Browsing by Author "Alexander, Lee"

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Advanced BRT Volume I: Innovative Technologies for Dedicated Roadways
(University of Minnesota Center for Transportation Studies, 2008-06) Alexander, Lee; Cheng, Pi-Ming; Gorjestani, Alec; Menon, Arvind; Newstrom, Bryan; Shankwitz, Craig
Presented herein is a novel approach to vehicle positioning using RFID technology (Vehicle Positioning System, or VPS). By installing in the road RFID tags encoded with road name or other designation, the specific lane, the direction of travel, and the longitudinal distance from a known reference, a vehicle outfitted with an RFID tag reader can determine its position each time it passes over and reads a tag, thus, providing precisely the information needed for many ITS applications - the longitudinal position of a vehicle in a particular lane on a particular road of the transportation network. Knowledge of lane of travel and distance from a known reference provided by VPS enables many transit applications, including headway control of bus platoons, merge/lane change assistance, rear-end collision avoidance, and bay mark-up applications. For lane assist systems, VPS and a lateral positioning system can augment DGSP in urban areas, providing seamless operation where DGPS accuracy is insufficient for lane keeping. This research focused on designing and building a prototype VPS using existing third party RFID hardware. The hardware was evaluated and characterized to determine if it could be used to create a viable, robust VPS. After the development and characterization of the positioning system, an implementation of a rear-end collision avoidance system was built to demonstrate the use of VPS. Finally, a more sophisticated rear-end collision avoidance system was designed and simulated, after which its implications to the accuracy specifications for VPS were analyzed.
Analysis of a Differential Global Positioning System as a Sensor for Vehicle Guidance
(Minnesota Department of Transportation, 1996-09) Bodor, Robert; Alexander, Lee; Liao, Chen-fu; Bajikar, Sundeep; Morellas, Vassilios; Donath, Max
An ongoing research project examines guidance systems, which can take over control of a vehicle if the driver becomes incapacitated. Part of this project includes an evaluation of a Differential Global Positioning System (DGPS) for vehicle-based lane sensing. This report documents the results of tests of the 5 Hz NovAtel RT20 DGPS receiver. A series of 32 static tests found the overall mean and standard deviation for the offset errors within specifications. In a series of dynamic tests, in which the vehicle was driven around the track at speeds of 20-35 miles per hour, after removing the effect of the GPS receiver's latency, the DGPS determined position exhibited a mean offset error of -17.3 cm (-6.82 in) and a mean standard deviation of 25.5 cm (10.1 in) in the direction of vehicle motion. In the direction perpendicular to vehicle motion, the mean offset was 4.57 cm (1.8 in) with a mean standard deviation of 39.6 cm (15.6 in). With no overhead obstructions in these tests, continuous satellite lock was possible. Tests at higher speeds based on a more accurate methodology are planned for the future.
Automated Vehicle Location, Data Recording, Friction Measurement and Applicator Control for Winter Road Maintenance
(Minnesota Department of Transportation Research Services Section, 2010-02) Erdogan, Gurkan; Alexander, Lee; Rajamani, Rajesh
The first part of this project conducted a detailed evaluation of the ability of a new friction measurement system to provide an accurate measure of road conditions. A system that records friction coefficient as a function of road location was developed using the same vehicle location measurement system as the current MDSS project. Studies conducted show that the friction measurement system provides a significantly more reliable measure of road surface conditions than does visual inspection. The second part of this project focused on a detailed evaluation of the performance of a closed-loop system that utilizes friction measurement for automatic applicator control. Experimental studies have shown that a friction measurement based zero velocity sander can adequately apply salt/chemicals to all slippery spots on a road at speeds up to 25 mph. The final part of this project focused on enhancement of the developed automatic applicator control system with utilization of real-time data from a geographical information system that provides information on upcoming geometric road alignment and known problematic segments of roadway. The developed friction measurement, data recording and applicator control system is compact, modular and can be used on both snowplows and pick-up trucks.
