Random Road Excitation Research Articles

Semi-Active Suspension Design for Truck Using Pneumatic Spring Joining MR Fluid Damper Based on Neural Networks Controller

<div>In order to modify both stiffness and damping rates according to various road conditions, this research introduces a pneumatic spring in conjunction with a magnetorheological (MR) fluid damper as a single suspension unit for each wheel in the truck. Preventing weight transfer and improving riding comfort during braking, acceleration, and trajectory prediction are the main objectives. A two-axle truck has been used, consisting of three degrees of freedom for the sprung mass, including vertical, pitch, and roll motions, and four degrees of freedom for the unsprung masses, which have been redesigned according to the different types of springs and dampers. Pneumatic-controlled springs, often referred to as dynamic or classic models, replace laminated leaf springs commonly found in vehicles. Additionally, an MR damper replaces a hydraulic double-acting telescopic shock absorber. These models are studied to evaluate the effect of pneumatic spring parameters on truck dynamics. Pneumatic stiffness and the intended damping force are monitored by a recurrent neural network in conjunction with leveling control. This process provides the recommended voltage for the MR damper based on the Signum function damper controller. The performance of the suspension is assessed in the time and frequency domains for both step and random road excitations using vehicle dynamic parameters. Six suspension system configurations are compared with the air spring dynamic model integrated with the MR damper (Model 6), which is recommended as a suspension system for trucks. According to simulation data, when compared to alternative suspension systems, Model 6 significantly enhances both ride comfort and vehicle stability. Model 6 offers improvements in tire workload, truck path, tire–ground contact point during acceleration, braking efficiency, and stopping distance. Compared to previous controlled models, Model 6 also demonstrates zero steady-state offset and zero steady-state error.</div>

Analysis of a bus vertical dynamic performances – a comparison between linear and nonlinear suspension systems

This paper mainly focuses on the numerical calculation to determine the vertical evaluation indexes with all three types of typical harmonic, transient and random road excitations. The effects of linear and nonlinear suspension characteristics on the vertical evaluation indexes are fully understood systematically. The ride comfort, suspension working space, and road holding are analyzed for both two cases of linear and nonlinear suspension systems. The improvement of the vertical stability and road holding in the case of nonlinear suspension subjected under three different excitations could be characterized most meaningfully. The obtained results help to systematically get full understanding of the investigated problem nature. It also should guide interested readers in suspension design to improve the stability, safety, and ride comfort of buses.

Analysis of damping multi-mode switching control of semi-active suspension based on digital controlled hydraulic cylinders group

In order to improve the ride comfort of vehicle suspension, this article proposes a damping multi-mode semi-active suspension system and its control method. The semi-active suspension takes a hydraulic electromagnetic shock absorber based on a digital controlled hydraulic cylinders group as the core, and realizes the switching of multiple damping modes by controlling the on-off statuses of three groups of switch solenoid valves, thus making the semi-active suspension have the characteristics of damping multi-mode adjustable. The damping characteristics corresponding to the single damping mode are verified through the prototype bench test of the shock absorber principle. On this basis, the semi-active suspension model of the vehicle is established, and a multi-mode switching control strategy of suspension damping using fuzzy control is designed. The filtered Gaussian white noise is used as the random road excitation for simulation. The simulation results show that compared with the traditional passive suspension and the semi-active suspension based on skyhook control, the damping multi-mode semi-active suspension based on the digital controlled hydraulic cylinders group can realize the switching of multiple damping modes, have good damping performance, and help to improve the vehicle ride comfortable capability.

Neural Network-Based Adaptive Height Tracking Control of Active Air Suspension System with Magnetorheological Fluid Damper Subject to Uncertain Mass and Input Delay.

In this paper, we present a novel robust adaptive neural network-based control framework to address the ride height tracking control problem of active air suspension systems with magnetorheological fluid damper (MRD-AAS) subject to uncertain mass and time-varying input delay. First, a radial basis function neural network (RBFNN) approximator is designed to compensate for unmodeled dynamics of the MRD. Then, a projector-based estimator is developed to estimate uncertain parameter variation (sprung mass). Additionally, to deal with the effect of input delay, a time-delay compensator is integrated in the adaptive control law to enhance the transient response of MRD-AAS system. By introducing a Lyapunov-Krasovskii (LK) functional, both ride height tracking and estimator errors can robustly converge towards the neighborhood of the desired values, achieving uniform ultimate boundness. Finally, comparative simulation results based on a dynamic co-simulator built in AMESim 2021.2 and Matlab/Simulink 2019(b) are given to illustrate the validity of the proposed control framework, showing its effectiveness to operate ride height regulation with MRD-AAS systems accurately and reliably under random road excitations.

