Showing papers on "Skyhook published in 2009"

Vibration Isolation of Precision Payloads: A Six-axis Electromagnetic Relaxation Isolator

Abstract: This paper describes a passive six-axis vibration isolation system for space applications. The system consists of a Stewart platform with cubic architecture; each leg is equipped with an electromagnetic transducer connected to a RL circuit. The system behaves like a relaxation isolator and its transmissibility exhibits an asymptotic decay rate of ―40 dB/decade. The performances are very similar to that of an active isolator based on a skyhook controller.

Self-powered and sensing control system based on MR damper: presentation and application

Abstract: A new self-powered and sensing semi-active control system based on magnetorheological (MR) damper is presented. The system includes four key parts: a rack and pinion mechanism, a linear permanent magnet DC generator, a current adjustment MR damper, and a control circuit. Numerical simulations for seismic protection of elevated bridges equipped with this system excited by two historical earthquakes are conducted. Linear quadratic regulator (LQR) is used for the design of ideal active control system. LQR-based clipped optimal control as well as skyhook control is used to command a MR damper in both the semi-active control with external power and self-powered semi-active control. It is shown that five strategies (ideal active control, two semi-active controls and two self-powered semi-active controls) have similar control performance in pier response as well as bearing response. It is noticed that only one accelerometer is needed to monitor the response of the deck to realize the self-powered skyhook control, which greatly simplifies the classical semiactive vibration control system based on MR damper.

Feasible control solutions of the ASCE benchmark cable-stayed bridge

Abstract: A benchmark model of a cable-stayed bridge has attracted in the last years the attention of the control community. In this paper robust feasible solutions are investigated. As a first step passive devices have been applied to the bridge numerical model between the deck and the piers. Further, an open-loop semi-active improvement of the passive control system is implemented, as suggested by the preliminary results. Finally, an innovative decentralized solution for a semi-active scheme in closed-loop configuration is introduced in the bridge model; the results are here compared, in terms of structural responses, with an active setting, defining an optimal target. The control algorithm adopted for the semi-active devices in the closed-loop setting is an on/off skyhook one with two force levels. The devices adopted in the numerical simulations have dissipative properties and, when managed in a semi-active arrangement, act as a 3D smart control system. The device force displacement relationship fits the results of laboratory tests during the characterization process of an electro-inductive device. The excitation considered in the benchmark problem is essentially the seismic one. A digression to the wind excitation is introduced in the numerical model so as to analyze the control system reaction. The aim of this study is to suggest control solutions for cable-stayed bridges with the common sense to research the best performance, though maintaining robustness, simplicity and feasibility. Copyright © 2009 John Wiley & Sons, Ltd.

Semi-active suspension system simulation using Simulink

Abstract: This paper describes a simulation design procedure aimed to achieve improved performance of the vehicle semi-active suspension. The issues related to the design of vehicle models with skyhook control are discussed. Three basic models with linear parameters are explained: quarter-, half- and full-car. The road profile is generated from a spatial power spectral density (PSD) to represent a typical road (based on ISO 8608 classification). The normalized root-mean-square values of sprung mass acceleration and tyre load forces are used to assess the vehicle ride comfort and handling performance based on five benchmark road profiles employed in industrial tests.

Static Output Feedback Control for Electrohydraulic Active Suspensions via T–S Fuzzy Model Approach

Abstract: The paper presents a juzzy static output feedback controller design approach for vehicle electrohydraulic active suspensions based on Takagi―Sugeno (T―S) fuzzy modeling technique. The T―S fuzzy model is first applied to represent the nonlinear dynamics of an electrohydraulic suspension. Then, the fuzzy static output feedback controller is designed for the obtained T―S fuzzy model to optimize the H ∞ performance of ride comfort through the parallel distributed compensation scheme. The sufficient conditions for the existence of such a controller are derived in terms of linear matrix inequalities (LMIs) with an equality constraint. A computational algorithm is presented to convert the equality constraint into a LMI so that the controller gains can be obtained by solving a minimization problem with LMI constraints. To validate the effectiveness of the proposed approach, two kinds of static output feedback controllers, which use suspension deflection and sprung mass velocity, and suspension deflection only, respectively, as feedback signals, are designed. It is conjirmed by the simulations that the designed controllers can achieve good suspension performance similar to that of the active suspension with optimal skyhook damper.

