* updated
10.06.15 - Simulation: Problems with variables
There were unknown variables for a few weeks in the simulation. Namely the drag coefficient, the lift coefficient and the inertia of the quadcopter body. No real solution has been found as of yet.
One the other hand, the simulation is pretty much finished. The movement of the quadcopter works as intended (if the unknown variables would be known). There is still uncertainty about the output though. It is important to know, if the output of the acceleration has to be in the direction of the body frame of the quadcopter or the direction of the inertial frame (in the direction the copter is nudged or the xyz-direction of the room the copter is in).
A missing feature is some form of object distance measurement (putting the copter into a virtual room and outputting the distances to the walls). This will hopefully be acomplished within the next week.
As for the missing variables, here is some information gathered which might help:
Inertia:
"What do you think of reducing the quadcopter to a spheric point mass with 4 point masses located distance l from the centre. So basically Ixx=(2m(r^2)/5)+2m(l^2),Iyy=(2m(r^2)/5)+2m(l^2) and Izz=(2m(r^2)/5)+4m(l^2). I was suggested a paper written by Randal Beard. This is how he calculates its. I cant actually do it experimentally because I need to simulate it before building."
-> http://www.engr.colostate.edu/~dga/mech324/Labs/Lab%2010/images/moment%20of%20inertia%20table.jpg
-> http://de.wikipedia.org/wiki/Tr%C3%A4gheitsmoment
Lift Coefficient & Drag Coefficient:
C= (L/Al)/(0,5*p*V²)
mit L = Lift Force
Al = cross sectional area of the airfoil
p = Air density
V = wind speed
D = (D/Ad)/(0,5*p*V²)
mit D = Drag Force
Ad = effective area of the airfoil in the drag direction
Source: http://mragheb.com/NPRE%20475%20Wind%20Power%20Systems/Aeorodynamics%20of%20Rotor%20Blades.pdf
Another nice read: http://www.technik-consulting.eu/Analyse/Quadrocopter.html
Yet these two formulas might not even help since both papers I'm currently working with say that the constants in their simulations are only dependent on the lift coefficient and the drag coefficient.
03.06.15 - Update: The Ultrasonic Problem
Measuring distances with an ultrasonic sensor poses an unexpected challenge - dealing with the speed of sonic.
02.06.15 - Update: First Movements
28.05.15 - Meeting
Start: | 16:00 | Attendees: | ||||
End: | 17:00 | apo | fma | lan | lpe | |
Protocol: | fma |
21.05.15 - Meeting
Start: | 16:00 | Attendees: | ||||
End: | 17:00 | apo | fma | lan | lpe | |
Protocol: | apo |
13.05.15 - Update*
For providing the ability of using the real sensors and actuators as well as the simulation to test the quadcopter, we decided to use some interface, which can both, communicate with the hardware or with the simulation.
Update (16.05.15):
A basic Arduino Sketch with description is published under the Software section, outlining all current challenges of the projects code.
12.05.15 - Update
Since the components are shipped with an unknown arrival date and for testing the interaction of the different sensors and actuators we will build an Arduino Lego Mindstorms setup on three wheels.
The NXT will therefor provide some basic navigation functions like goForwards, goBackwards, rotateRight, etc., as the software for basic flight is going to do later, too, and control the motors accordingly. The Arduino will be connected to the rest of existing components as usual.
An NXT block is generally able to communicate over I2C as master to any slave device, for instance the Arduino. Via simple looped polling the NXT can ask the Arduino for drive commands.
To connect the Lego block to the Arduino a Mindstorms NXT cable is ordered, which will be cut open and linked to the microcontroller. For further understanding about wiring and I2C the LEGO MINDSTORMS NXT Hardware Developer Kit.pdf gives a good start. In addition the webpages of leJOS News and Dexter Industries seem to be quite helpful and even give some basic code example. Further information following...
11.05.15 - Update*
Ultrasonic sensors and bluetooth bridge have been delivered. Communication with Arduino is working.
Code:
The bluetooth module is found on the MacBook Pro as HC-06 in the list of available bluetooth devices. A connection can be established with Code '1234'.
Unfortunately the MacBook does not reconnect automatically after reset of the Arduino. The bluetooth module has to be unpaired and paired again to be usable again. Hopefully this will can be fixed somehow...
Update:
A much easier way of connecting via bluetooth is to use the Arduino Serial Monitor (Tools -> Serial Monitor).
It is now clear, how the module is handled by the MacBook Pro. Once paired, the HC-06 is always shown in the list of bluetooth devices as 'Not connected', unless an explicit connection is established. Establish a connection with a screen or the Serial Monitor. Once the connection is closed, HC-06 will be shown as 'Not connected' again. It is important to notice that the previous screen method has to be killed explicitly, not only closed, since there can only be one serial connection at once.
08.05.15 - Proposal Presentation
07.05.15 - Meeting
Start: | 16:00 | Attendees: | ||||
End: | 18:00 | apo | fma | lan | lpe | |
Protocol: | lan |
30.04.15 - Meeting
Start: | 16:00 | Attendees: | ||||
End: | 16:40 | apo | fma | lan | lpe | |
Protocol: | lpe |
26.04.15 - Meeting
Start: | 17:30 | Attendees: | ||||
End: | 21:00 | apo | fma | lan | lpe | |
Protocol: | fma |
23.04.15 - Meeting
Start: | 17:30 | Attendees: | ||||
End: | 18:30 | apo | fma | lan | lpe | |
Protocol: | lpe |
23.04.15 - Meeting
Start: | 16:00 | Attendees: | ||||
End: | 17:30 | apo | fma | lan | lpe | |
Protocol: | lpe |