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To enhance passenger ride comfort, improve vehicle safety and stability, and possibly reduce potential accidents due to driver mis-operations, automatic steering control has been a fascinating research topic in the area of Advanced Vehicle Control Systems (AVCS). More recently, due to deteriorated traffic congestion on highways, steering control of automated vehicles has been studied extensively in the context of Automated Highway Systems (AHS) among researchers throughout the world in the past several years.
A popular automatic steering control approach for passenger cars is to de-couple the yaw motion from lateral motion by using yaw rate feedback. It has recently been shown that by re-defining the control position at a frequency-dependent distance ahead of the vehicle, the yaw dynamics can also be de-coupled. The resulting system dynamics with this dynamic look-ahead scheme can be simplified into a double-integrator type vehicle dynamics with a constant open-loop gain. It has further been shown that the open loop gain of the resulting double-integrator vehicle dynamics is independent of the vehicle longitudinal velocity. This invariant property makes the design of a full-operating-envelope controller much easier. Even though the simplified input-output dynamics obtained from the dynamic look-ahead scheme appears similar to that from the de-coupling approach using yaw rate feedback, the hidden (unobservable) dynamics of the closed control loop using the dynamic look-ahead scheme possesses much better damping properties than that using yaw rate feedback.
In this study, experimental data of open-loop vehicle dynamics at different vehicle speeds will be used to validate the effectiveness of this dynamic look-ahead scheme. Experimental data utilized in this study include both vehicle yaw rate frequency response and lateral acceleration frequency response, which have been
conducted before by applying frequency-sweeping techniques at different vehicle longitudinal velocities. Important vehicle parameters, such as mass, moment of inertia, and tire cornering stiffness, will firstly be estimated/identified in this project by analyzing these experimental data. Secondly, a computer simulation vehicle model, which has been derived by applying Newton’s law of motion, will be calibrated by
incorporating identified vehicle parameters and possible un-modeled dynamics extracted from the experimental data. This calibrated computer simulation model will be utilized to simulate the vehicle’s closed-loop response under automatic steering control using the proposed dynamic look-ahead scheme. Thirdly, notice that the main appeal of this dynamic look-ahead scheme is that it can de-couple vehicle’s yaw dynamics from vehicle’s lateral dynamics and simplify the input-output dynamics into a double-integrator. This claim will be validated by applying the dynamic look–ahead scheme off-line to the experimental data and examine if the input-output frequency response exhibits double-integrator characteristics.
Keyword
Vehicle Control, Automatic Steering, Lateral Control, Yaw De-coupling, Zero Dynamics, Output Re-definition!"# $%&'()* +,-. /0$ 123456789:;<=> ?@ABCD !EFGHIJK LB89M: NOP 45 ?@#Q2RSTUVWXY/0$15 Z[\"]^_/0`abcdeC$% &6% '´GVw /0`abcd»¼ 1 ()à¯*+,- 1.G/301d.
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4. Guldner, J., H. Tan, and S. Patwardhan, “Analysis of Automatic Steering Control for Highway Vehicles with Look-down Lateral Reference Systems”, Vehicle System Dynamics, vol. 26, pp. 243-269, 1996.
