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Helicopter Electromechanical Actuators Test Rig (HEMAS TEST RIG)
Article.
FLAVIA’s approach to the Test Rig Development.

ABSTRACT
Aircrafts and Helicopters weight reduction, is a continuous way to reduce fuel consumption achieving greener operations.

Hydraulic system is used for different purposes as acting hydraulic actuators for moving control surfaces to command the flight. Hydraulic system has a considerable weight, since it has not only actuators but pumps, valves, piping, etc.

A/C and Helicopter systems manufacturers, have taken the challenge to develop Electromechanical Actuators to replace the hydraulic actuators, reducing overall weight.

The Helicopter Electromechanical Actuators are also known as HEMAs.

The new HEMAs are different from the current hydraulic helicopters’ actuators, so the HEMAS TR must give an answer to the challenges for testing properly the HEMAs (forces, speed, acceleration, electrical consumptions) before implementing in the helicopters.

The challenge is to develop an Advanced Test Rig for testing the next generation of Helicopters Electromechanical Actuator Systems (HEMAS).
The project is so called HEMAS TR (HEMAS Test Rig)

This article also gives an approach to the solution for Cleansky JTI-CS-2012-02-GRC-03-014 Topic.

CAPABILITIES OF THE TEST RIG
The HEMAS TR provides a controlled Load Simulation System for the HEMAs.
All process is controlled by the Local Control System, a powerful Hardware & Software System. The Human Machine Interface (HMI) of the Local Control System allows preparing automated and manual tests, in a friendly visual way.
Some of these tests are previously defined load simulation patterns, and others correspond to Flight Control Computer (FCC) Simulator.
Additional tests can be programmed easily through Excel files.
The test results are stored in industry-standard format files, and can be easily accessed local or remotely for data mining. Graphs, test reports, compared studies to analyze HEMAs behaviour, etc can be done from this record files.
It is possible to work with up to three Units Under Test (UUT), being each of them, Electromechanical actuators independently controlled through Local Control System.
The HEMAS TR can also be connected to a bigger Test Rig with all the systems, communicating with its control system to receive commands and send information in Real Time. This bigger Test stand is called ETB (Electrical Test Bench) or “Copper Bird”.

ENGINEERING. RESEARCH AND DEVELOPMENT
The HEMAS Test Rig must be developed for each specific HEMAS, looking at the state of the art of the technologies involved, and researching and developing solutions to fulfill the testing requirements, and control and communications necessities.

The concept of FLAVIA Test Rig also includes transportability, so the whole system will be developed to be installed in ISO containers for better transportation.

All FLAVIA Test Rigs are CE marked.

Following engineering topics must be researched and developed for the HEMAS TR:

1. LOAD SIMULATOR SYSTEM
The Load Simulator System will be able to load individually each UUT (composed by two HEMAs) receiving the proper load patterns from the Local Control System.

The system generates controlled opposite forces to the HEMAs under test, to simulate flight load conditions or load patterns for a number of purposes for testing HEMAs.
A solution for the Load System is to be analyzed and developed for each case, based on a static and dynamic physics model.
The Load System is composed of load actuators mounted on a load frame.

With the selected performances below, the optimum solution appears to be a hydraulic system, composed by hydrodynamic actuators commanded by high-speed servovalves.

The hydraulic system is powered by a high pressure hydraulic supply system, 55l/min@250bar, ISOVG32 hydraulic fluid, 200l reservoir, and 3 microns filters, to avoid the servovalves to receive any contamination.

The hydraulic supply system is cooled and additionally filtered at 5 microns with an offline circuit, cooled by air.

First brands for components are chosen as Moog, Bosch-Rexroth, Parker, etc. Proper flushing procedures are explained to the user to maintain servovalves in optimum condition.

They can be achieved for instance, following load performances:

- Operation mode of Load Simulator: closed loop force control
- External load per actuator: +/-40kN (dynamic), +/-50kN (static)
- Dynamic requirement: static offset 15kN (compression), amplitude 25kN, bandwidth: up to 30Hz.
- Controlled overshoot at operation against a hard stop at max speed: 5kN.
- Output speed of piston: 120mm/s max.
- Stroke: up to 200mm

The Load Simulator shall provide sensors for measuring and recording force, speed/acceleration, and position,100Hz..

