Camera Gimbals are used for many different things in many different industries including stabilizing cameras for TV/Cinema. Their development can be traced from the introduction of the Steadicam in the 1970’s. This allowed the stabilized movement of a camera, revolutionizing filming by removing the need for a wheeled Camera Dolly running on expensive/time consuming tracks or leveled boards. Although the system is not motorized it introduced the principal of a stabilized camera.
Recent technological developments have allowed the construction of lightweight/low cost motorized gimbal systems which can be carried by UAVs.
Gimbals and Archaeological/Heritage recording
With the development of the UAV the development of a lightweight camera gimbal to enable it to carry stabilized cameras was also begun.
The gimbal has become an important element in UAV photographic/video recording, from taking vertical photographs for mapping purposes to cinematic style flypasts/throughs of buildings.
Mapping can be undertaken with cameras attached to the UAV with a static mount, but this removes the ability to use the camera for other recording methods without landing the UAV and changing the mount.
Although this series of blogs will concentrate on UAV camera gimbals, much of what is discussed is transferable to other recording platforms/techniques.
There are also other recording systems that use gimbals which could aid in recording; including handheld GoPro systems such as the EasyGimbal Kickstarter Project.
Some of these types of systems, such as the FY G4 handheld gimbal, can be attached to extensions poles allowing low altitude aerial photography/video to be undertaken using a handheld remote control to rotate the gimbal.
Gimbals can also provide a stabilized camera platform on rovers such as the Flyoxis Buggy Cam allowing the recording of ceilings and tunnels.
UAV camera gimbals
UAV camera gimbals are designed to:
1. Remove camera vibration using the anti-vibration rubber balls within the gimbal frame.
2. Stabilize the camera as the UAV moves, keeping it level and pointing in the required direction.
3. Allow the movement of the camera to point at the subject matter while flying the UAV, sometimes in completely different directions.
Types of gimbal
Gimbals come in two different types:
1. The two-axis gimbal.
2. The three-axis gimbal.
Two-axis gimbals are designed for UAVs where there is no requirement to pan the camera from left to right, such as those with fixed landing gear which precludes the panning of cameras whether physically or visually.
There are many different gimbals for numbers of different camera, from GoPros through mirrorless cameras to Digital SLR cameras.
Some of these can be purchased already constructed and calibrated out of the box, such as the Zenmuse Gimbals supplied by DJI Innovations. Others come ready installed on a UAV. While the one I will be discussing is a DIY kit which needs to be built and setup.
The price difference between buying a ready made solution and building your own one from a kit in order to carry the same camera can can be quite significant:
|DYS BLG3SN 3-Axis Brushless Gimbal with BaseCam SimpleBGC 32-bit controller||Sony NEX size camera||£299.94|
|Zenmuse Z15||Sony NEX 5 and 7||£1,915.00|
The brushless gimbal is made up of a number of different components:
- Gimbal frame
- Gimbal controller
- IMU (Inertial Measurement Units)
- Brushless Motors
Gimbal frames are deigned for different types of cameras. The gimbal frame I am using for this project is the DYS BLG3SN 3-Axis Brushless Gimbal Frame kit with 3pcs BGM4108-130 Brushless Motors for the SONY NEX type of camera. I will be using a Sony α5000 Mirrorless Camera which is almost identical to the NEX series cameras.
In order to control the gimbal a gimbal controller board is required, there are a number available on the market. The Zenmuse gimbals supplied by DJI Innovations are designed to connect directly into the DJI UAV, while other solutions require a separate board.
The gimbal controller board one I am using is the BaseCam SimpleBGC 32-bit board which is designed for 3-axis gimbals. The cheaper and simpler BaseCam (AlexMos) SimpleBGC (formerly called AlexMos) although designed for 2-axis gimbals can be upgraded to support 3-axis gimbals with the addition of an extension board. The 32-bit board is a lot easier to use as well as being more up-to-date and so was chosen as a first gimbal construction experiment.
IMU (Inertial Measurement Unit)
Another important element is the IMU , in the case of this 3-axis gimbal two of these are required. One is connected to the main frame of the camera gimbal while the other is connected to the camera mount. These tell the gimbal controller which direction the gimbal/camera is pointing and the gimbal controller can then control the motors to point the camera in the required direction.
The importance of brushless motors in the development of lightweight/high-powered UAV systems has already been discussed in another blog.
Those in gimbals are slightly different, rather than being designed to spin quickly they are designed to hold the camera in position with enough torque to stop it moving and also to rotate to level the camera when required.
In the case of a 3-axis gimbal one motor is required for each of the 3 axis.
Although originally it was required to rewind the wires inside motors designed for the rotor blade with thinner wires to increase the motor resistance and torque, it is now possible to buy ready made motors for the purpose. These motors come in different sizes depending on the size of the camera they are required to stabilize.
In order to use the gimbal it needs to be calibrated. This is done using the OpenSource SimpleBCG program. The is installed either as a Windows program or Android app and the gimbal is calibrated using the USB port on the gimbal controller board.
In the case of a 3-axis gimbal two IMUs need to be calibrated, one for the camera and the other for the gimbal frame.
A triple axis camera spirit level can be used to accurately calibrate the two IMUs.
A number of other settings can be altered in order that the gimbal works as required.
Once the gimbal controller has been calibrated the camera will remain in place as the gimbal is moved around it. This is done by calibrating the IMUs to a nominal position, the IMUs determine the actual position of the gimbal and the motors are turned on to correct the position, less voltage is sent to the motors the closer to the nominal position that the gimbal is.