New Robotic Device Mimics the Adjustable Grip of a Human Hand

Human hands are extremely adept at controlling many different objects. Humans can hammer a nail or pick up a strawberry or an egg without breaking it.

One trait that enables humans to carry out a wide range of tasks is the potential to modify the firmness of their grip. Now, engineers at the University at Buffalo (UB) have created a novel two-fingered robotic hand that shares this characteristic.

The robotic hand is designed so that it can absorb the energy from the impacts caused during collisions. This makes sure that the objects held by the robot are not broken, whatever they may be. This also makes it safer for individuals to work with and close to the machines.

Such grippers can serve as a handy asset for human-robot relationship in assembly lines, in the electronic packaging, automotive, and other sectors, stated Ehsan Esfahani, PhD, associate professor of mechanical and aerospace engineering in the UB School of Engineering and Applied Sciences.

Our robotic gripper mimics the human hand’s ability to adjust the stiffness of the grip. These grippers are designed for collaborative robots that work together with people,” “They’re going to be helpers, so they need to be safe, and variable stiffness grippers help to achieve that goal.

Ehsan Esfahani, PhD and Associate Professor, Department of Mechanical and Aerospace Engineering, School of Engineering and Applied Sciences, UB

A recent research reported online on September 10^th, 2019, in IEEE Transactions on Industrial Electronics points out the safety design of the device. This also included experiments that demonstrated how the shock-absorbing features of the gripper prevent a spaghetti stick from breaking at the time of the collision.

Esfahani revealed that magnets are responsible for the versatility of the robotic gripper. Rather than having a pair of fingers fixed in place, each finger of the gripper has a magnetic base that is located between a pair of neodymium magnets that push or repulse against the finger.

Between the magnets, the air gap serves like a spring and creates a slight push when the hand collides with an external force or picks up an object. In addition, the space between the magnets can be increased or decreased by adjusting the grip’s stiffness.

Esfahani and Amirhossein Memar, a former UB PhD candidate in mechanical and aerospace engineering, reported these safety features in the new paper.

In one group of tests, the researchers positioned a short stick of spaghetti in a lengthwise fashion between the robotic hand’s fingers. When the robotic gripper smashed into a fixed object, the device was able to detect the external force being applied. This caused the magnets to alter their position, momentarily decreasing the grip’s stiffness and enabling the gripper to absorb some of the energy caused by the collision. The outcome was that the spaghetti stick did not break.

Next Steps in Development

Esfahani observed that the gripper being developed by his group can be fixed to robot arms available in the market. Such robot arms are already being used in numerous facilities. This may reduce the cost of implementing the technology for companies keen on enhancing the capabilities and safety of current machines.

Esfahani is licensing the technology from UB and will shortly set up a startup company to market the gripper.

The Buffalo Fund: Accelerator—funded by the Innovation Hub—has awarded $55,000 to Esfahani’s team to further improve the robotic gripper. The Innovation Hub is administered by UB and supported by Empire State Development. Apart from optimizing the existing design of the robotic hand, the researchers may also investigate other developments, like introducing a third finger.

Scientists who played a part in developing and testing the robotic gripper include PhD student Sri Sadhan Jujjavarapu and Memar, the co-author on the latest spaghetti stick study, who earned his PhD from UB and is currently a postdoctoral research scientist at Facebook Reality Labs.

(Video credit: University at Buffalo)