Wen-Ching Chung

Control Design for Vehicle's Lateral Dynamics

Issues of controllability and stabilization design for vehicles lateral dynamics are presented. Based on the assumption of constant driving speed, a second-order nonlinear lateral dynamical model is obtained. It is observed that saddle node bifurcation will appear in vehicle dynamics with respect to the variation of the front wheel steering angle, which might result in spin and/or system instability. In order to possibly prevent the occurrence of such an instability, the controllability of vehicle dynamics at the saddle node bifurcation point is discussed. This leads to the design of a direct state feedback control law for system stabilization. Two-Parameter bifurcation analysis of system behavior is also obtained to classify the regime of the effective control gains for system stabilization. Numerical simulations for an example model demonstrate the effectiveness of analytical results.

Two-parameter bifurcation analysis of longitudinal flight dynamics

The bifurcation analysis of longitudinal flight dynamics is presented, emphasizing the influence of elevator deflection and aircraft mass. Based on a mathematical model proposed by Garrard and Jordan (1977), a rich variety of bifurcation phenomena such as saddle-node bifurcation, Hopf bifurcation, and cycle fold bifurcations are observed in the numerical simulations of longitudinal flight dynamics of the F-8 aircraft. The occurrence of saddle-node bifurcation and Hopf bifurcation may result in jump behavior and pitch oscillations of flight dynamics. The analysis leads to a division of the longitudinal flight space into several maneuvering regions, and may provide more understanding of the longitudinal flight dynamics.

Control Design for Longitudinal Flight Dynamics

In this paper, the control issues of longitudinal flight dynamics is presented. System controllability with respect to the variation of the elevator deflection angle is first discussed. Stabilization controllers using washout filter-aided feedback control law is then proposed. Case study for F-8 aircraft is explicitly derived for constructing a feasible set of controllers. Numerical simulations for bifurcation scenarios are also given to compare the performance of the designs

LINEAR STATE FEEDBACK DESIGN FOR SURGE CONTROL OF AXIAL FLOW COMPRESSOR DYNAMICS

Based on Moore and Greitzers model [15], the surge behavior of axial flow compression system was found to be attributed to the appearance of Andronov-Hopf bifurcationin [12]. In this paper, we focus on the design of control law to prevent and/or delay the occurrence of the bifurcations, which will then suppress the surge behavior. Both types of linear dynamic state feedback and linear washout filter controllers are proposed. The proposed washout design does not require the explicit knowledge of the operating point and keep the original equilibrium characteristic while the dynamic feedback design will change the equilibrium operating points for pre-surge and post-surge regime. In addition, the washout type control scheme can relax the implementation of the control law in the practical applications. Numerical results demonstrate the effectiveness of the proposed designs and the superiority of the washout filter scheme.

A Feedback Linearization Design for the Control of Vehicle's Lateral Dynamics

In this paper, the feedback linearization scheme is applied to the control of vehicles lateral dynamics. Based on the assumption of constant driving speed, a second-order nonlinear lateral dynamical model is adopted for controller design. It was observed in Liaw and Chung (2006) that the saddle-node bifurcation would appear in vehicle dynamics with respect to the variation of the front wheel steering angle, which might result in spin and/or system instability. Feedback linearization control laws are proposed in this paper to stabilize the vehicles dynamics at bifurcation points. Numerical simulations for an example model demonstrate the effectiveness of the analytical results

Washout-filter based bifurcation control of longitudinal flight dynamics

This paper presents the bifurcation control of longitudinal flight dynamic, via washout filter based design. Based on the mathematical model proposed by Garrard and Jordial (1977). a rich variety of bifurcation phenomena, such as saddle-node bifurcation, Hopf bifurcation, and cycle fold bifurcations are observed in the numerical simulations of longitudinal flight dynamics of F-8 aircraft. The occurrence of saddle-node bifurcation and Hopf bifurcation might result in jump behavior and pitch oscillations of flight dynamics. Bifurcation control laws are proposed to change the property of bifurcation phenomena and hence improve system stability.

The steering control of vehicle dynamics via a sliding mode method

In this paper, we propose a steering control scheme for vehicle dynamics by using sliding mode control approach. The vehicle dynamics is known to exhibit a saddle-node bifurcation phenomenon while operating at some front wheel steering angle, which might incur spin and/or instability for vehicle systems and then cause traffic accidents. By using the proposed sliding mode control law, the vehicle dynamics will be stabilized at the bifurcation point and the stability of the vehicle system will also be guaranteed after the appearance of bifurcation phenomenon. Simulation results for an example vehicle model demonstrate the success of the proposed design.

The steering control of vehicle dynamics via a Lyapunov redesign approach

In this paper, Lyapunov redesign method is proposed to control the steering of vehicle. It was observed in Liaw and Chung (2006) that the vehicle dynamics would exhibit the saddle-node bifurcation phenomenon at some front wheel steering angle. This might result in spin and/or instability for vehicle system. Based on the assumption of constant driving velocity, a Lyapunov redesign control law was proposed to stabilize the system dynamics at the bifurcation point for guaranteeing system stability after the appearance of stall. Simulation results for an example model of vehicle dynamics were presented to illustrate the success of the proposed design.

Nonlinear control of longitudinal flight dynamics

This paper presents the nonlinear analysis and control of a third-order model for longitudinal flight dynamics. Bifurcation analysis using numerical study for F-8 aircraft reveals that Hopf bifurcations may occur at some critical values of the elevator commands. These results agree with the well-known nonlinear phenomena existed in longitudinal flight dynamics. Furthermore, bifurcation control using both washout filter and direct state feedback are applied to develop the stabilizing laws for system equilibria and periodic solutions emerged from bifurcation points. Numerical simulations are providedto demonstrate these main results.