Compact servo drives key in collision avoidance testing
Compact servo drives are providing the driving force for AB Dynamics’ (ABD) fastest, most robust test rig yet. This enables the company, which specialises in testing systems for the automotive industry, to increase the speed and versatility of its Guided Soft Target (GST) vehicle.
The human-assisted and fully automated collision avoidance systems currently being developed by the motor industry require multiple tests to mitigate collisions from any direction at any speed. ABD’s internationally adopted GST allows vehicle manufacturers and test houses to gather extensive data from highly repeatable experiments that are used to improve vehicle safety and reduce accidents.
The GST comprises a 125mm high flat platform that carries a foam car body which has the visual and radar appearance of a real car. Upon collision with a conventional vehicle under test, the GST’s foam body safely breaks apart on impact, allowing data to be gathered on the performance of the test vehicle’s sensors, and collision avoidance and mitigation algorithms.
The platform has sloped sides and air-filled suspension to further reduce its vertical profile to the equivalent of a small speed bump. This ensures no damage is done to either the GST or the test vehicle, and that the GST comes to a quick stop when driven over.
The GST’s low height and small wheels make achieving high speeds a challenge. ABD turned to Elmo Motion Control to find a solution that would deliver sufficient power to propel the GST at up to 100km/h, without compromising on size. Two high power density, intelligent, resilient servo drives from the Gold Drum series are used in the platform. The drives provide an output of 100A within a 75mm tall housing, allowing the GST to travel at motorway equivalent speeds while minimising the risk of collision damage.
An Elmo Gold DC Trombone servo drive is used to handle the steering on the GST. Even the most skilled human driver will struggle to perfectly replicate the same drive twice, and so Elmo and ABD have automated this aspect. The lithium ion phosphate batteries used to generate a 240V DC bus in the GST allow it to be driven for several hours between charges, giving more testing time.
Mat Hubbard, ABD engineering director, says: “We are continually looking for ways to improve the GST’s acceleration and top speed to better simulate driving scenarios. Drive size is also an issue, as the components we use determine how small we can make the platform. Elmo is the only company that can offer sufficient power density to deliver the speeds we require.
“We have adopted Elmo motor drives across our track testing products and they have proved to be extremely reliable, which is important given that 98% of our sales are to overseas customers. We’re also currently working on a new product that is only feasible due to the availability of Elmo’s Twitter drive, which has unparalleled power density.”
Elmo’s Rob Greenhalgh adds: “We are pleased to have helped ABD to break through the 100km/h barrier. We are currently working on improvements to increase the speed further. This ongoing project showcases the superior power density and ruggedness of our drives, and is one of the many unusual applications for which we can provide advanced motion control solutions.”
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