Communications: electrical – Selective – Having indication or alarm
Patent
1984-02-06
1987-03-03
Rowland, James L.
Communications: electrical
Selective
Having indication or alarm
73 65, 114122, 364463, G08B 2300, B63B 3900
Patent
active
046479287
ABSTRACT:
A stability indicator for a marine vessel. The indicator continuously determines a GM value for the vessel equal to the square of the vessel's beam length times the square of the vessel's rolling constant divided by the square of the vessel's rolling period. The rolling period is determined by means of a gravity sensor whose output is an electrical signal corresponding to the instantaneous magnitude and direction of the roll angle. Electronic level adjustment and gain selection means are also provided, to compensate for the fact that the stability indicator may often be installed with the gravity sensor off-horizontal. The signal from the gravity sensor is input into a data processor that computes the rolling period by first analyzing the roll angle signal to establish a zero level and threshold levels above and below the zero level. The rolling period is then determined to be the time required for the roll angle to change from the positive threshold, to a value less than the negative threshold, and back to the positive threshold again. Successive rolling periods are averaged by means of a recursive filter, and the average rolling period is used to determine GM. In another embodiment of the present invention, the stability indicator includes means for calculating two average rolling periods. The first average rolling period is determined by averaging a fixed number of successive rolling periods, and the second average rolling period is determined by averaging a selectable number of successive rolling periods. First and second GM values are calculated based on the first and second average rolling periods respectively. Means are also included for providing a warning when the first GM value is less than an alarm level, and for displaying the second GM value.
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Casey Thomas A.
Keough William B.
Rice Miles L.
Rothenbuhler Dan E.
Trimble Bruce E.
Marine Partners
Rowland James L.
Swarthout Brent A.
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