Variable Stiffness Suspension Research Articles

Design and Investigation of a Suspended Backpack With Wide-Range Variable Stiffness Suspension for Reducing Energetic Cost

Design and Investigation of a Suspended Backpack With Wide-Range Variable Stiffness Suspension for Reducing Energetic Cost

Vibration Analysis and Control of the Suspension System of the Drum Washing Machine by Applying SMA

The suspension system of the drum washing machine is the object of study. To reduce the vibration of drum washing machines during high-speed dehydration, a shape memory alloy is proposed to be used to make suspension spring. The spring stiffness can be controlled according to the characteristic that the elastic modulus of SMA varies with temperature to achieve damping effect. The mathematical model and multi-body dynamics simulation model are established for the suspension system of the drum washing machine, the vibration generation mechanism of the drum washing machine and the SMA active vibration control principle are analyzed, and the vibration control effect of the SMA suspension spring is studied for different speed simulations. The results show that the SMA variable stiffness suspension spring has a significant vibration control effect compared with the spring of general material.

Application Research on H∞ Controlled Variable Stiffness Suspension System of High-speed Train

Application Research on H∞ Controlled Variable Stiffness Suspension System of High-speed Train

Theoretical and experimental investigation of a stiffness-controllable suspension for railway vehicles to avoid resonance

In this paper, a semi-active suspension system, composed of variable stiffness (VS) magnetorheological (MR) dampers, was developed and investigated theoretically and experimentally, aiming to improve the ride comfort of high-speed train by avoiding the train body resonance. Firstly, a full-scaled high-speed train model with 17-degree-of-freedom (17-DOF), whose secondary lateral suspension was installed with two VS-MR dampers, was established. And the numerical evaluation on the performance of the VS suspension was conducted. Secondly, a scaled high-speed railway vehicle and the VS suspension were designed and manufactured for experimental evaluation on a vibration generating platform under different excitations. The experimental results are consistent with the numerical evaluation results, which show that the VS suspension can effectively avoid the train's resonance in lateral direction and greatly improve the ride comfort compared with the traditional suspension system.

Development and evaluation of a versatile semi-active suspension system for high-speed railway vehicles

Abstract With the increase in speed of high-speed trains, their vibration will become fiercer and fiercer, especially when the lateral resonance of the car body occurs. This paper develops a versatile semi-active suspension system with variable stiffness (VS) magnetorheological elastomer (MRE) isolators and variable damping (VD) magnetorheological (MR) dampers for high-speed trains, aiming to improve ride comfort by avoiding car body resonance and dissipating vibration energy. As the first step, a multifunction VSVD semi-active suspension system for high-speed railway vehicles was designed and prototyped, including four VS-MRE isolators and two VD-MR dampers. After that, a scaled train model, composing of a car body and a secondary lateral suspension system was designed and built to evaluate the performance of the new VSVD suspension system; a control strategy based on short-time Fourier transform (STFT) and sky-hook was proposed to control the new suspension system. Two different excitations, harmonic excitation and random excitation, were applied to evaluate the train’s VSVD suspension. As a comparison, four alternative suspension systems, including passive-off suspension, passive-on suspension, pure VS suspension, and pure VD suspension were also evaluated. The evaluation results verified that the VSVD suspension of the train can avoid lateral resonance of car body and dissipate the vibration energy efficiently. The comparison verified that the VSVD suspension system outperforms the passive-off suspension, passive-on suspension, pure VS suspension, and pure VD suspension.

Scalable Electroactive Polymer for Variable Stiffness Suspensions

We present an approach for creating a reliable variable stiffness suspension using prestretched electroactive polymer films. In comparison to other variable-stiffness devices, the design is compact, lightweight, consumes low energy, and can change its stiffness in approximately 10 ms. Attention to the main causes of failure increases the reliability of the device so that multiple layers can be combined for increased loads and stiffness. A device with 20 layers supports loads of over 15 N at minimum stiffness and maximum voltage for displacements of $\pm 7$ mm and up to 138 N at maximum stiffness with a displacement of 20 mm. Multilayer devices have demonstrated 3 million mechanical load cycles and hundreds of thousands of stiffness variation (charging and discharging) cycles, respectively.

Influence of Spring Ratio on Variable Stiffness and Damping Suspension System Performance

The variable stiffness and damping (VSVD) suspension system offers an interesting option to improve driver comfort in an energy efficient way. The aim of this study is to analyze the influence of the spring ratio on the VSVD. The realization of the VSVD is obtained by the application of variable damping with magnetorheological (MR) damper. In this study, the nonlinear damping force characteristic of the MR damper is modeled with the Bouc-Wen model and the road disturbance is modeled by a stationary random process with road displacement power spectral density. It is shown from simulation that VSVD has a potential benefit in improving performance of vehicle suspension.

