Optimal Suspension Research Articles

Optimal Adaptive Active Suspensions for a Full Car Model

SUMMARY In order to present a useful method for designing active suspension of a vehicle, a linear full-car model is used in this investigation. In this model, the dampers of passive system are totally replaced by actuators. The actuators are controlled with optimal full state vector feedback. After determining feedback coefficients, the responses of active and passive systems were compared and it was found that performance of active system is much superior. It is desired that, changes in vehicle parameters would not affect the system's performance and hence should not violate its optimality. In other words, the system should behave adaptively using Model Reference Adaptive Control. The optimally controlled active suspension was used as a model for the active suspension of vehicle. In this way, the suspension of vehicle is controlled in such a way that its output approaches to that of the optimal active model. Thus the suspension should behave just like the optimal one.

Optimal Preview Semiactive Suspension

This paper examines an optimal preview semiactive suspension of a quarter-coach model moving along randomly profiled track. This optimal computer-controlled suspension is designed only to dissipate energy, and is able to use knowledge of track irregularities over a distance L in front of the train. Thus the deformation of the track can be taken into account when calculating the semi-active suspension control law. First, the expression of the optimal preview semiactive control law is established. Then, using a two-degrees-of-freedom quarter-coach model, preview information is shown to improve the behavior of an optimal non-preview semi-active system, which can come close to the performance of an active system.

Non-linear optimal control of a semi-active vehicle suspension system

This paper considers the optimal control of a semi-active vehicle suspension system. Analysis is based on a simple fifth-order mathematical model of the ride dynamics of an automotive suspension. The quarter-vehicle model describes the vertical motions of the vehicle body mass and of a single wheel mass. Although the underlying equations are essentially linear, significant nonlinear effects arises from the dissipative nature of the control actuator, and the inclusion of displacement limiting criteria for the control of suspension and tyre deflections. Optimal suspension control is considered under both free and forced motion of the suspension. New results are given concerning the ability of semi-active suspension to make use of road-surface preview information.

015 Design of Active LQ optimal suspensions for ground transportation vehicles

015 Design of Active LQ optimal suspensions for ground transportation vehicles

Production of die steels by suspension molding

The ranges of application of traditional technologies of powder metallurgy, which include holding under a pressure of (5–7)·102 N/mm2, are limited by the necessity of using expensive press equipment and attachments. This paper investigates the structure and properties of heat-treated die steels produced by a new method of molding — from stabilized suspensions of metallic powders. Optimal suspension compositions and sintering conditions are proposed.

Random Vibration and the Single Degree-of-Freedom Vibratory System: A Symbolic Quantification of Isolation and Packaging Performance

With twenty years of research, active and semi-active systems have been shown to have certain performance advantages over passive suspensions in certain operating regimes. Chalasani and Redfield and Karnopp have shown that, depending on the performance index and weightings, active control improves performance from little to moderately. There are situations where passive control is quite satisfactory and the complexities and cost of more active means may not be warranted. To further the understanding of the tradeoffs involved and the performance potentials of active suspensions, this paper symbolically quantifies the isolation and stroke performance for a one degree-of-freedom vibratory system subject to a stochastic disturbance input acting through the suspension. The system of this paper models that of tracked vehicles and a class of isolation systems quite well. It also gives insight into low and high frequency performance for two degree-of-freedom systems such as a typical suspension model for automobiles, aircraft, and rail vehicles. Because of the nature of the single degree-of-freedom model, issues of handling cannot be readily addressed in this work. The 1 DOF model does not adequately predict dynamic tire forces. The main contributions of this work are the closed form symbolic solutions developed for optimal suspension responsemore » and the demonstration of the marked similarity between the frequency and mean square response of the 1 degree-of-freedom model of this paper and the more involved 2 degree-of-freedom model incorporating a so-called unsprung mass.''« less

Design of Active LQ Optimal Suspensions for Ground Transportation Vehicles

Considerable efforts have been made by many investigators in the synthesis of active suspensions for ground transportation vehicles. In this paper, optimal suspension for a simple two-degree-of-freedom vehicle model is derived using inverse Linear-Quadratic method and the second method of Lyapunov. The purpose of this paper is to investigate energy and hardware requirements of a class of optimal LQ suspensions. It is shown chat the feedback paths of displacement mesurements are not necessary for energy dissipation but for LQ optimality; moreover, the minimization of energy function leads to relative-velocity feedback scheme.

Thermodynamic modeling of hydrothermal synthesis of ceramic powders

A thermodynamic method is proposed for analyzing the hydrothermal synthesis of ceramic materials. The method utilizes standard-state thermodynamic data for solid and aqueous species and a compressive activity coefficients model to represent solution nonideality. The method is used to generate phase stability diagrams for the species that predominate in the system. The stability diagrams can be used to predict the optimum suspension synthesis conditions (i.e., feedstock composition, pH and temperature) for hydrothermal synthesis of ceramic materials. The synthesis of barium titanate and lead titanate are discussed as examples.

