UAV Simulator Project

Overview

This repository contains a custom-built UAV simulation framework that models the dynamics and control of a small fixed‑wing aircraft.
It integrates:

• Nonlinear flight dynamics derived from standard aircraft equations of motion.
• Trim calculation routines to establish equilibrium states for specific flight conditions.
• Linearization methods that generate transfer‑function and state‑space representations for control design and analysis.
• 3D rendering and visualization of the aircraft geometry, body axes, and simulation outputs.

The project serves as a foundation for experimenting with guidance, navigation, and control (GNC) algorithms, while providing an educational platform for testing new ideas in flight dynamics.

📖 Project Documentation (Doxygen):
https://msk2000.github.io/UAV-Simulator

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Demo footage showing slider controls, trim computation, computation of state space models, unfinished waypoint navigation, real-time state plotting etc:

Trim_demo_aug_2_c.mp4

Older Demo footage illustrating path and waypoint generation, real-time state plotting, slider based aircraft control:

UAV_Update.mp4

A texture mapped terrain and control demo footage:

terrain_control_conv.mp4

A stall demo footage (old):

mid_oct_stall_demo.mp4

Current Status

Active Development:
The simulator has been rebuilt after an earlier data loss, and a working baseline is already running.
At present you can:

• Load an aircraft configuration and compute trim for given airspeed and flight‑path parameters.
• Generate preliminary state‑space and transfer‑function models around the trim condition.
• Run the dynamics in a custom C++ simulation loop with live 3D visualization.

Soon you should be able to provide a path to the UAV and watch it generate waypoints and use an autopilot to navigate itself to the destination autonomously :D

Recent Changelog:

26th July 2025

• Documentation: Doxygen workflow set up. Documentation is now automatically generated and published online at https://msk2000.github.io/UAV-Simulator.

25th July 2025

• Trim: Implemented automated trim point calculation and corresponding control settings and sim initialisation.
• Memory Leaks: Fixed some memory leak bugs.
• Waypoint Navigation: Work on waypoint navigation started. A sample path (in red) and waypoints(yellow) can be seen in the most recent update video.
• ImGUI/ImPlot: Live plotting of state variables integrated into simulation (see recent video). A control panel for elevator,rudder, aileron and throttle input has been added to the gui.

6th July 2025

• Terrain Texture Mapping: Implemented texture mapping on the STL terrain using UV coordinates and a texture image. Normalized and tiled the UVs for consistent texture scaling.
• Texture Wrap Mode: Set texture wrap mode to REPEAT to allow seamless tiling across the terrain surface.
• Coordinate Adjustment: Corrected UV mapping to use the X and Y axes (pos[0], pos[1]) instead of X and Z, since Z is the up-axis in this simulator.
• Shadow Rendering: Attempted basic hard shadow support for the aircraft model using Easy3D's Shadow class. Pending Implementation.
• HUD Implementation: Integrated a Heads-Up Display (HUD) in the viewer using Easy3D's TextRenderer. The HUD overlays real-time flight data from the aircraft onto the screen during simulation.
• Viewer Improvements: Introduced a new TestViewer class derived from Easy3D’s Viewer. This class handles aircraft HUD rendering, user input for aircraft control, and shadow rendering(incomplete).

28th October 2024

• Runga-Kutta 4: Changed the simplistic solver to RK4 based integrator for much better estimation of state parameters.

20th October 2024

• Modularization: Refactored the forces and moments function from a monolithic structure to a more modular design for improved clarity and maintainability.
• Dynamics Function: Transitioned the dynamics function to a modular structure, facilitating easier updates and modifications.
• Animation Cleanup: Cleaned up the animation function by introducing an update function that manages all necessary updates to the simulation before rendering.
• Coordinate Frame: Added a body frame coordinate system that is always visible and coincident with the aircraft, providing a consistent reference for the simulation.

