T-S Fuzzy Model Based H

This paper presents a double loop controller for a 7-DoF automobile electrohydraulic active suspension via T-S fuzzy modelling technique. The outer loop controller employs a modified H-infinity feedback control based on a T-S fuzzy model to provide the actuation force needed to ensure better riding comfort and handling stability. The resulting optimizing problem is transformed into a linear matrix inequalities solution issue associated with stability analysis, suspension stroke limit, and force constraints. Integrating these via parallel distributed compensation method, the feedback gains are derived to render the suspension performance dependent on the perturbation size and improve the efficiency of active suspensions. Adaptive Robust Control (ARC) is then adopted in the inner loop design to deal with uncertain nonlinearities and improve tracking accuracy. The validity of improvements attained from this controller is demonstrated by comparing with conventional Backstepping control and a passive suspension on a 7-DoF simulation example. It is shown that the T-S fuzzy model based controller can achieve favourable suspension performance and energy conservation under both mild and malevolent road inputs

An Alternative Nonlinear Lyapunov Redesign Velocity Controller for an Electrohydraulic Drive

This research aims at developing control law strategies that improve the performances and the robustness of electrohydraulic servosystems (EHSS) operation while considering easy implementation. To address the strongly nonlinear nature of the EHSS, a number of control algorithms based on backstepping approach is intensively used in the literature. The main contribution of this paper is to consider an alternative approach to synthetize a Lyapunov redesign nonlinear EHSS velocity controller. The proposed control law design is based on an appropriate choice of the control lyapunov function (clf), the extension of the Sontag formula and the construction of a nonlinear observer. The clf includes all the three system variable states in a positive define function. The Sontag formula is used in the time derivative of our clf in order to ensure an asymptotic stabilizing controller for regulating and tracking objectives. A nonlinear observer is developed in order to bring to the proposed controller the estimated values of the first and the second time output derivatives. The design, the tuning implementation and the performances of the proposed controller are compared to those of its equivalent backstepping controller. It is shown that the proposed controller is easier to design with simple implementation tuning while the backstepping controller has several complex design steps and implementation tuning issue. Moreover, the best performances especially under disturbance in the viscous damping are achieved with the proposed controller

Design of a denoising hybrid fuzzy-pid controller for active suspension systems of heavy vehicles based on model adaptive wheelbase preview strategy

Active suspension is an effective approach to improve vehicle performance, and it is of great importance to attenuate the vibration of the rear part of heavy vehicles with freight. This paper proposes a new hybrid fuzzy proportional-integral-derivative (PID) controller with model adaptive wheelbase preview and wavelet denoising filter in an active suspension system for heavy vehicles with freight. A half vehicle model is first built, followed with the construction of the road excitation profiles of the shock and vibration pavement. After the design and implementation of the control method, four performance indices of the vehicle are evaluated. To verify the effectiveness of the proposed method, the control performance of the integrated controller and the separate function of every single controller are evaluated respectively. Numerical results show that the integrated control algorithm is superior to the single controllers and is effective in improving the vehicle performance as compared with other methods. Moreover, the wavelet denoising filter is shown to be an effective way to improve the vehicle performance and enable the stability of the system against noise

Innovative magnetorheological devices for shock and vibration mitigation

Vibration and impact protection have been a popular topic in research fields, which could directly affect the passengers’ and drivers’ comfort and safety, even cause spines fracture. Therefore, an increasing number of vehicle suspensions and aircraft landing gears are proposed and manufactured. Magnetorheological fluids (MRFs), as a smart material, are growly applied into the above device owing to its unique properties such as fast response, reversible properties, and broad controllable range, which could improve the vibration/impact mitigation performance. MRF was utilized to achieve adaptive parameters of the vehicle suspensions by controlling the magnetic field strength of the MRF working areas. Generally, the magnetic field is provided by a given current, subsequently, it would consume massive energy from a long-term perspective. Thus, a self-powered concept was applied as well. This thesis reports a compact stiffness controllable MR damper with a self-powered capacity. After the prototype of the MR damper, its property tests were conducted to verify the stiffness controllability and the energy generating ability using a hydraulic Instron test system. Then, a quarter-car test rig was built, and the semi-active MR suspension integrated with the self-powered MR damper was installed on a test rig. Two controllers, one based on short-time Fourier transform (STFT) and a classical skyhook controller was developed to control the stiffness. The evaluation results demonstrate that the proposed MR damper incorporated with STFT controller or skyhook controller could suppress the response displacements and accelerations obviously comparing with the conventional passive systems

