Blade control device for work machinery

Abstract

In a blade control device, a blade operation control part outputs a command for raising and lowering a blade such that a position deviation between a blade position calculated by a blade position calculating part and a blade target position approaches zero in a case where a blade load is equal to or less than a second load threshold value, and outputs a command for raising the blade in a case where the blade load is greater than the second load threshold value. In a case where an update condition is satisfied, the update condition being set in advance so as to associate the blade load and a first load threshold value with each other, a target position setting part updates the blade target position using the blade position obtained when the update condition is satisfied as a reference.

1 . A blade control device which is provided in a work machine including a machine body and a blade attached to the machine body so as to be raised and lowered and which controls raising and lowering operation of the blade, the blade control device comprising:
 a target design surface setting part which sets a target design surface that specifies a target shape of an object to be dug by the blade;   a position information acquiring part which acquires position information related to the work machine;   a blade position calculating part which calculates a blade position as a position of the blade on the basis of the position information acquired by the position information acquiring part;   a blade load acquiring part which acquires a blade load as a load applied on the blade;   a storage part which stores a first load threshold value as a threshold value of the blade load and a second load threshold value which is a threshold value of the blade load and is greater than the first load threshold value;   a target position setting part which sets a blade target position that is a position as a target of the blade position and that is a position above the target design surface; and   a blade operation control part which outputs a command for raising and lowering the blade such that a position deviation as a deviation between the blade position calculated by the blade position calculating part and the blade target position approaches zero in a case where the blade load acquired by the blade load acquiring part is equal to or less than the second load threshold value, and outputs a command for raising the blade in a case where the blade load acquired by the blade load acquiring part is greater than the second load threshold value,   wherein   in a case where an update condition is satisfied, the update condition being set in advance so as to associate the blade load and the first load threshold value with each other, the target position setting part updates the blade target position using the blade position obtained when the update condition is satisfied as a reference.   
     
     
         2 . The blade control device according to  claim 1 , wherein
 the update condition includes a condition that the blade load reaches the first load threshold value, or a condition that the blade load reaches a determination value for determining whether the blade load has neared the first load threshold value or not, the determination value being set on the basis of the first load threshold value.   
     
     
         3 . The blade control device according to  claim 1 , wherein
 the storage part is configured to store a first state indicating allowance of update of the blade target position when the blade load becomes greater than a flag threshold value as a threshold value set in advance, and also store a second state indicating non-allowance of update of the blade target position in place of the first state when the blade target position is updated, and   the update condition includes a condition that the blade load reaches the first load threshold value when the first state is stored in the storage part, or a condition that the blade load reaches a determination value when the first state is stored in the storage part, the determination value being set on the basis of the first load threshold value for determining whether the blade load has neared the first load threshold value or not.   
     
     
         4 . The blade control device according to  claim 1 , wherein
 the blade target position to be updated by the target position setting part is set at a position which passes the blade position when the update condition is satisfied and is on a plane parallel to the target design surface.   
     
     
         5 . The blade control device according to  claim 1 , wherein
 the storage part stores a target track as a target for an increase process of the blade load when the blade load approaches the first load threshold value while being increased, and   the blade operation control part outputs a command for raising and lowering the blade such that the blade load approaches the first load threshold value while following an increase process close to the target track before the blade target position is set by the target position setting part.   
     
     
         6 . The blade control device according to  claim 1 , further comprising:
 a load threshold value setting part which sets the first load threshold value,   wherein   the position information acquiring part includes a vehicle body position acquiring part which acquires a vehicle body position as a position of the machine body, and   the load threshold value setting part updates the first load threshold value such that the first load threshold value becomes smaller when a body distance is a second distance than when the body distance is a first distance, the body distance being a distance between the vehicle body position acquired by the vehicle body position acquiring part and the target design surface, the second distance being smaller than the first distance.   
     
     
         7 . The blade control device according to  claim 1 , wherein
 the blade operation control part outputs the command on the basis of a function having a term including, as a variable, a position deviation which is an elevation difference between the blade position and the blade target position and including a position gain by which the position deviation is multiplied, the blade control device further comprising:   a position gain setting part which sets the position gain,   in a case where the blade position is below the blade target position, the position gain setting part updates the position gain such that a raising speed of the blade is increased on the basis of the position deviation.   
     
     
         8 . The blade control device according to  claim 7 , wherein
 the function further has a term including, as a variable, a load deviation which is a deviation obtained by subtracting the second load threshold value from the blade load and including a load gain by which the load deviation is multiplied, the blade control device further comprising:   a load gain setting part which sets the load gain,   in a case where the blade load is greater than the second load threshold value, the load gain setting part updates the load gain such that the raising speed of the blade is increased on the basis of the load deviation.