Work machine safety device

Abstract

A safety device is capable of stably performing safety control for a work machine. The safety device comprises a position information acquisition part and a control part. The position information acquisition part periodically acquires position information on a position of a detection object around the work machine. The control part performs the safety control corresponding to current information when the current information is varied from previous information in a direction of approaching the work machine, executes a control change inhibition of inhibiting the safety control from being changed in response to the variation in the position information when a change inhibition condition including that the current information is varied from the previous information in a direction of separating from the work machine is satisfied, and releases the control change inhibition when a predetermined time has elapsed after the start of the control change inhibition.

1 . A safety device for performing a safety control of a work machine, comprising:
 a position information acquisition part that periodically acquires position information on a position of a detection object around the work machine; and   a control part, wherein   the control part is configured to perform the safety control when current information, which is the position information currently acquired, is varied from previous information, which is the position information previously acquired, in a direction of approaching the work machine, the safety control corresponding to the current information, configured to execute a control change inhibition of inhibiting the safety control from being changed in response to a variation in the position information when a change inhibition condition including that the current information is varied from the previous information in a direction of separating from the work machine is satisfied, and configured to release the control change inhibition at a point in time when a predetermined time has elapsed after the control change inhibition is started.   
     
     
         2 . The safety device of the work machine according to  claim 1 , wherein the control part releases the control change inhibition at a point in time when the position information has been acquired a predetermined number of times after the start of the control change inhibition. 
     
     
         3 . The safety device of the work machine according to  claim 1 , wherein the safety control includes a speed limitation control, which is a control of limiting a speed of a limitation target motion that is preset among motions of the work machine at a degree increased with a decrease in an object distance, which is a distance from a reference position that is set for the work machine to the detection object, when the object distance is within a preset speed limitation range, and the control change inhibition includes inhibiting a limitation of the speed of the limitation target motion from being relaxed in response to the variation from the previous information to the current information. 
     
     
         4 . The safety device of the work machine according to  claim 3 , wherein: the work machine includes a hydraulic circuit for performing the limitation target motion; the hydraulic circuit is configured to limit the limitation target motion in accordance with a limitation command that is input to the hydraulic circuit; and the control part is configured to generate the limitation command and to input the limitation command to the hydraulic circuit when performing the speed limitation control and configured to inhibit, as the control change inhibition, the limitation command from being changed. 
     
     
         5 . The safety device of the work machine according to  claim 4 , wherein: the work machine includes a lower traveling body and an upper turning body mounted on the lower traveling body capably of turning; the hydraulic circuit includes a circuit for turning the upper turning body; the position information acquired by the position information acquisition part includes information about the object distance, which is a distance from a reference position set for the upper turning body to the detection object; the limitation target motion includes at least a turning motion of the upper turning body; and the limitation command includes a turning limitation command for limiting the turning motion. 
     
     
         6 . The safety device of the work machine according to  claim 1 , further comprising an alarm unit, wherein the safety control includes a control of making the alarm unit output an alarm. 
     
     
         7 . The safety device of the work machine according to  claim 1 , wherein the control change inhibition is to continue the safety control based on the previous information regardless of the current information. 
     
     
         8 . The safety device of the work machine according to  claim 3 , wherein the control change inhibition is to limit the speed of the limitation target motion based on position information obtained by reducing the variation from the previous information to the current information. 
     
     
         9 . The safety device of the work machine according to  claim 3 , wherein the control change inhibition is to directly reduce the relaxation itself of the limitation of the speed of the limitation target motion in response to the variation from the previous information to the current information. 
     
     
         10 . The safety device of the work machine according to  claim 1 , wherein the change inhibition condition further includes that a difference between the current information and the previous information exceeds a preset allowable difference. 
     
     
         11 . The safety device of the work machine according to  claim 1 , wherein the change inhibition condition further includes that the position information about the detection object related to the current information has already been acquired more than or equal to a preset number of times. 
     
     
         12 . The safety device of the work machine according to  claim 1 , wherein the position information acquisition part includes an imaging device that generates a captured image containing the detection object and a position information generation unit that processes the captured image to thereby generate the position information. 
     
     
         13 . The safety device of the work machine according to  claim 1 , wherein the control part is configured to execute the safety control when the detection object is detected in a monitoring area set around the work machine and configured to maintain the safety control that has been performed in an in-area detection state where the detection object is detected in the monitoring area, as the control change inhibition, when the detection object is shifted from the in-area detection state to an in-area non-detection state where the detection object is not detected in the monitoring area. 
     
     
         14 . The work machine safety device according to  claim 13 , wherein: the monitoring area includes a stop area and a speed limitation area; the control part is configured to execute a forcible stop control as the safety control when the detection object is detected in the stop area, the forcible stop control being a control of forcibly stopping a limitation target motion preset among motions of the work machine, and configured to execute a speed limitation control as the safety control when the detection object is detected in the speed limitation area, the speed limitation control being a control of limiting the speed of the limitation target motion at a degree increased with a decrease in an object distance, which is a distance from a reference position set for the work machine to the detection object; and the control change inhibition includes inhibiting the limitation of the speed of the limitation target motion from being relaxed in response to the variation from the previous information to the current information. 
     
     
         15 . The safety device of the work machine according to  claim 14 , wherein the change inhibition condition further includes that a difference between the object distance according to the current information and the object distance according to the previous information exceeds a preset allowable difference.