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13/05/2010
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DC motors with an exceptionally long service life and low energy consumption are helping to power robots monitoring the ecosystem of the Amazon.
 Christened 'Chico Mendes' in honour of a rainforest activist killed in 1988, the robot was developed with the help of the latest submarine and drive technology in a joint project between the sociological research institution Piatam (Potential Impacts and Environmental Risks of the Petroleum and Gas Industry in the Amazon), the Brazilian state university and Petrobras.
In developing the robot, it was particularly important to ensure that it minimised any possible damage to the very nature it is supposed to be protecting. Such specifications posed a particularly difficult challenge in drive technology terms.
'Chico Mendes' has to battle through mud, water and swamps with the help of electric microdrives. This involves eight of Maxon Motor's DC motors delivering a high performance in a tiny space. Their low energy usage is one of the key reasons why they were chosen for the project. The environmental robots are driven by solar power in an initial phase and, with an efficiency of over 90%, Maxon's motors are ideally suited to this type of application.
Maxon RE 40 motors feature in all four of the robot's wheels, while another four Maxon RE 35 motors are housed in the adaptive suspension, and automatically adapt to conditions depending on the terrain and water conditions in the rain forest. Two planetary gearheads, measuring 42 and 52 millimetre across, provide the requisite torque for the vehicle which is 1.5m long, 2.2m wide and 1.2m high.
The environmental robot's high dynamism requires equally dynamic electronics to control the DC motors. All operating DC motors can be accurately controlled using Maxon Motor's digital positioning controller EPOS 70/10. EPOS stands for 'easy-to-use positioning system'. All EPOS controllers can be networked according to CANopen standards. The drives are programmed according to IEC 61131-3 standard using a simple software tool with graphic user interface.
Key to the DC motors' drive is Maxon's patented ironless winding system. The rotor of a conventional DC motor comprises an armature iron with inserted spool segments. This rotor is encumbered with a large moment of inertia, high inductance and therefore a long start-up time. In the Maxon DC motor, however, a pure copper winding rotates in the magnetic field.
There are a number of benefits to ironless winding ¬– particularly in an application of this sort. There is no magnetic detent, while the low mass moment of inertia means it is able to offer rapid acceleration.
Designed specifically for applications for use in high-tech applications in battery-powered appliances, the motors use brushes made of precious metal that ensures constant and low-contact resistance with the commutator – even after a prolonged standstill. It also means low start-up voltages and minimal electrical interference.
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Author
Tom Shelley
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