A device for the accelerated testing of highways or airport runways developed in South Africa, features modular AC drives from Control Techniques.
The Accelerated Pavement Testing device (APT) – the MLS10 - produced by MLS Test Systems of Stellenbosch, features contactless linear induction motors eliminating drive train fatigue and wear. The MS10 can apply more than 100 000 wheel loads per day, each equivalent to a 12 ton axle load, onto a 3,6 metres long stretch of road. The typical speed of the wheels is 6 m/s (22 kph).
The machine structure is a space frame 10 metres long, inside which four wheel bogies, each fitted with dual 295/65 R22.5 truck tyres, run in a vertical loop. The wheel bogies, linked together in an endless chain, are guided by two concentric sets of steel guide rails. Dual, counter-rotating, 250-mm diameter steel guide wheels on the bogies run between two sets of guide rails. Whilst a bogie runs along the bottom section of the rails, the tyres are pushed down onto the pavement by an hydraulic and compressed nitrogen gas system. In addition, whilst running, the entire machine can be translated sideways, about 500 mm to each side, on computer-controlled hydraulic powered slides to simulate the lateral distribution of the wheel paths of different trucks on a highway.
The machine utilises linear induction motors (LIMs) from Force Engineering in the UK to drive the bogies inside the machine and these are controlled by specially configured modular Unidrive SPM AC drives. LIMs, with their no-contact characteristics and their high thrust and acceleration were the perfect choice for this application, but they do require control by specially configured inverter drives. Control Techniques has worked closely with Force Engineering for many years to produce the optimum control characteristics for LIMs.
The drives give a soft-start action, maximum speed being determined by winding design and supply frequency whilst torque and speed is controlled in several ways. Control Techniques’ on-board second processor technology was used to run the dedicated LIM control software solution. The software resides in an SM Applications Plus module which requires no panel space as it is fitted into the interior of the Unidrive SPM drive. The machine I/O is networked to the SM Applications Plus processor by means of CTNet, Control Techniques’ own high-speed network and Beckhoff remote I/O cards. In this way the designers managed to network large quantities of field I/O at very high communication speeds. An operator interface is used to set up the machine operating parameters as well as provide system diagnostics and fault reporting.
For more information contact Bill Tedd, Control Techniques, +27 (0)11 462 1740, [email protected], www.controltechniques.com
| Tel: | +27 11 462 1740 |
| Fax: | +27 11 462 1941 |
| Email: | [email protected] |
| www: | www.controltechniques.com |
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