Tank depth determination for water radiometric measurements

Abstract To determine the optimum tank depth for the assessment of spectral reflectance from suspended inorganic matter (SIM), a 1·10 m × 0.90 m × 0·67 m black-coated tank was used. A plate with the same coating was constructed to simulate various depths. Different concentrations of bentonite and red silt suspensions were produced and radiometric measurements were performed in the 400-900 nm spectral range. The results showed close relationships between optimum depth and suspension characteristics, e.g., at 5mg/l of bentonite the optimum depth was around 0·63 m and at 140 mg/l it was 0·41 m. For red sill, at 140 mg/1 the optimum tank depth was greater than 0·41 m too. Before each experiment the optimum tank depth must be assessed to produce spectral reflectance of SIM.

Optimal active suspension control based on a half-car model: an analytical solution

Simple yet, in practice, meaningful state-space formulations of the optimal suspension control problem for a half-car 2-D vehicle model are given. Using an efficient equivalent representation, a complete analytical solution of the related fourth-order linear quadratic problem was obtained. The problem structure and associated analytical results are used to deduce generic properties of the optimal solution, which in turn form a basis for global, centralized, and decentralized optimal suspension performance studies. >

Integral and state variable feedback controllers for improved performance in automotive vehicles

An analytical investigation of a half-car model using an integral plus state variable feedback controller for tracking and regulation is performed. The potential benefits of incorporating, actively or semi-actively, such a controller to remedy the inherent problems associated with conventional passive suspensions and active suspensions based on state variable feedback controllers are examined. Both random and deterministic roadway inputs as well as deterministic body force and moment disturbances are used. The results demonstrate that an optimal suspension using an integral plus state variable feedback controller retains both excellent ride and attitude control characteristics.

Optimal Active Suspension Design Using a Frequency-shaping PID Filter

SUMMARY By the incorporation of frequency-shaping into the linear quadratic methods used in active suspension design it is possible to achieve improvements in both body frequency response and road-holding. The use of a PID filter for this purpose also leads to robustness of the system to disturbance forces. Zero steady-state deflections are achieved for applied body loads by the integral action with excellent attenuation of the transient response. The resulting system consists of a hydraulic actuator in parallel with a body spring of arbitrary stiffness and is optimal with equivalent full state feedback.

Application of Transrectal Ultrasonography in Modified Stamey Procedure for Stress Urinary Incontinence

From June 1989 to August 1990, 21 women with genuine stress urinary incontinence were treated with the Gittes procedure combined with transrectal ultrasonography. The urethrovesical junction was well pinpointed on an ultrasonographic image. The strength of suspension providing the optimal posterior urethrovesical angle was changed by each patient. Posterior urethrovesical angles averaged 89.3 ± 9.5 degrees at operation and 93.6 ± 9.5 degrees (mean ± standard deviation) on a postoperative lateral cystourethrogram with the patient straining while in the standing position. An indwelling urethral catheter was removed on postoperative day 1. None of the patients had residual urine of more than 50ml. by 4 days postoperatively. Furthermore, the average maximum urinary flow rates significantly increased from 21.0 ± 7.1ml. per second preoperatively to 26.1 ± 9.8ml. per second postoperatively (p <0.01). Therefore, application of ultrasonography during bladder neck suspension is simple and reliable for determination of the optimal suspension as well as identification of the suspension site.

Optimal suspension performance for 2-D vehicle models

A study is described which was a comprehensive investigation of potential benefits of preview control applied to a linear, two-dimensional (2-D), four-degree-of-freedom, half-car model. The model includes vehicle sprung mass pitch and heave dynamics, and front and rear unsprung masses. By using the discrete-time, optimal Linear Quadratic (LQ) control formulation, it is shown that the preview based on front wheel inputs can contribute to up to 70% reduction of vehicle r.m.s. acceleration, for a given suspension travel, and up to 50% reduction in tire deflection, for a given acceleration level. These improvements are in addition to those already achieved with active suspensions without the preview. The results also indicate that, in view of the available preview times, the preview control is most beneficial at higher speeds and rougher roads.

Simulation of the radiated noise emitted by two coupled structures and application to the acoustic quietening of air conditioning equipment

The challenge of noise control for the nineties will be to leave trial and error methods that are efficient in specific well‐known situations and to tackle the difficult and complex but inevitable problem of structural acoustics and vibration. In order to actually control the noise at the source at the design step, a mode of the radiation of a semicomplex structure has been developed. Based on an analytical approach using a variational method, this model allows prediction of the effects of the boundary conditions [J. Acoust. Soc. Am. (to be published)] as well as stiffeners and added masses with force or moment type of excitation. To go toward industrial applications, the calculus has been extended to the case of a mechanical source of vibration (electric motor, engine) which is attached to a large thin structure that acts as a noise radiator. A theoretical analysis of the problem is presented. The actual force input into the structure is determined as the resultant of both the output impedance of the source and the input impedance of the structure. A quadripole approach for the source assembly enables calculation of the force input, the kinetic energy, the radiation efficiency, and overall sound power. The key novelty of this method lies in its capacity of predicting a priori the radiated noise in various configurations, allowing the designer to choose rationally the best configuration in terms of noise control. This approach has been applied in order to decrease the unwanted noise emitted by air conditioning equipment. A new design has been proposed which led to a 10‐dB improvement. In a general case, guidelines for the optimal suspension design will be presented.

