Stepper motors: the sky is not the limit

Clear, unjittered pictures and film shooting best succeed with the use of a tripod. Even if only taking photos whilst moving slowly, the picture may appear unclear. The distortion becomes more extreme if the camera is mounted in a vehicle or even an aeroplane. Photographic devices rely on additional stabilization ­especially in small aeroplanes as they provide little automatic damping due to their low permanent weight. Here, a gimbal-mounted, gyro-stabilized mounting platform is a perfect solution. However, weight is an issue, simply because the mini aeroplane or reconnaissance drone still has to be able to take off. Micromotors with adapted transmissions provide the solution for easy, reliable gyro-stabilization.

The use of unmanned aerial vehicles (UAVs), also known as drones, is often favoured in the military field to exercise the dangerous job of reconnaissance. One drone costs 2 to 5 million euros. However, smaller light and ultra-light drones can be acquired for much less – a few tens of thousands up to one hundred thousand euros. This is why other users such as ­cartographers, archaeologists and various industrial exploration concepts ­increasingly rely on these flexible reconnaissance planes. Unfortunately, the combination of small size and good value also translates into a low load capacity. Apart from the camera, the most important component for clear photos during a flight is the ­stabilized mounting platform. Normal ­stabilizers based on gyro-stabilization are too heavy for small aircraft. The Hood Technology Corporation, from Hood River in Oregon, USA, has developed a new lightweight design for this specific ­purpose. In cooperation with the drive specialist MicroMo, the North American FAULHABER Group ­company, it was ­possible to adapt gyro-stabilization for UAVs.

Weight reduction

In order to enable mobile drones, small aircraft or small helicopters with an average weight of only 15 kg to carry out their tasks for several hours, they must be able to remain airborne for a lengthy period of time. The more fuel required, the ­lower the overall capacity in terms of payload. Therefore, heavy gyro-stabilized ­mounting platforms are therefore simply out of the question. Modern CCD cameras are small, light and only require little electricity, which is ideal for the miniature aircraft. Thanks to significant progress made ­within the area of mechanics, too, the ­latest mounting platform to have been developed now boasts a considerably lower weight. Small mass combined with high velocity enables damping which is just as good as that of conventional heavy­weight “gyro-steamers”. Hence, the first mounting platform with a weight of as little as 500 g provides a stable basis for a load capacity of up to 200 g. Thanks to its gimbal-mounted attachment, the inter­n­ally fitted camera guide can be moved for panning – independent of the stabili­zation. Power supply and data transfer operate via smooth-running collector rings. Miniature stepper motors ensure the required homogeneous gyro movement and sensitive controllable camera guide movement.

Step-by-step to engine speed

When it came to choosing a drive source for stabilization, only micromotors were among the possible candidates. The minia­ture stepper motors with an absolute encoder proved the best possible option for position feedback. If the command “move on one step” is given, the motor immediately moves on one step further. Within this context, friction in relation to the motor step output is negligible. If step commands are given in rapid succession, the motor effectively rotates continuously. When in operation, this “mighty midget” moves at about 10,000 steps per second, thus generating continuous motion. The high velocity is then reduced by a special, pre-loaded 1:200 transmission which is therefore backlash-free. This facilitates an unjittered angle speed of 90°/s on the rotation axle output end. The continuous engine speed stabilizes the payload perfectly with oscillating weight and the gimbal-mounted attachment.

Catching instead of landing – the drone is threaded into a vertical rope with one wing, thus not requiring a runway
Catapult take-off – when taking off, the drone and the camera platform are exposed to acceleration of 35 G