Current knee designs for prosthetic legs rely on electric motors for both moving and stationary states. The electric motors draw an especially high level of current to sustain a fixed position. The advantage of using magnetorheological (MR) fluid is that it requires less current and can have a variable braking torque. Besides, the proposed prosthetic leg is actuated by NiTinol wire, a popular shape memory alloy (SMA). The incorporation of NiTinol gives the leg more realistic weight distribution with appropriate arrangement of the batteries and wires. The prosthesis in this research was designed with MR brake as stopping component and SMA wire network as actuating component at the knee. The MR brake was designed with novel non-circular shape for the rotor that improved the braking torque while minimizing the power consumption. The design also helped simplify the control of braking process. The SMA wire network was design so that the knee motion was actively rotated in both directions. The SMA wires were arranged and played very similar role as the leg’s muscles. The study started with the overall solid design of the knee including both MR and SMA parts. Theoretical models were derived and programmed in Simulink for both components. The simulation was capable of predicting the power required for moving the leg or hold it in a fixed position for a certain amount of time. Subsequently, the design was prototyped and tested to validate the theoretical prediction. The theoretical models were updated accordingly to correlate with the experimental data.
Modern vehicles have been increasingly equipped with advanced technologies such as hybrid and cylinder-on-demand to
enhance fuel efficiency. These technologies also come with vibration problems due to the switching between the power
sources or the variation of the number of active cylinders. To mitigate these vibrations, a large variety of vibration
isolators have been proposed, ranging from passive to active isolators. Semi-active mounts are often preferred to other
solutions because of their overall low power requirement in operation as well as relatively simpler configurations.
Among the semi-active categories, the magnetorheological fluid (MRF) mounts have been proven to be a viable solution
for modern vehicle vibration isolation. These mounts can change their stiffness and damping characteristic without
involving moving parts, by controlling the yield stress of the MRF housed inside the mount by means of magnetic field.
This study looked into several innovative designs for MRF mounts. The characteristics of the mount depend significantly
on the compliances of the rubber, the number and arrangement of the fluid chambers and the number of flow passages
connecting the chambers. These parameters provide the designers with various options to design the mounts to function
in various conditions and over a wide range of frequencies. Different values of the aforementioned parameters were
selected to form specific designs with certain characteristics. Mathematical models have been developed for each design
and MATLAB/Simulink was used to simulate the response of each mount to certain excitations. As the hydraulic and
magnetorheological (MR) effects are dominant in the mount, the elastomer behavior is considered linear.
A discussion of the advantages and disadvantages of each design, based on the simulated response, is presented. The outcomes of this study can be a useful reference for MRF mount designers and leads to the development of a general MRF mount design methodology.
Magnetorheological (MR) fluid has been increasingly researched and applied in vibration isolation devices. To date, the
suspension system of several high performance vehicles has been equipped with MR fluid based dampers and research is
ongoing to develop MR fluid based mounts for engine and powertrain isolation. MR fluid based devices have received
attention due to the MR fluid's capability to change its properties in the presence of a magnetic field. This characteristic
places MR mounts in the class of semiactive isolators making them a desirable substitution for the passive hydraulic
In this research, an analytical model of a mixed-mode MR mount was constructed. The magnetorheological mount
employs flow (valve) mode and squeeze mode. Each mode is powered by an independent electromagnet, so one mode
does not affect the operation of the other. The analytical model was used to predict the performance of the MR mount
with different sets of parameters. Furthermore, in order to produce the actual prototype, the analytical model was used to
identify the optimal geometry of the mount.
The experimental phase of this research was carried by fabricating and testing the actual MR mount. The manufactured
mount was tested to evaluate the effectiveness of each mode individually and in combination. The experimental results
were also used to validate the ability of the analytical model in predicting the response of the MR mount. Based on the
observed response of the mount a suitable controller can be designed for it. However, the control scheme is not
addressed in this study.
Recently, widespread attention has been directed towards scavenging energy from renewable sources such as wind.
