Study on the Effects of Magnetic Field on Magnetorheological Fluid Hydraulic Retarder Braking Torque
Abstract In order to ensure driving safety, heavy vehicles are often equipped with hydraulic retarder, which provides sustained, stable braking torque and converts the vehicle kinetic energy into heat taken away by the cooling system when traveling on a long downhill. The conventional hydraulic retarder braking torque is modulated by adjusting the liquid filling rate, which leads to slow response and difficult control. In this paper, a new kind of magnetorheological (MR) fluid hydraulic retarder is designed by replacing the traditional transmission oil with MR fluid and arranging the excitation coils outside the working chamber. The braking torque can be controlled by the fluid viscosity of MR fluid with the variation of magnetic field. Compared with the traditional hydraulic retarder, the system has the advantages of fast response, easy control and high adjustment sensitivity.
Effect of Temperature on Braking Efficiency Stability of Magnetorheological Fluid Auxiliary Braking Devices
Abstract Fluid auxiliary braking devices can provide braking torque through hydraulic damping, fluid auxiliary braking devices can also convert vehicular inertia energy into transmission fluid heat energy during the braking, which can effectively alleviate the work pressure of the main brake. Traditional hydraulic auxiliary braking devices use transmission fluids to transmit torque, however, there is a certain lag effect during the braking. The magnetorheological fluid (MR fluid) can also be used to transmit torque because it has the advantages of controlling braking torque linearly and responding fast to the magnetic field changed. The temperature of MR fluid will increase when the vehicle is engaged in continuous braking. MR fluid temperature changes will cause a bad influence on the efficiency stability of auxiliary braking.
A new controllable limited slip differential is proposed and tested in software environment. It is characterized by the employment of a magnetorheological fluid, which presents the property of changing its rheology thanks to an applied magnetic field. A vehicle model has been designed and employed for the synthesis of a sliding controller. The control is based on a double level scheme: the upper controller aims to generate the target locking torque, while the lower controller generates, as control action, the supply current for the controllable limited slip differential. The obtained results show the effectiveness of the device in terms of vehicle dynamics improvement. Indeed, the results reached by the vehicle in presence of the new differential confirm the improved performances for both steady and unsteady state manoeuvres.
Abstract Stringent emission norms introduced by the legislators over the decades has forced automotive manufacturers to improve the fuel economy and emission levels of their engines continuously. Therefore, the emission levels of modern engines are significantly lower than pre-1990 engines. However, the improvement in fuel economy is marginal when compared to that of emission levels. For example, approximately 30% of total energy in the fuel is being wasted through the cooling systems in the modern engines. Therefore, thermal management systems are being developed to reduce these losses and offer new opportunities for improving the fuel economy of the vehicles. One of the new emerging technologies for thermal management is the use of nanofluids as coolant. Nanofluids are a mixture of nano-sized particles added to a base fluid to improve its thermal characteristics.
Abstract In recent years, Magneto-rheological (MR) fluid has drawn a lot of attention for its applications in a variety of torque transmission devices, such as brakes, clutches and soft starters of mechanical equipment. Compared with the conventional clutch of vehicle, the novel MR clutch has the advantages of fast response with electronic signal, accuracy control and simple structure without mechanical wear in plates. Besides, MR clutch may be helpful to fast response of vehicle in some situation. Nowadays, most applications of MR fluids in the torque transmission field mainly are used in low-power situation. As far as we know, the proposed effective methods enhancing the output torque of MR devices will increase either the number of fluid gaps or the magnetic field in the MR fluid. This article presents a novel vehicle clutch utilizing magnetorheological fluid and multiple-disc structure.
Design, Testing and Analysis of a Novel Multiple-Disc Magnetorheological Braking Applied in Vehicles
Abstract This paper presents a new magnetorheological braking which can be used in vehicles. Magneto-rheological (MR) fluid is a novel material which can be used in different components of vehicle. Magneto-rheological fluids (MRF) are suspensions of micron size whose yield stress varies rapidly as the change of magnetic field. The use of MRF in vehicles has been gaining popular recently due to its strong rheological effect, fast response and low energy consumption. Besides, these performances give designers more choice in automotive designs. However, most of the related research of MRF brake is about the construction of small prototype to verify its rheological performance. As a result, research progress is limited to calculation and simulation which make the braking force of prototype can hardly meet the requirement of vehicle due to a lack of optimal design and the understanding of MRF in the situation of high sheer stress and magnetic field.
