Our technology extends through circuit design and assembly, microcode and firmware development, integration algorithm and simulation model development, system integration and test, application software development, customer development process design and interfacing, and beyond. The articles below discuss the high-level concepts of real-time technology and offer real-world examples of how these concepts are applied to simulation-based development and model-based system engineering.
ADEPT Framework Applications
- Simulation Based Aircraft Testing
- Shipboard Systems
- Gas Turbine Engine Test Rig
Simulation Based Aircraft Testing
Real-time simulation is a powerful, heavily utilized tool for the development, verification, and airworthiness certification of modern aircraft. This technique combines some number of aircraft systems with the real-time simulation of aircraft components and/or elements of flight (ex: changing altitude, 6DOF, etc.) to place the aircraft systems into highly realistic flight test conditions. There are three common types of simulation based aircraft testing facilities:
Applied Dynamics offers the industry leading software suite, the ADEPT Framework, provides integrated systems, and is a technology partner to companies throughout the aerospace and defense and many other industries.
Avionics Testing Facilities
Electronics Integration and Verification
The use of electronic systems in new aircraft designs has steadily expanded along with greater interconnectivity and coupling between these systems. Each aircraft subsystem supplier develops and tests their Line Replaceable Unit (LRU) and its mating electronic system(s) through a range of verification tests as part of its development process and as required for airworthiness certification. But it’s when all of these complex, interdependent systems are brought together and integrated that many of the design and implementation anomalies and flaws are discovered.
Furthermore, new aircraft designs have added on-board wireless networking for passenger info and entertainment and to support the adoption of Electronic Flight Bag (EFB) capability. Ensuring that these network interfaces are fully secure, and cannot be exploited through some type of hack, is a critical task.
The avionics integration facility provides a powerful, simulation-based tool that is used to integrate and test these aircraft subsystems with lower cost and no risk of damaging a flight test aircraft in the process and provides the ideal platform for assessing and evaluating aircraft cybersecurity. The ADEPT Framework provides the software platform that layers on top of commercial-off-the-shelf computer equipment to create the real-time, simulation testing backbone for the avionics integration facility.
Supporting the Flight Test Program
The flight test program involves using some number of highly-instrumented prototype aircraft to fly an exhaustive series of test flights. During the execution of these test cases, unexpected behavior is inevitably observed. The avionics integration facility is put to work as a tool for repeating and investigating the unexpected behavior discovered during test flights. The specific conditions that resulted in the error may be replayed and the source of the problem can be determined. The problematic test case may be run again and again until the root of the problem is found. The ADEPT Framework includes the tremendous depth of capabilities required to enable this critically important work.
Distributed Real-Time System
The real-time server provides the simulation and testing backbone for the avionics integration facility. This computer system must interface with aircraft equipment throughout the lab. To minimize cable lengths and spread the computational load, the real-time simulation system uses a distributed, multi-node computational architecture. The ADEPT Framework includes the ADvNet Toolbox that allows distributed configurations to be easily implemented, controlled, and monitored.
An out-the-window visual scene generation system is typically used to provide the test pilot with realistic situational awareness. Scene generation systems include high-fidelity 3D animation, airport and runway modeling, and ground elevation. During simulated flight, the elevation above the ground will be determined by the out-the-window scene generation system and transmitted to the aircraft flight dynamics model. Latitude and longitude position, altitude, pitch, roll, yaw, and velocities are fed by the real-time flight dynamics simulation to the scene generation system, allowing the correct visual representation to be displayed. The ADEPT Framework makes it easy to establish the necessary closed-loop connection between the real-time simulation backbone and a commercially available out-the-window display system.
Integrated Modular Avionics
Integrated Modular Avionics (IMA) is a relatively new paradigm for the architecture and overall implementation of aircraft avionics systems. IMA makes better use of high-speed computer networks to share data, provides decoupling of software function and processing resources to better utilize powerful, multi-core processor technology, and provides a strategy to minimize cable interconnection (and thus weight) as the role and capability of avionics systems expands. IMA platforms were first used on the F-22 and F-35 and have since been used in a wide range of aircraft including the A380, A350, and Boeing 787. IMA systems introduce a tremendous amount of new technology in an aircraft program and as a result add a high level of technology risk. Simulation-based lab test facilities, such as the avionics integration lab, provide an important tool for the aircraft development program to mitigate this new technology risk. The ADEPT Framework continues to play a significant role in the development, integration, and verification of IMA systems for the latest aircraft designs.
