| > but I'm not aware of any high-resolution ultrasonic sensors for land robots. Sound cameras are very cool- passive sonar, but they're audio frequency and not usually depth-sensing. There's a lot of room for improvement there, but its a relatively unknown area and definitely hasn't found its niche. High resolution air sonar is necessarily fairly large, which makes it decidedly unsexy. It also puts a lot of strain on the potential for a low cost BOM when the pcb and chassis are ~>12" wide. > One minor challenge with ultrasonic sensors in real products is ensuring that they are inaudible to people and pets - when they are almost-audible they are extremely annoying or even painful. One thing that really surprised me when I got into it was that this isnt a trivial problem. Part of it is practical- the cheapest and most common sensors are around 60-80 kHz (mechanical size makes them easy to produce, with the drawback of a high-ish time constant). Getting above the range of domestic animals isn't too hard or inconvenient, but it's surprising how extensively evolution has adapted for sound in bats. If you want to avoid harming them you need to keep above ~150 kHz, which gives you a fairly uncomfortably small bandwidth before you're into the highly-attenuating frequency ranges. Underwater it's a different story (biological structures have difficulty resonating at MHz+) but the frequencies that would give you sub-millimeter precision (350 kHz) are way more inconvenient than 40 or 60 kHz. You need totally different types of piezos and the range is sharply limited unless you're projecting volumes that would deafen at audio ranges. Im still very optimistic about the role of sonar even as cheap lidar and depth cameras crowd the space, but its pretty difficult today to make a truly good sensor. |