Maneuvering in outer space and underwater
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Motion on Mars
Maxon Motor, Switzerland, has delivered motors to nearly every space vehicle that has moved around on Mars and the moon. These motors are extremely small, lightweight, and power efficient because of their patented design, which is created through a patented production process. Maxon’s micromotors use an ironless rotor with rhombic winding. Located on space vehicles’ wheels and other mechanical parts, these motors do nothing unless told to move in a coordinated manner.
The world’s leading high-precision drive systems supplier introduced the second generation of motor management and position control at the Hannover Industrial Fair earlier this April. The company makes motors from 1 W (0.25" diameter) to about 5 kW. Maxon’s EPOS controller family is optimized for smaller motors up to 700 W, which covers most applications.
Small and mechanically robust, the DSP-supported EPOS2 controller (Figure 1) can be installed near the drive or motor in decentralized applications. A typical EPOS is 105 mm x 83 mm x 24 mm (4" x 3.5" x 1"). Communication with up to 127 nodes or axes can be achieved via the CAN fieldbus, which is efficient in real time and often used under different names (J1939, NMEA 2000, ISO 11783, 11898, and 11992, Smart Distributed System, and DeviceNet) in many passenger cars, trucks, and farm tractors worldwide.
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Figure 1 (click graphic to zoom by 2.1x) |
The EPOS controller is an SBC with local I/O (analog and digital) using a 32-bit DSP to process complex mathematical algorithms in real time. I/O ports are available potential-separated (optocoupled) for electrical isolation and protection against electromagnetic interference. In Interpolated Position Mode, EPOS2 can move synchronously and control coordinated multi-axis movements. The Regulated Tuning function helps optimize current, speed, and position control at installation time. The controller also has gateways to USB and RS-232. Control cycle times are not a problem even for very small and highly dynamic motors.
EPOS-controlled motors power the Telerob vehicle (Figure 2), a remote-controlled robot from Telerob, Germany, that searches for explosives in buses, aircraft, or railway cars (see the Embedded Technology in Europe column in the November 2007 issue of Embedded Computing Design). EPOS controller SBCs control chain drive motors, robot arms, turrets, and other moving elements in real time. The Telerob is radio-controlled from a safe distance.
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Figure 2 (click graphic to zoom by 2.0x) |
Maxon has partnered with NASA since the first Mars landing in 1997. The Mars Pathfinder was fitted with 11 small Maxon motors. Spirit and Opportunity, NASA’s twin rovers that landed on Mars in January 2004, each have 39 Maxon motors. Maxon also supports Phoenix, the most recent Mars project that successfully landed on the Red Planet on May 25. The probe Phoenix Lander (Figure 3, courtesy of Corby Waste, Jet Propulsion Laboratory) will search for visible water and dig for traces of water with a robot shovel. A more than 2 meter long robot arm will penetrate the thin layer of dust and rubble to lay bare the Martian ice-rich soil. The researchers at the University of Neuchatel, Switzerland, will use a special microscope to analyze the soil samples and assess if primitive life forms can be found beneath Mars’ surface.
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Figure 3 (click graphic to zoom by 2.2x) |
Mini submarine contest
The Student Autonomous Underwater Challenge – Europe (SAUC-E) is a competition in which students from across Europe design and build Autonomous Underwater Vehicles (AUVs) to attempt navigation through an underwater assault course. The course varies from year to year but typically consists of gates, drop targets, surface zones, and many other obstacles. The competition aims to advance AUV technology and provides students the opportunity to gain industrial links.
A student-led team from the University of Southampton, United Kingdom, triumphed at last year’s SAUC-E, winning both the overall competition and receiving an award for Innovation in Autonomy. Two U.K. government organizations – the Defence Science Technology Laboratory and the Research Acquisition Organisation – hosted and sponsored the competition, respectively. Commercial 0sponsors included QinetiQ, Kontron Europe, and other companies.
The victorious Southampton team used three watertight USB cameras, which deliver better accuracy than echolocation or other search systems, and the dual-core 986LCD-M/M-ITX, a 17 cm x 17 cm (approximately 7" x 7") Mini-ITX board from Kontron. Figure 4 shows a view inside the team’s AUV, courtesy of the University of Southampton.
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Figure 4 (click graphic to zoom by 1.9x) |
To compete in SAUC-E, AUVs (mini submarines) must operate autonomously without any control or communication to or from the outside world. Batteries must last for an extended period of time, and processors must handle complex algorithms and three video streams in real time, thus presenting heat dissipation difficulties. Pressure sensors and compass and inertial navigation systems control the underwater course.
Teams that participate in this four-day event gain real-life engineering experience as they design and build vehicles capable of completing a series of underwater tasks without any human intervention. Points are awarded based on the final run, technical documentation, presentations, and innovation. The 2008 competition will be held this July in Brest, France, along the Atlantic Coast.