Efficient hybridization of mouse-human cell lines by means of hypo-osmolar electrofusion

The fusion of a mouse-human heteromyeloma with a mouse hybridoma is used as a model to define parameters to generate human hybridomas. Electrofusion of these cells in 300 mosM and 75 mosM solutions showed that strong hypo-osmolar conditions resulted in a dramatic increase in the efficiency of hybridoma formation. In contrast to iso-osmolar electrofusion, a high hybrod yield could be obtained by injection of only a single field pulse. The field strength was adjusted in proportion to the increased size of the cells in hypo-osmolar solutions. Hypo-osmolar electrofusion allowed the generation of approximately 0.45% hybrids at a suspension density of 1.75·10 5 mouse-human cells/ml corresponding to an input number of 3.5·10 4 mouse-human cells. A further increase in the efficiency of hybridoma formation to about 0.6% was achieved by cell alignment in an alternating field of modulated field strength. Experiments in which the total cell number per fusion chamber was decreased at constant optimum suspension density showed that a further increase in the efficiency of hybridoma formation in hypo-osmolar solution was not possible because of the increasing influence of the heterogeneity of the cell lines with decreasing cell number. The results allow the conclusion that hypo-osmolar electrofusion is a potential tool to enhance succesful immortalisation of human B lymphocytes.

Optimal Linear Active Suspensions with Multivariable Integral Control

SUMMARY In this paper, an optimal suspension system is derived for a quarter-car model using multivariable integral control. The suspension system features two parts. The first part is an integral control acting on suspension deflection to ensure zero steady-sate offset due to body and maneuvering forces as well as road inputs. The second is a proportional control operating on the vehicle system states for vibration control and performance improvement. The optimal ride performance of the active suspensions based on linear full-state feedback control laws with and without integral control together with the performance of passive suspensions are compared.

Coupling effects between a lumped vibrational source of finite impedance and a plane radiator

A typical situation in structural acoustics and vibrations is the case of a mechanical source of vibrations attached to a large, thin structure (radiator). In general, the force input into the structure, responsible for undesired vibrations of, and radiation from, the structure, is the resultant of both the output impedance of the source and the input impedance of the structure. A theoretical analysis of the problem is presented in the case of a lumped mechanical source composed of masses, springs, and dampers, with one single attachment point to a baffled, thin, rectangular, plane structure. The coupling assumes only pure transverse force transmission into the structure. A quadrupole approach for the source assembly and a variational approach for the motion of the structure allow, respectively, the source output impedance and the structure input impedance to be calculated in a variety of configurations. The force input into the structure, kinetic energy of the structure, and radiation of sound from the structure can then be derived. It is shown how the natural frequencies of the combined system can be found from the natural frequencies of the source and structure decoupled. Numerical results are presented for the particular application of optimal suspension design of mass‐type source. [Dr. I. Michaluk is acknowledged for fruitful discussions.]

Optimal Linear Active Suspensions with Vibration Absorbers and Integral Output Feedback Control

SUMMARY The bandwidth of the body response to a road input in an active suspension may be considerably reduced if the axle motions are independently controlled and if, at the same time, the effects of static and dynamic loads are counteracted by integral action in the body force control system. The paper presents a further application of the Ferguson-Rekasius method, leading to optimal output control with incomplete state feedback. To achieve narrow bandwidth body response the support springs are replaced by hydraulic actuators, and vibration absorbers or active wheel dampers are employed for the control of the axle motions. Active wheel damping is the more effective and gives good results. Proportional-plus-integral control action is shown to reduce the transient body displacements due to external forces.

An Approach Toward the Optimal Semi-Active Suspension

In this paper, a two-degree-of-freedom model of a semi-actively suspended vehicle is used as a starting point in the design of an optimal suspension. The optimization is performed with respect to a quadratic performance index reflecting suspension design constraints and ride quality requirements. Two closely related mathematical descriptions of the model are given, one leading to a linear and the other to a bilinear system of differential equations, with an additional inequality constraint reflecting the passivity of the semi-active device. Since the resulting stochastic optimization problem does not allow for a closed-form analytical solution, a numerical method is proposed as an approximate solution. The justification for the method is based on a recent existence theorem from stochastic optimal control theory. Illustrative simulation results of the optimization are presented.