Automotive Suspension Research Articles

Structural and dynamic analysis of automotive quarter car model suspension system for different materials

The suspension system is a group of mechanical components that links the wheels to the frame or chassis. Suspension systems have received a significant deal of engineering attention as part of an ongoing effort to improve vehicle ride and handling as well as passenger comfort and safety. As the noise, vibration and harshness (NVH) issues are at the forefront of the customers perspective, the vehicle comfort and stability have been considered. In the passenger four-wheelers, shock absorption and vibration due to random excitation are prevalent. The suspension effects play a major role in absorbing the shocks. Hence, this work attempts to model a car suspension and analyzed the dynamic behaviour due to external excitation forces. Among the investigated materials, the epoxy based composites ended-up with the larger deformations and higher stresses compared to the aluminium and steel.

Delay-Dependent Sliding Mode Variable Structure Control of Vehicle Magneto-Rheological Semi-Active Suspension

The vehicle semi-active suspension with Magneto-Rheological Damper (MRD) has been a hot research topic of this decade, featuring the challenging task of the robust control with actuator time delay considerations. In this study, a delay dependent sliding mode variable structure control, based on the Linear Matrix Inequality (LMI), is proposed to suppress the vibration of the Magneto-Rheological Semi-Active Suspension (MRSS) control system. In accordance with the nonlinear characteristics of MRD, a dynamic model of automotive semi-active suspension system, considering time delay, is established. By defining a parameter-dependent Lyapunov switching functional, the conditions for asymptotic stability of closed-loop time delay system are derived, while the sliding mode variable structure control with reduced conservatism is designed. According to the method of LMI, the asymptotic stability problem of sliding mode is transformed into a feasibility problem, which can be solved by the solver ‘feasp’ in LMI toolbox. In addition, the calculation of the critical time delay of MRSS is expressed as a generalized eigenvalue optimization problem. For comparison purposes, three representative controllers, including a conventional sliding mode controller, a delay dependent controller, and a smith compensation, are studied. Simulation and real vehicle testing on bump and random road responses show that, the designed delay dependent controller can ensure the stability of the suspension system, weaken the influence of time delay on the control performance and effectively improve the ride comfort of the vehicle.

Design of Composite Disc Spring for Automotive Suspension with using Numerical Simulation

This paper investigates the replacement of a conventional steel coil spring with a composite disc spring with the aim of minimizing its weight. Simulation in the CAD system Siemens NX 12 was used to determine the composite disc spring’s behavior. The regression functions were stated based on the numerical simulation. Based on the regression functions the solution with the minimum weight was found using software programmed in Matlab. The prototype discs were manufactured from carbon fibre prepreg. Their load-deflection characteristics were tested and compared with the designed values. The experimental results show that using this solution reduces the weight by about 30% in this case.

일래스토메릭 부싱의 회전 방향 모드에 대한 Modified Pipkin-Rogers 모델의 주파수 관련 검증

Elastomeric bushings are structural elements that are used in automotive suspension systems. An elastomeric bushing is a hollow cylinder that is contained between an outer steel cylindrical sleeve and an inner steel cylindrical rod. The outer steel cylindrical sleeve is connected to the components of the suspension system and is used to transfer forces and moments from the wheel to the chassis. The elastomeric material reduces the shock and vibration in this connection. Dynamic simulations of the automotive suspension system involve the interaction between many components. The accurate determination of the transmitted forces and moments between the components, the motion of the components, stress in the components, and energy dissipation is affected by the quality of the bushing model. Several Pipkin-Rogers models have been proposed for the axial mode, radial mode, and torsional mode and modified Pipkin-Rogers models have been proposed for the axial mode and torsional mode. In this research, the modified Pipkin-Rogers model for the torsional mode was verified in a frequency-related rotational angle control test. The results showed that the moment outputs of the modified Pipkin-Rogers model were in very good agreement with those of the Pipkin-Rogers model in the sinusoidal rotational angle control test.

