Jongann Lee

Geometric Tracking Controller for a Multirotor UAV with Collective Pitch-Tilting

Mon, 25 Nov 2024 00:00:00 +0000

PIEJAM(Passive Inversion and Eversion Joint Ankle Mechanism)

Fri, 11 Oct 2024 00:00:00 +0000

Inversion and eversion is the rotation of the foot about the axis parallel to the toes. In simpler terms, its the rotation that makes the bottom of your foot face the left or right. This movement is crucial for maintaining balance and traversing uneven terrain. Yet many current ankle exoskeletons do not allow the user to perform inversion and eversion. The goal of this project was to develop an inversion and eversion ankle joint mechanism that would allow augment this capability to an existing ankle exoskeleton(speifically PERL from POLAR lab at Polytechnique Montreal).

The primary feature of this mechanism is the compliant mechanism based joint. Typical revolute joints use bearings and pins to create the rotational degree of freedom, but this increases the complexity and manufacturing and maintaining the joint. PIEJAM uses compliant mechanisms, which are flexible mechanisms that achieve force and motion transmission through elastic body deformation. It has been implemented in the form of a x-shaped cross-axis flexural pivot, which enables the rotational motion and at the same time provides adverse torque feedback like a torsional spring. The overall joint mechanism designs also limits the range of motion, which is important for preventing injuries.

A test of using PIEJAM with PERL showed that the desired inversion and eversion movenemt charactertistics while not comprimising the requirements for dorsalflexion and plantarflexion actuation.

Reinforcement Learning based Tuner for the Geometric Tracking Attitude Controller

Wed, 05 Jun 2024 00:00:00 +0000

PID controllers are widely used across many applications including quadrotors. A variant of the PD controller is the geometric tracking controller, which utilizes the rotation matrix and the non-linear quadrotor dynamics. However, PID controllers require gain tuning, and their fixed gains render them incapable of responding to changes in the system in real-time. We propose a reinforcement learning based tuner for the attitude controller gains, which updates the gain in real time based on the history of the vehicle attitude error. The trained RL tuner is shown to be capable of stabilizing a vehicle with an unstable initial controller gain.

Unicycle Control using Disturbance Observer

Fri, 01 Dec 2023 00:00:00 +0000

This was a project done as part of the advanced control methods class, where the goal was to freely implement a controller that was taught during class. One of the control methods taught was the disturbance observer or DOB. DOB makes the inner loop dynamics behave like the nominal plant, eliminating the effects of model uncertainty. It also has an added bonus of disturbance rejection making it a very versatile controller. This project implemented a DOB inner loop to a unicycle, which had previously been controlled using a PD controller. The PD controller was designed using the linearized plant dynamics. The goal of the DOB was to improve the controller’s performance on the real, non-linear plant dynamics by stabilizing the plant behaviour while under control. A Simulink simulation of the controller confirmed the improvement in performance. While there was an improvement in performance, the overall robustness of the original PD controller meant that the improvement in performance was marginal.

Blog with Jupyter Notebooks!

Sat, 04 Nov 2023 00:00:00 +0000

from IPython.core.display import Image
Image('https://www.python.org/static/community_logos/python-logo-master-v3-TM-flattened.png')

print("Welcome to Academic!")

Welcome to Academic!

Organize your notebooks

Place the notebooks that you would like to publish in a notebooks folder at the root of your website.

Import the notebooks into your site

pipx install academic
academic import 'notebooks/**.ipynb' content/post/ --verbose

The notebooks will be published to the folder you specify above. In this case, they will be published to your content/post/ folder.

Adaptive Quadrotor Controller

Sun, 01 Oct 2023 00:00:00 +0000

Adaptive control laws allow for stable control of the agent even when the system parameters vary over time. Therefore, adaptive control laws are useful to quadrotors, whose system parameters such as mass and moment of inertia are subject to uncertain measurements and variations over time.

Most adaptive control laws use a simple Euclidian distance between the real and estimated inertial parameters. This however, poses issues as the manifold of physically consistent inertial parameters is not a simple Euclidian space. Thus, the Euclidian distance is an inaccurate distance metric and could potentially assign physically inconsistent values to the estiamted inertial parameters.

We propose using the geodesic distance on the manifold of physically consistent inertial parameters. This is a more accurate distance metric and ensures that the estimated inertial parameters are physically consistent.

