Download Tracker Module

Target Tracker
The Target Tracker system is a prototype bearing tracker that can be used as an input to
automatically orientate a mechanical structure in the direction of the mobile wireless tracking
module.
The tracking is based on range measurements from DECA Wave radios [1]. This first prototype only
tracks bearing from the fixed structure to the moving target for controlling Azimuth. The system
can be expanded to also provide tracking information for Elevation.
Contents
SYSTEM COMPONENTS: ...........................................................................................................................................................2
CONCEPT OF OPERATION .......................................................................................................................................................2
CAN PROTOCOL ..........................................................................................................................................................................2
ANCHOR_UPDATE ..................................................................................................................................................................................... 2
TRACKING INFO ......................................................................................................................................................................................... 2
ANCHOR_RESET ......................................................................................................................................................................................... 3
TRACKER MODULE ....................................................................................................................................................................3
ANCHOR MODULE ......................................................................................................................................................................3
EXAMPLE SOFTWARE ..............................................................................................................................................................4
KNOWN ISSUES ...........................................................................................................................................................................6
BILL OF MATERIALS .................................................................................................................................................................7
NM-260 BOARD ..........................................................................................................................................................................7
POWER ........................................................................................................................................................................................................... 7
CAN1 ................................................................................................................................................................................................................ 7
P410 ................................................................................................................................................................................................................. 7
PROGRAM, ICD, DWM1000........................................................................................................................................................................ 8
USB ................................................................................................................................................................................................................... 8
OPPORTUNITIES FOR IMPROVEMENT........................................................................................................................................................... 8
REFERENCES ................................................................................................................................................................................8
Target Tracking TS-260
iTrack, LLC
System components:
2 Anchor modules
1 Wireless tracking module
1 Wire harness
1 Battery Charger
1 Example interface software
Concept of Operation
The bearing of the tracking target can be determined by the distance to two known points, and the
resulting triangle. The anchors act as the known points. The distance between the anchors must be
configured1.
On power-on the anchor modules are in receive more, ready to respond to range acquisition
requests. The anchors transmit a CAN message with current power level every 1000 ms.
The wireless tracker module requests a range measurement from each of the two anchors, and
transmits the result wirelessly to one of the anchors, along with some diagnostic and health data.
Upon receiving this message, the anchor forwards the data on a CAN message to the host interface.
If one of the anchors stops responding, a value of 255 will appear as the age of its range in the CAN
message. The anchor must be power-cycled to re-activate.
Filtering and data processing is an important aspect of the resulting tracking performance. See the
example Windows Application on page 4 for more information.
CAN Protocol
The CAN protocol consists of 4 Extended messages.
ANCHOR_UPDATE
CAN_ID
DLC Data[0] Data[1] Data[2] Data[3] Data[4] Data[5] Data[6] Data[7]
0x124
3
ID
Vpp
Where ID is the unique ID for the anchor. The current system has anchors 100 (0x64) and 101
(0x65).
TRACKING INFO
CAN_ID
DLC Data[0] Data[1] Data[2] Data[3] Data[4] Data[5] Data[6] Data[7]
0x123
8
Range A
Range B
V bat
Age A
Age B
where Range A and B are in [cm], V bat is the voltage level of the battery in the tracking module, and
Age A and B represent the time in [ms] since the range was acquired.
The distance between the anchors can easily be acquired automatically from the radios, but this has not
been implemented for the current version.
1
-2-
Target Tracking TS-260
iTrack, LLC
Note that the value for Age is limited to 255, which typically means that the range has expired and
that the anchor is not responding.
ANCHOR_RESET
CAN_ID
DLC Data[0] Data[1] Data[2] Data[3] Data[4] Data[5] Data[6] Data[7]
0x0CFFB000
2
0xAA
ID
where ID is the unique ID of the anchor to be reset.
This message was initially implemented in an attempt to re-initialize communication to the
DWM1000 radio, without much success.
Tracker Module
The tracker module contains a 3.7V Li-Ion battery that allows the module to operate for several
hours of tracking time. The system does not contain a sleep mode, so make sure to turn the power
off when the module is not used.
