MOOG FCS HELPS RACK MAKER THULE TAKE VIBRATION RESISTANCE TESTS TO THE LIMIT

AMSTERDAM, June 4, 2008 – When the world's leading supplier of car rack systems decided to invest in a new world-class test facility, it chose Moog FCS for a test rig to simulate the conditions its products are likely to face on all the world's roads. Swedish company Thule, the world leader in Sports Utility Transportation including roof top boxes, roof racks, roof rails and bike carriers, took delivery of the test rig in February 2008, a month before it opened its new test centre in Hillerstorp, Sweden. The facility will support the entire Thule group, which has numerous locations around the world.

Moog FCS supplied a complete test rig solution including a Multi-Axis Shaker Table or MAST and the software modules to run a wide range of tests efficiently and faster. It includes the SmarTEST program for system installation, and FasTEST operator software for preparing and running tests to simulate travelling over various types of road surfaces, as well as operating data acquisition and analysis systems.

Thule chose Moog FCS for several reasons. “We liked their technical solution, they were very easy to work with, and their expertise in testing helped us to develop our approach,” says Thule's technical group manager Fredrik Larsson. “Other potential suppliers we talked to had more experience in this particular application, but their technology was older and sometimes more expensive.”

The two companies first started to work together in May 2006 to develop a unique test system for this application. Thule was looking for a solution to carry out accelerated high frequency vibration testing on its rack systems. Previously, the company had been farming the work out to an external engineering company, but had recently decided to bring the work in-house.

Meeting the challenge of Thule’s new testing generation

Moog FCS delivered the complete test rig including a Multi-Axis Shaker Table or MAST unlike any model currently on the market. The hexapod configuration used by the Moog FCS is the optimum design to achieve test acceleration, attain force or displacement inputs, and reproduce data collected on proving grounds. Rather than using a conventional orthogonal system, which has a table that is moved by actuators mounted on its base and on its sides, the Moog FCS MAST is based on a six-leg hexapod (or Stewart platform).

Moog FCS originally developed the hexapod for flight simulators (Moog acquired FCS in 2005). The hexapod has two equilateral triangular frames set one above the other, offset at 30 degrees. Each apex of the top triangle is connected to the two apexes below it on the lower triangle via Moog actuators. Moog FCS’ proven technology expertise incorporated with the world class performance of Moog actuators, servovalves and digital controllers is essential to providing Thule with a long-lasting solution to meet challenges of today and tomorrow.

High performance, compact, and clean MAST design

Moog FCS developed the HexaTEST MAST over four years, having completed a benchmark study of all competing designs. Like traditional systems, it has six degrees-of-freedom (DOF) – the table moves in the x, y and z axes, with rotational movements over all three (pitch, roll and yaw). “We took what the competition could do in terms of acceleration and displacement as a benchmark, and set out to beat their performance specifications,” says Pim van den Dijssel, Market Manager Test Systems, Moog FCS. “The hexapod is a proven technology but we are the first to use it in this application,” he says. It's quite complex to control each of the individual degrees of freedom, because even a movement along a single axis involves the use of all six actuators. “They all have to be controlled exactly in terms of speed and time, and this is especially tricky when the table has to vibrate at high frequency.” The Moog FCS HexaTEST MAST can vibrate at frequencies anywhere from 0.8 to 80 Hz.

To enable the MAST to run at very low frequencies, the seismic mass incorporates “active level control.” This is because it has a resonant frequency of around 1-1.5 Hz. Air springs under the MAST are automatically activated as the mass begins to resonate, compensating for its motion. The HexaTEST MAST can vibrate with an amplitude of over 140 mm along the x, y and z axes, while maximum rotational displacement is +/- 10 degrees. It supports loads of up to 450 kg. It can run for several days without stopping, which is a period equivalent in real-life use to hundreds of thousands of kilometres.

There are numerous advantages of the Hexapod when compared with traditional designs. The new unit is less costly to maintain than alternative designs. The main reason for this is that, in contrast to orthogonal designs, its six actuators are exactly the same, so the spare part requirements are much less. Moreover, the geometry of the assembly of actuators offers a convenient working height for the operator to mount and inspect the test specimen when no work platform is required.

Showcase testing facility for Thule

“What Thule needs to establish,” says van den Dijssel, “is that the rack or box stays firmly attached to the vehicle and that it stays in one piece. They will be testing the clamping device as well as the rack or box.” Tests are done with the clamping units attached to a section of the car roof provided by the OEM.

The new unit will be a show-case item for Thule as well as for Moog FCS. “They want to show it off to their customers – many of whom are our customers as well. They are very proud of this clean and compact design and so are we.” All hydraulic hoses are embedded in the concrete floor, for example.

Engineers and designers from both companies worked together on the development of the equipment. “It's a completely new area for Thule,” says van den Dijssel, “so they relied heavily on our expertise. They grew into the system as we were delivering it.” Moog FCS worked with Thule to time delivery of the system to coincide with Thule building its new test facility.

In the few weeks that Thule has been using the Moog FCS MAST it has carried out several real-life tests. “We are very happy with it. It's compact, it's clean, and it's very user-friendly,” says Larsson. This is particularly important, given the minimal staffing levels at the facility. Larsson works together with two engineers and two experts in virtual reality test software who develop theCAD models before the company moves to manufacture real prototypes. “With in-house test capability, we will build up our knowledge base. The high versatility of our MAST solution gives us the possibility to develop new tests faster than ever,” commented Thule's Technical Group Manager Fredrik Larsson. “We can't be experts in everything,” says Larsson. “If we do run into trouble, Moog FCS has people close by in Gothenberg. We know we can count on them to quickly come in and help out.”

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