Automated Winter Road Maintenance Using Road Surface Condition Measurements
(Minnesota Department of Transportation, 2007-09) Erdogan, Gurkan; Alexander, Lee; Agrawal, Piyush; Rajamani, Rajesh
Real-time measurement of tire-road friction coefficient is extremely valuable for winter road maintenance operations and can be used to optimize the kind and quantity of the deicing and anti-icing chemicals applied to the roadway. In this project, a wheel based tire-road friction coefficient measurement system is first developed for snowplows. Unlike a traditional Norse meter, this system is based on measurement of lateral tire forces, has minimal moving parts and does not use any actuators. Hence, it is reliable and inexpensive. A key challenge is quickly detecting changes in estimated tire-road friction coefficient while rejecting the high levels of noise in measured force signals. Novel filtering and signal processing algorithms are developed to address this challenge including a biased quadratic mean filter and an accelerometer based vibration removal filter. Detailed experimental results are presented on the performance of the friction estimation system on different types of road surfaces. Experimental results show that the biased quadratic mean filter works very effectively to eliminate the influence of noise and quickly estimate changes in friction coefficient. Further, the use of accelerometers and an intelligent algorithm enables elimination of the influence of driver steering maneuvers, thus providing a robust friction measurement system. In the second part of the project, the developed friction measurement system is used for automated control of the chemical applicator on the snowplow. An electronic interface is established with the Force America applicator to enable real-time control. A feedback control system that utilizes the developed friction measurement sensor and a pavement temperature sensor is developed and implemented on the snowplow.
Bus Rapid Transit Technologies: Assisting Drivers Operating Buses on Road Shoulders: Volume 1
(2003-12) Alexander, Lee; Cheng, Pi-Ming; Donath, Max; Gorjestani, Alec; Newstrom, Bryan; Shankwitz, Craig; Trach, Walter
The FTA has identified the concept of Bus Rapid Transit as a means to increase the efficiency of transit operations while maintaining transit's proven safety record. According to the FTA website www.fta.dot.gov, "BRT combines the quality of rail transit and the flexibility of buses. It can operate on exclusive transitways, HOV lanes, expressways, or ordinary streets. A BRT system combines intelligent transportation systems technology, priority for transit, cleaner and quieter vehicles, rapid and convenient fare collection, and integration with land use policy." Because of the limited right-of-way available to build new (and possibly dedicated) lanes for BRT operations, the FTA has identified lane assist as an emerging technology, which will enable deployment of BRT systems. The premise behind lane assist technology is to increase the safety of BRT vehicles as they operate in the more unique environments, such as narrow lanes. Lane assist technology will allow BRT vehicles to operate at the desired higher operating speeds while maintaining the safety of the passengers, BRT vehicle and the motoring public.
Development of a Novel Tilt-Controlled Narrow Commuter Vehicle
(2006-05-01) Gohl, J.; Rajamani, Rajesh; Starr, Patrick J.; Alexander, Lee
Traffic congestion is growing in urban areas of every size and is expected to double by 2010. A relatively unexplored but very promising solution to the problem of congestion is the adoption of narrow vehicles for commuter travel. Narrow vehicles like motorcycles can promote significantly improved highway utilization by the use of half-width lanes. However, in order for the general public to adopt this form of personal transportation, narrow vehicles should perceptibly provide the same ease of use and the same level of safety as passenger sedans. The research team in this project has developed a new concept vehicle that is relatively tall compared to its track width so as to provide a travel height that is comparable to that of other vehicles on the highway. To help the driver balance a relatively tall, narrow vehicle, it incorporates an electronic tilt control system that ensures tilt stability. The tilt control system balances the vehicle and improves ease of use, especially on curves where the vehicle must lean into the curve to ensure tilt stability. In this report the design and implementation of a control system that ensures the tilt stability of the prototype narrow vehicle is presented. The control system is based on the use of steer-by-wire technology and is called Steering Tilt Control (STC). The report includes significant details on the design of the prototype narrow vehicle constructed by the research team, on dynamic modeling for narrow tilting vehicles and also includes experimental results on the performance of the control system on the prototype narrow vehicle.
