Bapiraju Surampudi

Autonomous ground vehicle control system for high-speed and safe operation

This paper describes a new Autonomous Ground Vehicles (AGVs) trajectory tracking control system towards safe and high-speed operations enabled by incorporating Vehicle Dynamics Control (VDC). The system consists of an AGV desired yaw rate generator based on a kinematic model, and a yaw rate controller based on the vehicle/tyre dynamic models. Sliding Mode Control (SMC) is used to handle the system uncertainties. The performance of the control system was evaluated by using a high-fidelity (experimentally validated) full-vehicle Sport Utility Vehicle (SUV) model provided by CarSim®. Compared with the results of position-error-based AGV control, significant performance improvement was observed.

Evaluation of autonomy in recent ground vehicles using the autonomy levels for unmanned systems (ALFUS) framework

Over the last few decades, the field of unmanned systems (UMSs) has begun to emerge into a variety of markets. The military has already deployed unmanned air, sea, and ground vehicles. Universities and other research institutions have developed semi-autonomous passenger vehicles that have driven on highways in the U.S. and abroad. The National Aeronautics and Space Administrations (NASA) has developed unmanned rovers that have been navigating the planet Mars for several years. Even the transit and commercial freight market has developed programs for unmanned vehicles research to help solve complex logistics issues. In order to compare the capabilities of unmanned systems in such a wide variety of markets, the Autonomy Levels for Unmanned Systems (ALFUS) framework has been established in a series of workshops. While this framework is still under some development, it can be used in its current state to compare unmanned systems. In this paper, we highlight some of the major accomplishments made in the field of ground vehicle autonomy in particular. We then map the capabilities of these ground vehicles to the ALFUS framework and summarize the resulting trends that occur from this mapping.

Modeling, Simulation, and Hardware-in-the-Loop Transmission Test System Software Development

This paper describes the development of a generic test cell software designed to overcome many vehicle-component testing difficulties by introducing modern, real-time control and simulation capabilities directly to laboratory test environments. Successfully demonstrated in a transmission test cell system, this software eliminated the need for internal combustion engines (ICE) and test-track vehicles. It incorporated the control of an advanced AC induction motor that electrically simulated the ICE and a DC dynamometer that electrically replicated vehicle loads. Engine behaviors controlled by the software included not only the average crankshaft torque production but also engine inertia and firing pulses, particularly during shifts. Vehicle loads included rolling resistance, aerodynamic drag, grade, and more importantly, vehicle inertia corresponding to sport utility, light truck, or passenger cars. Driver aggressiveness algorithms that compensated for sensitivity to high grade, forward/reverse driving, and extremely high speeds were also incorporated to properly track a variety of severe driving profiles. Test results validating the operation of the system against actual vehicle data is also included. The paper summarizes the elements required to accomplish these tasks.

42-Volt Electric Air Conditioning System Commissioning and Control for a Class-8 Tractor

The electrification of accessories using a fuel cell as an auxiliary power unit reduces the load on the engine and provides opportunities to increase propulsion performance or reduce engine displacement. The SunLine Class 8 tractor electric accessory integration project is a United States Army National Automotive Center (NAC) initiative in partnership with Cummins Inc., Dynetek Industries Ltd., General Dynamics C4 Systems, Acumentrics Corporation, Michelin North America, Engineered Machine Products (EMP), Peterbilt Motors Company, Modine Manufacturing and Masterflux. Southwest Research Institute is the technical integration contractor to SunLine Services Group. In this paper the SunLine tractor electric Air Conditioning (AC) system is described and the installation of components on the tractor is illustrated. The AC system has been designed to retrofit into an existing automotive system and every effort was made to maintain OEM components whenever modifications were made. Hardware modifications were limited to replacing the engine driven compressor for a 42 volt DC driven one, exchanging the expansion orifice for a thermal expansion valve and positioning the components to minimize the length of refrigerant lines. The thermodynamics and PID control algorithms are discussed. Closed loop test results are presented in controlled ambient conditions. Analysis of reversed Carnot cycle changes due to transient operation and coefficient of performance changes are given. INTRODUCTION The engine driven air conditioning system on the 2002 Peterbilt 385 is used for maintaining a comfortable incab temperature and as a windshield defroster. The Original Equipment Manufacturer (OEM) system includes a Sanden SD7 engine driven compressor that draws approximately 6 kW at full load. One disadvantage of this compressor is that it is the same one that is used on all of their trucks, and therefore it is sized for the trucks with the full size sleeper. Peterbilt and Modine engineers have designed this system to provide up to 25000 BTU/hr of cooling. Other disadvantages of having the engine driven compressor include constant parasitic losses from clutch drag, inability to operate the compressor in its efficient zones, and packaging.

Electric Air Conditioning for Class 8 Tractors

Air conditioning and heating of heavy-duty truck cabs is an important contributor to engine efficiency, fuel economy and driver comfort. The air conditioner condenser coil and engine radiator typically share a common cooling fan, making it necessary to run the large engine cooling fan to provide condenser cooling. Engagement of the radiator cooling fan consumes a large amount of energy, further contributing to engine exhaust and noise emissions. Even under moderate temperature conditions, when the conventional enginedriven air conditioning compressor is not in use, the belt drive system adds a small speed-dependent parasitic load to the engine. Electrically driven air conditioning systems have the potential for lower energy consumption than their mechanical counterparts: Electrically driven air conditioning systems can reduce engine idle time by decoupling the air conditioner system from the engine cooling fan while offering near zero parasitic load when not in use. This paper covers the design, integration, and testing of an electric air conditioning system for a Class 8 tractor for day cab cooling and is a continuation of the efforts initially published in SAE paper 2004-01-1478 [1]. A 42 VDC electric air conditioning system consisting of a variable speed compressor, remote condenser with a variable speed cooling fan, and a thermostatically controlled expansion valve was integrated into an existing Class 8 tractor. The OEM evaporator, in-vehicle ducting, and air speed control were unmodified. The electrical power for the electrified air conditioning system is supplied by a fuel cell auxiliary power unit. The Class 8 tractor has been in-service in the desert of Southern California. Included in the paper is a detailed description of the different control schemes examined and the control scheme implemented. Energy consumption and driver comfort for each scheme is evaluated. Future system improvements and possible system enhancements are also identified. All work has been performed at Southwest Research Institute and SunLine Transit Agency and is funded by the US Army RDECOM TARDEC National Automotive Center (NAC).