Human hands are incredible. At one moment we are grasping eggs with not problem, at the other – we are crushing walnuts. This ability is due to feel – we can sense how much pressure needs to be applied in order to grasp the object, but not crush it. How can we teach robots that? Scientists at Michigan State University have designed a robotic hand that combines soft and hard architecture for safe repetitive gripping.
Industrial robots are using various specially developed grippers. They are not very universal though – each task requires a special tool. Meanwhile human hands are able to grip pretty much everything we need. So how do we transfer this ability to robots? Well, we use human hands as inspiration, obviously.
Scientists designed a humanoid hand where each finger is constructed from a flexible hybrid pneumatic actuator (FHPA), controlled via compressed air. Each finger can move independently from the others. While the fingers are soft, the hand is relatively rigid. Scientists say that this basically combines the best of both worlds – deformability, adaptability and compliance of soft grippers and a high level of stiffness for exerting strong clamping forces. This kind of a robotic gripper would allow lifting relatively heavy objects, while doing it gently.
These humanoid hands are soft due to the FHPA technology, but they are still quite rigid because of their bone-like spring core. They really are a lot like human hands. Changyong Cao, lead author of the study, said: “Traditional rigid grippers for industrial applications are generally made of simple but reliable rigid structures that help in generating large forces, high accuracy and repeatability. The proposed soft humanoid hand has demonstrated excellent adaptability and compatibility in grasping complex-shaped and fragile objects while simultaneously maintaining a high level of stiffness”.
There are soft grippers available already, but they are not very good, because they do not offer the necessary stability to handle fragile items. Most existing robotic grippers are not suitable for easily damaged objects. This is why fruits are still being harvested by hand in industrial fruit plantations. Scientists paid a lot of attention to human-environment interaction and now hope that this robotic soft-rigid gripper is going to come to commercial use.
Scientists say that this technology could benefit the industry. For example, these soft humanoid hands could be used in medical care, fruit plantations (they could even harvest apples, for example), automated packing and many other areas. In the future scientists are hoping to enhance their technology with printed sensors in the gripping material