How Surgical Robots Reconfigure Their Arms Without Moving the Tool Tip

This patent describes how a surgical robot arm can move and reshape itself to avoid obstacles or improve its position, all while keeping its surgical tool perfectly still at the patient's entry point or target.

What it covers

The patent details a method for a robot arm, like those used in surgery, to reconfigure its shape without disturbing the position or orientation of its working end, called the distal portion or end effector. When the robot receives a 'reconfiguration command' (Claim 1), it calculates specific joint velocities for its multiple joints. These calculated movements ensure that while parts of the arm shift, the distal portion remains in its 'desired state' (Claim 1), meaning its position, orientation, or velocity stays unchanged (Claim 4). This is achieved by ensuring the combined joint velocities lie within the 'null-space' of the manipulator arm's Jacobian (Claim 2), which means these joint movements have no effect on the end effector's position. For example, a surgeon could command the robot arm to move its elbow out of the way to prevent it from bumping into another instrument, all while the scalpel at the arm's tip remains precisely where it needs to be.

What it doesn't cover

• —Does not cover robot arm movements where the distal portion (the tool tip) is intended to move or change its state.
• —Does not cover robot arms that lack sufficient 'degrees of freedom' (extra joints) to allow for internal reconfiguration without moving the end effector.
• —Does not cover systems that reconfigure the arm by physically detaching and reattaching segments, rather than by coordinated joint movements.
• —Does not cover simple robot arm movements that only involve moving the end effector to a new position without any concurrent internal arm reconfiguration.
• —Does not cover reconfigurations that do not involve calculating joint velocities based on a kinematic Jacobian or similar mathematical model.

The clever bit

The core innovation is using the 'null-space' of the robot arm's kinematics. This mathematical concept identifies specific ways the robot's joints can move that change the arm's shape but have absolutely no effect on the position or orientation of the tool at its very end. This allows for internal arm adjustments without disturbing the surgical task.

Why it matters

In robotic surgery, maintaining the precise position of a surgical instrument is critical for patient safety and surgical accuracy. This patent allows surgical robots to adjust their posture, for instance, to avoid collisions with other instruments or to improve the robot's overall reach, without interrupting the delicate work being performed by the tool tip. This capability enhances the robot's dexterity and safety, making complex procedures more manageable and efficient for surgeons.

Real-world examples

• 1.Intuitive Surgical da Vinci surgical systems
• 2.Other advanced surgical robotic platforms
• 3.Industrial robots performing tasks requiring fixed tool points