16th October 2024

• Visualisation Method: Changed the simple vertex/face based rendering to surface mesh based one allowing for import of any 3d model into the simulator.
• Changes to Aircraft Class: Removed multiple depricated functionds and added new ones to help with the new render system.

Features

• Aircraft Dynamics: Models the physical characteristics and flight dynamics of an aircraft.
• State Tracking: Tracks various state variables including position, velocity, and orientation.
• Control Inputs: Handles different control inputs such as throttle, aileron, elevator, and rudder.
• 3D Rendering: Uses Easy3D for rendering and visualizing aircraft dynamics in a 3D environment.
• Graphing: Includes basic functionality for plotting and analyzing aircraft state data.

Dependencies

This project relies on the following libraries:

• Eigen: For linear algebra operations.
• ImGui: For in‑application graphical user interfaces (sliders, panels, etc.).
• ImPlot: For real‑time plotting integrated with ImGui.
• Doxygen: For generating documentation from source code.
• Easy3D: For 3D visualization and rendering.
• NLOpt: For nonlinear optimization used in trim and control routines.

Building and Running the Project

To build and run UAV-Simulator, you need a system with the required dependencies installed and CMake available.

1. Clone the repository

git clone https://github.com/msk2000/UAV-Simulator.git
cd UAV-Simulator

2. Install dependencies

Make sure these libraries and tools are installed on your system (install paths may vary):

• Eigen (header‑only)
• Easy3D (set Easy3D_DIR accordingly in CMakeLists.txt)
• ImGui and ImPlot (already included in the repo or via Easy3D’s 3rd_party)
• NLopt (for trim and optimization)
• Python 3 development headers and NumPy (for certain computations)
• OpenGL and GLFW development packages
• CMake (version 3.0 or newer)

3. Configure and build with CMake

From the root of the project:

mkdir build
cd build
cmake ..
make -j$(nproc)

4. Run the simulation

From inside the build/ directory:

./UAVSim

Known Issues

• Data Loss: Recent updates to the project have been lost. The current code is a recovery of an older, less developed version.
• Incomplete Features: The project is still under development, and some features are not fully implemented or tested.

Future Work

• Autopilot System: Implement a closed‑loop control framework to stabilize the UAV and follow desired flight commands automatically.
• Guidance Algorithm: Develop algorithms to generate and update flight paths or waypoint sequences in real time for autonomous navigation.
• Navigation: Integrate real‑time state estimation to accurately track the UAV’s position, velocity, and attitude during flight.
• Linearisation and State‑Space Models: Create routines to linearize nonlinear flight dynamics around trim conditions and generate state‑space models for control design and analysis.
• Transfer Function Integration: Implement methods to derive and analyze transfer functions for key control channels, enabling frequency‑domain tuning and analysis.

Class Members for Aircraft Simulation

The following table details the key parameters used in the simulation. These parameters represent the physical properties, control inputs, and initial conditions of the aircraft. This table will help you understand both the class members and the data.txt file that the simulator uses to load a given UAV configuration.

