Magnetorheological Seat Suspension Research Articles

Performance evaluation of a novel semi-active absorption and isolation co-control strategy with magnetorheological seat suspension for commercial vehicle

Abstract Vibration isolation performance of seat suspension plays a critical role in protection of drive’s physical health as the last barrier. In this paper, the integrated magnetorheological (MR) dynamic tuned mass damper (TMD) is firstly designed and utilized into seat suspension. A semi-active co-control algorithm with MR damper and MR TMD is designed, analyzed and validated by comparative experiments. The dynamic models of two MR devices have been tested and fitted. Comparing with simulation and experimental results under various excitations and control conditions, this co-control algorithm with MR TMD is validated to be highly effective. The transmissibility at resonance frequency reaches to 0.81 which is less than 1. This phenomenon has hardly been investigated in seat suspension. It illustrates that resonance has been suppressed and improved significantly. The peak acceleration decreases to 1.19 m s−2 with a reduction of 57.2%, in contrast to passive condition with MR damper. The comfort index is increased by 45.6% under random excitation than passive condition. According to these comparisons, the vibration isolation property and comfort of seat suspension can be further improved by the proposed co-control algorithm with two MR devices.

A Novel Application of Magnetorheological Seat Suspension with an Improved Tuning Control Strategy

During the operation of commercial vehicles, drivers are usually exposed to long-term vibrations and acquire several health problems. Moreover, the end-stop impacts caused by large-magnitude vibrations or shocks may affect driving performance and result in injuries. A study of magnetorheological (MR) seat suspension controlled by a novel tuning control strategy is conducted in this research to reduce vibrations and avoid end-stop impacts. First, the MR damper’s characteristics are tested, and a mathematical model of MR seat suspension is established. Then, an improved tuning control strategy is designed based on this model. The proposed strategy has three control stages that can be adjusted according to the suspension stroke to improve seat comfort or avoid end-stop impacts. Each part of the control strategy is designed separately, and the vibration attenuation performance of this seat suspension is evaluated with a simulation for three excitations, i.e., harmonic excitation, bump excitation, and random road excitation. Finally, an experiment is conducted to verify the conclusion of the simulation. The seat suspension with the proposed control shows good performances on vibration attenuation and end-stop impact reduction. Compared with a passive seat, the vibration level is reduced by around 27% and end-stop impact is avoided when semiactive suspension with the proposed strategy is used. It also shows the best overall performance among the three experimental algorithms. Both the simulation and the experiment results indicate that the vibration attenuation performance of the seat suspension can be greatly improved with the improved tuning control strategy.

Gray skyhook predictive control of magnetorheological semi-active seat suspension with time delay

Semi-active seat suspension with a magnetorheological (MR) damper has been a popular study issue in recent years. Since the response time delay of the MR damper can reduce the control effect and even make the vibration more severe, there is an urgent need to compensate for the response time delay. In this paper, gray prediction is introduced into the vibration control study of commercial vehicle seat suspension. A gray skyhook prediction controller is designed to compensate for the response time delay. This proposed controller does not rely heavily on controller parameter optimization and requires fewer state variables than other typical time delay compensation controllers. The mechanical property of the MR damper has been tested, modeled, and analyzed. A seat suspension dynamic model considering geometric nonlinearity is established based on the motion relationship between the components of the suspension. Subsequently, the effect of the response time delay on seat suspension vibration control has been verified by simulation. The results show that the control effect deteriorates significantly after considering the response time delay. Finally, prediction accuracy and vibration reduction performance of the designed gray skyhook predictive controller are verified by simulation and bench testing. The results illustrate that the gray skyhook predictive controller provides excellent time delay compensation and can significantly improve the ride comfort and handling stability of the driver. This study provides a reference for vibration control research of the MR seat suspension.

