How a Robot Arm Can Be Manually Moved While Staying Safe

This patent describes how a robotic arm can be partly moved by a human, like pushing it, while the robot's computer automatically handles other movements to keep it stable or avoid obstacles.

What it covers

The patent details a system for controlling a robotic manipulator arm, often used in applications like surgery. It features a "manipulation mode" where a processor fully controls the arm to move a tool (end effector) and pivot it around a fixed point (remote center). Crucially, it introduces "clutch modes" that allow a human to manually adjust parts of the arm's position. For example, in the "arm-null-perpendicular-clutch mode," the system automatically maintains the remote center's position (by "servoing" specific joints) while allowing a human to manually move the end effector (by "floating" other joints with friction or gravity compensation). Simultaneously, the system can perform "auxiliary tasks" like avoiding collisions or optimizing the arm's posture by controlling motion in the intersection of the remote center's and end effector's null-spaces, as described in claims 1, 7, and 8.

What it doesn't cover

• —Robot arms that are entirely manually operated without any computer assistance for stability or auxiliary tasks.
• —Systems where the robot arm cannot perform auxiliary tasks, such as collision avoidance or posture optimization, while being manually positioned.
• —Clutching mechanisms that do not involve actively "servoing" to maintain a specific point (like a remote center or end effector) while another part is "floated" by a user.
• —Robot arms that lack sufficient degrees of freedom to have a null-space for the end effector or remote center, which is necessary for the described concurrent control.
• —Systems that do not apply friction compensation or gravity compensation when allowing manual "floating" of the arm's joints.

The clever bit

The novelty lies in the concurrent control strategy: simultaneously allowing manual "floating" of certain arm movements (with friction/gravity compensation), actively "servoing" to maintain critical points like a remote center, and using the remaining "null-space" to perform background "auxiliary tasks" such as collision avoidance or optimizing joint positions.

Why it matters

This technology is vital for advanced robotics, particularly in surgical systems where surgeons need precise control but also benefit from the robot handling complex background tasks. It allows for a more intuitive and safer interaction between a human operator and a robot. This enables surgeons to focus on the primary task while the robot automatically manages critical constraints like maintaining a pivot point or preventing collisions, enhancing both precision and safety in delicate procedures.

Real-world examples

• 1.Intuitive Surgical da Vinci surgical systems
• 2.Other advanced robotic-assisted surgical platforms
• 3.Collaborative industrial robots (cobots) that allow human guidance
• 4.Robots used in hazardous environments requiring human-in-the-loop control