I am building a dynamic full vehicle thrust stand and need to be able to set the throttles to specific levels for calibration purposes. Is there a way using the mission planner and a joystick as my control device to make the engines run at specific throttle settings like 10, 20, 30, 40, ... 100% to get my data points? If anyone else has ever built a full system thrust stand like this i would like to hear about how it worked out for them.
thanks
dennis
Replies
Hi Dennis,
A cheap servo tester should be able to accomplish this but a microprocessor controlled test would be way cooler...
Sounds like you need to look into Arduino... I have performed motor/prop testing on a stand controlled using a Arduino Nano ($8.66 from here: http://goo.gl/xrhz4T) . Everything else you need to setup and program your own testing controller is free from here: http://www.arduino.cc/ I set up mine to sweep through the throttle range and output over a serial stream pulse width (throttle), voltage, current, rpm, and thrust. Voltage was measured via divider, current via a hall effect sensor, thrust via a load cell. RPM was a bit of a trick but I did manage to come up with a simple circuit that produced a 5v square wave across one phase proportional to RPM - due to the way the ESC drives the motor, this signal can be quite noisy....
in your testing did you do single motor/prop or full up installed system testing. what i want to do is a full craft, installed test where i can resolve the thrust of each engine at a given thrust setting. i am a retired flight test engineer and have experience with both installed and uninstalled engine testing and i just wanted to try this with our quad. i am currently at a hold on this project because i got all wrapped up in the dragster data logging effort. my current thrust "stand" involves hanging the quad upside down from my garage ceiling with four scales on the corners and collecting data that way. i was about to test that when they added a feature to disarm the beast when it goes upside down for over some small number of seconds - there doesn't seem to be a way to override that. i will have to flip the apm upside down to do my tests and that sort of irritates me since any "feature" like auto-disarm should be able to be overridden by the pilot/user if they want to. i will get over that attitude when i get back to working on the thrust stand and just flip the apm over.....
I tested with a single motor/prop. My quad is a big of a large beast that is a bit scary close up... Max thrust of a single motor with 16x8 prop is just a tad over 3.4Kg. I just replied to your new blog regarding your dragster data logging where I posted a link to some 3.2 firmware that I modified to disable the crash detection that is hampering your efforts here. It is a fairly simple change to the code - I will link to the file below as well.
I just found another resource that may help you get on the path to modifying the code yourself:
http://firmware.diydrones.com/Tools/Arduino/How%20to%20Build%20Ardu...
I enjoy something a bit different like this (both projects!) so feel free to share your ideas and I'll help out where I can.
Modified 3.2 Firmware: http://gdurl.com/OeEL/download (please do not fly!)
since i got not replies to my question let me ask it a different way.....
how hard would it be to build a firmware load for the apm which would run instead of the UAS firmware (ardupilot, arducopter, ardurover, etc,) that a user could use to do "maintenance" type things. one example of a "maintenance" kind of thing would be to runa selected engine(s) at specific power setings. i would like to do this, and perhaps other things, without the "help" of the autopilot - pure installed hardware/electrical tests... what i would like are tools like an autoshop has to run diagnostic tests on a car which take onboard computers out of the loop to remove that variable. perhaps there is already such a tool and i just don't know about it. any input would be appreciated.
thanks
dennis