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Lucien Renaud 2022-05-26 19:18:11 +02:00
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README.md
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The aim of this project is to be able to use the 3-axis DJI gimbal with a custom open source controller like [SimpleFOC](https://docs.simplefoc.com/). This high quality gimbal is very tiny and easy to find as a replacement part which makes it very suitable for DIY projects.
<img src="docs/overview.jpg" height=250>
<img src="docs/working.gif" height=250>
<img src="https://git.lurenaud.com/lurenaud/DJI-Gimbal-FOC/src/branch/main/docs/overview.jpg" height=250>
<img src="https://git.lurenaud.com/lurenaud/DJI-Gimbal-FOC/src/branch/main/docs/working.gif" height=250>
## Pinout identification
The Gimbal is composed of a flex PCB with a main connector and 3 smaller for each motor. The main end connector is a 40-pin mezzanine board to board connectors. In order to work easily I have designed a breakout board which open to a 2.54" header. (Kicad folder)
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2. Group remaining pins by motor With the multimeter find all the pins connected to the motor connector. (Reapeat 3 times for the other connectors)
<img src="Kicad/Breakout_DJI_Gimbal.png" height=400> <img src="docs/setup.jpg" height=400>
<img src="https://git.lurenaud.com/lurenaud/DJI-Gimbal-FOC/src/branch/main/Kicad/Breakout_DJI_Gimbal.png" height=400> <img src="https://git.lurenaud.com/lurenaud/DJI-Gimbal-FOC/src/branch/main/docs/setup.jpg" height=400>
### Open-loop control
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### 1. Setup
Each motor is composed of two ratiometric linear hall sensors. (Texas Instrument DRV5053 Analog-Bipolar Hall Effect Sensor) They are placed at around 120º from each other (eyes measured) and measure the magnetic field of the rotor.
<img src="docs/Hallmotor.jpg" height=300>
<img src="https://git.lurenaud.com/lurenaud/DJI-Gimbal-FOC/src/branch/main/docs/Hallmotor.jpg" height=300>
Ratiometric means that the output signal is proportional to the voltage supply to the sensor. In this setup, with 5V supply, the output measured is between 520mV and 1.5V, so a 1V amplitude signal.
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These oscilloscope traces are the sensor output when rotating the rotor forth and back. (a bit less than 180º on the 3rd motor)
The channel 0 (Yellow) is the Hall 1 and the Channel 1 (Green) is the Hall 2
<img src="docs/courbes.png" height=250> <img src="docs/cosSinEncoderDiagram.png" height=250>
<img src="https://git.lurenaud.com/lurenaud/DJI-Gimbal-FOC/src/branch/main/docs/courbes.png" height=250> <img src="https://git.lurenaud.com/lurenaud/DJI-Gimbal-FOC/src/branch/main/docs/cosSinEncoderDiagram.png" height=250>
We can see that in the first movement (positive rotation), the green is out of phase of π/2.`
@ -102,4 +102,4 @@ To achive position control it is necessary to have first, a velocity controller
However, the motors of the gimbal have hard stop and can only rotate of around a half turn. It was so necessary to remove these mecanical stops. I drilled with a 1.6mm drill the two little holes to remove it. Then the motor was able to rotate freely and PID can be tuned.
<img src="docs/drilling.jpg" height=250> <img src="docs/freeturn.gif" height=250>
<img src="https://git.lurenaud.com/lurenaud/DJI-Gimbal-FOC/src/branch/main/docs/drilling.jpg" height=250> <img src="https://git.lurenaud.com/lurenaud/DJI-Gimbal-FOC/src/branch/main/docs/freeturn.gif" height=250>