The adaptive control scheme is then combined with the geometric tracking controller for the quadrotor, a trajectory tracking controller that is proven to be stable even with near inverted attitude. The adaptive quadrotor controller was simulated in Matlab where the improvement in performance was confirmed.

Autonomous Quadrotor System for Payload Delivery

Tue, 01 Aug 2023 00:00:00 +0000

During my undergraduate studies, I was a member, and later president, of the Seoul National University drone club Bulnabi. Over the years, I have participated in many projects within the club, but the 2023 Korea Robot Aircraft Competition is the one that I worked on the hardest, and therefore I chose to discuss it here.

The objective of the competition could be split into several parts. The aircraft had to take off and fly in a stable manner automatically without human input. Next, it had to navigate between two ladders and fly inbetween them. After doing this, the vehicle had to locate the delivery point located on the third floor balcony, which had been marked with a cross. A pizza box would then be delivered and the drone would return to a designated position and land automatically.

All of the above mentioned tasks had to be performed automatically without human intervention. For this, we decided to utilize two computers: a Pixhawk flight computer(FC) running PX4, and a NVIDIA Jetson Xavier companion computer(CC) running ROS2. The CC would take sensor data, such as camera images, and use it to determine the action needed to be taken (go forward, release cargo etc.). The FC would then receive these actions and calculate the appropriate commands to be given to the motors in order to follow the action and maintain stability at the same time.

This requires a good communications bridge between the FC and the CC. I implmented a communications bridge between the PX4-Autopilot FC software and the ROS2 software on the CC by utilizing the XRCE-DDS prptocol. This protocol was used to convert ROS2 messages into uORB messages used by PX4, which allowed the FC to send vehicle sensor data to the CC, and for the CC to send kinematic commands to the FC.

I also worked on the trajectory generation module, which was necessary to continously provide a smoothe trajectory for the vehicle to follow. The module utilized a 4-point Bezier curve, which was defined using the current position, current velocity, desired position, and desired velocity. The design allowed the vehicle to smoothly enter from the current state and exit to the desired state in a continous manner as well.

Welcome to Hugo Blox Builder, the website builder for Hugo

Sun, 13 Dec 2020 00:00:00 +0000

import libr
print('hello')

Overview

The Wowchemy website builder for Hugo, along with its starter templates, is designed for professional creators, educators, and teams/organizations - although it can be used to create any kind of site
The template can be modified and customised to suit your needs. It’s a good platform for anyone looking to take control of their data and online identity whilst having the convenience to start off with a no-code solution (write in Markdown and customize with YAML parameters) and having flexibility to later add even deeper personalization with HTML and CSS
You can work with all your favourite tools and apps with hundreds of plugins and integrations to speed up your workflows, interact with your readers, and much more

Get Started

👉 Create a new site
📚 Personalize your site
💬 Chat with the Wowchemy community or Hugo community
🐦 Twitter: @wowchemy @GeorgeCushen #MadeWithWowchemy
💡 Request a feature or report a bug for Wowchemy
⬆️ Updating Wowchemy? View the Update Tutorial and Release Notes

Crowd-funded open-source software

To help us develop this template and software sustainably under the MIT license, we ask all individuals and businesses that use it to help support its ongoing maintenance and development via sponsorship.

As a token of appreciation for sponsoring, you can unlock these awesome rewards and extra features 🦄✨

Ecosystem

Hugo Academic CLI: Automatically import publications from BibTeX

Inspiration

Check out the latest demo of what you’ll get in less than 10 minutes, or view the showcase of personal, project, and business sites.

Features

Page builder - Create anything with widgets and elements
Edit any type of content - Blog posts, publications, talks, slides, projects, and more!
Create content in Markdown, Jupyter, or RStudio
Plugin System - Fully customizable color and font themes
Display Code and Math - Code highlighting and LaTeX math supported
Integrations - Google Analytics, Disqus commenting, Maps, Contact Forms, and more!
Beautiful Site - Simple and refreshing one page design
Industry-Leading SEO - Help get your website found on search engines and social media
Media Galleries - Display your images and videos with captions in a customizable gallery
Mobile Friendly - Look amazing on every screen with a mobile friendly version of your site
Multi-language - 34+ language packs including English, 中文, and Português
Multi-user - Each author gets their own profile page
Privacy Pack - Assists with GDPR
Stand Out - Bring your site to life with animation, parallax backgrounds, and scroll effects
One-Click Deployment - No servers. No databases. Only files.