2. MECHANICAL SYSTEM
For optimum behaviour and control, the Load Frame for Load Simulator System must be developed specifically. It will be studied the static, stiffness and frequency parameters of the system, by mean of FEM analysis, to take the decision for the proper design. 4 beams stabilized steel frame, with hydraulic tooling for moving and fixing the upper beam is our first choice for the Finite Element Simulation and further load frame design and manufacturing. Specific tooling for mounting the HEMAs to the Load Frame and Load actuators will be developed.

Each HEMA can have its own load frame fixed to ground to avoid interferences and vibration transmission between them.

The load frames can be fitted with climate chambers for high or low temperature tests. (Optional under request)

One of the issues while designing test rig is further transportability to customer locations. The HEMAS TR will be designed to fit into ISO 10 ft containers for easy road transport to users locations.

3. LOCAL CONTROL SYSTEM
Local Control System controls Load Simulation System, HEMAs, safety aspects of the TR and communicates with Copper Bird in real-time, and recording non real-time data synchronizing operations with Copper bird clock.

Local Control System platform includes Load Simulation and Flight Control Computer (FCC) Simulator, by means of a friendly HMI in a local computer system, and can be controlled locally in Emulation mode or remotely. It can also act receiving set points and commands from the Copper Bird.

Due to the demanding requirements in control, acquisition and communications, it is commonly used in FLAVIA’s Test Rigs, National Instruments PXI platform, with LabVIEW software specifically developed for each Test Rig.

This platform can fulfill the Real-time communications, clock synchronizing, high speed recording, and control of the whole system.

It is integrated in an industrial rack with a LCD display for local control, and can be controlled remotely by Ethernet.

All the sensors report to Local Control System. The test results are stored in an external high speed RAID storage National Instruments unit, with huge capacity to store long term, high speed acquisition tests.

Set Point generator
The load set point generation is performed by the real-time PXI Controller . Actuator tests are performed in two different manners:
Generation of load steps: Each step has a configurable duration and each actuator can have a specified load.
Generation of load cycles: Each cycle is an arbitrary waveform that can be created in the operator interface software. The number of cycles and cycle duration are configurable.

HMI
The HMI (human Machine Interface) of the HEMAS Test Rig is a graphic very user friendly environment, where user can control all the parameters of the Test Rig in different level accesses, password protected.

Tests can be selected from a list, and additional tests can also be added by user in an easy way through MS Excel file to define each stage of the test parameters.

Result of the tests can be monitored in values or graphs, and recorded in the storage system. They can be analyzed and compared easily after the tests.

The HMI can also be controlled remotely, so that operator can be working in other location by mean of Ethernet access.

SOFTWARE
The software will be developed under National Instruments LabVIEW platform. Two applications will be developed:
- Acquisition and control application on real-time PXI system.
- Windows application that allows communication with PXI and allows communication and synchronization with Copper Bird.
- Application in Windows that will allow the implementation of HMI.
- The software will set up test in local mode or remote mode, display of all data and variables and to perform data recovery saved.
The software will allow the representation and obtaining force-displacement curves during the execution of the tests

4. COMMUNICATIONS
Local Control System can be connected with a Copper Bird for actuation and communications from/to the Copper Bird. (interfaces and protocols to be agreed)

The HEMAS TR clock can be synchronized with Copper Bird Clock, by mean of an NTP ethernet server included in PXI system, so all records will have the same time in both systems. It is also possible with the proposed system, to use external synchronizing with a satellite IRIG-B signal, very common when synchronizing different test rigs for using a common time.

REMOTE MODE
The PXI controller will allow remote access via Ethernet interface 1 GHz with the outside world to be commanded by mean of Ethernet commands. All programming software of the supplied equipment will be developed under the National Instruments LabVIEW environment using the specific module for LabVIEW.
Real Time acquisition deterministic signals will be provided at 10 Hz for acquisition and communication.
The non deterministic acquisition signals will be made to 100 KHz sample rate.

(Interfaces with HEMAs and Copper bird to be agreed with customer)

5. ELECTRICAL SENSOR AND SUPPLY SYSTEM
The electrical system is part of the Local Control System and provides the proper sensors to measure the voltage and current provided to the HEMAS from the Copper Bird in Voltage range: 0-400V, + transients at high frequency and Current range: ±50A, 100Hz.

