Jihua Huang

Design and field testing of a Cooperative Adaptive Cruise Control system

This paper describes the development of an Cooperative Adaptive Cruise Control (CACC) experimental system with vehicle-to-vehicle communication based on a car with factory installed ACC system. The controller design will be introduced in detail on how to incorporate the information shared through wireless communication link. The structure of the proposed CACC controller and an indirect adaptive Model Predictive Control (MPC) based gap regulation controller are presented. Experimental results from field testing at both vehicle proving ground and public highway are shown to verify the effectiveness of the proposed controller design.

LTV controller design for vehicle lateral control under fault in rear sensors

This work focuses on vehicle lateral control for automated highway systems (AHSs) studied as a part of the California Partners for Advanced Transit and Highways (PATH) Program. In the PATH lateral control system, magnetometers are installed under both front and rear bumpers of the vehicle; these magnetometers measure the lateral deviation of the vehicle relative to the magnets buried along the centerline of each automated lane. Lateral controllers have been designed and tested successfully provided that there is no fault in magnetometers. It has been argued that these controllers are NOT tolerant to the fault in magnetometers. The focus of This work is the degraded-mode lateral control under fault in rear magnetometers. The aim of the controller design is to accomplish adequate performance with the remaining set of magnetometers, the front magnetometers. The effects of the fault are examined, and the significance of the linear time-varying (LTV) property of the front-magnetometer-based vehicle lateral dynamics is recognized. Popular control methods for LTV systems generally involve gain scheduling by switching between several linear time-invariant (LTI) controllers. Such methods are complicated and it is difficult to prove the stability of the switching mechanism. To derive a simple effective LTV controller, feedback linearization is applied to approximately cancel out the time-varying terms in the plant and to function as a gain scheduler. However, due to the weakly damped zeroes of the plant, feedback linearization with state feedback or matched observer state feedback results in weakly damped internal dynamics. In order to tune the internal dynamics, a mismatched observer is designed based on H-infinity optimal control techniques. Experimental results are presented to show the effectiveness of the controller design.

The design and implementation of an automated bus in revenue service on a bus rapid transit line

This paper describes the development of an automated steering control system that has been implemented and deployed on a 60-ft articulated bus in Eugene, Oregon for revenue service. With operators controlling the speed, the automated steering system needs to conduct S-curve precision docking and lane keeping maneuvers in a challenging real-world environment consisting of a three-mile-long narrow urban segment with sharp curves, six stations, and dedicated and mixed traffic lanes. Because the automated steering bus was intended to carry passengers for an extended period of time, in addition to the normal performance and robustness considerations, the system design needed to incorporate the redundancy, fault detection, and fault management into the controller structure. This paper introduces the safety-centered system architecture and discusses the methodologies adopted to meet the elevated safety and performance requirements. With the experience of not only designing but also deploying this safety-critical vehicle control system, this paper may provide new insights into addressing safety as an integral element of the automated vehicle system design. The resulting system also offers an example of using duplex redundancy in automated vehicle control systems.

Preliminary steps in understanding a target & control based driver steering model

This paper presents the preliminary steps in understanding a target & control based (T&C) driver steering model. This driver steering model was developed and verified based on vehicle test data of Double Lane Change (DLC) maneuvers. According to the data, drivers use target points located at the centerline of the lane to be changed to as references for control and determine steering rate based on a target angle error with respect to the current target point. The T&C driver model was shown to effectively capture drivers steering behavior. This paper examines the extendibility of this T&C driver steering model to other common maneuvers, such as left/right turns in intersections; the initial simulations show that this T&C model is capable of performing other maneuvers with ease, indicating its potential to be a generic driver model. Moreover, the preliminary control synthesis shows that this model exhibits plenty of stability margins for drivers to increase their control gain when necessary.

Driver steering model based on a target & control scheme

This paper aims to develop a driver steering model that can capture drivers key steering mechanisms from a control engineering point of view. Analyses with Double Lane Change (DLC) vehicle test data suggest that, instead of following the traditional concept of trajectory planning, drivers use target points located along the centerline of the lane they are changing to as references for control. The data also suggests that drivers engage steering rate control instead of steering angle control to steer the vehicle. Based on these analyses, this paper proposes a relatively straight-forward driver steering model based on this target & control scheme. Vehicle data of more than 80 DLC runs is used for the model verification. Both the open-loop identification and closed-loop simulations verify that this relatively simple driver steering model is capable of capturing drivers steering behavior and the simulated steering rate matches well with the actual steering rate.