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.

A Robust Control for a Controllable Suspension System with an Input Time Delay

In this study, a state feedback robust control strategy with time delay dependence for the uncertainty, fault, and input time delay of a vehicle’s controllable suspension system is designed. Firstly, based on the working principle of the adjustable damping suspension system, the total damping force of the suspension is divided into “foundation damping force” and “controllable damping force”, taking the adjustable damping interval as the constraint boundary, which varies with the actuating velocity. Furthermore, based on the sensitivity analysis of the input time delay’s relationship with damping force disturbance, it exerts influence on the controllable damping force part. The associated uncertainty and fault are defined through linear fraction transformation and proportional gain, respectively, and the two are decoupled from the control mechanism. Then, based on the Lyapunov stability theory, a robust control law for the time-delay-dependent H∞ state feedback is designed and transformed into a linear matrix inequality convex optimization problem to solve. Finally, the feasibility and effectiveness of the proposed method are verified by designing different combinations of uncertainty and fault tests and by comparing and analyzing these with the time-delay-independent H2/H∞ robust control strategy under random and pulse road excitation.

Influence of random road excitation on DCT vehicle dynamic characteristics during starting and shifting

Influence of random road excitation on DCT vehicle dynamic characteristics during starting and shifting

Optimal nonlinear polynomial control of a quarter-vehicle suspension system under harmonic and random road excitations

The present paper proposes an optimal polynomial control strategy for a quarter-vehicle suspension system based on dynamic programming. The optimal control objective is to decrease the responses of sprung mass acceleration, suspension deformation and road excitation, which are reflected in the performance index. The optimal control force is obtained through the principle of dynamic programming, and the form of the optimal control force mainly depends on the form of the cost function. The optimal nonlinear polynomial control (NPC) force is derived by selecting the cost function in polynomial form. The linear feedback matrix and nonlinear feedback matrix in the NPC force are determined by the Riccati equation and Lyapunov equation, respectively. The root mean square (RMS) responses of the sprung mass acceleration, suspension deformation and road load of driving vehicles under deterministic and random road surfaces are calculated. The numerical results showed that the proposed NPC strategy has a better control effect over the traditional linear quadratic regulator (LQR), especially on the peak reduction of sprung mass acceleration. Finally, the optimal control force is divided into active control force and passive control force. The energy input of the optimal control force can be reduced by only inputting the active control force.

Identification of combustion parameters from cylinder head vibration signal with the influence of random road excitation

The combustion process feedback information can be extracted from the vibration signals of the cylinder head. This is of positive significance for the online monitoring of combustion status and closed-loop control of combustion processes in internal combustion engines. To obtain the combustion process feedback information under the random road excitation (RRE) condition, this paper firstly simulates and analyses the influence of RRE on the combustion parameters identification by an established simplified diesel-suspension model. Results show that the amplitude, frequency and phase of road excitation signal seriously affect the identification of the combustion characteristics, and the combustion excitation response signal is covered by the road excitation response signal in most cases. Then, a method of combining a high-pass filter and principal component analysis (HPF-PCA) is proposed to extract the combustion parameters. This method effectively eliminates the road excitation response signal and successfully identifies the start of combustion (SOC), the location of maximum pressure rise rate (LMPRR) and the location of peak pressure (LPP) from the processed vibration acceleration signal. Finally, the phase deviation caused by the filtering is corrected based on the relationship between the phase deviation of SOC and the cut-off frequency of filtering. The corrected results show that the maximum deviation between the SOC identified from the vibration signals that with and without the influence of road excitation is 0.8 deg.