Development of Driver Assistance Systems to Support Snowplow Operations
(Center for Transportation Studies, University of Minnesota, 2018-08) Liao, Chen-Fu; Morris, Nichole L.; Achtemeier, Jacob; Alexander, Lee; Davis, Brian; Donath, Max; Parikh, Gordon
Snowplow operators are often tasked with numerous monitoring and operational activities that they need to do simultaneously while removing snow and spreading deicing agents on the road. Driver assist systems were considered for 3 applications: gang plowing, backup assist, and lane boundary guidance. We evaluated the system performance and position accuracy of commercially available Dedicated Short Range Communication (DSRC) Onboard Units (OBU) for gang plowing. Our results indicated that the positioning accuracy of the OBUs was inadequate for providing the plow operator with sufficient information to maintain spacing between two vehicles. The backup assist system and lane boundary guidance system were developed and successfully deployed to support snowplow operations. Human factors studies were also conducted using a driving simulator to better understand the needs prior to designing an appropriate Human Machine Interface (HMI) for these plow operations. The radar-based backup assist system was installed on a snowplow that operates on Highway 169. The backup assist system provides an audio warning to the operator to look at the display from a rear-view camera when an object is detected. The Global Navigation Satellite System (GNSS)-based lane boundary guidance system was developed to assist plow operations when visibility is poor and lane boundary cues are limited. The lane boundary guidance system was installed on a second snowplow operating on MN-25 running between Belle Plaine and Green Isle. The lane boundary guidance received the most positive feedback from operators and is recommended for further development.
DGPS-Based Gang Plowing
(2005-04-01) Alexander, Lee; Gorjestani, Alec; Shankwitz, Craig
Gang plowing is one method used by the Minnesota Department of Transportation (Mn/DOT) to increase the productivity of snowplow operations. However, these gains in productivity often come at the expense of increased driver stress. These higher stress levels are the result of the low visibility caused by localized snow clouds created by the lead snowplow, and by anxious drivers trying to pass between the moving plows. To improve the gang plowing process, a DGPS-based gang plowing system has been developed. This system uses advanced technology to allow a trailing snowplow to automatically follow a lead snowplow at an operator-specified lateral and longitudinal offset. The system is designed to improve both safety and productivity. This report covers three areas. First, to improve driver visibility, an implementation of the virtual mirror to the left side of the trailing plow is described. Second, the lateral and longitudinal performance of a two-vehicle gang on Minnesota Trunk Highway 101 is described. Third, a system architecture for gangs of more than two vehicles is proposed, and its potential performance is documented through simulation. Finally, recommendations for further research and other potential applications are provided.
Differential GPS Based Control of a Heavy Vehicle
(1999-01-01) Alexander, Lee; Donath, Max
This report describes the development of technologies that safely steer a vehicle if the vehicle's driver becomes incapacitated. A Differential Global Positioning System (GPS) senses the vehicle's position and velocity. This method seems to offer adequate precision with a low-enough infrastructure cost to make the system practical in most rural settings. Researchers used a heavy vehicle -- a class 8 truck tractor -- partly because of the most favorable economics associated with installation of this type of system on a commercial vehicle, and partly because of the commercial driver's higher exposure to conditions that engender drowsy driving. This research examines two potential applications of the steering, throttle, and brake controllers. The first, a virtual rumble strip, vibrates the wheel whenever the vehicle drifts out of its lane. The second, a system senses the erratic steering that presages loss of consciousness, and then takes control of the vehicle, pulling it over to a safe stop.
