Under ideal Optical Flow conditions on a typical 450 class quadcopter (lots of incandescent light, varied ground texture, focused PX4flow, tuned PID settings, and altitude of ~1 meter) how much X-Y drift should we expect to see in Loiter Mode?
Interesting. It must've been fixing some other issue with my quad then. To be clear, it was the setting labeled "Loiter PID" in the upper right hand corner of Mission Planner's settings that appeared to "fix" my loiter issues. The settings labeled "Rate Loiter PID" did not resolve my issues.
We're interested in developing a "next generation" optical flow sensor where the camera lens is slaved to a high accuracy laser altimeter in order to provide dynamic focus and increase the useable range. We're looking for someone to flight test our new SF11 laser altimeter with the PX4Flow so that we can collect some real world data before moving forward with the final design. @Fabien, would you be interested in testing the SF11 on your project? We already have some high altitude flight data but we need verification of the short range performance as well :).
We've still got some room on the quad, so that sounds good. Then we can compare it with both sonar and the lite.
I'll contact you via PM to explain our project a bit more.
I'm testing v3.3.2-RC2 using PIXHAWK and PX4FLOW.
I read reply Goro Senzai and all comments. But still have two questions
1) I’m set the EKF_GPS_TYPE parameter equal to 3 and trying take-off in Loiter mode. But copter lost PITCH control via transmitter and autopilot also cann’t control PITCH.
2) On the floor always "Error compass variance". I arm copter in hand and then put on the floor. I set FS_EKF_THRESH 0 (and second test set 1), but nothing changed.
Help me please with my questions. Thanks in advance
Thanks Goro, I'll try again and let you shared on the result ^^;
Hi Paul, I'm not sure why log shows like that and I've tested it indoor like space under big bridge which protected GPS signal perfectly. I'll do test it again. Thanks for your comment ^^
In case someone might find it useful, here's my notes on using the sonar on PX4FLOW as the analog rangefinder.
Since I mostly fly small quads indoors, I thought it would be nice to shed some weight by eliminating bulky and heavy LiDAR unit so I gave it a try, but it turns out my sonar unit was too noisy to be usable so I decided not to go this route, but your milage may vary.
PX4FLOW supplies 5V to the sonar, so the maximum output voltage from pin 3 is going to be roughly 5V (slightly lower in practice). Note that this fluctuates depending on the quality of power source. When powered via USB, it's usually lower than 5v, but when powered via battery and power module, it goes over 5V.
Make sure you connect the analog out of the sonar to Pixhawk's 6.6V ADC input.
If in doubt, consult these pages.
# Analog=1, I2C=4 RNGFND_TYPE=1
# Analog output on EZ4 is linear
# Analog input pin on ADC 6.6V socket is mapped to virtual pin 15.
# If you've connected the sonar to ADC 3.3V socket (using voltage converter), it will either be virtual pin 13 or 14 (ADC 3.3V socket has 2 analog input pins combined).
# EZ4 is linear and ratiometric
# Don't connect stop pin (sonar will always be on)
# The wiki says you should set this to 7m for EZ0 and EZ4, but that's for XL-MaxSonar series. HRLV-Max-Sonar-EZ4 on PX4FLOW only mesures up to 5m.
# EZ4 on PX4FLOW won't return reliable data if the distance is closer than 30cm.
# Adjust the following according to the description given by Paul Riseborough in the previous comment.
# Distance in cm of the PX4FLOW unit from the ground.
# In theory, the voltage range should be between 0.293V and 4.885V (300mm to 5000mm) when Vcc = 5V for the EZ4 sonar on PX4FLOW.
# Acroding to the datasheet, EZ4 will return 4.885mV at 5m when given 5V Vcc.
# 5m / 4.885v
# Finally, if you are using EKF.
# Use range finder instead of baro.
# If you are using EKF2.
# Use range finder instead of baro.
Does anybody have experience with using optical flow at a much higher altitude, such as ~20m? ... My initial guess is that ~20m is probably not doable, but I would like to hear otherwise. :) We have some work that could benefit from it.
Thanks, Paul. That sounds promising.
We intend to fuse the data from PX4Flow and our IR-LOCK system. In the simplest implementation, IR-LOCK would be used to correct the drift.
Also, we were thinking of using IR-LOCK to compute x-y velocities, but I am not 100% confident in that approach.
What exactly do you mean by "accurately focused and calibrated sensor"? Did you use the default 16mm lens?
We are working on a somewhat similar project, but at a higher altitude. Let me know if I can shoot you a PM sometime. :)
Gotcha. Thanks again.