Patent ID: 7646161

Claim:
A method for controlling a robot arm for use in medical or industrial applications, wherein a robot arm ( 10 ) with a redundant number of joints is used wherein at least a first and a second joint ( 12 a , 12 b ) are controlled and wherein the redundancy of joints is used to optimize a quality criterion, to align two zero moment controlled axes substantially vertical to the instrument axis, an instrument connected to said robot arm is passed through an opening ( 19 ), a torque acting in at least one joint ( 12 ) is detected, the interaction torque acting in said joint ( 12 ) is controlled to substantially zero by means of a control device in order to reduce the forces acting on the edge of the opening, the control of at least a first joint ( 12 a ), which due to its position in space can generate a force in the plane parallel to the patient, is performed such that the force is substantially zero at the patient penetration point, and joint axes ( 20 a , 20 b ) of said first and second joints are vertical to each other, and the instrument axis ( 18 ) vertical to both joint axes ( 20 a , 20 b ) and includes an angle other than zero with the joint axes.