R U S S I A N S T A T E S C I N T I F I C C E N T R E

R U S S I A N S T A T E S C I N T I F I C C E N T R ER U S S I A N S T A T E S C I N T I F I C C E N T R EC E N T R A L R E S E A R C H A N D D E S I G N I N S T I T U T E O F C E N T R A L R E S E A R C H A N D D E S I G N I N S T I T U T E O F

R O B O T I C S A N D T E C H N I C A L C Y B E R N E T I C SR O B O T I C S A N D T E C H N I C A L C Y B E R N E T I C S

5th APRIL 2006

Oleg Shmakov

CRDI RTC DEPARTMENT OF SPbSPU

Joint Advanced Student School 2006Saint Petersburg

Course 5: Mechatronics – Foundations and Applications

Introduction

• Why snakelike robots?• Biomechanics of snakes• Review• Mechanic model of snakelike robots• Mathematical model of snakelike robots• Hardware realization control• Snakelike robot CRDI RTC• Conclusion

Oleg A. Shmakov Snakelike robots locomotions control

Why snakelike robots?Advantages

• Stability

• Terrainability is the ability of a vehicle to traverse rough terrain • Traction is the force that can be applied to propel a vehicle

• Redundant

• Simple anatomy


Why snakelike robots? Applications

• Search and Rescue• Examination blockages after earthquake• Planet’s exploration • Medical applications • Examination hard-to-reach areas • Tube inspection• Bio Terrorist• Remote sampling• Military inspection• …

Biomechanics of snakesVertebrate


Real snakes have 100-400 vertebrae

Snake vertebral articulation is one of the most complex of all vertebrates.

Biomechanics of snakes Locomotion modes

• Lateral undulation• Sidewinding• Propulsion (with creeping)• Concertina• Rectilinear movement


ReviewDesign snakelike robots


Non-modular Modular

WITH WHEELS WITHOUT WHEELS

ReviewHirose & Umetami - SERPENOID


• the waveform that the snake assumes during creeping movement is a curve which changes sinusoidally along the curvature of the body, and a formula for this, called a serpenoid curve.

ReviewHirose & Umetami – ACM III

• Active Cord Mechanisms – ACM

• Wheeled robots

• Robots that could perform lateral undulation


• Hirose’s development of modeling and control first derived expressions of force and power as functions of distance and torque along the curve described by the snake.

• Comparisons with natural snakes across constant friction surfaces showed close agreement between the serpenoid curve and the empirical data.

• Snakes quickly adapt locally to variations in terrain and environment.

• The control took the form of angle commands at each joint

ReviewHirose & Umetami – ACM R3


ReviewCarnegie Mellon University – Kevin Dowling


ReviewCarnegie Mellon University – Biorobotics Lab


Mechanic model of snakelike robotsDobroluybov A.I.


1970 - Dobroluybov A.I.

«genetic relationship» wheels and waves and

Snakes are using rolling motion ”

Some points of a moving body or set of bodies during movement should vary periodically roles: mobile points become motionless and on the contrary. On character of this procedure of locomotion can be divided into two big classes: pacing when reference points of a body only during some moments of time pass from motionless in a mobile condition and back, and rolling when these transitions are carried out continuously. Snakes can move by pacing and rolling. Carry of points of a support of the essences, moving in the way rolling, can be various.

Mechanic model of snakelike robotsIvanov A.A.


Mechanic model of snakelike robotsIvanov A.A.


Lateral bendingRectilinear movement

curving (without creeping)

Side winding

Concertina

Shank movement

Propulsion (with creeping)

Mathematical model of snakelike robotsHow to control?

• Random Search• Hill climbing• Simulated• Annealing• Neural Nets• Response Surface Methods• Genetic Algorithms• Trigonometric forms• Fourier• Parametric curves• Bayesian optimization

algorithms


DOWLINGCONROTANEV

CMU – Biorobotics Lab

Genetic algorithms for locomotions control


Category Value

Function set {sin, cos, +, -, *, /}

Terminal set {time, segment_ID, Pi, random constant, ADF}

Population size 200 individuals

Selection Binary tournament, ratio 0.1

Elitism Best 4 individuals

Mutation Random subtree mutation, ratio 0.01

Fitness Velocity of simulated Snakebot during the trial

Trial interval180 time steps, each time step account for

50ms of “real” time

Termination criterion

(Fitness >100) or (Generations>30)or (no improvement of fitness for 16

generations)

Fitness convergence characteristics of 10 independent runs of GP for cases where fitness is measured as velocity in any direction (a) and snapshots of sample evolved best-ofrun sidewinding locomotion gaits of simulated Snakebot (b, c), viewed from above. The dark trailing circles depict the trajectory of the center of the mass of Snakebot. Timestamp interval between each of these circles is fixed and it is the same (10 time steps) for both snapshots.

Trajectory of the central segment (cs) around the center of mass (cm) of Snakebot for a sample evolved best-of-run sidewinding locomotion (a) and traces of ground contacts (b).

The determined approach of Ivanov A.A.


Hardware realization control


С0 С1 С2

18 1916 1714 1512 1310 118 96 74 52 30 1

RS232

Microcontrollers

Hardware realization control


microcontroller DC motorsFeedback from sensing

Control & power

SensorsPower supply

MAINMicrocontroller

For all joints(CMU)

Snakelike robot CRDI RTC


Total mass 3 kg

Length 1120 mm

Width 65 mm

Maximal course torque 0,3 Nm

Maximal pitch torque 1,2 Nm

Number of the links 16

Number of the joints 15

Number of the servos 30

Voltage 4,8 – 6 V

System of snakelike robot control

“SnakeWheel -1”

Coding - MAX 232

Power supply servo

PC

Camera

Power supplyMicrocontrollers

6 volt

4.8 - 6 volt

USB 1.1RS232


Structural control scheme

AA F1 1 CS59 60

63 byte

63 byte*


Low level control

1 channel 2 channel 1 channel

t, мс

10 мс

20 мс

0,9 1,5 2,1

fsend ≤ 50 Гц

t

φ

T

20 – 40 main points

fsend = 30 – 60 Гц

fbase = 1,5 Гц

T ≥ 2/3

fsend ≤ 50 Гц

60°/0,11 с


Software scheme

Entering parameters

Send

VisualizationBlocOf

Protection

BlokChangingmovement

BlocCamera control

Forming

RS-232


Software – snake-charmer


EXPERIMENTLateral bending

Amplitude corner by course

35

Amplitude corner by pitch 18

Quantity link which are using in course wave

8


4

Phase 0

SPEED (max) (cm/sec) 2.5

SPEED (min) (cm/sec) 1


EXPERIMENTLateral bending


EXPERIMENTSide winding

Amplitude corner by course

35

Amplitude corner by pitch 20


8


8

Phase π/2

SPEED (max) (cm/sec) 4,3

SPEED (min) (cm/sec) 3


EXPERIMENTSide winding


EXPERIMENTMotion on the given curve


EXPERIMENTMotion on the given curve


Conclusion


?Thank you for your attention


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