Network Communication Testing
With more and more electronic systems in an aircraft, collecting data from more and more sensors, and sharing this data with other electronic systems, serial communication using digital networks throughout the aircraft is unavoidable. The ARINC-429 network databus commonly found in civil aircraft and the MIL-STD-1553 network databus found in military aircraft are nothing new but new aircraft designs are using more and more channels of these traditional networks. In addition to this older technology, low-cost Ethernet network technology has found its way into the aircraft in what’s called ARINC-664 or AFDX. ARINC-664 uses a cascaded star network topology, sophisticated network switches, and dual-redundant lines to provide determinism and fault-tolerant communication, as opposed to the not-so-deterministic communication offered with the TCP/IP Ethernet found in LANs. ARINC-664 offers network transmission speeds up to 1000x faster than ARINC-429 and can move far more information over a single cable link. Verifying and validating this aircraft network communication is an important task for the avionics integration facility. The ADEPT Framework includes a tremendous depth of capabilities required to perform comprehensive aero/defense network communication testing.
Iron Bird Simulator
Flight Controls Test Methodology
In modern aircraft designs, Fly-by-Wire flight controls actuate the flight control surfaces using electrical and electronic position sensors and actuation signals. These electronically controlled systems include a great deal of intelligence as required to ensure safety during failure conditions and provide additional capabilities not available in conventional cable-driven flight control systems. The Iron Bird facility is used to test the flight control system through a wide range of normal operating and failure-mode conditions without risk of crashing a flight test aircraft. The Iron Bird facility includes real control surface actuators, the associated hydraulic and electrical system components, sensors and drive electronics, the related avionics systems, and more. The ADEPT Framework provides the software platform layered on top of commercial-off-the-shelf computer equipment to create the facility’s simulation backbone.
Project development, test execution, test automation, data acquisition, data analysis, report generation, and test evidence archiving are performed using the ADEPT Framework tools. The ADEPT tools connect with the real-time simulation system across a standard TCP/IP Ethernet network. This provides a great deal of flexibility in the design of a facility and allows the team to connect from virtually anywhere, receive streaming test data, perform analysis, work collaboratively, and get the job done.
The Iron Bird facility includes a “force loading system” that applies hinge moment forces to the aircraft control surfaces (ex: ailerons, flaps, rudder, etc.) representative of the aerodynamics forces applied during the simulated flight test and driven by the flight simulation model. Mechanical actuators are mounted to the Iron Bird’s external structure and apply a load to each control surface under high-fidelity, closed-loop control by the facility’s real-time aircraft simulation. Low-latency and real-time determinism in the entire system are of critical importance. If the system under-performs then the test results are invalid. The ADEPT Framework is industry-tested to meet the demanding real-time performance requirements of the Iron Bird facility.
Cockpit Development, Integration, and Verification Testing
A cockpit integration facility is a simulation based lab test facility that serves many purposes including the development, integration, and verification of cockpit and flight deck systems throughout the aircraft development program. There are two common types of cockpit integration facilities found in the civil and military aircraft industry. Although each aircraft company tends to use different names for these labs, they can be recognized as:
- Cockpit Systems Integration and Verification Lab
- Cockpit Concept Development Lab
Both types of facilities combine real-time simulation of flight dynamics and simulation of many aspects of the aircraft with realistic closed-loop stimulus to the flight deck, pilot controls, and systems included in the cockpit integration facility. The ADEPT Framework provides the software platform that layers on top of commercial-off-the-shelf computer equipment to create the simulation and test backbone of the facility.
Cockpit Systems Integration and Verification Lab
The Cockpit Systems Integration and Verification Lab is a facility where real flight deck systems and pilot controls are integrated and placed in a real-time, hardware-in-the-loop environment where the systems are taken through exhaustive and realistic verification testing. Pilot-in-the-loop, and automated (no pilot-in-the-loop) test cases are executed allowing stand-alone behavior and interoperability to be verified against expected behavior during normal and failure-mode flight conditions. Cockpit systems suppliers will participate in many of these test cases to provide the domain expertise required to assess behavior and troubleshoot observed problems.
Cockpit Concept Development Lab
The Cockpit Concept Development Lab is a facility where emulated or mock-up flight deck systems and pilot controls are placed in a real-time, hardware-in-the-loop environment for development and assessment with pilot-in-the-loop as part of an aircraft development process. Because the cockpit concept lab does not use real cockpit systems, this facility represents a lower-cost tool for exploring innovative ways of implementing the cockpit (ex: glass cockpit functionality). As the early development tasks are completed, the Cockpit Concept Development Lab can then be repurposed as a tool for aircraft simulation and flight control law development.
