Hydraulic Amplification Mechanism Research Articles

Principle and Control of Active Engine Mount Based on Magnetostrictive Actuator

Engine mount system affects the automobile NVH performance. Active mounts would achieve excellent vibration isolation and relative displacement control performance in a broad frequency bandwidth by outputting controlled force to the mounting system. The actuator and control method of the active mounts determine the system performance. In this paper, an active mount based on the smart material, i.e., Terfenol-D rod, is proposed, which mainly includes three parts: rubber spring, magnetostrictive actuator (MA), and hydraulic amplification mechanism (HAM). Dynamic model of the active mount is correspondingly established. A state feedback control method based on x-LMS (Least-Mean-Square) algorithm is proposed as well. Specifically, with the consideration of the unmeasurable state parameters in the active mounting system, an x-LMS state feedback controller with the system state as the reference signal is constructed by employing Sage-Husa Kalman filter to realize the state estimation of the active mounting system. Then a detailed analysis of the proposed control method is conducted, with deriving iterative formula of tap-weight vector. Sequentially, the problem of the dependence on the excitation signal in the x-LMS algorithm is addressed. The feasibility and capability of the proposed control method are verified and evaluated by simulation of a two-degree-of-freedom active mounting system.

Encoding and presentation of surface textures using a mechanotactile display

Tactile displays can present virtual tactile sensations to the user by stimulating tactile receptors, which are distributed spatially within the skin and are classified into four types based on their characteristic temporal pattern of impulses. The mechanotactile displays can stimulate different types of the receptors selectively by changing the displacement and frequency of the skin deformation. In our previous work, we developed an array of large-displacement microactuators composed of hydraulic amplification mechanism (HDAM) and piezoelectric actuators, which is capable of stimulating all the four types of the tactile receptors. We controlled the driving parameters that were the driving voltage, vibration frequency, and actuation patterns of the actuators, and successfully presented various surface textures. However, in practical applications, the control parameters are to be tuned according to the surface textures that we want to present. In addition, the input signals to the piezoelectric actuators would consist of multiple frequency components and are difficult to create through trial and errors. To solve this inverse problem, in this work, we encoded the sample surface textures to voltage signals by sliding the sample over the HDAM and using the piezoelectric actuators as sensors. First, we attempted to reproduce the surface textures. The encoded signals were amplified to drive the mechanotactile display. The perception tests indicated that this approach was effective. Secondly, we attempted to correlate the encoded signals with hardness of the samples. The encoded signals were investigated among the samples of different hardness. In addition, we fabricated moicropatterned tactile samples that have the same physical properties except Young’s modulus to isolate hardness from other parameters. The encoded signals were compared to extract the characteristic signals to determine the hardness. These signals were used to drive the tactile display in the perception tests, which verified the effectiveness of the approach. These two approaches that were proposed and experimentally verified in this paper are readily applicable to solve the inverse problem in tactile display applications.

A normally-closed piezoelectric micro-valve with flexible stopper

In the field of controlled drug delivery system, there are still many problems on those reported micro-valves, such as the small opening height, unsatisfactory particle tolerance and high cost. To solve the above problems, a novel normally-closed piezoelectric micro-valve is presented in this paper. The micro-valve was driven by circular unimorph piezoelectric vibrator and natural rubber membrane with high elasticity was used as the valve stopper. The small axial displacement of piezoelectric vibrator can be converted into a large stroke of valve stopper based on hydraulic amplification mechanism. The experiment indicates that maximum hydraulic amplification ratio is up to 14, and the cut-off pressure of the micro-valve is 39kPa in the case of no working voltage. The presented micro valve has a large flow control range (ranging from 0 to 8.75mL/min).

2A1-G29 Hydraulic Amplification Mechanism for Large Displacement Actuators Systems

We developed a hydraulic amplification mechanism (HDAM) for applications requiring large deformation. HDAM consists of a set of two largely deformable polydimethylsiloxane (PDMS) that are sharing a closed fluid chamber filled with glycerin, an incompressible fluid. Chamber's geometry with input and output surfaces having different cross-sectional areas creates amplification. By varying and studying influence of geometry on amplification performance, we achieved a mechanism offering displacement amplification up to 18-fold for static actuation. For tactile display application, by combining HDAM with piezoelectric actuators, we can amplify the input displacement generated and use the output displacement to stimulate tactile receptors. For such applications, dynamic characteristics are essential so we studied dynamic response of HDAM when combined with piezoelectric actuators.

A piezoelectric microvalve for compact high-frequency, high-differential pressure hydraulic micropumping systems

A piezoelectrically driven hydraulic amplification microvalve for use in compact high-performance hydraulic pumping systems was designed, fabricated, and experimentally characterized. High-frequency, high-force actuation capabilities were enabled through the incorporation of bulk piezoelectric material elements beneath a micromachined annular tethered-piston structure. Large valve stroke at the microscale was achieved with an hydraulic amplification mechanism that amplified (40×-50×) the limited stroke of the piezoelectric material into a significantly larger motion of a micromachined valve membrane with attached valve cap. These design features enabled the valve to meet simultaneously a set of high frequency (/spl ges/1 kHz), high pressure(/spl ges/300 kPa), and large stroke (20-30 μm) requirements not previously satisfied by other hydraulic flow regulation microvalves. This paper details the design, modeling, fabrication, assembly, and experimental characterization of this valve device. Fabrication challenges are detailed.