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Design and development of an Adaptive, Smart and Eco-efficient Test Bench for synchronized testing of linear actuators in the aeronautic sector

Final Report Summary - ASE-TB (Design and development of an adaptive, smart and eco-efficient test bench for synchronised testing of linear actuators in the aeronautic sector)

Executive summary:

The ASE-TB project has designed, manufactured and tuned an innovative test bench for linear actuators that will be capable of conducting synchronised tests on two linear actuators of the same type while applying different loads on them. This test bench has been based on a modular and adaptive concept by integrating easily exchangeable hydraulic and mechanical components with sensors and control strategies that will allow automatic and autonomous safety controls during endurance tests.

This innovative concept of actuator test bench has been based on a multi-disciplinary approach that has considered modularity, assembly easiness and process safety in an integral way.

With the aim of designing, manufacturing, tuning and delivering the innovative ASE-TB test bench for linear actuators, Tecnalia has tackled multidisciplinary research activities that have been grouped into seven Work package (WP)s: WP1-4 as Research and technological development (RTD) activities, WP5 as demonstration activity, WP6 as tther activities and WP7 as management.

Project context and objectives:

One of the major challenges in the aeronautic sector is to conduct endurance tests on critical components and actuators in an automated, safe and sustainable way by means of appropriate test benches that include actuating, sensing, monitoring and supervising capabilities.

In this respect, there are several European research projects that have tackled this issue as a means for validating the developed components as well as for comparing and adjusting models of components as of their production processes.

As reference, the European project 'Predictive methods for Combined cycle fatigue (CFF) in gas turbine blades' (PREMECCY), funded within the Sixth Framework Programme (FP6), developed a test bench for validating in an experimental way innovative predictive methods for estimating the CCF of gas turbine blades in the aeronautic sector. Inasmet-Tecnalia developed the concept of the multiaxial PREMECCY test bench, with which motor builders for the aeronautic sector will be able to conduct fatigue endurance tests combining both high frequency loads and high temperature conditions. Moreover, on the built and tuned test bench, Inasmet-Tecnalia conducted tests with INCONEL 713LC blade like test tubes. The main innovations of this PREMECCY test bench are:

i) the integration of a thermal chamber with temperature control;
ii) a graphic user interface with which the user can configure, read and store the results of each individual test;
iii) a multi-axial actuation, combining axial and orthogonal load actuations;
iv) a high-frequency load capacity, that has reached the value of 1 KHz;
v) advanced strategies for cycle counting based on the treatment of poles and zeros.

On the other hand, in ECOFIT European project 'Eco-efficient machine tools' by means of radical mass and energy needs reduction), that was led by Fatronik-Tecnalia, the coordinator of this project, the consortium developed an innovative test bench for validating active damping strategies based on both inertial actuators and filters in the speed-loop. Within this view, the test bench consist of two linear actuators, one that is based on a ballscrew feed-drive and the other one based on a linear motor, on which synchronised tests with different loads can be conducted on both drives.

The main innovations of this ECOFIT test bench are:

i) the modular concept of the bench components, what allows the users to allocate the linear scales in different positions and thus close the position control loop in different slide points;
ii) a control strategy based on flexible multibody models, that users can customise with ease by combining parameterised models of the test bench components.

Tecnalia, based on the experience of these mentioned two state-of-the-art test benches, has developed ASE-TB test bench, fulfilling the following objectives:

- The developed test bench (CLTB) validates the feasibility of an electrical synchronisation of electrical actuators with high accuracy.
- This CLTB is capable of providing counter-loads for 2 actuators at the same time with the ability to apply different loads for each actuator. Additionally, the CLTB is able to be used with a single electrical actuator under test.
- This test bench assures a safe test running without an operator during endurance tests.
- The CLTB is designed to apply an adjustable load from 35 000 to 35 000 N on each actuator on the complete stroke. The load is adjustable independently on each actuator at every position.

Project results:

In the following lines, the result of the ASE-TB project, in fact the counter-load test bench is described.

The architecture of the CLTB is made up of two mechanically independent carriages, on which the actuators are tested.

The main components are listed below:

1. Fixed carriage / table
2. Movable carriage / table
3. Actuator mounting beds
4. Control interface (Does not need to be on-board. The CLTB can be remotely operated through a network connection)
5. Hydraulic cylinders
6. Hydraulic auxiliary elements
7. Electric cabinet

The CLTB is totally autonomous, except for an electrical power source. One of carriages, referred from now on as CLTB2, has all the electric and hydraulic servitudes mounted on-board.

Approximate dimensions of the carriage are 2 400 (+1 050 of the cylinder) x 800 x 1 400 mm.

