Robot imitates an elephant’s trunk

The Bionic Handling Assistant boasts an ultralight structure, nimble grippers, and servopneumatic control.
The elephant’s trunk is a remarkable tool — capable of lifting heavy loads, yet dexterous and sensitive enough to pick up a peanut. By analyzing its structure and motion, and taking advantage of new manufacturing techniques and high-speed servopneumatic controls, engineers at Festo, Esslingen, Germany, have developed a new lightweight, biomechatronic system that could change the way manufacturers handle products.

At first glance, the Bionic Handling Assistant resembles not so much a robotic arm but an organic structure with three basic elements: an arm, hand axis, and gripper with adaptive fingers.

The arm is made up of three segments, each comprised of three polyamide bellows actuators with a 3° taper running the length of the segment. Individual bellows cover about a third of the arm’s circumference, so actuating all three with compressed air linearly extends the arm. Pressurizing just one or two produces angular displacement. The bellows act like a spring and return to their original position when compressed air exhausts. Bowden cable potentiometers mounted outside the actuators track position and permit closed-loop control of movements.

The hand axis contains three additional bellows actuators surrounding a ball joint. Activating them displaces the gripper by angles up to 30°. Festo SMAT-8M position transmitters — compact, magnetic-proximity sensors with ±0.1-mm repeatability — track movements and make for precise alignment.

Finally, the FinGripper, with a design based on a fish’s tail fin, is what actually grasps the workpiece. Unlike conventional metal grippers or vacuum handlers, the FinGripper is light, flexible, and readily adapts to an object’s shape, which makes it particularly well suited for fragile and irregularly shaped products. It consists of a pneumatic bellows actuator (or, for longer life, a simple pneumatic cylinder) and three fingers. Compressed air actuates the bellows which, via lever action, opens and closes the fingers

The basic finger consists of two plastic bands which meet at one end to form a triangular structure. Intermediate stays that add strength connect to the bands via articulated joints. This flexible design lets the fingers adapt to the shape of a workpiece when pressure is applied laterally — just like a human hand, but much faster, according to company officials.

The Bionic Handling Assistant is 0.75 m long with a maximum extension of 1.1 m and an operating range (diameter) of 1.2 m. Thirteen actuators give the unit 11 degrees of freedom. It weighs only 1.8 kg but handles weights to 500 gm. Operating pressure is 1.5 to 3.0 bar.