Themes

Wowchemy and its templates come with automatic day (light) and night (dark) mode built-in. Alternatively, visitors can choose their preferred mode - click the moon icon in the top right of the Demo to see it in action! Day/night mode can also be disabled by the site admin in params.toml.

Choose a stunning theme and font for your site. Themes are fully customizable.

License

Released under the MIT license.

Writing technical content in Markdown

Fri, 12 Jul 2019 00:00:00 +0000

Hugo Blox Builder is designed to give technical content creators a seamless experience. You can focus on the content and Wowchemy handles the rest.

Highlight your code snippets, take notes on math classes, and draw diagrams from textual representation.

On this page, you’ll find some examples of the types of technical content that can be rendered with Wowchemy.

Examples

Code

Wowchemy supports a Markdown extension for highlighting code syntax. You can customize the styles under the syntax_highlighter option in your config/_default/params.yaml file.

```python
import pandas as pd
data = pd.read_csv("data.csv")
data.head()
```

renders as

import pandas as pd
data = pd.read_csv("data.csv")
data.head()

Mindmaps

Wowchemy supports a Markdown extension for mindmaps.

Simply insert a Markdown markmap code block and optionally set the height of the mindmap as shown in the example below.

A simple mindmap defined as a Markdown list:


```markmap {height="200px"}
- Hugo Modules
- wowchemy
- blox-plugins-netlify
- blox-plugins-netlify-cms
- blox-plugins-reveal
```

renders as

- Hugo Modules
- wowchemy
- blox-plugins-netlify
- blox-plugins-netlify-cms
- blox-plugins-reveal

A more advanced mindmap with formatting, code blocks, and math:


```markmap
- Mindmaps
- Links
- [Wowchemy Docs](https://docs.hugoblox.com/)
- [Discord Community](https://discord.gg/z8wNYzb)
- [GitHub](https://github.com/HugoBlox/hugo-blox-builder)
- Features
- Markdown formatting
- **inline** ~~text~~ *styles*
- multiline
text
- `inline code`
-
```js
console.log('hello');
console.log('code block');
```
- Math: $x = {-b \pm \sqrt{b^2-4ac} \over 2a}$
```

renders as

- Mindmaps
- Links
- [Wowchemy Docs](https://docs.hugoblox.com/)
- [Discord Community](https://discord.gg/z8wNYzb)
- [GitHub](https://github.com/HugoBlox/hugo-blox-builder)
- Features
- Markdown formatting
- **inline** ~~text~~ *styles*
- multiline
text
- `inline code`
-
```js
console.log('hello');
console.log('code block');
```
- Math: $x = {-b \pm \sqrt{b^2-4ac} \over 2a}$

Charts

Wowchemy supports the popular Plotly format for interactive charts.

Save your Plotly JSON in your page folder, for example line-chart.json, and then add the {{< chart data="line-chart" >}} shortcode where you would like the chart to appear.

Demo:

You might also find the Plotly JSON Editor useful.

Math

Wowchemy supports a Markdown extension for $\LaTeX$ math. You can enable this feature by toggling the math option in your config/_default/params.yaml file.

To render inline or block math, wrap your LaTeX math with {{< math >}}$...${{< /math >}} or {{< math >}}$$...$${{< /math >}}, respectively. (We wrap the LaTeX math in the Wowchemy math shortcode to prevent Hugo rendering our math as Markdown. The math shortcode is new in v5.5-dev.)

Example math block:

{{< math >}}
$$
\gamma_{n} = \frac{ \left | \left (\mathbf x_{n} - \mathbf x_{n-1} \right )^T \left [\nabla F (\mathbf x_{n}) - \nabla F (\mathbf x_{n-1}) \right ] \right |}{\left \|\nabla F(\mathbf{x}_{n}) - \nabla F(\mathbf{x}_{n-1}) \right \|^2}
$$
{{< /math >}}

renders as

$$\gamma_{n} = \frac{ \left | \left (\mathbf x_{n} - \mathbf x_{n-1} \right )^T \left [\nabla F (\mathbf x_{n}) - \nabla F (\mathbf x_{n-1}) \right ] \right |}{\left \|\nabla F(\mathbf{x}_{n}) - \nabla F(\mathbf{x}_{n-1}) \right \|^2}$$

Example inline math {{< math >}}$\nabla F(\mathbf{x}_{n})${{< /math >}} renders as $\nabla F(\mathbf{x}_{n})$.

