Feedforward and Feedback Control of Lane Keeping by the Human Driver

A feedforward/feedback control model of drivers’ lane keeping behavior is presented in this paper. The model is based on the linearized analysis of the driver’s curve negotiation dynamics. In real driving, the driver previews the upcoming road geometry and relies on perceived vehicle states to maintain a desired lateral position. Feedforward and feedback roles are associated with different perceptual cues, and the lane keeping task is formulated into a disturbance rejection problem. Control parameters are determined to reflect natural stable human characteristics. Verification tests in a realistic simulation environment demonstrate the ability of the model to generate driver/vehicle lane keeping responses comparable to those obtained on a simulator. Potentially, the derived control algorithm can also be applied to automatic lane-tracking as long as reliable information regarding vehicle states and upcoming road conditions is accessible.

Active Front Steering Damping Control

This paper investigates the feasibility of steering-wheel damping enhancement control of an active front steer (AFS) system without the benefit of closed-loop feedback control and actuator control parameter adjustment. Through a comprehensive modeling and analysis of the AFS system, a simple, yet effective solution is reached to incorporate an additional control term to the actuator angular displacement command, which permits the fine-tuning of the steering wheel damping characteristics as a function of vehicle operation states beyond the pre-determined specification. Furthermore, the analysis also identifies a fundamental relationship between steering effort and the damping control, and thus leads to a proposed fine tuning of the Variable-Effort Steering for further development and implementation.

Gain-Scheduled Control for an Automotive Traction PEM Fuel Cell System

To be practical in automotive traction applications, fuel cell systems must provide power output levels of performance that rival that of typical internal combustion engines. In so doing, transient behavior is one of the keys for success of fuel cell systems in vehicles. From a model-based control perspective, regulation of the fuel cell system through transients is critical, where the response of a fuel cell system depends on the air and hydrogen (flow and pressure regulation) and heat and water management. The focus of this paper is on the air/fuel supply subsystem in tracking an optimum variable pressurization and air flow for maximum system efficiency during load transients. The control-oriented model developed for this study considers electrochemistry, thermodynamics, and fluid flow principles for a 13-state, nonlinear model of a pressurized fuel cell system. For control purposes, a model reduction is performed by converting some of the model dynamics to simple algebraic relationships. A single reference input, the power demanded by the user, is utilized to produce a corresponding reference air flow and back-pressure valve opening, after passing through a static calculation and a tabulated map. Because of the complexity of the full nonlinear model (used in simulation as the truth model), where several maps are used rather than functional forms, two different control techniques are examined separately, each using a feedforward component. The first technique uses an observer-based linear optimum control which combines a feed-forward approach based on the steady state plant inverse response, coupled to a multi-variable LQR feedback control. An extension of that approach, for control in the full nonlinear range of operation, leads to the second technique, nonlinear gain-scheduled control.

Engine Start Simulation on an Engine Transient Test System: Hardware and Controls

The goal of this research is to use a hydrostatic transient dynamometer combined with new control techniques to replicate multi-cylinder engine dynamics which occur while the engine is started by an electric starting system. The transient engine dynamometer test system in the Powertrain Control Research Laboratory (PCRL) uses a torque tube and extremely stiff driveline in order to provide a very high bandwidth of torque actuation. The design and nature of this low inertia, stiff system requires that a standard electrical starting system be omitted. One of the objectives of this research was to assemble a new engine on the hydrostatic dynamometer and model the starting dynamics which occur during an engine cold start. The other objective was to verify and compare data collected by the PCRL and Ford to validate testing. This information will then be used in support of development of a cold start testing procedure on the single-cylinder engine transient test system in the PCRL.

Diagnostic Train for High Speed Line: A Tool for Improving Vehicle and Track Maintenance

During 2005, the Italian railway Network Operator (RFI – Rete Ferroviaria Italiana) realized two ETR500 train sets completely dedicated to diagnostic operation on the new high speed lines being built in Italy. During 2006, these train were equipped with a complete acceleration measuring system for test activities on new Italian high speed line Turin – Novara and Rome – Neaples. A complete accelerometric measurement set up has been installed for track investigation. To this aim, the experimental set up is able to identify vertical profile of track geometry, without the limitation to 25 – 30 m, typical of the traditional measuring methods. On the other hand, a tool for predictive identification of hunting instability has been developed. For each run, it is possible to define a map, highlighting all the irregularity wavelengths involved as a function of the space: for high speed application wavelength over 100 m can become really important both for comfort and safety, because they are able to interest low frequency dynamic (around 0.8 – 1.5 Hz). Moreover, with the aim of identifying the beginning of hunting instability, a tool has been developed in order to identify yaw instability vibration mode and thus its non-dimensional damping, just by bogie yaw acceleration measurement. Both this tools have been developed by means of comparison between numerical multi body simulations and experimental measurements. Numerical simulation have been used to simulate a wide range of operating condition, that was of fundamental importance in tuning of such tools. Full evidence on these method will be given in the paper, together with an example of the obtained results.

