Bump Excitations Research Articles

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.

Investigation of a seat suspension installed with compact variable stiffness and damping rotary magnetorheological dampers

Long-term vibration poses a threat to drivers’ health and affects their ride performance. Furthermore, large-magnitude vibration and sudden shocks may even result in end-stop impacts, raising the drivers’ injury risk. To reduce the vibration and avoid end-top impacts, this paper presents an innovative seat suspension installed with variable stiffness and variable damping (VSVD) rotary magnetorheological (MR) dampers. At first, a novel compact VSVD rotary MR damper was designed and prototyped for the suspension, making the suspension’s stiffness and damping controllable. Then, with two identical VSVD MR dampers were installed, the prototyped seat suspension was characterised by an MTS test frame to verify its capabilities of variable stiffness and damping. A control strategy consisting of a nonlinear stiffness control and a no-jerk skyhook damping control was also designed. Finally, the vibration attenuation performance of the seat suspension was numerically and experimentally evaluated under three vibration excitations, i.e., harmonic excitation, bump excitation, and random excitation. Both numerical and experimental results indicate that the vibration control performance of the seat suspension can be significantly improved by the VSVD rotary MR dampers.

Investigation of Vibrations Energy Harvesting from Passive Car Suspension Using Quarter Car Model Under Bump Excitation

This paper aims to evaluate the voltage and the electrical power harvested from the car suspension system under bump excitation using a piezoelectric stack. For this purpose, a quarter car system equipped with a piezoelectric stack installed parallel to the suspension's damper is modelled and investigated in temporal domain using MATLAB/Simulink. The studied system is excited, considering different bump amplitudes to evaluate the harvested voltage and power at different speeds. The effect of the suspension's damping coefficient on the harvested voltage and power is also studied and quantified.

Fault detection and fault tolerant control of vehicle semi-active suspension system with magneto-rheological damper

Compared with other components, actuator fault has a higher probability of occurrence in semi-active suspension with magneto-rheological (MR) damper, which will lead to the safety and reliability of the system. Hence, the fault diagnosis and fault-tolerant methods of semi-active vehicle suspension system with MR damper are investigated in this paper to deal with the fault of MR damper. Firstly, the quarter-vehicle suspension system model is established. Secondly, an unknown input observer (UIO) with strong robustness and simple structure is employed to detect the fault of MR damper; meanwhile, the correlation coefficient method based on the system residuals is used to isolate the fault of MR damper. Lastly, the skyhook fault-tolerant controller (FTC) is designed to compensate the system with fault application. The simulation results under sine excitation, random excitation and bump excitation show that the performance of the proposed FTC always outweigh that of without fault-tolerant when MR damper occurs fault.

Response characteristics of car seat suspension using intelligent control policies under small and large bump excitations

Integration of semi-active devices in Automotive Seating System (ASS) with intelligent control policies help attenuation of the vibration transmitted to the occupant. The current work investigates the effectiveness of a semi-active magnetorheological (MR) damper with ASS for a quarter car model with the application of suitable control algorithms. The system controller calculates the desired damping force using proportional integral derivative (PID), skyhook on/off, PID tuned using genetic algorithm (GA), skyhook continuous and modified skyhook controllers. The signum function damper controller estimates the command voltage required for tracking the desired damping force. The displacement and acceleration of the passive seat system was compared with the semi-active seat suspension system in time and frequency domains. The results from the frequency domain shows that the lowest resonance peaks for the seat system can be achieved using the modified skyhook control policy. The effectiveness of the modified skyhook controller is evaluated in terms of peak to peak (PTP) acceleration, root mean square (RMS) acceleration, frequency weighted RMS acceleration, seat effective amplitude transmissibility (SEAT), vibration dose value (VDV) and crest factor (CF) for enhancing the ride quality. The modified skyhook controller can dissipate the energy better than the passive system. The modified skyhook controller increased the occupant ride quality of SEAT, VDV and CF by 30.41%, 52.84% and 11.62% on account of small bump excitation and 31.76%, 53.27% and 11.02% on account of large bump excitation compared with passive system. The modified skyhook control policy attenuates the vibration better than other control policies addressed in this paper.

Structure design and parameters calculate of suspension system test bench

In order to research the vibration property of different dampers in different road conditions and different control strategies, a type of electro-hydraulic road excitation test bench is designed in allusion to a quarter of vehicle suspension system of a single wheel. Firstly, the structure and components of the test bench is designed, then the design requirements and targets are ascertained for the three types of normally used excitation through theoretical analysis, they are sine excitation, random excitation, and bump excitation. After that, the parameters of the test bench are calculated according to the requirements and targets. Finally, a prototype of the test bench is manufactured and the performances of the test bench are tested under the three types of excitation respectively, the results of the test show that, the errors between the actual displacements and the target displacements are tiny, and the test bench could make the objective road excitation reappear well.

Higher order sliding mode control for active suspension systems subject to actuator faults and disturbances

As the possibility of faults in active suspension actuators are higher and more severe compared to other components, this study presents a fault-tolerant control approach based on the second-order sliding mode control method. The aim of the controller is to improve riding comfort, guarantee handling stability, and provide adequate suspension stroke in the presence of disturbances and actuator faults. A nonlinear full-vehicle suspension system and hydraulic actuator with nonlinear characteristics are adopted for accurate control. Firstly, a nonlinear sliding manifold based on a nonsingular fast terminal sliding mode controller is introduced to suppress the sprung mass heave, pitch, and roll motions arising from road disturbances. Secondly, a second-order sliding mode-based super twisting controller is utilized to track the desired forces generated by the nonsingular fast terminal sliding mode controller with actuator faults and uncertainties. The controllers are robust against disturbances, uncertainties, and faults. Moreover, the stability of the super twisting controller is proved by the strong Lyapunov functions. Finally, numerical simulations are performed to demonstrate the effectiveness of the controller. Four different conditions, random road profile, bump road excitation, single-wheel bump excitation, and partial faults are considered. The main contributions of this study are: (1) combination of the above algorithms to deal with actuator faults and improve active suspension performance; (2) the controller proposed in this study has a simple structure. Simulation results indicate that the nonsingular fast terminal sliding mode super twisting controller can guarantee the performance of the closed-loop system under both faulty and healthy conditions.