Example multi-line math using the math linebreak (\\):

{{< math >}}
$$f(k;p_{0}^{*}) = \begin{cases}p_{0}^{*} & \text{if }k=1, \\
1-p_{0}^{*} & \text{if }k=0.\end{cases}$$
{{< /math >}}

renders as

$$ f(k;p_{0}^{*}) = \begin{cases}p_{0}^{*} & \text{if }k=1, \\ 1-p_{0}^{*} & \text{if }k=0.\end{cases} $$

Diagrams

Wowchemy supports a Markdown extension for diagrams. You can enable this feature by toggling the diagram option in your config/_default/params.toml file or by adding diagram: true to your page front matter.

An example flowchart:

```mermaid
graph TD
A[Hard] -->|Text| B(Round)
B --> C{Decision}
C -->|One| D[Result 1]
C -->|Two| E[Result 2]
```

renders as

graph TD A[Hard] -->|Text| B(Round) B --> C{Decision} C -->|One| D[Result 1] C -->|Two| E[Result 2]

An example sequence diagram:

```mermaid
sequenceDiagram
Alice->>John: Hello John, how are you?
loop Healthcheck
John->>John: Fight against hypochondria
end
Note right of John: Rational thoughts!
John-->>Alice: Great!
John->>Bob: How about you?
Bob-->>John: Jolly good!
```

renders as

sequenceDiagram Alice->>John: Hello John, how are you? loop Healthcheck John->>John: Fight against hypochondria end Note right of John: Rational thoughts! John-->>Alice: Great! John->>Bob: How about you? Bob-->>John: Jolly good!

An example Gantt diagram:

```mermaid
gantt
section Section
Completed :done, des1, 2014-01-06,2014-01-08
Active :active, des2, 2014-01-07, 3d
Parallel 1 : des3, after des1, 1d
Parallel 2 : des4, after des1, 1d
Parallel 3 : des5, after des3, 1d
Parallel 4 : des6, after des4, 1d
```

renders as

gantt section Section Completed :done, des1, 2014-01-06,2014-01-08 Active :active, des2, 2014-01-07, 3d Parallel 1 : des3, after des1, 1d Parallel 2 : des4, after des1, 1d Parallel 3 : des5, after des3, 1d Parallel 4 : des6, after des4, 1d

An example class diagram:

```mermaid
classDiagram
Class01 <|-- AveryLongClass : Cool
Class03 *-- Class04
Class05 o-- Class06
Class07 .. Class08
Class09 --> C2 : Where am i?
Class09 --* C3
Class09 --|> Class07
Class07 : equals()
Class07 : Object[] elementData
Class01 : size()
Class01 : int chimp
Class01 : int gorilla
Class08 <--> C2: Cool label
```

renders as

classDiagram Class01 <|-- AveryLongClass : Cool Class03 *-- Class04 Class05 o-- Class06 Class07 .. Class08 Class09 --> C2 : Where am i? Class09 --* C3 Class09 --|> Class07 Class07 : equals() Class07 : Object[] elementData Class01 : size() Class01 : int chimp Class01 : int gorilla Class08 <--> C2: Cool label

An example state diagram:

```mermaid
stateDiagram
[*] --> Still
Still --> [*]
Still --> Moving
Moving --> Still
Moving --> Crash
Crash --> [*]
```

renders as

stateDiagram [*] --> Still Still --> [*] Still --> Moving Moving --> Still Moving --> Crash Crash --> [*]

Todo lists

You can even write your todo lists in Markdown too:

- [x] Write math example
 - [x] Write diagram example
- [ ] Do something else

renders as

Write math example
- Write diagram example
Do something else

Tables

Save your spreadsheet as a CSV file in your page’s folder and then render it by adding the Table shortcode to your page:

{{< table path="results.csv" header="true" caption="Table 1: My results" >}}

renders as

Table 1: My results
customer_id	score
1	0
2	0.5
3	1

Callouts

Academic supports a shortcode for callouts, also referred to as asides, hints, or alerts. By wrapping a paragraph in {{% callout note %}} ... {{% /callout %}}, it will render as an aside.

{{% callout note %}}
A Markdown aside is useful for displaying notices, hints, or definitions to your readers.
{{% /callout %}}

renders as

A Markdown aside is useful for displaying notices, hints, or definitions to your readers.

Spoilers

Add a spoiler to a page to reveal text, such as an answer to a question, after a button is clicked.

{{< spoiler text="Click to view the spoiler" >}}
You found me!
{{< /spoiler >}}

renders as

Click to view the spoiler

You found me!

