Jump to content
Sign in to follow this  
elossam

rc radar

Recommended Posts

Hi again folks. Want to start playing with a ultrasonic radar to add an anticolision system for my quad. Have found this and several similar others http://www.maxbotix.com/products/MB1000.htm but seems to me it is not directly rc compatible like i.e. a gyroscope working inline with the servo. Does anyone know if there are already done adapter boards. Maybe a pwm to ppm adaptar like the ones used time ago on the first quads should be right?

Share this post


Link to post
Share on other sites

This is "just" a distance measurement device. I.e. it will give the distance to the nearest object in front of it in various forms. You will need a controller/processor that you'll program to use that info to decide whatever to do with it.

Share this post


Link to post
Share on other sites

Hi kilrah. One of the forms it shows the distance is a PW output according whith the datasheet in the same web. I'm far away of a technic man to understand it but if it is a PWM and it gives different values on it a converter can give me a variable rc signal to be mixed with the main channel. ┬┐no? I dont need to know hiw far or close an obstacle is but a signal increase when it's aproaching and a signal reduction when opposite that goes down to zero when nothing is detected in the range of the sensor.

Share this post


Link to post
Share on other sites

I dont see any rc compatable pulses as said already, the only pulse output would need to be fed into another processor like a pic to be of any use.

The idea that the raw output can be turned into an rc pulse and used is hoping for too much I think. I expect some scaling and expo would be needed at very least.

Terry

Share this post


Link to post
Share on other sites

Just curious, but are there any examples out there of a Quad flown outdoors that is successfully using ultrasonic sensors for altitude hold or collision avoidance? The reason I ask is because acoustic sensing does not seem to be an optimal choice for a helicopter. For example, noise from the blades/props or soft earthly surfaces (grass, bushes) will affect the performance. Yes, I know the robot hobbyists have grand success, but their application is a piece of cake compared to what a Quad might need.

Or maybe I should ask how one would expect to use it? Not so much the technical use, but the practical matters such as how many sensors do you expect to install and how would they be positioned on the quad? And in the case of the OP's anti-collision application, what flying situations are you trying to apply it to, what is the shape/size of the object you want to avoid (anti-collision), and what is the needed sensing distances?

It's all in the little details to determine if the ultrasonic solution is a practical choice. Not saying it won't work, but with things like this, what you want and what you get may not be the same. :)

Share this post


Link to post
Share on other sites

At first a single unit pointed forwards to fly close to a building but safe enough not to crash with it. As soon as the building comes into the radar range the elevator channel must push the unit back until the building is out of range again.

Share this post


Link to post
Share on other sites

I think you would need to be able to disable it too for take off and landing. For sure plenty of room for experimentation :)

Terry

Share this post


Link to post
Share on other sites
At first a single unit pointed forwards to fly close to a building but safe enough not to crash with it. As soon as the building comes into the radar range the elevator channel must push the unit back until the building is out of range again.

That seems like a simple implementation. Simple is good! :)

I think you would need to be able to disable it too for take off and landing. For sure plenty of room for experimentation

How about this: Use a stick, knob, or toggle switch (and its mix menu) on the Tx to control the anti-collision distance's threshold. It could also turn off the anti-collision feature.

If I had any free time I'd take a stab at this. Especially since my WiiCopter is an open source design and firmware changes are possible. But at this point I'm buried in stuff, so I can only cheer you on.

Share this post


Link to post
Share on other sites

The radar cone is not flat so take of with it enabled must be virtualy imposible. Mixing the signal with the elevator channel using a minimix or similar is what I`m thinking to do and a knob from the tx to reduce the gain or the mixing ammount. The goal is to have a virtual spring between the ufo and what it has infront so and obstacle can be close up to a certain distance but no more. Have a Hoverfly Sport board and it` s possible to directly fit this sensor to use it for altitude control. Must check if it works outdoors so I`ll start ordering one but could be fine if someone finds a way to get a rc signal converted from what the sonar can provide but whithout using a full PC to procces it.

Edited by elossam

Share this post


Link to post
Share on other sites

Regarding the sensor choice, I would suggest you use the XL series (MB1220 XL EZ2 looks good) rather than the LV. The XL's have higher output and continuous autocalibration for acoustic noise, which is something that should help ensure better performance in a model helicopter application.

Share this post


Link to post
Share on other sites

I purchased the Maxbotix MB1220 XL EZ2 and did some basic evaluation of it. The MB1220 seemed like a good candidate because it has high acoustic power and real-time noise filtering.

I wired it with a 3-wire cable, Power, Gnd, and Analog out. For my tests I used an o-scope during the indoor evaluation and a DMM was used during the outdoor experiments.

Tests of it measuring the distance from a large outdoor wall showed that it will be affected by the ground if it is not at a high enough altitude or has any pitch towards an earthy direction. But for the helicopter anti-collision application, this should not be a problem if the collision detection distance is short and the model is several meters above ground.

I was interested in how it would behave with a quad's vibration and prop noise. So I mounted it on my quad (pointing down) with some vibration damper grommets. The mounting is shown in the photos below.

Top View:

post-2-0-27856200-1316747989_thumb.jpg

Bottom View:

post-2-0-18138000-1316747999_thumb.jpg

I found that with large sudden throttle changes the data would jump for a moment, but other than that it worked fine over all normal throttle ranges. So the real-time noise filter feature does a good job.

It was also useable when I measured the height above my recently cut lawn; I did it from about 8 feet high (best I could do with a stretched arm) and the data wandered only a small amount. So the high acoustic power seems to be helpful.

Hopefully this information helps out with your anti-collision project. Be sure to periodically report updates as the project moves along.

Share this post


Link to post
Share on other sites

Oh your keen!

I can see an alt hold/auto land project comming soon ;)

Terry

Share this post


Link to post
Share on other sites
I can see an alt hold/auto land project comming soon

Sounds cool, but it's not on my list at the moment. I would indeed like a working altitude hold for my WiiCopter. But the limited range of the ultrasonic sensor method is just not my cup of tea. So in my spare time I'm slugging away at traditional barometric sensor methods and hoping for a miracle from the WiiCopter gurus.

The only reason I checked out the sensor is because the ultrasonic method frequently pops up in R/C forum discussions. Despite the interest in them, I have yet to see anyone publish any real DiY success with them. So I wanted to know if the latest affordable technology would work on a R/C heli flown in a varied outdoor environment. From my quick evaluation I believe the MaxBotix sensor should be fine if the requirements are practical. So someone out there needs to stop talking about them and just do it. I'm here to cheer them on. :)

Share this post


Link to post
Share on other sites

Have a look at this http://code.google.com/p/arducopter/wiki/AC2_Sonar

I and many others are using sonar on the Arducopter and it works very well over short distances. If you fly a copter up steps then it keeps a constant height from the steps.

The AC has a Planner that allows waypoints to be flown and other actions can be programmed as well. It also has an immediate mode so that the flight plan can be varied as you fly and all open source. Auto lift of, return to home, auto land are all available and the software base is good for conventional helis, 'copters and fixed wing which are catered for by variants of the software.

Peter

Share this post


Link to post
Share on other sites

Thanks for the link. It's great to see a quadcopter project that is using a Maxbotix ultrasonic sensor.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×