Piezoelectric materials are particularly suitable for capturing energy from motion since mechanical deflection of a
piezoelectric specimen results in an electric displacement. This electricity can be stored in batteries or used to power
portable devices. The present work is on the development of a device that can generate electricity from an oscillating
motion using a piezoelectric Macro Fiber Composite (MFC) bimorph. Previously, bimorph vibration was created by a
rotating or reciprocating part hitting the bimorph tip; whereas in the current work, base reciprocation excites the
piezoelectric bimorph. The device includes a fan blade, which aligns with the direction of the wind and moves a rod in
vertical direction. The microfiber composite beams (MFC) are attached to the upper end of the rod. Reciprocation of the
rod acts as a harmonic excitation for the MFC bimorphs. Vibration of the MFCs produces electricity which is stored in a
capacitor to be used to power electronic systems such as different types of remote sensors. Simulation and experimental
results have been compared. In vibration and wind tunnel experiments, comparable amounts of energy were collected
and accumulated in a capacitor.
Noise and vibration have always affected not only the operation of various devices but also people's comfort. These
issues are highly present in currently emerging technologies like hydraulic launch assist vehicles. While the switching
mechanisms in hydraulic hybrid vehicles enhance fuel efficiency, they cause complicated patterns of noise and vibration.
This, combined with a wider range of frequencies excited by this mechanism requires advanced vibration isolators that
can provide variable damping and stiffness. A solution to this problem can be provided by MR fluid based mounts. An
MR fluid mount is capable of changing its stiffness and damping characteristics to accommodate various input excitation
amplitudes and frequencies.
This paper presents simulated results for a mixed mode magnetorheological (MR) fluid mount. If the MR mount is only
working in one mode, either flow or squeeze mode, the range of isolation force provided by the damping and spring rate
of the mount is constrained by the geometry of the respective mode. However, when the mount operates in both modes
simultaneously, their effects are combined to accommodate a wider range of amplitudes and frequencies of excitation.
The mathematical governing equations of the mount are derived to account for its operation with mixed flow modes.
These equations implemented in MATLAB/Simulink<sup>(c)</sup>, with a specific set of parameters, predict the response of the
mount for various excitations. The simulated results indicate that the combination of modes is beneficial for the mount
performance in the low frequency range of operation.
This paper presents the results of vibration isolation analysis for the pump/motor component of hydraulic hybrid vehicles (HHVs). The HHVs are designed to combine gasoline/diesel engine and hydraulic power in order to improve the fuel efficiency and reduce the pollution. Electric hybrid technology is being applied to passenger cars with small and medium engines to improve the fuel economy. However, for heavy duty vehicles such as large SUVs, trucks, and buses, which require more power, the hydraulic hybridization is a more efficient choice. In function, the hydraulic hybrid subsystem improves the fuel efficiency of the vehicle by recovering some of the energy that is otherwise wasted in friction brakes. Since the operation of the main component of HHVs involves with rotating parts and moving fluid, noise and vibration are an issue that affects both passengers (ride comfort) as well as surrounding people (drive-by noise). This study looks into the possibility of reducing the transmitted noise and vibration from the hydraulic subsystem to the vehicle's chassis by using magnetorheological (MR) fluid mounts. To this end, the hydraulic subsystem is modeled as a six degree of freedom (6-DOF) rigid body. A 6-DOF isolation system, consisting of five mounts connected to the pump/motor at five different locations, is modeled and simulated. The mounts are designed by combining regular elastomer components with MR fluids. In the simulation, the real loading and working conditions of the hydraulic subsystem are considered and the effects of both shock and vibration are analyzed. The transmissibility of the isolation system is monitored in a wide range of frequencies. The geometry of the isolation system is considered in order to sustain the weight of the hydraulic system without affecting the design of the chassis and the effectiveness of the vibration isolating ability. The simulation results shows reduction in the transmitted vibration force for different working cycles of the regenerative system.