Commande hybride d'un système à suspension active

Cette thèse traite la modélisation, d’un système de suspension active électrohydraulique, du développement des lois de commande et leur implantation en temps réel pour des fins de validation. Les stratégies de contrôle employées et développées utilisent des approches de commande linéaire, nonlinéaire, et de commande adaptative avec des structures simples ou hybrides. Dans le cadre de cette thèse, nous avons développé une méthode de commande nonlinéaire hybride pour contrôler la position et la force appliquées sur un banc de suspension active représentant la suspension active d’un véhicule. La structure hybride combine deux contrôleurs nonlinéaires en utilisant deux filtres passe bas. Cette structure consiste en une loi de commande nonlinéaire qui contient des fonctions et des gains variables. Les contrôleurs sont développés en utilisant le mode de glissement pour sa robustesse malgré le broutement (chattering) produit dans la loi de commande. Une chose importante à traiter en contrôle de mode de glissement est la réduction du broutement. La loi d’atteint exponentielle est une des techniques existant pour réduire le broutement dans la loi de commande nonlinéaire. La technique a été testée en simulation ainsi qu’en temps réel pour des fins de validation dans cette thèse. Pour améliorer la performance du contrôleur proposé dans le paragraphe précédent, nous avons ajouté un autre contrôleur de logique floue basé sur les surfaces de glissement pour les tests de validation. Dans le contrôleur de logique floue, les entrées sont les surfaces de glissement de la position et de la force qui sont calculés instantanément dans le système. Le contrôleur de logique floue varie les gains des filtres efficacement pour améliorer la performance de contrôleur proposé utilisé dans la structure hybride. La stabilité de structure hybride est renforcée par la stabilité de chaque contrôleur employé dans cette structure. La popularité de contrôleur PID nous a motivé à l’intégrer dans la structure hybride. Vu que le contrôleur PID est facile à intégrer dans les applications industrielles et dans les systèmes embarqués, un contrôleur hybride basé sur des contrôleurs PID est construit et testé pour déterminer une force désirée en gardant la position dans ses limites. La structure hybride composée des contrôleurs PID et contrôleurs de mode de glissement a prouvé sa validité à travers des séries de tests en simulation et en temps réel. Les résultats montrent qu’un contrôleur hybride peut réduire la perturbation exercée sur un système à suspension active et suivre une trajectoire de force désirée générée à partir des paramètres du système. Ce double aspect ne peut être réalisé par un contrôleur simple et même un contrôleur nonlinéaire. Les contrôleurs simples sont faits pour réaliser un seul objectif (force ou position) et parfois garder des variables dans leurs limites. En revanche, la structure hybride est devenue de plus en plus populaire pour les applications multitâches surtout en robotiques. Autrement dit, le contrôle composé de deux contrôleurs a prouvé son efficacité dans plusieurs domaines. Dans le même sens, un contrôleur PID dual loop (PIDDL) a été développé et présenté sous une forme adaptative à travers des fonctions adaptatives pour contrôler la position de banc d’essai à suspension active. Le PIDDL pourrait être intégré dans la structure hybride pour avoir une nouvelle structure basée sur un contrôleur considéré comme une extension de contrôleur PID. Des contrôleurs à logique flou sont employés sous une structure adaptative avec des retours des sorties des même contrôleurs pour mettre à jour les gains essentiels de contrôleurs PID et PIDDL. Le contrôleur PIDDL avec des gains variables a été testé et validé à travers une série des comparaisons avec le PID et d’autres contrôleurs. Les résultats obtenus ont prouvé la validité du contrôleur proposé en surpassant les autres contrôleurs en termes de performance

Design and investigation of PA controller for driving nonlinear electro hydraulic actuator with new active suspension system model

Fully active electrohydraulic control of a quarter-car test rig is considered from both a modelling and experimental point of view. This paper develops a nonlinear active hydraulic design for the active suspension system, which improves the inherent trade-off between ride quality and suspension travel. The novelty is in the use of pole assessment controller to drive a nonlinear active suspension with a new insight into the model through consideration of a new term, friction forces. Therefore, this model has taken into account the dynamic inclination angle

