Scansorial Landing and Perching

Transcription

1 Scansorial Landing and Perching Alexis Lussier-Desbiens, Alan Asbeck and Mark R. Cutkosky ISRR 2009, Aug 31 - Sep 3, Lucerne CH Biomimetics and Dextrous Manipulation Laboratory Stanford University 1

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3 Advantages of Perching Greatly extend mission time Stable vantage point while perched Possibility of landing and physically interacting with a surface. Perching combines the best of climbing and flying: Agile and fast while flying Can cover long distances Low energy consumption while perched Wait for better weather conditions Quiet (no motor noise) RiSE platform climbing library at SwRI, San Antonio, TX 3 3

4 Why vertical surfaces? Common in urban environments Easy to detect Often provide a large surface to simplify landing After an explosion, earthquake, etc. walls may be comparatively safe, clean and uncluttered 4 4

5 Related Work On agile flight: How et al. (MIT) on indoor flying and hovering Oh et al. (Drexel) on autonomous hovering On perching aerodynamics & control: Wickenheiser et al. (Cornell) on vehicle morphing for perching Tedrake et al. (MIT) on controllability of fixedwing plane for perching on a wire Hybrid aerial/terrestrial vehicle (Quinn) No detailed consideration of the landing system Slow maneuvers sensitive to disturbances Use of highly accurate motion capture system/sensors to enable control [Wickenheiser, 2007] [Cory & Tedrake, 2008] [Green & Oh, 2006] 5 5

6 Approach: Conventional plane Quick maneuver to minimize disturbance effects Focus on suspension and spines to simplify sensing and control Everything onboard Sonar Paparazzi Autopilot & sensors Modified Flatana Airplane Spines Suspension 4) Touchdown 2) Wall detection 1) Approach 3) Pitch up 5) Rest Elevator 6 6

7 Perching Strategy 1. Fly toward wall ~ 9 m/s 2. Detect wall with ultrasonic sensor 20 Hz, 6 m range 3. Pitch up to slow down (takes about 2-3m) 4. Touchdown possible for about 1.5 m before impact 5. Touchdown at 1-3 m/s. Let suspension absorb impact Simulated trajectory of the perching maneuver 0!0.2 y (m)!0.4!0.6!0.8 Waiting for wall detection Pitching up Successful landing!6!5!4!3!2!1 0 x (m) (inspired by [Cory & Tedrake 2008]) 7 7

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9 Clinging with spines Why spines? require no power work on a range of outdoor surfaces relatively unaffected by films of dirt and moisture leave no trace of their passage provide many loading cycles Used on Spinybot and RiSE to climb brick, stucco, concrete rock... Spine mechanisms take advantage of robot's control over foot trajectories and forces. With UAVs, the challenge is to provide desired trajectory and forces using momentum of the plane. 9 9

10 Spine suspensions Small spines (10-15 µm tip radius) catch and hang on asperities Individual spine suspensions distribute the load Loading trajectory required 2. Pull down 1. Normal force Approach volume 3. Pull away Loading cycle x y 2 Loading Forces Volume 10 10

11 Spine/surface interaction mg 11 11

12 Spine limit curve -- 1 foot, 10 spines (for roofing paper -- similar to stucco or composite roof shingles) "! "%! &'()*($+,-(.(* 5/63,738($+ :$'./0,&$')3,9:;!"!#% & +$'./0 %& 123/',,,,,-(.(* &./4 -(.(* #! $!#" " "! #" #! $" 523/',&$')3,9:; &" $ mg 12 12

13 Revisit spine constraints, from standpoint of the plane F n overload limits friction limit safe region F tan pull-in Limit on Fn/Ftan gravity 13 13

14 Spine constraints, from the standpoint of the plane F max F pull-in F 0 F static mg 14 14

15 Fn Fmax # " The actual picture is a # bit messier... Loading trajectory is important Low damping ratio: Ratio Fn/Ftan too high 5*+67,*8-.',/*6 measured (9374+:9'; Rebound simulated High damping ratio: High peak force 1',3+4-.',/*-012 2!!2! % $!4!6 "& ' Fstatic 20 ' "!2! 2 " # $ %! 12 %" %# ()*+,-.',/*-012 Ftan 15 15