Robustness control for nonlinear systems based on homogeneous prescribed sliding mode control

This paper presents a new homogeneous control using dual sliding mode control, and robustness control using linear matrix inequality (LMI) constraints. The controller is applied for the severe disturbance. A sliding surface function, which relates to an exponential function and itself t-norm, is applied to save the energy consumption of the control system. The constraints related LMI are proposed with the matrices and vectors of the systems following the chosen matrices in control the energy for control. Solution of the constraints is also presented with new approach to save the time of calculation. In addition, the proof for the proposed controller is also presented by using the candidate Lyapunov function. In the input control function, the t-norm type is embedded to improve its performance in control disturbance. Besides of the t-norm, the modified sliding surface in the input control is also improve the energy for controlling. The combination of these robustness control elements would bring a new view for the design of control. The advantages of the controller are demonstrated via computer simulation for a seat suspension system. A magneto-rheological fluid seat suspension with its random disturbances is used. To prove the flexibility of the controller, the proposed approach is compared with an existing controller. The compared control has the same structure as shown in the proposed model. However, its design has a disadvantage in control the severe disturbance. The comparison between two controls is a clear view of distinct improvement. The results of simulations show that the controller provides better performance and stability of the system. The stability is also analyzed through the variation of the input control and power spectral density related energy consumption.

Experimental Study of a Variable Stiffness Seat Suspension Installed With a Compact Rotary MR Damper

Traditional MR seat suspension without stiffness control is not able to avoid the resonance between the excitation and the seat, though it can dampen the vibration energy. To solve this problem, this paper proposed a variable stiffness (VS) magnetorheological (MR) damper to implement an advanced seat suspension. Its natural frequency can be shifted away from the excitation frequency through the variations of stiffness, thereby realizing the non-resonance control. The new seat suspension is designed and prototyped first, and then its dynamic property under different energizing current, excitation amplitude, and excitation frequency was tested using an MTS machine. The testing results verified its stiffness controllability. The vibration attenuation performance of the seat suspension was also evaluated on a vibration shaking table. The vibration reduction performance of the seat suspension was evaluated under two kinds of excitations, i.e., harmonic excitation and random excitation; the experimental results indicate that the new seat suspension outperforms passive seat suspensions regarding their ride comfort.

Simulation and experiment of the magnetorheological seat suspension with a seated occupant in both shock and vibration occasions

The aim of the present work is to develop an magnetorheological (MR) seat suspension for military vehicles to mitigate dynamic responses of seated occupant in both shock and vibration occasions. The main components of the MR seat suspension are tested and modelled. Subsequently, a mathematical model incorporating the MR seat and a seated occupant is established. The vibration and shock simulations based on the established model are carried out, and the results indicate that the proposed MR seat suspension can significantly alleviate the acceleration responses of the seated occupant under vibration input, and simultaneously possess the ability of reducing the spinal injury risk in the presence of severe impact. The systematic experiments of the MR seat prototype with a 50th percentile male hybrid III dummy are conducted, it is found out that the experimental results are in good agreement with the theoretical simulation results, which demonstrates that the developed MR seat suspension is provided with favourable vibration reduction performance and impact resistance.

A novel scissor-type magnetorheological seat suspension system with self-sustainability

A novel scissor-type magnetorheological seat suspension with self-sustainability which integrated self-powered, self-sensing, and self-adaptability is proposed in this study. The adaptive rotary damping system consisted of the rotary magnetorheological damper, and rotary permanent magnet direct current generator is designed to realize the self-sustainability. Effects of damping force and isolation object mass are analyzed for further designing and testing based on the dynamic model. The rotary magnetorheological damper and the electrical part are designed and analyzed theoretically. Series of experimental tests are conducted to verify the feasibility and control performances. The experimental results show that the on–off balance control algorithm based on the self-sensing signals can improve the comfort than the directly and supply-with-rectifier control modes.

