Add Projects section with inverted pendulum and real-time interface pages

content/projects/_index.md

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+---
+title: "Projects"
+---
+
+Here are personal and professional projects that are all open-source / open hardware.

content/projects/inverted-pendulum/index.md

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+---
+title: "Inverted Pendulum on a Recycled 3D Printer"
+summary: "A pendulum balanced upright on a motorised cart, built from the axis of an old 3D printer and controlled by a Teensy 4.1 at 1 kHz."
+tags: ["Hardware", "Software", "Control"]
+status: "Completed"
+date: 2026-03-22
+repo: "https://github.com/tdehaeze/inverted-pendulum"
+cover: "cover.jpg"
+---
+
+## Overview
+
+This project is a classic control demonstrator: a rigid pendulum is mounted on a cart and kept upright by moving the cart back and forth.
+The mechanics come from a recycled 3D printer (Alfawise U20): one of its linear axes, with the stepper motor and belt, carries the pendulum pivot.
+A quadrature encoder measures the pendulum angle, and a Teensy 4.1 microcontroller runs the feedback loop at 1 kHz.
+A small PyQt5 application on the computer is used to select the controller, change the gains and setpoints, and record data.
+
+{{< figure src="cover.jpg" alt="Photo of the inverted pendulum setup with its main parts labelled" caption="The setup: cart on a belt-driven rail, stepper motor, pendulum encoder and the electronics (labels in French)." >}}
+
+## Hardware
+
+| Component | Details |
+|-----------|---------|
+| Microcontroller | Teensy 4.1 |
+| Stepper motor | DRV8825 driver, 32 microsteps, 5 µm per step |
+| Pendulum encoder | Quadrature, 4096 steps per revolution (0.088° per step) |
+| Cart travel | ±200 mm hard stop, ±160 mm soft limit |
+| Control rate | 1 kHz, driven by a hardware timer (`IntervalTimer`) |
+
+The cart input is an acceleration command.
+It is integrated to a velocity inside the 1 kHz interrupt, and converted into step pulses for the motor driver.
+The pendulum angular velocity is estimated by finite difference of the encoder reading.
+A soft limit blocks accelerations towards the end of the rail, and a hard stop at ±200 mm cuts the motor.
+
+## Software
+
+The repository has three parts:
+
+- **`teensy/`**: firmware (PlatformIO / Arduino framework). Runs the control loop, drives the motor, reads the encoder and streams telemetry over USB serial.
+- **`gui/`**: PyQt5 and pyqtgraph application. Sends text commands to the Teensy (`MODE PD`, `SET KP 12`, `FB ON`, ...), plots the telemetry live and saves it to CSV.
+- **`model/` and `tools/`**: Python scripts for simulation, controller design, model identification and plotting experiments.
+
+## Model and identification
+
+With φ = θ − π the angle from the upright position and u the cart acceleration, the linearised dynamics around the upright position are:
+
+```
+D·φ̈ + c·φ̇ − m·g·l·φ = m·l·u
+```
+
+where D is the effective inertia of the pendulum about its pivot.
+The state is [x, ẋ, φ, φ̇] and the input is the cart acceleration.
+
+The pendulum length and friction coefficient are identified from a free oscillation: the pendulum hangs down, receives a small push, and the decaying oscillation is recorded for 10 to 50 seconds.
+A Nelder-Mead fit (`tools/fit.py`) then adjusts the model to the measurement.
+
+| Parameter | Symbol | Value |
+|-----------|--------|-------|
+| Pendulum mass | m | 0.1 kg |
+| Half length (pivot to centre of mass) | l | 0.326 m |
+| Friction coefficient | c | 3.4 × 10⁻⁴ N·m·s/rad |
+
+{{< figure src="identification-fit.png" alt="Measured and fitted free oscillation of the pendulum" caption="Free oscillation of the pendulum: measurement and fitted model (figure labels in French)." >}}
+
+{{< video src="identification.mp4" caption="Free oscillation used for the identification." >}}
+
+## Controllers
+
+All gains are in SI units, and the controller output is the cart acceleration.
+
+- **P**: u = −Kp · φ
+- **PD**: u = −Kp · φ − Kd · φ̇
+- **LQR**: u = −K · [x, ẋ, φ, φ̇]
+
+The LQR gain vector K is computed in Python (`model/inverted_pendulum.py`, using the `control` library) from weights on the four states and on the input, then entered in the GUI.
+
+### PD control
+
+A PD controller can hold the pendulum angle at zero, but it does not see the cart position.
+In the experiment below the angle is regulated while the cart drifts until it reaches the end of the rail and the pendulum falls.
+The same controller with other gains acts mostly as a damper: it slows down the pendulum without fully stabilising it.
+
+{{< figure src="pd-simulation.png" alt="Simulated PD response of the pendulum angle" caption="Simulated PD response, from a 5° initial angle (figure labels in French)." >}}
+
+{{< figure src="pd-experiment.png" alt="Measured angle and cart position with a PD controller" caption="Measured PD experiment: the angle is held near zero while the cart drifts to the end stop (figure labels in French)." >}}
+
+{{< video src="pd-control.mp4" caption="PD control: the pendulum is stabilised, the cart slowly drifts." >}}
+
+{{< video src="pd-damping.mp4" caption="PD control used as a damper only: the pendulum dynamics are slowed down." >}}
+
+### LQR control
+
+The LQR feeds back the cart position and velocity as well as the pendulum angle and angular velocity.
+This keeps the cart near its setpoint while the pendulum stays upright.
+Higher weights on the states give faster corrections, at the cost of more aggressive cart motion.
+
+{{< video src="lqr.mp4" caption="LQR with a higher gain: angle and cart position are controlled together." >}}
+
+{{< video src="lqr-setpoint-step.mp4" caption="LQR following a step in the cart position setpoint while keeping the pendulum upright." >}}
+
+## Typical workflow
+
+1. Flash the firmware with `pio run -e teensy41 -t upload` from `teensy/`.
+2. Start the GUI (`python gui/program.py`), enable the motor and zero the cart and encoder.
+3. Record a free oscillation (`tools/capture.py`) and fit the model parameters (`tools/fit.py`).
+4. Pick a controller in the GUI, enter the gains, bring the pendulum close to upright and switch the feedback on.
+5. Save the data to CSV and plot it with `tools/plot_experiment.py`.
+
+The full instructions and serial command list are in the [README](https://github.com/tdehaeze/inverted-pendulum).

