Experimental Validation of Stable Obstacle Climbing with a Four-Wheel Mobile Robot OpenWHEEL i3R 4W Stable Climbing [email protected] [email protected] [email protected] Clermont-Ferrand, France

LaMI

UBP

IFMA

TIMS

Mechanical Engineering Research Group

Blaise Pascal University

French Institute for Advanced Mechanics

Research Federation

Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

1

Introduction More agile mobile robots needed in the future 4W Stable Climbing

Spatial exploration Mars exploration robot A rover for sample analysis www.nasa.gov/centers/jpl

Introduction Agile robots Locomotion

Challenging usual applications

Exp. settings Experiment Conclusion

Wheeled ATVs are blocked on ground discontinuities Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

Wheelchair blocked before an obstacle

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

2

Introduction One big machine ✔

4W Stable Climbing

Agriculture

A fleet of agile robots ✔

Rescue

Fleet of robots to avoid soil compaction

Introduction Agile robots Locomotion

Earthquake Mag. 7.4 Turkey (1999) Scanning the streets and buildings

Exp. settings Experiment

✔

Beach cleaning uses big machines or manual cleaning

Conclusion

Beach pollution Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

Towed filtering machine

Manual cleaning

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

3

Introduction This work is about: ✔

4W Stable Climbing Introduction Agile robots Locomotion Exp. settings Experiment Conclusion

✔ ✔ ✔

Wheeled robots That climb step obstacles With only four wheels And stable behaviour

Within the OpenWHEEL framework Wireless connection A3 Rear

S 32

Control

S 31 Wheel W31

A2

I2

S 21

W21

Double wishbone

W22

Innovative suspension

S 11

W11

S 12

A1 Control

I1

W12

Camera

S22

Control

Suspension mechanism Saw Swing arm

Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

CAN Bus

W 32

n Fro

t Z X Y

Inter-axle mechanism Ia Serial Parallel Innovative mechanism mechanism mechanism

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

4

Agile mobile robots Terrestrial locomotion system ✔ ✔

4W Stable Climbing

✔

- unilateral / bilateral - slipping / sticking - can change in nature and number

Terrestrial vehicles & robots ✔

Introduction

Poly-articulated mechanical system Interact with environment Contacts with the ground

✔ ✔

Wheeled vehicles prevail (energetic efficiency ?) Blocked on slope discontinuities of the ground Legs / Tracks regain interest for climbing

Agile robots

Interface with the ground

Locomotion

✔

Crawler

+ multiples contacts, can cross obstacles & rough terrain - require high energy, moderate speed, complex control

Experiment

✔

Leg

+ can cross obstacles and go fast on rough terrain - contact discontinuity, energy cost, stability control

Conclusion

✔

Wheel

+ fast on smooth surface, energy efficient - cannot climb obstacles or run on rough terrain

✔

Track

+ permanent stability, high traction - high friction energy loss, particularly during steering

Exp. settings

Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

5

Mobile robots based on legs ✔ ✔ ✔

Bi / Quadri / Hexa / Octo Natural gait / self-teaching Legs with feet = wheels

4W Stable Climbing Yanboo III (13kg,0.7m high) Biped with suction/rolling effectors Legs are manipulators www-robot.mes.titech.ac.jp

Introduction Agile robots ●

Leg

●

Wheel

●

Hybrid

Locomotion Exp. settings Experiment Conclusion

Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

Big Dog (75kg, 1m long, 6km/h, 35° slopes, 150kg payload) www.bostondynamics.com

Roller-Walker (24kg, 0.5m long) Convertible wheels / Dual locomotion mode: walking / roller-skating www-robot.mes.titech.ac.jp