Fatigue Life Modelling of Steel Suspension Coil Springs Based on Wavelet Vibration Features Using Neuro-Fuzzy Methods

This study proposed wavelet-based approaches to characterise random vibration road excitations for durability prediction of coil springs. Conventional strain-life approaches require long computational time, while the accuracy of the vibration fatigue methods is unsatisfactory. It is therefore a necessity to establish an accurate fatigue life prediction model based on vibrational features. Wavelet-based methods were applied to determine the low-frequency energy and multifractality of road excitations. Strain-life models were applied for fatigue life evaluation from strain histories. ANFIS modelling was subsequently adopted to associate the vibration features with the fatigue life of coil springs. Results showed that the proposed wavelet-based methods were effective to determine the signal energy and multifractality of vibration signals. The established vibration-based models showed good fatigue life conservativity with a data survivability of more than 90%. The highest Pearson coefficient of 0.955 associated with the lowest RMSE of 0.660 was obtained by the Morrow-based model. It is suggested that the low-frequency energy and multifractality of the vibration signals can be used as fatigue-related features in life predictions of coil springs under random loading. Finally, the proposed model is an acceptable fatigue life prediction method based on vibration features, and it can reduce the dependency on strain data measurement.

Adaptive variable domain fuzzy PID control strategy based on road excitation for semi-active suspension using CDC shock absorber

Electronic suspensions can take into account the ride comfort and safety of the vehicle, the continuous damping control (CDC) shock absorber is the core component of the electronic suspension. CDC shock absorber and electronic suspension have a promising future for application in automotive. This paper proposed an adaptive variable domain fuzzy PID control strategy for semi-active suspensive to effectively improve the vibration reduction effect of the automobile suspension system. By analyzing the dynamic performance of the semi-active suspension system coupled with the CDC shock absorber to get the control variables, we deduce the math function of semi-active suspension. In addition, the simulation model of the semi-active suspension based on the bench test of shock absorbers was established. Under the observation of performance indicators, though comparing the new control and other different control strategies, which can prove the effectiveness of the new method. From the simulation results, the shock absorber simulation model is correct and the performance of the proposed control strategies are effective than the traditional PID control and fuzzy control under the random road excitation. In particular, in the 120 km/h case by using VAC, the peak values of the suspension dynamic deflection, vehicle body acceleration, and car body dynamic load are reduced by 49.6%, 50%, and 50%. For a semi-active suspension using the CDC shock absorber, the proposed control method provides better ride comfort to passengers due to lower peak compared with the fuzzy control strategy and the PID control strategy, it can be used as an optimized design method for suspension.

Advanced Vertical and Lateral Coupling Dynamics Control for a Four In-wheel Motor Drive Electric Vehicle

This paper presents an advanced vertical and lateral coupling dynamics control for stabilizing the vertical and lateral motion of a four in-wheel motor drive electric vehicle. The novelty is to investigate the possibilities of enhancing the lateral stability of electric vehicle through the correct control of their suspension system, and further improve the suspension system performances using direct yaw control (DYC) without having a contradictory effect between the vertical and lateral controllers. There are two main objectives; the first is to improve ride comfort, road holding and vehicle lateral handling performance simultaneously by using a new combined full vehicle suspension system, and the second is to strengthen electric vehicle lateral handling performance by using a sliding mode technique for controlling the direct yaw moment. For vehicle suspension system control, we are seeking to design a skyhook control to control the suspension damper and a sliding mode control to stabilize the position of the sprung masses of the in-wheel damper vibration absorber (DVA). To solve the problems caused by the chattering phenomena and ensure the exponential stability of the sprung mass, the continuous singular terminal sliding-mode controller is selected to design the sliding mode control used as a DVA controller. Simulation results show that the coordinated control between DYC and combined full vehicle suspension system under several turns' maneuvers and under random road excitations, can stabilize electric vehicle lateral motion, enhance the vehicle ride comfort, road holding, enhance the rollover resistance performance and satisfy the main suspension performances simultaneously.

