| 1. |
- Anderson, Sterling J., et al.
(author)
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A Unified Approach to Semi-Autonomous Control of Passenger Vehicles in Hazard Avoidance Scenarios
- 2009
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In: IEEE 2009 IEEE International Conference on Systems, Man and Cybernetics, SMC 2009, VOLS 1-9. - Piscataway, N.J. : IEEE Press. - 9781424427932 ; , s. 2032-2037
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Conference paper (peer-reviewed)abstract
- This paper describes the design of unified active safety framework that combines trajectory planning, threat assessment, and semi-autonomous control of passenger vehicles into a single constrained-optimal-control-based system. This framework allows for multiple actuation modes, diverse trajectory-planning objectives, and varying levels of autonomy. The vehicle navigation problem is formulated as a constrained optimal control problem with constraints bounding a navigable region of the road surface. A model predictive controller iteratively plans the best-case vehicle trajectory through this constrained corridor. The framework then uses this trajectory to assess the threat posed to the vehicle and intervenes in proportion to this threat. This approach minimizes controller intervention while ensuring that the vehicle does not depart from a navigable corridor of travel. Simulated results are presented here to demonstrate the framework's ability to incorporate multiple threat thresholds and configurable intervention laws while sharing control with a human driver. ©2009 IEEE.
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| 2. |
- Anderson, S. J., et al.
(author)
-
Constraint-based planning and control for safe, semi-autonomous operation of vehicles
- 2012
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In: 2012 IEEE intelligent vehicles symposium. - 9781467321181 ; , s. 383-388
-
Conference paper (peer-reviewed)abstract
- This paper presents a new approach to semi-autonomous vehicle hazard avoidance and stability control, based on the design and selective enforcement of constraints. This differs from traditional approaches that rely on the planning and tracking of paths. This emphasis on constraints facilitates "minimally-invasive" control for human-machine systems; instead of forcing a human operator to follow an automation-determined path, the constraint-based approach identifies safe homotopies, and allows the operator to navigate freely within them, introducing control action only as necessary to ensure that the vehicle does not violate safety constraints. The method evaluates candidate homotopies based on "restrictiveness", rather than traditional measures of path goodness, and designs and enforces requisite constraints on the human's control commands to ensure that the vehicle never leaves the controllable subset of a desired homotopy. Identification of these homotopic classes in off-road environments is performed using geometric constructs. The goodness of competing homotopies and their associated constraints is then characterized using geometric heuristics. Finally, input limits satisfying homotopy and vehicle dynamic constraints are enforced using threat-based feedback mechanisms to ensure that the vehicle avoids collisions and instability while preserving the human operator's situational awareness and mental models. The methods developed in this work are shown in simulation and experimentally demonstrated in safe, high-speed teleoperation of an unmanned ground vehicle. © 2012 IEEE.
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| 3. |
- Anderson, Sterling J., et al.
(author)
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Constraint-based semi-autonomy for unmanned ground vehicles using local sensing
- 2012
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In: UNMANNED SYSTEMS TECHNOLOGY XIV. - Bellingham, WA : SPIE - International Society for Optical Engineering. - 9780819490650 ; , s. Article no. 83870K-
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Conference paper (peer-reviewed)abstract
- Teleoperated vehicles are playing an increasingly important role in a variety of military functions. While advantageous in many respects over their manned counterparts, these vehicles also pose unique challenges when it comes to safely avoiding obstacles. Not only must operators cope with difficulties inherent to the manned driving task, but they must also perform many of the same functions with a restricted field of view, limited depth perception, potentially disorienting camera viewpoints, and significant time delays. In this work, a constraint-based method for enhancing operator performance by seamlessly coordinating human and controller commands is presented. This method uses onboard LIDAR sensing to identify environmental hazards, designs a collision-free path homotopy traversing that environment, and coordinates the control commands of a driver and an onboard controller to ensure that the vehicle trajectory remains within a safe homotopy. This system's performance is demonstrated via off-road teleoperation of a Kawasaki Mule in an open field among obstacles. In these tests, the system safely avoids collisions and maintains vehicle stability even in the presence of "routine" operator error, loss of operator attention, and complete loss of communications.
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| 4. |
- Anderson, Sterling J., et al.
