The initial design criteria of the gimbal was based around the selection of the gimbal payload, which is specifically tailored for search and rescue purposes. One of the most advanced and commercially available infra-red cameras on the market is the FLIR Vue Pro. This thermal imaging camera is perfect for SAR applications and is lightweight and small. With that being said, the gimbal has to be capable of taking modular payloads of various sizes. With this in mind, the gimbal was designed to accommodate cameras ranging from miniature sizes up to small SLR cameras weighing up to 700 grams. This set the engineering requirement for a specic brushless gimbal motor size. The motor specications are set by the manufacturer according to the maximum payload weight the motors can handle. This is a physical constraint owing to the rotational inertial properties of the camera as it sits on the gimbal.
The most important design consideration in a three-axis gimbal is the adjustable axis mounts which gives the gimbal the ability to maintain its payload on the centre of gravity. This design feature is clearly seen in the CAD drawing in the figure below. Each axis mount has adjustable fastening positions on two axes, allowing for six degrees of freedom adjustability of the payload, depicted as a hand-held camera in the assembly. Owing to the main focus of this project not being the design of the gimbal itself, but rather the control system of the gimbal, the preferred manufacturing technique was rapid prototyping. There are several methods of rapid prototyping but the most accessible and commercially available method is 3D printing by Fused Deposition Modelling. Most commercial or hobbyist built 3D printers operate by FDM.
The 3D printed parts printed well and can be seen in the figure below.The blue parts are PLA, a printing filament that is a lot easier to print with, but more brittle and not as strong. And the white parts are ABS, a filament that can be a real pain because it tends to warp as it cools down. Both materials were used to see how they hold up under stress and to take that knowledge into consideration in the final design.
The electronics that were chosen to be integrated into the gimbal were:
- 3-Axis 32 bit Basecam Alexmos Gimbal Controller
- DYS BGM 3608 – 70 Brushless Gimbal Motors
- Arduino Mega
- Arduino Wi-Fi Shield