The HEMAS TR Hill also incorporate 270VDC and 28VDC power supplies for the HEMAs to be tested in a stand-alone test rig configuration.

First brands for components are chosen as Siemens, Schneider, Honeywell, etc.

6. INSTALLATION AND COMISSIONING
The HEMAS TR can be customized for each necessity, and can be delivered in any worldwide location.
Delivery includes installation and commissioning and an operation and maintenance training course for users.

ADVANTAGES. Q&A
Why using hydraulic servoactuators?
Despite the technical development of the industrial Electromechanical Actuators, the actual EMAs, have even notable limitations to achieve the behaviors required to perform the tests. Hydraulics is very fast and stable technology. With the help of the high dynamic response servovalves can reach high frequency of extension and retraction with a high accuracy in the developed load. In addition the hydraulic actuators are able to withstand much higher work cycles.
In any case, some manufacturers can provide EMAs that could result a good choice to be studied in terms of inertia, stroke, acceleration, frequency for this or future developments.

How to ensure smooth displacements of the actuators avoiding irregular movements at high frequency?
The servoactuators will be built using the latest technology providing internal walls with a perfect surface finish and hydrostatic bearings. In addition a hydraulic power unit equipped with vacuum system and high filtration system ensures that the fluid is free of air and particles that could disrupt the linear movement of the actuator.
Through closed loops using high performance sensors it is possible to control the forces of positive or negative with high accuracy.

How to ensure the autonomy of the HEMAS Adaptation Kit?
The HEMAS TR has been design to operate connected to Copper Bird or in stand-alone configuration. This is possible because the unit incorporates two Power Supplies and a hydraulic Power Unit to convert the input voltage (400 VAC) to 270 VDC and 28 VDC to supply to the HEMAs, and Hydraulic Power to simulate loads through the servoactuators in the Load Simulator System.

How can the tests be prepared and read?
FLAVIA uses an easy to use system, where users can prepare their own test by mean of an Excel file.
In rows and columns it can be defined different stages for tests, the load pattern of each, parameters of the test, ramps, forces, etc.
This way the test rig allows performing infinite number of customized tests. After the test is finished, the files of the test can be read also easily to study, cross graphs, detect events, etc.
Each stage defined by user is easily recognized in test records, to quickly see the relevant information.

Can other systems be added to the HEMAS TR?
Of course, the National System PXI platform is a scalable environment that allows many configurations in control, acquisition and communications with other systems.
Other systems such us video recording of the HEMAs during tests can be added.

What are the development phases and how the customer can participate and follow the development?
FLAVIA offers a complete, integrating customer in the information and taking decision process.

As first approach, main Work Pachages and tasks of the process are:
0. WP0. KICK OFF Meeting
1. WP1. SRR. System Requirements Review (SRR). The purpose of the SRR is to review the system requirements specification document, to ensure the documented requirements reflect the current knowledge of the customer and market requirements, to identify requirements that may not be consistent with product development constraints, and to put the requirements document under version control to serve as a stable baseline for continued new product development.
2. WP2. Physical process definition. Physical and mathematical analysis of the process. Simulation using models to verify the correct design of the system. Characterization of the system.
3. WP3. Hydraulic System. Design of the hydraulic system, servoactuators and regulation stage.
4. WP4. Sensor System. Selection of the properly sensors and transducers.
5. WP5. Electrical System. Design of the electrical system.
6. WP6. Control and Monitoring System. Selection and configuration of control Hardware. Programming of the control system, communications with COPPER BIRD and development of the user interface.
7. WP7. Mechanical System. Physical analysis of all the mechanics components. Design of structures that must support the servoactuators and HEMAS.
8. WP8. Auxiliary System. Development of all the auxiliary equipment needed for the project. 9. WP9. Management of the consortium. Management and organization of the project. Integration.
10. WP10. PDR. Preliminary Design Review (PDR). The purpose of the PDR is to review the conceptual design to ensure that the planned technical approach will meet the requirements. 11. WP11. CDR Critical Design Review (CDR). The purpose of the CDR is to review the detailed design to ensure that the design implementation has met the requirements.
12. WP12. TRR. Test Readiness Review (TRR). The purpose of the TRR is to review preparations and readiness for testing of software configuration items, including adequate version identification of software and test procedures.
13. WP13. DELIVERY. Installation and commissioning and support stages.
 
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