(author)
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Design and Development of an Optimal-Control-Based Framework for Trajectory Planning, Threat Assessment, and Semi-autonomous Control of Passenger Vehicles in Hazard Avoidance Scenarios
- 2011
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In: Robotics Research. - Berlin : Springer Berlin/Heidelberg. - 9783642194566 ; , s. 39-54
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Conference paper (peer-reviewed)abstract
- This paper describes the design of an optimal-control-based active safety framework that performs trajectory planning, threat assessment, and semi-autonomous control of passenger vehicles in hazard avoidance scenarios. This framework allows for multiple actuation modes, diverse trajectory-planning objectives, and varying levels of autonomy. A model predictive controller iteratively plans a best-case vehicle trajectory through a navigable corridor as a constrained optimal control problem. The framework then uses this trajectory to assess the threat posed to the vehicle and intervenes in proportion to this threat. This approach minimizes controller intervention while ensuring that the vehicle does not depart from a navigable corridor of travel. Simulation and experimental results are presented here to demonstrate the framework's ability to incorporate configurable intervention laws while sharing control with a human driver. © 2011 Springer-Verlag.
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| 5. |
- Anderson, Sterling J., et al.
(author)
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Experimental Study of an Optimal-Control-Based Framework for Trajectory Planning, Threat Assessment, and Semi-Autonomous Control of Passenger Vehicles in Hazard Avoidance Scenarios
- 2010
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In: FIELD AND SERVICE ROBOTICS. - Berlin : Springer Berlin/Heidelberg. - 9783642134074 ; , s. 59-68
-
Conference paper (peer-reviewed)abstract
- This paper describes the design of an optimal-control-based active safety framework that performs trajectory planning, threat assessment, and semi-autonomous control of passenger vehicles in hazard avoidance scenarios. The vehicle navigation problem is formulated as a constrained optimal control problem with constraints bounding a navigable region of the road surface. A model predictive controller iteratively plans an optimal vehicle trajectory through the constrained corridor. Metrics from this "best-case" scenario establish the minimum threat posed to the vehicle given its current state. Based on this threat assessment, the level of controller intervention required to prevent departure from the navigable corridor is calculated and driver/controller inputs are scaled accordingly. This approach minimizes controller intervention while ensuring that the vehicle does not depart from a navigable corridor of travel. It also allows for multiple actuation modes, diverse trajectory-planning objectives, and varying levels of autonomy. Experimental results are presented here to demonstrate the framework's semi-autonomous performance in hazard avoidance scenarios.
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| 6. |
- Anderson, Sterling J., et al.
(author)
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The intelligent copilot : A constraint-based approach to shared-adaptive control of ground vehicles
- 2013
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In: IEEE Intelligent Transportation Systems Magazine. - Piscataway, NJ : IEEE Press. - 1939-1390. ; 5:2, s. 45-54
-
Journal article (peer-reviewed)abstract
- This work presents a new approach to semi-autonomous vehicle hazard avoidance and stability control, based on the design and selective enforcement of constraints. This differs from traditional approaches that rely on the planning and tracking of paths and facilitates minimally-invasive control for human-machine systems. Instead of forcing a human operator to follow an automation-determined path, the constraint-based approach identifies safe homotopies, and allows the operator to navigate freely within them, introducing control action only as necessary to ensure that the vehicle does not violate safety constraints. This method evaluates candidate homotopies based on restrictiveness rather than traditional measures of path goodness, and designs and enforces requisite constraints on the human's control commands to ensure that the vehicle never leaves the controllable subset of a desired homotopy. This paper demonstrates the approach in simulation and characterizes its effect on human teleoperation of unmanned ground vehicles via a 20-user, 600-trial study on an outdoor obstacle course. Aggregated across all drivers and experiments, the constraintbased control system required an average of 43% of the available control authority to reduce collision frequency by 78% relative to traditional teleoperation, increase average speed by 26%, and moderate operator steering commands by 34%. © 2009-2012 IEEE
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| 7. |
- Anderson, S., et al.
