Control Of Hydraulic Actuator Biology Essay

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ABSTRACT: By employing MR fluids as working fluid in power systems, direct interface can be realized between magnetic field and fluid power without the need for mechanical moving parts like spool in Directional control valves. In this study, we got to know the technology of fluid, its components, and the principle of work, and specifications. We got to know as well as the designs that make use of this liquid. The important thing is to design valves, actuators and systems as well as dealing with these valves. The new design of compact (4/3) Directional Control valve controlled proportionally with magnetic field (variable current) is possible. We think we can do the development work of the valves to work proportionally to control the hydraulic actuators. , Through a compact design and conduct experiments, and theoretical calculations to reach the optimal design. Reviews and has given us a clear idea of this technology.

Key words: Magnetorheological (MR) fluid, (MR) Valve design, (MR) Device, Hydraulic System.

INTODUCTION

Magnetorheological (MR) fluid consist of stable suspension of micro-sized, magnetic particles dispersed in carrier medium like a hydrocarbon fluid, silicon oil or water. When an external magnetic field is applied, the polarization induced in suspended particles which results in Magnetorheological effect of the MR fluid. The Magnetorheological effect is direct influences on the mechanical properties of the MR fluid. The suspended particles in the MR fluid become magnetized and align themselves, like chains, with the direction of the magnetic field. The formulation of these particle chains restricts the movement of the MR fluid, thereby increasing the yield stress of the fluids. The force of attraction between the particles in the chains manifests as a resistance to shear deformation and consequently, fluid flow. In an idealized MR fluid, the fluid does not start flowing till a particular value of shear stress, called the yield stress, has been reached. Thus, the viscosity of these fluids can be changed using an external magnetic field.

As anyone who has made MR fluid knows, it is not difficult to make a strong MR fluid. Over fifty years ago both Rabinow and Winslow (Carlson, 2001) described basic MR fluid formulations that were every bit as strong as fluids today. A typical MR fluid used by Rabinow consisted of 9 parts by weight of carbonyl iron to one part of silicone oil, petroleum oil or kerosene. To this suspension he would optionally add grease to improve settling stability. The strength of Rabinow's MR fluid can be estimated from the result of a simple demonstration that he performed.

Rabinow was able to suspend the weight of a young woman from a simple direct shear MR fluid device.

He described the device as having a total shear area of 8 square inches and the weight of the woman as 117 pounds. For this demonstration to be successful it was thus necessary for the MR fluid to have yield strength of at least 100 kPa. .

This unique property of MR fluids has been used in various commercial applications. MR fluids have been used in optical polishing, (Kordonski et al. ,1999), fluid clutches ,(Lee et al., 2000; Takesue et al.,2001), vibration isolation systems and a variety of aerospace ,(Kamath et al., 1999); (Marathe et al., 1998) , civil (Sodeyama et al., 2001); (Ribakov and Gluck, 2002) and automotive ,(Lam et al, 2003); (Lindler et al., 2003) damping applications The important rheological characteristics of an MR fluid are its yield force, viscosity and settling rate ,(Kordonski et al. 1998; Phule et al 1998 ;Rosenfeld et al. 2002) . The yield force and viscosity of an MR fluid can be continuously varied using appropriate magnetic fields. Using this property, control schemes can be implemented in devices using MR fluids.

Designs that take advantage of controllable fluids are potentially simpler and more reliable than conventional electromechanical devices. In addition, the MR fluid is one of the most efficient means to interface mechanical components with electronic controls (Mechatronics), offering fast switching speed, miniaturization, and continuously variable control.

Controllable fluid has received a great deal of attention over the past decade, because they offer the promise of valve with no moving parts and low-cost direction control valves, and miniature.

LITERATURE REVIEW

A literature survey has been done to investigate the past research relating to this work. The area of Magnetorheological fluids, devices of Magnetorheological, Magnetorheological valve design, test & Model for the Magnetorheological systems are of primary interest.

Magnetorheoological fluids

It is essential to know the work done by researchers in the study MR fluids, and for the purpose of knowledge of the properties and specifications of this MR fluid and their possible use.

(Bossis, et al. 2002) have presented the basic phenomena related to the interplay between inter particle magnetic forces which are responsible for the gelation of the suspension and hydrodynamic forces which will break this gel and will allow the suspension to flow. They had given some analytical predictions for the yield stress and emphasize how the combination of field and flow can give rise to a very rich rheology with hysteresis and shear-induced phase separation.

(Zipser, et al. 2001) have described the flow behavior of Magnetorheologic fluids in narrow channels, influenced by variable magnetic fields and temperature. Furthermore, they had studied possibilities and limits of applying Magnetorheologic fluids in smart actuators.

(Olabi, and Grunwald, 2007) have presented the state of the art of an actuator with a control arrangement based on MR fluid technology. They had showed the excellent features like fast response, simple interface between electrical power input and the mechanical power output, and controllability make MR fluid the next technology of choice for many applications.