Performance evaluation on vibration control of MR landing gear

Abstract: This paper is concerned with the applicability of the developed MR damper to the landing gear system for the attenuating undesired shock and vibration in the landing and taxing phases. First of all, the experimental model of the MR damper is derived based on the results of performance evaluations. Next, a simplified skyhook controller, which is one of the most straightforward, but effective approaches for improving ride comport in vehicles with active suspensions, is formulated. Then, the vibration control performances of the landing gear system using the MR damper are theoretically evaluated in the landing phase of the aircraft. A series of simulation analyses show that the proposed MR damper with the skyhook controller is effective for suppressing undesired vibration of the aircraft body. Finally, the effectiveness of the simulation results are additionally verified via HILS (Hardware-in-the-loop-simulation) method.

A Comparison of Suitable Control Methods for Full Vehicle with Four MR Dampers, Part I: Formulation of Control Schemes and Numerical Simulation

Abstract: Due to significant nonlinearity of magnetorheological (MR) suspension, one of the main challenges in the application of this technology is to develop appropriate control algorithms. The main purpose of this study is to identify a suitable control method for semi-active isolation in MR suspension application. The semi-active control schemes include the following: a new proposed intelligent control scheme, Human Simulated Intelligent Control (HSIC) and three representative semi-active control schemes that are skyhook control, hybrid control algorithm, and fuzzy logic control. A full-car dynamic model considering the effect of roll motion is adopted as the baseline model for our analysis. After deriving the governing motion equations of the proposed dynamic model, the HSICler and other three controllers with nonlinearity of MR dampers are formulated. Then each control policy is applied to the baseline model equipped with four MR dampers. The performances of each control algorithm under various road condition...

Comparison between Skyhook and Minimax Control Strategies for Semi-active Suspension System

Abstract: This paper describes the development, modeling, and testing of skyhook and MiniMax control strategies of semi-active suspension. The control performances are investigated using Matlab/Simulink [1], with a two-degree-of-freedom quarter car semiactive suspension system model. The comparison and evaluation of control result are made using software-in-the-loop simulation (SILS) method. This paper also outlines the development of a hardware-inthe-loop simulation (HILS) system. The simulation results show that skyhook strategy can significantly reduce the resonant peak of body and provide improvement in vehicle ride comfort. Otherwise, MiniMax strategy can be employed to effectively improve drive safety of vehicle by influencing wheel load. The two strategies can be switched to control semi-active suspension system to fulfill different requirement of vehicle in different stages. Keywords—Hardware-in-the-loop simulation, Semi-active suspension, Skyhook control, MiniMax control.

Cost-Effective Skyhook Control for Semiactive Vehicle Suspension Applications

Abstract: Skyhook control, which is now widely applied to vehicle suspension control, requires two sensors to measure sprung mass acceleration and relative displacement, respectively. In the practical implementation, these two measurement signals are converted into corresponding velocities; then per the skyhook control policy the velocities are employed to decide the desired damping level; finally the damping control signal will be sent to a controllable damper to reduce vibration. For automotive application, the cost as well as reliability is always one of the primary concerns. In this paper, a new scheme is proposed to simplify skyhook control implementation by eliminating one sensor instead of traditionally using two. This design can reduce cost and improve system reliability by reducing the semiactive system complexity. According to a quarter car model, the idea is expatiated on through analysis of the phase relationship between the two velocities that are essential for skyhook control. Then the estimation of the relative velocity from the sprung mass acceleration is formulated. A cost effective skyhook control is derived from using only one accelerometer, and the effectiveness of this new skyhook control approach is demonstrated with ride control through a simulation study of a full car suspension system with application of magneto-rheological (MR) dampers.

Application of LQR control theory to the design of modified skyhook control gains for semi-active suspension systems

Abstract: The control objective in this paper is to improve the ride comfort and the road holding ability, while maintaining the constraint on suspension deflection, for the semi-active suspension system equipped with a MR damper and a suspension relative displacement sensor. Two optimal control strategies are investigated: First, the linear quadratic regulator (LQR) control is investigated from the perspective of finding what optimal control forces are needed. Second, a modified skyhook control law is investigated for a semi-active suspension equipped with an MR damper. The parameters of the modified skyhook control are determined by minimizing the difference between the modified skyhook control forces and the optimal forces obtained by the LQR control using a minimum norm criterion. Furthermore, the use of filters to estimate the state variables is proposed. Simulation results are provided.

