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DJI-Gimbal-FOC
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Update README.md

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RENAUD Lucien 2022-05-25 17:03:22 +00:00
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@ -8,14 +8,12 @@ The aim of this project is to be able to use the 3-axis DJI gimbal with a custom
## 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.
<img src="docs/setup.jpg" height=250>
Here is the strategy I followed to find the pinout:
1. Find all equipotential pins with a multimeter set to continuity tests, and test all the combinations
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=500>
<img src="Kicad/Breakout_DJI_Gimbal.png" height=400> <img src="docs/setup.jpg" height=400>
### Open-loop control
@ -41,12 +39,11 @@ Ratiometric means that the output signal is proportional to the voltage supply t
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=300>
<img src="docs/courbes.png" height=250> <img src="docs/cosSinEncoderDiagram.png" height=250>
We can see that in the first movement (positive rotation), the green is out of phase of π/2.`
<img src="docs/cosSinEncoderDiagram.png" height=250>
### 3. Encoding the position
1. Get the absolute angle within a period
@ -104,7 +101,6 @@ To achive position control it is necessary to have first, a velocity controller
![Closed loop position diagram from SimpleFOC](docs/angle_loop_v.png)
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="docs/drilling.jpg" height=250> <img src="docs/freeturn.gif" height=250>