A mathematical modelling and experimental study of annular-radial type magnetorheological damper

An experimental study was undertaken to evaluate the mathematical modelling of the magnetorheological (MR) damper featuring annular radial gap on its valve. The experiment was conducted using a fatigue dynamic test machine under particular excitation frequency and amplitude to get force-velocity and force-displament characteristics. Meanwhile, the mathematical modelling was done using quasi-steady modelling approach. Simulation using adaptive neuro fuzzy inference (ANFIS) Algorithm (Gaussian and Generalized Bell) were also carried out to portray the damping force-displacement modelling that is used to compare with the experimental results. The experimental characteristics show that amplitudes excitation and current input affect the result damping force value. The comparison of the experimental and mathematical results presented in this paper shows a significant difference in damping force value and that the quasi-steady modelling could not significantly approach the damping force-velocity results. Moreover, the semi-active damper is compared to the passive damper. The results show that a semi-active damper performs better than a passive damper because it only requires a little power. Based on the damping force-displacement modelling, it can be seen that Gaussian has a higher accuracy rather than Generalized Bell. Discussion on the energy dissipation and equivalent damping coefficient were also accomodated in this paper. Having completed in mathematical modelling and simulation, the damper would be ready for further work in-vehicle application that is development of control system.

A smart passive MR damper with a hybrid powering system for impact mitigation: An experimental study

This paper presents a smart passive MR damper with fast-responsive characteristics for impact mitigation. The hybrid powering system of the MR damper, composed of batteries and self-powering component, enables the damping of the MR damper to be negatively proportional to the impact velocity, which is called rate-dependent softening effect. This effect can keep the damping force as the maximum allowable constant force under different impact speed and thus improve the efficiency of the shock energy mitigation. The structure, prototype and working principle of the new MR damper are presented firstly. Then a vibration platform was used to characterize the dynamic property and the self-powering capability of the new MR damper. The impact mitigation performance of the new MR damper was evaluated using a drop hammer and compared with a passive damper. The comparison results demonstrate that the damping force generated by the new MR damper can be constant over a large range of impact velocity while the passive damper cannot. The special characteristics of the new MR damper can improve its energy dissipation efficiency over a wide range of impact speed and keep occupants and mechanical structures safe.

Design of a Prosthetic Ankle Complex

Nature has, over a large span of geological time, engineered near perfect solutions to most problems humans face today. Motion of the limbs is one such area, and the cutting edge in the development of effective prostheses is biomimetics. Limb prostheses have been used by mankind for the better part of known history, and most of the technology currently available in prosthetics is not exclusively new. However, modern prosthetics either are uncomfortable—and the lack of flexion affects the gait of the patient—or too expensive for a large segment of the populace. This chapter seeks to study the mimicry of physiological systems through the design for an ankle prosthesis that includes a passive damper and mimics the shape and behavior of the natural ankle joint.

Intelligent Control Based on a Neural Network for Aircraft Landing Gear with a Magnetorheological Damper in Different Landing Scenarios

A typical oleo-pneumatic shock-absorbing strut (classic traditional passive damper) in aircraft landing gear has a metering pin extending through the orifice, which can vary the orifice area with the compression and extension of the damper strut. Because the metering pin is designed in a single landing condition, the traditional passive damper cannot adjust its damping force in multiple landing conditions. Magnetorheological (MR) dampers have been receiving significant attention as an alternative to traditional passive dampers. An MR damper, which is a typical semi-active suspension system, can control the damping force created by MR fluid under the magnetic field. Thus, it can be controlled by electric current. This paper adopts a neural network controller trained by two different methods, which are genetic algorithm and policy gradient estimation, for aircraft landing gear with an MR damper that considers different landing scenarios. The controller learns from a large number of trials, and accordingly, the main advantage is that it runs autonomously without requiring system knowledge. Moreover, comparative numerical simulations are executed with a passive damper and adaptive hybrid controller under various aircraft masses and sink speeds for verifying the effectiveness of the proposed controller. The main simulation results show that the proposed controller exhibits comparable performance to the adaptive hybrid controller without any needs for the online estimation of landing conditions.

Enhancing Friction Pendulum Isolation Systems Using Passive and Semi-Active Dampers

Friction pendulum systems (FPSs) are a common solution for isolating civil engineering structures under ground movements. The result is a base-isolated structure in which the base exhibits low shear stiffness in such a way that the input energy of the earthquake is concentrated and dissipated into it, leaving the superstructure free of damage. As a consequence, large displacements of the FPS may be demanded depending on the earthquake intensity and the fundamental period of the FPS. To accommodate these displacements, large-size isolators with high friction coefficients are usually required. However, the FPS will then exhibit poor re-centering capacity and the risk of future shocks will increase due to previous residual displacements, especially for low-intensity earthquakes. An alternative solution is to include a semi-active damper to the FPS, keeping the friction coefficient low and achieving both, limited base displacement under high-intensity earthquakes and good re-centering capacity under low-intensity ones. Thus, this work presents a design methodology for base isolators formed by an FPS with a damper added. The design methodology is applied to an FPS with a passive damper and to an FPS with a semi-active damper. Two ON-OFF control strategies are studied: (i) a fairly simple phase control, and (ii), a mechanical energy-predictive based algorithm. The advantages of semi-active FPSs with low friction coefficients with respect to FPS with high friction coefficients are demonstrated. The results with the designed semi-active FPS are compared with the single FPS and the FPS with a passive damper. Finally, the use of semi-active FPS allows us to enhance the FPS performance as the isolator size can be reduced while keeping the capacity to cope with low and high-intensity earthquakes without residual displacements.

Robust Adaptive Control for an Aircraft Landing Gear Equipped with a Magnetorheological Damper

A landing gear of an aircraft is required to function at touchdown in different landing scenarios with parametric uncertainties. A typical passive damper in a landing gear has limited performance in differing landing scenarios, which can be overcome with magnetorheological (MR) dampers. An MR damper is a semi-active system that can adjust damping force by changing the amount of electric current applied to it. This paper proposes a new robust controller based on model reference sliding mode control and adaptive hybrid control to improve the efficiency of absorbing landing impact energy, not only considering the variables of aircraft weight and sink speed but also managing uncertainties, such as ambient temperature and passive damping coefficient. To verify the effectiveness of the proposed controller, comparative numerical simulations were performed with a passive damper, a skyhook controller, and the proposed controller under various landing scenarios. The simulation results show that the proposed controller improves the total energy absorber efficiency by up to 10% higher than that of the skyhook controller. In addition, the proposed controller is demonstrated to have better adaptability and robustness than the other control algorithms in the differing landing scenarios and parametric uncertainties.