Driver Assistive Systems for Snowplows
(2003-03-01) Gorjestani, Alec; Alexander, Lee; Newstrom, Bryan; Cheng, Pi-Ming; Sergi, Mike; Shankwitz, Craig; Donath, Max
A comprehensive driver assistive system which utilizes dual frequency, carrier phase real time kinematic (RTK) differential global positioning system (DGPS), high accuracy digital geospatial databases, advanced automotive radar, and a driver interface with visual, haptic, and audible components has been used to assist specialty vehicle operators perform their tasks under these low visibility conditions. The system is able to provide a driver with high fidelity representations of the local geospatial landscape through a custom designed Head Up Display (HUD). Lane boundaries, turn lanes, intersections, mailboxes, and other elements of the geospatial landscape, including those sensed by automotive radar, are projected onto the HUD in the proper perspective. This allows a driver to safely guide his or her vehicle in low to zero visibility conditions in a desired lane while avoiding collisions. Four areas of research, are described herein: driver assistive displays, the integration of a geospatial database for improved radar processing, snowplow dynamics for slippery conditions, and a virtual bumper based collision avoidance/gang plowing system. (Gang plowing is the flying in formation of snowplows as a means to rapidly clear multilane roads.) Results from this research have vastly improved the performance and reliability of the driver assistive system. Research on the use of a specialized driver assistance system to assist specialty vehicle operators in low visibility conditions, including the design of a custom Head Up Display (HUD) projecting elements of the landscape in proper perspective. Driver assistive displays, the integration of a geospatial database for improved radar processing, snowplow dynamics for slippery conditions, and a virtual bumper based on collision avoidance/gang plowing system are discussed.
Fault Diagnostics for Intelligent Vehicle Applications
(2001-05-01) Rajamani, Rajesh; Shrivastava, Ankur; Zhu, Chunyu; Alexander, Lee
This project involved the development of a fault diagnostic system for Safetruck, an intelligent vehicle prototype. The fault diagnostic system continuously monitors the health of vehicle sensors, detects a failure when it happens, and identifies the source of the failure. The fault diagnostic system monitors several key components: the Global Positioning System, lateral accelerometer, and yaw-rate gyroscope, which constitute the set of lateral dynamic sensors, as well as the forward-looking radar that measures distance, relative velocity, and azimuth angle to other vehicles and objects on the highway. To design the project's lateral fault diagnostic system, researchers exploited the model-based dynamic relationships that exist between the three lateral sensors. They verified the system's performance through extensive experiments on the Safetruck. This project also explored a number of new approaches to creating a reliable fault detection system for radar. Monitoring the radar's health poses a special challenge because the radar measures the distance to another independent vehicle on the highway. In the absence of inter-vehicle communications, the fault diagnostic system has no way of knowing the other vehicle's motion, which means that model-based approaches cannot be used. Experimental results indicate that an inexpensive redundant sensor combined with a specially designed nonlinear filter would provide the most reliable method for radar health monitoring.
Friction Measurement System for Hennepin County
(Intelligent Transportation Systems Institute, Center for Transportation Studies, University of Minnesota, 2013-01) Alexander, Lee; Rajamani, Rajesh
A friction measurement system was developed for Hennepin County and installed on a snowplow in their winter road maintenance fleet. The major components of the developed system were a special instrumented wheel, a pneumatic pressure-controlled cylinder, force-measurement load cell and accelerometers, and a data processing micro-processor and LCD display. The project plan initially included interfacing the friction measurement system with an applicator and automatic control of the applicator on detection of a low tire-road friction coefficient on the road. However, due to concerns from Hennepin County about interfacing with the applicator electronics and its potential influence on normal operation of the Force America applicator, the friction coefficient was estimated in real-time and just displayed for the snowplow operator. It was not used for real-time control of the applicator. The stand-alone hardware developed in this project is being used as a platform for development and installation of friction measurement systems on two snowplows in Polk County during the 2012-2013 winter. The Polk County installation is being funded by the Minnesota Local Road Research Board.
