Wayne Walter

Development of a prototype over-actuated biomimetic prosthetic hand.

The loss of a hand can greatly affect quality of life. A prosthetic device that can mimic normal hand function is very important to physical and mental recuperation after hand amputation, but the currently available prosthetics do not fully meet the needs of the amputee community. Most prosthetic hands are not dexterous enough to grasp a variety of shaped objects, and those that are tend to be heavy, leading to discomfort while wearing the device. In order to attempt to better simulate human hand function, a dexterous hand was developed that uses an over-actuated mechanism to form grasp shape using intrinsic joint mounted motors in addition to a finger tendon to produce large flexion force for a tight grip. This novel actuation method allows the hand to use small actuators for grip shape formation, and the tendon to produce high grip strength. The hand was capable of producing fingertip flexion force suitable for most activities of daily living. In addition, it was able to produce a range of grasp shapes with natural, independent finger motion, and appearance similar to that of a human hand. The hand also had a mass distribution more similar to a natural forearm and hand compared to contemporary prosthetics due to the more proximal location of the heavier components of the system. This paper describes the design of the hand and controller, as well as the test results.

An Investigation of Electrochemomechanical Actuation of Conductive Polyacrylonitrile (PAN) Nanofiber Composites

A polymer-based nanofiber composite actuator designed for contractile actuation was fabricated by electrospinning, stimulated by electrolysis, and characterized by electrochemical and mechanical testing to address performance limitations and understand the activation processing effects on actuation performance. Currently, Electroactive polymers (EAPs) have provided uses in sensory and actuation technology, but have either low force output or expand rather than contract, falling short in capturing the natural kinetics and mechanics of muscle needed to provide breakthroughs in the bio-medical and robotic fields. In this study, activated Polyacrylonitrile (PAN) fibers have demonstrated biomimetic functionalities similar to the sarcomere contraction responsible for muscle function. Activated PAN has also been shown to contract and expand by electrolysis when in close vicinity to the anode and cathode, respectively. PAN nanofibers (~500 nm) especially show faster response to changes in environmental pH and improved mechanical properties compared to larger diameter fibers. Tensile testing was conducted to examine changes in mechanical properties between annealing and hydrolysis processing. Voltage driven transient effects of localized pH were examined to address pHdefined actuation thresholds of PAN fibers. Electrochemical contraction rates of the PAN/Graphite composite actuator demonstrated up to 25%/min. Strains of 58.8%, ultimate stresses up to 77.1 MPa, and moduli of 0.21 MPa were achieved with pure PAN nanofiber mats, surpassing mechanical properties of natural muscles. Further improvements, however, to contraction rates and Young’s moduli were found essential to capture the function and performance of skeletal muscles appropriately.

Exploration of a hybrid locomotion robot

Within the Kate Gleason College of Engineering (KGCOE) at the Rochester Institute of Technology (RIT), there has arisen a need for an efficient, variable-terrain robotic platform, with the ability to carry a payload with precision. This paper provides an overview of the work done toward the development of a hybrid locomotion robotic platform. The platform combines the benefits of both walking and rolling into a single integrated system. The robot will be shown to have the ability to traverse various terrain and obstacles.Copyright

Design, Build, and Test of Modular Mobile Micro Robots

This paper presents a novel architecture for a mobile micro robot design. The architecture will have hardware and software modularity. The modular architecture of the platform provides “plug-and-play” capability that will allow hardware and software subsystems to be easily swapped. This paper focuses on vertical hardware modularity in the sense that modules will not be identical to each other but have common connectivity. Our approach slices a robot into functional modules such as locomotion, control, sensors, communication, and actuation. Any mobile robot can be constructed by combining the above abstract modules. A sub-module is a piece of hardware, which accomplishes the functionality of an abstract module, i.e. a wireless communication sub-module for a communication module. The software architecture consists of abstract classes and their objects. The abstract classes are “robot”, “locomotion”, “control”, “communication”, “sensor”, and “actuators”. From these abstract classes, concrete classes are derived. The objects are going to be created from the concrete classes. For example, “wireless” can be a class inherited from “communication” class. Then, an instance of “wireless” class can be created as the communication module in the robot. The objects (tasks) are dynamically loaded into the robots so that the modular OS can run the tasks on the sub-module it has. The paper explores generations of micro robot designs with modular architecture.Copyright

An Intelligent Robotic System Platform for Autonomous Mapping and Sensor Data Gathering of Non-GPS Friendly Environments

This paper presents results of a novel intelligent robotic system using a re-configurable platform for autonomous mapping and sensor data gathering of non-Global Positioning System (GPS) friendly, unknown and hazardous enclosed environments such as caves, underground and underwater tunnel networks, building floors, and spaces within a collapsed building rubble field. The work developed here forms a basis for a swarm of mini/micro robotic vehicles capable of autonomous routing and control with a self-contained navigation system that does not rely on GPS information. A robotic prototype capable of autonomously mapping a floor plan (such as hallways within a building) has been developed. The robot navigates autonomously without the use of GPS and gathers absolute position information developing a 2-dimensional map of the hallway network using a novel Mini Inertial Measurement/Navigation System (MIMNS) developed at RIT. Also, enhancements to the MIMNS unit are presented for estimating attitude orientation of the robot using an accelerometer based device allowing for non-flat plane mapping using the MIMNS unit. The paper presents the concepts of the robot hardware and software, results of a 2-dimensional mapping of a flat plane, and introduces simulation results of an accelerometer based attitude orientation device.Copyright

Undergraduate Robotics Education on a Shoestring

The paper traces the development of the robotics program in the Mechanical Engineering Department at RIT with absolute minimal financial support from the departmental budget. The paper discusses how student robotics projects at local industries have provided real-world problems for students to work on, as well as exposure to state-of-the-art hardware and software that RIT cannot afford. The paper also discusses some of the problems that have been worked out including initiating and maintaining academic/industry relationships, getting students access to equipment to the industrial site, and the question of students’ patent rights. Some typical student projects are discussed.

