27-06-2012, 03:39 PM
ACC systems
[attachment=25784]
INTRODUCTION
In this report the structure and functionality of ACC systems are discussed in detail. Although development of ACC systems begin in the late seventies, marketing is now possible after significant progress in both sensor and signal processing technologies. Sensors, on one hand, need to measure accurately the distance and relative speed to preceding vehicles, be easily and cheaply producible, and must meet the strict requirements of the automotive market. On the other hand, the signal processing must guarantee the desired resolution of the processed data while keeping rigorous timing constraints. Progress in these areas was partly triggered by the PROMETHEUS project, an European project involving all European research project involving all European car manufacturers, initializing similar activities in Japan and U.S.
In this report, the main components, which typically make up such an ACC system, are described. The control strategy and the system architecture of ACC system are
explained. Then the principal limits, safety assured, as well as the simulated effects on the traffic flow are pointed out.
HISTORICAL SURVEY
At the dawn of 21century, the enormous increase of vehicles has made the prevention of vehicle collision important. At the same time, with the prosperous of highway systems, drivers need only keeping the same distance and speed with respect to the preceding vehicle once they are on the highways. Cruise control offers the advantage of reducing fatigue for drivers, since they can change their position and not necessarily hold one foot on the acceleration pedal. Automated transmission slows the vehicle if it comes within a three-second range of a vehicle in front of it. The controlled declaration alerts the driver to take additional corrective action in order to maintain safe operation of the vehicle. In addition, the steady speed avoids inadvertent acceleration, enhancing both safety and compliance with speed limit. Furthermore, such an operation is more economical. The Adaptive Cruise Control and the Collision Warning System work together to supplement a driver's own sense of road conditions. Crowded highways and inclement weather compound the complexity of driving while monitoring all the onboard systems in a commercial truck. The Collision Warning System assists the driver by advising when a vehicle encroaches upon the truck's safety zone. The Adaptive Cruise Control goes a step farther by automatically slowing the vehicle, giving the driver additional time to act.
With all these advantages, adaptive cruise control becomes more important at present time. The adaptive cruise control is a critical technology for future intelligent transportation systems. It can be integrated with steering, brakes, suspension, sensors to provide more comfortable and advanced vehicle dynamics and safety. Due to the overwhelming processing speed of microprocessor, the control system underlying adaptive cruise control is chosen digital control system. The digital control systems not only have great ability two integrate several-sensed input signal with complex algorithm to process them but also have relative competitive cost.
ACC COMPONENTS
OVERVIEW:
The ACC system is built as a distributed system using common Electronic Control Units (ECUs)plus one additional ECU, which contains the Range Sensor and the ACC controller. The different ECUs are connected via a CAN data bus. The actual components are displayed in fig. 1.
The combined Range Sensor and ACC controller is mounted in front of a car. The curve Sensor helps to predict the future course of vehicle. A man Machine-Interface (MMI) includes all the interfaces of ACC system to the driver: the operation switches, the display and the pedals (accelerator, brake). The actuators in the ACC System are slightly modified standard ECUs for engine control (EGAS, EDC), transmission control and active brake control ( small addition to ASR or Vehicle Dynamic Control (VDC)). An electronic brake control system is optional depending on the characteristic traffic conditions. In unsteady traffic conditions, a significant gain of functionality is achieved by the active brake control.
RANGE SENSOR
The range sensor is the key component of ACC. It has to supply the ACC controller with data about the position and speed of preceding vehicle relative to the ACC equipped vehicle. The considered ACC system contains a mm-wave Radar sensor in the 77 GHz frequency range. With the FMCW modulation (frequency modulated continuous wave) resolutions of better than 1 m distance and 0.5 m/s in relative speed are achieved. Not only this but also the lateral position or the angle relative to the vehicles longitudinal axis is important to select the relevant preceding vehicle. An angular resolution of better than 1 deg. Within a range between + & -0.5 deg can be achieved using multi-beam techniques. This results in better detection on curved roads.
