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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-