Calibrating a virtual force sensor of a robot manipulator
AssigneeFranka Emika GmbH
InventorAndreas Spenninger
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Abstract
The invention relates to a method for calibrating a virtual force sensor of a robot manipulator, wherein the following steps are carried out in a plurality of poses: applying an external wrench to the robot manipulator, ascertaining an estimate of the external wrench, ascertaining a first calibration matrix based on the ascertained estimate and a specified external wrench, ascertaining a second calibration matrix by inverting the first calibration matrix, and storing the respective second calibration matrix in a data set of all of the second calibration matrices, thereby assigning each second calibration matrix to the respective pose for which each second calibration matrix was ascertained.
Claims20
A method of calibrating a virtual force sensor of a robot manipulator, wherein the virtual force sensor is used to determine an external wrench acting on the robot manipulator based on torques determined by torque sensors in joints of the robot manipulator, wherein the robot manipulator (1) is moved or guided manually in a plurality of poses, and in each of the poses the method comprises:
- applying a respective specified external wrench to the robot manipulator;
- ascertaining an estimate of the external wrench based on an inverse or a pseudo-inverse of a transpose of the Jacobian matrix applicable to a current pose and based on an external torque vector, wherein the external torque vector is ascertained based on the torques determined by the torque sensors in the joints of the robot manipulator and based on expected torques acting on the robot manipulator;
- ascertaining a respective first calibration matrix based on the ascertained respective estimate of the external wrench and based on the respective specified external wrench;
- ascertaining a respective second calibration matrix by inverting the first calibration matrix, the second calibration matrix being used to adjust an external wrench currently determined during subsequent operation;
- and
- storing the respective second calibration matrix in a data set of all second calibration matrices by assigning the respective second calibration matrix to a respective pose for which the respective second calibration matrix was ascertained.
A robot system comprising:
- a robot manipulator comprising joints;
- torque sensors disposed in the joints of the robot manipulator;
- a control unit designed to implement a virtual force sensor on the robot manipulator, the virtual force sensor being used to determine an external wrench acting on the robot manipulator based on torques determined by the torque sensors, wherein the robot manipulator is moved or guided manually in a plurality of poses, and in each of the poses the control unit is configured to:
- apply a respective specified external wrench to the robot manipulator;
- ascertain an estimate of the external wrench based on an inverse or a pseudo-inverse of a transpose of the Jacobian matrix applicable to a current pose and based on an external torque vector, wherein the external torque vector is ascertained based on the torques determined by the torque sensors in the joints of the robot manipulator and based on expected torques acting on the robot manipulator,
- ascertain a respective first calibration matrix based on the ascertained estimate of the external wrench and based on the respective specified external wrench;
- ascertain a respective second calibration matrix by inverting the first calibration matrix, the second calibration matrix being used to adjust an external wrench currently determined during subsequent operation;
- and
- store the respective second calibration matrix in a data set of all second calibration matrices by assigning the respective second calibration matrix to a respective pose for which the respective second calibration matrix was ascertained.
Dependencies are inferred from the claim text.