Magnetorheological elastomers (MREs), like MR fluids, exploit magnetic forces between ferromagnetic particles to produce a material with instantaneously adjustable properties of stiffness and damping with external magnetic fields. In MREs, the particles are a part of a structured elastomer matrix, and an external magnetic field is applied to achieve an instantaneous change of stiffness due to magnetic forces between particles. A drawback of conventional MREs is its inability of softening (reduce stiffness) under an external field. Many engineering applications need an instant change of its stiffness in both directions, which requires a magnetic bias embedded in the MRE. One way is the use of a permanent magnet (PM) for pre-straining a base elastomer matrix, but its mechanical design can be bulky due to the size of PM. In this paper, we address a fabrication process of the biased-magnetorheological elastomers (B-MREs) and their mechanical properties. The B-MREs consist of magnetized ferromagnetic particles as fillers and an elastomer as a binder. The magnetization of ferromagnetic particles embedded in the elastomer matrix eliminates a need for the use of the PM and can achieve the desired pre-strain in the B-MRE. The experiment results related with the mechanical properties after magnetization were presented. Also, different MRE thickness and weight ratios of the ferromagnetic particles mixed with the base elastomer were compared in both normal and shear modes.
Variable stiffness features can contribute to many engineering applications ranging from robotic joints to shock and vibration mitigation. In addition, variable stiffness can be used in the tactile feedback to provide the sense of touch to the user. A key component in the proposed device is the Biased Magnetorheological Elastomer (B-MRE) where iron particles within the elastomer compound develop a dipole interaction energy. A novel feature of this device is to introduce a field induced shear modulus bias via a permanent magnet which provides an offset with a current input to the electromagnetic control coil to change the compliance or modulus of a base elastomer in both directions (softer or harder). The B-MRE units can lead to the design of a variable stiffness surface. In this preliminary work, both computational and experimental results of the B-MRE are presented along with a preliminary design of the programmable variable stiffness surface design.
Ionic polymer metal composites (IPMCs) are one of the most widely used types of electro-active polymer actuator, due to their low electric driving potential and large deformation range. In this research a tube type IPMC was investigated. This IPMC has a circular cross section with four separate electrodes on its surface and a hole through the middle. The four separate electrodes allows for biaxial bending and accurate control of the tip location. One of the main advantages of using this type of IPMC is the ability to embed a specific tool and accurately control the tool tip location using the large deflection range of the IPMC. This ability has widespread applications including in the biomedical field for use in catheter procedures. In this paper the results of the bending and force experiments were examined to validate the performance of this actuator obtained from the theoretical three dimensional COMSOL Multipysics model. An electromechanical model of the IPMC was developed and integrated into a closed loop control system. To improve functionality and the user interface the control system was designed to work on a laptop touchpad. This will provide a more familiar and intuitive interaction and cut down on operator training time.
Ionic polymer-metal composites (IPMCs) have been and still are one of the best candidates with great potential to be used as actuators and sensors particularly in bioengineering where the environmental conditions are in an aqueous medium. Each component of an IPMC is important. However, the ion exchange membrane should be more emphasized because it is where ions migrate when electrical stimulation is applied and eventually it produces deformation of the IPMC. So far, the most commonly used ion exchange membrane is Nafion and many studies have been conducted with it for IPMC applications. There are a number of other commercially available ion exchange membranes now, but only a few studies have been done on those membranes to be used in IPMC applications. In this study, four commercially available membranes, (1) Nafion N115 (DuPont), (2) CMI7000S (Membranes International Inc.), (3) F-14100 (fumatech), (4) GEFC-700 (Golden Energy Fuel Cell) were selected and fabricated in IPMCs and their potentials as actuators were examined by conducting various characterizations such as water uptake, ion exchange capacity, SEM, DSC, blocking force and bending displacement.
