Wide angle laser beams can detect and measure the range to people, trees and other safety critical objects from moving aerial or ground based platforms.
We've been experimenting with a new version of our SF10 laser altimeter to see what happens when we change the normally narrow, parallel laser beam into a wider, fan shape and align it horizontally or with a downwards tilt. There is a practical limit to the wide direction (major axis) of about 30 degrees but any angle from zero to thirty degrees is attainable. The best combination of range and sensitivity is found using a 10 x 3 degree beam pattern that can detect a person more than 10m away.
The two pictures above show the SF10 laser unit and an example of the modified laser beam pattern. The intensity, and therefore the detection sensitivity, is pretty uniform across the beam so even obstacles right at the edges give a good return signal. We're using time-of-flight technology to work out the distance and the unit has I2C, serial and analog interfaces.
The real purpose of this blog post is to ask the knowledgeable members of this forum for feedback about possible applications for wide laser beams, used either stand alone or in multiples. I admit that this is not going to be the ideal solution to every problem. Instead, I hope to use your feedback as a sanity check to see if we're going in the right direction with this technology.
Thanks, LD
Comments
I would buy it! I'm of the understanding that the higher data rates are useful to reduce the angle swept where no detections are made for a given RPM?
I think that I'd like to have the ability of streaming 10k readings per second, but that's got to be tempered by the ability to measure the beam source origin and angle so that the position of the reading in 3D space can be accurately calculated.
I think it's relatively easy to reject close duplicates so that any visualisations or processes using all stored points can be done with the smallest data set possible - further simplified by rules which allow the use of simpler geometry.
Obviously the accuracy of the base data is the foundations on which a good system is built.
Thanks @Phill and @Eli for the comments. It always astonishes me when people ask for hardware that they can't actually use, but perhaps this is a case of driving the technology in the right direction and letting the supporting architecture take care of itself.
I think we could produce a good quality 2D laser scanner that retails for less than $1k. What I don't understand yet, is why would anyone buy it?
I don't believe that you could do that sort of processing on any current flight controller. It would have to be offloaded to a single board computer, and the only one I can think of would be the Jetson because of its CUDA capability. At least that's my plan...
Thanks for the comment Eli. Any ideas how you would process more complex data on the fly? We have tested out a 2D rotary unit that can measure out beyond 100m at >10,000 readings per second. That's a lot of data for a small flight controller to digest.
Taking this biological analogy one step further, autonomous systems such as drones could be designed more on a Maslow architecture, where the final mission is actually the least "necessary" component of the design and instead represents the final stage of actualization. This way more emphasis is made of basic survival characteristics such as not flying or running into things.
We could create capability or activity diagrams that show which features are truly critical to survival, and work up the pyramid to those that have commercial or entertainment value. For example, this approach would turn the whole "conflict" with the FAA on its head because the first requirement for survival would be "Don't hurt people". Failure to deal with this fundamental problem could lead to extinction on many levels!
No kidding. I work in a manufacturing facility, and do a lot of work around the house (auto-repair, etc.) and ever since I lost my hair, you can't believe how often I bang my head on something compared to what I used to. :D
I have been using sonars for just this purpose, having high refresh rates with low processing power.
The problem with trying to scan using a narrow beam sensor is that the overall refresh rate will be way too small for reactive (or reflex) avoidance.
I have played around with the LIDAR from XV-11 Neato robotics (very similar to the RPLidar dev kit) and even with a sensor that can take 2000 readings a second you end up with <8Hz 360° refresh rate and this is only a planar scan.
If these wide angle sensors can run at 16-32Hz @ 10m max range without interfering with each other and with fewer problems outdoors than non time of flight systems, these would make a great upgrade for the ultrasonics I am currently using.
Hi Jake. Perhaps you're right, but consider that a static laser sensor is smaller, lower weight, more reliable (no moving parts), responds much faster than a scanning laser and has an easier data interface.
A laser is simply a source of light, just like an LED or incandescent lamp. The reasons for using a laser to measure distance relate more to its high speed than to the collimation properties of its beam.
The idea behind using static sensors for reflex response and scanning lasers for mapping comes from biological systems that offer good models for autonomous processes. All multi-cellular creatures use more than one sensing technology because it is the most efficient way of handling the data. For example, we humans regularly use our eyes for mapping but rely on touch (often just the hairs on our skin) for reflex "collision avoidance".
I found the article from Photonics about wire detection that I mention in my previous post. Here's the LINK.
It seems that I did not correctly remember the details of its operation. The wire detection system transmits an AM modulated waveform and measures phase shift to find the range.
Hi Ken, an interesting application.
For the additional range and a particularly uncooperative target, the best laser beam pattern might be a bit narrower - say <5 degrees. The trick would be to align the beam with the camera so that the operator knows exactly where the laser is (or to use a small red or green aiming laser) and then "grab" readings as the drone moves around in proximity to the cables, latching the last known good result.
I can't speak for all ultrasonic devices, but at one time we manufactured ultrasonic range finders and we would never have recommended them for measuring to a narrow cable that's 15m away. The return signal would be too small, especially with all the wind and noise around a drone.
-
1
-
2
of 2 Next