Model-Based Control for Diesel Engine Start-Stop Operations With a Belted Starter/Alternator

The coupling of an internal combustion engine with a starter/alternator is one of the most easily realizable hybrid electric vehicle configurations to achieve significant fuel economy savings in urban driving. A successful implementation of the starter alternator technology includes controlling the electric motor to start and stop the engine quickly and smoothly, without compromising the vehicle noise, vibration and harshness (NVH) signature. The issue becomes more critical in the case of Diesel hybrids, as the peak compression torque is much larger than in automotive spark ignition engines. This paper presents a model-based approach in control design for engine start/stop operations with a belted starter/alternator. Starting from previous modeling and experimental results, a nonlinear model of a belted starter/alternator coupled with a Diesel engine is developed for control algorithm development. With the introduction of a feed-forward control action proportional to the instantaneous engine torque, the starter/alternator controller is capable of consistently reducing the large torque fluctuations during the engine start. With this feedforward control action, the engine start control problem can be translated into a simpler disturbance rejection problem, given a prescribed speed trajectory. This facilitates a linearization of the complex nonlinear model to produce a control-oriented model on which feedback control can be designed. Using the control-oriented model thus developed, different linear control designs have been developed and compared. Further, a robustness study is conducted to evaluate the effect of noise and uncertainties common to such systems. The final results are tested on the original nonlinear truth model, demonstrating the capability of starting and stopping the engine with very limited torque and speed fluctuations.

Engine Torque Control Based on Discrete Event Model and Disturbance Observer

This paper presents a novel control method for torque generation in four-stroke spark ignition (SI) engines. A model-based approach is employed to control engine torque output by adjusting throttle air intake with considerations of robust stability and performance. Discrete event engine model (DEM) is adopted with an addition of torque generation dynamics. Disturbance observer (DOB) techniques are utilized to achieve robust stability and performance by regarding the discrepancy between the actual plant and the nominal plant with desired plant characteristics as an equivalent disturbance input, which is estimated and cancelled. The desired plant behavior is stably realized by the DOB up to a bandwidth which is sufficient for a torque control application discussed in authors’ previous work. A switching scheme for desired nominal plant is proposed to further enhance robust performance and stability. Numerical results show the effectiveness of the proposed schem.

Cost-Effective Structural Anti-Ram Security Barriers: New Design, Computer Modeling and Test Validation

Terrorist attacks became a major threat to the safety, security, and economy of our nation in the last few years. The Attacks against important facilities could have different techniques; however the main source of ground attacks is the application of excessive amount of energy to the designated facility through a vehicle intrusion and/or a blast. In the current research, a new approach of using steel-structure barriers is presented. Several new structural anti-ramming barriers are designed and analyzed using nonlinear Finite Element Analysis (FEA). In this new design, commercial steel-structural components were used in order to reduce the manufacturing cost. These new steel-structure security devices have proven an excellent capability to sustain severe impacts by spreading substantial amount of the impact energy throughout the entire structure and the supporting soil/concrete. In the current research, three anti-ramming bollard systems, for K4, K8 and K12 impact conditions, were presented. The bollard systems were made of commercial steel unites connected together to produce the entire bollard structure. The FE modeling and simulation results of the bollard systems were presented in details in this paper. The FEA for the K4 bollard was validated by comparing the simulation results with the actual test results. The FE simulation results correlated very well with the actual test results. The steel-structure barriers could have much less shallow foundation to account for the in-city utility restrictions. It also has the advantage of easier and faster installation minimizing the required digging and installation time inside the city. The design could also be modified to account for different threat levels and different sites’ restrictions.

Validation of a New Aluminum Honeycomb Crush Model With Dynamic Impact Tests

This paper describes a process for validating a new constitutive model for large, high strain-rate deformation of aluminum honeycomb, called the Honeycomb Crush Model (HCM). This model has 6 yield surfaces that are coupled to account for the orthotropic behavior of the cellular honeycomb being crushed on-axis and off-axis. The HCM has been implemented in the transient dynamic Presto finite element code for dynamic impact simulations. The HCM constitutive parameters were identified based on Presto finite element models that were used to simulate uniaxial and biaxial crush tests of 38 lb/ft3 aluminum honeycomb and reported in an earlier paper. This paper focuses on validating the HCM in the Presto code for application to impact situations that have honeycomb crush velocities up to 85 ft/sec. Also, a new approach for incorporating rate sensitivity into the model is described. A two-stage energy absorber with integrated aluminum honeycomb is described as the configuration for dynamic impact validation experiments. The test parameters and finite element model will be described along with the uncertainty quantification that was done and propagated through the model. Finally, correlation of model predictions and test results will be presented using an energy based validation metric.

A Comprehensive Physics-Based Model for Medium-Duty Diesel Engine With Exhaust Gas Recirculation

Physics-based models of diesel engines with exhaust gas recirculation and a variable geometry turbine (EGR/VGT) have been developed extensively in the control system design community. However, these models omit the heat transfer effects of the charge-air cooler and the recirculated exhaust gas cooler in order to avoid the added complexity in model order for online implementation. Generally, there is no need to include these effects if the purpose of the model is to control the target variables, such as boost pressure and air-to-fuel ratio. In this paper, after surveying the existing state of physics-based models for the EGR/VGT subsystem, a comprehensive model of the EGR/VGT subsystem is developed. This model includes heat transfer effects in the coolers, pressure drops across air filters and pipes, and mass flow rate calculations for a variable geometry turbine and an exhaust gas recirculation control valve. The purpose and scope of this work is offline modeling-for-diagnostics. Such models, though complex, will assist in the fault sensitivity analysis of a subsystem while avoiding any destructive testing when a major design modification in the EGR/VGT subsystem is proposed. For example, the impact of charge-water or EGR cooler degradation on the boost pressure and the air-to-fuel ratio can be studied with such models to further help in designing diagnostic reasoning strategies. Simulation performed using the proposed physicsbased model demonstrates a dominant failure effect of an EGR cooler coolant leak over a charge-water cooler water leak on the properties of the intake air.