Wan Suk Yoo

An adaptive LQG control for semi-active suspension systems

In this paper, a road-adaptive LQG control for the semi-active Macpherson strut suspension system of hydraulic type is investigated. A new control-oriented model, which incorporates the rotational motion of the unsprung mass, is introduced. A semi-active suspension controller adapting to road variations is proposed. First, based on the extended least squares estimation algorithm, a LQG controller adapting to the estimated road characteristics is designed. Through the computer simulations, the performance of the proposed semi-active suspension is compared with that of a non-adaptive one. The results show better control performance of the proposed system over the compared one.

Development of the PNU vehicle driving simulator and its performance evaluation

A vehicle driving simulator is a virtual reality device in which a human being is able to feel as if they are actually driving a vehicle. The driving simulator consists of a motion platform, a driving operating system, a motion controller, a visual and audio system, a vehicle dynamic analysis system, etc. In this paper, the main procedures in the development of a driving simulator are classified as follows: 1) a motion platform and a motion controller, which can track a reference trajectory, were developed; 2) a new washout algorithm to realize the motion of an actual vehicle in the driving simulator was developed, and this algorithm enables one to change the real motion space of a vehicle into the workspace of the driving simulator; and 3) a visual and audio system for a more realistic feeling were developed. Finally, an integration system to communicate and monitor among the subsystems was developed. The performance evaluation of the developed Pusan National University vehicle driving simulator (PUNVDS) was carried out.

Sliding mode controller with sliding perturbation observer based on gain optimization using genetic algorithm

The Stewart platform manipulator is a closed-kinematics chain robot manipulator that is capable of providing high structural rigidity and positional accuracy. However, this is a complex and nonlinear system, so the control performance of the system is not so good. In this paper, a new robust motion control algorithm is proposed. The algorithm uses partial state feedback for a class of nonlinear systems with modeling uncertainties and external disturbances. The major contribution is the design of a robust observer for the state and the perturbation of the Stewart platform, which is combined with a variable structure controller (VSC). The combination of controller and observer provides the robust routine called sliding mode control with sliding perturbation observer (SMCSPO). The optimal gains of SMCSPO, which is determined by nominal eigenvalues, are easily obtained by genetic algorithm. The proposed fitness function that evaluates the gain optimization is to put sliding function. The control performance of the proposed algorithm is evaluated by the simulation and experiment to apply to the Stewart platform. The results showed high accuracy and good performance.

Development of a washout algorithm for a vehicle driving simulator using new tilt coordination and return mode

A vehicle driving simulator is a virtual reality device which makes a man feel as if he drove art actual vehicle Unlike actual vehicles, the simulator has limited kinematical workspace and bounded dynamic characteristics So it is difficult to simulate dynamic motions of a multi-body vehicle model In order to overcome these problems, a washout algorithm which controls the workspace of the simulator within the kinematical limitation is needed However, a classical washout algorithm contains several problems such as generation of wrong sensation of motions by filters in tilt coordination, requirement of trial and error method in selecting the proper cutoff frequencies and difficulty in returning the simulator to its origin using only high pass filters This paper proposes a washout algorithm with new tilt coordination method which gives more accurate sensations to drivers To reduce the time in returning the simulator to its ougin, an algonthrn that applies selectively onset mode from high pass filters and return mode from error functions is proposed As a result of this study, the results of the proposed algorithm are compared with the results of classical washout algorithm through the human perception models Also, the performance of the suggested algorithm is evaluated by using human perception and sensibility of some drivers through experiments

Model reference adaptive control of a flexible structure

In this paper, the model reference adaptive control (MRAC) of a flexible structure is investigated. Any mechanically flexible structure is inherently distributed parameter in nature, so that its dynamics are described by a partial, rather than ordinary, differential equation. The MRAC problem is formulated as an initial value problem of coupled partial and ordinary differential equations in weak form. The well-posedness of the initial value problem is proved. The control law is derived by using the Lyapunov redesign method on an infinite dimensional Hilbert space. Uniform asymptotic stability of the closed loop system is established, and asymptotic tracking, i.e., convergence of the state-error to zero, is obtained. With an additional persistence of excitation condition for the reference model, parameter-error convergence to zero is also shown. Numerical simulations are provided.