The second carriage, referred as the moveable carriage, will be displaceable to accommodate different flex-shaft sizes. Approximate dimensions of the carriage are 2 350(+1 050) x 400 x 1400 mm. The width of the CLTB when fully retracted is shown below:

The distance between the carriages can be varied between 0 and 2 meters. The CLTB will be designed to be as compact as possible.
The counter load is applied through hydraulic cylinders. Both cylinders have internal mechanical stops and a position sensor.
A hydraulic system has been chosen for driving the actuator test bench. Hydraulic systems are capable of working with frequencies up to 200-400 Hz, while other systems, as electromechanical solutions, cannot reach these frequencies. Therefore, under dynamic precision and reaction time points of view a hydraulic system is the best solution. High loads application is another key factor to select a hydraulic system. High dynamic test benches are mainly hydraulic.

The hydraulic system of the test bench consists of the following main parts:

- hydraulic power unit;
- accumulators;
- double rod cylinders;
- servo valve.

The cylinders are sized to achieve the maximum loads specified in the requirements. Two identical cylinders are projected, each one able to apply the maximum load. This maximum load can be applied in tensile and compression working modes. The cylinders are designed in compliance with ISO 6020/1 standard. They are front round flange mounting double rod cylinders.

The servovalves (one per cylinder) permits to control the movement of the cylinders with the accuracy specified in the requirements. But, the hydraulic system comprises also some other secondary components as air-cooler, electrovalves, check valves, filters.

The main process control unit of the CLTB is a MOOG controller and data acquisition system. This acquisition system is capable to read the sensors inputs at a frequency of 1 000 Hz. It has been directly design to perform hydraulic control.

Two load cells will be installed, one for each cylinder. The accuracy of the load cells will be 0.1 % of the measuring range (full scale), an accuracy of 50 N for a 50 000 N maximum load cell.

Two position sensors will measure the cylinder stroke. These sensors will use digital electronics to adapt its output signal. The precision of the sensor will be of 0,1mm.

To prevent incidents related to the security, some safety systems will be implemented:

- emergency stop button;
- enclosure with limit switch;
- oil temperature sensor;
- relief valve to avoid overpressures in the hydraulic circuit;
- minimum and maximum stroke limiter.

All these safety systems will be connected to the main unit process. If some of them are activated the process will stop, will show and alarm to the user and will reduce the hydraulic pressure.

Potential impact:

This test bench that the ASE-TB consortium has developed along the project will have a remarkable impact on the competitiveness position and sustainable development of the European aeronautic industry because it will contribute to:

3.1.Contribution of ASE-TB test bench to enhancing the competitiveness of the European aeronautic industry

- Reduction of time and costs associated to testing of linear actuators: 1. The modular concept of the test bench allow having two testing positions, so that while one linear actuator is tested, in parallel, other linear actuator may be placed or removed, increasing thus the productivity of the testing processes.
2. The modular conception of the test bench will allow easy adaptations to future variations in the requirements of the testing processes, reducing thus the maintenance costs associated to assembly and disassembly for bench upgrading operations.

3.2 Contribution of ASE-TB test bench to enhancing Employment in the European Aeronautic Industry

The ASE-TB Bench will assure that the linear actuators will fulfil endurance tests with a high level of reliability, increasing thus the productivity of the personnel involved in those endurance tests. As a conclusion, the ASE-TB will maintain the employment level of the European aeronautic industry while enhancing their competitiveness level.

3.1.3 Contribution of ASE-TB test bench to enhancing the sustainability of the European aeronautic industry

- Improvement of working conditions of testing operators: During the detailed design phase, Tecnalia has designed a safety control system which will assure a safe and proper running of the endurance tests.
- Reduction of environmental impact associated to linear actuator testing: The modular conception of the ASE-TB test bench will allow its easy upgrading for matching to new requirements in the future, and in addition, will allow the re-use of their components in other benches or in other mechatronic systems once the life span of the test bench have finished, reducing thus the environmental impact associated to test benches.

Main dissemination activities

Tecnalia will play an important role in the dissemination of the results of ASE-TB project. Tecnalia will take advantage of their multiple industrial connections, to explain the results of the project, respecting the confidentiality agreements with the ITD topic manager. This technical and research corporation will also study the application of the knowledge developed in the project to different sectors.

In fact, the dissemination of the results will be addressed towards the following sectors:
- aeronautics (mainly aircraft engine and actuators manufacturing companies);
- aerospace (companies which manufacture actuators);
- engineering companies which design test benches for validation or certification of products.

Exploitation of results

The exploitable result of ASE-TB project is the counter load test bench that has been developed along the project. Its purpose is to conduct synchronised tests on two linear actuators of the same type while applying different loads on them.

Tecnalia foresees different ways of exploiting this developed test bench:
- Selling the test bench to an aeronautic company interested in this validation mean. This is a possibility that would be explored after the end of the project and by Tecnalia; in fact the contacts and meetings that are being held with aeronautic companies in the context of dissemination activities can be a base for exploring this possibility.
- The test bench could be used by Tecnalia, for selling testing services to aeronautic companies. This activity would be performed after the end of the project.
- The test bench could also be used as a demonstrator of technologies that for being too innovative and risky, have not been implemented in the ASE-TB project, for instance, non-linear control strategies.

List of websites: Contact persons in Tecnalia: Malen Cano: malen.cano@tecnalia.com , Joseba Lasa: joseba.lasa@tecnalia.com