Optimization study for fabrication of micro-scale stacked dielectric elastomer actuators

Fabrication of micro-scale DEAs could benefit many fields including micro-robots, micro-optical systems besides reducing the driving voltage from kV scale to possibly sub-100V range. In an earlier study, proof of concept fabrication methods for PDMS-based fiber-like micro-sized stacked dielectric elastomer actuators were introduced. This study tried to optimize the fabrication process by investigating the effect of different fabrication approaches and different design geometries on the performance of micro-sized DEAs. Micro-sized DEAs with different geometrical parameters were fabricated. Several fabrication steps were modified and the effectiveness of the new fabrication steps and parameters were investigated.

Microfabrication of stacked dielectric elastomer actuator fibers

Dielectric elastomer actuators (DEA) are one of the best candidate materials for next generation of robotic actuators, soft sensors and artificial muscles due to their fast response, mechanical robustness and compliance. However, high voltage requirements of DEAs have impeded their potential to become widely used in such applications. In this study, we propose a method for fabrication of silicon based multilayer DEA fibers composed of microlevel dielectric layers to improve the actuation ratios of DEAs at lower voltages. A multi-walled carbon nanotube - polydimethylsiloxane (MWCNT/PDMS) composite was used to fabricate mechanically compliant, conductive parallel plates and electrode connections for the DEA actuators. Active surface area and layer thickness were varied to study the effects of these parameters on actuation ratio as a function of applied voltage. Different structures were fabricated to assess the flexibility of the fabrication method for specific user-end applications.

Development of a Two-Dimensional Model of the Human Arm to Investigate the Biomimetic Substitution of Human Bicep Muscle With a Dielectric Electroactive Polymer Muscle Actuator

Current prostheses are not able to meet the needs of patients. The authors have recently been investigating the feasibility of integrating multiple types of electroactive polymers (EAP) to develop an artificial muscle for prostheses and muscle implants; much like biological muscle is made up of multiple types of muscle fibers. The intent is to produce a lightweight device which has smooth fluid-like motion, in contrast to the jerky motion of current prostheses which use heavy rotary actuators. A human arm model, isolating the bicep muscle, was developed to better understand the requirements on force and strain that an artificial muscle must meet to replace biological muscle. This study was conducted with the assistance of orthopedic surgeons from the Rochester General Hospital. Bicep muscle characteristics were compared with those of dielectric elastomer electroactive polymers (DEAP), since they produce relatively high force and large strain during actuation. Results show that current characteristics of DEAPs will not allow for direct substitution of human muscle fibers with EAPs because their force and strain outputs are too low. To increase the force and strain output of DEAPs to that of human muscle fibers, the stiffness of the DEAP needs to be increased. The analysis done and results obtained are discussed in the paper, as well as possible ways to increase the stiffness of EAPs to better meet the requirements for biological muscle replacement.Copyright

Feasibility of Integrating Multiple Types of Electroactive Polymers to Develop an Artificial Human Muscle

Electroactive polymers (EAPs) have been labeled as the future stakeholder for artificial muscle technology and machine actuation. The US Armed Forces have seen an increased population of service members suffering from loss of limbs as a result of conflicts overseas. Civilian populations have suffered as well, due to muscle tissue deterioration brought on by injury or disease. Many prosthetic limbs have been engineered with rotary actuation, but do not mimic fluid motion as human muscles do. Through the research of biomimetics, imitating nature and applying those techniques to technology, electroactive polymers have been found to produce the fluid-like characteristics of biological muscles as needed for precise artificial simulation. These materials exhibit common traits of biological muscle tissue regarding potential energy storage. When activated by an electrical voltage potential, EAPs can produce characteristics such as: bending/axial strain or changes in viscosity. One classification of electroactive polymers, Ionic EAPs, exhibit bipolar activation under low voltages and can be found in various physical states; solid, liquid, and gel states. These characteristics make Ionic EAPs the most attractive materials to be used in low energy or mobile applications, such as exoskeletons and implants. For high strain and large load applications, electronic EAPs can be used. Electronic EAPs require high voltages which induces high rates of strain and large deformations. To date, it appears that various types of EAP materials are being used individually, as opposed to integrated with other types. Biological muscles are made of many different proteins organized in an optimized geometrical structure which yields a more efficient response combined than achieved individually. The focus of the current project is to integrate multiple EAP materials in a designed mechanical system to produce a closer representation of a biological muscle. The status of this RIT project; to design, fabricate, and test an integrated EAP-based artificial muscle will be discussed along with the conceptual thinking for design obtained to date.© 2010 ASME