(author)
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Semi-autonomous Avoidance of Moving Hazards for Passenger Vehicles
- 2010
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In: Proceedings of the ASME Dynamic Systems and Control Conference--2010. - New York : ASME Press. - 9780791844175 ; , s. 141-148
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Conference paper (peer-reviewed)abstract
- This paper presents a method for semi-autonomous hazard avoidance in the presence of unknown moving obstacles and unpredictable driver inputs. This method iteratively predicts the motion and anticipated intersection of the host vehicle with both static and dynamic hazards and excludes projected collision states from a traversable corridor. A model predictive controller iteratively replans a stability-optimal trajectory through the navigable region of the environment while a threat assessor and semi-autonomous control law modulate driver and controller inputs to maintain stability, preserve controllability, and ensure safe hazard avoidance. The efficacy of this approach is demonstrated through both simulated and experimental results using a semi-autonomously controlled Jaguar S-Type. Copyright © 2010 by ASME.
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| 8. |
- Anderson, S., et al.
(author)
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Semi-Autonomous Stability Control and Hazard Avoidance for Manned and Unmanned Ground Vehicles
- 2010
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In: Proceedings of the 27th Army Science Conference. ; , s. 1-8
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Conference paper (peer-reviewed)abstract
- This paper presents a method for trajectory planning, threatassessment, and semi-autonomous control of manned andunmanned ground vehicles. A model predictive controlleriteratively replans a stability-optimal trajectory through the saferegion of the environment while a threat assessor and semi-autonomous control law modulate driver and controller inputs tomaintain stability, preserve controllability, and ensure that thevehicle avoids obstacles and hazardous areas. The efficacy of thisapproach in avoiding hazards while accounting for various typesof human error, including errors caused by time delays, isdemonstrated in simulation.
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| 9. |
- Arndt, David, et al.
(author)
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Two-Wheel Self-Balancing of a Four-Wheeled Vehicle
- 2011
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In: IEEE Control Systems Magazine. - Piscataway, N.J. : IEEE Press. - 1066-033X. ; 31:2, s. 29-37
-
Journal article (peer-reviewed)abstract
- Cars and trucks are susceptible to accidents due to rollover. In the United States in 2005, 21.1 of a total of 54,718 deaths in vehicle crashes were caused by rollover [1]. Significant research has therefore been devoted to detecting and preventing rollover through active control. Numerous approaches attempt to detect or predict wheel liftoff using onboard sensing and a combination of automatic steering and braking to keep the wheels on the ground [2][4]. © 2006 IEEE.
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| 10. |
- Arvidson, R. E., et al.
(author)
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Opportunity Mars Rover mission : Overview and selected results from Purgatory ripple to traverses to Endeavour crater
- 2011
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In: Journal of Geophysical Research. - Hoboken : Wiley-Blackwell. - 0148-0227 .- 2156-2202. ; 116, s. E00F15-
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Journal article (peer-reviewed)abstract
- Opportunity has been traversing the Meridiani plains since 25 January 2004 (sol 1), acquiring numerous observations of the atmosphere, soils, and rocks. This paper provides an overview of key discoveries between sols 511 and 2300, complementing earlier papers covering results from the initial phases of the mission. Key new results include (1) atmospheric argon measurements that demonstrate the importance of atmospheric transport to and from the winter carbon dioxide polar ice caps; (2) observations showing that aeolian ripples covering the plains were generated by easterly winds during an epoch with enhanced Hadley cell circulation; (3) the discovery and characterization of cobbles and boulders that include iron and stony-iron meteorites and Martian impact ejecta; (4) measurements of wall rock strata within Erebus and Victoria craters that provide compelling evidence of formation by aeolian sand deposition, with local reworking within ephemeral lakes; (5) determination that the stratigraphy exposed in the walls of Victoria and Endurance craters show an enrichment of chlorine and depletion of magnesium and sulfur with increasing depth. This result implies that regional-scale aqueous alteration took place before formation of these craters. Most recently, Opportunity has been traversing toward the ancient Endeavour crater. Orbital data show that clay minerals are exposed on its rim. Hydrated sulfate minerals are exposed in plains rocks adjacent to the rim, unlike the surfaces of plains outcrops observed thus far by Opportunity. With continued mechanical health, Opportunity will reach terrains on and around Endeavour's rim that will be markedly different from anything examined to date. Copyright 2011 by the American Geophysical Union.
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