(Laun, et al. 2008) have done the measurements of the first and second normal stress difference in steady shear of a 50 vol. % MR fluid. The analysis was based on a comparison of plate-plate and cone-plate results. Since the radial profiles of true magnetic flux density in the sample could not be expected to be identical for both geometries, they have carefully analyzed the flux density profiles both by Hall probe measurements and Maxwell 2D FEM simulations. In addition, they had addressed the normal stresses effect on the concentricity in coaxial cylinder geometry.

(Brigadnov, and Dorfmann, 2005) have presented the material constitutive relations for a non-Newtonian incompressible MR fluid. They had considered the full system of equations as well as the Clausius-Duhem inequality for moving isotropic MR fluids in an electro-magnetic field. To illustrate the validity of the constitutive relations, the flow of a MR fluid between two parallel fixed plates under the influence of a constant magnetic field perpendicular to the flow direction was considered.

Literatures above, were identified on the MR fluid, composition, mechanical specifications, and Magnetic specifications. As well as, how do to be treatment with its. Also been identified on the relations between the specifications change, with the magnetic field of its. It has also been identified on the mathematical method of calculating the variables, and the use of appropriate software.

Devices of Magnetorheological

In this section we will look at some researches for devices, working with the MR fluid. MR fluid damper and Brake are devices to give its function by the shear stress of MR fluid.

(Hitchcock, et al. 2007) have presented theoretical and experimental investigations of a novel external bypass, fail-safe, Magnetorheological (MR) fluid damper. A fail-safe (MR) fluid damper was referred to as a device that retains a minimum required damping capacity in the event of a power supply or electronic system failure. They had developed theoretical formulation based on the Herschel-Bulkley constitutive model for an annular flow. Experimental results had obtained to demonstrate the validity of the theoretical analysis.

(Kelso, 2001) has illustrated the development of a fast-response for MR damper, low-power, cost-effective solution. Fundamentally, a competitive 'whole approach' active or semi-active MR solution can be viewed as system of separate components: parameter sensing, intelligent control, power delivery, and MR hardware technology. He had presented that is MR technology, comprising simple, commercial-off-the-shelf (COTS) components where possible, presents an attractive, practical and cost effective component of the 'whole approach' MR solution.

(Yang, et al. 2005) have investigated theoretically the fundamental design method of the MR damper. They had developed theoretical method to analyze the shear stress by the MR fluid within the damper. An engineering expression for the shear stress was derived to provide the theoretical foundations in the design of the damper. Based on this equation, be algebraically manipulated, the volume and thickness of the annular MR fluid within the damper was yielded.

(Milecki, 2001) described and studied a semi-active controllable fluid damper. He had proposed a simulation model of a damper and made some control analysis. He had presented the experimental results in a damper whose characteristics may by adapted in real time to the user's requirements. Such dampers could used to eliminate oscillations in different servo drive machine tools systems.

(Gravatt, 2003) has focused in his MSc. thesis on another application of MR dampers, involving super-sport motorcycles. He had discussed the method of designing and manufacturing MR dampers. The laboratory testing has been covered, including the test equipment, test procedure, and the laboratory test results. The results of field tests with stock dampers and MR dampers with a variety of control systems were discussed.

(Sukhwani and Hirani, 2008) have described the design procedure of MR brake and discuss the effect of MR gap on its braking torque. They have performed the theoretical design and its findings, prototyping, and experimental study of MR brake. An experimental test setup has been developed to measure the braking torque under various operating speeds (200 to 1200 r/min) and control currents (0.0 to 1.2 A). The effects of central and side electromagnets on braking torque have been examined.

(Karakoc, et al. 2008) have discussed the design considerations for building an automotive Magnetorheological (MR) brake. They were considered practical design criteria such as material selection, sealing, working surface area, viscous torque generation, applied current density, and MR fluid selection to select a basic automotive MR brake configuration. Then, a finite element analysis was performed to analyze the resulting magnetic circuit and heat distribution within the MR brake configuration. They had followed by a multidisciplinary design optimization (MDO) procedure to obtain optimal design parameters that can generate the maximum braking torque in the brake.

(Park, et al. 2006; 2008) developed and studied a Magnetorheological brake system for the automotive which has been performed advantages over the conventional hydraulic brake system.

(Zhang et al. 2006) have proposed the magnetic design of an MR damper, and have discussed a finite element analysis (FEA) on the magnetic saturation for the utmost improvement of the high force. Through experimental verification, the damper force was effectively scaled by the magnetic design.

Literatures above have been identified on devices which used MR fluid, Types and design of its. We got to know also the method of calculating the variables, experimentally design and theoretical. As well as using the software.

Magnetorheological valve design

In this section we will look at some research for valves, working with the MR fluid. Including pressure control valve and flow control valve. These valves are very important in control system, for this reason the researchers focused on develop it.

(Yokota, et al. 1999) proposed and fabricated a pressure control valve using MR fluid. The valve consists of a flow channel between a pair of magnetic poles and the differential pressure was controlled by the applied magnetic field intensity. It features simple, compact and reliable structure without moving parts. The static characteristics experiments found that the differential pressure was controlled by the applied magnetic field intensity under little influence of the flow rate, which corresponds to pressure control valve. The differential pressure and output power change of 0.68MPa and 20W were obtained with the input current and power change 710A.turns and 1.9W at the flow rate of 30cm3/s(1.8L/min).

