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Technical Paper

A Compact Temperature Control System for Lean Exhaust Gas to Improve Conversion Performance of NOx Aftertreatment

A compact exhaust gas temperature control unit is presented. The unit was fitted to a gasoline direct injection production car together with a modified exhaust system. It was shown that it was possible to keep the exhaust gas temperature within the lean operational NOx temperature window of typical NOx absorption catalysts for the whole European drive cycle. This should improve the lean NOx conversion of such a catalyst system significantly. It was shown that the standard vehicle cooling system should be able to cope with the additional heat input from the temperature control unit without major modifications.
Technical Paper

A Comparative Analysis of Active and Passive Emission Control Systems Adopting Standard Emission Test Cycles

The aim of the present work is to analyse and compare the energetic performances and the emissions conversion capability of active and passive aftertreatment systems for lean burn engines. To this purpose, a computational one-dimensional transient model has been developed and validated. The code permits to assess the heat exchange between the solid and the exhaust gas, to evaluate the conversion of the main engine pollutants, and to estimate the energy effectiveness. The response of the systems to variations in engine operating conditions have been investigated considering standard emission test cycles. The analysis highlighted that the active flow control tends to increase the thermal inertia of the apparatus and then it appears more suitable to maintain higher temperature level and to guarantee higher pollutants conversion at low engine loads after long full load operation.
Journal Article

A Comparison between One- and Two-Loop ATCS Architectures Proposed for CEV

In an effort to help future crewed spacecraft thermal control analysts understand the characteristics of one-and two-loop Active Thermal Control Systems (ATCS), a comparison was made between the one- and two-loop ATCS architectures officially proposed for the Crew Exploration Vehicle (CEV) in Design Analysis Cycle 1 (DAC1) and DAC2, respectively. This report provides a description of each design, along with mass and power estimates derived from their respective Master Equipment List (MEL) and Power Equipment List (PEL). Since some of the components were sized independent of loop architecture (ex. coldplates and heat exchangers), the mass and power for these components were based on the MEL and PEL of the most mature design (i.e. two-loop architecture). The mass and power of the two architectures are then compared and the ability of each design to meet CEV requirements is discussed.
Technical Paper

A Comparison of Different Methods for Battery and Supercapacitor Modeling

In future vehicles (e.g. fuel cell vehicles, hybrid electric vehicles), the electrical system will have an important impact on the mechanical systems in the car (e.g. powertrain, steering). Furthermore, this coupling will become increasingly important over time. In order to develop effective designs and appropriate control systems for these systems, it is important that the plant models capture the detailed physical behavior in the system. This paper will describe models of two electrical components, a battery and a supercapacitor, which have been modeled in two ways: (i) modeling the plant and controller using block diagrams in Simulink and (ii) modeling the plant and controller in Dymola followed by compiling this model to an S-function for simulation in Simulink. Both the battery and supercapacitor model are based on impedance spectroscopy measurements and can be used for highly dynamic simulations.
Technical Paper

A Comparison of Different Squeak & Rattle Test Methods for Large Modules and Subsystems

Many engineers today use large, powerful multi-purpose test systems to do squeak & rattle testing of modules and subsystems such as Instrument Panels, Consoles and Seat Assemblies. Such test systems include Multi-Axis Hydraulic Shaker Tables and Electrodynamic Vibration Systems with large head expanders and rigid (or at least stiff) fixtures. These test systems have been successful when used for squeak & rattle test programs, have been validated as approved test methods, and have become the standards of comparison in many labs today. They are, however, expensive and throughput can be limited due to the time needed to unbolt, unload, handle, load, and re-bolt a test item at its many attachment points on the rigid fixture. Furthermore, the capital cost of these Legacy systems can be prohibitive, especially for the smaller supplier, who is being compelled to perform squeak & rattle testing on the products they supply to their customers, the vehicle manufacturers and Tier 1 suppliers.
Technical Paper

A Comparison of Refueling Emissions Control With Onboard and Stage II Systems

A comparison of alternative methods for the control of motor vehicle refueling emissions indicates that Stage II control systems installed at gasoline service stations can provide greater control at lower cost than Onboard control systems installed on motor vehicles. In addition, Stage II control can be achieved with a shorter implementation schedule. Because of this advantage, Stage II controls can achieve more than twice the hydrocarbon reductions possible with Onboard systems during the next ten years, when additional reductions are needed to meet the ambient air quality standard for ozone. Several assumptions are critical to a comparison of Stage II and Onboard controls. These include service station population and size cut-offs, whether “breathing loss” emissions are considered, system cost and lead time, and whether additional evaporative emission controls are considered under both Stage II and Onboard control programs.
Technical Paper

A Comparison of Two Optimal Preview Driver Models for Automobile Directional Control

