State Dependent Riccati Equation Control of an Active Hydro Pneumatic Suspension System

In this study, a nonlinear active Hydro-Pneumatic (HP) suspension system is modelled. The HP suspension system model is then incorporated into the quarter car model and a nonlinear controller for the vehicle system is developed. A linear structured model with state dependent matrices of the nonlinear quarter car model is derived for use in controller design. A nonlinear control method, State Dependent Riccati Equation control (SDRE) is used to attenuate sprung mass acceleration, suspension deflection, and tire deflection. The performance of the controller is examined in both frequency and time domains. Active HP suspension system is simulated with sinusoidal inputs at discrete amplitudes and frequencies, and the approximate frequency response functions are obtained. The active HP suspension system is simulated with random road inputs and the root mean square values of the responses are used to evaluate the performance of the controller. The results show that the active suspension successfully and simultaneously decreases the sprung mass acceleration, suspension deflection, and tire deflection around body bounce frequency and thus improved ride comfort and road holding are obtained

Araç sürüş konforunun artırılması için pasif titreşim sönümleyicilerinin geliştirilmesi ve test edilmesi

TÜBİTAK MAG15.10.2013Bu çalışmada, doğrusal ve dönel ayarlanabilir titreşim emicilerinin (ATE) ve kaldıraç tipli titreşim izolatörler (KTİ) araç sürüş konforuna etkileri çeyrek araba modeli üzerinde incelenmiştir. ATE'ler, özellikle kendi doğal frekanslarında, sistemin enerjisini kendi üzerine alarak titreşimleri azaltmaktadırlar. Doğrusal ATE'lerin süspansiyon sistemlerine uygulanması kolay olmasına rağmen döner ATE'ler atalet etkilerinin daha fazla olması sebebiyle daha iyi performans göstermektedirler. Elde edilen sonuçlar ATE'lerin tekerlek sıçrama frekansı civarındaki dar bir frekans aralığında sürüş konforunu arttırdığını göstermektedir. ATE’lere ek olarak değişik kütlelere sahip çeşitli KTİ konfigürasyonları incelenmiş ve KTİ'lerin hem araç sıçrama hem de tekerlek sıçrama frekanslarında titreşim genliklerini önemli oranda azalttığı görülmüştür. Ancak bu çalışma sırasında ATE ve KTİ’leri kullanabilmek için önerilen parçalı süspansiyon sistemi araç sürüş konforunu çok önemli bir oranda arttırmıştır. Parçalı süspansiyon sisteminin sürüş konforuna olan olumlu etkilerinin yanında ATE’ler neredeyse etkisiz kalmıştır. KTİ’ler ise parçalı süspansiyon sisteminin gerçekleştirdiği iyileştirmeyi belli frekans bölgelerinde biraz daha arttırdığı gözlemlenmiştir. Dolayısıyla ayarlanmış parçalı süspansiyon sistemi araç sürüş konforunun arttırılması konusunda çok önemli alternatif olarak karşımıza çıkmıştır. Teorik olarak gerçekleştirilen bu çalışmalarının gerçek durumdaki etkilerini gözlemleyebilmek için proje çalışması kapsamında ölçeklendirilmiş bir çeyrek araç test düzeneği tasarlanmıştır. Tasarlanan bu test düzeneği üzerinde teorik çalışmalar neticesinde araç sürüş konforunu arttırdığı belirlenen konfigürasyonlar test edilmiş ve testler sonucunda sürüş konforunda teorik modeller ile elde edilen sonuçlara benzer iyileşmelerin elde edildiği gözlemlenmiştir.In this study, the effects of utilization linear and rotational tuned vibration absorbers (TVA) and lever type vibration isolators (LVI) on vehicle ride comfort are investigated a quarter car model. TVAs decrease the vibrations of the system they are mounted on by absorbing energy of the system especially vibrating frequency equal to the natural frequency of TVA. Even though application of linear TVAs on vehicle suspension is easier, rotational TVAs have better performance due to their increased inertia effect. The results obtained show that TVAs improve ride comfort only at a narrow frequency band around the wheel hop frequency. In addition to TVAs, LVIs with different masses and configurations are as well studied and it is observed that LVIs decrease vibration amplitudes both at the wheel hop and body bounce frequencies. On the other hand, it discovered that the divided suspension system proposed in this study in order to use TVAs and LVIs improved ride comfort significantly, even though TVAs and LVIs are not present. As a result of this significant improvement in ride comfort, the effect of TVAs is observed to be negligible. However, addition of LVIs onto the divided suspension system increase the improvement in ride comfort at certain frequencies, slightly. Therefore, divided suspension system turns out to be an important alternative in increasing vehicle ride comfort. In order to observe the effects these theoretical models, a scaled quarter car experimental setup is as well designed. Theoretical configurations that result in improvement in vehicle ride comfort is tested utilizing this experimental setup where similar improvements as in the case of mathematical models are observed

A fuzzy logic controlled Anti-lock Braking System (ABS) for improved braking performance and directional stability