Observer-based event-triggered control and application in active suspension vehicle systems

This paper focuses on event-trigger control of automotive suspension systems. Firstly, fuzzy T-S systems which suitable for automobile suspension systems are studied. Parameter uncertainties and disturbances are included in the fuzzy T-S systems. Secondly, based on linear matrix inequalities (LMIs) and Lyapunov function, the conditions for the stability of fuzzy T-S systems are given. In the meantime, the controller and observer of the fuzzy T-S systems are designed. Finally, the theory is applied to the automotive suspension systems in the simulation.

A study of an industrial counter pressure casting process for automotive parts

Counter pressure casting (CPC) is emerging in the automotive manufacturing industry as an alternative to low-pressure die casting (LPDC) due to its reported superior capabilities in aluminum parts production. This study presents the first comprehensive investigation of how CPC's characteristic feature (applied chamber pressure) influences the fluid flow and heat transport occurring in the process and its effect on casting quality. A large amount of high-quality data was acquired from a commercial CPC process for the production of automotive suspension control arms with two process conditions (standard production and low back-pressure condition). Analysis of the data shows that there are no significant differences between the two process pressure conditions with respect to heat transfer during solidification, as-cast microstructure nor mechanical properties. Generally, in-die measured temperatures exhibited a difference within 10 °C for the two process conditions examined and the ultimate tensile strengths (UTSs) of the samples obtained from castings were within 7% for the two process conditions. Furthermore, there was no measurable difference observed in the Secondary Dendrite Arm Spacings (SDASs) obtained under the two process conditions. However, the implementation of chamber back pressure noticeably reduces the venting rate during the filling stage, leading to 12 s delay in the filling time relative to the low back-pressure condition. A computational modelling methodology, originally developed for LPDC, was applied to simulate the CPC process. The model required only an adjustment to pressure curve to account for the delay of filling owing to the reduced venting rate observed for the higher back-pressure condition. The predicted results were found to correlate well with the measured data, demonstrating that the modelling methodology is broadly applicable to permanent die casting processes.

Active Suspension Control Using an MPC-LQR-LPV Controller with Attraction Sets and Quadratic Stability Conditions

The control of an automotive suspension system by means of a hydraulic actuator is a complex nonlinear control problem. In this work, a linear parameter varying (LPV) model is proposed to reduce the complexity of the system while preserving the nonlinear behavior. In terms of control, a dual controller consisting of a model predictive control (MPC) and a Linear Quadratic Regulator (LQR) is implemented. To ensure stability, quadratic stability conditions are imposed in terms of Linear Matrix Inequalities (LMI). Simulation results for quarter-car model over several disturbances are tested in both frequency and time domain to show the effectiveness of the proposed algorithm.

Synthesis of sliding control system for automotive suspension under kinematic constraints

This article is about the problem of control system synthesis for an active suspension system with not-ideal actuator under kinematic constrains. This paper investigates the influence of hysteresis and the dead zone in an actuator on efficiency of an active suspension system. To reduce the influence of hysteresis and the dead zone a method of synthesis of discontinuous control systems is proposed. The proposed discontinuous control system reduces the sensitivity of the system to disturbances caused by a non-ideal actuator. It enables a fourfold expansion of the distribution range where an active suspension is more effective than a passive suspension. This system also takes into account the nonlinear structure of the control object. The efficiency of the closed system is studied on a dynamic model constructed using the Simulink package.

Emerging approaches for nonlinear parameter varying systems

Emerging approaches for nonlinear parameter varying systems

A design methodology for passive mechatronic vibration absorbers

Passive mechatronic vibration absorbers have demonstrated great performance potential in previous studies. For such devices, optimal design of the electrical circuits therein is critical but challenging since existing techniques have evident limitations: those investigating a few specific circuits leave huge possibilities unexplored; those optimising circuit impedances potentially lead to circuits which cannot be physically implemented. Another challenge lies in the need for considering device parasitic effects (e.g., transducer11The term ‘transducer’ is used in this work to describe the used electric machine, so as to avoid the terms ‘motor’ and ‘generator’ which specifically describe operating regions of the machine. resistance) to guarantee the predicted performance accuracy—this can be extremely time-consuming, especially when exploring numerous design possibilities (e.g., circuits, transducers). To address these two challenges, this paper proposes a novel design methodology, which (1) allows the optimal and practically implementable circuit to be identified among all layouts with predefined complexity; (2) considers the device parasitic effects where necessary, to efficiently explore various possibilities. The validity of this methodology is demonstrated via an automotive suspension design case study, where the obtained significant performance improvement is successfully verified via experiments. This methodology is directly applicable to vibration suppression of other engineering structures and can also be adopted for other mechatronic absorber types.

