Merge pull request #40 from zabertech/tracking-example

Adding motion tracking example.

examples/motion_tracking/.gitignore

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examples/motion_tracking/README.md

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+# Tracking Motion Using PID Controller
+
+This example demonstrates how Zaber stages can track analog input signals using a PID controller.
+A PID controller is a control loop feedback mechanism widely used in industrial control systems.
+It calculates the error between a desired setpoint and a measured process variable and applies a correction based on proportional, integral, and derivative terms.
+In Zaber's case, the controller can move the stage to track the setpoint of the analog input signal.
+Zaber only supports the PI controller, which is a simplified version of the PID controller without derivative term.
+
+The following video demonstrates the concept:
+
+![video.mp4](img/video.mp4)
+
+In the video above there is a load cell mounted on a Zaber stage.
+The stage is tracking the analog input signal from the load cell keeping a constant tension on the spring.
+When disrupted, the stage moves to compensate for the change in the force until it reaches the setpoint again.
+
+## Code
+
+### Dependencies
+
+The script uses `pdm` to manage the virtual environment and dependencies:
+
+Instructions on how to install it can be found on the official `pdm` project page [here](https://github.com/pdm-project/pdm).
+
+The dependencies are listed in `pyproject.toml`.
+
+### Running the Script
+
+Make sure to change `SERIAL_PORT` constant in `main.py` file to the serial port that your device is connected to.
+
+Afterwards, you can run the example:
+
+```shell
+cd examples/motion_tracking/
+pdm install
+pdm run example
+```
+
+### Explanation
+
+<https://github.com/zabertech/zaber-examples/blob/main/examples/motion_tracking/src/motion_tracking/main.py#L17-L32>
+
+After establishing a connection with the device, the script prints the PI controller parameters.
+
+Then based on the user input "track" the scripts starts the PI controller by issuing the `move track` command to the axis.
+After that, the stage will track the analog input signal indefinitely until the user inputs "stop".
+
+## Tuning the Controller
+
+Properly tuning the controller requires a basic understanding of control theory and is beyond the scope of this example.
+Typically, you adjust the Kp and Ki parameters to achieve the desired response.
+You may also need to change the direction (setting `motion.tracking.dir`) if the input signal is inverted.
+In this example, the Kp = 0, Ki = 1000, and the direction is set to 1.
+We recommend using Oscilloscope application in Zaber Launcher to visualize the input signal and the stage position.
+
+## Additional Information
+
+There is also a `move track once` variant of the `move track` command that reaches the setpoint once and then stops.
+For this variant a settings `motion.tracking.settle.tolerance` and `motion.tracking.settle.period` determines
+when the stage is considered to have settled at the setpoint.
+
+You can find the exhaustive list of commands and settings in the [ASCII Protocol Manual](https://www.zaber.com/protocol-manual?protocol=ASCII).

examples/motion_tracking/article.yml

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+authors:
+  - Martin Zak
+date: 2024-12-05
+category: Motion
+tags:
+  - PID
+  - Tracking
+  - Python
+picture: img/chart.png