Trajectory Segmentation for the Autonomous Control of Backward Motion for Truck and Trailer. Dieter Zöbel

Transcription

1 Trajectory Segmentation for the Autonomous Control of Backward Motion for Truck and Trailer Dieter Zöbel Universität Koblenz-Landau Fachbereich Informatik, Institut für Softwaretechnik Arbeitsgruppe Echtzeitsysteme

2 CONTENTS 1 Introduction 1 2 Trajectories for maneuvers 6 3 Extreme curves of the moving vehicle 12 4 Cover segments for extreme curves 15 5 Safe cover segments and corridors 18 6 Outlook 26 ii

3 1 Introduction University Koblenz-Landau, Germany Department of Computer Science Institute for Software Engineering Working Group Real-Time Systems Dieter Zöbel Elisabeth Balcerak David Polock Students Topics in research and education: Scheduling of real-time processes without resource constraints Validation of real-time contraints in operating systems Special course of studies: Mobile Systems autonomous safe auto-mobile Dieter Zöbel ITSC

4 Application area: Automation in logistics non automotive: management and administrative support for transport, exchange of goods and controlling internet based activities such as electronic contracts and billing mobile applications: guidance of trucks or the tracking of goods automotive: automatic guided vehicles (AGV) for storage automation tracking the road detection of traffic signs autonomous driving electronic shaft maneuvering of truck and trailer Dieter Zöbel ITSC

5 Scenario of application: Autonomous driving on a yard of a forwarding agency preconditions: restriction to the non-public traffic high precision in driving and brisk motions of the vehicle compliance of defined safety criterions expectations: saving of personnal costs permanent disposability of any vehicle on the yard the possibility for coherent integration of the vehicle s maneuvers into the workflow of a forwarding agency Dieter Zöbel ITSC

6 Motion planning for (ideal) articulated vehicles Given a yard without any obstacles and boundaries computation of a feasible trajectory control algorithm to make the vehicle follow the trajectory Basis: bike-model Dieter Zöbel ITSC

7 Motion planning for (real) articulated vehicles Safety criteria for the yard of a logistics center: Computation of a corridor that will never be left by the vehicle in motion. Constraints: trajectory inside the corridor modeling of obstacles (fixed and moving) formalization for the shape of a vehicle in motion estimation of deviations from the trajectory algorithms for path planning and motion control Measures to be taken: Definition of adequate geometric objects (segments) for path planning motion control Dieter Zöbel ITSC

8 2 Trajectories for maneuvers Intention: Canonical construction of trajectories motion planning based on polygons execution of standardized maneuvers 2500mm 2000mm 1500mm 1000mm 500mm 0mm 500mm 1000mm 1500mm 0mm Dieter Zöbel ITSC

9 Maneuver phases 1-2 inclination of truck and trailer 2-3 truck and trailer on a circular line 3-4 getting truck and trailer into a straight line Constraints: existance of a fixed relation between steering angle α circ and the inclination γ circ between truck and trailer for driving on a circular line maximal steering angle α max steering angle α circ between truck and trailer somewhere between 0 and α max Dieter Zöbel ITSC

10 Kinematic model Bike model: zl Settings: x-andy-position of the axle of the trailer rzl lza lzk aa.x(u, v) = rzk cos(u)+laa cos(u v) α rza rzk η za zk aa.y(u, v) = rzk sin(u)+laa sin(u v) u raa laa v direction of motion of the axle of the trailer aa γ δ(aa.y) δ(aa.x) = tan(u v) Dieter Zöbel ITSC

11 2500mm 2000mm 1500mm 1000mm 500mm 0mm 0mm 500mm 1000mm 1500mm EZauto The curves of the trailer for all maneuver phases Dieter Zöbel ITSC

12 The motion of truck and trailer for the maneuver phases 2500mm 2000mm 1500mm 1000mm 500mm 0mm 500mm 1000mm 1500mm 0mm Dieter Zöbel ITSC

13 Inclination γ as a function of the covered distance d α max γ Distance d corresponds to the curve covered by the axle of the trailer. This curve consists of different circular lines for the different maneuver phases. Computation of distance d: α circ α -20 α max -30 γ for inclination: α circ = α max 30 γ d d 1 2 = u(v 2 ) u(v 1 ) rzk d 2 3 = φ 2 3 rzk d d 3 4 = u(v 3 ) u(v 4 ) rzk α -20 circ -α max -30 γ for inclination: α circ = 25 Dieter Zöbel ITSC

14 3 Extreme curves of the moving vehicle From the bike model to the extent of a real vehicle A vehicle is described by a rectangle. The shape(t) is the perpendicular shadow of such a vehicle at time t. A vehicle in motion covers a certain space during a time interval. (x, y) cover(t 1,t 2 ) t, t 1 t t 2, (x, y) shape(t) Anomaly: the curvature of the wheels of a vehicle is not necessarily equal to the curvature of any point of its shape Dieter Zöbel ITSC

