CASE STUDY - Eurofighter (Typhoon) hydraulic test rig

The purpose of hydraulic test rig project was to provide a software solution to control a hydraulic test bench and execute sequences to test the performance and functionality of hydraulic components from the Eurofighter aircraft. Amfax was asked to work in conjunction with a hydraulic equipment manufacturer to design and develop both the software and the hardware.

---

Key benefits of Amfax's involvement

• Assistance in the specification and design of system hardware
• Delivery of a distributed real time control system using the latest innovations from National Instruments
• Accommodate and design custom pump control loops using a PID implementation
• Design allowed for switchable / isolatable hydraulic power supplies
• Engineers worked through design, development and test witnessed and accepted by the Eurofighter Nation's Airforces

The resulting system was a generic test platform which allowed the end customers to strip and test Eurofighter hydraulic components without having to send them back to the manufacturer.
This vastly reduced the costs for supporting operational aircraft.

---

System safety and design innovation were key

Operator safety was a key consideration for the hydraulic test rig. Hydraulic power packs capable of delivering 360bar pressure or 180 l/m flow could do serious damage. Our solution's design addressed these concerns

Real time control

The safety critical system was built around an NI-PXI RT controller and LabView RT. 

A time critical 50ms epoch for the control system which was able to guarantee timely reaction to a change, such as a pressure surge in a fixed time frame

C.B.I.T

The CBIT or (C)ontinuous (B)uilt (I)n (T)est was designed to monitor active system pressures, flows, voltages and currents.

Any deviation from normal caused the system to cut all power from supplies, either hydraulic or electric.

Watchdog

In addition to the C.B.I.T., a watchdog relay governed all electrical controls for the system. If there was ever a critical failure on the RT controller, this watchdog relay ensured any active power to the control system would always be cut.

---

System software and hardware used

LabVIEW
LabVIEW was used as the primary development language for this project and delivered the following benefits :

• Rapid development
• Hardware support
• Accredited code standards
• Wide industry support

LabVIEW Real Time
The real time module for LabVIEW allowed us to make use of PXI RT hardware, broadening the scope and capability of this system.

• Deterministic Epoch
• Safety critical

TestStand
Each type of hydraulic component needed its own test sequence with step by step limits and custom control conditions. TestStand was the natural choice for this and offered these benefits :

• Separate test from application
• Custom step types
• Separate installers

Hardware
The RT system hardware was housed in rackmounted PXI chassis, one chassis in each hydraulic power supply and one in the hydraulic test bench, in some of the installations, these components were housed in separate rooms. 

The user interface was housed in a control and display unit, controlled by a 19" Rackmount Industrial controller running a Windows operating system.

Test Bench hardware included

• Digital I/0
• Analogue I/O
• DMM
• Counter timer module
• Scope
• Arb

Hydraulic power supply control included

• Digital I/O
• Analogue I/O
• Counter timer module

Control and display unit contained

• Industrial controller
• Dual monitor output
• Printer for automatic reports