Optimum Response of a Nonlinear Passive Vehicle Suspension System under Random Road Excitations

Optimum Response of a Nonlinear Passive Vehicle Suspension System under Random Road Excitations

A reinforcement learning backstepping‐based control design for a full vehicle active Macpherson suspension system

This paper presents a reinforcement learning backstepping-based control scheme for the design of a full vehicle active suspension system such that both the superior ride comfort and stabilization are achieved. It is well known that the traditional backstepping control scheme is suitable to solve higher order nonlinear system based on the strict-feedback form; however, the disadvantage of the procedure requires computing the derivatives of virtual control signals, which is a very complex task. Therefore, a reinforcement learning scheme using the deep deterministic policy gradient (DDPG) control strategy is developed to replace the process of finding virtual control force in backstepping method. It not only avoids the complexity of analytically calculating the derivatives of the virtual control signals, but also retains the systems robustness when there exist random disturbances from road irregularities. To verify the performance of the proposed active suspension control scheme, the random road unevenness profiles according to ISO 8608 is considered as vertical and lateral disturbance input excitation of a full-vehicle suspension system. Compared with conventional passive suspension system and backstepping control scheme, the proposed approach can be demonstrated to not only effectively improve ride comfort under random road excitation, but also improve the transient response and robustness.

Optimal Chassis Suspension Design for Towbarless Towing Vehicle for Aircraft Taxiing

<div class="section abstract"><div class="htmlview paragraph">The towbarless aircraft taxiing system (TLATS) consists of the towbarless towing vehicle (TLTV) and the aircraft, of which the nose wheel is lifted and fixed by the picking up and holding system of the TLTV. The aircraft is towed to the destination in a long distance with a high speed of about 40 km/h only driven by the TLTV, which has the advantages of efficiency and economy by comparing with the traditional towing operation at a low speed of 5 km/h and with a short towing distance of about 50 m. However, the increase of the towing velocity leads to an deteriorate vibration problem in terms of the uncomfortable of the driver and reduction of the structure safe life limit, due to the lack of the chassis suspension for the vibration isolation of the TLTV. Therefore, the air suspension is introduced to the TLTV to alleviate the vibration. The dynamic model of the TLATS with air suspensions is derived. The chassis bounce natural frequency is presented, and the initial stiffness and damping coefficients are determined. The parameters of the air spring, i.e., the initial pressure, volume, effective area under the working condition, are optimally designed. The ride performances of the TLATS with the air suspensions under the random road excitation are compared with those with coil spring suspension and without suspension. The simulation results show that the optimal air suspensions could alleviate the TLATS’ vibration during the high-velocity towing of the aircraft.</div></div>

Development of Robust Guaranteed Cost Mixed Control System for Active Suspension of In-Wheel-Drive Electric Vehicles

This paper presents a mixed H2/H∞-based robust guaranteed cost control system design of an active suspension system for in-wheel-independent-drive electric vehicles considering suspension performance requirements and parameter variation. In the active suspension system model, parameter uncertainties of active suspension are described by the bounded method, and the perturbation bounds can be also limited; then, the uncertain quarter-vehicle active suspension model where in-wheel motor is suspended as a dynamic vibration absorber is established. The robust guaranteed cost mixed H2/H∞ feedback controller of the closed-loop active suspension system is designed using Lyapunov stability theory, in which the suspension working space, dynamic tire displacement, and the active control force are taken as H∞ performance indices, the H2 norm of body acceleration is selected as the output performance index to be minimized, and then a comprehensive solution is transformed into a convex optimization problem with linear matrix inequality constraints. Simulations on random and bump road excitations are implemented to verify and evaluate the performance of the designed controller. The results show that the active suspension with developed robust mixed H2/H∞ controller can effectively achieve better ride comfort and road-holding ability compared with passive suspension and alone H∞ controller.

Dynamic analysis and design of power management circuit of the nonlinear electromagnetic energy harvesting device for the automobile suspension

A nonlinear electromagnetic energy harvester (EMEH) for the automobile suspension is designed. The magnetic flux density and the magnet repulsive force of the mechanical model are determined by finite element analysis. The dynamic model of a quarter car with the nonlinear EMEH under random road excitation is established. The influence of structure parameters on output characteristics of the nonlinear EMEH is studied. In order to further improve the output power, effects of the road class, the car speed, and the load resistance are investigated in detail. Studies have revealed that the higher the road class and the larger the car speed are, the better output characteristics of the nonlinear EMEH become. In order to prove that the nonlinear magnet repulsive force can significantly improve the output power, output characteristics of the nonlinear EMEH and the linear EMEH are compared. Finally, the power management circuit matching with the nonlinear EMEH is designed, which can convert the unstable alternating voltage into the stable direct voltage, and directly supply power to electronic devices. There are two innovations in this paper. One is the introduction of the nonlinear magnet repulsive force and the amplification bar in the structural design. Another is to design the power management circuit of the high energy conversion efficiency, which is up to 74.3% for the car speed 25 m/s on the road of class C.