A New Design Model of an MR Shock Absorber for Aircraft Landing Gear Systems Considering Major and Minor Pressure Losses: Experimental Validation

This work presents a novel design model of a magnetorheological (MR) fluid-based shock absorber (MR shock absorber in short) that can be applied to an aircraft landing gear system. When an external force acts on an MR shock absorber, pressure loss occurs at the flow path while resisting the fluid flow. During the flow motion, two pressure losses occur: the major loss, which is proportional to the flow rate, and the minor loss, which is proportional to the square of the flow rate. In general, when an MR shock absorber is designed for low stroke velocity systems such as an automotive suspension system, the consideration of the major loss only for the design model is well satisfied by experimental results. However, when an MR shock absorber is applied to dynamic systems that require high stroke velocity, such as aircraft landing gear systems, the minor loss effect becomes significant to the pressure drop. In this work, a new design model for an MR shock absorber, considering both the major and minor pressure losses, is proposed. After formulating a mathematical design model, a prototype of an MR shock absorber is manufactured based on the design parameters of a lightweight aircraft landing gear system. After establishing a drop test for the MR shock absorber, the results of the pressure drop versus stroke/stroke velocity are investigated at different impact energies. It is shown from comparative evaluation that the proposed design model agrees with the experiment much better than the model that considers only the major pressure loss.

A Method for Comparing the Fatigue Performance of Forged AZ80 Magnesium

A closed die forging process was developed to successfully forge an automotive suspension component from AZ80 Mg at a variety of different forging temperatures (300 °C, 450 °C). The properties of the forged component were compared and contrasted with other research works on forged AZ80 Mg at both an intermediate forging and full-scale component forging level. The monotonic response, as well as the stress and strain-controlled fatigue behaviours, were characterized for the forged materials. Stress, strain and energy-based fatigue data were used as a basis for comparison of the durability performance. The effects of the starting material, forging temperature, forging geometry/configuration were all studied and aided in developing a deeper understanding of the process-structure-properties relationship. In general, there is a larger improvement in the material properties due to forging with cast base material as the microstructural modification which enhances both the strength and ductility is more pronounced. In general, the optimum fatigue properties were achieved by using extruded base-material and forging using a closed-die process at higher strain rates and lower temperatures. The merits and drawbacks of various fatigue damage parameters (FDP’s) were investigated for predicting the fatigue behaviour of die-forged AZ80 Mg components, of those investigated, strain energy density (SED) proved to be the most robust method of comparison.

Automotive suspension component behaviors driven on flat and rough road surfaces

The objective of this study is to identify the behavior of the car suspension components subjected to road surface contours. Strain signals were measured by installing a strain gauge at the critical area of the coil spring and lower arm. The car was driven on a flat and rough road surface with speeds of 30–40 km/h and 10–20 km/h, respectively. According to the fatigue life assessments based on the strain-life approach, it was found that when the car was driven on the rough road, the components received higher stresses, contributing to a shorter fatigue life. The fatigue life of the coil spring when being driven on the rough road was 1,248 cycles to failure, which was more than 14 times shorter when being driven on the flat road, with 19,060 cycles to failure. Meanwhile the fatigue life of the lower arm being driven on the rough surface was 3,580 cycles to failure, which was almost 3,328 times shorter when being driven on the flat road, with 11,914,000 cycles to failure. The useful life of the coil spring was more than 625 times lower than the lower arm when driven on the flat road, whereas when driven on the rough road, the useful life of the coil spring was almost 3 times lower than the lower arm. In conclusion, the coil spring will fail more than 2 times faster than the lower arm. This is because the contour of the road surfaces provide a vertical load, directly working the coil spring which reduces the load vertically, while the lower arm functions to hold the load when turning.