(Songjing, et al. 2002) have developed a new type MR fluid relief valve. The construction and working of new type valve were introduced. Its steady-state performance was simulated and experimented.

(Yoo and Wereley 2002) have designed the miniature MR valve with the maximum performance of the MR effect in fluid mechanics. The performance of the MR valve was limited by saturation phenomenon in magnetic circuit and by the finite yield stress of MR fluid. Design parameters of the MR valve were studied and an optimal performance was designed using steel (Permalloy) material in the magnetic circuit. A maximum magnetic flux density at the gap was achieved in the optimized valve design based on a constraint on the outer diameter limitation. Valve performance was verified with simulation. A flow mode bypass damper system was fabricated and used experimentally and validated valve performance.

(Li, et al. 2003) have optimized the design of a high-efficiency Magnetorheological (MR) valve using finite element analysis. The MR valve was composed of a core, a wound coil, and a cylinder-shaped flux return. The core and flux return form the annulus through which the MR fluid flows. The effects of magnetic field formation mechanism and MR effect formation mechanism on the MR valve performance were investigated. Analytical results of the magnetic flux density in the valve indicate that the saturation in the magnetic flux may be in the core, the flux return, or the valve length. To prevent the saturation as well as to minimize the valve weight, the dimensions of the valve were optimally determined using finite element analysis. In addition, this analysis was coupled with the typical Bingham plastic analysis to predict the MR valve performance.

(Ai, et al. 2006) have designed of an MR valve possessing simultaneously annular fluid resistance channels and radial flow resistance channels. They have described the structure and working of it, and a mathematical had developed. The simulation results show that the efficiency of the MR valve could be improved significantly with two types of fluid flow resistance gaps.

(Nguyen, et al. 2007) have presented the geometric optimal design of MR valves in order to improve valve performance, such as pressure drop. They had investigated the pressure drops on the basis of the Bingham model of an MR fluid. Then, the valve ratio, which was an objective function, was derived by considering the field-dependent (controllable) and viscous (uncontrollable) pressure drops of the MR valves.

(Nguyen, et al. 2008) have presented an optimal design for MR valves for minimizing the control energy to be applied to coils to control the pressure drop of the valves. The optimization problem identifies parameters such as applied current, coil wire size and geometric dimensions of the valves which satisfy the specified pressure drop and inductive time constant requirements.

Literatures above have been identified on kinds of valves used in MR fluid technology and its design, as well as its applications. It also identified the valve design experimentally and theoretical, in addition to the software used in the design.

Test & Model for the Magnetorheological systems

In this section we will look at some research for systems which are using MR fluid. These systems are controlled by MR valves as well as in Hydraulic systems.

(Yoo and wereley, 2004) have implemented four MR valves as Wheatstone bridge hydraulic power circuits to drive a hydraulic actuator using a gear pump for driving a conventional hydraulic actuator. If a change in direction is required, the flow through each of the valves in the Wheatstone bridge could be controlled smoothly via changing the applied magnetic field. They had studied the behavior and performance of the MR valve in terms of nondimensional parameters. The performance of the hydraulic actuator system with a Wheatstone bridge network of MR valves was derived using three different constitutive models of the MR fluid: an idealized model (infinite yield stress), a Bingham plastic model, and a biviscous model. The analytical system efficiency in each case was compared to experiment.

(Yoo, et al. 2005) have described a prototype MR-piezo hybrid actuator that combines the piezo pump and MR valve actuator concepts, resulting in a self-contained hydraulic actuation device without active electromechanical valves. They had designed and constructed of a prototype MR-piezo hybrid actuator. They had tested and described the performance and efficiency of the system experimentally.

(John, et al. 2008) have configured the MR valves in the form of an H-bridge to produce di-direction motion in an output cylinder by alternately applying magnetic field in two opposite arms of the bridge. The primary actuation was performed using a compact terfenol-D rod driven pump and frequency rectification of the rod motion was done using passive reed valves. The pump and reed valve configuration along with MR valves form a compact hydraulic actuation system. Actuator design, analysis and experimental results were presented. A time domain model of the actuator was developed and validated using experimental data.

Literature above gave us an idea of the systems and hydraulic actuators using MR fluid technology. It is clear that the researchers began to develop ideas and the development of systems to reach the optimal design.

CONCLUSIONS

After exploring the literature and studied in depth. We conclude the idea of the work of the MR fluid. We got to know as well as the types and designs that work with MR fluid technology. The thing that concerns us is to design the valve, which works with MR fluid technology, in addition to the systems and hydraulic actuators.

We conclude that the literature does not mention one of the researchers to develop a compact directional hydraulic valve works proportionally to control the hydraulic actuator, using the MR fluid technology. That is why we are developing a design that the valve, making the idea of proportional directional control valve using MR fluid.

The new design of compact (4/3) Directional Control valve controlled proportionally with magnetic field (variable current) is possible. We think we can do the development work of the valves to work proportionally to control the hydraulic actuators. , Through a compact design and conduct experiments, and theoretical calculations to reach the optimal design. Reviews and has given us a clear idea of this technology. This is our research.

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