Method for controlling a robot arm, and robot for implementing the method

• US 7,646,161 B2
• Filed: 11/15/2006
• Issued: 01/12/2010
• Est. Priority Date: 11/16/2005
• Status: Active Grant

• Current Assignee: Brainlab AG, Deutsches Zentrum Fã¼R Luft- Und Raumfahrt E.V., Deutsches Zentrum Fuer Luft- Und Raumfahrt E.V.
• Original Assignee: Brainlab AG, Deutsches Zentrum Fuer Luft- Und Raumfahrt E.V.
• Inventors: Ortmaier, Tobias, Albu-Schäffer, Alin, Hagn, Ulrich, Ott, Christian
• Primary Examiner(s): Leykin; Rita
• Application Number:
  US11/600,959
• Publication Number:
  US 20070120512A1
• Time in Patent Office: 1,154 Days
• Field of Search: 318/568.2, 318/568.21, 700/245, 700/249, 700/254, 700/259, 700/248, 700/261, 901/1, 901/30, 901/41, 248/282.1, 248/274.1, 248/276.1, 248/278.1
• US Class Current: 318/568.2
• CPC Class Codes: A61B 2090/064 for measuring force, pressure or mechanical tension
• CPC Class Codes: A61B 34/70 Manipulators specially adapted for use in surgery
• CPC Class Codes: A61B 34/76 Manipulators having means for providing feel, e.g. force or tactile feedback
• CPC Class Codes: B25J 13/085 Force or torque sensors B25J13/082, B25J13/084 take precedence
• CPC Class Codes: B25J 9/1633 compliant, force, torque control, e.g. combined with position control
• CPC Class Codes: B25J 9/1643 redundant control
• CPC Class Codes: G05B 2219/40599 Force, torque sensor integrated in joint

Abstract

In a method for controlling a robot arm, which is particularly suitable for use in medical applications, a robot arm (10) with a redundant number of joints is used. A torque acting in at least one joint (12a, 12b) is sensed. By means of a control device, the torque acting in this joint (12a, 12b) is controlled to become substantially 0.

Claims

1. 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 (12a, 12b) 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 (12a), 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 (20a, 20b) of said first and second joints are vertical to each other, and the instrument axis (18) vertical to both joint axes (20a, 20b) and includes an angle other than zero with the joint axes.

2. The method of claim 1, wherein the control using the control device is performed when predetermined limit values are exceeded or under-run.

3. The method of claim 1, wherein the control is effected using a zero moment control.

4. The method of claim 1, wherein the joints (12a, 12b) connected with a joint connecting element (16) that is closest to the element of the environment are controlled.

5. The method claim 1, wherein correction terms are included in the control to compensate for moments and/or forces caused by inertia and/or friction.

6. The method of claim 1, wherein the control of the robot arm is supported by a haptic flow of information.

7. The method of claim 1, wherein at least one of the joints controlled is adapted to be switched to a controlled free movement.

8. The method of claim 1, wherein, due to the redundant number of joints, a change of position of at least one connecting element (16) is possible through haptic interaction without changing the position of the end effector, the forces acting on the edge of the opening being substantially zero.

9. The method of claim 1, wherein the optimized quality criterion is alignment of the two zero moment controlled axes substantially vertical to the instrument axis.

10. A robot, for use in medical applications, comprising

a robot arm (10) with a plurality of joints (12), the number of joints being redundant, connecting elements (16) being arranged between the joints (12), an end effector, and actuators and torque sensors (14, 22) connected with the joints (12) and/or the connecting elements (15), wherein a first and a second joint (12a, 12b) are connected with a connecting element (16) and the first and second joints (12a, 12b) are arranged closest to an element of the environment and

a control device, connected with the torque sensors (14, 22) and the actuators, for executing the method of claim 1 wherein said first joint (12a), a joint closest to the element of the environment, includes a torque sensor (14, 22) wherein the torque sensor is an internal torque sensor (14) integrated in the joint and/or a torque sensor (22) connected with the adjacent connecting element (16).

11. The method of claim 3 wherein the control is effected using an impedance control.

12. The method of claim 3 wherein the control is effected using an admittance control.

13. The method of claim 3 wherein the control is effected using an impedance projection.