Patent ID: 8442685
Filing Date: 2013-05-14
Classification: B25J

Abstract:
1. A robot control apparatus that controls a robot comprising a joint shaft and a drive shaft transmitting a drive force to the joint shaft, comprising: an actuator configured to drive the joint shaft in each control cycle; a drive shaft angle detecting unit configured to detect an angle of the drive shaft; a joint shaft angle calculating unit configured to calculate an angle of the joint shaft from the angle of the drive shaft; a tip-end position calculating unit configured to calculate a position of a tip end of the robot from the angle of the joint shaft; a position error calculating unit configured to calculate a position error between the tip-end position and a position command value of the tip-end position; a Jacobian matrix calculating unit configured to calculate a Jacobian matrix between a task coordinate system and a joint coordinate system at the tip-end position, based on the angle of the joint shaft; a joint angle difference calculating unit configured to calculate a joint angle difference; a torque command value calculating unit configured to calculate a torque command value of a joint, based on the joint angle difference; a drive unit configured to drive the actuator, based on the torque command value; a drive torque estimating unit configured to estimate a drive torque for driving the actuator from the angle of the joint shaft; an external torque calculating unit configured to calculate an external torque that is a difference between the drive torque estimated and the torque command value; an external force calculating unit configured to calculate an external force acting on the tip-end position, from the external torque and the Jacobian matrix; a compliance model memory unit configured to store a compliance model at the tip-end position; a compliance correction amount calculating unit configured to calculate a compliance correction amount for a task coordinate system position at the tip-end position in accordance with the external force, using the compliance model, the compliance correction amount calculating unit correcting the position error with the use of the compliance correction amount; a friction parameter memory unit configured to store friction parameters including at least one parameter of a model approximating a friction torque; and a friction torque evaluating unit, the drive torque estimating unit including: a drive shaft speed calculating unit configured to calculate a speed of the drive shaft from the angle of the drive shaft; an inertia torque calculating unit configured to calculate an inertia torque acting on the joint shaft; a gravity torque calculating unit configured to calculate a gravity force acting on the joint shaft; a first friction torque calculating unit configured to estimate a first friction torque, using the calculated speed of the drive shaft and the friction parameters stored in the friction parameter memory unit; and a second friction torque calculating unit configured to calculate a plurality of second friction torques by varying the friction parameters, the friction torque evaluating unit calculating a sum of a calculated first friction torque, a second friction torque selected from the plurality of second friction torques, the calculated inertia torque, and the calculated gravity torque, the friction torque evaluating unit calculating a torque error between the sum and the torque command value calculated by the torque command value calculating unit, the torque error being calculated for each of the second friction torques, the friction torque evaluating unit selecting a friction parameter based on the torque error, and the friction parameters being updated based on a result of the selection.