A comparative ride performance and dynamic analysis of passive and semi-active suspension systems based on different vehicle models

Abstract: Vehicle models used to evaluate performance and dynamic behaviour are either discrete models, which includes quarter, half, and full car models, or continuous models using finite element modelling. In this work our focus will be on discrete models, which have more popularity with ground vehicle analysts owing to their shorter computational time and lower cost compared with continuous models. In this paper, ride comfort, suspension displacement and road-holding performances are compared for three different models – quarter (Q), half (H) and full (F) car models. In each model, semi-active system controls, namely skyhook, groundhook and hybrid controls, are used along with the conventional passive system. The analysis covers both transient and steady-state responses in the time domain and transmissibility response in the frequency domain. Results show that while the responses give generally the same trend, the simpler model gives significantly higher responses.

Fuzzy Logic Control for active suspension of a Non-Linear Full-Vehicle Model

Abstract: This paper describes the suspension control of a seven-degree of freedom (7-DOF) Non-Linear Full-Vehicle Model. The system is controlled by a Fuzzy Logic Controller (FLC) using Skyhook theory. The proposed model takes into consideration heave, pitch and roll motions of the vehicle. Multiple road input effects on the vehicle are evaluated through simulations. The simulation results show that the developed fuzzy controller improves ride comfort without sacrificing safety.

A Comparison of Suitable Control Methods for Full Vehicle with Four MR Dampers Part II Controller Synthesis and Road Test Validation

Abstract: The significant non-linearity and uncertainty in the behavior of magnetorheological (MR) suspension systems has been one of the main challenges in the application of this technology in the development of appropriate control algorithms. Here, four model-free control algorithms studied theoretically in prior work are applied to a full vehicle featuring four MR dampers and evaluated through road test to identify the most suitable control algorithm. The four model-free control algorithms include the well-known skyhook control, the hybrid control, the fuzzy logic control, and a newly proposed intelligent control algorithm, the human simulated intelligent control (HSIC). As the first step, four MR dampers (two for the front parts and two for the rear parts) are designed and manufactured based on the damping-force levels and mechanical dimensions of stock dampers of the test vehicle. After experimentally measuring the magnetic-field-dependent force property and controllability, a precise inverse model of MR damp...

Modified skyhook control of a suspension system with hydraulic strut mount

Abstract: In this paper, a mathematical model of a quarter-car suspension system equipped with a hydraulic strut mount is investigated. It is assumed that only suspension deflection is measured. In contrast to the conventional suspension model, in which the effect of a strut mount is not included, damping-spring characteristics of the hydraulic strut mount have been added. Then a modified skyhook control for the proposed model is investigated in achieving both the ride quality and the handling performance. An algorithm to find the optimal skyhook parameters using root mean squares value of the sprung mass acceleration, the suspension deflection, and the tire deflection is introduced. Furthermore, a Kalman filter is introduced to estimate the required state variables for skyhook control.

Optimizing active control scheme of high-speed pantograph

Abstract: A novel control scheme for the active suspension in a 4-DOFs pantograph is presented here. The concepts of force cancellation, Skyhook damper and track-following spring are jointly applied to establish an active vibration control system. A force cancellation control scheme is used to isolate the sprung masses. Skyhook damper is employed to form the sprung mass. Track-following springs are applied for the sprung mass to follow the variable of contact line. For efficiency, the process for design of the active suspension parameters of pantograph using the constrained multiobjective evolutionary algorithm is employed to search for the parameters like damping ratio and spring constant to achieve an optimum, trade off peak of contact force, suspension displacement and inertia force. Computer simulations are performed using MATLAB to verify the proposed control scheme model.

