Tag Archives: mirrorless camera

Brushless Gimbals – Part 1 – Introduction

Camera Gimbals
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.

3D Printed UAV Mapping Mount

3D Printed UAV Downward Facing Mapping 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.

EasyGimbal handheld GoPro Gimabl

EasyGimbal handheld GoPro Gimbal

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.

FY Reach extension pole with FY G4 3-xis handheld gimbal

FY Reach extension pole with FY G4 3-xis handheld gimbal

Gimbals can also provide a stabilized camera platform on rovers such as the Flyoxis Buggy Cam allowing the recording of ceilings and tunnels.

Flyonix Buggy Cam

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.

Zenmuse H3-2D 2-Axiz Gimbal on a DJI Phantom 2

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:

Model Camera Price
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

Components
The brushless gimbal is made up of a number of different components:

  • Gimbal frame
  • Gimbal controller
  • IMU (Inertial Measurement Units)
  • Brushless Motors
  • Battery
  • Camera
Gimbal Frame

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.

DSC00792

DYS 3 Axis Brushless Gimbal

Gimbal Controller

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.

Basecam SimpleBGC 32 Bit Gimbal Controller with IMU attached

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.

IMU attached to gimbal frame

Brushless Motors

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.

DSC00798

Brushless Gimbal motor

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.

Calibration
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.

Detailed instructions on how to do this can be found in many places including YouTube videos.

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.

SimpleBCG Gimbal Calibration Software

A triple axis camera spirit level can be used to accurately calibrate the two IMUs.

DSC00918

Camera Triple Axis Spirit Level

A number of other settings can be altered in order that the gimbal works as required.

3 Axis Brushless Gimbal for Sony NEX size cameras

3 Axis Brushless Gimbal for Sony NEX size cameras

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.

Sources
http://www.simplebgc.com/eng/

http://www.simplebgc.org/

http://www.unmannedtechshop.co.uk/3-axis-brushless-gimbal-sony-nex-size-camera/

http://www.unmannedtech.co.uk/manualsguides/blg3sn-brushless-gimbal-assembly-guide

http://www.dronetrest.com/t/how-to-connect-and-setup-alexmos-3-axis-brushless-gimbal-controller/53

http://www.dronetrest.com/t/balancing-your-brushless-gimbal/55

https://en.wikipedia.org/wiki/Gimbal

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Mirror-less Cameras and UAVs

UAV (Unmanned Aerial Vehicle) photography and photogrammetry has long been a balance between weight and the quality of the camera equipment carried.

Cameras

Low cost camera solutions such as the GoPro can be carried on almost all UAVs because they are small and lightweight, but these benefits are also drawbacks because limited size/fish eye lenses and small image sensors reduce the quality of the photographs they take, together with this the lack of control of many of the camera settings is a drawback.

High quality DSLR (Digital Single Lens Reflex) cameras have superior quality lenses and image sensors together with the fact that they have extensive control of the camera settings meaning that they take much better photographs. But they can only be carried by much higher power/cost octo and hexo-copter systems.

One solution is the lightweight point-and-shoot camera/compact camera used in some mapping solutions, such as those provided by 3DRobotics (Canon PowerShot S100). Although these cameras provide a better quality solution than the GoPro, and may be all that is required for mapping exercises; they are still limited in their optics and higher megapixel sensors which are much more important in the recording of complicated structures and photogrammetry work.

Changes in the camera industry due to competition from the phone industry has enhanced development of a different solution. This is the MILC (Mirrorless Interchangeable-lens camera) or DSLM (Digital Single Lens Mirrorless) Camera. These cameras don’t have the mirror reflex optical viewfinder of a DSLR camera, and the associated weight, replacing it with a LCD screen or with an app on a mobile device which controls the camera. As a result they have the capability to carry high quality interchangeable lenses without the weight associated with DSLR cameras. The system comes in two different forms; the first resembles a standard digital SLR camera, while the second resembles just a lens with all control being provided by an app on a mobile device.