Vibration Control of MR-Damped Vehicle Suspension System Using PID Controller Tuned by Particle Swarm Optimization
Abstract Proportional integral derivative (PID) control technique is the most common control algorithm applied in various engineering applications. Also, particle swarm optimization (PSO) is extensively applied in various optimization problems. This paper introduces an investigation into the use of a PSO algorithm to tune the PID controller for a semi-active vehicle suspension system incorporating magnetorheological (MR) damper to improve the ride comfort and vehicle stability. The proposed suspension system consists of a system controller that determine the desired damping force using a PID controller tuned using PSO, and a continuous state damper controller that estimate the command voltage that is required to track the desired damping force. The PSO technique is applied to solve the nonlinear optimization problem to find the PID controller gains by identifying the optimal problem solution through cooperation and competition among the individuals of a swarm.
Abstract In order to improve structure and performance of magneto-rheological dual mass flywheel (MRF-DMF), some parameters effects on dynamic characteristics are acquired by parameters analysis. The dynamic stiffness and loss angle in different current and different frequency are gained through dynamic characteristic test. The fluid-structure interaction finite element model of MRF-DMF is built and the accuracy is verified by comparison between test and simulation. Based on the model, the parameters analysis is done and the law of MRF viscosity, arc spring stiffness, working clearance, rotor radius and axial width effect on dynamic characteristics are gained, it will prove some guidance for the structure and performance improvement.
Control Research of Power Train Torsional Vibration Based on Magneto-Rheological Fluid Dual Mass Flywheel
Abstract To research the torsional vibration damping characteristic of magneto-rheological fluid dual mass flywheel (MRF-DMF) and the control system in power train, the multi-degree power train torsional vibration model which contains MRF-DMF and semi-active fuzzy control model are built, then the damping characteristic of MRF-DMF in several conditions are gained and compared with MRF-DMF when no control system. The result indicates: the damping characteristic of MRF-DMF effect on power train when using control is better than without control in idle, speed up, slow down, ignition and stalling, while the damping characteristic is less obvious in constant speed because the simulation condition and damping moment relatively stable.
Abstract Magneto-rheological (MR) fluid is a type of smart material which has ability to change its flow resistance on the application of magnetic field. This property of changing viscosity of the fluid due to application of magnetic field is utilized in the MR brake. MR brake typically consists of multiple rotating disks immersed in MR fluid and an enclosed electromagnet. The controllable yield stress produces shear friction on the rotating disks, generating the braking torque. Of late MR brakes have been explored for automotive applications. Literature review reveals that the torque output of MR brake is not sufficient for braking of mid-sized car. Hence, it is worthwhile to investigate its application for a two-wheeler where the braking torque requirement is low. This paper presents design and simulation of MR brake performance for its torque output.
Abstract In the field of massive and complex manufacturing we are now in need of materials, with properties, that can be manipulated according to our needs. Smart materials are one among those unique materials, which can change their shape or size simply by adding a little bit of heat, or can change from a liquid to a solid almost instantly when near a magnet. These materials include piezoelectric materials, magnetorheostatic materials, electrorheostatic materials, and shape memory alloys (SMA's). Shape memory alloys (SMA's) are metals, which exhibit two very unique properties, pseudo-elasticity (an almost rubber-like flexibility), and the shape memory effect (ability to be severely deformed and then return to its original shape simply by heating). The two unique properties described above are made possible through a solid state phase change that is a molecular rearrangement, in which the molecules remain closely packed so that the substance remains a solid.
The paper presents a new electromechanical brake system for vehicles using magnetorheological fluid. The brake system designed for the electric vehicle has some advantages over the conventional brake system. The brake system is made up of a brake disk, shells, magnetorheological fluid (MRF) and the electromagnets. The brake disk is immersed in the MRF whose yield stress changes as the applied magnetic field. The braking torque of this system can be linearly adjusted by the current in just a few milliseconds without the conventional vacuum booster. This system has a quick response and precise control performance with a low hysteresis. Besides, the system has adopted the original complicated structure to save space and cost. In this paper, the configuration of MRF brake types is described. The braking torques of the MRF brakes is derived based on the MRF theoretical model which is firstly raised. Some braking simulation based on the theoretical model is also shown.
Smart Lockwire: A Shape Memory Alloy Lockwire for Improved Reliability in Bolted Fixing in Automotive and Aeronautical Applications
Shape memory alloys (SMA) have a unique behavior due to a reversible phase transformation between two solid crystalline structures: martensite (low temperature and low stiffness phase) and austenite (high temperature and a higher stiffness phase). This transformation can occur either as a result of temperature change or mechanical stress load, both above characteristic critical values of these materials. Due to the reversible nature of this phenomenon, direct transformation occurs when austenite transforms into martensite and reverse transformation when martensite transforms into austenite. The latter is induced by raising the temperature and it is this process that occurs during the generation of significant associated forces through the undergone deformation recovering of the material, being of fundamental importance for the use as actuators.
