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RTK stands for ‘actual time kinematic [positioning]’, and it is a system that works to make GPS knowledge extra correct. So satellite tv for pc knowledge alone would possibly assist find your robot lawn mower right to inside a number of meters, however mix it with RTK positioning, and it may slim that down to a couple centimeters.
This is the know-how that has enabled fashionable lawnbots to navigate and not using a boundary wire. It additionally means the lawnbot can mow in an ordered, logical style, slightly than simply traversing the lawn randomly.
Nonetheless, the effectiveness of RTK positioning is reliant on particular components – and if sure issues are off, it may not work very properly in any respect. Learn on for extra on how RTK positioning works in robot lawn mowers.
Why is satellite tv for pc knowledge not correct sufficient?
We have been utilizing the time period GPS, however that is in truth simply one in every of 4 programs that is likely to be offering the satellite tv for pc knowledge that helps your lawnbot discover its approach round – so a extra right acronym could be GNSS (world navigation satellite tv for pc system).
The satellites use two primary sign varieties. The oldest sort of satellite tv for pc sign is the L1 sign, and this could’t cross by way of any stable object. Newer L2 alerts can penetrate by way of some objects – together with issues like thinner timber, plastic and lightweight tree protection – however each time it does so, the sign will get weaker.
The time it takes for the sign to get from the satellite tv for pc all the way down to earth is what creates the inaccuracies in positioning knowledge. Even passing by way of our ambiance causes delays; the sign passes by way of some areas extra rapidly than others.
How does RTK positioning assist?
RTK primarily helps right inaccuracies in satellite tv for pc positioning knowledge, to make it extra exact. It does this in actual time.
The system depends on a set, antenna-equipped base station with recognized coordinates (this is separate from the robot lawn mower’s charging station, which is the place the bot docks and recharges its battery). Each the RTK base station and lawnbot hook up with satellites within the sky.
To do that they want a direct line of sight to every satellite tv for pc – issues like partitions, roofs and even tree protection can block the sign. What’s extra, each the bottom station and lawnbot each want to connect with the identical satellites as a way to operate.
The RTK station must be positioned so it has the widest unobstructed view of the sky as potential, in as many instructions as potential. It needs to be excessive up, and away from overhanging buildings and timber.
As a result of the lawnbot wants to have the ability to hook up with satellites when it is docked in addition to when it is working, the cost station additionally must be ready with a direct line of sight to the sky (you’ll be able to typically get away with there being a wall behind, offered the opposite three instructions are open and have good line of sight to the sky.)
The RTK base station additionally connects to the lawnbot, however this connection would not require a direct line of sight – it is normally a radio sign, which might cross by way of stable objects.
Are there any down-sides of the RTK system?
The large advantage of utilizing RTK and GPSS knowledge for navigation is that it means you needn’t undergo the effort of including a boundary wire to your backyard.
Nonetheless, it isn’t a failsafe system. The entire thing hinges on there being loads of unfold out satellites that each the robot mower and the RTK station can hook up with. Overhead obstructions like timber and buildings will impression on how efficient it is, and having a great place to place your RTK station is very important.
As a result of they’re so delicate to environmental components, lawnbots that depend on RTK are extra susceptible to getting misplaced, or straying out of bounds, than those who use perimeter wires.
You may additionally discover that the placement knowledge nonetheless is not fairly exact sufficient. An RTK-powered robot mower will will navigate your lawn in neat traces, however as a result of there’s nonetheless a number of centimeters’ margin of error, you would possibly find yourself with unmown strips of grass between rows. You may additionally want to go away a bigger buffer at doubtlessly hazardous perimeters – for instance, the sting of a pond. Lawnbots that use boundary wires will cowl the world in a way more haphazard approach, however they will by no means go over a boundary, and are maybe much less more likely to find yourself lacking a spot.
These potential weak factors imply virtually all fashionable lawnbots will embody one other type of navigation system as backup for when sign is poor. That is likely to be one thing like radar or LiDAR (the tactic utilized in most of at the moment’s finest robot vacuums), or a digicam. There are in fact limitations for every system, however applied sciences are getting ever extra superior, and consequently, so are the lawnbots they energy.