Analysis of semi-active suspension systems for four-axles off-road vehicle using half model

Abstract: Handling and ride quality are affected by many factors, including high-frequency vibrations, body booming, body roll and pitch motion, vertical motion by the suspension system and frequency vibration transmitted from the road input excitations. This article focuses on the most significant vibration source that affects handling and ride quality, which is the suspension system. Passive suspension has been taken as the starting point of this work, in which we discuss the model in context. Semi-active suspension systems are introduced with the aim of exploring the performance of the system compared with passive suspension. Several control policies of semi-active systems, namely, skyhook, ground-hook and hybrid controls, are presented. Their ride comfort, suspension displacement and roadholding performances are analysed and compared with passive systems. The analysis covers both transient and steady-state responses in the time domain and transmissibility response in the frequency domain. The results show that the hybrid control policy yields better comfort than a passive suspension, without reducing the road-holding quality or increasing the suspension displacement for a typical off-road vehicle. The hybrid control policy is also shown to provide a better compromise between comfort, road-holding and suspension displacement than the skyhook and ground-hook control policies.

Ride comfort assessment in off road vehicles using passive and semi-active suspension

Abstract: Vehicles handling and ride comfort are essential subject because these vehicles operate at different environments. Improving the comfort ability enables the drivers to derive for a long time at critical situations with full activity. This paper deals with dynamics and control policies analysis of semi-active suspension systems for off-road vehicles. Three configurations of these vehicles; 2-axle, 3-xle and 4-axles have been studied and their performances are compared. The application of several control policies of semi-active suspension system, namely skyhook; ground-hook and hybrid controls have been analyzed and compared with passive systems.The results show that the hybrid control policy yields better comfort than a passive suspension, without reducing the road-holding quality or increasing the suspension displacement. The hybrid control policy is also shown to be a better compromise between comfort, road-holding and suspension displacement than the skyhook and ground-hook control policies. Skyhook control generally improves sprung mass responses while at the same time increase unsprung mass responses. On the other hand, ground-hook control generally improves unsprung mass responses at the expense of the sprung mass responses. Ground-hook control also found to take longer time to settle in transient state response. Results show an improvement in ride comfort and vehicle handling using 4-axle over 3-axle and 2-axle when emphasis is placed on the response of the vehicle body acceleration, suspension and tyre deflection.

Transient and steady state dynamic analysis of passive and semi-active suspension systems using half-car model

Abstract: Several control policies of semi-active system, namely skyhook, groundhook and hybrid controls are presented using a half-car model, as a continuation of the previous work on quarter-car model. Their ride comfort, suspension displacement and road-holding performances are analysed and compared with passive system. The analysis covers both transient and steady state responses in time domain and transfer function in frequency domain. The results show that the hybrid control policy yields better comfort than a passive suspension, without reducing the road-holding quality or increasing the suspension displacement for typical passenger cars. The hybrid control policy is also shown to be a better compromise between comfort, road-holding and suspension displacement than the skyhook and groundhook control policies.

A system engineering approach for the design optimization of a hydraulic active suspension

Abstract: A procedure for the optimal design of an active suspension with skyhook control scheme is presented. A 15 Degrees of Freedom vehicle model has been implemented and, once correlated with test data, the control strategy has been plugged in and tuned in function of the vehicle manufacturer target requirements. Achievable performances of the vehicle equipped with active components have been estimated through the implementation of the “quarter car model”, successively extended towards the full controlled vehicle. The active damper system, to be manufactured by Tenneco, has been separately modeled and the suspension design definition has been optimized with reference to performance achievements and power consumption requirements.

Switched Stiffness Vibration Controllers for Fluidic Flexible Matrix Composites

Abstract: This paper investigates semi-active vibration control using Fluidic Flexible Matrix Composites (F2 MC) as variable stiffness components of flexible structures. The stiffness of F2 MC tubes can be dynamically switched from soft to stiff by opening and closing an on/off valve. Fiber reinforcement of the F2 MC tube changes the internal volume when externally loaded. With an open valve, the fluid in the tube is free to move in or out of the tube, so the stiffness is low. When the valve is closed, the high bulk modulus fluid resists volume change and produces high stiffness. The equations of motion of an F2 MC-mass system is derived using a 3D elasticity model and the energy method. The stability of the unforced dynamic system is proven using a Lyapunov approach. To capture the important system parameters, nondimensional full order and reduced order models are developed. A Zero Vibration (ZV) state switch technique is introduced that suppresses vibration in finite time, and is compared to conventional Skyhook semiactive control. The ITAE performance of the controllers is optimized by adjusting the open valve flow coefficient. Simulation results show that the optimal ZV controller outperforms the optimal Skyhook controller by 13% and 60% for impulse and step response, respectively.Copyright © 2009 by ASME