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

6

Wheeled robots ✔ ✔

Wheel: energy efficient even when steering Only exception : skid steering

4W Stable Climbing Introduction Agile robots ●

Leg

●

Wheel

●

Hybrid

Locomotion Exp. settings Experiment Conclusion

Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

Pioneer P3-AT Skid steering simple robot www.mobilerobots.com

Nomad Dual Ackermann steering strategy www.frc.ri.cmu.edu/projects/lorax

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

7

Adaptative Wheeled Robots ✔ ✔

Minimally actuated frame, energy efficiency Simple control

4W Stable Climbing Introduction Agile robots ●

Leg

●

Wheel

●

Hybrid

Locomotion

Micro5 Climbing abilities via 5 wheels www.mit.edu/~ykuroda

Rocky 7 Adaptative rocker-bogie structure www-robotics.jpl.nasa.gov

Exp. settings Experiment Conclusion

Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

8

Adaptative Wheeled Robots Crab I Adaptative parallel bogies Obstacle climbing abilities www.asl.ethz.ch

4W Stable Climbing Introduction Agile robots ●

Leg

●

Wheel

●

Hybrid

Shrimp 6 wheels on 2 // bogies and 1 front linkage www.asl.ethz.ch

Locomotion Exp. settings Experiment Conclusion

Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

9

Hybrid multi-mode robots ✔ ✔

4W Stable Climbing

Highly actuated frame Orientable tracks for special modes of displacement

Introduction Agile robots ●

Leg

●

Wheel

●

Hybrid

Locomotion Exp. settings Experiment

Azimut 4 orientable tracks www.gel.usherbrooke.ca/laborius

Conclusion

Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

Helios VII 2 articulated tracks + 1 manipulating arm with hybrid grip/wheel end effector www-robot.mes.titech.ac.jp

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

10

Hybrid multi-mode robots ✔ ✔

4W Stable Climbing Introduction Agile robots ●

Leg

●

Wheel

●

Hybrid

Highly actuated frame Displacement modes: peristaltic crossing, obstacle climbing

RobuROC 6 (150 kg, 1.5m long) 3 tiltable axles with passive warping Able to turn on itself Can climb obstacles www.robosoft.fr

Locomotion Exp. settings

Hylos (0.5m long) 4 wheels on 3DOF legs www.robot.jussieu.fr Lama Peristaltic crossing of sandy areas www.laas.fr

Experiment Conclusion

Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

11

Chosen locomotion modes for OpenWHEEL Chosen architecture 4W Stable Climbing Introduction Agile robots Locomotion

✔ ✔

✔ ✔

OpenWHEEL

●

OW i3R

✔

●

Stability

✔

Experiment Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

Rolling Climbing step obstacles

Multi-modes

Only four wheels ✔

Climbing

Exp. settings

Hybrid robot

Two locomotion modes (at least)

●

●

Wheels (efficiency) On legs (climbing ability)

No existing robot that climb with only four wheels A challenge for stability during climbing Easier to transfer on real vehicles

Few actuators ✔ ✔

Actuated wheels Few actuators in legs/frame for better simplicity / stiffness / consumption / price MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

12

OpenWHEEL i3R i3R = 3R inter-axle mechanism ✔ ✔

4W Stable Climbing Introduction

2 passive R joints in the middle of the axles 1 actuated R joint for central warping

Kinematic structure with double symmetry OpenWHEEL i3R A big central actuator for warping

Passive joint Axle steering without robot motion

Agile robots Locomotion ●

OpenWHEEL

●

OW i3R

●

Stability

●

Climbing

ar e R

Exp. settings Experiment Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

W21

W22

nt o r F

W11

W12 Four actuated wheels More space for payload

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

13

Stability criterion on 3 wheels 2D modelling when lifting one wheel

Introduction Agile robots

Wheel W12 (front-left)

Wheel W21 (rear-right)

1)

2)

3)

Front axle steering

4W Stable Climbing

Wheel W11 (front-right)

W12

4)

W11 G

G

G

●

OW i3R

●

Stability

●

Climbing

5)

Rear axle steering

OpenWHEEL

W22

G

W21

Locomotion ●

Wheel W22 (rear-left)

W11

G

6)

W12

7)

G

8)

G

G W21

W22

Exp. settings Experiment Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

Stable

Unstable

Stable

Unstable

Stability if the lifted wheel is inside the turn MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

14

Stability during climbing 3D modelling Stability margin on 3 wheels when climbing = HG' 4W Stable Climbing Introduction

W12

Exploring wheel

Agile robots

Obstacle

G1

Locomotion ●

R0 W11

OpenWHEEL

●

OW i3R

●

Stability

●

Climbing

Exp. settings

R1

G W22 R2 P21

P12

H G'