A novel adaptive controller featuring inversely fuzzified values with application to vibration control of magneto-rheological seat suspension system

This work presents a novel adaptive fuzzy controller based on the inversely fuzzified values associated with the H infinity technique and it is applied to vibration control of a vehicle seat suspension system installed with a magneto-rheological damper. In this work, the fuzzified values are embedded into the Riccati-like equation to achieve enhanced robustness of control function and the sliding surface function of sliding mode control is used for designing the main control function. The synthetic function of controller includes a model of online interval type 2 fuzzy neural network system and a fast calculation for clustering. The combination between the fuzzy model system and the proposed control algorithm can shorten the calculation time and improve control responses of the system in the presence of disturbances and uncertainties. After formulating the controller, the effectiveness is validated through both simulation and experiment. In computer simulation, three different road profiles of random bump, regular bump, and random step wave are adopted to emulate severe external disturbances. It is shown from the simulation that both displacement and acceleration of the driver are remarkably well controlled under three different road conditions. This advantage is also validated in the experimental work. It is demonstrated that vibration control performances under random step wave road are much better than the comparative adaptive fuzzy controller. It is identified from the results that the use of the inversely fuzzified values plays a major role to enhance the robustness and hence better control responses in the presence of the disturbances.

Development of an MR seat suspension with self-powered generation capability

This paper proposes a self-powered magnetorheological (MR) seat suspension on the basis of a rotary MR damper and an electromagnetic induction device. By applying the self-powering component to the MR seat suspension, the operation cost of the semi-active seat is much cheaper because no external energy is required to control the MR damper. In this paper, the structure, design and analysis of the seat suspension were presented following the introduction section. The property tests of the self-powered seat suspension were conducted using an MTS machine. A robust control algorithm was developed to control the self-powered MR seat suspension and the vibration attenuation performance of the seat suspension was tested under two different vibration excitations, i.e. harmonic excitation and random excitation. The testing result verifies that the self-powered MR seat suspension under proper control can improve the ride comfort for passengers and drivers.

An adaptive fuzzy sliding mode control of magneto-rheological seat suspension with human body model

This article presents the control performances of a vehicle seat suspension system equipped with magneto-rheological dampers using a new adaptive fuzzy sliding mode controller. A magneto-rheological damper is designed by applying the Bingham model incorporating with the field-dependent rheological properties of magneto-rheological fluid. On the other hand, a seat suspension model is established by integrating with a 4-degree-of-freedom human body model. Then, the governing equations are then derived considering the vertical motion of the seat. Subsequently, an adaptive fuzzy controller is formulated by considering the acceleration of the seat. This controller is combined with the sliding mode controller to ensure the robustness against model uncertainty and external disturbances. The controller is then evaluated through experiment. It is demonstrated that the proposed seat suspension system realized by the proposed adaptive fuzzy sliding mode controller can provide very effective ride comfort performances by reducing vertical acceleration under regular bump, random signal, and sinusoidal excitations.

Multi-objective genetic algorithm fractional-order PID controller for semi-active magnetorheologically damped seat suspension

Recently, fractional-order proportional–integral–derivative (FOPID) controllers are demonstrated as a general form of the classical proportional–integral–derivative (PID) using fractional calculus. In FOPID controller, the orders of the derivative and integral portions are not integers which offer more flexibility in succeeding control objectives. This paper proposes a multi-objective genetic algorithm (MOGA) to optimize the FOPID controller gains to enhance the ride comfort of heavy vehicles. The usage of magnetorheological (MR) damper in seat suspension system provides considerable benefits in this area. The proposed semi-active control algorithm consists of a system controller that determines the desired damping force using a FOPID controller tuned using a MOGA, and a continuous state damper controller that calculates the input voltage to the damper coil. A mathematical model of a six degrees–of–freedom seat suspension system incorporating human body model using an MR damper is derived and simulated using Matlab/Simulink software. The proposed semi–active MR seat suspension is compared to the classical PID, optimum PID tuned using genetic algorithm (GA) and passive seat suspension systems for predetermined chassis displacement. System performance criteria are examined in both time and frequency domains, in order to verify the success of the proposed FOPID algorithm. The simulation results prove that the proposed FOPID controller of MR seat suspension offers a superior performance of the ride comfort over the integer controllers.