To charge the battery, the module must be opened to reach the charging cable that is tucked inside.
To open the module, unscrew the two screws in the back on the edge of the box that holds the front
lid to the enclosure. When the screws are removed, carefully slide the lid back just a bit, to remove
it from the back side of the enclosure.
Anchor Module
The anchor modules for this prototype system do not contain batteries. The system is connected to
the host to provide power and CAN communication.
The NM-260 board inside the anchor module contains a linear regulator for power regulation, so it
is recommended that the unit is provided with voltage between 4.5 and 8 V.
The 4-wire modular cable provides Power (red), Ground (black), CAN_HI (yellow) and CAN_LO
(green).
-3-
Target Tracking TS-260
iTrack, LLC
When the anchor module receives a message from the Tracking module containing tracking
information, it forwards it through the CAN bus to the host interface. The tracking module provides
more information about the range measurement than is currently forwarded to the host. This can
be expanded for next versions.
Example Software
An example software application is provided to illustrate how the system is used for tracking, and
how to process the data and apply filtering.
On the following page is a snapshot of the software interface. The test window contains a log of the
incoming CAN messages. The columns represent a timestamp, CAN ID, DLC, and the data fields.
-4-
Target Tracking TS-260
iTrack, LLC
To start, select the appropriate baud rage (500 kB) in the drop down list, and click “Start”. When
connected and powered up, the Anchors should report their status with messages once per second.
When the tracking module is switched on, the tracking data messages are reported at a much higher
rate.
The graphics in the User Interface Window represent the tracking system with the Anchors as the
square boxes, and the tracking module as the circle.
The value for Scale can be changed to represent the scale of the graphics. Bigger values zoom in,
while smaller values zoom out.
The value for Base represents the distance between the Anchors, and can be adjusted in the user
interface. The unit is in meters.
-5-
Target Tracking TS-260
iTrack, LLC
The Filtering Coefficient represents a time constant for the second order moving average filter that
is implemented on the individual range measurements. The value can be anywhere from 0 to 1,
with smaller values representing more filtering (and more time delay) and higher values
representing less filtering and more responsiveness. A value for 1 will turn filtering off, and use
unfiltered data for tracking.
The Reset button is implemented to send a reset CAN message to the Anchors. This will trigger a
soft-reset of the firmware within the Anchors.
Known Issues
DWM1000 modules in the anchor may become unresponsive, resulting in failure to acquire range
measurements. CAN message will result value of 255 (0xFF) for age. The only remedy is to powercycle the anchor module.
-6-
Target Tracking TS-260
iTrack, LLC
Bill of Materials
Part
Tracker Enclosure
Anchor Enclosure
Battery 3.7V/800mAh
Charger for Li-Ion
DECAWave radio
iTrack Interface board
Vendor
Digikey
Digikey
All-Battery
Tenergy
Digikey
iTrack
Part number
SRM4PCB-ND
377-2276-ND
14500
01211
DWM1000
NM-260
NM-260 board
Numbering is from Left to Right in the above Figure.
POWER
1. VCC 4.5 ~ 12 V
2. GND
CAN1
1. CAN_H
2. CAN_L
P410 (3.3V UART)
This connector can be used for firmware upgrading using the boot-loader [2]
1. RXD
2. TXD
3. GND
-7-
Target Tracking TS-260
iTrack, LLC
Program, ICD, DWM1000
Follow connector numbering
Functional assignment for ICD and DWM1000:
1.
2.
3.
4.
5.
6.
7.
8.
PGD
PGC
GND
MCLR
N.C.
VDD
N.C.
VDD
CLK
CS
GND
MOSI
3.3V
MISO
3.3V
USB
Default pin assignments.
Wire Harness
Opportunities for Improvement
1. Extend the maximum range. This requires operating the radio in alternative modes and
improve antenna options.
2. Make anchors wireless, and communicate back to the camera through RF (requires
additional radio)
3. Add sleep modes to prolong battery life
4. Add additional anchor to track elevation
References
[1] DECA Wave radio module.
http://www.decawave.com/products/dwm1000-module
[2] PcWin iTrack Interface software.
http://www.itrack-llc.com/KC/index.html
-8-