Until 2006, the only broadcast-use motorized Pan/Tilt heads on the market were very heavy, because professional equipment was built to hold analog video cameras, which could weigh well over 100 lb. But due to the recent transition to digital TV, camera manufacturers have flooded the U.S. market with lightweight, high-definition (HD) digital cameras. These new cameras weigh less than 10 lb, and weight continues to drop as the use of flash memory storage devices increases. When demand recently stabilized, Video Robotics, Gardena, Calif., set out to design small, lightweight, and professional-quality Pan/Tilt heads for these new cameras and soon released a modular Pan/Tilt head named Birdy.
Initial design and development of the Birdy head challenged the engineering team. They needed to design a lightweight unit that was easy to manufacture, while still providing a solid look and feel. The application also requires extraordinarily smooth motor control and minimal gear transmission noise. Other challenges included extending the remote distance to at least 1,000 ft, and separating the pan and tilt into independent modules to minimize costs.
The most pressing task was choosing the gear transmission and motor. According to design engineer Stefan Stanev, “Our prototypes used only a planetary gearhead for its compact size and cylindrical shape that fits easily into the tubes. However, imbalanced tilt loads were able to move the gearhead when in a still position. Not only that, but the diameter was too large and output backlash too high for professional Pan/Tilt usage. We tried using a worm gearhead, but that didn't work either. Neither method worked on its own.”
In the end, the company decided to use both types of gearheads, thereby separating the gear transmission into two stages — a small worm gearhead as the output stage, and a small planetary gearhead as input. Both the motor and planetary gearhead had to fit into a 28-mm internal diameter tubing. Secondly, motor stall torque had to be at least 200 mNm for smooth motion at very slow speeds, and to reach maximum speed (30°/sec or faster) — all while carrying a 10-lb camera.
The company found a suitable motor, the RE26, from Maxon Precision Motors Inc., Fall River, Mass. Unfortunately, the gearheads that had to fit this motor were the same or larger than the motor's diameter. Video Robotics needed a smaller gearhead diameter to have the space for the sound insulation required in the design. Maxon was able to make the match work. To reduce audible noise from the planetary gearhead, Maxon uses a combination of plastic and metal planetary gears, without sacrificing output torque. The use of a smaller diameter planetary gearhead gives Video Robotics more space to use more insulation to reduce any noise. (More noise is prevented with custom-designed and molded rubber fasteners that mount the motor and planetary gearhead.) The finished Birdy Pan/Tilt head features smooth motion, compact size and weight, and one-minute assembly out of the box. A multi-camera control console is also available. For more information, visit www.maxonmotorusa.com.