G2 W21

Experiment Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

P22 MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

15

Climbing process Climbing sequence in 7 phases / 19 stages 1

4W Stable Climbing

A - Prepairing W22

Low

Introduction

2

W12

B - W 11 climbing

3

4

5

C - W 12 climbing

7

8

9

E - W 21 climbing

12

13

14

17

18

19

High

W21

W11

6

Agile robots Locomotion ●

OpenWHEEL

●

OW i3R

●

Stability

●

Climbing

Exp. settings

10

D – Going forward

15

F - W 22 climbing

11

16

G - Conclusion

Experiment Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

16

Climbing process Strong simplifying hypotheses ✔

4W Stable Climbing Introduction

✔ ✔ ✔ ✔

Agile robots

Negligible mass of the inter-axle mechanism Non-deformable bodies (i.e. infinite part stiffness) Small warping rotation-angles to avoid representation of complex 3D poses Punctual ground-wheel contact with toric wheels Perfect rolling without slipping assuming that normal forces are sufficient to ensure enough traction

Locomotion ●

OpenWHEEL

●

OW i3R

●

Stability

●

Climbing

Incremental validation ✔ ✔ ✔

Multi-body Adams model [IROS 06] Reduced model [MTM 2008] Full scale model [in process...]

Exp. settings Experiment Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

17

Wheel sub-assembly Four identical wheel sub-assemblies ✔

4W Stable Climbing

✔ ✔ ✔

One 9V actuator : 200 rpm, 3.52 N.cm on top of the wheel Transmission ratio 1/15 Rubber air-tire with good friction (Diam 49.6 mm) Overconstrained structure - mass 149 g

Introduction

2

Agile robots Locomotion

Z40

Z8

3

C

Exp. settings ●

Wheel

●

Inter-axle

●

Whole robot

●

E 0 Z8

Software

Experiment

Z24

1

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

18

Inter-axle mechanism High torque warping mechanism ✔

4W Stable Climbing Introduction

✔ ✔ ✔ ✔

The same 9V actuator as for the wheels Transmission ratio 1/560 Double worm gear redundant overconstrained transmission Minimized backlash Improved tooth strength

Agile robots

Z16

Locomotion Exp. settings ●

Wheel

●

Inter-axle

●

Whole robot

●

F1

Z16

Z8 E

F2 Z8

Software

Z56

Experiment

Z40 Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

19

Whole reduced model of the robot Whole assembly = 2 axles + 1 inter-axle mechanism 4W Stable Climbing

✔

Total weight 1430 g

✔

Center of mass quasicentered

Introduction

 G1 G=0.497 G1 G2

Agile robots Locomotion

✔

●

Wheel

●

Inter-axle

●

●

Whole robot Software

Experiment

✔

Translation speed 55mm/s

✔

Warping speed 45° in 21s (with oil)

170 mm

Exp. settings

G1

Carries its power (12 AA batteries)

G G2

W12 17 5  m

m

W22

m 0  9 1

m

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

20

Software architecture Embedded program in each control unit NQC language, BricxCC developing environment 4W Stable Climbing

✔

Introduction

✔

✔ ✔

Control unit 1 for axle 1 (Master) Control unit 2 for axle 2 and warping joint R0 (Slave) Exchanges between units via infrared port Protocol by message sending and detection loop

Agile robots Locomotion Exp. settings ●

Wheel

●

Inter-axle

●

Whole robot

●

Master program for A1

Slave program for A2+ R0

// Stage 2 : rev W22 / fwd W21 Bip(); SendMessage (2); ClearMessage(); until (Message() == 2);

  // Stage 2 : rev W22 / fwd W21   if (Message() == 2)     {     OnRev (W22);     OnFwd (W21);     Wait(150);     Off (W22+W21);     SendMessage(2);     }

Software

Experiment Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

21

Experimental climbing Purpose: validating the climbing strategy ✔

4W Stable Climbing

✔ ✔

Obstacle: 55 mm high Higher than a wheel Actuators at full speed with open loop control Useful to determine the most suitable sensors

