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Alpha production Currently this product is only available as part if our alpha release and not yet finalized. Information here will be changed at any time without notice.

System overview

The local positioning system is based on the DecaWave DWM1000 module. The system consists of a number of anchors that's continuously pinged from the Crazyflie 2.0 deck that's based on the same module. The anchors are placed around the room at known positions (for now).

Our testsystem uses the following components:

  • 6 anchors (with power cables) using this 3D printed stand
  • 1 deck
  • Computer running ROS (Indigo) using the Crazyflie ROS module
  • Crazyflie client with ZMQ to mix manual and automatic control

Here's a video of the current state (March 2016).

Hardware description

The hardware consists two parts, nodes and decks.

Firmware

DWM Node

Building and flashing

Building and flashing is described in the repository. It's possible to flash the board both using SWD and DFU.

Flashing via DFU requires dfu-utils (>=0.8) and Python (>=2.7). To enter DFU mode hold down the DFU button (see 6 above) while power on or resetting the board.

To flash the firmware use

make dfu

DWM deck

The firmware for the DWM deck is included in the Crazyflie 2.0 firmware build (recent) and activated when the deck is attached. The deck contains a small memory that holds the address of the board as well as the addresses of the anchors it will use for ranging.

More information on building the firmware and the firmware itself can be found here.

ROS

The ROS module for positioning with the LPS is available on Github: https://github.com/bitcraze/lps-ros. It has been developed and tested on ROS Indigo running on Ubuntu 14.04

To get started from a newly installed ubuntu:

  1. Run catkin_make to build the packages
  2. Source the workspace devel/setup.bash again
  3. Run rosdep install bitcraze_lps_estimator to install dependencies

The position of the anchor has to be entered in a configuration file. The file should be data/anchor_pos.yaml. An example is present in the data folder:

anchor_pos.yaml
n_anchors: 6
anchor0_pos: [  0,   0, 1.85]
anchor1_pos: [  0,   2, 1.85]
anchor2_pos: [  4,   2, 1.85]
anchor3_pos: [  4,   0, 1.85]
anchor4_pos: [1.3,   1, 1.85]
anchor5_pos: [2.6,   1, 1.85]

The positions are in meter, [x, y, z], from the origin.

When this file is configured, the dwm_loc.launch launch configuration will connect the crazyflie with the right log setup, launch the particle filter and the visualization:

$ roslaunch bitcraze_lps_estimator dwm_loc.launch uri:=radio://0/40/2M

Set up

the dwm nodes can be configured in 3 different modes; tag, anchor or sniffer. By default they come pre-configured as anchors. The anchors are powered with 5v either through micro usb, power jack or screw terminal A nice way to power the anchors is to use usb power pack like we do here:

Place the anchors at least 15 cm from the floor/wall/ceiling, and preferably at least 2 meter apart. We use 3d printed anchor-stands that can be found at: https://github.com/bitcraze/bitcraze-mechanics/blob/master/LPS-anchor-stand/anchor-stand.stl

One of the main consideration for the anchor placement is the Dilution Of Precision.

projects/lps/index.1464092538.txt.gz · Last modified: 2016-05-24 14:22 by arnaud