Babak Ebrahimi

Eddy current damper feasibility in automobile suspension: modeling, simulation and testing

This paper presents the modeling, simulation and testing of a novel eddy current damper (ECD) to be used in vehicle suspension systems. The conceived ECD utilizes permanent magnets (PMs), separated by iron poles that are screwed to an iron rod, and a conductive hollow cylinder to generate damping. Eddy currents develop in the conductor due to its relative motion with respect to the magnets. Since the eddy currents produce a repulsive force that is proportional to the velocity of the conductor, the moving magnet and conductor behave as a viscous damper. The structure of the new passive ECD is straightforward and does not require an external power supply or any other electronic devices. An accurate, analytical model of the system is obtained by applying electromagnetic theory to estimate the electromagnetic forces induced in the system. To optimize the design, simulations are conducted and the design parameters are evaluated. After a prototype ECD is fabricated, experiments are carried out to verify the accuracy of the theoretical model. The heat transfer analysis is established to ensure that the damper does not overheat, and the demagnetization effect is studied to confirm the ECD reliability. The eddy current model has 1.4?N RMS error in the damping force estimation, and a damping coefficient as high as 53?N?s?m?1 is achievable with the fabricated, scaled-down prototype. Finally, a full-size ECD is designed and its predicted performance is compared with that of commercial dampers, proving the applicability of the ECD in vehicle suspension systems.

A hybrid electromagnetic shock absorber for active vehicle suspension systems

The use of electromagnetic dampers (ED) in vehicle active suspension systems has drawn considerable attention in the past few years, attributed to the fact that active suspension systems have shown superior performance in improving ride comfort and road handling of terrain vehicles, compared with their passive and semi-active counterparts. Although demonstrating superb performance, active suspensions still have some shortcomings that must be overcome. They have high energy consumption, weight, and cost and are not fail-safe in case of a power breakdown. The novel hybrid ED, which is proposed in this paper, is a potential solution to the above-mentioned drawbacks of conventional active suspension systems. The proposed hybrid ED is designed to inherit the high-performance characteristics of an active ED with the reliability of a passive damper in a single package. The eddy current damping effect is utilised as a source of the passive damping. First, a prototype ED is designed and fabricated. The prototype ED is then utilised to experimentally establish the design requirements for a real-size active ED. This is accomplished by comparing its vibration isolation performance in a 1-DOF quarter-car test rig with that of a same-class semi-active damper. Then, after a real-size active ED is designed, the concept of hybrid damper is introduced to the damper design to address the drawbacks of the active ED. Finally, the finite-element method is used to accurately model and analyse the designed hybrid damper. It is demonstrated that by introducing the eddy current damping effect to the active part, a passive damping of approximately 1570 Ns/m is achieved. This amount of passive damping guarantees that the damper is fail-safe and reduces the power consumption more than 70%, compared with an active ED in an automotive active suspension system.

A novel eddy current damper: theory and experiment

A novel eddy current damper is developed and its damping characteristics are studied analytically and experimentally. The proposed eddy current damper consists of a conductor as an outer tube, and an array of axially magnetized ring-shaped permanent magnets separated by iron pole pieces as a mover. The relative movement of the magnets and the conductor causes the conductor to undergo motional eddy currents. Since the eddy currents produce a repulsive force that is proportional to the velocity of the conductor, the moving magnet and the conductor behave as a viscous damper. The eddy current generation causes the vibration to dissipate through the Joule heating generated in the conductor part.An accurate, analytical model of the system is obtained by applying electromagnetic theory to estimate the damping properties of the proposed eddy current damper. A prototype eddy current damper is fabricated, and experiments are carried out to verify the accuracy of the theoretical model. The experimental test bed consists of a one-degree-of-freedom vibration isolation system and is used for the frequency and transient time response analysis of the system. The eddy current damper model has a 0.1 m s−2 (4.8%) RMS error in the estimation of the mass acceleration. A damping coefficient as high as 53 Ns m−1 is achievable with the fabricated prototype.This novel eddy current damper is an oil-free, inexpensive damper that is applicable in various vibration isolation systems such as precision machinery, micro-mechanical suspension systems and structure vibration isolation.