Introduction Agile robots Locomotion Exp. settings Experiment ●

Climbing

●

Adjustments

●

Control

●

Improvement

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

Difficulties ✔ ✔

Initial tests with stabilized power – Final test with batteries Difficult to debug: the final pose depends on the full process MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

22

Phase A – Stage 01

4W Stable Climbing Introduction Agile robots Locomotion Exp. settings Experiment ●

Climbing

●

Adjustments

●

Control

●

Improvement

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

23

Phase B – Stage 02

4W Stable Climbing Introduction Agile robots Locomotion Exp. settings Experiment ●

Climbing

●

Adjustments

●

Control

●

Improvement

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

24

Phase B – Stage 03

4W Stable Climbing Introduction Agile robots Locomotion Exp. settings Experiment ●

Climbing

●

Adjustments

●

Control

●

Optional: going against the obstacle and actuating the wheel for bonus tangential force

Improvement

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

25

Phase B – Stage 04

4W Stable Climbing Introduction Agile robots Locomotion Exp. settings Experiment ●

Climbing

●

Adjustments

●

Control

●

Improvement

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

26

Phase B – Stage 05

4W Stable Climbing Introduction Agile robots Locomotion Exp. settings Experiment ●

Climbing

●

Adjustments

●

Control

●

Optional: the exploring wheel can land faster if it was lifted just at the level of the obstacle

Improvement

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

27

Phase C – Stage 06

4W Stable Climbing Introduction Agile robots Locomotion Exp. settings Experiment ●

Climbing

●

Adjustments

●

Control

●

With pitch angle and contact on four wheels, steering Axle A1 is coupled with warping the frame

Improvement

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

28

Phase C – Stage 07

4W Stable Climbing Introduction Agile robots Locomotion Exp. settings Experiment ●

Climbing

●

Adjustments

●

Control

W11 serves as a pivot for Axle A1 Slipping risk on W11

Improvement Solution: unsteer slightly Axle A2 Slightly lifts W12 Conclusion Increase normal force on W11 ●

Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

29

Phase C – Stage 08

4W Stable Climbing Introduction Agile robots Locomotion Exp. settings Experiment ●

Climbing

●

Adjustments

●

Control

●

Improvement

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

30

Phase C – Stage 09

4W Stable Climbing Introduction Agile robots Locomotion Exp. settings Experiment ●

Climbing

●

Adjustments

●

Control

●

Improvement

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

31

Phase D – Stage 10

4W Stable W and W with same speed set point Normal forces differ Climbing 11

12

Induced steering on axle A1

Introduction Agile robots Locomotion

Exp. settings Experiment ●

Climbing

●

Adjustments

●

Control

Improvement Solution: closed-loop control - to equilibrate normal forces Conclusion - to keep a constant steering angle ●

Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

32

Phase E – Stage 11

4W Stable Climbing Introduction Agile robots Locomotion Exp. settings Experiment ●

Climbing

●

Adjustments

●

Control

●

Improvement

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

33

Phase E – Stage 12

4W Stable Climbing Introduction Agile robots

Solution: additional 149 g counterweight

Locomotion Exp. settings Experiment Risk ●ofClimbing instability during W21 climbing ● Adjustments ●

●

Control Improvement

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

34

Phase E – Stage 13

4W Stable Climbing Introduction Agile robots Locomotion Exp. settings Experiment ●

Climbing

●

Adjustments

●

Control

●

Improvement

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

35

Phase E – Stage 14

4W Stable Climbing Introduction Agile robots Locomotion Exp. settings Experiment Climbing Optional: the exploring wheel can land faster if it was lifted just at the ● Adjustments level of the obstacle

●

●

●

Control Improvement

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

36

Phase F – Stage 15

4W Stable Climbing Introduction Agile robots Locomotion Exp. settings Experiment ●

●

●

●

Climbing Optional: going against the Adjustments obstacle and actuating the wheel for bonus tangential force Control Improvement

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

37

Phase F – Stage 16

4W Stable Climbing Introduction Riskrobots of instability Agile

during W22 climbing

Locomotion

Solution: additional 149 g counterweight

Exp. settings Experiment ●

Climbing

●

Adjustments

●

Control

●

Improvement

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

38

Phase F – Stage 17

4W Stable Climbing Introduction Agile robots Locomotion Exp. settings Experiment ●