Neuro-adaptive optimized control for full active suspension systems with full state constraints

In this paper, an adaptive neural network (NN) optimized control strategy is presented to improve the inherent tradeoff between ride comfort of passengers and the suspension travel for full vehicle active suspension system with state constraints. To the best of our knowledge, the automotive suspension system control using hydraulic actuators is a highly complex nonlinear control task, involving external disturbances and uncertainties. To address it, this paper develops the virtual and actual optimal controllers based on backstepping technique and the identifier-actor-critic structure. Meanwhile, the Barrier Lyapunov functions are developed to prevent the systems from the state constraints and the systems states are limited in the preselected compact sets. It is particularly worth mentioning that the proposed optimal control strategy ensures that all the closed-loop signals remain bounded, while the power of the control input as well as the amplitude of the vertical displacement has been minimized. The simulation results show how the full-car system can be controlled optimally and satisfactorily, and confirm the superiority of proposed method.

Body height robust control of automotive air suspension system using finite‐time approach

AbstractOne of the essential characteristics of electronically controlled air suspension (ECAS) is that the automotive height is adjustable. Because ECAS system has complex nonlinearity and noticeable hysteresis, it is easy to make the vehicle oscillate near the target height due to the overcharge/discharge of air springs, which would cause the instability of vehicle body posture. More than that, the existence of external disturbances and uneven loads has impacts on body height control. The complex nonlinear characteristics and the existence of external interference put forward higher requirements for the design of ECAS body height controller. In this paper, by non‐singular coordinate transformation, the nonlinear model of the 1/4 ECAS body height regulation system is transformed into a linear model with a third‐order integral chain firstly, which is closer to the real dynamic characteristics of the suspension system than the linear system with low order. Secondly, based on continuous finite‐time theory, a continuous finite‐time feedback stabilization controller with small parameters is designed, and it turned out that the height regulation system can achieve finite‐time stability. Finally, the simulation results under sinusoidal and random disturbances show that with the comparison with the traditional PD control, the designed finite‐time controller can not only guarantee the system faster response speed and better control accuracy but also obtain the better anti‐jamming performance. By innovatively applying the finite‐time theory to the ECAS system, the designed control system in this paper can afford good robustness for ECAS height adjustment and has great significance to improve the overall performance of ECAS system.

Experimental study on the factors affecting squeak noise occurrence in automotive suspension bushings

In this study, friction tests are performed, via a custom-built friction tester, on specimens of natural rubber used in automotive suspension bushings. By analyzing the problematic suspension bushings, the eleven candidate factors that influence squeak noise are selected: surface lubrication, hardness, vulcanization condition, surface texture, additive content, sample thickness, thermal aging, temperature, surface moisture, friction speed, and normal force. Through friction tests, the changes are investigated in frictional force and squeak noise occurrence according to various levels of the influencing factors. The degree of correlation between frictional force and squeak noise occurrence with the factors is determined through statistical tests, and the relationship between frictional force and squeak noise occurrence based on the test results is discussed. Squeak noise prediction models are constructed by considering the interactions among the influencing factors through both multiple logistic regression and neural network analysis. The accuracies of the two prediction models are evaluated by comparing predicted and measured results. The accuracies of the multiple logistic regression and neural network models in predicting the occurrence of squeak noise are 88.2% and 87.2%, respectively.