A systematic comparison between the two position preview driver models, the optimal preview acceleration model and the optimal preview control model for directional control has been carried out in this paper by means of the theoretical analysis and the digital simulation. The comparison results indicate that the optimal preview control model belongs essentially to the second order following control system, and its following performance is not so good as the optimal preview acceleration model in which the order number is greater than 2. Also, the results from the double-lane-change experiment of the closed-loop system show that the control strategy of most real drivers is basically corresponding to the so-called second-and-half-order optimal preview acceleration model.
Technical Paper

A Comparison of Two Soft-Sensing Methods for Estimating Vehicle Side Slip Angle

Two soft-sensing methods which are neural network and Kalman filter for estimating vehicle side slip angle are compared. A radial basis function (RBF) neural network based soft-sensing model is proposed to estimate vehicle side slip angle in driver-vehicle closed-loop system. Vehicle side slip angle is considered as mapping of time series of yaw rate and lateral acceleration which are easily measured, the nonlinear mapping relationship of the three state parameters is established through neural network. In addition the method based on Kalman filter is also given. The results of comparison between estimation and measurement show that the neural network method proposed in this paper has higher accuracy and less computation requirement. It can provide theoretical guidance for design of estimator in vehicle stability control system.
Journal Article

A Comparison of the Apollo and Early Orion Environmental Control, Life Support and Active Thermal Control System's Driving Requirements and System Mass

The Orion Crew and Service Modules are often compared to the Apollo Command and Service Modules due to their similarity in basic mission objective: both were dedicated to getting a crew to lunar orbit and safely returning them to Earth. Both spacecraft rely on the environmental control, life support and active thermal control systems (ECLS/ATCS) for the basic functions of providing and maintaining a breathable atmosphere, supplying adequate amount of potable water and maintaining the crew and avionics equipment within certified thermal limits. This assessment will evaluate the driving requirements for both programs and highlight similarities and differences. Further, a short comparison of the two system architectures will be examined including a side by side assessment of some selected system's hardware mass.
Technical Paper

A Comprehensive Approach to Design of Embedded Real-Time Software for Controlling Mechanical Systems

In this paper, we present a comprehensive approach to design of embedded real-time software for electrically controlled mechanical systems in automotive applications. As a case study, we implement a Gear change and Clutch controller for a Formula SAE car. This includes a generic communication interface and protocol for CAN bus communication, I/O interfaces for A/D conversion and PWM output, together with a PID controller for clutch actuation. Under our framework, the embedded software is developed using Timber, a programming language and formalism that provides executable models for embedded real-time systems. The case study shows how a complete control system can be straightforwardly modeled, simulated and transformed into executable code. The system has been realized and tested onto a lightweight, 8-bit AVR-5, embedded platform. Compared to the raw C code design flow, the proposed framework has in our case study showed increased efficiency with respect to development time.
Technical Paper

A Computer Aided Engineering Tool for ECLS Systems

This paper presents an overview of the Computer Aided Systems Engineering and Analysis (CASE/A)-ECLSS series which is designed as a generalised ECLSS design and analysis package. This system was developed under NASA MSEC contract NAS8-36407 to meet the Systems Analysis requirements of the Space Station ECLSS. The Space Station represents an order of magnitude increase in complexity over current Spacecraft technologies and will seriously tax current analysis techniques. This program is capable of simulating atmospheric revitalization systems, water recovery and management systems, and single phase active thermal control systems. The program evolved from both the G189A and the SINDA programs and shares the G189A architectural concepts. The designer/ analysis interface is graphics based and allows the designer to build a model by constructing a schematic of the system under consideration.
Technical Paper

A Contact-Point Type Start of Injection Sensor for Diesel Engines

A simple contact-point based start of injection sensor has been developed for use in closed-loop injection timing control systems. The main element in this sensor is a highly durable thin film deposited by an advanced ion plating process. This sensor is expected to provide accurate detection of start of injection over all speed ranges. Sensor transient response in the feedback loop is also expected to be fast compared to other types of sensors. This detecting method can easily be applied to many kinds of injectors because of its simple structure. The durability has been confirmed by extensive testing.
Technical Paper

A Continuously Variable Transmission for Automotive Fuel Economy

The use of a high efficiency, continuously variable transmission (CVT) with a wide ratio range is required in order to operate an automotive engine at minimum brake specific fuel consumption (bsfc). Such operation will increase fuel economy from 20-40% over conventional practice. This paper describes a 12:1 ratio range CVT, and shows a simplified control system capable of allowing a vehicle to operate with the engine at or very near minimum bsfc under all demand power conditions for optimized fuel economy. Also described is the effect such a transmission has on vehicle performance and raises the possibility of reducing engine size to maintain normal performance, and further increase fuel economy.
Technical Paper

A Control Algorithm for Low Pressure - EGR Systems Using a Smith Predictor with Intake Oxygen Sensor Feedback