Aircraft Simulation Model Development
In addition to developing and testing cockpit concepts and systems, the cockpit integration facilities provide an important tool for developing and validating the real-time aircraft simulation model that is used in all of the simulation based lab test facilities (ex: iron bird, avionics integration facility). During an aircraft development program, virtually every aspects of the aircraft design will evolve. This design evolution results in a continuously evolving real-time aircraft simulation model. As additional modeling detail and fidelity are added to the aircraft simulation model, a new version of the model is issued and must be validated prior to releasing the model for general use. The cockpit integration facility represents the lowest-cost, high-fidelity, pilot-in-the-loop flight simulator and therefore is ideally suited to perform this man-in-the-loop simulation model validation.
Pilot-in-the-Loop Simulated Flight
Pilot-in-the-loop simulated flight is an important tool for tasks such as: evaluating the handling qualities of an aircraft design and its fly-by-wire flight control laws; getting a sense of the usability of a glass cockpit layout; assessing the convenience of the positioning and layout of flight deck systems. When compared with using a motion-based flight simulator or a flight test aircraft, the cockpit integration facility is a very inexpensive way to submerse a pilot into highly realistic simulated flight test assessment. In order for this pilot-in-the-loop evaluation to be meaningful, the cockpit simulator must operate with high real-time determinism, good repeatability, and low latency. The ADEPT Framework has been developed for the needs of, and successfully deployed for, industry leading civil and military cockpit integration simulator facilities.
Interconnected Simulation Test Labs
Many of the recent and on-going aircraft development programs have added the ability to connect their cockpit integration facilities to other simulation based lab test facilities. For example, the Cockpit Systems Integration lab may be connected, with appropriate cabling and signal switching, to the Iron Bird simulator. With the two facilities disconnected, each facility may be operated as a separate tool for development, integration, and verification. By connecting the two facilities the combination of a cockpit with full flight deck, pilot controls, and avionics modules is added to aircraft hydraulics, electrical power, and control surface actuation focused test facility. This allows the test scope to extend all the way from pilot controls to the actuation of ailerons, flaps, etc., and expands the scope of interoperability testing. The ADEPT Framework makes it easy to connect multiple distributed real-time simulation facilities using a range of communication interface options.
The revolution, that is model based system engineering, continues to take hold in the area of shipboard systems. The concept of an All-Electric Ship (AES) has expanded since 2000 when the US Navy selected electric-drive propulsion for use in the DDG-1000 destroyer. The AES concept offers a range of benefits for the Navy-of-the-future but it also includes a wide array of technical challenges best solved using model based techniques.
In an AES architecture, systems found in traditional ship designs, based on steam, hydraulic, and pneumatic power, are replaced with electric systems. Electric power is supplied to the ship with traditional onboard power generation such as gas turbine engine, diesel engine, or nuclear power and is fed into the shipboard power grid. Key benefits of the AES approach are numerous, including better fuel efficiency, ability to support power requirements of advanced weapons and communications systems, reduced ship lifecycle costs, increased stealthiness, and improved survivability.
Of the power generated in the All-Electric Ship, approximately 70% to 90% in an Integrated Power System (IPS) is used by the ship propulsion systems. During mission critical or life critical situations the interactions between shipboard systems sharing power represents a significant challenge. The management of power demand and the ability to actively reduce power demand for less critical systems, during a wide array of scenarios, must be accounted for. Furthermore, the overall design of this highly complex, tightly coupled integrated shipboard power architecture poses a challenging set of problems, particularly when the overall goal is to design an optimally efficient architecture.
Real-time simulation based development, integration, and verification facilities, as well as model based rapid controller deployment systems, are tremendously important tools to help solve these shipboard system engineering challenges.
Shipboard systems are designed, characterized, and optimized using desktop simulation. Next, each system is combined with some amount of “real” equipment and some amount of simulation to develop and integrate a wider scope of capability. Eventually, all the individual systems (or as many as possible) are brought together in a real-time simulation based integration facility and connected to simulated behavior of the ship’s normal operating and failure mode conditions to thoroughly investigate and understand the interactions between power electronics, machines, and sea conditions. The ADEPT Framework provides the software platform that layers on top of commercial-off-the-shelf computer equipment to create the simulation testing backbone for shipboard systems development. The ADEPT Framework includes the tremendous depth of capabilities required to handle the large, many-system, distributed architecture of a shipboard systems integration facility and to include the large computational capability required to accurately simulate the unpredictable and complex behavior of sea conditions interfaced with stochastic time-varying propulsion loads.
