At the beginning of the Covid-19 pandemic, car manufacturing companies such as Ford quickly shifted their production focus from automobiles to masks and ventilators.
To make this switch possible, these companies relied on people working on an assembly line. It would have been too challenging for a robot to make this transition because robots are tied to their usual tasks.
Theoretically, a robot could pick up almost anything if its grippers could be swapped out for each task. To keep costs down, these grippers could be passive, meaning grippers pick up objects without changing shape, similar to how the tongs on a forklift work.
A University of Washington team created a new tool that can design a 3D-printable passive gripper and calculate the best path to pick up an object. The team tested this system on a suite of 22 objects – including a 3D-printed bunny, a doorstop-shaped wedge, a tennis ball and a drill.
The designed grippers and paths were successful for 20 of the objects. Two of these were the wedge and a pyramid shape with a curved keyhole. Both shapes are challenging for multiple types of grippers to pick up.
The team will present these findings August 11 at SIGGRAPH 2022.
Senior author Adriana Schulz, a UW assistant professor in the Paul G. Allen School of Computer Science & Engineering, says: “We still produce most of our items with assembly lines, which are really great but also very rigid. The pandemic showed us that we need to have a way to easily repurpose these production lines.
“Our idea is to create custom tooling for these manufacturing lines. That gives us a very simple robot that can do one task with a specific gripper. And then when I change the task, I just replace the gripper.”
Passive grippers can’t adjust to fit the object they’re picking up, so traditionally, objects have been designed to match a specific gripper.
Co-author Jeffrey Lipton, UW assistant professor of mechanical engineering, says: “The most successful passive gripper in the world is the tongs on a forklift. But the trade-off is that forklift tongs only work well with specific shapes, such as pallets, which means anything you want to grip needs to be on a pallet.
“Here we’re saying, ‘OK, we don’t want to predefine the geometry of the passive gripper’. Instead, we want to take the geometry of any object and design a gripper.”
For any given object, there are many possibilities for what its gripper could look like. In addition, the gripper’s shape is linked to the path the robot arm takes to pick up the object.
If designed incorrectly, a gripper could crash into the object en route to picking it up. To address this challenge, the researchers had a few key insights.
Lead author Milin Kodnongbua, who completed this research as a UW undergraduate student in the Allen School, says: “The points where the gripper makes contact with the object are essential for maintaining the object’s stability in the grasp. We call this set of points the ‘grasp configuration.
“Also, the gripper must contact the object at those given points, and the gripper must be a single solid object connecting the contact points to the robot arm. We can search for an insert trajectory that satisfies these requirements.”
When designing a new gripper and trajectory, the team …….