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Camera Stabilization for Ocean Filming

Small Brush DC Motors Provide Camera Stability During Ocean Filming

In the rugged environment of the ocean, making brilliant films is far from easy. To shoot the "OCEANS" documentary, French film company, Galatée Films required some improvements to their existing camera technology. The challenge of creating the necessary camera stability to ensure shudder-free images while filmed "on top of" a permanently shaky surface was particularly difficult for the developers. A gyroscopic mounting platform with several micro DC motors proved to be the perfect solution.

ocean filming - camera stabilization made possible with micro drives from MICROMO and FAULAHBER

Shooting high-quality nature films is hard enough on land, but even more challenging at sea. For one thing, the crew is much more dependent on the weather and for another, the kind of travel required on location is extremely time-consuming and not as easily repeated - if at all. This means that each take must produce the perfect shot. In this particular case, an 26.2 ft long and 8.2ft wide rubber dinghy with a 200 hp outboard motor was chosen as the “assault vehicle”. The inflatable boat was suitable for transporting the camera equipment in the shallow waters along the shoreline as well as out on the high seas. Onboard stabilization consisted of the Thetys platform, a 14.7 ft jib crane and a stand to mount it on the boat. When attaching it to the bow, care had to be taken not to exceed the maximum allowable weight, so that the seaworthiness of the inflatable was not unduly impaired. These requirements meant that the 14.7 ft long crane weighing over 660 lbs had to be able to carry the stabilizing platform with 165 lbs of its own weight, plus camera load. The platform itself can stabilize camera equipment weighing up to 88 lbs.

Creating a Fixed Point in Fluid Space

As is the case with aircraft, movement in a boat occurs in all three spatial directions. Lurching, rolling and pitching are often accompanied by some hard knocks mechanical impacts that all technical components must be able to withstand. Shock absorbing mounts can only block some of the occupational hazards of shooting at sea, such as motor vibrations. Since any equalizing movements have to occur in real time, rapid data processing is also called for, as well as a drive system that can quickly execute the related computerized commands with as little backlash as possible. The necessary computations in this case are handled by a 1 GHz Pentium processor. The mounting plate for the camera is stabilized via three gyroscopes in all spatial directions. Optical tracking, to even out the fluctuating movements so that the lens is always focused on the right shot, is achieved via two drive systems per spatial axis.

Reliable Performance For Once-in-a-Lifetime Shots

The performance inhibiting factors for rapid, dynamic yet precise movements are breakaway torque, gear backlash and drive efficiency. The non-linear behavior of these factors makes it harder for the computer to calculate the steering commands. The actual drive consisted of a 24 V small DC motor with a 38 mm diameter and matching planetary gearing supplied by FAULHABER and MICROMO. "The main benefit of the drives", explains Jacques Perrin, director and co-developer of the stabilizing platform, "lies in their almost cog-free action. They also have no iron losses and offer high dynamic performance thanks to low rotator inertia. The high performance ratio is a further plus for our purposes." The motors weigh as little as 400 g but achieve 220 W. The triple reduction gearing (with a reduction ratio of 1:64) increases the rated torque to 15 Nm. The maximum torque available in, for instance, emergency situations is 30 Nm. In order to increase the response accuracy and minimize the backlash of the gears, two drives work on each axis in a push-pull arrangement. Weighing less than 2 kg, this drive is the optimal solution due to both its rapid response and robust construction. The chosen motor control system is also part of the FAULHABER product range. The 4-quadrant, switching pulse-width modulation facilitates high precision motor movements. With up to 10 A, the controller also ensures the necessary power supply even during substantial equalization maneuvers. Modern micro drives and matching accessories like gears and control systems allow the complex actuators to be quickly assembled. Top performance in the tiniest space, minimal weight, yet high speed coupled with precise positioning make this an option that may well prove suitable for use in many other areas.

For more information about how MICROMO can provide a customized motion solution for your next application, contact us today!

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