A New Semiactive Variable Stiffness Suspension System Using Combined Skyhook and Nonlinear Energy Sink-Based Controllers

This paper presents the semiactive case of a variable stiffness suspension system. The central concept is based on a recently designed variable stiffness mechanism that consists of a horizontal strut and a vertical strut, both of which are semiactively controlled by magnetorheological (MR) dampers. The vertical MR damper force is designed to track a skyhook damper force, while the horizontal strut is used is to vary the load transfer ratio by semiactively controlling the location of the point of attachment of the vertical strut to the car body. The control algorithm, effected by the horizontal MR damper, uses the concept of a nonlinear energy sink (NES) to effectively transfer the vibrational energy in the sprung mass to a control mass, thereby reducing the transfer of energy from road disturbance to the car body. The analyses and simulation results show that a better performance can be achieved by subjecting the point of attachment of a suspension system, to the chassis, to the influence of a horizontal NES system.

Experimental study on the ride comfort of a crawler power chassis scale model based on the similitude theory

The ride comfort experimental assessment of crawler off-road vehicle is relatively overlooked, and is expensive and difficult to execute with higher and higher ride comfort performance requirements. To trade off between precise and cost, an experimental method based on the similitude theory is proposed. Under the guidance of the similitude theory, a 1:5 crawler power chassis scale model equipped with a kind of variable stiffness suspension system is used. The power spectrum density(PSD), the root mean square(RMS) of weighed acceleration, peak factor, average absorbed power(AAP) and vibration dose value(VDV) are selected as ride comfort evaluation indexes, and tests results are transformed via similarity indexes to predict the performance of full-scale power chassis. PSD shows that the low-order natural frequency of the vertical natural frequency(z axis) is 1.1 Hz, and the RMS, AAP and VDV values indicate the ride comfort performance of this kind of power chassis is between the “A little uncomfortable” and “Rather uncomfortable”. From the results, low-order vertical natural frequency, obtained by PSD, validates that the similarity relationship between two models is satisfied, and 1:5 scale model used in experiment meets the similarity relationship with the full-scale model; consequently, the ride comfort prophase evaluation with the 1:5 scale model is feasible. The attempt of applying the similitude theory to crawler vehicle ride comfort test study decreases the cost and improves the test feasibility with sufficient test precise.

Attitude control of full vehicle using variable stiffness suspension control

SUMMARY In this paper, the attitude of a ground vehicle travelling in cornering is controlled using a variable stiffness semi-active suspension control. The main goal of the variable stiffness semi-active suspension controller is to track as close as possible the performance of the full-active suspension control. The work is subdivided into two main parts. At first, making use of optimal control theory, the full-active suspension control of the full car is designed in various ways, depending on the choices of the state's variables. Afterwards, the variable stiffness control algorithm is derived based on the variable damping semi-active control concept, except that the variable damping is now replaced by the variable stiffness mechanism. Simulation results using various types of manoeuvre show that, when external body forces are applied to the vehicle, the variable stiffness control tracks the performance of the full-active control for high damping and stiffness coefficient, and for mild damping and stiffness coefficient, the performance of the variable stiffness control follows that of the skyhook controller. Copyright © 2014 John Wiley & Sons, Ltd.

Application Research of Virtual Prototype Technology in the Variable Stiffness Suspension Matching of Light Bus

In order to meet the ride comfort requirements of the light bus under no load and full-load condition,its rear suspension employs two-level variable stiffness leaf spring. For reasonably matching the two values of the variable stiffness and the damping force curve of the damper, one kind of virtual prototype technology was used. The virtual spring model of two-level variable stiffness was created in Adams-Chassis and the center-curve of the leaves was based at the free-state of the leaf spring. Then the front suspension, the rear suspension, the steering system, the powertrain & drineline system, the braking system, the wheels and bus body were respectively builded in Adams_Car, and they consituted the virtual assembly model of the light bus. So we could use the virtual model to conveniently test the performance of the ride comfort and handling stability under the no load and full-load state. Based on the ISO test standards, the virtual objective evaluation indexes were all calculated. According to these indexes, the two-level variable stiffness and the damping force curve were optimized. At last, the optimization results were verified by testing the optimized light bus. Experimental results shows that virtual optimization technology could play an important role in solving engineering problems.

Improving Vehicle Lateral Stability Based on Variable Stiffness and Damping Suspension System via MR Damper

The capability of a variable stiffness and damping (VSVD) suspension system via a magnetorheological (MR) damper on improving vehicle lateral stability is investigated in this paper. First, a type of the VSVD suspension system is briefly introduced with the application of variable damping to realize the capability of VSVD. Then, variable damping via the MR damper is extended, and the characteristics of damping force are presented with the Bouc-Wen model. Then, the proposed VSVD system is inserted into a full vehicle model as a front suspension system to control tire normal forces. A control strategy composed of a fuzzy controller that the output is wheel slip ratio and a simple on/off controller to model the application of VSVD is developed to illustrate its ability in improving vehicle stability. It is shown from simulation that VSVD can increase tire normal forces and make vehicles present better performance on lateral stability.