content/projects/real-time-interface-gui/index.md

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+---
+title: "rtint-gui: Desktop GUI for Real-Time Control"
+summary: "A desktop application to acquire signals, identify plant dynamics and design feedback control on a real-time target."
+tags: ["Software", "Control"]
+status: "Active"
+date: 2026-09-01
+repo: "https://gitlab.esrf.fr/dehaeze/real-time-interface-gui"
+docs: "https://dehaeze.gitlab-pages.esrf.fr/real-time-interface-gui/"
+pypi: "https://pypi.org/project/rtint-gui/"
+---
+<!-- TODO: confirm public URL -->
+<!-- TODO: add GUI screenshots (e.g. Signal Analysis, Dynamical Identification, Feedback Control Design) -->
+
+## Overview
+
+`rtint-gui` is a desktop application for working with a real-time target that runs a Resyst server.
+It is built on top of [rtint]({{< relref "real-time-interface" >}}), which handles the communication with the target, and follows the usual steps of a control task:
+
+1. **Connect** to a running server.
+2. **Acquire** signals from the target.
+3. **Analyse** the records as time traces and spectra (PSD / ASD).
+4. **Identify** the plant dynamics by measuring frequency responses.
+5. **Design** feedback control from the identified dynamics.
+
+Each step is a page of the application.
+
+## Pages
+
+- **Signal Analysis**: choose counters and model signals, set a duration, watch the acquisition live, then compute power spectra with configurable window, overlap and averaging.
+- **Dynamical Identification**: excite the plant with a generator and estimate its frequency response (Bode plot, coherence, and an RGA plot for multi-input multi-output systems). Open-loop and closed-loop identification are supported.
+- **Transfer Function Analysis**: overlay measured responses with the Bode plots of the filters running on the target, and with their products.
+- **Feedback Control Design**: from an identified plant and the filters used as controller, compute characteristic loci, sensitivity and complementary sensitivity, the modulus margin and a Nyquist stability verdict.
+- **Filters, motors, EtherCAT, parameters and more**: inspect and edit what the real-time model exposes.
+
+Results are saved as MATLAB `.mat` files, so they can be reopened in MATLAB or Python.
+The analysis pages also work offline on previously saved data, without a target.
+
+## Installation
+
+```bash
+pipx install rtint-gui     # or: uv tool install rtint-gui
+rtint-gui
+```
+
+Python 3.12 or 3.13 is required.
+The interface uses PySide6 and pyqtgraph.
+Running `rtint-gui --offline` starts it without a real-time target.
+
+The [documentation](https://dehaeze.gitlab-pages.esrf.fr/real-time-interface-gui/) has a guide for each page and a description of the `.mat` file format.
+
+## Related
+
+- [rtint]({{< relref "real-time-interface" >}}): the Python package this application is built on.

