Model Rocket Simulator oriented to the design and tuning of active control systems, be them in the form of TVC, Active Fin Control or just parachute deployment algorithms on passively stable rockets. It is able to simulate non-linear actuator dynamics and has some limited Software in the Loop capabilities. The program computes all the subsonic aerodynamic parameters of interest and integrates the 3DOF Equations of Motion to simulate the complete flight.
This is a Model Rocket Simulator oriented towards active stabilization. It integrates the Three Degree of Freedom Equations of Motion, allowing to tune controllers used in Model Rockets. There is pre-coded controller in the file src/control.py, one can use it or run the Flight Computer's software through Software in the Loop.
The program computes the 3DoF Equations of Motion of the Rocket and integrates their result with the trapezoidal rule. The Aerodynamic Coefficients are calculated using the same Extended Barrowman Equations that Open Rocket uses (plus some modifications). The fins' forces are computed with interpolated wind tunnel data and Diederich's Semi-Empirical Method to accurately model the behaviour for every aspect ratio and angle of attack. The program also allows for fins separated from the body. More information can be found in the technical documentation or inside src/simulation/main_simulation.py, src/aerodynamics/rocket_functions.py or src/aerodynamics/fin_aerodynamics.py
Without the optional dependencies, the Software in the Loop module will not work.
If someone can make an .exe that works with VPython, please let me know.
The setup of the rocket is fairly simple. However, the program is not meant for designing the rocket. Open Rocket is a more comfortable option.
To run the program, run AeroVECTOR.py. The program will open in the file tab.
One can create a new file or open an existing one. Once a file is open, a copy can be created with the Save As button.
In case of using the Python SITL module, it is recommended to save each file in a different folder since the modules can only be loaded from the SITL Modules folder located in the directory of the .txt save file, as in the examples. The SITL Modules and SITL Modules/Complementary Modules folders are created automatically when creating a new file and, in case of using the Save as command, the contents of the original modules are also copied to the new location.
One must fill the required parameters of the rocket. New motors can be added in the motors folder.
Please do not leave blank entries
THE SAVE BUTTON SAVES ONLY THE CURRENT TAB, BE SURE TO CLICK IT ON ALL OF THEM
To draw the rocket, one must insert the point as coordinate from the nose cone tip, diameter in that point. With the Add Point button, one adds the point written in the entry. The Delete Point button deletes the point currently selected in the combo box. To modify a point, one has to select the desired point in the combo box, click the Select Point button, write the new coordinates in the entry, and at last, click the Modify Point button.
To draw the fins, one must insert the position and chord of the root and tip, separated by comma. The wingspan is measured from the root to the tip.
All dimensions are in meters.
The order is the following:
Only trapezoidal fins are modelled.
After the points are written in the entries, one can either update the stabilization or control fin. Clicking the Load "" Fins button will fill the entries with the current data of the fin. The button Reset Fin sets the fin entries to a zero-area fin.
WARNING: THE USE OF CONTROL FINS DISABLES THE TVC STABILIZATION.
Examples of detached fins: Sprint - BPS.space, and our own Roll Control System Testbed
The space between the body and the fin must be considerable, if one is unsure about a fin being attached or detached, the most conservative option is the right option.
The Angle of Attack slider allows to change the AoA at which the CP (red point) is calculated. The blue point represents the CG of the rocket. One can enable and disable the fins to quickly redraw the rocket and ensure that the CG is in the correct position.
The Set Rocket Body tab has four sliders to simulate the forces on the rocket and test changes in the configuration before simulating. For example, if you see in the simulation that your rocket looses control at 10º angle of attack, with an actuator deflection of 20º, at 3 seconds from liftoff, you can put those parameters in the sliders in the Set Rocket Body tab and make changes to make sure you have the net moment that you need (i.e. increase the control fin size to get a restaurative moment).
One can activate the 3D Graphics by clicking the checkbox. IT REQUIRES VPYTHON
In case of using the Python SITL module, refer to the example. One can create functions, classes, modules, etc., or modify the code at will. The objective was to make it as similar as possible to an Arduino, but there are some differences, especially with the global variables having the prefix self. Only the Python SITL module is compatible with GNSS and sample times.
It was only tested on an Arduino Nano clone, so compatibility is not ensured.
Even on the Arduino, the program did not work properly with program runtimes times smaller than 5 milliseconds.
To use the Software in the Loop function, one must set the Port to the one in which the board is connected, and the Baudrate to the one set in the Arduino program.
One can simulate sensor noise by filling the entries with the Noise Standard Deviation of the specified sensor.
Download and include the library and create the instance with the name you want.
At the end of void setup, start the simulation.
Replace your sensor readings with Sim.getSimData() and the name of your variables.
Positive values are positive in the direction of the axes!
(Refer to the Technical Documentation)
Replace your servo.write() for:
Replace servo_command for your servo variable (in º).
The parachute variable is an int, it's normally 0 and one must make it 1 when the parachute would deploy.
REMEMBER THAT THE DATA IS IN DEGREES, G'S AND M, AND YOU HAVE TO SEND THE SERVO COMMAND IN DEGREES AND THE PARACHUTE DEPLOYMENT SIGNAL AS 0 OR 1.
IF ONE IS USING SOFTWARE IN THE LOOP, THE CONTROLLER SETTINGS DO NOTHING
There are ten plots in total, one can choose between a variety of variables to be plotted in two different figures. The Export Plots button creates a .csv file containing all the plotted variables. The name of the .csv is the save file's name with a subscript and is created in the Exports folder. The exports are useful for feeding simulated sensor data from the Python SITL modules to a real flight computer and debug the latter by comparing the outputs. In consequence, there will be faster code prototyping and more complex controllers with less failures.
If the 3D Graphics were enabled, once the simulation finishes a new tab in your default web browser should open.
NOTE: If the animation is paused, some of the features might require you to seek forward/backward to update the frame.
In src/aerodynamics/rocket_functions.py are some experimental features turned off by default, you can enable them by searching "experimental =" and setting them to True. They include dynamic pressure scaling for, theoretically, better damping, and drag calculations based on the component or fin Reynolds instead of the rocket's Re.