Ride comfort enhancement of heavy vehicles using magnetorheological seat suspension

This paper investigates the application of a controlled MR damper for a semi-active seat suspension for heavy vehicles, enabling more appropriate control algorithm. The proposed control system consists of a system controller that calculates the desired damping force using a proportional integral derivative (PID) controller tuned using genetic algorithm (GA), and a continuous state damper controller that estimates the command voltage that is required to track the desired damping force. The controlled semi-active seat suspension is compared to a passive seat suspension for predetermined base displacements. These inputs are calculated separately from the vibration of the body mass of a passive quarter-vehicle suspension. System performance criteria are evaluated in both time and frequency domains, in order to verify the effectiveness of the proposed semi-active control algorithm. The generated results show that the proposed genetic PID controller of MR seat suspension offers a considerable enhancement of the ride comfort.

Semi-active control of magneto-rheological variable stiffness and damping seat suspension with human-body model

The potential benefits of an MR seat suspension in improving ride quality are investigated. Two magneto-rheological (MR) dampers are devised and manufactured to realise the variable damping and equivalent stiffness capacities of a seat suspension, respectively. After evaluating fi eld-dependent damping characteristics of the MR seat damper, the equation of equivalent variable stiffness is also shown. A seat suspension model with a four-DOF human body model is then formulated. A Human Simulated Intelligent Controller (HSIC) is proposed to attenuate the unwanted vibration of the variable stiffness and damping seat suspension. To validate the control performance of the proposed seat suspension and the control scheme, a numerical simulation is performed under the bump, random and chirp excitations. The result indicates that the proposed seat suspension system with HSIC can significantly improve the driver’s ride quality compared to the passive one.

Adaptive magnetorheological seat suspension for the expeditionary fighting vehicle

The Expeditionary Fighting Vehicle (EFV) is an amphibious vehicle designed to operate through harsh conditions and at much higher speeds than its predecessors. These unique capabilities and broadly varying operational conditions lead to a complex design and human factors scenario for the forward seating positions that cannot be solved using conventional passive seat suspension systems. Injurious shock loads transmitted to the occupants when traversing over water in high sea states and/or at high speeds, as well as harmful shock and vibration transmitted to the occupants when the vehicle is travelling over land, pose a threat to occupant health and significantly limit mission duration. In this study, a semi-active magnetorheological (MR) seat suspension is developed which adapts to broadly varying operational conditions, as well as occupant weight, to provide optimal protection of EFV occupants. It is shown that this MR seat suspension system will reduce the shock and vibration transmitted to the occupant by up to 33% and 65%, respectively, as compared to the existing passive suspension.

Semi-Active Magnetorheological Helicopter Crew Seat Suspension for Vibration Isolation

This study explores the use of magnetorheological dampers in a semi-active seat suspension system for helicopter crew seats to enhance occupant comfort. Key concepts in designing a magnetorheological seat suspension system to isolate the occupant from rotorcraft vibration are identified. Using these design concepts, a magnetorheological damper is designed, fabricated, and retrofitted into a tactical SH-60 Seahawk crew seat. This magnetorheological damper is implemented in series with the existing fixed load energy absorbers such that the crashworthiness capability of the seat is not impaired. Semi-active control is implemented and performance is evaluated both analytically and experimentally. Experimental test results have shown that this system reduced the dominant rotor-induced vertical vibration (4 per rev) transmitted to a 50th percentile male aviator by 76%, which is a 61-70% improvement over the unmodified SH-60 crew seat depending upon whether a soft seat cushion is used. Furthermore, these experimental tests also show that this system significantly reduces vertically induced seat rocking that occurs as a result of an offset center of gravity in the crew seat design.

Analysis and Strategy for Superharmonics With Semiactive Suspension Control Systems