Icons

Academic enables you to use a wide range of icons from Font Awesome and Academicons in addition to emojis.

Here are some examples using the icon shortcode to render icons:

{{< icon name="terminal" pack="fas" >}} Terminal
{{< icon name="python" pack="fab" >}} Python
{{< icon name="r-project" pack="fab" >}} R

renders as

Terminal
Python
R

Slides

Tue, 05 Feb 2019 00:00:00 +0000

Create slides in Markdown with Hugo Blox Builder

Hugo Blox Builder | Documentation

Features

Efficiently write slides in Markdown
3-in-1: Create, Present, and Publish your slides
Supports speaker notes
Mobile friendly slides

Controls

Next: Right Arrow or Space
Previous: Left Arrow
Start: Home
Finish: End
Overview: Esc
Speaker notes: S
Fullscreen: F
Zoom: Alt + Click
PDF Export

Code Highlighting

Inline code: variable

Code block:

porridge = "blueberry"
if porridge == "blueberry":
 print("Eating...")

Math

In-line math: $x + y = z$

Block math:

$$ f\left( x \right) = ;\frac{{2\left( {x + 4} \right)\left( {x - 4} \right)}}{{\left( {x + 4} \right)\left( {x + 1} \right)}} $$

Fragments

Make content appear incrementally

{{% fragment %}} One {{% /fragment %}}
{{% fragment %}} **Two** {{% /fragment %}}
{{% fragment %}} Three {{% /fragment %}}

Press Space to play!

One Two Three

A fragment can accept two optional parameters:

class: use a custom style (requires definition in custom CSS)
weight: sets the order in which a fragment appears

Speaker Notes

Add speaker notes to your presentation

{{% speaker_note %}}

- Only the speaker can read these notes
- Press `S` key to view
 {{% /speaker_note %}}

Press the S key to view the speaker notes!

Themes

black: Black background, white text, blue links (default)
white: White background, black text, blue links
league: Gray background, white text, blue links
beige: Beige background, dark text, brown links
sky: Blue background, thin dark text, blue links

night: Black background, thick white text, orange links
serif: Cappuccino background, gray text, brown links
simple: White background, black text, blue links
solarized: Cream-colored background, dark green text, blue links

Custom Slide

Customize the slide style and background

{{< slide background-image="/media/boards.jpg" >}}
{{< slide background-color="#0000FF" >}}
{{< slide class="my-style" >}}

Custom CSS Example

Let’s make headers navy colored.

Create assets/css/reveal_custom.css with:

.reveal section h1,
.reveal section h2,
.reveal section h3 {
 color: navy;
}

Questions?

Ask

Documentation

An example journal article

Tue, 01 Sep 2015 00:00:00 +0000

Click the Cite button above to demo the feature to enable visitors to import publication metadata into their reference management software.

Create your slides in Markdown - click the Slides button to check out the example.

Add the publication’s full text or supplementary notes here. You can use rich formatting such as including code, math, and images.

An example conference paper

Mon, 01 Jul 2013 00:00:00 +0000

Click the Cite button above to demo the feature to enable visitors to import publication metadata into their reference management software.

Create your slides in Markdown - click the Slides button to check out the example.

Add the publication’s full text or supplementary notes here. You can use rich formatting such as including code, math, and images.

Jongann Lee

Geometric Tracking Controller for a Multirotor UAV with Collective Pitch-Tilting

PIEJAM(Passive Inversion and Eversion Joint Ankle Mechanism)

Reinforcement Learning based Tuner for the Geometric Tracking Attitude Controller

Unicycle Control using Disturbance Observer

Blog with Jupyter Notebooks!

Organize your notebooks

Import the notebooks into your site

Adaptive Quadrotor Controller

Autonomous Quadrotor System for Payload Delivery

Welcome to Hugo Blox Builder, the website builder for Hugo

Overview

Get Started

Crowd-funded open-source software

❤️ Click here to become a sponsor and help support Wowchemy’s future ❤️

Ecosystem

Inspiration

Features

Themes

License

Writing technical content in Markdown

Examples

Code

Mindmaps

Charts

Math

Diagrams

Todo lists

Tables

Callouts

Spoilers

Icons

Did you find this page helpful? Consider sharing it 🙌

Slides

Create slides in Markdown with Hugo Blox Builder

Features

Controls

Code Highlighting

Math

Fragments

Speaker Notes

Themes

Custom Slide

Custom CSS Example

Questions?

An example journal article

An example conference paper