Lateral control of an articulated bus for lane guidance and curbside precision docking

This paper presents the design, implementation, and field testing of a lane assist system that provides lane guidance and curbside precision docking functions for a 60 ft articulated bus. The challenges in this lateral control design include the extra lightly-damped mode from the articulated section, the relatively large disturbance due to the sharp S-curves for precision docking, and the uncertainties introduced by public roads and live traffic. To tackle these challenges, the control problem is formulated as a mixed H2/H∞ synthesis problem and solved by LMI optimization. Extensive field tests were conducted in live traffic and the results show adequate and consistent performances.

H/sub /spl infin// controller for vehicle lateral control under fault in front or rear sensors

This paper presents the design of lateral controllers for automated vehicles under specific sensor fault. The specific fault refers to the failure of one of the two sets of sensors on-board the vehicle which are critical to vehicle lateral control. The aim of the controller design is to accomplish sound performance with the remaining set of sensors. The current vehicle lateral controller, which works with the two sets of sensors, is examined and its ineffectiveness under sensor failures is described. Controllers with one set of sensors are designed using the H/sub /spl infin// optimal control theory. Two controllers are derived, each using one set of the two sets of sensors. Simulation results are presented to demonstrate the effectiveness of the controllers.

Design of an automatic steering controller for bus revenue service based on drivers' steering mechanism

This paper describes an automatic steering controller based on a target and control driver steering model. Derived based on analyses of vehicle test data on the standard Double Lane Change (DLC) course, this novel target and control driver model captures drivers key steering mechanisms. The analyses show that, instead of planning and following a desired path according to the traditional trajectory planning concept, drivers use the next lane center as the target points to generate vehicle angle error for control during lane changes. The data also suggests that drivers apply steering rate control instead of the conventional steering angle control to steer the vehicle. By extending this relatively straight-forward look-ahead based driver steering model to an automatic steering controller with a “look-down” sensing system, an equivalent controller structure was derived. The structure revealed that drivers apply a PID-type controller whose look-ahead distances and feedback gains are dependent on the vehicle speed. This equivalent controller was directly implemented on a 60-ft articulated bus for revenue service on a narrow and curving bus rapid transit line at Eugene, Oregon, USA. The field tests demonstrated that the controller achieved all the stringent performance and robustness requirements. This automated steering bus started its daily revenue service (i.e., carrying passengers) started in June, 2013.

CHARACTERIZING DRIVING SKILL BASED ON ENTROPY ANALYSIS OF STEERING FREQUENCY RESPONSE

As a first step towards a dynamic control-oriented driver model that can describe various levels of driving skill in the driver’s primary vehicle control functions, this paper attempts to recognize the driving skill manifested in the low-level control characteristics. Vehicle tests on a DLC course were conducted with twenty subjects of different skill levels. A variance-based analysis was applied to the steering angle to generate both the frequency responses and the time sequences for frequency-domain and time-domain analysis. Two entropy measures are developed to evaluate the effectiveness of drivers’ steering control, and preview errors are used to provide an absolute measure for drivers’ preview performance. Simple rules using these three measures are developed, and data analysis verifies that the above three measures can effectively distinguish the driving skill levels of the twenty subjects participated in the DLC vehicle test.Copyright

Immediate Manual-Automatic Vehicle Control Transitions based on Dynamic Initial Conditioning

Abstract With more vehicle control systems providing partial or more complete automatic control functions in passenger vehicles, it is necessary to ensure smooth and immediate transitions between drivers manual control and automated control. This paper presents a novel switching method for achieving immediate and smooth manual-automatic vehicle control transitions. An open-loop dynamic initial conditioning module is added to the existing closed-loop automatic steering control to provide suitable references to the automatic steering controller. This open-loop dynamic initial conditioning is designed as a vehicle regulation control with gains and bandwidth lower than the automatic steering controller so as to achieve immediate, smooth transitions. Moreover, as the reference converges to zero, the overall automatic steering control system naturally becomes the original automatic steering control without any explicit transition. The proposed method was implemented in a test vehicle and test runs with over 250 switches in 300 seconds up to 140 km/h were conducted. The test results demonstrate that the proposed design has achieved immediate and smooth transitions between manual control and automated control.