Amplifiers help drive vehicle testing innovation

When, in 1982, suspension design expert Anthony Best set up AB Dynamics the business was predominantly centred around consultancy work. It wasn't until the early 1990s, and the decline in the UK automotive industry, that the company really began the journey that has seen it evolve into the specialist manufacturer of advanced vehicle testing systems that it is today.

Drawing on its many years of expertise in vehicle suspension, in 1995 the company delivered its first Suspension Parameter Measurement Machine (SPMM), a kinematics and compliance machine which still accounts for a large proportion of its business.

Repeatable testing

With the SPMM, AB Dynamics had come up with a machine that was not only accurate and quick, but was reliable and provided highly repeatable testing – and it was partly this characteristic of repeatability that prompted the company to turn its expertise to the on-track testing arena.

Although using a human test driver is undoubtedly still an important part of testing for any new automotive model, even the most experienced driver will be subject to fatigue and physical stress, which can have a detrimental affect on repeatability.

"Typical vehicle dynamics testing requires a test driver to put a step or sinusoidal inputs into the steering, if you can make those inputs more repeatable to get the same every time, it's possible to collect better quality data about how the car handles," says Mat Hubbard, Technical Director at AB Dynamics.

Addressing this need, the company developed its first steering robot in 1997, which was soon followed by pedal robots for the brake and clutch. As a result, the speed of the car being tested can be very precisely controlled. Taking this a step further, in 2001 the company took on the challenge of developing a system by which a vehicle could steer itself through a defined path using GPS.

"In 2007 we took the driver out of the car completely and we now sell systems for fully driverless testing, either for very dangerous tests or where the driver is only allowed to drive for a limited time because of fatigue," says Hubbard.

As today's car designs become more sophisticated, in addition to needing data on how a vehicle will handle in different situations, automotive manufacturers are increasingly testing complex safety systems, known as advanced driver assistance systems (ADAS).

"A lot of our early robot systems were all about looking at vehicle dynamics – how the car drives, how the brakes work, how the steering works," says Hubbard. "Now many of our systems are going into the active safety markets – it's all about cameras and radars on cars. Does a car stop automatically if a pedestrian comes across the road? Will a car stop automatically if another car comes into the road? You need tools to be able to evaluate this."

Guided Soft Target Vehicle

And that's where AB Dynamics' latest product development fits in. Described by Hubbard as "essentially a very expensive, very big remote controlled car", the Guided Soft Target Vehicle (GSTV) has a 'car-sized' footprint, but is just 125mm high. The unit is built around a chassis originally developed by US-based company, Dynamic Research.

Although if you spotted the GSTV at a distance, you could be forgiven for thinking it was an over-sized tea tray, once a foam 'body' is fitted it starts to looks like a real car.

"Basically, it provides a way of having collisions between the vehicle you are developing and another car without actually damaging either vehicle because the foam breaks apart as you drive through it," says Hubbard. "The radar signature of a real vehicle is 'faked' by the materials used in the foam cover."

If a collision does occur, the car being tested simply drives over the GSTV without being damaged. This is in contrast to testing using two cars, where if a collision does occur there is the costly potential of both vehicles being written off.

A very accurate GPS system, in both the GSTV and the car being tested, combined with user friendly software enables users to pull in a Google Earth image of the testing track and 'draw' the path they want both vehicles to follow, controlling in sections and specifying speed, acceleration, deceleration, etc.

Achieving speeds of around 80km per hour, the GSTV uses an LiFePO4 lithium ferrous phosphate power pack with 230V DC bus and three Elmo amplifiers – one that drives the steering motor, a Solo Trombone; and two Drum HV amplifiers that drive the rear axle. The Elmo amplifiers were supplied by Bournemouth-based Motion Control Products, a motors, drives and mechanical components supplier for advanced motion control and automation since 1994.

"We've used amplifiers from various companies in the past, but the Elmo products were selected because of their high power density – for the size we get lots of power out of them, which is important when you look at the tight space we need to be able to fit them in. They've also proved to be very robust," says Hubbard. He also cites AB Dynamic’s relationship with Motion Controls Products and the supplier’s extensive range of drives and motors as contributing factors.

Reliability has also been a factor in AB Dynamics' decision to specify the drives from Motion Control Products as well as excellent pre- and post-sale customer service. Although there might be cheaper options available, cheaper is not always better, especially when 95% of your products are exported, as Hubbard explains.

"If we ship a product to China, getting that product back in the event of a technical issue is extremely problematic – so the cost of saving, say, £100 on a drive is completely outweighed by the fact that it might cost £5000 to get a product back, repair it and then ship it back to the customer. Because of this we tend to stick with products that we have grown to trust, like the Elmo amplifiers."

AB Dynamics also uses Elmo products in its pedal and gear change robots, MCP and Elmo are working with AB Dynamics to produce a custom bespoke drive to meet its exact current and voltage requirements for the next generation GSTV.

MCP sales director, Andy Holmes, says: "The Elmo range of servo drives are unique in the industry and are generally coupled with our extensive range of matching motors, gearboxes and/or actuators. The combination of MCP’s strong sales, technical support and quality motion based products enables our OEM partners to become successful in their specific industrial application.”   

To see AB Dynamics’ products in action for yourself, visit the company’s YouTube channel at http://www.youtube.com/user/abdynamics

For more details on Elmo’s range from Motion Control Products, visit www.motioncontrolproducts.com/drives