Patent ID: 8289013
Filing Date: 2012-10-16
Classification: G01P

Abstract:
1. A speed detection device for periodically sampling coordinates showing a position of a moving body which carries out a rotating motion or a reciprocating motion and detecting a speed of the moving body based on the coordinates comprising: a memory configured to store a plurality of preset tentative angles and values of a trigonometric function corresponding to the plurality of tentative angles; a first register configured to store first coordinates of the moving body obtained by a first sampling; a second register configured to store actual second coordinates of the moving body obtained by a second sampling subsequent to the first sampling; and an arithmetic operation unit configured to calculate second coordinates in calculation by multiplication, addition, or subtraction of the first coordinates and the values of the trigonometric function to approximate the second coordinates in calculation to the actual second coordinates, the arithmetic operation unit further configured to calculate the speed of the moving body based on a tentative angle corresponding to the value of the trigonometric function used to calculate the second coordinates in calculation; a discrimination unit configured to discriminate a region to which the first coordinates, the actual second coordinates, and the second coordinates in calculation belong; a comparator configured to select an expression to be operated by the arithmetic operation unit; wherein the expression is selected based on the region to which the first coordinates, the actual second coordinates, and the second coordinates in calculation belong; a third register configured to sequentially store the second coordinates in calculation; a fourth register configured to cumulate tentative angles; wherein the memory is further configured to store φ the arithmetic operation unit is further configured to cumulate Expression 1 or Expression 2, as to the respective values of i in the order of i=0, 1, 2, . . . . (where, φ i =tan −1 2 −i (i=0,1,2 . . . n), and when i=0, xc i−1 =x 1 , yc i−1 =y 1 ) where the first coordinates are shown by (x 1 , y 1 ), the actual second coordinates are shown by (x 2 , y 2 ), and the second coordinates in calculation are shown by (xc i , yc i ); the comparator is further configured to compare the actual second coordinates (x the third register is further configured to store the second coordinates in calculation operated by the arithmetic operation unit as to the respective values of i; the fourth register is further configured to accumulate the tentative angles used by the second coordinates in calculation as to the respective value of i; the arithmetic operation unit is further configured to calculate the speed of the moving body based on the accumulated tentative angle stored in the fourth register, when the second coordinates in calculation are nearest the actual second coordinates.