The Crazyflie 2.0 (as most other quadcopters and robots) has no real notion of its position in space. The on board sensors (accelerometers and gyros) can be used to give a rough idea of its movements but lacks the accuracy for long term position awareness. The solution is to use an external system that can provide information of the current position. Outside GPS can be used, but indoor the options are limited, often complex, expensive or both. That is why we have created the Loco Positioning system.
The Loco Positioning system is a local positioning system that is used to find the absolute 3D position of objects in space. It is in many ways similar to a miniature GPS system. The base of the system is a set of Anchors that are positioned in the room (compare to the satellites in GPS), they are the reference. The other part of the system is one or more Tags (compare to the GPS receiver) that are fixed to the object(s) that are to be tracked. By sending short high frequency radio messages between the Anchors and Tags, the system measures the distance from each Anchor to the Tags and calculates the position of the Tags from that information. By adding knowledge of its position to a Crazyflie 2.0 it is capable of flying autonomously without manual control. This opens up an array of exciting use cases and applications.
The Loco Positioning Deck
The Loco Positioning Deck is a Crazyflie 2.0 expansion deck with the Loco Positioning Tag functionality. Read more on the Loco Positioning Deck page.
The Loco Positioning Node
The Loco Positioning Node is a multi functional node in a Loco Positioning system, it can act either as an Anchor or Tag. As an Anchor it is part of the reference base for the system while running in Tag mode it can be attached to an object to track, for instance a robot. Read more on the Loco Positioning Node page.
The Loco Positioning system is based on the Decawave DWM1000 chip and has an accuracy in the 10 cm range.
A theoretical minimum of 4 Anchors are required to calculate the 3D position of a Tag, but a more realistic number is 6 to add redundancy.
The Loco Positioning system has mainly been designed for indoor use.
Getting started with Loco positioning
The video below is showing the process from receiving the Loco Positioning system up to having an autonomous flying Crazyflie. More information is also available on the wiki.
Used by Lund University
At the Centre for Mathematical Sciences at Lund University PhD student Kenneth Bastone and professor Kalle Åström are currently using the Crazyflie and the Bitcraze ultra-wide band based Loco Positioning system as part of their research. We visited them and wrote a blog post about their work.
To read the blog post go here.
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