FANBEAM. Fanbeam System. Fanbeam is an auto tracking laser system for one or a number of targets. Used with DP, only one target is tracked at a time.

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1 FANBEAM System is an auto tracking laser system for one or a number of targets. Used with DP, only one target is tracked at a time. The system is made up of 4 parts: Scanning head Control unit Display Power supply The scanning head is placed on the top of the mast to achieve full 360 viewing. The laser has two lenses, one for transmitting and one for receiving, the righthand lens when facing forward being the transmitter. The lenses must be kept clean. When the laser is parked, the lenses will face astern. Display unit Control unit Scanner unit The laser can be tilted vertically so that the centre axis will point towards the target. A telescope is mounted on top of the laser for this use. The laser is classified as a Class 1 laser, the same as the laser used in a CD player. Jan Kongsberg Maritime AS Page 6.6.1

2 Targets The targets must be equipped with reflectors, preferably retro prisms that return incoming light inside ±30 of the centre of the prism. Reflective tape, Diamond Grade White Reflective Tape is recommended, can be used at short range only because the quality of the return signals is poor. The longer the distance, the more prisms must be used, stacked on top of each other. For distances up to 1 km three prisms should be used. For distances over 1 km six prisms should be used. To make a target visible from all angles the prisms should be formed as a circle consisting of 8 prisms and the circles stacked on top of each other. Range Measurements The laser measures range with great accuracy. Theoretical maximum range = m PRF = 200µS between each pulse Speed of light 300 m/µs The light has to travel back and forth, i.e. 150 m/µs 200µS * 150 m = m Theoretical minimum range = 3,75 m Pulse length 25 ns Speed of light 0,300 m/ns The light has to travel back and forth, i.e. 0,150 m/ns 25 ns * 0,150 m = 3,75 m The laser beam: 20 vertical fan shape (± 10 ) from the centre axis of the lens. The fan shape is made by the lens. Due to loss, this fan will be reduced to approx. 6 (± 3 ) at 2 km. 2 cm horizontal beam. Laser is parallel light beams. Bearing Measurements The scanner contains a motor which rotates the laser in the horizontal axis and an encoder which measures the bearing. To find the bearing the system has to find the target centre. This is achieved through the laser scanning the target in a specified sector. Based on the reflected light the target s horizontal centre of gravity is calculated. The system will automatically adjust the centre of the sector to the target s centre of gravity. The sector has to be large enough for the system to be able to follow the target if the vessel suddenly changes heading, and the effects of pitch and roll. The laser s horizontal bearings are measured with an optic encoder with a resolution of 0,01. This makes the accuracy better than 0,02. At a distance of 1 km the inaccuracy will be 35 cm. Page Kongsberg Maritime AS Jan. 2010

3 The system gives bearing and range to target relative to the vessel. To find the vessel s position the DP system must know the vessel s heading. The accuracy of the measurements of an ordinary gyro is approx. 0,5. At a distance of 1 km the inaccuracy will be 8,8 m, and thus making the gyro the limiting factor for the system. In addition, the scanning head s position in relation to the vessel s centre of gravity must be corrected for pitch and roll by VRS signals. Operation The operation is simple: 1. Search for targets 2. Select a target 3. Park the laser after use The display page consists of 3 main areas: To the left a graphic display area. To the right an alpha numeric display area. Along the base of the screen, the command line is displayed. Use the arrows to go between the different commands, and select command by pressing the ENT button. On older versions with a plasma display, the command line refers to buttons just underneath the display, or function keys (F keys) on a keyboard when using a PC. Jan Kongsberg Maritime AS Page 6.6.3

4 Main Menu The main menu consists of 4 commands: Setup - not in use Track - used when searching and selecting target Park - used when the laser returns to parked position Commands - not in use If you suspect that you have changed something that should not have been changed, switch the system off and on, the values will then be reset. Searching and Selecting a Target On searching and selecting a target use the TRACK menu: ZOOM IN - decreases the effective area of the graphic display. ZOOM OUT - increases the effective area of the graphic display. SPEED + - increases the rotation speed of the laser. Not in use. SPEED - reduces the rotation speed of the laser. Not in use. GATING - sub-functions enable you to remove unwanted targets in case there are too many in the area (more than 8). STOP - causes the sequence to stop, and the laser to return to parked position. NEXT - carries out STOP and returns to the main menu. Page Kongsberg Maritime AS Jan. 2010

5 Searching for Targets Select TRACK. The laser goes to its zero position, facing straight ahead. The laser stops for a moment. The laser starts rotating 360. As targets are being discovered, they are shown in the graphic display area as vectors with numeric entries. When the laser arrives at its zero position, it stops for a moment before starting the next sweep. NB! The system can handle only 8 targets at the same time. Possible Problems An excessive number of targets, more than 8, are shown in the graphic display area: This happens because the system receives reflections from plane surfaces, such as windows, painted steel sheets, etc. Such reflections give a poor accuracy level. Select GATING Use LEVEL+ to increase the minimum level for the shown target Select NEXT to return to the previous command menu If more than 8 reflectors, all giving a good signal, can be found in the area, set a window with maximum and minimum ranges so that you keep the target you are interested in and lose some of the others. Select GATING Key in minimum range and select MINIRANGE Key in maximum range and select MAXRANGE Select NEXT to return to previous command menu No targets shown in the graphic display area: Control GATING settings and, if necessary, correct these. GATING information is shown in the alpha numeric area of the display. Switching the system off and on can reset the GATING levels. It is impossible to see the vectors, therefore the targets cannot be identified: Select ZOOM OUT to see a larger area of the graphic display. All vectors are too short for the targets to be identified: Select ZOOM IN to see a smaller area of the graphic display. Selecting a Target Select the number representing the target you want to follow. If you lose the target, try RE- ACQ first before you start searching again. Jan Kongsberg Maritime AS Page 6.6.5

6 Data shown on the Display The alpha numeric area shows 3 groups of data: Data for the selected target Target list when searching Target, gating and status information Data for the selected target: RANGE - range to the target BEARING - bearing to the target LEVEL - strength of the reflected signal; the higher the value, the better the strength ACCURACY - accuracy measuring value from 1 to 8; the higher the value, the better the accuracy Target list when searching: Target information number of target range in meter bearing relative to the vessel s bow strength of signal accuracy measuring value Target, gating and status information: number of targets found when searching gate size accuracy measuring value strength of signal scanner s speed of rotation rangegate min - max system status Searching Tracking Page Kongsberg Maritime AS Jan. 2010

7 Maintenance Control and wash scanning head regularly. Wash with a mild detergent. Clean lenses using a proprietary lens cloth. The connectors to be greased with silicon grease. Every 6. month the shaft seal has to be lubricated. Apply a grease gun to the nipple under the laser until grease is just seen appearing from the upper lip. Use lithium based multipurpose grease. If greasing is neglected, the shaft seal has to be replaced. The result might also be ingress of water with resulting problems. Jan Kongsberg Maritime AS Page 6.6.7