Linear CNC Stage Control with Arduino and TMC2209

This project demonstrates how to control a linear CNC stage using an Arduino, a TMC2209 stepper motor driver, and a Mitutoyo LGS-1012P linear encoder. The system employs a PID control loop to accurately position the stage. Additionally, this project demonstrates how to make use of the Mitutoyo digimatic serial interface for reading precise linear position measurements.

Components

• Arduino (e.g., Arduino Portenta 7, Nano RP2040 Connect)
• TMC2209 Stepper Motor Driver
• Stepper Motor
• Mitutoyo LGS-1012P Linear Encoder
• Power Supply (appropriate for your stepper motor)
• Connecting Wires
• Breadboard (optional for prototyping)

Wiring

Arduino to TMC2209

• ENABLE_PIN (D2) -> TMC2209 EN
• DIR_PIN (D3) -> TMC2209 DIR
• STEP_PIN (D4) -> TMC2209 STEP
• SW_TX (D6) -> TMC2209 PDN_UART
• SW_RX (D7) -> TMC2209 PDN_UART
• GND -> TMC2209 GND
• 5V -> TMC2209 VCC

TMC2209 to Stepper Motor

• A1 -> Stepper Motor Coil A1
• A2 -> Stepper Motor Coil A2
• B1 -> Stepper Motor Coil B1
• B2 -> Stepper Motor Coil B2

Arduino to Mitutoyo Linear Encoder

• REQ_PIN (D11) -> Encoder REQ
• DATA_PIN (D8) -> Encoder DATA
• CK_PIN (D9) -> Encoder CLK
• GND -> Encoder GND
• 5V -> Encoder VCC

Power Supply

• Power Supply Positive (e.g., 12V) -> TMC2209 VM
• Power Supply Ground -> TMC2209 GND

Setup Image

Arduino Code

The Arduino code for this project, which communicates over the micro-ROS agent, can be found in the file: /motor_linear_encoder_control/motor_linear_encoder_control.ino. This code implements a PID control loop that reads the encoder value and adjusts the motor position to achieve the desired setpoint.

Additionally, there is a sketch which does not make use of the micro-ROS agent, and it provides a proof-of-concept that the system can in fact use PID control to drive the linear stage towards an encoder position of 7.5mm under the file: /motor_linear_encoder_control_test/motor_linear_encoder_control_test.ino

Setting Up and Running the micro-ROS Agent with a Simulator

For this example, we will configure a ROS2 environment with the micro-ROS agent and use the motor_controller and arduino_simulator_serial packages to simulate a closed loop sequence.

Once these two are working together, we only need to modify the serial port which micro-ROS communicates over to target an actual Arduino running the .ino sketch above.

Installing micro-ROS Agent

First, you need to install the micro-ROS agent on your ROS2 machine.

Running micro-ROS Agent

Use socat to create linked virtual serial ports on your computer:

sudo apt-get install socat
socat -d -d pty,raw,echo=0 pty,raw,echo=0

Using motor_controller Package

The motor_controller package publishes pos_cmd values to the Arduino/simulator.

Using the arduino_simulator_serial Package

This package simulates the Arduino behavior and communicates over a virtual serial port.

Building

Assuming this repository is near the home root of your environment (modify as necessary), we can build the packages using colcon.

cd ~/Arduino_Linear_Encoder_example
colcon build

Running the Simulator Node

1. Ensure Virtual Serial Ports are Created using socat:

socat -d -d pty,raw,echo=0 pty,raw,echo=0

Note the virtual serial ports created, e.g. /dev/pts/3 and /dev/pts/4.

2. Run micro-ROS Agent on /dev/pts/3:

ros2 run micro_ros_agent micro_ros_agent serial --dev /dev/pts/3

3. Run the Controller Node:

ros2 run motor_controller motor_controller_node

4. Run the Simulator Node on dev/pts/4:

ros2 run arduino_simulator_serial arduino_simulator_node /dev/pts/4

This setup allows you to simulate the Arduino micro-ROS behavior and communicate over a virtual serial bus using socat, making it look like a micro-ROS device. You can then test your ROS2 motor_controller package without needing the actual hardware.

When we do connect an Arduino running the micro-ROS sketch, then we note the communication port, and we initialize the micro-ROS agent to interface with the hardware. As long as the Controller Node is running, then we should be able to use the micro-ROS agent to give setpoint commands to the Arduino device in order to drive the motor and actuate the position of the linear stage.

Usage

1. Wiring: Follow the wiring instructions provided above to connect your Arduino, TMC2209 driver, stepper motor, and Mitutoyo linear encoder.

2. Upload Code: Open the Arduino IDE, navigate to the provided Arduino code file (/motor_linear_encoder_control/motor_linear_encoder_control.ino), and upload it to your Arduino board.

3. Monitor Output: Open the Serial Monitor (set to 9600 baud rate) to observe the encoder readings and PID control output. Adjust the PID constants (Kp, Ki, Kd) as needed to achieve desired performance.

License

This project is licensed under the MIT License. See the LICENSE file for details.