Traditional robots are often moved with electric motors that are rigid, heavy, and can potentially be dangerous. Current robotic studies are shifting more and more toward soft robotics that are safe for human-robot interaction. Unlike traditional robots that are moved with motors, soft robots are moved with artificial muscles that are inherently compliant or soft. This is because artificial muscles are compliant or soft materials that can change their shapes under external stimuli such as temperature and voltage. They have shown strong potential in various applications, such as robot prosthetics, exoskeletons, and medical catheters. EXO Tech pursues new and developing soft robotic technology in the hopes of providing exoskeletal solutions to today’s problems.
Among soft robotic technologies, super coiled polymer [SCP] actuators exhibit many desirable muscle properties – they have demonstrated large actuation range, significant mechanical power, and are compliant and lightweight. Exo Tech is currently utilizing SCP technology in the development of an exoskeletal assistive glove. This device will be light, strong, and able to assist the user in everyday hand function. Further the glove will demonstrate the capabilities of SCP actuators.
Proof of Concept
Exo Tech plans to market the SCP assistive glove as a medical device, specifically looking at aiding those with arthritis. This is because the current products on the market either lack functionality, or utilize a technology that is inferior to SCP actuators. Some examples are Nuada’s glove which can only lock the hand, not assist it, and WYSS Institute’s pneumatic assistive glove that is impractical because of the large compressor that must be carried with the design.
To better prepare the product to compete in this market, EXO Tech has partnered with the University of Nevada, Reno’s Smart Robotics Lab directed by Dr.Jun Zhang. Specifically Dr. Zhang is experienced with SCP actuators making him a key person in the development of the glove.
The purpose of EXO Tech’s Proof of Concept [PoC] experiment was to confirm the model and mathematical findings on contraction, which were derived by a member of the team, Chris Mullen. Mullen created a mathematical model and calculated the required contraction of a Super Coiled Polymer [SCP] actuator in order to fully close a singular finger. Mullen found that the actuator would be required to contract a length of 2.8 centimeters in order to close the finger. Therefore, the purpose of the PoC was to confirm the accuracy of this model, empirically find the required SCP actuator length, and the force required to close the finger. In order to test this, EXO Tech took measurements of a team members finger and replicated appendage lengths in a Solidworks model. That model was then 3D printed using the resources found within the sponsors’ laboratory and assembled to replicate the articulation of a human index finger. The modeled finger was then attached to an SCP actuator and a load cell. The purpose of the load cell was to accurately measure the strain applied by the actuator to the finger.
Ultimately, the purpose of the PoC is to confirm that the SCP Actuated Assistive Glove has potential for real-world applications. Results of this experiment will not only show the strain required to close a singular finger, but also how long the SCP actuator must be. For example, if the actuator must be ten feet long or one foot long and if a single actuator is capable of outputting enough force to close the modeled finger.
Exo-Tech’s exoskeletal robotic assistive glove is intended to act as demonstration of the potential applications of SCP (Super Coiled Polymer) actuators in soft robotics and functions as an assistive device for augmenting the user’s grip. The primary goal of this product is demonstrate the potential of SCP soft robotic technology through in practical design and application. A robotic assistive glove demonstrates the potential of SCP actuators to be applied in a variety of industries, ranging from medical applications to space development.
Exo-Tech’s glove has been designed with specifications focused on improving the user’s grip strength and hand contractions in a rehabilitative and augmentative application. As a practical design usability and safety were the primary focus of the design specifications. An intuitive control mechanism through the use of EMG and flex sensors allows for easy operation of the glove. The glove was designed to be a flexible ergonomic semi-rigid exoskeleton to provide stability and comfort. Augmentation of the user’s grip strength and hand contractions is achieved through the flexible design and the control system developed for the SCP actuators. Due to unique actuator method of SCP actuators a large amount of continuous force can be applied with the proper controller and cooling system.
Exo-Tech’s final design produced from the design specifications will a glove-actuator system connected via metal wire. The glove will be a soft flexible fabric base with hard fixtures at the finger segments and palms to guide the wire along either side of each finger. The wires are connected to a separate housing for the SCP actuators that will act as the cooling unit and housing for the microprocessor. The microprocessor will process the inputs from the EMG and flex sensors into actuator contractions and operation of the active cooling unit.
Exo-Tech’s design will provide an augmentative robotic assistive glove that will demonstrate the practical use of SCP actuators and help further develop SCP technology.
Team EXO Tech approached the fabrication from individual subsystems first. Components for fabrication were either purchased or custom made based on desired design specifications. For custom components 3D printing was the primary manufacturing method used. Equipment was supplied by the team sponsor and his lab. The most unique manufacturing process was the manufacturing of Super Coiled Polymer [SCP] artificial muscles.
The SCP actuators were spun using a power supply, motor, and silver-coated nylon thread doubled back on itself four times pre-spinning (8-ply), and doubled back on itself under tension once after initial coiling to create the supercoiled structure. The supercoiled structure is then heat treated by applying a current through the actuator.
Housing for the SCP Actuators will be made from commercially purchased PVC tubes, a machined frame, and custom 3D printed components. The SCPs are cooled with commercially purchased fans attached to the PVC tubes with a custom printed adapter. The SCPs are fixed to housing with bolts attached to the adapter piece. At the exit end of the tubes the SCPs are connected to bike cables through a rotary potentiometer to measure the displacement of the actuators. From the exit end the cable are connected to the glove with brake tubing.
