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This thread is privately moderated by mike_kelly, who may elect to delete unwanted replies.
Mar 19, 2019, 05:30 PM
Wisconsin
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UC4H: Rangefinder inproves low altitude measurements


The continued epsiodes of the Son of FrankenSolo build. Using Olliw's UC4H and a 3DR Solo surplus motherboard to create and advanced DIY quad.

I have gotten the UC4H powerbrick, UC4H ESC's, UC4H Display Notifier and UC4H GPS/MAG/Baro installed. Kinda the required basics to get flying.

Now for some frosting on the cake. I have wanted to experiment with a downward facing sonar since the APM days but the sensors available have always been marginal or quite expensive. The old HC-SR04 did not do much. The Maxbotix had noise isssues to deal with and the true LIDARS were in the hundreds of dollars.

For low altitude measurements Pixhawk depends on it's barometer. But the Barometer senses air pressure and that changes with the weather. So adding a better sensor for low altitude height measurements could improve landing and AltHold flight mode.



The new kid on the low altitude sensor block is the Benewake TFTmini LIDAR. It is not a true LIDAR (Light Detection and Ranging) because it does not use a laser. It instead uses a less costly LED light. But it seems to work well and is moderately priced at around $50.

OlliW took advantage of this new sensor and added it to UC4H. The UC4H Rangefinder. It could use the UART Tunnel technology but it is easy to setup and use as a UAVCAN device or the generic mode.



First install the UC4H Rangerfinder firmware on your General Purpose node.
using the UAVCAN GUI tool. Choose a unique node ID and leave the Channel ID=-1, to use the UAVCAN mode for the node. RangeRate> 0 sets the node in the generic mode.

Mount the TFTmini so it has a clear view of the ground.

In Mission Planner goto the advanced Parameter list and the category RNDFND.

RNGFND1_TYPE=83 sets the rangefinder to UAVCAN/UC4H

You must set the RNGFND1_MAX_CM= to a reasonable and low height so that the limit of the Rangefinders accuracy is not exceeded, like 700cm which is about 20ft. Above that the Pixhawk will switch back over to using the barometer.

You can check to see if your Rangefinder is working by taking a look at the status tab (under the HUD in Mission Planner) the parameter Sonarrange will change as you move the quad up and down.



Now time for a nice soft landing!

Addendum: OlliW's new video on the rangefinder reminds me that the TFMini takes considerable power so it should not be powered of the flight controller CANbus. I power my CANbus with the powerbrick not the Flight controller.
https://www.youtube.com/watch?time_c...&v=My_RvtFhX-s
Last edited by mike_kelly; Mar 30, 2019 at 09:44 PM.
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