Controlling active cabin suspensions in commercial vehicles

Abstract: The field of automotive suspensions is changing. Semi-active and active suspensions are starting to become viable options for vehicle designers. Suspension design for commercial vehicles is especially interesting given its potential. An active cabin suspension for a heavy-duty truck is considered, consisting of four ideal actuators with parallel springs, one acting on each corner of the cabin. The main question is how to control this suspension such that it gives optimal comfort when driving in a straight line, but still follows a specified compensation strategy when cornering, braking or accelerating. The proposed controller uses modal input-output-decoupling. Each of the modes has a separate controller including: a skyhook part for enhanced comfort; and an event part for attitude control. The proposed control strategy is tested in simulation using a validated tractor semi-trailer model with idealized actuators. It is shown that driver comfort can be greatly enhanced, without impairing the attitude behavior of the cabin. Furthermore, in contrast to what is known from quarter car analysis, it is shown that adding passive damping is highly desirable.

Performance robustness of a magnetorheological seat suspension to temperature variations using skyhook control

Abstract: The harmonic steady-state responses of an MR seat isolator, designed and fabricated at the University of Maryland for the driver/commander seat of the Expeditionary Fighting Vehicle (EFV), are measured over a temperature range from 100°C to 1000°C, and the damper behavior is characterized using a variant of the nonlinear Bingham plastic model. The effect of damper self-heating on the model parameters is investigated and the trends with temperature variation are presented. Numerical simulations are carried out to investigate seat isolation performance across a broad frequency spectrum as temperature and payload vary. Conclusions are drawn about the performance robustness to temperature variations of the semi-active skyhook control algorithm typically utilized in vibration isolation problems.

A hierarchical controller for the vibration of an automotive suspension system via magnetorheological dampers

Abstract: Reducing the vibration of an automotive magnetorheological (MR) suspension system can contribute greatly to enhancing vehicle performance. However, it is difficult to design a control system that depends on a complicated whole-vehicle vibration model. This paper proposes a hierarchical controller that consists of a control level and a coordination level for heave, roll, and pitch vibration control of a vehicle with an MR suspension system. On the control level, a local fuzzy controller is designed for each quarter-vehicle MR suspension system, based on a hybrid control strategy of skyhook control and groundhook control. On the coordination level, a coordination controller is designed to tune four local independent fuzzy controllers by adjusting their output parameters on the basis of system feedback. A test and control system for MR suspensions is set up and implemented on a minibus equipped with four controllable MR dampers. The results on random rough roads confirm that the hierarchical controll...

Vibration damping device for railroad vehicle

Abstract: PROBLEM TO BE SOLVED: To provide a vibration damping device for a railroad vehicle capable of reducing the cost of the railroad vehicle, and optimizing vibration suppression control SOLUTION: The vibration damping device for the railroad vehicle comprises a damping force variable damper 3 which is interposed between a vehicle body 1 in a railroad vehicle V and a truck 2 for supporting the vehicle body 1 to suppress the vibration of the vehicle body 1 in the horizontal lateral direction with respect to the advancing direction of the vehicle V, a detection means 5 for detecting the vibration acceleration of the vehicle body 1 in the horizontal lateral direction with respect to the advancing direction of the vehicle V, and a control means 4 for performing the skyhook semi-active control of the control force F for suppressing the vehicle body vibration generated by the damping force variable damper 3; and further comprises an analysis means which analyzes the vibration acceleration to be detected by the detection means 5 to obtain the data for evaluating the ride quality COPYRIGHT: (C)2009,JPO&INPIT

Complementary Filter to Estimate Inertial Velocity

Abstract: Long appreciated advantageous stability and performance properties of "skyhook damping" are dependent on availability of an inertially referenced velocity signal. In this work a practical complementary filter using acceleration and position measurements is proposed to construct a high quality inertial velocity signal. The filter was used in a hydraulic suspension system, which isolates the cab of a semitractor from pitching motion of the frame. Low frequency pseudo-integration properties previously limited actual system performance on the vehicle. When the proposed complimentary filter was implemented, a nearly 10 dB improvement in resonant frequency attenuation was achieved while maintaining consistent stability margins.

