Feasibility of Using Nonlinear Time-Frequency Control for Magnetorheological Dampers in Vehicle Suspension

Semi-active vehicle suspensions that use magnetorheological (MR) dampers are able to better dissipate vibrations compared to conventional dampers because of their controllable damping characteristics. The performance of current MR damper control methods is often hindered by incorrect assumptions and linearized models. Therefore, a need exists to design an adaptive controller with improved accuracy and reliability. The objective of this research is to design an improved controller for MR dampers in vehicle suspension using the nonlinear time-frequency control approach and evaluate its feasibility by numerically employing MATLAB Simulink. Simulations in this research are performed using a simplified quarter car suspension model and modified Bouc-Wen damper model. The proposed control method is evaluated based on its ability to reduce the amplitude of vibrations and minimize acceleration of the car body for various test cases. Simulations are also performed using the skyhook controller and passive suspension to assess the performance of the proposed controller. The results of the simulations show that the proposed nonlinear time-frequency controller can successfully be applied to an MR damper suspensions system for vibration control. The proposed controller outperforms the skyhook controller in terms of reducing acceleration of the car body in each of the tested scenarios. The proposed controller also shows the ability to more efficiently manage the current input to the system. In general, the skyhook controller gives more improved vibration amplitude responses but is prone to generate large spikes in car body acceleration at higher frequency road profile inputs. Simulations performed with the passive system show large displacement amplitudes and inability to prevent oscillation. The feed-forward aspect and adaptive nature of the proposed controller gives it the ability to better compensate for the time-delay in the operation of the MR damper. The proposed controller shows sensitivity to controller parameters when pursuing the best response for different road profile input cases

Feasibility of Using Nonlinear Time-Frequency Control for Magnetorheological Dampers in Vehicle Suspension

Semi-active vehicle suspensions that use magnetorheological (MR) dampers are able to better dissipate vibrations compared to conventional dampers because of their controllable damping characteristics. The performance of current MR damper control methods is often hindered by incorrect assumptions and linearized models. Therefore, a need exists to design an adaptive controller with improved accuracy and reliability. The objective of this research is to design an improved controller for MR dampers in vehicle suspension using the nonlinear time-frequency control approach and evaluate its feasibility by numerically employing MATLAB Simulink. Simulations in this research are performed using a simplified quarter car suspension model and modified Bouc-Wen damper model. The proposed control method is evaluated based on its ability to reduce the amplitude of vibrations and minimize acceleration of the car body for various test cases. Simulations are also performed using the skyhook controller and passive suspension to assess the performance of the proposed controller. The results of the simulations show that the proposed nonlinear time-frequency controller can successfully be applied to an MR damper suspensions system for vibration control. The proposed controller outperforms the skyhook controller in terms of reducing acceleration of the car body in each of the tested scenarios. The proposed controller also shows the ability to more efficiently manage the current input to the system. In general, the skyhook controller gives more improved vibration amplitude responses but is prone to generate large spikes in car body acceleration at higher frequency road profile inputs. Simulations performed with the passive system show large displacement amplitudes and inability to prevent oscillation. The feed-forward aspect and adaptive nature of the proposed controller gives it the ability to better compensate for the time-delay in the operation of the MR damper. The proposed controller shows sensitivity to controller parameters when pursuing the best response for different road profile input cases