Ionic polymer-metal composites (IPMCs) are some of the most well-known electro-active polymers. This is due to their large deformation provided a relatively low voltage source. IPMCs have been acknowledged as a potential candidate for biomedical applications such as cardiac catheters and surgical probes; however, there is still no existing mass manufacturing of IPMCs. This study intends to provide a theoretical framework which could be used to design practical purpose IPMCs depending on the end users interest. By explicitly coupling electrostatics, transport phenomenon, and solid mechanics, design optimization is conducted on a simulation in order to provide conceptual motivation for future designs. Utilizing a multi-physics analysis approach on a three dimensional cylinder and tube type IPMC provides physically accurate results for time dependent end effector displacement given a voltage source. Simulations are conducted with the finite element method and are also validated with empirical evidences. Having an in-depth understanding of the physical coupling provides optimal design parameters that cannot be altered from a standard electro-mechanical coupling. These parameters are altered in order to determine optimal designs for end-effector displacement, maximum force, and improved mobility with limited voltage magnitude. Design alterations are conducted on the electrode patterns in order to provide greater mobility, electrode size for efficient bending, and Nafion diameter for improved force. The results of this study will provide optimal design parameters of the IPMC for different applications.
In this study, we introduce a newly developed Ionic Polymer-Metal Composite (IPMC) family that is
manufactured using a novel ionic exchange membrane-a randomly sulfonated fluoropoly(ether amide)
(TFIPA-90)-as the base material. The thermal behavior and mechanical properties of the ionic polymer were
probed by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Electrochemical
properties and the actuation performance of the TFIPA-90 based IPMCs were also investigated in this study.
The stiffness of the TFIPA polymer was significantly higher than that of Nafion® and much noted at high
temperatures (>100 oC). The thermal behavior of the TFIPA polymer also showed better stability than Nafion(R)
at high temperatures due to the more rigid chemical structure of the ionomer. As an actuator, a new IPMC
prepared from TFIPA-90 showed improved performance with rapid response time to the electric field and a
large bending displacement. The TFIPA-based IPMC may be useful for microwave-driven robotic
In this paper, a finite element-based dynamic model is developed for a miniature underwater vehicle propelled by Ionic
Polymer Metal Composite (IPMC) actuator. The proposed approach describes the electro-mechanical actuation using a
large deflection beam model. Hydrodynamic forces including frictional effects are also considered. The hydrodynamic
force coefficients are identified based on the results of extensive computational fluid dynamics (CFD) simulations.
Experimental results have shown that the proposed model predicts the motion of the vehicle accurately for different
actuation signals. The proposed model can lead to the development of an underwater vehicle, which can achieve
complex set of maneuvers. It can also contribute to developing both open and closed-loop control algorithms for the
The numerous possible applications of the Ionic Polymer-Metal Composite (IPMC) as an underwater propulsor have lead to the investigation of the IPMC behavior in an aqueous environment. This study compares the performance of the IPMC when subjected to fluid drag forces to its performance without such forces. Both the form (i.e. pressure) drag and the viscous (i.e. skin friction) drag forces experienced by the IPMC due to the surrounding liquid are modeled. These forces are incorporated into an existing analytical model of a segmented IPMC1, which adequately models the relaxation behavior of the IPMC. It is important to note that it is assumed that the IPMC exhibits planar motion, i.e. the center of mass does not move in the direction normal to the plane of the bending motion, therefore the hydrodynamic model developed is 2-dimensional. The maximum IPMC deflection and amount of relaxation predicted for aqueous and non-aqueous environments are compared. Results from this model are used to assess the suitability of the IPMC for underwater use.
The objective of this paper is to derive a new adaptive control law for the control of the rotation angle of a smart projectile fin using a piezoelectric actuator. The smart projectile fin consists of a flexible cantilever beam with a piezoelectric active layer, which is mounted inside a hollow rigid fin and is hinged at the tip of the rigid fin. The rotation angle of the fin can be controlled by deforming the flexible beam. In the closed-loop system, asymptotic trajectory tracking of the fin angle is accomplished. Simulation results are presented which show that trajectory control of the fin angle is accomplished in spite of large uncertainties using adaptive control law and the flexible modes remain bounded during maneuvers.