A new pneumatic suspension system with independent stiffness and ride height tuning capabilities

This paper introduces a new pneumatic spring for vehicle suspension systems, allowing independent tuning of stiffness and ride height according to different vehicle operating conditions and driver preferences. The proposed pneumatic spring comprises a double-acting pneumatic cylinder, two accumulators and a tuning subsystem. This paper presents a detailed description of the pneumatic spring and its working principle. The mathematical model is established based on principles of thermo and fluid dynamics. An experimental setup has been designed and fabricated for testing and evaluating the proposed pneumatic spring. The analytical and experimental results confirm the capability of the new pneumatic spring system for independent tuning of stiffness and ride height. The mathematical model is verified and the capabilities of the pneumatic spring are further proved. It is concluded that this new pneumatic spring provides a more flexible suspension design alternative for meeting various conflicting suspension requirements for ride comfort and performance.

Feasibility study of an electromagnetic shock absorber with position sensing capability

This paper presents the feasibility study of an electromagnetic damper, as sensor/actuator, for vehicle suspension application. This electromagnetic damper is based on the concept of the tubular, linear, brushless DC motor, and operates in three modes: passive, semi-active, and active. As a self-powered active shock absorber, the proposed damper has the potential to function as a sensor and actuator simultaneously. Optimized geometry factors are selected to achieve higher electromagnetic forces and magnetic flux induced in the system, and the maximum achievable damping force is estimated based on analytical models, considering physical restrictions. The estimated damping force seems reasonable for vehicle suspension applications, even in the absence of external power.

Design of a hybrid electromagnetic/hydraulic damper for automotive suspension systems

Vehicle suspension systems have been extensively explored in the past decades, contributing to ride comfort, handling and safety improvements. The new generation of power-train and propulsion systems, as a new trend in modern vehicles, poses significant challenges to suspension system design. Consequently, novel suspension concepts are required, not only to improve the vehicles dynamic performance, but also to enhance the fuel economy by utilizing regeneration functions. However, the development of new-generation suspension systems necessitates advanced suspension components, such as springs and dampers. This paper presents the concept, design, and modeling of a novel hybrid electromagnetic/hydraulic damper for automotive suspension applications. This study indicates that the coupling of active/passive systems benefits the power consumption issue in active systems, while saving cost and weight. A potential hybrid damper design is proposed, where hydraulic damping effect is employed as a source of passive damping. The active part of the damper is designed to satisfy the required active force. The designed damper is analyzed under the steady-state conditions to determine the correlation between the passive damper performance and design parameters. It is demonstrated that a passive damping of ∼1700 Ns/m can be achieved, by the addition of the viscous fluid to the active damper, which guaranties a fail-safe damper in case of power failure.

Design of an Electromagnetic Shock Absorber

This paper presents the design, modeling, and Finite Element (FE) analysis of a novel Electromagnetic Damper (ED). This cost-effective, regenerative ED is based on the concept of the tubular, linear, brushless dc motor. The structure of the proposed passive ED is straightforward, and it does not require an external power supply. An analytical model of the system is obtained using the magnetic circuit method and used to optimize the non-dimensional geometry factors and to estimate the electromagnetic forces and flux induced in the system. The model can be used to design high-performance dampers for various applications. To confirm the design, dynamic FE simulations were conducted and compared with the analytical and experimental results.Copyright

Pneumatic suspension damping characterisation with equivalent damping ratio

The damping property of a pneumatic suspension with orifice-type fluidic resistance is characterized in this study. The nonlinear and linear models for the suspension system are first formulated and experimentally verified. The verified linear model is employed to derive a new pneumatic damping measure, equivalent damping ratio, based on which a pneumatic Damping Ratio Diagram (PDRD) is proposed. A systematic investigation on pneumatic suspension damping is then conducted. The results and analyses demonstrate that PDRD can be an effective tool for the calculation/design of pneumatic damping, where to properly choose pneumatic suspension design parameters can help yield desirable pneumatic damping.

Automotive Glass Exciter Technology for Acoustic Application

This paper discusses the modeling and analysis of a novel audio subwoofer system for automotive applications using the automobile windshield glass. The use of a piezo-electric actuator coupled with a mechanical amplifier linked to a large glass panel provides a highly efficient method of producing sound. The proposed subwoofer system has the advantage over existing conventional systems of not only reducing the weight of the automobile, but also a significant power savings resulting in an increase of expected fuel economy. Among various design challenges, the glass-sealing design is of huge importance, as it affects the system dynamic response and so the output sound characteristics. The main goal in this manuscript is to evaluate different glass-sealing design configurations by providing a comprehensive Finite Element model of the system. To do so, a comprehensive, yet simplified FE model is developed, and experimental studies are performed in the component level to fine-tune and verify the model. Harmonic response of the system for each sealing configuration design is obtained in the frequency range of 0–200 Hz, and the results are compared and discussed. The finite element model is also beneficial in preliminary design of other components as well as the exciter placement, and predicting the performance of the overall system.Copyright