content/projects/real-time-interface/index.md

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+---
+title: "rtint: Python Interface to Real-Time Targets"
+summary: "A Python package to control and monitor Simulink models running on a real-time target machine, such as a Speedgoat."
+tags: ["Software", "Control"]
+status: "Active"
+date: 2026-10-01
+repo: "https://gitlab.esrf.fr/dehaeze/real-time-interface"
+pypi: "https://pypi.org/project/rtint/"
+---
+<!-- TODO: confirm public URL -->
+
+## Overview
+
+`rtint` is a Python package that talks to Simulink models running on a real-time target machine, through a Resyst server.
+It wraps the server's client API so that the parts of a real-time model (motors, filters, feedback loops, signals and so on) can be used as ordinary Python objects from a script or an interactive session.
+
+It is used at the ESRF to commission and tune mechatronic systems whose control runs on a real-time target.
+For a graphical front end built on top of it, see [rtint-gui]({{< relref "real-time-interface-gui" >}}).
+
+## What it covers
+
+Each part of the real-time model has its own controller object, available as an attribute of the main `RtintController`:
+
+- **Motors**: start, stop, move and read the state.
+- **Regulation**: switch feedback loops on and off.
+- **Filters**: read and change filter parameters, for example low-pass, PID and notch filters, and compute their frequency responses.
+- **Signals and parameters**: read and write model signals and tunable parameters.
+- **Acquisition**: record signals at the model sampling rate.
+- **Signal generators**: sine, chirp and other excitation signals, useful for system identification.
+- **Triggers, lookup tables, EtherCAT slaves and 2D scans.**
+
+Most objects can print a summary table of their state in the terminal.
+
+## Example
+
+```python
+from rtint.rtint_hardware import RtintController
+
+config = {
+    "server": "my-server-hostname",
+    "port": 8080,
+}
+
+controller = RtintController("my_target", config)
+controller._run_model("my_model")
+
+# Access hardware components
+controller.motor.start()
+controller.regul.on()
+controller.filter.low_pass(wn=100, xi=0.707)
+```
+
+## Installation
+
+```bash
+pip install rtint
+```
+
+Python 3.9 to 3.13 is supported.
+The package depends on `resyst-client`, `numpy`, `scipy`, `matplotlib`, `gevent`, `treelib` and `tabulate`.
+A running Resyst server and a real-time model are needed to do anything useful with it.
+
+## Related
+
+- [rtint-gui]({{< relref "real-time-interface-gui" >}}): desktop application built on this package.

