Active Shock Absorber Research Articles

Suppression of horizontal vibrations in high-speed elevators using active shock absorber to assist traditional damping systems

PurposeThis paper aims to design an active shock absorber scheme for use in conjunction with a passive shock absorber to suppress the horizontal vibration of elevator cars in a smaller range and shorter time. The developed active shock absorber will also improve the safety and comfort of passengers driving in ultra-high-speed elevators.Design/methodology/approachA six-degree of freedom dynamic model is established according to the position and condition of the car. Then the active shock absorber and disturbance compensation-based adaptive control scheme are designed and simulated in MATLAB/Simulink. The results are analysed and compared with the traditional shock absorber.FindingsThe results show that, compared with traditional spring-based passive damping systems, the designed active shock absorber can reduce vibration displacement by 60%, peak acceleration by 50% and oscillation time by 2/3 and is more robust to different spring stiffness, damping coefficient and load.Originality/valueThe developed active shock absorber and its control algorithm can significantly reduce vibration amplitude and converged time. It can also adjust the damping strength according to the actual load of the elevator car, which is more suitable for high-speed elevators.

Research on the Stability of Vehicle Active Shock Absorber Based on Intelligent Control System

The traditional vehicle suspension vibration reduction design method uses a fixed damping coefficient to reduce the vibration of the elastic element, and does not consider the different vibration intensity caused by different road conditions and vehicle speeds, and the vibration reduction effect is poor. A finite element design method for vehicle suspension shock absorption optimization is proposed to analyse the function and structure of vehicle suspension shock absorbers. We use the first-order optimization method in the ANSYS finite element software to carry out the optimal design of vehicle suspension damping, and take the damping force of the suspension shock absorber as the optimization objective to carry out the finite element optimization design of the vehicle suspension damping. This ensures that the vibration of the vehicle body is rapidly attenuated, so that the body can quickly reach a stable state. The results show that the fuzzy control strategy can greatly suppress the acceleration of the vehicle body and the dynamic load of the tire, reduce the dynamic travel of the suspension, and the ride comfort, driving safety and operation stability of the vehicle have been significantly improved, and the system suspension has a good comprehensive performance.

Active Shock Absorber Control Based on Time-Delay Neural Network

A controlled suspension usually consists of a high-level and a low-level controller. The purpose the high-level controller is to analyze external data on vehicle conditions and make decisions on the required value of the force on the shock absorber rod, while the purpose of the low-level controller is to ensure the implementation of the desired force value by controlling the actuators. Many works have focused on the design of high-level controllers of active suspensions, in which it is considered that the shock absorber can instantly and absolutely accurately implement a given control input. However, active shock absorbers are complex systems that have hysteresis. In addition, electro-pneumatic and hydraulic elements are often used in the design, which have a long response time and often low accuracy. The application of methods of control theory in such systems is often difficult due to the complexity of constructing their mathematical models. In this article, the authors propose an effective low-level controller for an active shock absorber based on a time-delay neural network. Neural networks in this case show good learning ability. The low-level controller is implemented in a simplified suspension model and the simulation results are presented for a number of typical cases.

Spring-Based Active Shock Absorber Systems with Piezoelectric Energy Harvesters.

In this research, energy harvesters with different types of spring-based shock absorbers were invested for the active shock absorber applications. Two different types of spring-based shock absorbers were prepared for the comparison, coil type spring-based shock absorbers and specially designed slice type spring-based shock absorbers. Shock absorbers have been widely employed to protect the complicated main system by cancelling the applied mechanical forces from outsides. Therefore, in the classical points of view, shock absorber can be prepared by the elastic materials to store and release the applied mechanical energy with sequentially in the form of elastic energy, thermal energy, and sound energy. However, in recently, there are strong demands to replace this classical shock absorber to the energy harvesters, which can collect the wasted energy in the form of electrical energy. Therefore, in this research, alternative two different types of spring-based advanced shock absorber will be presented and discussed. To combine with the spring-based shock absorber, multilayered piezoelectric energy harvesters were attached to collect the applied mechanical energy.

Improved design of an active landing gear for a passenger aircraft using multi-objective optimization technique

One of the major subsystems of each airplane is the landing gear system which must be capable of tolerating extreme forces applied to structure during ground maneuver to improve vibration absorbing performance. The traditional landing gear system performs this function well under normal condition, whereas with varying condition of landing and situation of the runway for the airplane, performance of this system decreases noticeably. In this research, for overcoming this problem, the coefficients of controller, the parameters of hydraulic nonlinear actuator added to the traditional shock absorber system, and the vibration absorber are optimized simultaneously by the bee intelligent multi-objective algorithm. As well as, for proving adaptability of this algorithm, this paper presents the sensitivity analysis of three point landing due to the additional payload and the touchdown speed and the robustness analysis of one and two point landings due to the wind conditions as emergency situation on the runway as an innovated work. In order to evaluate the effectiveness and the efficiency of proposed method, the flight dynamic differential equations of an Airbus 320–200 vibrational model during the landing phase are derived and through the numeric technique are solved. The results of numerical analysis for this large-scale airplane model with six degrees of freedom demonstrate that the active shock absorber system in accordance with two types of the bee multi-objective algorithm has good performance in comparison with the passive approach to minimize the bounce displacement and momentum, the pitch displacement and momentum, the suspension travel and impact force in time-domain and frequency-domain by using signal processing, that results in improvement of passenger ride comfort importantly. As well as, enhancement of structure’s fatigue life is a likely case as a consequence of study applicable to the industry.

