Unsprung Mass Velocity Research Articles

Control of active suspension system in the presence of nonlinear spring and damper

Two methods which are computationally simple and easy to apply are developed by using state dependent Riccati equation (SDRE) approach and approximating sequence of Riccati equation (ASRE) approach to control active suspension system in the presence of nonlinear spring and damper. Additionally, effectivenesses of the both control methods developed by utilizing two recently introduced SDRE and ASRE techniques are compared. First, methodologies of both approaches are presented. After that, nonlinear dynamics of the vehicle suspension system is described in terms of conveniently selected state variables for better control performance. Then, a cost function is written by using suspension and tire deflections, sprung mass velocity and acceleration, and unsprung mass velocity variables to improve ride quality, suspension deflection, and tire deflection. Additionally, a convenient representation of this cost function in terms of state variables is obtained to realize better control. A bump expressed as sinusoidal function and roughness of the road expressed as white noise are taken into consideration as the disturbances from the road. Finally, quarter vehicle suspension system equivalent model of Ford Fiesta Mk2 is used as an example and simulations obtained by using the developed control methods are checked against the performance requirements and corresponding passive suspension system.

Simultaneous Output Selection and Observer Design for Vehicle Suspension System With Unknown Road Profile

In this paper, a reduced-order observer is designed using an unknown input decoupling approach to estimate the road profile and the state variables of vehicle suspension system. During the observer design process, a new concept called the degree of observability (DO) is introduced to quantitatively describe the strengths and weaknesses of the system observability in terms of different outputs. This concept integrated with the decoupling conditions lead to a systematic method for selecting the suitable outputs of the suspension system for the observer design. In this method, among all output combinations that satisfy the decoupling requirements, the combination of sprung mass displacement and unsprung mass velocity is found to have the highest DO containing the most information of the system. The performance of the designed observer with the selected outputs is compared with the Kalman filter (KF) developed in the literature by assuming the initial random walk model for the road profile. To have a nearly real situation for simulation studies, a MacPherson suspension model constructed in the ADAMS multibody software is employed. The results obtained by deterministic and stochastic road excitations indicate much more accurate estimations for the designed observer with minimum outputs compared with the KF. The estimation errors are quantitatively compared with the KF using different set of outputs to confirm the positive effect of simultaneous DO analysis and decoupling approach. Meanwhile, the proposed observer is free of assumptions, and its structure is more simple and easier for implementation.

Output feedback [formula omitted] control for active suspension of in-wheel motor driven electric vehicle with control faults and input delay

In this paper, an output feedback H∞ controller is proposed for active suspension of an electric vehicle driven by in-wheel motors with actuator faults and time delay. The dynamic damping in-wheel motor driven system, in which the in-wheel motor is designed as a dynamic vibration absorber (DVA), is developed to improve ride quality and isolate the force transmitted to motor bearings. Furthermore, parameters of vehicle suspension and DVA are optimized based on the particle swarm optimization (PSO) to achieve better suspension performance. As some of the states such as the DVA velocity and unsprung mass velocity are difficult to measure, a robust H∞ output feedback controller is developed to deal with the problem of active suspension control with actuator faults and time delay. The proposed controller could guarantee the system’s asymptotic stability and H∞ performance, simultaneously satisfying the performance constraints such as road holding, suspension stroke, and actuator limitation. Finally, the effectiveness of the proposed output feedback controllers is demonstrated based on the quarter vehicle suspension model under bump and random road excitations.

Motorized vehicle active suspension damper control with dynamic friction and actuator delay compensation for a better ride quality

This paper describes motorized active suspension damper control with dynamic friction and actuator delay compensation for an enhanced ride quality. The control algorithm consists of a supervisory controller, an upper-level controller and a lower-level controller. The supervisory controller determines the control modes, such as the passive control modes and the active control mode. The upper-level controller, which incorporates the existing actuator delay, computes the damping force using linear quadratic control theory. The actuator input is determined by the lower-level controller by compensating the dynamic friction torque. To estimate the sprung-mass displacement, the sprung-mass velocity, the unsprung-mass displacement and the unsprung-mass velocity, two state estimators are proposed. An adaptive observer is developed for the non-linear dry friction to estimate the ball-screw dynamic friction caused by the axial movement of the actuator and the viscosity. The performance of the proposed control algorithm was evaluated from simulations. It was shown from simulations that the proposed motorized active suspension damper control with a friction and delay compensation algorithm can improve the ride quality.

Control of the motorized active suspension damper for good ride quality

This paper presents a control algorithm for the motorized active suspension damper. The control algorithm consists of supervisory, upper-level and lower-level controllers. The supervisory controller determines the control modes, such as the passive mode, the roll mode and the body acceleration mode. The upper-level controller computes the damping force using linear quadratic control theory. The actuator input is determined by the lower-level controller. Three state estimators, namely the vehicle body’s velocity estimator, the suspension state estimator and the friction estimator, are proposed to estimate the sprung-mass and unsprung-mass velocities, the tyre deflection, the roll angle, the roll rate and the friction. The performance of the proposed control algorithm was evaluated via simulations and vehicle tests. It was shown from both simulations and vehicle tests that the proposed control algorithm can improve the ride quality using a motorized active suspension damper.