Integrated Power System
The IPS, known in the commercial marine industry as Integrated Electric Drive (IED) and renamed in military applications for obvious reasons, offers a highly efficient, electric-side integrated power and propulsion system by combining advanced solid state power electronics, multi-Megawatt motor drives, and automated controls. The ADEPT Framework is designed to meet the high-performance requirements associated with the development of IPS subsystems and the integration of each subsystem into the complete, optimized IPS. Technologies such as hyperfast, multi-core real-time task allocation and FPGA based simulation and control integral to ADEPT and critical to IPS development.
FPGA based Simulation, Data Acquisition, and Control
The implementation of advanced power generation, conversion, and motor control has become increasingly dependent on FPGA integrated circuits with purposed-designed HDL code to provide a maximum-frequency, maximum-efficiency solution. FPGAs are used as sub-microsecond-frametime HIL simulation processors as well as central processing units for the control of a given subsystem (ex: power converter control, power generation control, motor control). The ADEPT Framework supports commercial-off-the-shelf FPGA computer boards within a small hardware-in-the-loop simulation and prototyping system and within large, multi-node, distributed hardware-in-the-loop simulation and prototyping facilities with unmatched performance.
Gas Turbine Engine Test Rig
Effective Aircraft Engine Development and Certification
Simulation based verification is a critical element of the development of an aircraft engine’s Full Authority Digital Engine Controller (FADEC). The FADEC is comprised of the Electronic Engine Controller (EEC) providing control and safety for the gas turbine engine, the fuel metering unit, the engine health monitoring system, and several other components. Real-time, hardware-in-the-loop simulation rigs are used to perform development, integration, and certification tests on each component of the FADEC and on the combined, integrated set of components. These simulation based test systems are used to test the FADEC to demonstrate that it is compliant with the airworthiness requirements and to generate the evidence that is submitted to the regulator body to achieve certification.
The airworthiness requirements for the EEC can be summarized as:
- The EEC must match the control system percent of available power or thrust controlled in both normal operation and failure condition, and range of control, specified for the engine – in other words, the EEC should operate as documented in the engine manuals
- The EEC must be designed and constructed so that any failure of aircraft-supplied power or data will not result in an unacceptable change in power or thrust, or prevent continued safe operation of the engine
- The EEC must be designed and constructed so that no single failure or malfunction, or probable combination of failures of electrical or electronic components of the control system, results in an unsafe condition
- The EEC must have environmental limits, including transients caused by lightning strikes, specified in the instruction manual – and environmental tests must be performed to demonstrate
- The EEC must have all associated software designed and implemented to prevent errors that would result in an unacceptable loss of power or thrust, or other unsafe condition, and have the method used to design and implement the software approved
The above airworthiness requirements are for the EEC only. Beyond the requirements listed above, the EEC and other safety-critical electronic systems found in an aircraft must also have software developed in compliance with DO-178B/C which dictates software certification requirements and process. Furthermore, there is a range of other requirements associated with the complete gas turbine engine (ex: fire protection, bird ingestion, parts manufacturing, life-limited parts, etc).
Certification is obtained by producing evidence to show that the engine’s FADEC meets these requirements. Evidence is generated using analysis, open-loop test methods, and simulation-based closed-loop test methods. Simulation based testing of the FADEC is typically the responsibility of the engine and FADEC supplier(s).
Engine Test Rig
A gas turbine engine test rig is a tool used by all major aircraft engine manufacturers and FADEC component suppliers. The test rig combines:
- real-time simulation processors
- sensor emulation I/O:
- thermocouple sensors
- pressure sensors
- LVDT sensors
- resolver sensors
- strain gauge sensors
- fuel flow sensors
- potentiometer sensors
- torque sensors
- actuator and load emulation I/O:
- torque motor emulators
- solenoid emulators
- stepper motor emulators
- igniter emulators
- aircraft databus (ARINC-429, ARINC-664, MIL-STD-1553) interface and emulation
- emulated aircraft power
- reconfigurable signal mapping interface
- electrical fault insertion system
- gas turbine simulation model
- software framework providing real-time services on the rig and desktop tools for performing comprehensive test related activities
Applied Dynamics is the largest commercial supplier of gas turbine engine test rigs. The ADEPT Framework provides the software platform that layers on top of commercial-off-the-shelf computer equipment to create a cost effective solution that can be seamlessly woven into our customers development and verification processes.