Chassis performance greatly influences driving in the turn inn movement. Spec of the active damper is simulated to achieve a chassis that satisfies various requirements. In this paper, an MR-damper (Magneto-Rheological fluid damper), which is high-response active damper, is chosen. The MR-damper is mounted in FSAE vehicles and controlled vehicle behavior electronically in a simulator. As a result, the MR-damper brought a big effect to pitch action rather than roll action, and an initial damping force effected vehicle behavior more than damping force change ratio.
Effect of Cylinder Diameter of Monotube-Type MR-Damper on the Damping Force Changing Ratio and the Response Time
MR-damper (Magneto-Rheological fluid damper) is used an actuator with high speed in response to control the movement of four-wheel vehicles. In this paper, performances of two MR-dampers were measured. These dampers had difference in diameter of cylinder, length of piston and orifice. These changes will influence the damping force, the damping force change ratio and the response time of damping force change. As a result, a larger damper showed 1.4 times damping force change ratio of smaller one and shorter response time in compression.
Magneto-rhelological(MR) dampers are devices that use rheological fluids to modify the mechanical properties of fluid absorber. The mechanical simplicity, high dynamic range, large force capacity, lower power requirements, robustness and safe manner of operation have made MR dampers attractive devices for semi-active real-time control in civil, aerospace and automotive applications. Landing gear is one of the most essential components of the aircraft, which plays an extreme important role in preventing the airframe from vibration and excessive impact forces, improving passenger comfortable characteristics and increasing aircraft flight safety. In this paper, the semi-active system used in landing gear damping controller design, simulation, and the vibration test-bed are discussed and researched. The MR dampers employed in landing gear system were designed, manufactured and characterized as available semi-active actuators.
Piezoelectric materials are smart materials that can undergo mechanical deformation when electrically or thermally activated. An electric voltage is generated on the surfaces when a piezoelectric material is subjected to a mechanical stress. This is referred to as the ‘direct effect’ and finds application as sensors. The external geometric form of this material changes when it is subjected to an applied voltage, known as ‘converse effect’ and has been employed in the actuator technology. Such piezoelectric actuators generate enormous forces and make highly precise movements that are extremely rapid, usually in the micrometer range. The current work is focused towards the realization and hence application of the actuator technology based on piezoelectric actuation. Finite element simulations are performed on different types of piezoelectric actuations to understand the working principle of various actuators.
Magneto-rheological fluid squeeze mode investigations at CVeSS have shown that MR fluids show large force capabilities in squeeze mode. A novel MR squeeze mount was designed and built at CVeSS, and a dynamic mathematical model was developed, which considered the inertial effect and was validated by the test data. A variant engine mount that will be used for isolating vibration, based on the MR squeeze mode is proposed in the paper. The mathematical governing equations of the mount are derived to account for its operation with MR squeeze mode. The design method of a robust H✓ controller is addressed for the squeeze mount subject to parameter uncertainties in the damping and stiffness. The controller parameter can be derived from the solution of bilinear matrix inequalities (BMIs). The displacement transmissibility is constrained to be no more than 1.05 with this robust H✓ controller. The MR squeeze mount has a very large range of force used to isolate the vibration.
Smart material is a suitable candidate for adaptive airfoil design as it can be customized to generate a specific response to a combination of inputs. Shape memory alloy (SMA) in particular is lightweight, produces high force and large deflection which makes it a suitable candidate for actuator in the adaptive airfoil design. By attaching SMA wires inside the airfoil, they can be activated to alter the shape of the airfoil. Placement of the actuator is crucial in obtaining the desired change of the airfoil camber. This paper proposed a design for the morphing wing aimed at changing the camber of the airfoil during cruise in order to increase the lift-to-drag ratio. Finite Element Method (FEM) analysis predicted the deformed airfoil geometry when the SMA wires were fully actuated. Numerical results are presented along with issues related to the fabrication of the morphing wing and implementation of the SMA actuator.
The Anatomy of Smart Materials and Structures and Their Influence on Design Practices in Automotive Engineering
This paper presents an exposition on the embryonic eclectic field of smart materials and structures, prior to discussing how this class of biomimetic materials will influence design practices in the field of automotive engineering. The development of smart structures typically involves the macroscopic synthesis of materials with both functional and structural properties by exploiting biomimetic philosophies. The most innovative class of these macroscopically adaptive materials typically feature combinations of actuators, sensors, and microprocessing capabilities which enable these materials to actively change their mass, stiffness and energy-dissipation characteristics in real-time. Such capabilities are particularly relevant to the numerous automotive systems that must operate under variable service conditions and in unstructured environments.