Climbing

●

Adjustments

●

Control

●

Improvement

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

39

Phase F – Stage 18

4W Stable Climbing Introduction Agile robots Locomotion Exp. settings Experiment ●

Climbing

●

Adjustments

●

Control

●

Improvement

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

40

Phase G – Stage 19

4W Stable Climbing Introduction Agile robots Locomotion Exp. settings Experiment ●

Climbing

●

Adjustments

●

●

Control

Risk of lateral drift with respect to phase 1

Improvement

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

41

Design adjustments Axle A1 climbs more easily than Axle A2 4W Stable Climbing Introduction

Need for a counterweight ✔

The counterweight breaks longitudinal symmetry

✔

Possible explanation: if the centre of mass G is too high, its projection on the ground G' moves relatively to contact points Pi and stability criterion is no more respected

Agile robots Locomotion

G2

G

G1

Exp. settings

G

G2

Experiment ●

Climbing

●

Adjustments

●

Control

●

Improvement

G1

P1 P2

✔

G'

P1

P2

G'

The 149 g counterweight brings G forward of 16 mm  G1 G=m2 /m1m2  G 1 G2=0.408 G1 G2

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

42

Control Control laws for the 4 wheels and central actuator ✔ ✔

4W Stable Climbing Introduction

Phases B-D-E-F are similar in length Warping phases take 80% of time. Warping angle < 26°

700

Phase E

Angles of rotation of the actuators of OW i3R 600

Angle Angle Angle Angle Angle

500

Phase F

W12 (°) W11 (°) W22 (°) W21 (°) R0 (°)

Agile robots 400

Phase B

Locomotion

Phase C

300

Exp. settings 200

Experiment 100 ●

Climbing

●

Adjustments

●

Control

●

Improvement

0

-100

2 3

45

6

7

8

9

10 11

12

13 14

15

16

17 18

19

-200 0

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

10

20

30

40

50

60

70

80

90

89 s MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

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Control improvement The good metrics for measuring climbing ability 4W Stable Climbing Introduction Agile robots Locomotion

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Better control to improve climbing Adding sensors for precise monitoring ✔ ✔

Exp. settings Experiment ●

Climbing

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Adjustments

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Control

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Not the wheel diameter Comparison Obstacle height / Altitude of the centre of mass OpenWHEEL i3R can climb obstacles as high as 67% ZG

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Angular coders on actuators (wheels + warping central joint) Coders on passive joints (axle steering) Ultra-sound sensor to detect obstacle / measure height

Rolling without slipping ✔ ✔

Measuring normal force Pitch → Two-axes force gauges in the rim of the wheels

Improvement

Conclusion Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

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Conclusion Results 4W Stable Climbing Introduction

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A new principle for stable obstacle climbing

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Usable with only 4 wheels for simplicity

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Only one supplemental central actuator

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A climbing process in 19 stages

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Validated on a reduced model of OpenWHEEL i3R

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Climbs obstacles as high as 66% of ZCentre of mass

Agile robots Locomotion Exp. settings Experiment Conclusion

In the future ✔

Geometrical model for coupled actuation of steering / warping

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Obstacle detection and control adaptation

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Normal force / slipping regulation

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Optimizing kinematics & structure

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Optimizing climbing strategy: how much can we climb with 4 wheels ?

Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

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02

03

4W Stable Climbing 04

Introduction Agile robots Locomotion

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Next step ?

Exp. settings Experiment Conclusion

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A stable climbing process Multibody validation (Adams) Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

Experimental validation on actuated reduced model

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

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Conclusion

4W Stable Climbing Introduction Agile robots Locomotion Exp. settings Experiment Conclusion Full scale demonstrator 140 kg, 1.4m long

Fauroux / Bouzgarrou / Chapelle LaMI, Clermont-Ferrand, France

MTM2008 - 10th International Conference on Mechanisms and Mechanical Transmissions 8-10 October 2008, Polytechnichal University of Timisoara, Romania

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