The glove component is constructed from custom 3D printed components and a purchased glove as the base. The printed ring components have been affixed to the glove with a temporary adhesive. Final prototyping will have the rings sewn into the glove. The rings will be connected with the cabling from the SCP housing. The brake tubing is held in place and guided with a wrist mount attached with a Velcro strap. Flex sensors are affixed to the back of the hand with Velcro and held in place with slots in the rings. The flex sensor control system is powered with an Arduino with a PWM MOSFET circuit as the base of the controller.
Testing and Results
Meet the Team
Aaron Wiese is from Granite Bay, California. Aaron has been a part of numerous engineering design projects and has earned his Eagle Scout award. Aaron is currently working on several projects for the UNR Smart Robotics Lab, including an actuator fabricator which required both programing and part design skills to complete. Aaron’s goal is to finish his bachelor degree in mechanical engineering which he expects to have finished in spring of 2018. Following his graduation, Aaron plans to continue his research at the UNR Smart Robotics Lab.
Anthony Johnson is from Las Vegas, Nevada. Growing up, Anthony’s father owned a company which was a forerunner in engineering American V8 and Subaru motors into various models of Porsches. Being around vehicles early on fueled his passion for learning how things function and has brought him to where he is today. One of the most challenging engineering projects Anthony has been a part of while attending the University of Nevada, Reno (UNR) was a magnet, “mine” seeking robot. In order to set his project apart from fellow competitors, he designed and built a telescoping arm that was capable of rotating nearly three-hundred degrees around the robot, while telescoping linearly approximately five inches. Another project, outside of school, that Anthony is proud of, consists of a “bead winder”. The customer was a jewelry and bead distributor and required a device that was capable of winding long strands of beads efficiently and affordably. Anthony began by designing the system by using analytical methods to ensure the device would not fail under the countless cycles and stress. The final product consisted of a smooth shaft, inserted into a set screw bearing, and bolted onto a steel frame. This was connected to an electric drill, which was operated by a foot petal. The device was a success and was much cheaper, stronger, and safer than any previous products used by the client. Through his studies at UNR, Anthony has developed a deep interest in control systems and looks forward to advancing his knowledge in this field to help him solve problems in his future career. Currently, as a senior at UNR, Anthony is working part-time doing computer aided design drafting, and after graduation, his goals are to work within the automotive industry, ideally working on vehicle crash safety.
Christopher Mullen is a senior mechanical engineering student at the University of Nevada, Reno. Mullen was raised in San Jose, California in a family of engineers. Mechanical engineering was natural choice when pursuing a higher education. Going into engineering was initially difficult due to Mullen’s previous trouble with math and science. Through effort and interest in engineering Mullen has developed proficiency with basic engineering principles with a greater interest in dynamic systems, fluid dynamics, and control systems. The most challenging engineering project Mullen has worked on was designing an autonomous robot to clear a simulated minesweeper game for an Intro to Mechanical Engineering course. Through this project Mullen gained an interest in autonomous systems and robotics. Mullen has taken additional classes in computer science and has developed skills with microcontrollers and other programing languages, such as Python, outside of the curriculum. Currently, Mullen is working on building a drone with some autonomous capabilities. This personal project has required the application of engineering skills and problem solving techniques. Mullen is eager to be working with Team Exo-Tech and the opportunity to gain hands on experience with soft robotics technology. Mullen intends to develop his interest in robotics and autonomous systems into a career.
Silvio P. Reggiardo
Silvio P. Reggiardo is from Cameron Park, California. Silvio is a senior mechanical engineering student attending University of Nevada, Reno. The most challenging engineering project Silvio worked on was a bridge project in a Statics class. Beyond simply picking a truss design that should have been strong, Silvio applied analytical techniques to optimize a truss design by leaving as many parameters in variable form as possible, creating a set of equations based on Statics principles, and optimizing the variables with the help of computer programming. The project was a success. Silvio in general developed the skills of solving for variables of systems and programming throughout his schooling. Outside of school, Silvio is proud of working to get a non-starting, partially disassembled, Model A to a limited driving condition. Silvio’s goal until graduation is to maintain a GPA sufficient to be accepted into graduate school, as an option. Silvio intends to work as an engineer upon graduation. The particulars of employment will beworked out based on aspects such as market factors, competency, and other circumstances.
Clayton Frieders is a senior mechanical engineering student. Being from Livermore, California and having family who have worked at the Lawrence Livermore National Laboratory has influenced Clayton’s decision to pursue a degree in mechanical engineering. The most challenging engineering project that he has been involved with was designing a hovercraft for his Engineering 101 class. This project tested his abilities to conceptualize designs, apply mathematics, and problem solve. During Clayton’s semesters at the University of Nevada, Reno (UNR), he has developed and improved upon many engineering skills. These skills range from applying math and science to creating concepts and implementing designs. An accomplishment that he is proud of is designing and constructing solar powered water pumps for wells on his grandparents country property. Using skills that he has learned through engineering classes at UNR, he was able to calculate the required wattage needed to power each pump for a certain amount of time. Additionally, he designed battery packs for the solar panels to charge while the pumps were not being used. The pump could then run off the battery packs at anytime, day or night. These designs allow for the pumps to draw water from an underground well that then will be given to livestock. His current goals are to help complete a prototype of an assistive glove for Team Exo Tech. After graduation he would like to apply his engineering skills to either the automotive, outdoor, or aerospace industry.