wangning198914 wrote:What do you think using swarm flying robot? they can work together, and I am thinking there are 4 flying robot be a group, 1 is a scanning and communication drone, and 3 of them are signal transmission drones.they are using visual light communication system to contact with surface. When they are out of range, the 1 of signal transmission drone land on the floor become a signal box that make the others flying further. I also think about using "Bluetooth low energy". Each of caver can wear a smart Bluetooth device. And when the flying robot near them, it can detect the victims and connect with them. it can through 3-5 km. What do you think?
Hi Ning. Welcome to the forum.
I think you have some promising ideas here. Bluetooth should be effective for very short range wireless communication in cave passages, and the use of light (preferably infrared so it doesn't distract the human rescuers) between robots is an interesting concept but could be affected by interference from a multitude of caver headlamps which use Pulse Width Modulated LED drivers. Also the average cave will require a lot more than just 4 robot repeaters if you intend to relay signals over any significant distance.
Of the 3 choices in your initial post (search, treatment and transporting patients), my gut feeling is that the search process would most benefit from some type of automated robotic assistance. This seems to be your conclusion too. I think a compact, rugged, hybrid flying/crawling robot would be the most ideal solution but also the most complex and expensive. As for the most time-consuming part of an average cave rescue, I would say that would be patient transport unless the patient is minimally injured and able to move on their own. But with the various techniques we use I just don't think robotic assistance to treat or transport patients would be as effective as robots to help with the search process.
For robots to be really useful in a cave rescue application, they should be able report back to humans on the surface in real-time (or short delay) even if they are programmed to operate autonomously. As Dan indicated, communication during a cave rescue is as challenging as it is critical. The default cave rescue communication method in North America is a modified army-type field phone system using wire, and its strength is in its relative simplicity and dependability. However trailing a long wire behind a robot all the way through a cave is not so practical (unless you design a robot to do exactly that and replace a human!), so really wireless communication (radio frequency or your visual light concept) is the obvious solution for this.
The old cave CB radio design with attached transverter (I think this is what Dan meant) converts 27MHz to 185kHz (VLF), and has been proven to work well in some caves through hundreds of meters of solid rock but is not always a perfectly reliable system. The transverter process is not very efficient, and the surface end is usually very susceptible to atmospheric and electrical interference. Going higher in frequency, the lower end HF band is less affected by atmospherics and allows for slightly more compact equipment, but is more fickle transmitting through different types of rock and different ground resistivity. Simple tone signals (like Morse) have more likelihood of being received through deep rock than voice communication, but even with good voice communication it would be a huge leap to the bandwidth required to support a data stream carrying video signals etc in VLF or even HF systems. Also this mode of communication requires larger equipment, batteries and antennas which would be difficult to make work on a practical cave-sized drone or robotic device.
As an alternative to lower frequency RF, there are more compact and cost effective UHF systems. The good news is that while these signals generally do not penetrate rock to any practical extent, there has been some recent success experimenting with a series of UHF nodes positioned along cave passages where each 'hop' is line-of-sight. How about trialing a larger group of small robots (flying or crawling) autonomously deployed and able to be re-positioned throughout the cave to provide a series of nodes for passing voice, data and/or video either by light pulses or UHF? It would be rather equipment-intensive, but you could send a series of basic robots to spread out along main passages to act as mobile communication repeater nodes, while a few flying/crawling robots autonomously investigate for missing/injured persons and return back to the nodes to report. In a deep cave system you could even incorporate a wire carrying data from the surface to the search area, where an interface patches the signal through the wireless nodes/robots. And with a little extra instrumentation and miniature cameras and lighting, you could create a virtual map and video of the cave as you go!
Let us know when you have prototypes ready to test, and we'd be happy to help you get them dirty.
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