#	Parameter	Description
1	mass	Aircraft mass in kilograms.
2	Jx	Moment of inertia about the x-axis (roll) in kg·m².
3	Jy	Moment of inertia about the y-axis (pitch) in kg·m².
4	Jz	Moment of inertia about the z-axis (yaw) in kg·m².
5	Jxz	Product of inertia for coupling between the x and z axes.
6	S_wing	Wing surface area in square meters.
7	b	Wingspan in meters.
8	c	Mean aerodynamic chord length in meters.
9	e	Oswald efficiency factor.
10	g	Gravitational acceleration constant (9.81 m/s²).
11	rho	Air density in kg/m³.
12	k_motor	Motor constant representing the relationship between motor speed and thrust.
13	S_prop	Propeller surface area in square meters.
14	k_T_P	Motor torque constant (to be defined based on propeller efficiency).
15	k_Omega	Propeller rotational speed constant (to be defined based on efficiency).
16	C_L_0	Zero-lift coefficient of lift.
17	C_L_alpha	Lift curve slope, relating angle of attack to lift.
18	C_L_q	Lift coefficient due to pitch rate.
19	C_L_delta_e	Lift coefficient due to elevator deflection.
20	C_D_0	Zero-lift drag coefficient (parasitic drag).
21	C_D_alpha	Drag coefficient as a function of angle of attack.
22	C_D_p	Drag coefficient due to roll rate.
23	C_D_q	Drag coefficient due to pitch rate.
24	C_D_delta_e	Drag coefficient due to elevator deflection.
25	C_m_0	Zero-lift moment coefficient.
26	C_m_alpha	Moment coefficient due to angle of attack.
27	C_m_q	Moment coefficient due to pitch rate.
28	C_m_delta_e	Moment coefficient due to elevator deflection.
29	C_Y_0	Zero-sideslip yaw force coefficient.
30	C_Y_beta	Yaw force coefficient due to sideslip angle (lateral stability).
31	C_Y_p	Yaw force coefficient due to roll rate.
32	C_Y_r	Yaw force coefficient due to yaw rate.
33	C_Y_delta_a	Yaw force coefficient due to aileron deflection.
34	C_Y_delta_r	Yaw force coefficient due to rudder deflection.
35	C_ell_0	Roll moment coefficient at zero sidesli
36	C_ell_beta	Roll moment coefficient due to sideslip angle.
37	C_ell_p	Roll moment coefficient due to roll rate.
38	C_ell_r	Roll moment coefficient due to yaw rate.
39	C_ell_delta_a	Roll moment coefficient due to aileron deflection.
40	C_ell_delta_r	Roll moment coefficient due to rudder deflection.
41	C_n_0	Zero-yaw moment coefficient.
42	C_n_beta	Yaw moment coefficient due to sideslip angle (lateral stability).
43	C_n_p	Yaw moment coefficient due to roll rate.
44	C_n_r	Yaw moment coefficient due to yaw rate.
45	C_n_delta_a	Yaw moment coefficient due to aileron deflection.
46	C_n_delta_r	Yaw moment coefficient due to rudder deflection.
47	C_prop	Propeller thrust coefficient.
48	M	Transition Rate used for Stall Characteristic modelling
49	epsilon	Downwash gradient coefficient.
50	alpha0	Zero-lift angle of attack.
51	pn0	Initial position in the North direction (in meters).
52	pe0	Initial position in the East direction (in meters).
53	pd0	Initial position in the Down direction (negative altitude, in meters).
54	u0	Initial velocity along the body x-axis (forward velocity).
55	v0	Initial velocity along the body y-axis (side-slip velocity).
56	w0	Initial velocity along the body z-axis (vertical velocity).
57	phi0	Initial roll angle (in radians).
58	theta0	Initial pitch angle (in radians).
59	psi0	Initial yaw angle (in radians).
60	p0	Initial roll rate (body frame).
61	q0	Initial pitch rate (body frame).
62	r0	Initial yaw rate (body frame).
63	delta_t	Throttle input (ranging from 0 to 1).
64	delta_a	Aileron deflection (control surface input for roll control).
65	delta_e	Elevator deflection (control surface input for pitch control).
66	delta_r	Rudder deflection (control surface input for yaw control).
67	delta_t_max	Maximum throttle setting.
68	delta_t_min	Minimum throttle setting.
69	delta_a_max	Maximum aileron deflection.
70	delta_a_min	Minimum aileron deflection.
71	delta_e_max	Maximum elevator deflection.
72	delta_e_min	Minimum elevator deflection.
73	delta_r_max	Maximum rudder deflection.
74	delta_r_min	Minimum rudder deflection.

Usage

Each of these parameters is used to model the dynamics of the aircraft in simulation, ensuring that the response to control inputs and environmental factors is accurate. For more details, refer to the implementation in aircraft.h. Additional details about how to obtain these parameters for a given UAV will be provided in the future.

Contributing

Contributions to the project are welcome. If you'd like to help improve the project, please fork the repository and submit a pull request with your changes.