[attachment=25784]
INTRODUCTION
In this report the structure and functionality of ACC systems are discussed in detail. Although development of ACC systems begin in the late seventies, marketing is now possible after significant progress in both sensor and signal processing technologies. Sensors, on one hand, need to measure accurately the distance and relative speed to preceding vehicles, be easily and cheaply producible, and must meet the strict requirements of the automotive market. On the other hand, the signal processing must guarantee the desired resolution of the processed data while keeping rigorous timing constraints. Progress in these areas was partly triggered by the PROMETHEUS project, an European project involving all European research project involving all European car manufacturers, initializing similar activities in Japan and U.S.
In this report, the main components, which typically make up such an ACC system, are described. The control strategy and the system architecture of ACC system are
explained. Then the principal limits, safety assured, as well as the simulated effects on the traffic flow are pointed out.
HISTORICAL SURVEY
At the dawn of 21century, the enormous increase of vehicles has made the prevention of vehicle collision important. At the same time, with the prosperous of highway systems, drivers need only keeping the same distance and speed with respect to the preceding vehicle once they are on the highways. Cruise control offers the advantage of reducing fatigue for drivers, since they can change their position and not necessarily hold one foot on the acceleration pedal. Automated transmission slows the vehicle if it comes within a three-second range of a vehicle in front of it. The controlled declaration alerts the driver to take additional corrective action in order to maintain safe operation of the vehicle. In addition, the steady speed avoids inadvertent acceleration, enhancing both safety and compliance with speed limit. Furthermore, such an operation is more economical. The Adaptive Cruise Control and the Collision Warning System work together to supplement a driver's own sense of road conditions. Crowded highways and inclement weather compound the complexity of driving while monitoring all the onboard systems in a commercial truck. The Collision Warning System assists the driver by advising when a vehicle encroaches upon the truck's safety zone. The Adaptive Cruise Control goes a step farther by automatically slowing the vehicle, giving the driver additional time to act.
With all these advantages, adaptive cruise control becomes more important at present time. The adaptive cruise control is a critical technology for future intelligent transportation systems. It can be integrated with steering, brakes, suspension, sensors to provide more comfortable and advanced vehicle dynamics and safety. Due to the overwhelming processing speed of microprocessor, the control system underlying adaptive cruise control is chosen digital control system. The digital control systems not only have great ability two integrate several-sensed input signal with complex algorithm to process them but also have relative competitive cost.
ACC COMPONENTS
OVERVIEW:
The ACC system is built as a distributed system using common Electronic Control Units (ECUs)plus one additional ECU, which contains the Range Sensor and the ACC controller. The different ECUs are connected via a CAN data bus. The actual components are displayed in fig. 1.
The combined Range Sensor and ACC controller is mounted in front of a car. The curve Sensor helps to predict the future course of vehicle. A man Machine-Interface (MMI) includes all the interfaces of ACC system to the driver: the operation switches, the display and the pedals (accelerator, brake). The actuators in the ACC System are slightly modified standard ECUs for engine control (EGAS, EDC), transmission control and active brake control ( small addition to ASR or Vehicle Dynamic Control (VDC)). An electronic brake control system is optional depending on the characteristic traffic conditions. In unsteady traffic conditions, a significant gain of functionality is achieved by the active brake control.
RANGE SENSOR
The range sensor is the key component of ACC. It has to supply the ACC controller with data about the position and speed of preceding vehicle relative to the ACC equipped vehicle. The considered ACC system contains a mm-wave Radar sensor in the 77 GHz frequency range. With the FMCW modulation (frequency modulated continuous wave) resolutions of better than 1 m distance and 0.5 m/s in relative speed are achieved. Not only this but also the lateral position or the angle relative to the vehicles longitudinal axis is important to select the relevant preceding vehicle. An angular resolution of better than 1 deg. Within a range between + & -0.5 deg can be achieved using multi-beam techniques. This results in better detection on curved roads.