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As seen in Business Geomatics: The Art of Harmonization

As seen in Business Geomatics July 2018 issue

Read the article in English below or view the original article in German by visiting the Business Geomatics website here. 

For two years, the objective of Microdrones has been to create solutions for various surveying, inspection and geomatics applications. In the development of solutions, it is important to maintain an optimally harmonized overall system.

A maximum flight time of up to 45 minutes, high flight stability and resistance to wind and weather: Microdrones is known for its efficient flight platforms. After all, the company founded in Siegen is regarded as the inventor of quadrocopters and has never lost sight of its goal of technology leadership in its company history. But do the flight parameters alone suffice for continuous success in the highly competitive drone market? Business Geomatics raised this question to the company, which currently has more than 120 employees worldwide, with 60 of those employees in Germany, many of who  are employed in the field of research and development.

In a nutshell, the answer is a decisive “as well”. "Flight time is an absolutely critical factor for the procurement of drones, whether in the field of surveying or inspection," Michael Pontz, Development Manager (CTO) at Microdrones. To this end, lightweight construction, high mechanical quality, high rotor efficiency and advanced aerodynamic capacities are essential in all areas. It goes without saying that the battery systems should also be state-of-the-art.

Thanks to the DG (Direct Georeferencing) solution, less overlaps are needed for the images. This reduces the time needed for the overflight and thus the number of photos that have to be processed later.

Peak values in the flight parameters are therefore essential. However, the company profile of Microdrones as a mere manufacturer of flight platforms is no longer correct.
The unique selling point of Microdrones in the UAV market is that the company does not develop different flight platforms, but rather a differentiated product portfolio of solutions that are designed for surveying tasks. The payload, flight platform and equipment are carefully harmonized.

International cooperation

Research and development are essential tasks at Microdrones and the company uses considerable resources for this. As a result of company development (merger of two companies), there is a development team in Canada and one in Siegen in North Rhine-Westphalia. While Canadians are mainly working on payload development and data processing, the main focus in Germany is on optimizing the platforms. "Despite geographical separation, collaboration is very intense," says Dr. Michael Pontz, Development Manager at Microdrones.

"All Microdrones solutions have a leading position in the market with very long flight time, but, of course, the more technology that needs to be integrated, the more compromises there are that need to be made," says Pontz. Getting the optimal compromise depends on many details. "The harmonization of the mechanical, electrical and software components is crucial," says Pontz.
Which components configure an overall solution is always determined by its end purpose, for example, in laser-based systems: There are various solutions from an "access variant" with a laser from the manufacturer Sick to the high-end solution with a sensor from Riegl, which is designed for maximum productivity. Both systems are Direct Georeferencing (DG) solutions.  

All DG-products are able to capture the exact position as well as spatial position at all times during data collection and image triggering.

For this purpose, high-precision Applanix GNSS-E is integrated, and this also has an inertial module. This GNSS inertial system has a very small form factor and is one of the most powerful components of its kind on the world market. It is thus able to determine its position extremely accurately, even in bad signal environments.

This kind of efficient technology is extremely important to Microdrones because it is directly noticeable in the application. It makes the use of ground control points largely superfluous. In addition, it requires less overlap, i.e. the area productivity of the drone increases rapidly. Specifically, an mdMapper1000DG can measure up to 80 hectares - about 30 percent more than the non-DG version.

These properties are also stored in the flight control. "Our goal is to generate a one-bottom system," says Pontz, which means that the user only defines the recording surface, the basic settings required for the result. In the case of the DG version, this means that highly precise survey data are available at the push of a button and that other flight, recording and mission parameters are required for a flight to inspect high voltage pylons. "All this knowledge, expertise and experience are available in the fully configured system," says Pontz. That is, the software for flight planning, monitoring and evaluation is also available for the Android platform. The manufacturer finally assumes that the increasingly mobile consumer terminals in the field will be used on a touchscreen basis.

Longflying times central

The long flight times of Microdrones have been a feature of Microdrones from the start. Even five years ago, the overflight project of the main Alpine ridge caused a sensation, when the quadrocopter stayed in the air for 25 minutes in difficult weather conditions.

First of all, the chassis is partly responsible for this. It is manually manufactured from carbon. "This is the material that optimally combines light weight and high stability worldwide," says Pontz, referring to the material established in model or sports equipment construction. Weight and strength result from a millimetre-accurate bonding of carbon fibre-based plastics, and since every gram counts, quality work is required. The central chassis part is also called a monocoque and consists of one piece.

The four rotors are also manufactured to exact specifications. When the first motors were developed and manufactured at Microdrones in the start-up phase, this was mere development work. Although UAV motors are standard equipment today, Microdrones has always stayed with customization. "The rotors are enormously important for the overall system. Every gain in efficiency increases exponentially to a certain extent, "says the doctor of physics.

This encapsulates a structural feature, because the rotors have a comparatively low speed. "Not only does the weight play a role in the rotors, but also the efficiency of the engine. The higher this is, the less power is consumed, "says Pontz.

The drives consist of high-pole external rotor motors and drive the propellers directly without additional gears. Since the propellers are very wide and large-scale, the engines must deliver a high torque. This concept makes it possible to provide high mechanical quality. That means: Low friction losses ensure that the power output does not dissipate in frictional heat, thus enabling longer flight times.

The low speed ensures a quieter position in the air and less background noise compared to the high-frequency variants that often produce an aggressive bee swarm noise. "The sonorous buzzing of our aircraft also ensures that the drones are not perceived so quickly as an aggressive threat," says Pontz. The wind stability in this type of rotor is also very good and thus the MD family is predestined for use in surveying tasks.

It is not evident at first glance, but the relationship between rotors/drive and the sensor suspension, the so-called gimbals, is even more important. Microdrones has also put much development work into this point. Although there are standard gimbals on the market, these are usually designed for high-frequency rotors and therefore unsuitable for taking precise photos or laser recordings with the drones of the md family. However, their low-frequency rotors are essential for the long flight times, therefore, the gimbal also begs to be customised.

The central task of the gimbal is not only to balance the drone's movements, but also to decouple the vibration spectrum. Microdrones offers both active and passive gimbals that are optimally adapted to the respective sensor.

Some Microdrones systems already include "brushless gimbals", the latest generation of high-performance suspensions, such as those used in the film and media sectors. These variants, which are also referred to as active gimbals, compensate for the movements and vibrations with special brushless mini-motors. The complex systems consisting of sensors, gyroscopes and acceleration sensors aim at perfect stabilization,
precision and almost instantaneous compensation control of cameras or lasers or precise. They avoid distorting effects during the shot (rolling shutter, jello, wobble, etc.), which are not only avoided during film recording, but also in the measurement of accuracy. Even with the passive gimbal, Microdrones treads the line of the currently feasible limits and offers an extremely light gimbal, which is nevertheless decoupled on two axes. For Microdrones, the variety at this point is crucial, because it allows the company to decide in which solution which gimbal best fits the overall package.

The following applies to the system integration: The better it is, the less the end user "experiences" this. However, a one-bottom system is not possible at all without this development work. An additional advantage: "Due to our extensive development work, we can respond exactly to customer requirements," says Pontz. This is the prerequisite for further increasing the variance of the product range and constantly bringing new VTOL, high-performance solutions to the market, all of which have a lowest common denominator: The longest feasible flight time within the economic framework.

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