Mohammad Saber Fallah

New model and simulation of Macpherson suspension system for ride control applications

The main purpose of this paper is to propose a new nonlinear model of the Macpherson strut suspension system for ride control applications. The model includes the vertical acceleration of the sprung mass and incorporates the suspension linkage kinematics. This two-degree-of-freedom (DOF) model not only provides a more accurate representation of the Macpherson suspension system for control applications in order to improve the ride quality, but also facilitates evaluation of the suspension kinematic parameters, such as camber, caster and king-pin angles as well as track alterations on the ride vibrations. The performances of the nonlinear and linearised models are investigated and compared with those of the conventional model. Besides, it is shown that the semi-active force improves the ride quality better than active force, while the opposite is true in terms of improving the performance of the kinematic parameters. The results of variations of the kinematic parameters based on the linear model subject to road disturbances are compared with those of a virtual prototype of Macpherson suspension in ADAMS software. The analytical results in both cases are shown to agree with each other.

Optimized Control of Semiactive Suspension Systems Using H

In this paper, an optimized modified skyhook control for the semiactive Macpherson suspension system, equipped with a magnetorheological (MR) damper, is investigated. Using H∞ robust control theory and a 2-D dynamic model, including the kinematics of the suspension system, a robust output feedback controller is developed. The combination of a linear matrix inequality (LMI) solver and genetic algorithm (GA) is adopted to optimize the control gains. Further a 3-D kinematic model is introduced to evaluate the kinematic performance of the controlled suspension system. An inverse dynamic model of the MR damper is obtained based on the experimental results for tuning the input current signal. The effectiveness of the control system is discussed and validated through the simulations and experiment.

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Shimmy vibration is one of the major concerns in the aircraft landing gear design. In this paper, the influence of structural parameters on the shimmy dynamics is analyzed based on a nonlinear dynamical model. A computationally efficient robust model predictive control law is formulated for a linear parameter varying system with guaranteed closed-loop stability. Moreover, an attempt is made to apply the proposed robust model predictive control strategy to suppress the shimmy during the taxiing and landing of an aircraft. Compared with two current robust model predictive controls, the proposed shimmy controller can effectively suppress the shimmy with more efficient computation. To verify the efficiency of the proposed algorithm, the simulation results are presented and discussed. Nomenclature A,B,C = discrete state-space matrices Ac,Bc,Cc = continuous state-space matrices Aj,Bj = discrete state-space matrices ofjth vertex a = half contact length

Robust Control Theory and Current Signal Estimation

In this paper, the performance of a robust control scheme for a Macpherson suspension system is investigated using new dynamic and kinematic models. While the new dynamic model incorporates the kinematics of the suspension in order to have a superior description of the plant dynamics, the three-dimensional kinematic model is used to evaluate the wheel motion subject to controlled force variation. A new definition of the measurement of the wheel–road contact is proposed based on the real function of the control arm. In addition, it is recommended to integrate the vertical displacement of the chassis in the formulation of the control design in order to improve wheel motions. It is shown that the robust semi-active suspension system has superior performance compared with those of a modified skyhook controller system and a passive system.

Robust Model Predictive Control of Shimmy Vibration in Aircraft Landing Gears

In this paper, a new nonlinear model of Macpherson strut suspension system for ride control applications is proposed. The model includes the vertical acceleration of the sprung mass and the motions of the unsprung mass subjected to control arm rotation. In addition, it considers physical characteristics of the spindle such as mass and inertia moment. This two degree-of-freedom (DOF) model not only provides a more accurate representation of the Macpherson suspension system for ride control applications but also facilitates evaluation of the kinematic parameters such as camber, caster and king-pin angles as well as track alterations on the ride vibrations. The performances of the nonlinear and linear models are investigated and compared. Simulation results are presented and discussed.

H ∞ robust control of semi-active Macpherson suspension system: new applied design

Control of vehicle suspension systems has been the focus of extensive work in the past two decades. Many control strategies have been developed to improve the overall vehicle performance, including both ride quality and stability conditions. However, the concerns regarding the wheel motions affecting significantly on the handling and steering are ignored by researchers in the control formulation. A H∞ control methodology is employed to design an active suspension system so that ride quality and wheel motions are improved simultaneously. In addition, a three-dimensional kinematic model of a specific suspension system, namely Macpherson suspension, is developed to study the alteration of those of kinematic suspension parameters which represent the wheel motions. The results show that the proposed robust design provides superior kinematic and dynamic performances compared to those of the passive system.

New nonlinear model of macpherson suspension system for ride control applications

Suspension kinematic parameters such as camber, caster and king-pin angles as well as track width are important in improving handling performance and stability of a vehicle. Using a new model of the Macpherson suspension system, the effects of different hybrid semi-active control strategies on the performance of suspension kinematic parameters and on improvement of ride quality are investigated. The control strategies considered in this work comprise hybrid skyhook-groundhook, modified skyhook and, passive-skyhook controllers. It is shown that although contribution of these controllers on the improvement of ride quality of the vehicle is similar, they affect the performance of the Macpherson suspension kinematic parameters significantly different. Simulation results are presented and discussed. Copyright

H∞ robust control of active suspensions: A practical point of view

In this paper, the driver ride comfort in a heavy vehicle (city bus) is studied under the sky-hook semi-active damping force policy. A new hybrid dynamic model composed of a continuous system and a discrete system are integrated in the current work. The chassis of the vehicle is assumed as the continuous beam supported on the discrete suspension springs and dampers. The driver and the seat are also considered as a discrete vibrating system. The dynamic equations are solved by using the assumed mode method, where the mode shapes of a free-free beam have been employed. The results of the semi-active system are compared with those of the passive one through simulations. The results indicate that the new hybrid dynamic model represents more degrees-of-freedom of the system for driver ride analysis compared to the discrete model. In addition, the results show that the semi-active system has a superior performance in terms of the ride comfort. Copyright

Influence of Different Semi Active Control Strategies on the Performance of Macpherson Suspension Kinematic Parameters

The main focus of the present paper is on the design of a modified sky-hook control of a semi-active Macpherson suspension system by means of H∞ Output Feedback Control (OFC) theory. To this end, a new dynamic model, incorporating the kinematics of the suspension system, is used for the controller design. The combination of a Linear Matrix Inequality (LMI) solver and Genetic Algorithm (GA) is adopted to regulate the static output feedback control gain so that the stability conditions are fulfilled and control objectives are achieved. Meanwhile, a three-dimensional kinematic model of the system is incorporated to investigate the influence of the control force variation on the steering, handling and stability of the vehicle. A geometric relation of the vehicle roll center is employed to study one more extra aspect of the comfort and stability of the vehicle. The results show that the proposed controller improves the kinematic and dynamic performances of the suspension well compared with those of the passive system. Moreover, it is concluded that a superior stability of the vehicle during the cornering can be achieved by adjusting the height of the vehicle roll center passively so that the stability of the vehicle is improved while the forward motion specifications can be modified by an appropriate suspension control design. Copyright