Robots With Knives: A Study of Soft-Tissue Injury in Robotics

What would happen if a knife-wielding robot struck a person?

3 min read
Robot with knife
Image: DLR

A robot in the kitchen cooking you dinner may sound like a great idea. Just make sure you stay out of the way when it is handling the knives.

To find out what would happen if a robot holding a sharp tool accidentally struck a person, German researchers performed a series of stabbing, puncturing, and cutting experiments.

DLR robot arm with knife

They fitted an articulated robotic arm with various tools (scalpel, kitchen knife, scissors, steak knife, screwdriver) and programmed it to execute different striking maneuvers. They used a block of silicone, a pig’s leg, and at one point a human volunteer’s bare arm as the, uh, test surface.

The researchers—Sami Haddadin, Alin Albu-Schaffer, and Gerd Hirzinger from the Institute of Robotics and Mechatronics, part of the German Aerospace Center (DLR), in Wessling—presented their results today at the IEEE International Conference on Robotics and Automation, in Anchorage, Alaska.

The main goal of the study was to understand the biomechanics of soft-tissue injury caused by a knife-wielding robot. But the researchers also wanted to design and test a collision-detection system that could prevent or at least minimize injury. Apparently the system worked so well that in some cases the researchers were willing to try it on human subjects.

We applaud the man in the video getting his arm struck by the robot in the name of science [UPDATE: That’s Sami Haddadin, the study’s lead author, who was clearly confident in the safety system he and his colleagues devised].

Warning: The video includes scenes that some people may find upsetting.

The researchers acknowledge that there are serious concerns about equipping robots with sharp tools in human environments. But they argue that only by getting more data can roboticists build safer robots.

The experiments involved the DLR Lightweight Robot III, or LWRIII, a 7 degrees-of-freedom robot manipulator with a 1.1-meter reach and moderately flexible joints. The robot, which weighs 14 kilograms, is designed for direct physical interaction and cooperation with humans.

The tools the researchers tested included [right]: (1) scalpel; (2) kitchen knife; (3) scissors; (4) steak knife; (5) screwdriver.

The researchers performed two types of experiments: stabbing and cutting. The actions were done with the different tools at various speeds, with and without the collision-detection system active.

In most cases, the contact resulted in deep cuts and punctures, with potentially lethal consequences. But remarkably, the collision-detection system was able to reduce the depth of the cuts and in a few cases even prevent penetration altogether.

Although the robotic arm has a force-torque sensor on its wrist, this sensor is not used in the collision-detection system; it only serves as a measurement reference in the experiment. “The collision detection and reaction,” Haddadin told me, “is based on a very good dynamics model of the robot and the fact that, unlike other robots, we have torque sensors and position sensors in every joint.”

With the dynamics model (which includes rigid body dynamics, joint elasticity, and motor behavior) and the sensor measurements, the robot can detect a collision nearly instantaneously. (The control system relies on a “nonlinear disturbance observer.”)

“This method does not require any additional external sensors and only relies on the internal capabilities of the robot,” Haddadin says.

This is the first study to investigate soft-tissue injuries caused by robots and sharp instruments. Previous studies by the same researchers, as well as other groups, have focused on blunt collisions involving non-sharp surfaces.

The video below shows impact experiments using crash-test dummies and large industrial robots. Ouch.

The Conversation (0)

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Toyota’s Gill Pratt on enhancing independence in old age

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An illustration of a woman making a salad with robotic arms around her holding vegetables and other salad ingredients.
Dan Page
Blue

By 2050, the global population aged 65 or more will be nearly double what it is today. The number of people over the age of 80 will triple, approaching half a billion. Supporting an aging population is a worldwide concern, but this demographic shift is especially pronounced in Japan, where more than a third of Japanese will be 65 or older by midcentury.

Toyota Research Institute (TRI), which was established by Toyota Motor Corp. in 2015 to explore autonomous cars, robotics, and “human amplification technologies,” has also been focusing a significant portion of its research on ways to help older people maintain their health, happiness, and independence as long as possible. While an important goal in itself, improving self-sufficiency for the elderly also reduces the amount of support they need from society more broadly. And without technological help, sustaining this population in an effective and dignified manner will grow increasingly difficult—first in Japan, but globally soon after.

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