Sam-Sang You

MULTI-OBJECTIVE CONTROL SYNTHESIS : AN APPLICATION TO 4WS PASSENGER VEHICLES

Abstract The vehicle dynamics and control play an important role in an automated highway system for passenger cars. This study addresses the problem of designing active controllers for four-wheel-steering (4WS) vehicles. We first obtain a set of linear maneuvering equations representing the four-wheel steering motions and independent wheel torques for lateral/directional plus roll dynamics. We then formulate simultaneous H 2 and H ∞ (sub)-optimal controls with a desired pole assignment via linear matrix inequalities (LMIs). The steering angles are actively controlled by steering wheel commands through the actuator mechanisms for the lateral/directional and roll motions. Further the wheel power and braking are directly controlled by independent torques. Numerical simulations are performed on a complex vehicle model in order to evaluate the vehicle performance (noise and disturbance attenuation), stability, and robustness under a given class of uncertainty. Finally, the presented autopilot controller provides greater maneuverability and improved directional stability for passenger vehicles.

CONTROLLER DESIGN AND ANALYSIS FOR AUTOMATIC STEERING OF PASSENGER CARS

Abstract This paper deals with a lateral controller design for active 2WS vehicles in ITS applications. First, the vehicle dynamics for typical lateral maneuvers are rigorously described by Newtons formulation. Next, based on a linear perturbed model, a robust controller via μ (mu)-synthesis is designed. Due to the characteristics of D–K iteration, the resulting high-order controller has to be reduced for implementation. Then the frequency- and time-domain responses of the robust controller are extensively evaluated through numerical simulations. Further, we present performance comparisons between full-order controller and reduced-order controller. Finally, the automated steering control presented here is shown to be robust to the prescribed levels of uncertainty for highway maneuvers.

Experimental Investigation of Heat Transfer in Two-phase Flow Boiling

In this article, an experimental investigation is performed to measure the boiling heat transfer coefficient of water flow in a microchannel with a hydraulic diameter of 500 μm. Experimental tests are conducted with heat fluxes ranging from 100 to 400 kW/m2, vapor quality from 0 to 0.2, and mass fluxes of 200, 400, and 600 kg/m2s. Also, this study has modified the liquid Froude number to present a flow pattern transition toward an annular flow. Experimental results show that the flow boiling heat transfer coefficient is not dependent on mass flux and vapor quality but on heat flux to a certain degree. The measured heat transfer coefficient is compared with a few available correlations proposed for macroscales, and it is found that previous correlations have overestimated the flow boiling heat transfer coefficient for the test conditions considered in this work. This article proposes a new correlation model regarding the boiling heat transfer coefficient in mini- and microchannels using boiling number, Reynolds number, and modified Froude number.

Active steering for intelligent vehicles using advanced control synthesis

This paper considers the design of an active steering controller of an intelligent vehicle for general lane change manoeuvres. First, we present a unified formulation of lateral vehicle dynamics. Next, the design method includes the 2-DOF H∞ loop-shaping control scheme for lane change manoeuvres, in the face of co-prime factorisation perturbations. Furthermore, the controller has been reduced to a reasonable order before real implementation. The resulting controller is then evaluated in both frequency- and time-domains. Finally, it is shown that the presented controller provides excellent performance over a wide range of simulated manoeuvring conditions.

Automatic steering controllers for general lane-following manoeuvres of passenger cars using 2-DOF robust control synthesis

This paper deals with the modelling and robust control synthesis of intelligent vehicles for general lateral motion in intelligent transportation system applications. The lateral vehicle dynamics for general lane following are firstly derived in a unified framework. Based on a coprime factor plant description, the two-degree-of freedom based H1 loop-shaping control scheme is presented for lane keeping and changing manoeuvres simultaneously. The resulting robust controller is generally of high order and has to be reduced for real implementation. Also, the reduced-order controller is evaluated in both the frequency- and the time-domain analysis. Finally, it is found that the proposed automatic steering controller provides robust performance and stability for a given vehicle manoeuvring in the presence of parameter variations of vehicles.