A robust hybrid generator for harvesting vehicle suspension vibration energy from random road excitation

Existing energy harvesters are mostly designed into the electromagnetic shock absorbers to replace the original dampers in automotive suspension systems, possibly deteriorating sprung mass acceleration when the energy harvesters are in trouble. Therefore, this study proposed a hybrid generator based on the sliding-mode triboelectric nanogenerator (S-TENG) and electromagnetic generator (EMG) to harvest the suspension vibration energy without replacing the original damper and deteriorating sprung mass acceleration. First, the patterned polyimide (PI) films were prepared to solve the challenge of the poor durability of the S-TENG due to material wear. The results showed that the wear mass loss of PI film diminished with the decrease of pillar pitch, and the wear mass loss of P2 film was only 37% of that of the smooth one. Furthermore, whether the patterned surface could improve the electrical output of the S-TENG depended on the pattern parameters, which was a departure from the common view that any pattern could enhance triboelectrification. In this paper, P2 was the optimal textural parameter for improving the durability and electrical output of the S-TENG, which could provide a texture design reference for the S-TENG. Second, the hybrid generator charged a 4.7 μF capacitor to 18.05 V in 60 s, and the contribution ratio of charging voltage of the S-TENG component increased with extended charging time. Finally, the hybrid generator moved together with the original shock absorber without a noticeable impact on sprung mass acceleration, which can make the accelerometer self-powered at different random road excitations.

Parameters uncertainty in pareto optimization of nonlinear inerter-based suspension system under nonstationary random road excitation

Ignoring the possible impacts of uncertainties in vehicle components during the design phase can undermine the safety of passengers and the vehicle performance. The main function of a suspension system is to provide satisfactory ride comfort and road-holding with a sufficiently low probability of rollover. Despite many studies on the design of new suspension systems with inerters, the effect of uncertainties in vehicle weight and tire stiffness on the design of suspension with inerters has not received much attentions. This paper presents a new type of suspension with inerters and asymmetric dampers and investigates the dynamic behavior of a vehicle under variable vehicle speed. Moreover, the effect of uncertainties on the choice of acceptable values of inerters is evaluated. For this investigation, the authors developed a 9-DOF full vehicle model with roll and yaw motions under non-stationary random road excitations in the time and frequency domains and studied its dynamic response with different suspension models. The optimal design was performed using a multi-objective optimization algorithm called MOEA/D. The best model was then used to determine the effect of uncertainties on the choice of inerters. The optimization results show that using the optimized suspension with inerters and nonlinear dampers instead of conventional design improves the ride comfort by 0.16%, the vehicle road-holding by 3.54%, and the rollover probability by 44.73%. In the proposed model, by changing the values of vehicle parameters with uncertainty, the choice of inerters to have an acceptable performance would be variable.

Research on vibration reduction of semi-active suspension system of quarter vehicle based on time-delayed feedback control with body acceleration

In this paper, the mechanical model of two-degree-of-freedom vehicle semi-active suspension system based on time-delayed feedback control with vertical acceleration of the vehicle body was studied. With frequency-domain analysis method, the optimization of time-delayed feedback control parameters of vehicle suspension system in effective frequency band was studied, and a set of optimization method of time-delayed feedback control parameters based on “equivalent harmonic excitation” was proposed. The time-domain simulation results of vehicle suspension system show that compared with the passive control, the time-delayed feedback control based on the vertical acceleration of the vehicle body under the optimal time-delayed feedback control effectively broadens the vibration absorption bandwidth of the vehicle suspension system. The ride comfort and stability of the vehicle under random road excitation are significantly improved, which provides a theoretical basis for the selection of time-delayed feedback control strategy and the optimal design of time-delayed feedback control parameters of vehicle suspension system.