USA federal agencies continue to invest in these technologies by funding projects that improve their performance and efficiency. This work will not only shape the future of these application areas, but will also have significant crossover into the commercial marketplace.
Astronauts freed up
During future space exploration missions, autonomous robots are expected to free astronauts of routine and repetitive tasks such as simple inspections, maintenance, scouting terrain and gathering field samples. Today's earth-bound technologies play a key role in the development and enhancement of these robots. One recent example is Thibodeaux, a four-wheeled autonomous mobile robot being developed at NASA's Johnson Space Centre for use in lunar and Mars missions.
Roughly the size of an all-terrain vehicle, Thibodeaux is designed to pre-scout areas for astronaut missions, and to carry heavier payloads for construction and in situ scientific tasks. The robot is directed by astronaut voice commands, and can be driven remotely using wireless communications and onboard video cameras. Four onboard, sealed lead-acid batteries provide power.
Inverted architecture
Currently reaching speeds of only 5 kph, one 1,8 kW electric motor is being outfitted into each wheel to enable speeds up to 50 kph. Originally designed for electric scooters and motorcycles with top speeds up to 60 kph, each motor will currently be limited to produce 180 Nm of peak torque for the NASA project.
The permanent magnet, DC brushless motor has an inverted architecture which means that the rotor surrounds and rotates around the centre mounted stator. The stator consists of a series of independently controlled electromagnets driven by a proprietary power electronics module. Conventional steel laminations are used as the stator core material. The rotor has rare earth-based permanent magnets and housings that are arranged in a proprietary design. Connected to the power electronics, a digital signal processor activates the electromagnets by analysing motor position, desired torque, and the electrical characteristics of the energy management system powering the motor. Patented adaptive algorithms adjust the current and excitation sequence of each electrical phase.
Patented software
"One of the key things about our technology is the patented software used in the integrated motor and control. It allows the motor to reconfigure itself within nanoseconds," said Tim Hassett, general manager of Motors for WaveCrest Laboratories in Dulles, Virginia. "The software senses load such that it reconfigures the motor and allows it to run at an optimal performance while properly dissipating heat. Integrating the motor and control also eliminates electric and magnetic field (EMF) issues and shortens cable lengths to reduce line chatter.“
Additional customisation
Additional customisation is necessary for the NASA project, mainly because Thibodeaux will be an all-wheel drive robot requiring communication among four wheels, whereas the scooter only had a single wheel on the back drive. While specifics cannot be provided due to the nature of the work, software will be altered so that it works with the robot's existing vehicle control and some of the components on the power board will be changed to better suit the application. According to Hassett, alterations to the housing or anything mechanical will not be necessary.
For more information contact WaveCrest Laboratiories, www.wavecrestlabs.com
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