Nonlinear mr model inversion for semi-active control enhancement with open-loop force compensation

Abstract: The increased prevalence of semi-active control systems is largely due to the emergence of cost effective commercially available controllable damper technology such as Magneto-Rheological (MR) devices. Unfortunately, MR dampers are highly nonlinear, which presents an often over-looked complexity to the control system designer. The well-known Skyhook Damping control algorithm has enjoyed great success for both fully active and semi-active control problems. The Skyhook design strategy is to create a control force that emulates what a passive linear damper would create when connected to an inertial reference frame. Skyhook control is device independent since it generates a desired control force command output that must be produced by the control system. For simplicity, MR dampers are often assumed to have a linear relationship between the current input and the force output at a given relative velocity. Often this assumption is made implicitly and without knowledge of the underlying nonlinearity. In this paper, we show that the overall performance of a semi-active Skyhook control system can be improved by explicitly inverting the nonlinear relationship between input current and output force. The proposed modification will work with any semi-active control algorithm, such as Skyhook, to insure that the controller performance is at least as good as the performance without the proposed modification. This technique is demonstrated through simulation on a quarter-vehicle system.

Genetic Algorithm Aided Groundhook Control Strategy for Semi-Active Magneto Rheological Damper Suspension System

Abstract: In this paper, a novel strategy called Genetic Algorithm aided Groundhook Control (GAGC) is proposed for vibration suppression of a 5 Degree Of Freedom (DOF) model of semi-active vehicle suspension system. This model considers bounce and pitch motions and utilizes magneto rheological damper (MRD). The model represents a pitch-plane vehicle suspension system with two independent spring-M RD sets in front section, two spring-MRD sets in rear section and a spring-MRD set as the driver's seat suspension system. The last spring-MRD set is controlled using groundhook control strategy. In this research we used Bingham plastic model to characterize the behavior of this MRD. The parameters of the proposed MRD are determined using Genetic Algorithm (GA). Simulation results prove that the proposed strategy yields a comfortable ride as well as effective vibration suppression. Two types of control strategies can be used in a semi-active suspension system: Skyhook control and groundhook control. The latter one which is considered in this study, works as follows: W hen the relative velocity between driver's seat and sprung mass is in the same direction with the velocity of the sprung mass, an electric current is applied to the MRD, otherwise no damping force is required. Since a MRD is unable to provide a zero force, we should minimize the semi-active damping force without any electric current. This condition implies that the actuating of the controller only assures the increment of energy dissipation of the stable system. The review of simple but credible models reveals that the vibration response of vehicles to different excitations can be investigated through the analysis of various in-plane models (Ahmed, A.K., 2002). In literatures, half-car model (Rao, L.V.V.G. and S. Narayanan, 2008) as well as the pitch-plane suspension model (Martynowicz, P. and B. Sapin, 2005; Sapin, B. and M. Roso, 2005) are considered for the purpose of studying bounce and pitch motions. Spinski and Rosol (Sapinski, B.and M. Rosol, 2008) concerned an autonomous control system (ACS) for a 3 DOF pitch-plane suspension model. They assumed negligible contributions due to the wheel-axle-brake assemblies' masses and tires stiffness. That means the road input is taken to be the same as the wheels input.

Vibration Control of Vehicle Suspension Featuring Magnetorheological Dampers : Road Test Evaluation

Abstract: This paper presents vehicle road test of a semi-active suspension system equipped with continuously controllable magnetorheological(MR) dampers. As a first step, front and rear MR dampers are designed and manufactured based on the optimized damping force levels and mechanical dimensions required for a commercial middle-sized passenger vehicle. After experimentally evaluating dynamic characteristics of the MR dampers, the test vehicle is prepared for road test by integrating current suppliers, real-time data acquisition system and numerous sensors such as accelerometer and gyroscope. Subsequently, the manufactured four MR dampers(two for front parts and two for rear parts) are incorporated with the test vehicle and a skyhook control algorithm is formulated and realized in the data acquisition system. In order to emphasize practical aspect of the proposed MR suspension system, road tests are undertaken on proving grounds: bump and paved roads. The control responses are evaluated in both time and frequency domains by activating the MR dampers.