Experimental and Numerical Analysis for Single-phase Flow Pressure Drop in Parallel Micro-channels

The experimental and numerical studies of the single-phase flow pressure drop in parallel micro-channels were performed. The parallel micro-channels consisted of 15 channels with depth 0.2mm, width 0.45mm and length 60mm. The FC-72 was used as the working fluid and the mass fluxes ranged from 62.8 to 1371.6kg/m 2 s. The numerical analysis was performed iterative calculations to solve governing equations and finds the appropriate value. The experimental data was compared with the numerical data, the results showed good agreement with the numerical data.

Two-phase Pressure Drop in Horizontal Rectangular Channel

Two-phase pressure drop experiments were performed during flow boiling to deionized water in a microchannel having a hydraulic diameter of . Tests were made in the ranges of heat fluxes from 100 to , vapor qualities from 0 to 0.2 and mass fluxes of 200, 400 and . The frictional pressure drop during flow boiling is predicted by using two models; the homogeneous model that assumes equal phase velocity and the separate flow model that allows a slip velocity between two phases. From the experimental results, it is found that the two phase multiplier decreases with an increase in mass flux. Measured data of pressure drop are compared to a few available correlations proposed for macroscale and mini/microscale. Among the separated flow models, the correlation model suggested by Lee and Garimella predicted the frictional pressure drop within MAE of 47.2%, which is better than other correlations.

Two-phase pressure drop due to friction in micro-channel

This paper deals with an experimental investigation to measure the frictional pressure drops for two-phase flow boiling in a micro-channel with a hydraulic diameter of 500 µm. First, the experimental study is performed under the test conditions: heat fluxes ranging from 100 to 400 kW/m2, vapor qualities from 0 to 0.2, and mass fluxes of 200, 400 and 600 kg/m2s. Then, the frictional pressure drop during flow boiling is estimated using two models: the homogeneous model and the separated flow model. The experimental results show that the two-phase multiplier decreases with the increase of mass flux. In addition, the measured pressure drops are compared with those from a few correlation models available for macro-scales and mini/micro-scales. Finally, the present paper proposes a new correlation for two-phase frictional pressure drops in mini/micro-scales. This correlation model is developed based on the Chisholm constant C as a function of two-phase Reynolds and Weber numbers. It is found that the new correlation satisfactorily predicts the experimental data within mean absolute error (MAE) of 3.9%.

Dynamics and robust control of underwater vehicles for depth trajectory following

This paper addresses the robust control synthesis of diving/climbing manoeuvres for underwater vehicle in the vertical plane. First, a new state–space representation for the vehicle dynamics is presented, and the corresponding problem formulation is clearly stated. Next, the two-controller set-up using a H∞-loop shaping design is employed to deal with the bottom following capability and robustness issues. Then the reduced order control system with a Hankel norm is evaluated in the frequency domain. In addition, the preview control approach is used to improve the overall tracking performance for undersea manoeuvres. The specific control tasks include the tracking of a set of depth profiles or ocean floors. Simulation results show that control objectives are effectively accomplished in spite of model uncertainties. Finally, it is found that the proposed control methodology is suitable for the depth trajectory following applications over a wide range of operating conditions.

Development of a new buffing robot manipulator for shoes

This paper presents analysis and experimental verifications of a new robot manipulator with five degrees of freedom developed for the buffing operation of shoes. First, the forward and inverse kinematics are analyzed. Next, an analytic closed-form solution is rigorously derived for the joint angles corresponding to the position and orientation of the end-effector in Cartesian coordinates. A control system, including input/output interfaces and the related electronic system, is designed for the control of the mechanical structure of the buffing robot. Then, peripheral systems integrated with the conveyer, transfer device, and fixture device are designed for the sequential buffing process of shoes. Also, a graphic user interface (GUI) program including the forward/inverse kinematics, control algorithm, and communication program to interact the robot with the peripheral systems is developed by using visual C++ language. A new flexible toolholder (FTH) is proposed to compensate for the excessive applied force between deburring tools and shoes. Finally, the test results are provided to demonstrate the effectiveness of the proposed scheme.