Sliding mode control with fuzzy adaptive perturbation compensator for 6-DOF parallel manipulator

This paper proposes a sliding mode controller with fuzzy adaptive perturbation compensator (FAPC) to get a good control performance and reduce the chatter. The proposed algorithm can reduce the chattering because the proposed fuzzy adaptive perturbation compensator compensates the perturbation terms. The compensator computes the control input for compensating unmodeled dynamic terms and disturbance by using the observer-based fuzzy adaptive network (FAN). The weighting parameters of the compensator are updated by on-line adaptive scheme in order to minimize the estimation error and the estimation velocity error of each actuator. Therefore, the combination of sliding mode control and fuzzy adaptive network gives the robust and intelligent routine to get a good control performance. To evaluate the control performance of the proposed approach, tracking control is experimentally carried out for the hydraulic motion platform which consists of a 6-DOF parallel manipulator.

Sensitivity Analysis of Anti-resonance Frequency for Vibration Test Control of a Fixture

The test specimen in environmental vibration test is connected to the fixture through several attachment points. The forces generated by the shaker must be transmitted equally to all attachment points. The forces transmitted to attachment points, however, are different because of the flexural vibration of the fixture. The variations of the transmitted force cause the undertest, especially at anti-resonance frequencies, in vibration test control. Anti-resonance frequencies at the attachment points of the fixture must be same in order to avoid the under-test in vibration test control. The structural modification of the fixture is needed so that anti-resonance frequencies at attachment points have the same value. In this paper, the method to calculate the anti-resonance frequencies and those sensitivities is presented. This sensitivity analysis is applied to the structural modification of the fixture excited at multi-points by the shaker. The antiresonance frequencies at the attachment points of the fixture can have the same value after structural modification, and the under-test in the vibration test control can be removed. Several computer simulations show that the proposed method can remove the under-tests, which are not removed in conventional vibration test control.

Multibody dynamics in arterial system

There are many things in common between hemodynamics in arterial systems and multibody dynamics in mechanical systems Hemodynamics is concerned with the forces generated by the heart and the resulting motion of blood through the multi-branched vascular system The conventional hemodynamics model has been intended to show the general behavior of the body arterial system with the frequency domain based linear model The need for detailed models to analyze the local part like coronary arterial tree and cerebral arterial tree has been required recently Non-linear analysis techniques are well-developed in multibody dynamics In this paper, the studies of hemodynamics are summarized from the view of multibody dynamics Computational algorithms of arterial tree analysis is derived, and proved by experiments on animals The flow and pressure of each branch are calculated from the measured flow data at the ascending aorta The simulated results of the carotid artery and the ihac artery show in good accordance with the measured results

Eigenstructure assignment methodology with application to automotive active suspension control

An effective disturbance suppression controller can be obtained by assigning the left eigenstructure (eigenvalues/left eigenvectors) of a system. In order to design such a controller, both the controllability and disturbance suppressibility should be considered simultaneously. The controllability of the system may be degraded if the left eigenstructure is chosen only to suppress the disturbance, and vice versa. In this paper, a modal disturbance suppressibility measure is proposed which indicates the degree of the systems disturbance suppression performance, and a simple general left eigenstructure assignment scheme is suggested. The proposed left eigenstructure assignment scheme makes it possible to achieve the desired left eigenstructure exactly if the desired left eigenvectors reside in the achievable subspace. In case the desired left eigenvectors do not reside in the achievable subspace, the left eigenvectors are assigned to the best possible set of eigenvectors in the least square sense guaranteeing the desired eigenvalues to be achieved exactly. The proposed scheme is applied to designing an automotive active suspension control system for a half-car model and its performance is compared with the existing LQR control system design methodology.

Steering System Design of Commercial Vehicle for Improving Pulling Phenomenon During Braking

The tires, suspension type, and steering system can all cause pulling during braking. Among these, a drag link steering system and leaf-type suspension system are significant causes of vehicle pulling. In this study, the pulling problem is analyzed using the vehicle analysis program ADAMS/CAR. The drag link and leaf spring behavior is analyzed to find the key reason for pulling. After this, the optimization program Visual DOC is used with ADAMS/CAR to find a steering link connection point to reduce pulling. After conducting this simulation, K&C (kinematic & compliance) test simulation with a modified connection point is conducted to determine whether the vehicle performance improves. Through a full braking simulation, it is verified that the pulling distance is reduced at braking.