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Southern Manufacturing & Electronics

Farnborough, Hants(GU14 6XL)

11/02/2020 - 13/02/2020

Southern Manufacturing and Electronics is the most comprehensive annual industrial exhibition in the (more)

Driving the ultimate in freedom of movement

Driving the ultimate in freedom of movement The dream of flying has fascinated people since time immemorial. Airstage, an offshoot of Effekt-Technik GmbH, uses this appeal in order to enthral people with hovering models. Each object is different and demands different drive concepts. What they all have in common, though, is that the drive must be very compact and be able to transform battery power into motion with high efficiency.

Consequently, the model specialists work with motors and gearheads from microdrive expert Faulhaber, whose products are available in the UK from EMS. The distinctive aspects of the flying objects and the drive technology ideally complement each other in this area.

The experts at Airstage have a wealth of experience in designing a wide variety of drive concepts. It all started with Rainer Mugrauer, who in the 1990s was a pioneer in 'slow flyer' development. The primary factors for effective flight operations were the same back then as they are today: the greatest possible performance with the lowest consumption of the scarce battery capacity and the quickest reaction to control commands. Bell-type armature motors with brushes are particularly well-suited for this purpose. With the compact drives it was possible to propel both the earlier slow fliers as well as the current, distinctly more sophisticated models.

While objects such as the flying 7 Series BMW are purely for show purposes, bionically driven models that mimic nature also support the training of students and engineers. Airstage is a partner of the Bionic Learning Network, a research association set up by Festo in 2006 to develop new ideas, solutions and technologies, and providing an opportunity to 'think outside the box'. By the same measure, natural principles and propulsion concepts are put into effect in technical applications and in industrial practice.

Such future concepts include the AquaJellies - artificial jellyfish that float in water with air-filled, pressurised vessels and that propel themselves with their tentacles just like real jellyfish. An internal logic unit monitors the battery status and autonomously leads the jellyfish back to dock on the charging station. Its counterpart is the 'flying' jellyfish, which works with a helium-filled balloon as its lifting body. The 'drive ballast', which is kept as light as possible, consists of two lithium polymer batteries and the central drive unit for the tentacles. A pinion gear, connected with eight spur gears, sets the tentacles in undulatory motion by means of cranks. The control is handled by two servomotors that shift the internal centre of gravity.

Even more exquisitely constructed is the flying dragonfly - the BionicOpter. With a total flying weight of just 175g and an impressive wingspan of 63cm, it can be steered through 13 degrees of freedom and has even mastered hovering flight - just like the real dragonfly. Then there are flying dolphins that cruise silently through a 'sea of air'. Because the models hover over the heads of the spectators, the utmost in reliability and rapid response to control commands are required. As aircraft that are lighter than air behave sluggishly, the pilot's commands must be executed quickly. Intermittent overloading of the drives allows precise, high thrust impulses, while avoiding the excess weight of larger motors that would negatively impact the model aircraft the entire time.

"Essentially, for us the advantages of the DC-Micromotors from Faulhaber lie in their high efficiency and excellent intermittent overloading capacity, combined with smooth-running operation, the uncomplicated actuation and easy interference elimination," explains Mugrauer. Bell-type armature motors have no cogging whatsoever; the precious-metal commutation guarantees a gentle start-up even at the lowest voltages. As a result, most models can offer weight savings through operation with only a 3.6V lithium battery. With diameters of 13-17mm and

12-27g of mass, a power output of approximately 1-3W is attained. Planetary gearheads appropriate to the diameters increase the torque as needed and reduce the speed, for example for operating the jellyfish tentacles.

If especially compact drives are needed, flat micromotors with integrated spur gearheads are well suited. With an overall length of just 19mm - including the gearhead, and a diameter of 26mm, they stake out a unique position in the microdrives market.

What all of the drives have in common is the ease of speed control by simply varying the input voltage. Thus, application-specific, ultra-light electronics control the motors of the model aircraft. As the precious-metal commutated motors generally have only a very low level of EMC emissions, wireless compatibility isn't a problem. Any potential brush wear is negligible for the models. Most of the model aircraft are only in operation for a relatively short time, and even with the AquaJellies, which swim around in basins for hours at trade shows, in practice the brush wear is insignificant.

Despite the trend towards electronically commutated drives, microdrives with brushes still offer specific advantages, with the bell armature motors offering cogging-free, silent operation, even at the lowest operating voltages. This makes them indispensable not only for model aircraft, but also in research, and in measurement equipment for medical technology, and even in outer space.
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