A simple and effective fuzzy logic controller is designed for an Anti-Lock Braking System (ABS) to improve the braking performance and directional stability of an automobile during braking and steering-braking manoeuvres on uniform and nonuniform (mu-Split) friction Surfaces. The system consists of two controllers working in tandem. The first controller works oil the longitudinal slip, and the second controller is responsible for the side-slip motion control of the vehicle. The fuzzy logic controller is implemented on a four-wheel nonlinear vehicle model with nonlinear lyre behaviour. Simulations are carried out and comparisons are made using the vehicle model with and without the fuzzy logic controlled ABS to assess controller performance

Steering strategies for multi-axle vehicles

The object of this study is to extend 4WS idea to an n-axle vehicle in general and to simulate sonic multi-axle vehicles with the derived strategies in an attempt to determine the best steering strategy. By extending the strategies used for four-wheel steering two-axle vehicles which have been extensively studied in literature, general strategies are established for an n-axle vehicle. Using integrated nonlinear ride and handling models in Matlab & Simulink, it is shown that lateral acceleration and yaw velocity responses can be improved while keeping zero vehicle sideslip angle by steering wheels on intermediate axles

Optimization of suspension parameters to improve impact harshness of road vehicles

This paper illustrates the development and implementation of a parameter optimization methodology to improve impact harshness (IH) of road vehicles. A full ADAMS model of a small commercial vehicle is used as the IH test vehicle. The methodology involves the use of design of experiments methods together with response surface methodology. Significant design parameters affecting IH of the vehicle are first determined by the screening experiments. Once the critical parameters are identified, they are optimized to achieve improvement in the IH by constructing response surface. The optimization results indicate that the selected suspension parameters are capable of improving IH performance of the full vehicle ADAMS model by minimizing longitudinal and vertical acceleration responses. The results also show that considerable improvement can be obtained by using the proposed parameter optimization methodology

Adaptive ride comfort and attitude control of vehicles equipped with active hydro-pneumatic suspension

In this study, an active suspension for combined ride comfort and attitude control of a vehicle equipped with hydro-pneumatic (HP) suspension system is developed. The state-dependent Riccati equation (SDRE) control is employed in the design of the active suspension controller. A detailed sensitivity analysis is performed to examine the effects of the selection of weighting coefficients on the ride comfort and attitude control. According to the results of the sensitivity study, three different sets of fixed weighting coefficients and a fourth set with adaptive weighting coefficients are developed. The adaptive weighting coefficients are implemented by the state constraint in the SDRE formulation. The controller is tuned mainly for ride comfort at low suspension deflections and for keeping the proper vehicle attitude at higher suspension deflections. Simulation results show that the active suspension with the adaptive weighting is successful in improving both ride comfort and the vehicle attitude

Modeling and Simulation of High Speed Railway Vehicle Dynamics

This study aims to provide mathematical model(s) for the simulation of high speed railway vehicles. The dynamic behavior of a high speed train is divided into three uncoupled motions: vertical, lateral, and longitudinal. Two models with different complexities are used to simulate vertical plane response of the vehicle to track vertical irregularities. Different wheel-rail contact formulations are utilized to simulate the lateral plane motion of the vehicle on tangent and curved tracks. For both vertical and lateral dynamics modeling, a single wagon is assumed to simulate the whole vehicle. Finally, wagon interactions are taken into account and the response of a full train to different traction/braking inputs are analyzed. The models are parametric and they are used to develop computer programs to simulate train motion. Using a set of parameters obtained from literature, different case studies were performed to test model functionality. It was observed that 10 degree of freedom model can predict the vertical behavior quite well. In wheel-rail contact modeling, the nonlinearities should be included in the system and the wheel profile with its tread and flange sections should be introduced to obtain accurate results. Finally, in longitudinal dynamics modeling, the stopping time and distance between wagons with respect to braking delay and wagon to wagon connection are examined

Analysis and Design of Passive and Active Interconnected Hydro Pneumatic Suspension Systems in Roll Plane

In this study, analysis and design of a half car model in roll plane with passive and active unconnected and interconnected Hydro-Pneumatic (HP) suspension systems are made. An interconnection configuration with a connection between the piston side oil volume and rod side oil volume of the right and left suspensions, respectively, is considered. The performance of the active unconnected HP and interconnected HP suspension systems are compared in terms of ride comfort and handling. Nonlinear mathematical models are developed for each suspension configuration. A state space model with state dependent coefficients is derived using extended linearization to be used in the controller design. A nonlinear control method, State Dependent Riccati Equation (SDRE) control is used for the active controllers. The active controllers are designed to improve the ride comfort and handling, and to control the attitude and leveling of the vehicle. The performances of the controllers are evaluated by time and frequency domain simulations. Comparisons of the active and passive, unconnected and interconnected HP suspension systems with respect to ride comfort and handling are performed to evaluate the relative advantage and disadvantage of each type. The results illustrate the advantages as well as disadvantages of the active interconnected HP suspension system as compared with the other suspension configurations