Friction Measurement System for Polk County
(Minnesota Department of Transportation, 2013-11) Alexander, Lee; Rajamani, Rajesh
A friction measurement system was developed for Polk County and installed on two snowplows in the county’s winter road-maintenance fleet. The major components of the developed system were a special instrumented wheel, a pneumatic pressure-controlled cylinder, force-measurement load cell and accelerometers, a data collection microprocessor and a data processing micro-processor. The road friction coefficient was estimated in real-time and was stored on a secure digital card along with the current GPS-sensed location of the truck. The friction coefficient information was also displayed in real-time using LED lights for the operator. Although the basic design of the friction wheel system had been used for several previous years of intermitant testing without showing significant wear, the almost identical installations on the Polk County trucks suffered bearing failures after the first few days of continuous use. The failed bearings were replaced with larger bearings in a more robust mount. Apparently, the system again failed in a few days, but the research team did not learn of this failure until the end of the project. The low budget for the project and the significant travel required to go to Crookston posed major challenges in getting a friction measurement to work effectively for Polk County.
GPS Based Real-Time Tire-Road Friction Coefficient Identification
(2004-09-01) Wang, Junmin; Alexander, Lee; Rajamani, Rajesh
This project concentrates on the development of real- time tire-road friction coefficient estimation systems for snowplows that can reliably estimate different road surface friction levels and quickly detect abrupt changes in friction coefficient. Two types of systems are developed - a vehicle-based system and a wheel-based system. The vehiclebased friction measurement system utilizes vehicle motion measurements from differential GPS and other on-board vehicle sensors. The wheel-based friction measurement system utilizes a redundant wheel that is mounted at a small angle to the longitudinal axis of the vehicle.
Improved Approach to Enforcement of Road Weight Restrictions
(Minnesota Department of Transportation, 2013-11) Alexander, Lee; Phanomchoeng, Gridsada; Rajamani, Rajesh
This project focused on the enhancement and evaluation of a battery-less wireless weigh-in-motion (WIM) sensor for improved enforcement of road weight restrictions. The WIM sensor is based on a previously developed vibration energy harvesting system, in which energy is harvested from the vibrations induced by each passing vehicle to power the sensor. The sensor was re-designed in this project so as to reduce its height, allow it to be installed and grouted in an asphalt pavement, and to protect the piezo stacks and other components from heavy shock loads. Two types of software interfaces were developed in the project: a) An interface from which the signals could be read on the MnDOT intranet b) An interface through a wireless handheld display Tests were conducted at MnRoad with a number of test vehicles, including a semi tractor-trailer at a number of speeds from 10 to 50 mph. The sensor had a monotonically increasing response with vehicle weight. There was significant variability in sensor response from one test to another, especially at the higher vehicle speeds. This variability could be attributed to truck suspension vibrations, since accelerometer measurements on the truck showed significant vibrations, especially at higher vehicle speeds. MnDOT decided that the final size of the sensor was too big and could pose a hazard to the traveling public if it got dislodged from the road. Hence the task on evaluation of the sensor at a real-world traffic location was abandoned and the budget for the project correspondingly reduced.
Influence of Autonomous and Partially Autonomous Vehicles on Minnesota Roads
(Minnesota Department of Transportation, 2023-05) Espindola, Andre; Alexander, Lee; Rajamani, Rajesh
This project focuses on experimental tests of the performance characteristics of autonomous vehicles (AVs) on highways and local roads in Minnesota. The project provides detailed data characterizing AV performance, which in turn can be used to inform the transportation community on implications for infrastructure maintenance, winter road maintenance, work zone guidelines, safety, and traffic capacity. The experimental work presented here makes use of a new autonomous vehicle purchased by the Center for Transportation Studies at the University of Minnesota. The key aspects of the autonomous functions of the vehicle studied in this project include winter performance and implications for road maintenance, characterization of the driving performance of the AV and its likely influence on safety, traffic flow and fuel economy, and the ability of the AV to handle work zones and the implications on changes needed to the guidelines for work zones. The project documents the major challenges and obstacles ahead in the way of true autonomy on Minnesota roads, but also outlines further areas for research with which it will be possible to facilitate the improvement of the capabilities of autonomous vehicles in Minnesota in the future.
