new software for testing without risking system failure because there is no combination of new and old software which allows the new software to run until it fails but not after.

Like the single computer Simplex demonstrations, a real time control system was developed. While an unstable inverted pendulum is continuously controlled, the Multiprocessor Demonstration tolerates both software and hardware faults. The Multiprocessor Demonstration also supports the repair and alteration of hardware and software while maintaining control of the pendulum. Using the leadership protocol and appropriate decision logic, system hardware and software need not be identical and the individual systems run asynchronously.

System Characteristics

• 3 PC-based computational nodes: commercial grade systems running a real-time Unix based operating system
• Graphical user interface system
• Switch box for voting and data I/O
• Inverted pendulum

Simplex Features

• Software tolerates one arbitrary system failure on any member system and a crash failure of a second system
• Support for on-line hardware and software upgrade and test
• Any software component may be upgraded
• New software may be safely tested without facing the upgrade paradox
• Support for systems with heterogeneous software and hardware

Simplex Pilots

Distributed Demonstration

Overview

The Distributed Demonstration was developed to demonstrate a Simplex approach for a submarine control system under U. S. Navy sponsorship. Emphasis is placed on the use of COTS components in a fault-tolerant control system with high reliability and availability requirements. The system topology and functions replicate, in commercial grade components, the planned system. In addition to the usual demonstration of fault tolerance and upgradeability, consideration is given to the issues of software safety and certifiability in the software design.

System Characteristics

• Heterogeneous computational nodes
• Separate, redundant data acquisition/voter nodes
• Network communications
• "Bubble Control" system
• User interface system

Simplex Features

• Support of safe commercial-grade COTS usage in high reliability systems
• Online replacement and upgrade support
• Effective solutions for interactive consistency problems

Distributed Demonstration detailed description
Video of the Distributed Demonstration (7:19 minutes, 2.5 Mb, RealNetworks RealVideo format)

Coordinated Prototype

Overview

The Coordinated Prototype demonstrates an approach for constructing a fault resistant system capable of performing coordinated motion in a hostile communications environment. The demonstration uses two inverted pendulums to provide visual feedback and as a tangible indication of failure.

System Characteristics

• Standard PCs used as system nodes
• Paired inverted pendulums for visual feedback

Simplex Features

• Uses separate movement and coordination controllers
• Implements fault-resistant communications

Coordinated Prototype detailed description
Video of the Coordinated Demonstration (5:07 minutes, 1.8 Mb, RealNetworks RealVideo format)

Simplex Applications

PECVD Application

Overview:
The Plasma Enhanced-Controlled Vapor Deposition (PECVD) Apparatus is used for the development of improved semiconductor production software and techniques. Experimental software is frequently used to run the equipment, at the risk of failed runs and time-consuming cleaning if the vacuum chamber is contaminated. Application of the Simplex Architecture allows the safe completion of experimental runs even in cases where new software is defective.

PECVD Application detailed description

INSERT Autopilot Prototype

Overview:
The INSERT (INcremental Software Evolution for Real-Time applications) Project used Simplex to insert new technology into an existing aircraft simulation. The new autopilot software is fault resistant and allows the on line upgrade and test of the autopilot subsystem.

System Characteristics

• Simplex Subsystem: PC running a real-time Unix based operating system
• Aircraft Simulator: Silicon Graphics 02

Simplex Features

• Simplex inserted as a subsystem
• Fault detection to ensure vehicle safety

INSERT detailed description
Video of the INSERT Demonstration (6:30 minutes, 2.3 Mb, RealNetworks RealVideo format)