Active suspension control of electric vehicle with in-wheel motors

In-wheel motor (IWM) technology has attracted increasing research interests in recent years due to the numerous advantages it offers. However, the direct attachment of IWMs to the wheels can result in an increase in the vehicle unsprung mass and a significant drop in the suspension ride comfort performance and road holding stability. Other issues such as motor bearing wear motor vibration, air-gap eccentricity and residual unbalanced radial force can adversely influence the motor vibration, passenger comfort and vehicle rollover stability. Active suspension and optimized passive suspension are possible methods deployed to improve the ride comfort and safety of electric vehicles equipped with inwheel motor. The trade-off between ride comfort and handling stability is a major challenge in active suspension design. This thesis investigates the development of novel active suspension systems for successful implementation of IWM technology in electric cars. Towards such aim, several active suspension methods based on robust H∞ control methods are developed to achieve enhanced suspension performance by overcoming the conflicting requirement between ride comfort, suspension deflection and road holding. A novel fault-tolerant H∞ controller based on friction compensation is in the presence of system parameter uncertainties, actuator faults, as well as actuator time delay and system friction is proposed. A friction observer-based Takagi-Sugeno (T-S) fuzzy H∞ controller is developed for active suspension with sprung mass variation and system friction. This method is validated experimentally on a quarter car test rig. The experimental results demonstrate the effectiveness of proposed control methods in improving vehicle ride performance and road holding capability under different road profiles. Quarter car suspension model with suspended shaft-less direct-drive motors has the potential to improve the road holding capability and ride performance. Based on the quarter car suspension with dynamic vibration absorber (DVA) model, a multi-objective parameter optimization for active suspension of IWM mounted electric vehicle based on genetic algorithm (GA) is proposed to suppress the sprung mass vibration, motor vibration, motor bearing wear as well as improving ride comfort, suspension deflection and road holding stability. Then a fault-tolerant fuzzy H∞ control design approach for active suspension of IWM driven electric vehicles in the presence of sprung mass variation, actuator faults and control input constraints is proposed. The T-S fuzzy suspension model is used to cope with the possible sprung mass variation. The output feedback control problem for active suspension system of IWM driven electric vehicles with actuator faults and time delay is further investigated. The suspended motor parameters and vehicle suspension parameters are optimized based on the particle swarm optimization. A robust output feedback H∞ controller is designed to guarantee the system’s asymptotic stability and simultaneously satisfying the performance constraints. The proposed output feedback controller reveals much better performance than previous work when different actuator thrust losses and time delay occurs. The road surface roughness is coupled with in-wheel switched reluctance motor air-gap eccentricity and the unbalanced residual vertical force. Coupling effects between road excitation and in wheel switched reluctance motor (SRM) on electric vehicle ride comfort are also analysed in this thesis. A hybrid control method including output feedback controller and SRM controller are designed to suppress SRM vibration and to prolong the SRM lifespan, while at the same time improving vehicle ride comfort. Then a state feedback H∞ controller combined with SRM controller is designed for in-wheel SRM driven electric vehicle with DVA structure to enhance vehicle and SRM performance. Simulation results demonstrate the effectiveness of DVA structure based active suspension system with proposed control method its ability to significantly improve the road holding capability and ride performance, as well as motor performance

Semi-active suspension control algorithms of a car moving on rough road pavement

Disertacijoje nagrinėjamos elektroniniu būdu reguliuojamos lengvųjų automobilių pakabos. Automobiliuose dažniausiai naudojamos pasyvios pakabos, kurios turi gamintojo nustatytas pastovias slopinimo charakteristikas. Tačiau sparčiai tobulėjant elektroninių sistemų valdymo technologijoms, į automobilius vis dažniau montuojami pakabos slopinimo elementai, kuriais galima keisti slopinimo charakteristikas. Pagrindinis tokių sistemų trūkumas paaiškėja automobiliui užvažiavus ant didesnių kelio nelygumų. Kadangi amortizatorius yra elektroninė sistema, turi veikimo uždelsimą, tad pageidaujamos slopinimo reikšmės pakeičiamos per vėlai. Disertaciją sudaro įvadas, trys skyriai, bendrosios išvados, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai bei penki priedai. Įvadinėje dalyje nagrinėjama tiriamoji problema ir darbo aktualumas. Aprašomas tyrimų objektas, suformuluojamas tikslas ir darbo uždaviniai, pristatoma tyrimų metodika, darbo mokslinis naujumas, rezultatų praktinė reikšmė ir ginamieji teiginiai. Įvado pabaigoje pateikiamos disertacijos tema autoriaus paskelbtos publikacijos, pranešimai mokslinėse konferencijose ir seminaruose bei disertacijos struktūra. Pirmajame skyriuje apžvelgiama mokslinė literatūra disertacijos tema. Pateikiama mokslinių tyrimų su lengvųjų automobilių pakabomis analizė, taip pat naudojamų pakabų valdymo principų apžvalga. Aptariami kelio paviršiaus nelygumų nustatymo būdai, atliekama virpesių, veikiančių vairuotoją, keleivius ir automobilio elementus, analizė. Antrajame skyriuje pristatomas automobilio su sumontuotu lazeriniu atstumo jutikliu matematinis modelis, modelio patikrinimas. Aprašomas sukurtas kėbulo svyravimų kompensavimo modelis ir elektroniniu būdu valdomos pakabos algoritmas. Pateikiami rezultatai gauti atliekant tyrimus su pasyvia ir pusiau aktyvia pakabomis. Trečiajame skyriuje pateikta eksperimentinių tyrimų metodika ir naudota įranga. Pristatomi lazerinio jutiklio optimalios montavimo vietos ir padėties paieškos eksperimentiniai tyrimai, jų rezultatai. Pateikiami automobilio amortizuotos masės svyravimų kompensavimo modelio ir sukurto pakabos valdymo algoritmo eksperimentiniai tyrimai. Disertacijos tema paskelbti aštuoni moksliniai straipsniai: trys mokslo žurnaluose įtrauktuose į Clarivate Analytics Web of Science duomenų bazę, penki – kituose recenzuojamuose žurnaluose. Disertacijos tema skaityti keturi pranešimai mokslinėse konferencijose.Disertacij