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Anti-gravity finger

Description: Project aiming to counter the effect of gravity on a one-degree of liberty arm (i.e finger) by programming a torque control command on Dynamixel motor.

demo

👨‍💻 Developer documentation • 📈 Project report • 📚 Bibliography

📄 This project in short

In this project, you will find a Python module that allows you to control your Dynamixel motor with torque commands.

  • One degree of freedom available ;
  • Countering of friction based on Stribeck model ;
  • Use of pypot library ;
  • Constants available for Dynamixel MX-64 and Dynamixel MX-106 (code is available to determine constants for other models).

🚀 Quickstart

Install instructions:

  • Clone this repo
git clone https://github.com/Julienchh/antigravity-arm
  • Create a conda environment with all the dependencies:
conda create -n antigravity-arm
pip3 install numpy scipy matplotlib pypot

Launch instructions: Few lines of code to launch the main feature of your project

  • Connect your Dynamixel motor to your computer (don't forget to plug the power supply). Check the name of the device (often ttyACMx or ttyUSBx) with the following command:
$ ls /dev/tty*
... /dev/ttyS3   /dev/ttyS8
/dev/tty12  /dev/tty19  /dev/tty25  /dev/tty31  /dev/tty38  /dev/tty44  /dev/tty50  /dev/tty57  /dev/tty63  /dev/ttyS11  /dev/ttyS18  /dev/ttyS24  /dev/ttyS30  /dev/ttyS9
/dev/tty13  /dev/tty2   /dev/tty26  /dev/tty32  /dev/tty39  /dev/tty45  /dev/tty51  /dev/tty58  /dev/tty7   /dev/ttyS12  /dev/ttyS19  /dev/ttyS25  /dev/ttyS31  /dev/ttyUSB0 # here, it is the last one
  • Activate your conda environment :
conda activate antigravity-arm
  • Find your motor's ID with:
$ python3 -c "import pypot.dynamixel; dxl_io = pypot.dynamixel.Dxl320IO('/dev/ttyUSB0'); print(dxl_io.scan())"
>>> [20]
  • In the file src/compensation.py, change the following information according to your setup:
DXL_ID = 20             # found just above
PORT = "/dev/ttyUSB0"   # found with the ls command 
MASS = 0.08             # Object mass attached to motor (in kg)
DISTANCE = 0.25         # Center of mass of the object attacher to motor
OFFSET = 90.            # Offset in degrees : the angle value when the object attached to the motor is pointing downwards (minimal torque value)
  • Launch the program and enjoy the anti-gravity finger !
python3 src/compensation.py

🔍 About this project
💼 Client Pollen Robotics
🔒 Confidentiality Public
⚖️ License GNU GPLv3
👨‍👨‍👦 Authors Matteo Caravati, Julien Chabrier, Nicolas Gry

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