Camera Comparison
Camera Type Megapixel Weight Cost
Canon EOS 5D Mark III Digital SLR 22.3 Approx 950g £2,544
Nikon D5300 Digital SLR 24.2 Approx 840g £549.99
Sony A5000 DSLM Digital SLM 20.1 Approx 388g £250
Sony ILCE-QX1 Lens Style Camera 20.1 Approx 332g £250
Canon PowerShot S100 Compact Camera 12.1 Approx 198g £195
GoPro Hero3+ Black Sports Camera 12 74/136g (with housing) £349.99
Canon EOS 5D Mark III

Canon EOS 5D Mark III

Nikon D5300

Nikon D5300

α5000 E-mount Camera

α5000 E-mount Camera

ILCE-QX1 Lens-Style Camera

ILCE-QX1 Lens-Style Camera

3DRobotics UAV Mapping Solutions, discussed in another blog entry, carry the Canon PowerShot S100 digital compact camera.

Canon PowerShot S100

Canon PowerShot S100

GoPro Hero3+ Black

GoPro Hero3+ Black

UAVs

UAVs come in a number of different configurations and increase in price with a higher level of complexity and ability to carry heavier loads.

UAV Comparison
UAV Type Payload Capacity Price (Without Gimbal)
3D Robotics Iris+ Quadcopter 400g £599
3D Robotics X8+ Octocopter 800g – 1Kg with reduced flight time £880
Spreading Wings S900 Hexacopter 4.7 – 8.2Kg £1,291-£1,540
DJI Spreading Wings S1000+ Octocopter 11Kg £1,750-£2,057
3D Robotics Iris+ Quadcopter

3D Robotics Iris+ Quadcopter

3D Robotics X8+ octocopter

3D Robotics X8+ Octocopter

Gimbals

Gimabls are an important element in stabilizing cameras during photography and video recording, as well as providing a motorized solution to move the camera to a desired angle during flight. They can add significantly to both the weight and price of any UAV solution depending on the camera equipment they are carrying.

Gimbal Price Comparison
Gimbal Camera Weight (Camera excluded) Cost
DJI Zenmuse H4-3D GoPro 168g £249
DYS 3 axis brushless gimbal Sony NEX size camera 388g £231.95 – £299.94
DJI Zenmuse Z15-A7 Sony α7s and α7r 1.3Kg £1,915
DJI Zenmuse Z15-5D III (HD) Canon EOS 5D DSLR 1.53Kg £2,831

Solutions

The 3DRobotics Iris+ Quadcopter has a payload capacity of 400g which would allow a rather small 15g for a mount to attach a Sony A5000 DSLM or 68g to attach a Sony QX1 Lens-Style Camera without weighing too much, although the system could be flown with excess weight reducing the flight time. A downward facing 3D Printed Sony A5000 Mapping Mount  is available for both the Iris+ Quadcopter and X8+ Octocopter, it weighs 36g.

Although the X8+ is a octocopter by definition, it gets over the intrinsic problems of size, weight and cost caused by eight separate arms by having two rotors on each arm, one pointing up and the other downwards. With a maximum payload of 1KG it can carry a Sony A5000 DSLM camera (388g) together with a gimbal such as the DYS 3 Axis Brushless Gimbal for Sony NEX size cameras (609g) to support and move it, the gimbal is designed for the NEX range of cameras, but they are almost identical to the A5000 in design. Although a lighter mount could be used.

3 Axis Brushless Gimbal for Sony NEX size cameras

3 Axis Brushless Gimbal for Sony Nex size cameras

Conclusions

The mirror-less camera would seem to provide a solution to the problem of how to carry a high specification camera capable of capturing high quality images on a fairly low-cost UAV solution.

Sources

http://en.wikipedia.org/wiki/Mirrorless_interchangeable-lens_camera

http://www.dummies.com/how-to/content/gopro-cameras-understand-the-cameras-limitations.html

http://www.japantimes.co.jp/news/2013/12/30/business/mirrorless-cameras-offer-glimmer-of-hope-to-makers/

Quadcopter vs Hexacopter vs Octocopter: The Pros and Cons