16 Leg suspension requirements Early tests revealed that vertical rebound was the main failure Solution: design suspension (links, springs, dampers, nonlinear elements) to absorb kinetic energy and direct forces toward spines with: moderate peak landing force moderate suspension travel (no knee contact) no negative tangential forces (vertical rebound, detachment) small negative normal forces (no horizontal bounce-off) 16 16

17 Suspension model!! (dynamic equations via Autolev; simulations in Matlab) "" * "! /!!!" #$ %&' +'&)* #$!! 75 8)9-* +'&)* Toe suspension (new) ()$#(! ()** 6,34 %&' +,!6) 3" +- Pseudo-elastic link model accounts for bending. 6. /01"!26) ()** 3!,!&-.*/!&-01231/4*1-*5 #$%&'$ ()$#(" Hip damping is large and nonlinear 17 17

18 Leg Structure Attachment points Foam hip Foam ankle Spines Carbon tibia Balsa/Carbon femur Sorbothane knee 18 18

19 Nonlinear elements Stiffness (Nm/deg) Hip stiffness versus hip angle (damping follows similar trend)! Fit Data Hip angle (deg) Material properties + kinematics to create roughly constant force Damping scaled w.r.t position and velocity Urethane foam exhibits reduced damping at high velocity 19 19

20 Comparing model & force plate data 56/7809:83/01;4 $! #' #! '! =:?/<0A-,60=/72"0B787."! "!5!!"#!"$!"%!"& spine!"' dragging!"(!") effects!"*!"+,-./012/34 # ;:8.7<09:83/01;4 #! '!!5 $ =/72>8/?09:83/201%08>@24 =:?/<0A-,60=/72"0B787."!!"#!"$!"%!"&!"'!"(!")!"*!"+,-./012/

21 Elevator up Touchdown possible 9 m/s Wall detection Pitch up maneuver 2 m/s y x 30/40 successful landings (10 autonomous, 20 in manual control) Pitch = 65 to 110 deg Pitch rate = 0 to 200 deg/s vx = m/s (forward) vy = up to 1 m/s (downward) 21 21

22 Improvements and future work Land on other surfaces (horizontal, inverted) > use opposed spines Real conditions (windy, etc.) Maneuver on the wall (hybrid scansorial robotics) Take off from the wall! -(./0 12(()0 '() 140 F 32 F *(+, 34) 567 *+489 5:6)7 ;"<=4= C8DE"+(8, *.6649)">8?8@:+:):4=A B+8994,">8?8@:+:):4=A!""#""$"""%""""!&""""!&&"""!&&&!""#""$"""%""""!&""""""#&"""""""$& F+@=EG 22 22

23 Improvements and future work 23 23

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25 Limits for directional adhesion (e.g. Stickybot) ) k l a t Fs / N N m ( e pulloff c r limits o F µ m 600 µ m 700 µ m l a m r o N Tangential Force (mn/stalk) F tan 25 25

26 Spine limit curve -- 1 foot, 10 spines (for roofing paper -- similar to stucco or composite roof shingles) "! "%! &'()*($+,-(.(* 5/63,738($+ :$'./0,&$')3,9:;!"!#% & +$'./0 %& 123/',,,,,-(.(* &./4 -(.(* #! $!#" " "! #" #! $" 523/',&$')3,9:; &" $ mg 26 26

27 Onboard Sensors Simple wall detection using the LV-Maxsonar: Range of 6 m Update rate of 20 Hz Onboard accelerometer and gyro are used for data analysis Combined using a second order complementary filter: ( ) τs +1 2 θ(s) = τs +1 τ 2 s 2τs +1 θ(s)+ (τs + 1) 2 (τs + 1) 2 θ(s) Need something better!!! Pitch (deg) !20 Different techniques for measuring pitch Drifting Complementary Filter Rate Gyro Integration Gravity measurement Sensitive to vibrations time (sec) 27 27

28 !!!& Aero Model (inspired by [Cory & Tedrake 2008]) +,(-.%" " C L = 2 sin(α) cos(α)! "& "! #$% '( )!' C D = 2 sin 2 (α) ), )*!") "- L = 1 2 ρv2 AC L #2 D = 1 2 ρv2 AC D )- "!#$%!,