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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 ## 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. 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: 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 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) 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 ### 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) 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 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.` 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 ### 3. Encoding the position
1. Get the absolute angle within a period 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) ![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. 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/drilling.jpg" height=250> <img src="docs/freeturn.gif" height=250>
<img src="docs/freeturn.gif" height=250>