Instrumentation of Navistar Truck for Data Collection
(Minnesota Department of Transportation, 2013-01) Alexander, Lee; Phanomchoeng, Gridsada; Rajamani, Rajesh
The overarching goal of this project was to instrument the new MnDOT Navistar truck used at MN Road. A rugged data acquisition, data recording and wireless transmission system was established for collection of various sensor signals from the truck. The truck was instrumented with a suite of 20 accelerometers, with these accelerometers being located both on the five axles of the truck and on the tractor and trailer bodies. In addition, the truck was instrumented with a differential GPS system and an inertial measurement unit in the tractor cab. A cRIO-based data acquisition system, a rugged laptop and Labview software together serve as a flexible platform for data acquisition. A wireless communication system has been established to communicate trigger signals to roadside cabinets when the truck is at desired GPS locations on the road. Data recording by in-pavement sensors is triggered by this system. Software has also been set up for automatic downloading of data from the truck to a server on the network at MN Road. The experimental performance of the developed system has been verified by multiple tests conducted by the research team. The above instrumentation of the truck will enable data collection on truck vibrations, enable analysis of correlations between truck vibrations and variations in signals of weigh-inmotion sensors, and enable recording of truck movements and pavement loads at MnROAD.
Intersection Decision Support Surveillance System: Design, Performance and Initial Driver Behavior Quantization
(Minnesota Department of Transportation, 2007-08) Alexander, Lee; Cheng, Pi-Ming; Donath, Max; Gorjestani, Alec; Menon, Arvind; Shankwitz, Craig
In rural Minnesota, approximately one-third of all crashes occur at intersections. Analysis of crash statistics and reports of crashes at rural expressway through-stop intersections shows that, for drivers who stop before entering the intersection, the majority of crashes involve an error in selecting a safe gap in traffic. The Intersection Decision Support system, developed at the University of Minnesota, is intended to reduce the number of driver errors by providing better information about oncoming traffic to drivers stopped at intersections. This report deals primarily with the surveillance technology which serves as the foundation upon which the IDS system will be built. Three components of the surveillance system are described in detail in the body of the report: 1) a Mainline Sensor subsystem; 2) a Minor Road Sensor subsystem; 3) a Median Sensor subsystem. These subsystems include radar units, laser-scanning sensors, and infrared cameras, integrated with a vehicle tracking and classification unit that estimates the states of all vehicles approaching the intersection. The design, installation, performance, and reliability of each of these three subsystems are documented in the report. The report concludes with an analysis of driver gap acceptance behavior at an instrumented intersection. Gap selection is examined as a function of time of day, traffic levels, weather conditions, maneuver, and other parameters. Log-normal distributions describe gaps acceptance behavior at rural, unsignalized expressway intersections.
A Lateral Dynamic Model of a Tractor-Trailer: Experimental Validation
(1996-11) Alexander, Lee; Donath, Max; Hennessey, Michael; Morellas, Vassilios; Shankwitz, Craig
The SAFETRUCK program focuses on preventing accidents on rural highways, especially those associated with run-off-the-road incidents and driver fatigue, by giving the vehicle the ability to steer to the side of the road and come to a safe stop if the driver falls asleep or is otherwise incapacitated. Researchers have equipped a Navistar 9400 series class 8 truck tractor with the sensors and control computers necessary to perform this task. Designing the controller that will steer the truck requires a mathematical model of the lateral response of the truck to steering inputs. In this project, researchers developed a lateral dynamic model by incorporating second order dynamics into the steering axle tires. Simulation of the resulting models indicated dynamic behavior that was close to the experimental data for speeds between 15 and 30 miles per hour. This is the first time that a lateral dynamic model of a truck has been experimentally verified. Both models, however, resulted in experimentally determined values for steering axle cornering stiffness that were considerably smaller than published values for the Goodyear G 159 tires on the truck.
Methods of corn breeding
(University of Minnesota. Agricultural Experiment Station, 1924-04) Hayes, H.K.; Alexander, Lee

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