Eye muscle inspires piezo-actuator
The eye has inspired robot vision steering at Georgia Tech.
Key to the control system is a muscle-like piezoelectric actuator.
In muscle, many small actuator units are connected in series or in parallel.
“The actuators developed in our lab embody many properties in common with biological muscle, especially a cellular structure,” said researcher Joshua Schultz. “Essentially, in the human eye muscles are controlled by neural impulses. Eventually, the actuators we are developing will be used to capture the kinematics and performance of the human eye.”
While piezoelectric materials expand or contract when electricity is applied, the minuscule displacement of piezo-ceramics limits use in robotics.
In the Georgia Tech system “each muscle-like actuator consists of a piezoelectric material and a nested hierarchical set of strain amplifying mechanisms”, said fellow researcher Jun Ueda. “Unlike traditional actuators, piezoelectric cellular actuators are governed by the working principles of muscles – namely, motion results by discretely activating, or recruiting, sets of active fibres, called motor units.
The motor units are linked by flexible tissue, which serves two functions: combining the action of each motor, and presenting a compliant interface with the world, “which is critical in unstructured environments”, said Ueda.
A mathematical model has been developed which can to predict performance as well as help select the required geometry of nested structures.
“We use the design of the camera positioning mechanism’s actuators to demonstrate the concepts,” said Ueda.
It uses 16 amplified piezoelectric stacks per side.
“Multiple stacks addressed the need for more layers of amplification,” said the university. “The units were placed inside a rhomboidal mechanism.”
Details were presented at the IEEE International Conference on Biomedical Robotics and Biomechatronics in Rome.