Electro-mechanical suspension system considering energy consumption and vehicle manoeuvre

In this paper, the performance of the electro-mechanical suspension is discussed on the energy consumption, vibration isolation, and vehicle manoeuvrability. On the basis of the formulation of electro-mechanical suspension, the energy consumption and vibration isolation are discussed through the contour maps with the sprung and unsprung mass velocity feedback gain axes. From the numerical simulation and experimental results, the contour maps for the evaluation of the performance with feedback gain axes are proposed, and on these maps, the abilities of vibration isolation and manoeuvrability are evaluated. On the energy consumption, the regeneration region exists, and the velocity feedback gain of unsprung mass should be considered for regeneration and energy saving. Moreover, Gain settings for improving each vehicle performance are proposed and verified by shaker tests. From simulation and experimental results, it is demonstrated that the proposed active suspension system is able to solve the compatibility between vibration isolation and energy saving.

A road-adaptive control law for semi-active suspensions

This paper presents a road-adaptive control law for semi-active vehicle suspensions. In semi-active suspensions, damping coefficients are controlled so as to make the actual damper force as close to the desired damper force as possible at any time instance. The proposed control law consists of a road-adaptive sky-hook damping algorithm and a Road Detection Algorithm (RDA). This approach leads to the sprung mass and unsprung mass velocity feedback control law with time varying gains. The gains are tuned by the RDA. To evaluate the performance enhancement brought about by the proposed control law, the performance of a semi-active suspension with the proposed control law is compared to those of the sky-hook controlled semi-active suspension and a passive suspension. The controller has been implemented experimentally on a quarter car test rig and a semi-active damper with a 19 damping rates has been used to generate the desired semi-active force. The proposed control law provides adequate damping for the wheel hop frequency and improved performance compared to that of the sky-hook control law.

Observer Design for Semi-Active Suspension Control

This paper presents an observer for automotive semi-active suspension control. Automotive suspensions are disturbance affected dynamic systems and semi-active suspensions can be represented as a bilinear model. An observer for semi-active suspensions is formulated such that the estimation error is independent of unknown external disturbance. The proposed observer uses easily accessible measurements such as accelerations and guarantees exponentially convergent state estimation for suspension deflections and velocities. Absolute sprung mass and unsprung mass velocities can be estimated using the proposed observer. Simulations and experimental rig tests show that all states of a semi-active suspension can be estimated only with acceleration measurements. The estimated states are used to improve ride quality in a semi-active suspension.

Observer-based control of vehicle semi-active suspensions

This paper presents an observer-based controller for vehicle semi-active suspensions. Vehicle suspensions are disturbance-affected dynamic systems and semi-active suspensions can be represented as a bilinear model. A new methodology for designing observers for vehicle semi-active suspensions has been proposed. The proposed methodology simplifies the observer design process and is convenient for implementation. An observer is formulated such that the estimation error is independent of unknown road disturbances. The proposed observer uses easily accessible measurements, such as accelerations, and guarantees exponentially convergent state estimations for suspension deflections and velocities. The absolute sprung mass and unsprung mass velocities can be estimated using the proposed observer. Simulations and experimental rig tests show that all states of a semi-active suspension can be estimated only with acceleration measurements. The estimated states are used to improve ride quality in a semi-active suspension. It has been shown that the performance of the observer-based controller is comparable to that of a controller using measured states.

A new adaptive sky-hook control of vehicle semi-active suspensions

This paper proposes a new adaptive sky-hook control law for vehicle semi-active suspensions. Vehicle suspensions are disturbance-affected dynamic systems. In semi-active suspensions, damping coefficients are controlled so as to make the actual damper force as close to the desired damper force as possible at any time instance. The proposed control law consists of a ‘new adaptive’ sky-hook damping algorithm and a road detection algorithm (RDA). This approach leads to the sprung mass and unsprung mass velocity feedback control law with time varying gains. The gains are tuned by the RDA. To evaluate the performance enhancement brought about by the proposed control law, the performance of a semi-active suspension with the proposed control law is compared with that of the sky-hook controlled semi-active suspension and with a passive suspension. The controllers are implemented experimentally on a quarter-car test rig and a semi-active damper with 19 damping rates has been used to generate the desired semi-active force. The performance of the proposed control law is shown to be superior to that of the sky-hook control.

Reduced Order Design of Active Suspension Control

The presence of fast and slow modes in suspension systems is utilized in the design of two reduced-order active suspension control strategies. The first strategy is obtained by combining the solutions of slow and fast control sub-problems. The second strategy is based on a two-level hierarchical control design. The local level requires measurements of local fast variables, namely the unsprung mass velocities. The coordinating level relies on measurements of slow variables, namely, suspension deflections, sprung mass velocity, and mass pitch rate. Neither strategy requires tire deflection measurements. In spite of their simplified structure, simulation results indicate that their performance is comparable to that of the full-state feedback design.