Roll stabilisation of road vehicles using a variable stiffness suspension system

A variable stiffness architecture is used in the suspension system to counteract the body roll moment, thereby enhancing the roll stability of the vehicle. The variation of stiffness concept uses the ‘reciprocal actuation’ to effectively transfer energy between a vertical traditional strut and a horizontal oscillating control mass, thereby improving the energy dissipation of the overall suspension. The lateral dynamics of the system is developed using a bicycle model. The accompanying roll dynamics are also developed and validated using experimental data. The positions of the left and right control masses are sequentially allocated to reduce the effective body roll and roll rate. Simulation results show that the resulting variable stiffness suspension system has more than 50% improvement in roll response over the traditional constant stiffness counterparts. The simulation scenarios examined is the fishhook manoeuvre.

A new active variable stiffness suspension system using a nonlinear energy sink-based controller

This paper presents the active case of a variable stiffness suspension system. The central concept is based on a recently designed variable stiffness mechanism which consists of a horizontal control strut and a vertical strut. The horizontal strut is used to vary the load transfer ratio by actively controlling the location of the point of attachment of the vertical strut to the car body. The control algorithm, effected by a hydraulic actuator, uses the concept of nonlinear energy sink (NES) to effectively transfer the vibrational energy in the sprung mass to a control mass, thereby reducing the transfer of energy from road disturbance to the car body at a relatively lower cost compared to the traditional active suspension using the skyhook concept. The analyses and simulation results show that a better performance can be achieved by subjecting the point of attachment of a suspension system, to the chassis, to the influence of a horizontal NES system.

Improving the capacity of tire normal force via variable stiffness and damping suspension system

Tire normal force of a vehicle equipped with a variable stiffness and damping (VSVD) suspension system is studied via numerical simulation in this paper. The main purpose of the paper is to illustrate the effects of VSVD suspension system on the capacity of tire normal force. Firstly, a modified suspension system and its variable stiffness and damping characteristics are presented based on a conventional suspension system. With the application of adjustable suspension system in vehicle, the effects of equivalent stiffness of suspension system on vehicle performance are analyzed by the term of load transfer at tires when cornering. By using a reference model, a simple on/off control strategy is developed to improve normal forces at tires and a fuzzy control strategy to model Direct Yaw moment Control (DYC) based on yaw rate is also developed to show the required longitudinal force. Finally, numerical simulations are carried out to demonstrate the important role of VSVD in improving tire normal force and then ameliorating vehicle lateral stability. It is shown from the results that the normal force at tires can be increased through the application of VSVD suspension system. It also indicates that DYC would be much efficient when implementing this system.

A new variable stiffness suspension system: passive case

Abstract. This paper presents the design, analysis, and experimental validation of the passive case of a variable stiffness suspension system. The central concept is based on a recently designed variable stiffness mechanism. It consists of a horizontal control strut and a vertical strut. The main idea is to vary the load transfer ratio by moving the location of the point of attachment of the vertical strut to the car body. This movement is controlled passively using the horizontal strut. The system is analyzed using an L2-gain analysis based on the concept of energy dissipation. The analyses, simulation, and experimental results show that the variable stiffness suspension achieves better performance than the constant stiffness counterpart. The performance criteria used are; ride comfort, characterized by the car body acceleration, suspension deflection, and road holding, characterized by tire deflection.

CJ89-56. Fuzzy multi-objects optimization in parameters of engine-mountings : By Pan Xufeng (Qinghua University, Beijing, China) et al. Chinese J. Mech. Engng25, No. 4 (Dec. 1989), pp. 61–67

In this paper, a semi-active suspension system, composed of variable stiffness (VS) magnetorheological (MR) dampers, was developed and investigated theoretically and experimentally, aiming to improve the ride comfort of high-speed train by avoiding the train body resonance. Firstly, a full-scaled high-speed train model with 17-degree-of-freedom (17-DOF), whose secondary lateral suspension was installed with two VS-MR dampers, was established. And the numerical evaluation on the performance of the VS suspension was conducted. Secondly, a scaled high-speed railway vehicle and the VS suspension were designed and manufactured for experimental evaluation on a vibration generating platform under different excitations. The experimental results are consistent with the numerical evaluation results, which show that the VS suspension can effectively avoid the train's resonance in lateral direction and greatly improve the ride comfort compared with the traditional suspension system.