Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Marine vehicle
Reexamination Certificate
2001-01-24
2003-04-15
Nguyen, Tan (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Marine vehicle
C701S014000, C114S163000, C340S987000
Reexamination Certificate
active
06549831
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to indicator systems for marine vehicles particularly with respect to a low cost rudder angle indicator system including a large, three-faced display.
2. Description of the Prior Art
In one type of prior art rudder angle indicator system, a conventional synchro transmitter is coupled to the rudder to provide a synchro signal output in accordance with rudder angle. A conventional synchro receiver, coupled to a rudder angle indicator, positions the indicator to an angle in accordance with the synchro signal thereby displaying rudder angle. Plural synchro receivers may be required if multiple indicator units are utilized. Typical synchro transmitter and receiver devices tend to be expensive adversely affecting the cost competitiveness of a rudder angle indication system in which they are utilized.
It is often desirable and a requirement in certain types of installations to utilize a large conventional three-faced rudder angle indicator display as the primary rudder angle indicator, which display is typically mounted overhead in the bridge area. The large indicator is mounted toward the front and center of the bridge and by utilizing the three scales located at different angles around the indicator, the large dial can be read from numerous positions in the bridge area including straight on and from the port and starboard wings.
When the large three-faced indicator structure it utilized, the rudder angle sensor and indicator positioning mechanism is conventionally synchro based. In such systems, a number of smaller displays may be mounted in various locations about the ship and may also be included on the bridge wings. In such a synchro based system, a synchro receiver corresponding to the synchro transmitter rudder angle sensor is used to drive each of the indicator units including the three-faced display. Because of the significant cost of the synchro devices, such a synchro based system tends to be undesirably expensive as discussed above.
Another approach to rudder angle indication utilizes a potentiometer sensor coupled to the rudder to provide a voltage proportional to rudder angle. The rudder angle indicating voltage is applied to a plurality of d'arsonval meter movement indicators with appropriate rudder angle indication scales. Such an analog system tends to be inaccurate and unreliable and requires amplifiers in accordance with the number of such indicators utilized on the ship. Significantly, the d'arsonval meter movement approach is inappropriate for positioning the large three-faced rudder angle indicator without undesirable design complexity and expense. Thus, it is appreciated that this analog approach is primarily limited to providing variously positioned small meter movement indicators about the ship for displaying rudder angle.
U.S. Pat. No. 5,107,424 issued Apr. 21, 1992 and assigned to the assignee of the present invention, although not describing a rudder angle indication system, discloses, inter alia, a compass repeater dial positioned open loop by a stepper motor in response to a signal from a synchro coupled to the ship's compass. An index tab attached to a pulley driving the repeater dial provides an electrical index for positioning the repeater dial to zero. Although the system of said U.S. Pat. No. 5,107,424 is eminently suited to the purposes for which the system was designed, the use of an expensive synchro sensor would be undesirable in a system where the objective is low cost.
Additionally, at power-up of the system, a full 360° spin search of the repeater dial is typically required to locate the index tab for initial dial synchronization. A considerable amount of time is required for the full 360° repeater dial spin hunt for the index tab where the repeater dial is slewed potentially through 360° while detecting when the index tab traverses the index tab sensor. The time required for the search is further exacerbated by index tab overshoot and reverse direction hunting for the tab alignment edge.
It is an objective of the present invention to provide a low cost rudder angle indicator system suitable for driving the large three-faced rudder angle display.
It is a further objective of the invention to minimize the requirements of the full 360° spin search for the index tab during power-up of the system.
SUMMARY OF THE INVENTION
The objectives of the present invention are achieved by a system for providing an indication of rudder angle utilizing a position sensor, such as a low cost potentiometer, coupled to the rudder for providing a rudder angle signal. A display indicator, such as the three-faced rudder angle indicator, provides the rudder angle indication which is provided in an active display sector corresponding to the rudder angle range. Drive means, such as a stepper motor, drives the indicator open loop in response to the rudder angle signal so that the indicator provides the rudder angle indication. Initializing means including, for example, an index tab and sensor are utilized in activating the drive means to drive the indicator to an initial position such as 0°. If the indicator is already in the active sector, a first initializing procedure is utilized that avoids the disadvantages of a full spin search. If the indicator is not in the active sector, a second initializing procedure, such as the full spin search, is utilized. Means, which include, for example, a sector tab and sensor, are included for detecting the active sector of the display to provide an active sector signal in accordance with whether the indicator is or is not positioned in the active sector. The active sector signal is utilized to determine which of the first and second initializing procedures to select.
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Lett Gerald L.
Levine Seymour
Nguyen Tan
Northrop Grumman Corporation
Tran Dalena
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