Automotive suspension system modelling and controlling

In both academic and industrial fields, suspension system modelling and associated control design influence vehicle response. Ideal hydraulic force models have been used in active suspension studies for decades, but few studies have investigated hydraulic effects, which are the core of system force generation. Accurate mathematical subsystem modelling is essential in representing physical subsystems and enhancing design estimation control. This thesis details the mathematical modelling of both passive and active suspension and controller design for a quarter-car test rig. When using a conventional passive model, a significant difference between the experimental and simulation results was found for improved modelling of body movements. This led to an investigation in how to resolve this issue, accordingly, the consideration of a new term (friction force) was researched. Establishing a nonlinear friction force became a vital aspect of this work. In addition, emphasis was placed on hydraulic modelling and unknown model parameters that were experimentally identified. This experimental work is unique and helpful for advancing knowledge of any system. A new approach to implementing the friction force was used to identify the system through the transformation of a ¼ car model to one Degree of Freedom (DOF) and two-DOF models. This reduced the model complexity and allowed the parameters to be identified from a series of transfer functions linking vehicle parts and the hydraulic models. Simulation and experimental results were then compared. The hydraulic component model is crucial to the formulation of accurate active control schemes. Full-state feedback controls were realised by Pole-Assignment (PA) and Linear Quadratic (LQ) optimal method. Simulation results suggest that even though the performance of active suspension designed by the PA method is superior to that of passive suspension, it still possesses a design constraint, similar to a passive system, as the design is a compromise between the effects of natural frequency and transmissibility. With a different design concept, the LQ method provided a better solution as it reduced energy consumption by 65% and effectively shifts the dominant natural frequency to a very low-frequency range. Thus, allowing the damping rate to be increased to its critical value with the smallest effect on transmissibility. iv It was estimated for experimental work that the identified model with the LQ controller might be used to predict the dynamic responses of the actual system within a certain range of the design parameters due to the considerable difference between the initial condition of the test rig and the linearised operating design. The servovalve produced issues that did not allow validation of the controller. Both simulation and experimental results, with several conditions, showed consistent agreement, between experimental and simulation output, consequently confirming the feasibility of the newly approved model for passive and active suspension systems that accounted for the actual configuration of the test rig system. These models, that subsequently implemented the nonlinear friction forces that affect the linear supported body bearings, are entirely accurate and useful. The nonlinear friction model captures most of the friction behaviours that have been observed experimentally. Additionally, the models of the nonlinear hydraulic actuators, covered by the dynamic equation for the servovalve, are moderately precise and practical. The suggested Proportional Integral (PI) control successfully guided the road hydraulic actuator and validated the control strategy. The suggested PA and LQ controllers for active systems successfully guided the system to achieve the targets. Ride comfort and handling response are close to that expected for the passive suspension system with road disturbances, whereas there were clear response enhancements for the active system

Advanced robust control strategies of mechatronic suspensions for cars

Two novel mechatronic suspensions for road vehicles are studied in this thesis: the Series Active Variable Geometry Suspension (SAVGS) and the Parallel Active Link Suspension (PALS). The SAVGS and the PALS complement each other in terms of the vehicle categories they serve, which range from light high-performance vehicles (the Grand Tourer) to heavy SUV vehicles, respectively, based on the sprung mass and the passive suspension stiffness. Previous work developed various control methodologies for these types of suspension. Compared to existing active suspension solutions, both the SAVGS and the PALS are capable of low-frequency chassis attitude control and high-frequency ride comfort and road holding enhancement. In order to solve the limitation of both SAVGS and PALS robustness, mu-synthesis control methodologies are first developed for SAVGS and PALS, respectively, to account for structured uncertainties arising from changes to system parameters within realistic operating ranges. Subsequently, to guarantee robustness of both low-frequency and high-frequency vehicle dynamics for PALS, the mu-synthesis scheme is combined with proportional-integral-derivative (PID) control, employing a frequency separation paradigm. Moreover, as an alternative robustness guaranteeing scheme that captures plant nonlinearities and road unevenness as uncertainties and disturbances, a novel robust model predictive control (RMPC) based methodology is proposed for the SAVGS, motivated by the promise shown by RMPC in other industrial applications. Finally, aiming to provide further performance stability and improvements, feedforward control is developed for the PALS. Nonlinear simulations with a set of ISO driving situations are performed to evaluate the efficiency and effectiveness of the proposed control methods in this thesis.Open Acces