Velocity calculation device, velocity calculation method and navigation device

Abstract

A velocity calculation device includes a vertical direction acceleration detection unit that is mounted on a mobile object to detect the acceleration of a vertical direction generated corresponding to the unevenness of a surface on which the mobile object moves; a horizontal direction angular velocity detection unit that is mounted on the mobile object to detect the angular velocity around a horizontal axis perpendicular to a direction of travel of the mobile object generated corresponding to the unevenness of the surface on which the mobile object moves; and a velocity calculation unit for calculating the velocity in the direction of travel of the mobile object based on the acceleration of the vertical direction and the angular velocity around the horizontal axis.

1 . A velocity calculation device comprising:
 a vertical direction acceleration detection unit that is mounted on a mobile object to detect the acceleration of a vertical direction generated depending on the unevenness of a surface on which the mobile object moves;   a horizontal direction angular velocity detection unit that is mounted on the mobile object to detect the angular velocity around a horizontal axis perpendicular to a direction of travel of the mobile object generated depending on the unevenness of the surface on which the mobile object moves; and   a velocity calculation unit for calculating the velocity in the direction of travel of the mobile object based on the acceleration of the vertical direction and the angular velocity around the horizontal axis.   
     
     
         2 . The velocity calculation device according to  claim 1 ,
 wherein the vertical direction acceleration detection unit continuously and sequentially detects the acceleration of the vertical direction by a prescribed sampling frequency;   wherein the horizontal direction angular velocity detection unit continuously and sequentially detects the angular velocity around the horizontal axis by the sampling frequency; and   wherein the velocity calculation unit sequentially calculates the velocity of the mobile object using the acceleration of the vertical direction in the prescribed sampling number and the angular velocity around the horizontal axis of the sampling number.   
     
     
         3 . The velocity calculation device according to  claim 2 ,
 wherein the velocity calculation unit changes the sampling number so as to increase the sampling number when the velocity is equal to or larger than the prescribed velocity and decrease the sampling number when the velocity is less than the prescribed velocity.   
     
     
         4 . The velocity calculation device according to  claim 3 ,
 wherein the velocity calculation unit has a hysteresis property by changing the sampling number when the velocity increases and when the velocity decreases.   
     
     
         5 . The velocity calculation device according to  claim 4 ,
 wherein the velocity calculation unit calculates the velocity by extracting a maximum value and a minimum value from the acceleration of the vertical direction of the sampling number as a maximum acceleration and a minimum acceleration, respectively, and extracting a maximum value and a minimum value from the angular velocity around the horizontal axis of the sampling number as a maximum angular velocity and a minimum angular velocity, and then dividing a difference of the maximum acceleration and the minimum acceleration by a difference of the maximum angular velocity and the minimum angular velocity.   
     
     
         6 . The velocity calculation device according to  claim 1 ,
 wherein the velocity calculation unit further includes a low-pass filter in which a low-pass cut-off frequency lower than a prescribed frequency generated by a cradle when the velocity calculation device is held in the cradle is set up to remove frequency components which are equal to or more than the low-pass cut-off frequency from the acceleration of the vertical direction and the angular velocity around the horizontal axis.   
     
     
         7 . The velocity calculation device according to  claim 6 ,
 wherein the velocity calculation unit further includes   a high-pass filter in which a high-pass cut-off frequency lower than the frequency equivalent to the unevenness of the surface on which the mobile object moves is set up to remove frequency components which are equal to or less than the high-pass cut-off frequency from the acceleration of the vertical direction and the angular velocity around the horizontal axis, and   a cut-off frequency setting unit that sets up the low-pass cut-off frequency and the high-pass cut-off frequency depending on the previous velocity.   
     
     
         8 . The velocity calculation device according to  claim 7 ,
 wherein the cut-off frequency setting unit sets up the low-pass cut-off frequency and the high-pass cut-off frequency so as to be changed in a plurality of stages, and makes the value of the velocity, which is a threshold value when changing the low-pass cut-off frequency and the high-pass cut-off frequency, different from each other in a case where the velocity increases further than the previous velocity and in a case where the velocity decreases further than the previous velocity.   
     
     
         9 . The velocity calculation device according to claim  7 ,
 wherein the cut-off frequency setting unit sets up the low-pass cut-off frequency and the high-pass cut-off frequency corresponding to a prescribed function depending on the velocity.   
     
     
         10 . The velocity calculation device according to  claim 1 ,
 wherein when the velocity acquires a higher value of more than a prescribed threshold value than the previous velocity and when the previous velocity is less than the prescribed velocity, the velocity calculation unit sets the velocity to 0, and   wherein when the velocity acquires a higher value of more than the prescribed threshold value than the previous velocity and when the previous velocity is equal to or larger than the prescribed velocity, the velocity calculation unit sets the previous velocity to the velocity.   
     
     
         11 . A method of calculating a velocity comprising the steps of:
 detecting the acceleration of a vertical direction generated in a mobile object corresponding to the unevenness of a surface on which the mobile object moves;   detecting the angular velocity around a horizontal axis perpendicular to a direction of travel of the mobile object generated in the mobile object corresponding to the unevenness of the surface on which the mobile object moves; and   calculating the velocity in the direction of travel of the mobile object based on the acceleration of the vertical direction and the angular velocity around the horizontal axis.   
     
     
         12 . A navigation device including:
 a vertical direction acceleration detection unit that detects the acceleration of a vertical direction generated in a mobile object corresponding to the unevenness of a surface on which the mobile object moves;   a horizontal direction angular velocity detection unit that detects the angular velocity around a horizontal axis perpendicular to a direction of travel of the mobile object generated in the mobile object corresponding to the unevenness of the surface on which the mobile object moves;   a velocity calculation unit that calculates the velocity in the direction of travel of the mobile object based on the acceleration of the vertical direction and the angular velocity around the horizontal axis;   a vertical direction angular velocity detection unit that calculates the angular velocity around a vertical axis perpendicular to the direction of travel;   an angle calculation unit that calculates the angle through which the mobile object has rotated based on the angular velocity around the vertical axis; and   a position calculation unit that calculates the position of the mobile object based on the velocity in the direction of travel calculated by the velocity calculation unit and the angle calculated by the angle calculation unit.