Low-pressure cooled EGR (LP-cEGR) systems can provide significant improvements in spark-ignition engine efficiency and knock resistance. However, open-loop control of these systems is challenging due to low pressure differentials and the presence of pulsating flow at the EGR valve. This research describes a control structure for Low-pressure cooled EGR systems using closed loop feedback control along with internal model control. A Smith Predictor based PID controller is utilized in combination with an intake oxygen sensor for feedback control of EGR fraction. Gas transport delays are considered as dead-time delays and a Smith Predictor is one of the conventional methods to address stability concerns of such systems. However, this approach requires a plant model of the air-path from the EGR valve to the sensor.
Technical Paper

A Control Oriented Model Development for a Gas Control Path with a Stepper Motor-Based Actuator for a Gas Engine

In today's automotive power train control, the usage of model based control system is getting more focused because of the advantages associated with this approach. The model-based system can be implemented to predict and control different control parameters associated with Power train control. As a part of this work a multivariable control oriented model is developed to control the inlet manifold airflow of a small S.I. engine running on Gas. A stepper motor-based actuator is placed on the gas flow control path. A model based controller approach is adopted to control the actuator, which is placed on the low-pressure tube with inlet manifold to control the gas flow. In the initial phase of work, a state based non-linear model is developed for the actuator. This model captures the total dynamics of a permanent magnet stepper motor-based flow control device in a state space model. Different parameters for the model are calculated using system identification methodology.
Technical Paper

A Control Strategy for Kickback Reduction using Electric Power Steering and Combined Chassis Control

Good road feel means that the driver can interpret road conditions through the steering wheel. This is one of the most important requirements demanded by car makers. However, over-sensitivity in steering transmission could cause inconvenience to the driver especially maneuvering on rough roads and hence must be isolated by the steering system or by other means. To overcome this, firstly we have to distinguish diverse road conditions and apply appropriate control strategy. In this paper we've proposed two control strategies to enhance steering performance on rough roads. The first method analyzes motor position signal of Electric Power Steering (or EPS) where the road roughness is separated from the motor position signal through signal processing. The roughness then is compensated for by using EPS to obtain a better steering feel. The second method utilizes CAN transferred vehicle information from Continuous Damping Control system (or CDC).
Technical Paper

A Control System Methodology for Steer by Wire Systems

Steer by Wire systems provide many benefits in terms of functionality, and at the same time present significant challenges too. Chief among them is to make sure that an acceptable steering feel is achieved. Various aspects of this subjective attribute will be defined mathematically. A control system that is architected specifically to meet these challenges is presented. Furthermore, the design is made such that it would be robust to tire and loading variations. Supporting vehicle data and model results are shown as needed.
Technical Paper

A Control System for Managing and Replenishing Nutrient Solution Based on Electrical Conductivity

An automated nutrient replenishment system has been developed in order to provide a constant electrical conductivity (EC) value for the nutrient solution over the period of plant growth. A single nutrient film technique (NFT) system developed by the Tuskegee University NASA Center was equipped with the EC control system for growth trials with sweetpotatoes. The system is completely controlled and monitored by a PC through the use of LabView instrumentation and data acquisition software. A submersible EC probe driven by an EC controller measures the EC of the nutrient solution reservoir. EC values are passed from the controller to the PC through analog outputs. If the EC is outside a given range, the PC sends a signal to one of two solenoid valves that allow concentrated stock solution or deionized water to enter the reservoir to either raise or lower the EC respectively. For this application the set point is 1200μS cm-1, with a dead band from 1180 to 1220μS cm-1.
Technical Paper

A Coordination Approach for DYC and Active Front Steering

Integrating chassis control systems can lead to improvements in the safety, efficiency of action and overall production of a modern car. The sharing of information between chassis sub-systems allows the controller to take the optimum course of action since it has more than one option to affect the dynamics of a vehicle. This paper investigates the principle of coordination of chassis subsystems by selecting active steering and yaw stability control. A controller that coordinates the action of active front steering(AFS) and direct yaw moment control(DYC) is proposed. Preliminary results for the coordinated controller using limit handling tests suggest that such an integrated approach can lead to overall improvements in vehicle dynamic response.
Technical Paper

A Cylinder Pressure Sensor for Spark Advance Control and Knock Detection

A cylinder pressure time history has long been used as an indication of the performance of internal combustion engines. Recently the use of cylinder pressure has been proposed for the knock adaptive closed loop control of spark advance (1, 2)*. The ultimate practicality of such a scheme depends heavily on the cost and reliability of a sensor to make this measurement. This paper describes the design, associated analysis, and the experimental performance of a potentially inexpensive sensor. The transducer is shown to be suitable for determination of the crank angle at the peak cylinder pressure and for detection of incipient detonation through the associated high frequency cylinder pressure oscillations. Furthermore, implementation of the sensor in a closed loop spark control system is briefly described. The sensor has proven to be adequate for spark advance control purposes.