Research

FREEs are made of a hollow silicone or latex tube which is reinforced with inextensible fibers. The orientation of the fibers determine the nature of its deformation upon pneumatic or hydraulic actuation. Since FREEs are essentially inflatables, they can be modeled by solving a volume maximization problem with physical constraints due to the inextensibilty of fibers and strain energy stored in the elastomer.

There is a direct correlation between deformation of FREEs and their fiber orientations. This can be exploited to conduct an inverse design to optimize the FREE fibers so as to attain a required deformation profile. We have studied this thoroughly for designing FREEs to match a planar curve and also investigated FREEs that undergo snake like spiral winding. Our results are presented as design maps or charts and can be used without the need for computationally intensive solvers. In the video below the FREEs are designed to take the shape of ‘SoRo’ the acronym for the soft robotics journal.

(in collaboration with Prof. Elizabeth Hsiao-Wecksler, MechSE) This project aims to develop a soft robotic upper extremity orthosis for pediatric patients that use crutches for ambulation. While walking with crutches, peak loads observed in the wrist typically approach 50% of body weight and wrist postures experience extreme extension angles ~35°. These repetitive, high loads and poor wrist postures can lead to joint pain and injury, carpal tunnel syndrome, arthritis, or joint deformity. We have developed a light-weight (< 1 kg), pliable (tunable modulus of rigidity), powered (by <100 psi) wrist orthosis and integrated compact actuators to reduce these transient loads and associated wrist stresses by 50% and improve wrist posture to a more neutral position; therefore lowering the risk for joint injury such as carpal tunnel syndrome, while allowing for normal wrist and arm range of motion when not used for load bearing. We expand the range and functionality of contracting McKibben muscles by developing a robust analysis framework to generalize the construction and operating principles for FREE actuators to yield different deformation patterns.

We have developed a bio-inspired soft pneumatic robot that can achieve locomotion along the outside of a cylinder. The robot uses soft pneumatic actuators called FREEs (Fiber Reinforced Elastomeric Enclosure), which can have a wide range of deformation behavior upon pressurization. The robot being soft and compliant can grasp and move along cylinders of varying dimensions. Two different types of FREEs are used in the robot namely (a) extending FREEs and (b) bending FREEs. These actuators are arranged in such a way that the bending actuators are used to grip the pipe while the extending actuators generate forward motion as well as bending for direction control. The modular design of the robot provides simplicity and ease of maintenance. The entire robot is made of flexible actuators and can withstand external impact with minimal to no damage. The maximum speed achieved for horizontal motion is 4.2 mm/s and for vertical motion is 2.1 mm/s.