Lecture_15_Collision detection and avoidance

nullVehicle System DynamicsVehicle System DynamicsProfessor You-Qun ZhaoLecture 15 Review and OutlineLecture 15 Review and OutlineReview of Previous Lecture Intelligent Transportation Systems (ITS) Advanced Traffic Management Systems (ATMS) Advanced Traveler Information Systems (ATIS) Commercial Vehicle Operations (CVO) Advanced Vehicle Control Systems (AVCS) AVCS I: vehicle-based systems to enhance safety, reduce congestion, etc. AVCS II: cooperative driver-vehicle-highway systems (e.g., platooning) AVCS III: complete automation of the riving task on limited access highways Today’s topics collision detection and avoidance Collision Detection and AvoidanceCollision Detection and AvoidanceTraditional (“passive”) safety is based on crashworthiness Active safety is gaining importance: Continuous progress in the passive safety systems has pushed the technology into a return/cost plateau Corporate Average Fuel Economy (CAFE) standards requires lower vehicle weight. However, it has been verified consistently that vehicle weight is the third most important safety attribute for automobiles (after safety belts and air bags). Active safety: This is a key motivation for AVCS One of the important motivations for AVCS technologies is safety, and a key safety technology is collision detection and avoidance systemsEnabling Technologies for Active SafetyEnabling Technologies for Active SafetyA lot of the enabling technologies and subsystems will have been widely available on passenger vehicles by 2005 (Table). The add-on complexity and cost will thus be much reduced. This fact, together with the diminishing returns that has been obvious in passive safety devices, has made active safety technologies (AST) look attractive in the long-run. Collision Detection & Avoidance SystemsCollision Detection & Avoidance SystemsMust detect objects in the vehicle near-field: Ultrasonic, infrared, laser, video imaging, and radar have been suggested as the most plausible sensing devices Must operate under adverse conditions (lighting, weather, clutter) Must interpret the sensed information correctly: Vehicle and obstacles are typically both moving at high speeds Roadway environment includes signs, barriers, various types of markings, etc. Must act in some appropriate manner: Warnings Intervention ControlCollision Detection & Avoidance SystemsCollision Detection & Avoidance SystemsTypical vehicle-highway obstacle detection scenario might combine: long-range forward detection system (e.g., radar). shorter range forward and rear obstacle detection systems (e.g., ultrasonic), or even short-range side detection systems. Some "blind spots" may remain depending on sensor placement and range.Collision Detection & Avoidance SystemsCollision Detection & Avoidance SystemsThe presence of many stationary roadside objects, such as trees/shrubs, guardrails, and signposts make the problem of processing sensor information quite complex. The information available on the vehicle may be from its own near field sensors, and/or transmitted to the vehicle from other vehicles and from the roadway. Example Scenario from Smart Cruise ProjectExample Scenario from Smart Cruise ProjectOverhead vision systems are currently being used in a SMART CRUISE demonstration project in Tsukuba City, Japan to monitor traffic flows for use in vehicle navigation systemsCollision WarningsCollision WarningsA collision warning signal is triggered based on two types of indexes. Both of which are popular and used widely. Time to Collision (TTC): Simple use of range over range rate will give a reasonable index for collision warning. Based on engineering judgment, this index is usually selected to be between 5-8 seconds. Safe distance: Based on physics, a "safe following distance" d can be constructed, which has a form like: where Vc is the controlled (host) vehicle speed, td is the delay time, which can consists of human NM delay plus judgment time. Vl is the lead vehicle speed, and ac and al are deceleration limits, and are usually assumed to be the same, but change with environment (e.g. 4.5 for dry road, 3.3 for wet road, etc.) Lecture 15 Summary Lecture 15 Summary Collision detection and avoidance Passive vs. active safety Sensors for obstacle detection Warnings, intervention and control