layouts/partials/projects/styles.html

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+<style>
+.project-filter { display: flex; flex-wrap: wrap; gap: .5em; justify-content: center; margin: 1.5em 0 1em; }
+.project-filter button {
+  font: inherit; font-size: .9em; cursor: pointer; padding: .25em .9em;
+  border: 1px solid #d5d8e0; border-radius: 999px; background: #fff; color: #34495e;
+}
+.project-filter button:hover { border-color: hsl(232, 61%, 64%); }
+.project-filter button.active { background: hsl(232, 61%, 64%); border-color: hsl(232, 61%, 64%); color: #fff; }
+
+.project-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 1.5em; margin: 1.5em 0 2em; }
+.project-card {
+  display: flex; flex-direction: column; background: #fff; border: 1px solid #e3e5ea; border-radius: 8px;
+  overflow: hidden; transition: box-shadow .2s, transform .2s;
+}
+.project-card:hover { box-shadow: 0 6px 18px rgba(40, 50, 90, .12); transform: translateY(-2px); }
+.project-card[hidden] { display: none; }
+.project-card-cover { display: block; aspect-ratio: 16 / 10; background: #eef0f5; overflow: hidden; border: 0; }
+.project-card-cover:hover { border: 0; }
+.project-card-cover img { width: 100%; height: 100%; object-fit: cover; display: block; margin: 0; }
+.project-card-cover.placeholder { display: flex; align-items: center; justify-content: center; padding: 0 .5em; text-align: center; color: #fff; font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: 1.8em; font-weight: 600; background: linear-gradient(135deg, hsl(232, 61%, 64%), hsl(232, 45%, 38%)); }
+.project-card-cover.placeholder:hover { color: #fff; }
+.project-card-body { display: flex; flex-direction: column; gap: .5em; padding: 1em 1.1em 1.1em; flex: 1; }
+.project-card-title { margin: 0; font-size: 1.2em; line-height: 1.25; }
+.project-card-title a { color: inherit; border: 0; }
+.project-card-title a:hover { color: hsl(232, 61%, 64%); border: 0; }
+.project-card-summary { margin: 0; color: #4a5568; font-size: .95em; line-height: 1.5; flex: 1; }
+.project-card-footer { display: flex; align-items: center; justify-content: space-between; gap: .5em; font-size: .85em; margin-top: .3em; }
+.project-card-footer a { color: #c05b4d; white-space: nowrap; }
+
+.project-tags { display: flex; flex-wrap: wrap; gap: .35em; }
+.project-tag {
+  display: inline-block; padding: .05em .65em; font-size: .78em; font-weight: 600; letter-spacing: .02em;
+  border-radius: 999px; background: hsl(232, 61%, 94%); color: hsl(232, 45%, 40%);
+}
+.project-status { font-size: .85em; color: #8a8a8a; }
+.project-status::before { content: ""; display: inline-block; width: .55em; height: .55em; border-radius: 50%; margin-right: .4em; background: #b0b4c0; }
+.project-status[data-status="active"]::before { background: #4caf7d; }
+.project-status[data-status="completed"]::before { background: hsl(232, 61%, 64%); }
+.project-status[data-status="in progress"]::before { background: #e0a030; }
+
+.project-summary { text-align: center; font-size: 1.1em; color: #4a5568; max-width: 40em; margin: .4em auto 1em; }
+.project-header .project-tags { justify-content: center; }
+.project-meta { display: flex; flex-wrap: wrap; justify-content: center; align-items: center; gap: .6em 1.4em; margin: 1em 0 1.5em; font-size: .95em; color: #6b7280; }
+.project-btn {
+  display: inline-block; padding: .35em 1em; border-radius: 4px; border: 1px solid hsl(232, 61%, 64%);
+  color: hsl(232, 61%, 64%); font-size: .95em;
+}
+.project-btn:hover { background: hsl(232, 61%, 64%); color: #fff; border-color: hsl(232, 61%, 64%); }
+.project-btn.primary { background: hsl(232, 61%, 64%); color: #fff; }
+.project-btn.primary:hover { background: hsl(232, 61%, 54%); }
+.project-back { text-align: center; margin-top: 2em; }
+
+.project-content figure, figure.project-video { margin: 1.5em auto; text-align: center; }
+.project-content figure img { max-width: 100%; height: auto; }
+figure.project-video video { display: block; margin: 0 auto; width: 100%; max-width: 420px; max-height: 75vh; background: #000; border-radius: 6px; }
+figure.project-video.wide video { max-width: 100%; }
+figure.project-video figcaption, .project-content figcaption { margin-top: .5em; font-size: .9em; color: #6b7280; }
+.project-content table { margin: 1em auto; }
+@media (max-width: 600px) { .project-grid { grid-template-columns: 1fr; } }
+</style>