Rotary regenerative shock absorbers for automotive suspensions

The increasingly strict limits on pollutant emissions are pushing the car industry towards the electrification of the powertrain and chassis. This scenario has driven the automotive field to the use of energy harvesters. Among these, regenerative shock absorbers are mechatronic devices that enable the energy recovery from road irregularities, thus yielding benefits in terms of fuel saving and ride quality. The state of the art proposes different technologies for regenerative dampers. In this context, rotary dampers represent an unexplored field from the scientific point of view. These devices feature a linkage and a gearbox to convert the suspension linear motion into rotation of an electric machine. This work proposes a novel system-level design methodology for rotary regenerative shock absorbers and explores their performance from an experimental perspective. The design is focused in yielding a compact solution able to fulfill a given damping specification. Hence, the integrated definition of electric machine, gearbox and linkage is addressed by the proposed method. To support the methodology, a case study is presented. A fully functional prototype is produced and successfully validated in terms of damping capability, total conversion efficiency and acoustic behavior. The obtained results demonstrate the validity of the proposed methodology and the advantageous features of rotary dampers with respect to other regenerative suspension solutions.

Adaptive sliding mode control based nonlinear disturbance observer for active suspension with pneumatic spring

Pneumatic springs have been used for the automotive suspension to induce a flexible stiffness and create the control forces according to various uncertain masses of passengers and exogenous inputs. However, the control of the vehicle suspension system using the pneumatic spring is a very complicated task because it involves parametric uncertainties, external disturbances, and system nonlinearities. In this paper, an adaptive sliding mode control (SMC) based on nonlinear disturbance observer (NDOB) is designed to obtain passenger comfort and keep the driving safety of the pneumatic active suspension. The nonlinear disturbance observer is proposed to asymptotically reject the external disturbances and overcome parametric uncertainties which exist in the suspension system such as road profiles, different passenger masses, and actuator dynamics. Finally, comparative simulations and experimental results are given and compared by the pneumatic vehicle suspension test bench to demonstrate the efficiency of the proposed SMC - NDOB scheme for different road conditions. Results show that the RMS acceleration value is decreased by 41.5% when the proposed control is used for the experiment with the bump road profile.

Active dispersing mechanism for settled magnetorheological fluid featuring with rotary blades and inductive coils in twin-tube damper

Magnetorheological (MR) fluid-based applications have accelerated new approaches for vibration and shock control in many scenarios such as the automotive suspension, earthquake mitigation, recoil system and landing gears. However, one of the most serious problems to resolve for successful applications is to mitigate the sedimentation of MR fluids. The sedimentation of MR fluid is inevitable due to the density mismatch between the particles and base liquid. So, several efforts have been made to prevent MR fluid from the settling through additives to match between dispersed phase and dispersing medium, failed because of the difficulty for balancing the density mismatch between the carbonyl iron particles and carrier liquids such as silicone oil. In this work, an active method to resolve the settling problem is proposed and its effectiveness is validated through an experimental test. This work presents an active dispersing mechanism (ADM) with the features of twin tubes structure and full circulation generated by rotary blades driven by an electric motor. A new measurement method based on inductive sensing is provided to characterize the permeability of MR fluid continuously and instantaneously, which is directly pertinent to the dynamic volume concentration of MR fluid in the phase of settling and dispersing. Based on the simply prepared MR fluid, the sedimentation is traced for 24 h and active dispersing is operated after a relatively short time settling of 3 h. The measured results show that the proposed ADM is very effective to recover settled MR fluid after starting the rotary blades less than 1 min.

Damping Variation Effects in Vehicle Semi-active MR Suspensions: A Stress Concentration Analysis

Semi-active vehicle suspensions are used to improve the limited comfort performance of passive vehicle suspensions by varying the damping coefficient according to a control strategy. These benefits have been usually studied in a transient and frequency domain, but rarely in a multi-body dynamic analysis considering the mechanical components and their joints. In this study, the controllability effects of a magnetorheological (MR) damper on the mechanical components of a McPherson automotive suspension are investigated using a stress concentration analysis. Finite element analysis was used with a Quarter of Vehicle (QoV) suspension model configured with an MR damper, and then compared with the passive damper. The simulation results show that an SA damper in the suspension not only improves the dynamic behavior of a road vehicle, but it also has the positive effect of reducing the stress concentrations in a critical suspension element, the knuckle, that are generated by high amplitude road profiles such as rough roads or dangerous street bumps.