15 Extreme points of the articulated vehicle Six extreme points of a vehicle dominate its cover. zvr zvl zar zhr avl aal ahl avr aar ahr zal zhl Relevant extreme points for truck and trailer Dieter Zöbel ITSC

16 Extreme curves of the articulated vehicle Twelve extreme curves determine the cover of the articulated vehicle throughout the maneuver 3000mm 2500mm 2000mm 1500mm 1000mm 500mm 0mm 0mm 500mm 1000mm 1500mm Dieter Zöbel ITSC

17 4 Cover segments for extreme curves Context: description of the movement of the articulated vehicle by simple geometric forms: segments simple and efficient algorithms for path finding algorithms uniqueness in associating a vehicle to a segment for an instant of time Idea: rectangle for straight movements section of rings for circular movements (with center equal to the center c 23 of phase 2-3) Dieter Zöbel ITSC

18 Decision table for computing the section of a ring The radius of the ring is determined by rc min and rc max vehicle phase rc min rc max truck 1-2 construction final points 2-3 zar zvl or zhl 3-4 final points final points trailer 1-2 construction construction 2-3 aar avl or ahl 3-4 right aar construction 3-4 left aar final points Table for the change of direction by +45 Dieter Zöbel ITSC

19 3000mm 2500mm 2000mm 1500mm 1000mm 500mm 0mm 0mm 500mm 1000mm 1500mm EZauto Cover segment for a maneuver All extreme curves of a maneuver are covered by a section of a ring Dieter Zöbel ITSC

20 5 Safe cover segments and corridors A (real) vehicle in motion constitutes a typical real-time object with all the deficiencies regarding timeliness and precision. Considerable deficiencies by: in the precision of the perceived input data, e.g. angle γ in the precision of the perceived output data, e.g. steering angle α deficiencies due to the aging of input and output data deficiencies by the control algorithm Objective: Estimation of the possible cover of the articulated vehicle Dieter Zöbel ITSC

21 The real vehicle: a model truck EZauto Solid model at a scale of 1 : 16 with position and direction detection by triangulation Dieter Zöbel ITSC

22 Results with the model truck Precision of the trailer at the ramp: ±10mm bzw. ± Sollweg Anhaengerachse Vorderachse Dieter Zöbel ITSC

23 Strategies for safety Safety criteria: Truck and trailer do not leave the safe corridor at any time the (real) articulated vehicle is associated to exactly one safe cover segment at certain instances of time the (real) articulated vehicle passes from one safe cover segment to the next one Srategies: avoidance by estimation of the deviation due to control and data deficiencies detection by forecasting that the predefined space is left eventually The latter one operates with emergency halts and is less pessimistic with respect to the extent of predefined space for maneuvering. Dieter Zöbel ITSC

24 Computation of safe cover segments and safe corridors Steps in deriving the cover for articulated vehicles in motion: 1. derivation of the set of curves produced by the extreme points of the truck and trailer 2. covering of the curves by a simple geometric object: the segment (in terms of a rectangle or a part of a ring) 3. enlargement of the segment considering all kinds of deficiencies to a safe segment 4. application of a construction principle based on contact points to form a safe corridor by subsequent safe segments Invariant: At one instant of time there is exactly one safe segment that is to associated to a vehicle in motion covering its movements up to some eventual emergency halt. Dieter Zöbel ITSC

25 Timeliness for the detection strategy The control algorithm ca is executed every time period t mc. At time t ca algorithm ca operates on input data with an age up to t p An emergency halt is thrown by control algorithm ca at time t ca if the articulated vehicle is in danger to leave the the safe corridor up to time t ca + t mc + t h cycle i bound c k + c k - bound C k (t ca ) SI i t p t mc t h t ca Dieter Zöbel ITSC

26 Construction of safe segments EZauto 2500mm 2000mm 1500mm 1000mm 500mm 0mm 0mm 500mm 1000mm The extension of a cover segment to a safe cover segment is determined by the estimation of all sources of deficiencies over the interval t p + t mc + t h. Dieter Zöbel ITSC

27 2500mm 2000mm 1500mm 1000mm 500mm 0mm 0mm 500mm 1000mm EZauto Construction of safe corridors Dieter Zöbel ITSC

28 6 Outlook result: concept of safety for known (fixed or mobile) obstacles immediate questions: effective path planning based upon save cover segments solving the tradeoff between the size of cover segments and the frequency of emergency halts spin offs: a simulator for learner drivers in maneuvering articulated vehicles driving assistance e.g. for parking a car with caravans further research and development: cooperation and coordination of several articulated vehicles by dynamic acquisition of save cover segments integration of redundant sensors the two-axle-trailer Dieter Zöbel ITSC