layouts/projects/list.html

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+{{ define "title" }}{{ .Title }} - {{ .Site.Title }}{{ end }}
+
+{{ define "content" }}
+{{ partial "projects/styles.html" . }}
+<article class="post">
+  {{- with .Content }}<div class="post-content">{{ . }}</div>{{ end }}
+
+  <div class="project-grid">
+    {{- range .Pages.ByDate.Reverse }}
+    {{- $cover := .Resources.GetMatch (.Params.cover | default "cover.*") -}}
+    <div class="project-card">
+      {{- if $cover }}
+      <a class="project-card-cover" href="{{ .RelPermalink }}" tabindex="-1" aria-hidden="true">
+        <img src="{{ $cover.RelPermalink }}" alt="" loading="lazy">
+      </a>
+      {{- else }}
+      <a class="project-card-cover placeholder" href="{{ .RelPermalink }}" tabindex="-1" aria-hidden="true">{{ index (split .Title ":") 0 }}</a>
+      {{- end }}
+      <div class="project-card-body">
+        <h2 class="project-card-title"><a href="{{ .RelPermalink }}">{{ .Title }}</a></h2>
+        {{- with .Params.summary }}<p class="project-card-summary">{{ . }}</p>{{ end }}
+        <div class="project-card-footer">
+          {{- with .Params.status }}<span class="project-status" data-status="{{ . | lower }}">{{ . }}</span>{{ else }}<span></span>{{ end }}
+          {{- with .Params.repo }}<a href="{{ . }}" target="_blank" rel="noopener">Source code ↗</a>{{ end }}
+        </div>
+      </div>
+    </div>
+    {{- end }}
+  </div>
+</article>
+{{ end }}

layouts/projects/single.html

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+{{ define "title" }}{{ .Title }} - {{ .Site.Title }}{{ end }}
+
+{{ define "content" }}
+{{ partial "projects/styles.html" . }}
+<article class="post project-page">
+  <header class="post-header project-header">
+    <h1 class="post-title">{{ .Title }}</h1>
+    {{- with .Params.summary }}<p class="project-summary">{{ . }}</p>{{ end }}
+    <div class="project-meta">
+      {{- with .Params.status }}<span class="project-status" data-status="{{ . | lower }}">{{ . }}</span>{{ end }}
+      {{- if not .Date.IsZero }}<span>{{ .Date.Format "January 2006" }}</span>{{ end }}
+      {{- with .Params.repo }}<a class="project-btn primary" href="{{ . }}" target="_blank" rel="noopener">Source code ↗</a>{{ end }}
+      {{- with .Params.docs }}<a class="project-btn" href="{{ . }}" target="_blank" rel="noopener">Documentation</a>{{ end }}
+      {{- with .Params.pypi }}<a class="project-btn" href="{{ . }}" target="_blank" rel="noopener">PyPI</a>{{ end }}
+    </div>
+  </header>
+  <div class="post-content project-content">
+    {{ .Content }}
+  </div>
+  <p class="project-back"><a href="{{ .Parent.RelPermalink }}">← All projects</a></p>
+</article>
+{{ end }}

layouts/shortcodes/video.html

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+{{- $src := .Get "src" | default (.Get 0) -}}
+{{- $caption := .Get "caption" -}}
+{{- $poster := .Get "poster" -}}
+{{- with .Page.Resources.GetMatch $src }}{{ $src = .RelPermalink }}{{ end -}}
+{{- with $poster }}{{ with $.Page.Resources.GetMatch . }}{{ $poster = .RelPermalink }}{{ end }}{{ end -}}
+<figure class="project-video">
+  <video controls preload="metadata" playsinline{{ with $poster }} poster="{{ . }}"{{ end }}>
+    <source src="{{ $src }}" type="video/mp4">
+    Your browser does not support the video tag. <a href="{{ $src }}">Download the video</a>.
+  </video>
+  {{- with $caption }}<figcaption>{{ . | markdownify }}</figcaption>{{ end }}
+</figure>