Intelligent control of active shock absorber for high-speed elevator car

Due to the influencing factors, such as irregularity of guide, piston wind excitation in the hoistway, and uncertain swinging of hoisting rope during the operation of high-speed traction elevator, car will produce dramatic horizontal vibration. With the purpose of suppressing this vibration effectively, the active car shock absorber is designed with linear motor, and a five-degrees-of-freedom space vibration model of the car is established and, subsequently, its state space equation is derived. For the uncertainty external excitation in the car system, the back propagation neural network proportional–integral–derivative controller with linear prediction model is designed for the intelligent active control of the vibration of the car, and simulation analysis is carried out with MATLAB/Simulink. The result shows that the active shock absorber designed in this study can effectively suppress the horizontal vibration of high-speed elevator car, better than traditional proportional–integral–derivative controller. This study has opened up a new idea of high-speed elevator vibration damping method, and is of important referential significance for the field of active control of car vibration.

One-Quarter-Car Active SuspensionModel Verification

Suspension system influences both the comfort and safety of the passengers. In the paper, energy recuperation and management in automotive suspension systems with linear electric motors that are controlled by a designed H∞ controller to generate a variable mechanical force for a car damper is presented. Vehicle shock absorbers in which forces are generated in response to feedback signals by active elements obviously offer increased design flexibility compared to the conventional suspensions with passive elements (springs and dampers). The main advantage of the proposed solution that uses a linear AC motor is the possibility to generate desired forces acting between the unsprung (wheel) and sprung (one-quarter of the car body mass) masses of the car, providing good insulation of the car sprung mass from the road surface roughness and load disturbances. As shown in the paper, under certain circumstances linear motors as actuators enable to transform mechanical energy of the vertical car vibrations to electrical energy, accumulate it, and use it when needed. Energy flow control enables to reduce or even eliminate the demands on the external power source. In particular, the paper is focused on experiments with active shock absorber that has been taken on the designed test bed and the way we developed an appropriate input signal for the test bed that as real road disturbance acts upon the vibration absorber and the obtained results are evaluated at the end. Another important point the active suspension design should satisfy is energy supply control that is made via standard controller modification, and which allows changing amount of energy required by the system. Functionality of the designed controller modification was verified taking various experiments on the experiment stand as mentioned in the paper.

주파수 감응식 쇽업소버와 수동형 쇽업소버의 성능비교 분석

Various forms of passive shock absorber have developed to supplement performance which is poorer than that of active shock absorber. It is called 'Hybrid Conventional Damper (HCD)'. Frequency sensing shock absorber that this study will cover belongs to the HCD. This study aims to demonstrate that performance of frequency sensing shock absorber is superior than that of passive shock absorber. Study process is as follows. Firstly, analysis models for both passive shock absorber and frequency sensing shock absorber are developed to secure reliability. Then, elements which cause difference of ride quality are found out through comparison of hysteresis characteristics. By comparison of frequency characteristic, furthermore, damping principle of frequency sensing shock absorber is understood. Also, it determines if the absorber performs well even though maximum excitation speed is changed. Finally, the study proves that performance of frequency sensing shock absorber is superior than that of passive shock absorber after comparing change of damping power in excitation condition that various frequencies are mixed.

Characteristics of ferro fluid

This paper focuses on the synthesis and characterization of ferro fluid (smart fluid). The colloidal mixtures of magnetite in carrier fluid were made by different chemical processes. The characteristics like particle size, turbidity, density, viscosity, and damping were studied. The average particle size after repeated filtering measured to 12 nm. The turbidity variation was found to be almost negligible. The damping coefficient varied from 0.2418 Ns/m to 0.8348Ns/m in the magnetic field. The effect of magnetic field on viscosity was studied on in house made viscometer and calibrated with the existing Redwood viscometer. It was possible to change the viscosity with the change in magnetic field. Such smart fluid could be used in a semi active shock absorber of a vehicle for better performance. Keywords: Ferro fluid, viscosity, magnetic field, Smart fluid.

Characteristics of ferro fluid

This paper focuses on the synthesis and characterization of ferro fluid (smart fluid). The colloidal mixtures of magnetite in carrier fluid were made by different chemical processes. The characteristics like particle size, turbidity, density, viscosity, and damping were studied. The average particle size after repeated filtering measured to 12 nm. The turbidity variation was found to be almost negligible. The damping coefficient varied from 0.2418 Ns/m to 0.8348Ns/m in the magnetic field. The effect of magnetic field on viscosity was studied on in house made viscometer and calibrated with the existing Redwood viscometer. It was possible to change the viscosity with the change in magnetic field. Such smart fluid could be used in a semi active shock absorber of a vehicle for better performance.

Testing of Semiactive Landing Gear Control for a General Aviation Aircraft

The operating possibilities of semiactive control of landing gears aimed at application to general aviation aircraft are evaluated. Compared to fully active systems, this kind of control is simple, lightweight, and safe, its intervention being based on the modification of the oil orifice section only. This active control was designed by using a landing simulation code that allowed a reliable prediction of its effectiveness. The application of the active shock absorber to a nonflying prototype has been both numerically and experimentally investigated, by means of drop tests at different sink speeds. The setup, the control strategy, and the obtained results are described, and the measured responses are compared to simulation results. Good agreement between analytical and experimental results confirms that a heuristic tuning of the active control can be effective when adequate simulation tools are used in the design.