The Effect of Scale on Fluid-Filled Flexible Composite Actuators

2011 ◽  
Author(s):  
Larry D. Peel ◽  
Luis Muratalla ◽  
Jeff Baur ◽  
Dean Foster
Keyword(s):  
Incompressible Fluid ◽  
Mechanical Energy ◽  
Systems Design ◽  
Critical Length ◽  
Variable Stiffness ◽  
Micro Air Vehicles ◽  
Design Guidelines ◽  
Segment Length ◽  
Actuation Force ◽  
Opening And Closing

Morphing aircraft and other shape-changing structures are well suited to McKibben-like flexible composite actuators. These actuators, made from fiber-reinforced elastomeric composites, are extremely efficient in converting potential energy (pressurized air) into mechanical energy. Such actuators are promising for use in micro air vehicles, prosthetics and robotics because they offer excellent force-to-weight ratios and behave similar to biological muscle. Use of an incompressible pressurizing fluid instead of compressible air may also offer higher actuator stiffness, better control, and compatibility with existing actuation systems. Using incompressible fluids also allows the actuator to serve as a variable stiffness element which can be modulated by opening and closing valves that constrain or allow fluid flow. The effect of an incompressible fluid (water) on the performance of Rubber Muscle Actuators (RMA), with varying diameters, lengths and segment lengths, was experimentally investigated in the current work. Upon pressurization with air or water, past an activation threshold, overall force and stroke increased with increasing actuation length and diameter. Actuation force when pressurized with water is slightly greater than with air. Both air and water-pressurized actuation force and strain decrease significantly when segment length is less than a minimum critical length. Closed valve actuator stiffness (modulus) of actuators at full length, when pressurized with an incompressible fluid is up to 60× greater than the open valve stiffness of the same actuator. Air-filled RMAs with equal parameters only see a 10× increase. Incompressible fluid-filled RMAs have great potential to provide needed high actuation forces within adaptive material systems. Design guidelines are given to aid additional RMA use.

Toward a User-Centered Method for Studying CVEs for Learning

2005 ◽  
pp. 269-301 ◽  
Author(s):  
Daphne Economou ◽  
Steve Pettifer
Keyword(s):  
Interaction Analysis ◽  
Systems Design ◽  
Design Guidelines ◽  
Research Community ◽  
Collaborative Virtual Environments ◽  
Rigorous Approach ◽  
Third Phase ◽  
Virtual Actors ◽  
Design Factors ◽  
Grid Based

This chapter addresses one of the challenges the collaborative virtual environments (CVEs) research community faces which is the lack of a systematic approach to study social interaction in CVEs, determine requirements for CVE systems design, and inform the CVE systems design. It does this by presenting a method for studying multi-user systems in an educational context. The method has been developed as part of the Senet project, which is investigating the use of virtual actors in CVEs for learning. Groupware prototypes are studied in order to identify requirements and design factors for CVEs. The method adopts a rigorous approach for organizing experimental settings, collecting and analysing data, and informing CVE systems design. The analysis part of the method shares many of the Interaction Analysis foci and expands on it by providing a grid-based method of transforming rich qualitative data in a quantitative form. The outcome of this analysis is used for the derivation of design guidelines that can inform the construction of CVEs for learning. The method is described by a third phase of work in the Senet project.

Variable-Stiffness–Mode Dielectric Elastomer Devices

2008 ◽  
Vol 61 ◽  
pp. 192-201 ◽  
Author(s):  
Ron Pelrine ◽  
Roy Kornbluh
Keyword(s):  
Smart Materials ◽  
Dynamic Range ◽  
Low Cost ◽  
Mechanical Energy ◽  
Mechanical Impedance ◽  
Variable Stiffness ◽  
Dielectric Elastomer ◽  
Dielectric Elastomers ◽  
Electromechanical Transduction ◽  
Broad Dynamic Range

Dielectric elastomers, or more precisely dielectric polymers, are a relatively new class of materials for variable-stiffness and variable-damping devices. Dielectric elastomers offer significant potential advantages compared with previous variable stiffness smart materials. Advantages include simplicity, broad dynamic range, ability to reach zero stiffness, low cost, minimal mass, shock tolerance, simple drive circuitry, and design flexibility. Dielectric elastomer devices in the variable-stiffness mode convert electrical and mechanical energy back and forth to change mechanical impedance. This type of electromechanical transduction distinguishes the variable stiffness mode from simply using a dielectric elastomer actuator to alter the geometry, and hence the stiffness, of the device. Stiffness using a variable-stiffness mode depends heavily on the electrical loading of the dielectric elastomer. Analysis shows that a constant voltage loading reduces stiffness, down to zero in some cases, while a constant charge loading increases stiffness. Many applications can be considered for dielectric elastomer variable-stiffness mode such as vibration control, suspensions, and tuning consumer devices for user comfort or preference. As with dielectric elastomer actuators and generators, silicones and acrylics are the most promising materials for variable-stiffness-mode devices.

Granular Jamming With Hydraulic Control

2013 ◽  
Author(s):  
Allen Jiang ◽  
Tomaso Aste ◽  
Prokar Dasgupta ◽  
Kaspar Althoefer ◽  
Thrishantha Nanayakkara
Keyword(s):  
Particulate Matter ◽  
Incompressible Fluid ◽  
Comparative Studies ◽  
Variable Stiffness ◽  
Vacuum Pressure ◽  
Soft Robotics ◽  
Hydraulic Control

In the field of soft robotics, granular jamming is a newly adopted variable stiffness mechanism involving the use of vacuum pressure to control soft, particulate matter to become a unified, solid-like structure. However, granular jamming is conventionally controlled with air, which reduces the mobility of the robot. This is because the compressibility of air requires large vacuum pumps or chambers. Instead, we propose the use of an incompressible fluid, such as water, to control the stiffness of the mechanism. This paper presents comparative studies that shows that a hydraulic granular jammed joint using deaired water can both achieve the same stiffness level with just one twentieth of the volume extraction and maintain the same hysteresis level of an air-based system.

Sign in / Sign up

Export Citation Format

Share Document