Vibration reduction of seat suspension using observer based terminal sliding mode control with acceleration data fusion

In this work, a disturbance observer and state observer based terminal sliding mode (TSM) controller with acceleration data fusion is proposed for the active control of a seat suspension. In practical applications, the driver's body and the friction forces are difficult to be accurately described with a mathematical model; for this reason, the proposed controller is designed based on a model simplified from a 6-degree-of-freedom (6-DOF) seat-driver model with nonlinear friction. The disturbance observer and state observer are designed together with Linear Matrix Inequality (LMI) method. For improving the observer's performance, a complementary filter is applied to fuse the estimation of the seat suspension velocity from the acceleration measurement and the state observer. The proposed controller is validated using simulations with various bump excitations applied, and the conventional state feedback TSM controller is implemented for comparison. The proposed controller is also implemented in a practical active seat suspension prototype, and a well-tuned commercial heavy duty vehicle seat suspension is applied for comparison. The power spectral density (PSD) value and ISO 2631–1 standard are used to evaluate the active seat suspension system's performance under random vibration. Both the simulation and the experimental results indicate that with the proposed controller, the vibration magnitude caused by a rough road can be greatly reduced, and the driver ride comfort is greatly improved.

Dynamic modelling and design of tracked vehicle suspension system using magnetorheological valve

This paper presents dynamic modelling and optimal design of magnetorheological fluid (MR) based suspension system for a tracked vehicle. The MR suspension unit (MRSU) is designed to combine with a gas spring. The governing equation of motion of a tracked vehicle suspension is derived and the optimisation problem to find optimal geometric dimensions of the MR valve is undertaken to improve damping force and control energy. The performance characteristics of the optimised MRSU are then evaluated and compared with initial one. In addition, vibration control performances of the tracked vehicle suspension installed with the optimised MRSU are evaluated under bump excitation.

Discrete-time sliding mode control for MR vehicle suspension system

This paper presents control performance of a full-vehicle suspension system featuring magnetorheological (MR) dampers via a discrete-time sliding mode control algorithm (DSMC). A cylindrical MR damper is designed by incorporating Bingham model of the MR fluid and the field-dependent damping characteristics of the MR damper are evaluated. A full-vehicle suspension model installed with independent four MR dampers is constructed and the governing equations which include vertical, pitch and roll motion are derived. A discrete-time control model is established with considering system uncertainties and a discrete-time sliding mode controller which has inherent robustness to model uncertainty and external disturbance is formulated. Vibration control performances under bump excitation are evaluated and presented.

Vibration control of a smart material based damper system considering temperature variation and time delay

This paper presents vibration control responses of an electrorheological (ER) damper system subjected to temperature variation and time delay. The field-dependent yield stress of the ER fluid is experimentally evaluated at various temperatures and the dynamic characteristics of the ER damper are investigated in order to obtain the time constant. These two properties are integrated with the governing model of a quarter car ER suspension system, and a sliding mode controller is formulated. Vibration control responses of a quarter car model installed with the ER damper system are evaluated under bump excitation.

Multiple-bump roadholding test: Description and metric interpretation

Road vehicle roadholding comprehends directional response to road inputs. This response is primarily a function of the roadway's frequency content and amplitude and the vehicle's inertial, suspension and tyre characteristics. There is also evidence that suspension kinematic and compliance steer properties can have a significant contribution (Rill, G. Steady state cornering on uneven roadways. SAE paper 860575, 1986). The multiple-bump roadholding test measures vehicle response to a periodic bump of varying frequency while cornering. By driving a vehicle at different speeds over a set of periodic bumps placed on circles of different diameters, it is possible to observe the response to different fundamental bump excitation frequencies at a particular lateral acceleration. This paper describes the test procedure, measured vehicle responses and the metrics calculated.

Acoustic emission of laser textured disks influenced by bump excitation

The acoustic emission behavior of laser textured disks was studied in both time and frequency domains. The high intensity peaks observed during a starting process are related to specific rotational speeds. Some peaks are associated with slider body resonance excited by a harmonic of the laser bump interaction. A finite element analysis was performed to determine the natural frequencies of sliders. The AE intensity curve can give a correct take-off velocity for a laser textured disk if at least one harmonic component of the bump excitation falls within the filter range at the real take-off velocity. With amplifier settings similar to those for mechanically textured disks, it is not feasible for an AE system to detect contact if the bump spacing is smaller than a critical value.

Photochemistry near a semiconductor surface

A numerical study of photochemistry near a rough InSb surface, whose roughness is modeled as a spheroidal bump protruding out of the substrate plane, has been carried out. The semiconducting nature of the substrate is taken into account via a model dielectric function. ‘‘Shape resonance’’ effects through the resonant coupling of the bump excitations to photons and various substrate modes (plasmons, phonons, etc.) are calculated and included in the study. Unlike in the case of a metal surface, radiation damping as well as damping due to adsorbate–substrate coupling are seen to play a minor role.