This paper presents the mathematical modeling and predictive control of a magnetorheological fluid damper system. For the development of an effective controller precise modeling of the force-velocity characteristics of the MR damper is needed. Based on experimental data first the mathematical model for the MR damper is developed. Then a predictive controller is designed for the shock isolation of the payload mass. The design of the predictive controller is based on the optimization of a judiciously chosen performance index. The control input (electric current) is assumed to be bounded and positive for all time. Simulation results are presented which show that the developed mathematical model is effective in characterizing the behavior of the MR damper and the designed predictive controller is effective in the shock isolation of the payload.
The Ionic Polymer-Metal Composite (IPMC) for flexible hydrodynamic propulsor blades can provide many new opportunities in the naval platforms, especially in developing robotic unmanned vehicles for both surveillance and combat. IPMC materials are quietly operational since they have no vibration causing components, i.e. gears, motors,
shafts, and etc. For small Autonomous Underwater Vehicles (AUV), these features are truly attractive due to limited space. Also, IPMCs are friendly to solid-state electronics with digital programming capabilities. Active control is thus possible. Another advantage of these materials should be recognized from the fact that they can be operational in a self-oscillatory manner. There are several issues that still need to be addressed such as propulsor
design, testing, robotic control as well as theoretical modeling of the appropriate design. In this effort, IPMC is investigated for propulsor blades applications in NaCl solution and a propulsor model with a robust control scheme is explored. An analytical model of a segmented IPMC propulsor was formulated to be used as a building block for furthering the model to adequately accommodate the relaxation behavior of IPMCs and for describing the dynamics of the flexible IPMC bending actuator.
It has been observed that the Ionic Polymer-Metal Composite (IPMC) is both inherently resistive and capacitive. This allows for the material to be modeled using an equivalent RC circuit to describe the charging/discharging behavior associated with the IPMC. Typically, the model includes two resistors and two capacitors, which will primarily account for the effective electrodes on the surface of the IPMC (top and bottom). There will also be a resistor placed between the two RC circuits to account for material between the electrodes and the resistance due to ion migration through polymer matrix. In this paper we report our recent effort to extend such a model to accommodate a multi-layer IPMCs a swell as inter-digitated electrodes. As expected the observed electric characteristics of an IPMC subjected to an electric field is highly non-linear. This is believed to be due primarily to the particle electrodes on the IPMC surface, which is inherently both captive and resistive due to particle seperation and density. The advantage of using such a model is to realize the capacitive and resistive effect and use them for multi-layer configuration. We also present typical experimental data.
In this paper, the feasibility of using a magnetorheological (MR) fluid-based system for motion control is studied
based on the hysteretic biviscous model of the MR damper. A feedback control system is designed to synchronize
the motion of the two masses in a two degree of freedom spring-mass-damper system subject to an unknown
disturbance. The controller performance is evaluated numerically. For the derivation of the control law, a
quadratic Lyapunov function, which is a function of the relative position and velocity of two masses, is considered.
The control input (current) is obtained by minimizing the derivative of the Lyapunov function along the trajectory
of the system. In the computer simulation, it is observed that the controller is effective in synchronizing the two
The objective of this paper is to study the feasibility of using
smart material to control the rotation angle of a subsonic
projectile fin during flight. The fin produces maneuvering force
and moment which are utilized to control the projectile. In this
paper a beam model of piezoelectric actuator is used for rotating
the projectile fin. The fin, which is assumed to be rigid, is
rotated by a cantilever beam-based piezoelectric actuator whose
both end are attached to the projectile body and the fin. An
analytical model of the beam actuator is obtained by the finite
element approach with each element satisfying Euler-Bernoulli's
theorem. A feedback linearizing adaptive control system is
designed for the trajectory control of the fin angle. The
controller consists of an inverse system and a high gain observer.
Simulation results are presented which show that fin control is
accomplished in spite of uncertainties in the system.