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CS 326A: Motion Planning. Jean-Claude Latombe CA: Aditya Mandayam. Motion planning is the ability for an agent to compute its own motions in order to achieve certain goals. All autonomous robots and digital actors should eventually have this ability. Piano Mover’s Problem. Sense. Plan.
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CS 326A: Motion Planning Jean-Claude Latombe CA: Aditya Mandayam
Motion planning is the ability for an agent to compute its own motions in order to achieve certain goals. All autonomous robots and digital actors should eventually have this ability
Sense Plan Move
Goal ARL Robot
Sense Plan Move Motion library Learn
Goal of Motion Planning • Compute motion strategies, e.g.: • geometric paths • time-parameterized trajectories • sequence of sensor-based motion commands • To achieve high-level goals,e.g.: • go to A without colliding with obstacles • assemble product P • build map of environment E • find object O
Fundamental Question Are two given points connected by a path? Valid region Forbidden region
E.g.: ▪Collision with obstacle ▪Lack of visibility of an object ▪Lack of stability Fundamental Question Are two given points connected by a path? Valid region Forbidden region
Basic Problem • Statement:Compute a collision-free path for a rigid or articulated object among static obstacles • Inputs: • Geometry of moving object and obstacles • Kinematics of moving object (degrees of freedom) • Initial and goal configurations (placements) • Output: Continuous sequence of collision-free robot configurations connecting the initial and goal configurations
Tool: Configuration Space • Problems: • Geometric complexity • Space dimensionality
Sampling-based Criticality-based Continuous space C-space Discretization Search
Moving obstacles Multiple robots Movable objects Assembly planning Goal is to acquire information by sensing Model building Object finding/tracking Inspection Nonholonomic constraints Dynamic constraints Stability constraints Optimal planning Uncertainty in model, control and sensing Exploiting task mechanics (sensorless motions, under-actualted systems) Physical models and deformable objects Integration of planning and control Integration with higher-level planning Extensions of Basic Problem
Humanoid Robots HRP-2, AIST, Japan
Climbing Robot http://www.youtube.com/watch?v=biSx-aKN690
Manipulation of Deformable Objects Topologically defined goal
Digital Characters Toy Story (Pixar/Disney) Antz (Dreamworks) A Bug’s Life (Pixar/Disney) Tomb Raider 3 (Eidos Interactive) The Legend of Zelda (Nintendo) Final Fantasy VIII (SquareOne)
Map Building Where to move next?
Radiosurgical Planning CyberKnife (Accuray)
24-inch turning radius 9-inch turning radius Building Code Verification
Primary escape route Potential congesting areas Secondary escape route Egress Simulation
Transportation of A380 Fuselage through Small Villages Kineo
Study of Motion of Bio-Molecules Inhibitor binding to HIV protease
Goals of CS326A • Present a coherent framework for motion planning problems • Emphasis of “practical” algorithms with some guarantees of performance over “theoretical” or purely “heuristic” algorithms
General Framework Continuous representation (configuration space and related spaces + constraints) Discretization (probabilistic sampling, criticality-based decomposition) Graph searching (blind, best-first, A*)
Practical Algorithms (1/2) • A complete motion planner always returns a solution plan when one exists and indicates that no such plan exists otherwise. • Most motion planning problems are hard, meaning that complete planners take exponential time in # of degrees of freedom, objects, etc.
Practical Algorithms (2/2) • Theoretical algorithms strive for completeness and minimal worst-case complexity. Difficult to implement and not robust. • Heuristic algorithms strive for efficiency in commonly encountered situations. Usually no performance guarantee. • Weaker completeness Simplifying assumptions Exponential algorithms that work in practice