This paper focuses on an experimental implementation of a semiactive seat suspension using magnetorheological (MR) dampers. We first introduce the nonlinear dynamics phenomena induced by skyhook control. Skyhook control has been widely applied to applications ranging from structural vibration suppression to commercialized vehicle suspensions. Unfortunately, skyhook control generates superharmonic dynamics; yet, this issue has not been clearly addressed in such vibration control systems. This paper will attempt to explain how superharmonics are created with skyhook controls through analysis of test data. Furthermore, a nonlinear model-based adaptive control algorithm is developed and evaluated for reducing the negative impact of the superharmonics. Based on an empirical MR damper model, the adaptive algorithm is expanded mathematically, and the system stability is discussed. Then in the following sections, this paper describes implementation procedures such as modeling simplification and validation, and testing results. Through the laboratory testing, the adaptive suspension is compared to two passive suspensions: hard-damping (stiff) suspension with a maximum current of 1A to the MR damper and low-damping (soft) suspension with a low current of 0A, while broadband random excitations are applied with respect to the seat suspension resonant frequency in order to test the adaptability of the adaptive control. In two separate studies, both mass and spring rate are assumed known and unknown in order to investigate the capability of the adaptive algorithm with the simplified model. Finally, the comparison of test results is presented to show the effectiveness and feasibility of the proposed adaptive algorithm to eliminate the superharmonics from the MR seat suspension response.

Biodynamic Response Mitigation to Shock Loads Using Magnetorheological Helicopter Crew Seat Suspensions

Biodynamic response mitigation of both sinusoidal vibration and shock loads using a magnetorheological (MR) seat suspension is investigated. In doing so, an MR seat suspension model for helicopters, with a detailed lumped parameter model of a human body, was developed. The lumped parameter model of the human body consists of four parts: pelvis, upper torso, viscera, and head. From the model, the governing equation of motion of the MR seat suspension considering the human body was derived. Based on this equation, a semi-active nonlinear optimal control algorithm appropriate for the MR seat suspension was developed. The simulated control performance of the MR seat suspension was evaluated under both sinusoidal vibration and shock loads due to a vertical crash landing of a helicopter. In addition, the mitigation of injuries to humans due to such shock loads was also evaluated and compared with that of the passive seat suspension using a passive hydraulic damper.

Mitigation of biodynamic response to vibratory and blast-induced shock loads using magnetorheological seat suspensions

The mitigation of biodynamic response to vibratory and blast-induced shock loads using a magnetorheological (MR) seat suspension is addressed in this study. To this end, an MR seat suspension model for military vehicles including seated personnel is constructed in terms of a detailed lumped parameter model. The lumped parameter model of the human body consists of four parts: pelvis, upper torso, viscera, and head. From the model, the governing equation of motion of the MR seat suspension considering the human body is derived. Based on this equation, a semi-active nonlinear optimal control algorithm appropriate for the MR seat suspension is developed. The simulated control performance of the MR seat suspension is evaluated under three different excitations of sinusoidal and random vibration and tremendous shock load due to a mine explosion. In addition, the mitigation of injuries to humans due to such a shock load is evaluated and compared with a passive hydraulic seat suspension and a passive MR seat suspension with a constant yield force.

An Adaptive Semiactive Control Algorithm for Magnetorheological Suspension Systems

In this paper, we will present a nonlinear-model-based adaptive semiactive control algorithm developed for magnetorheological (MR) suspension systems exposed to broadband nonstationary random vibration sources that are assumed to be unknown or not measurable. If there exist unknown and∕or varying parameters of the dynamic system such as mass and stiffness, then the adaptive algorithm can include on-line system identification such as a recursive least-squares method. Based on a nonparametric MR damper model, the adaptive system stability is proved by converting the hysteresis inherent with MR dampers to a memoryless nonlinearity with sector conditions. The convergence of the adaptive system, however, is investigated through a linearization approach including further numerical illustration of specific cases. Finally the simulation results for a magnetorheological seat suspension system with the suggested adaptive control are presented. The results are compared with low-damping and high-damping cases, and such comparison further shows the effectiveness of the proposed nonlinear model-based adaptive control algorithm for damping tuning.

MR seat suspension for vibration control of a commercial vehicle

This paper presents vibration control of a commercial vehicle utilising a magnetorheological (MR) seat damper. A cylindrical type of MR seat damper is manufactured and its field-dependant damping forces are experimentally evaluated. The MR seat damper is then incorporated with a full-vehicle model in which conventional passive dampers are installed for primary and cabin suspension, respectively. After formulating the governing equations of motion of the full-vehicle model, a semi-active skyhook controller is realised by adopting a hardware-in-the-loop-simulation (HILS) methodology. Control responses such as acceleration at the driver's seat are evaluated under both bump and random road conditions.