This week’s EYE ON NPI (video) knows where it’s been and where its goin’! We reckon you’ll love the ST Teseo-VIC3DA and Automotive GNSS Dead-Reckoning Module and Evaluation Kit, a technology that improves on GPS/GNSS by adding an IMU and odometer to help determine location in places where GPS signal is unable to reach such as tunnels and canyons.
We’ve covered GPS modules before on EYE ON NPI – they’re many-decades-old technology that uses a satellite constellation to calculate 3D location on Earth with ~10 meter precision. They’re great for use with cars or trucks because GPS works anywhere on the planet, and when combined with digital maps, can easily calculate instructions, arrival time and recommended routes. However, GPS has a few things that it can’t do. Most important is it cannot work at all if there’s no clear view of the sky. One needs to constantly be receiving GPS data from 3+ satellites in order to determine location. So, if you’re in tunnel or in a city-made canyon, or if there’s RF shielding or interference, you simply ‘drop off’ the planet. Super awkward!
For those situations, some companies or technologies can take advantage of “WiFi Assisted GPS” this is where a secondary base station, or WiFi signal names, can be used to help locate during low-visibility. This works particularly well in cities, of course, where there’s a high density of AP names that don’t change.
But it’s still pretty useless in a tunnel or outside a city center. There’s also RTK, which is awesome for increased precision and accuracy – but that requires a base station within a couple-hundred meters, and another transmission link on every device, so while it’s used for some agricultural robotics, it’s not always possible to implement (but it is worth investigating if you can control the environment where you’re using GNSS.)
So, finally we come to dead-reckoning techniques. These work in an intuitive way: if you know where you last were and you count the number of steps and direction which you’re going, then in theory you should be able to determine your exact location. Now, historically, this technique has been used with boats and planes and hiking – in fact you probably learned it in scout camp.
And, while in theory, it should be a perfect way to determine location, the implementation makes a massive difference on how usable the end product is. A slight error in direction angle makes for more and more drift error in the final result – and as humans struggle to calculate direction, it’s better than nothing, but not necessarily trustworthy without having reference checkpoints on a map.
For this module, ST has worked on how to make it as easy as possible to implement dead reckoning into your robot, with all the fixin’s. First up, you’re getting multi-constellation support. So not only American GPS, but also Europe’s Galileo, Russia’s Glonass, Japan’s QZSS, and China’s BeiDou systems. So if you can’t get data from one constellation, you can use another. Next up, there’s an internal 6-DoF sensor that is used as a tilt-compensated compass that will determine direction precisely. (GPS modules do give ‘heading’ but it’s just based on the last few locations). Next, you need to calculate ‘steps’ – that’s done with an odometer input. That pin is connected to a simple rotation-count sensor and direction sensor which will let the chip know how many ticks have passed since the last known fix. You can also send the odometer data over NMEA commands, btw. Finally, the module can combine this in the TESEO firmware to give you a fast (30 Hz) updated location! Usually this calculation stuff is the hardest part of doing dead reckoning, so it’s really cool to see this all in one.
For folks who want to get going immediately, ST makes a very snazzy EVB-VIC3DA dev kit in an aluminum box and everything, with ports and power supplies and LEDs so you can immediately toss it into your robot without any soldering or board layout required.
The ST Dead-Reckoning GNSS modules TESEO-VIC3D, and EVB-VIC3DA eval boards are in stock right now, for immediate shipment, from Digi-Key! Order today and I reckon’ you’ll be adding this great locating hardware to your design tomorrow afternoon.
See on Digi-Key at https://www.digikey.com/short/pwtjwh95