Robot controller, robot system, robot control method

Abstract

A robot controller includes a force control unit that outputs a correction value of a target track of a robot based on a detected sensor value acquired from a force sensor, a target value output unit that obtains a target value by performing correction processing on the target track based on the correction value and outputs the obtained target value, and a robot control unit that performs feedback control of the robot based on the target value. Further, the force control unit performs first force control when an external force direction indicated by the detected sensor value is a first direction, and performs second force control different from the first force control when the external force direction is a second direction opposite to the first direction.

What is claimed is: 
     
         1 . A robot comprising:
 a robot main body; and   a robot controller configured to control movement of the robot main body and including:
 a force controller configured to perform a first force control when an external force direction indicated by a detected sensor value is a first direction, and to perform a second force control different from the first force control when the external force direction is a second direction substantially opposite to the first direction; and 
 an operations controller configured to control operations of the robot main body based on the first or second force control performed by the force controller. 
   
     
     
         2 . The robot according to  claim 1  wherein:
 the force controller is configured to perform the first force control by which an amount of displacement change with respect to external force is a first amount of displacement change when the external force direction is the first direction, and 
 the force controller is configured to perform the second force control by which the amount of displacement change with respect to external force is a second amount of displacement change different from the first amount of displacement change when the external force direction is the second direction. 
 
     
     
         3 . The robot according to  claim 2  wherein:
 the force controller is configured to perform the first force control of outputting a first correction value corresponding to the first amount of displacement change when the external force direction is the first direction, and 
 the force controller is configured to perform the second force control of outputting a second correction value corresponding to the second amount of displacement change when the external force direction is the second direction. 
 
     
     
         4 . The robot according to  claim 1  wherein the force controller includes an external force direction determination part configured to determine the external force direction indicated by the detected sensor value. 
     
     
         5 . The robot according to  claim 1  wherein:
 the force controller includes a control parameter memory that stores plural sets of control parameters for force control and a control parameter selector that selects the set of control parameters to be used from the sets of control parameters stored in the control parameter memory, and 
 the force controller causes a first set of control parameters to be selected when the external force direction indicated by the detected sensor value is the first direction, a second set of control parameters to be selected when the external force direction is the second direction, and obtains a solution of a differential equation in force control as a correction value using the selected set of control parameters and outputs the correction value. 
 
     
     
         6 . The robot according to  claim 5  wherein the force controller changes the set of control parameters to be used from the first set of control parameters to the second set of control parameters when a predetermined control parameter change command has been issued when performing force control using the first set of control parameters. 
     
     
         7 . The robot according to  claim 5  wherein:
 the force controller changes the set of control parameters to be used to the first set of control parameters when a magnitude of external force in the first direction has exceeded a first threshold value when performing force control using the second set of control parameters, and 
 the force controller changes the set of control parameters to be used to the second set of control parameters when a magnitude of external force in the second direction has exceeded a second threshold value when performing force control using the first set of control parameters. 
 
     
     
         8 . The robot according to  claim 1  wherein the force controller weighs a first correction value obtained by the first force control and a second correction value obtained by the second force control to obtain a third correction value and outputs the third correction value when the external force direction indicated by the detected sensor value is the second direction. 
     
     
         9 . The robot according to  claim 1  wherein the force controller has a digital filter that obtains a solution of a differential equation in force control as a correction value. 
     
     
         10 . The robot according to  claim 9  wherein the force controller determines stability of an operation of the digital filter of obtaining the correction value, and obtains the solution of the differential equation in force control as the correction value when the operation of the digital filter is stable. 
     
     
         11 . The robot according to  claim 9  wherein the differential equation is an equation of motion having a virtual mass term, a virtual viscosity term, and a virtual elasticity term as coefficient parameters. 
     
     
         12 . The robot according to  claim 1  further comprising:
 a target value output unit configured to obtain a target value by performing correction processing on a target track based on a correction value and outputs the target value, wherein 
 the robot controller moves respective parts of the robot main body based on the target value acquired from the target value output unit.