snake robot project

Snake Motion inspired Robots

Outline

• Robot Motion Models

• Snake Locomotion

• Snake Robot Model

• Proposed Model

• Design and Technical Concerns

• Implications and Future Work

Motivation

• Occupy a wide variety of ecological niches

• Movement without limbs

• Small cross section to length ratio

• Ability to change the shape of their body

"To walk is human, to slither divine"

Other Models

Applied AI Systems, Inc., Canada

Ijspeert et al

Science 315, 1416

2007

Advantages of Serpentine Locomotion

STABILITY• Potential Energy low in most situations

• Less probable failure points

TERRAINABILTY• Can climb heights many times it’s own girth

• No possibility of getting stuck


TRACTION• Moving Snake can exert a force upto a 3rd of

it’s own weight

• Large contact area results in greater traction

EFFICIENCY• Reduced costs due to low COG, elimination of

acceleration and decceleration of limbs


SIZE & SHAPE• Small frontal area

• Slender design implies better maneuverabilty

REDUNDANCY• Employs simple motion actuators in sequence

• Failure/Defect could be easily replaced

Snake Locomotion

Scales & Weight distribution.

Scales have similar design as Wheels and Ice

skates.

•Lateral undulation S-shaped wave travelling from head to tail, it is the

most common and efficient mode, and used by almost all snakes. Snake’s

body moves back and forth causing lateral waves that force longitudinal

motion.

Used mostly in areas with uneven or variable terrain . e.g swimming

snakes, anguilliform swimming lampreys eels.

•Rectilinear locomotion ("inchworm" )employed by the heavyweights snake

like boas & pythons. By cyclically “fixing” parts of the skin to the ground

using scales, and then moving the backbone forward with respect to the skin,

and finally releasing the scales allowing the skin to move forward. Stabbing

and pushing mechanism of the scales. Very slow motion used while

stalking its prey.

•Concertina mode: can be thought of as snake taking steps. Part of the

snake’s body is pushed against a surface forming a small number of waves:

by moving these waves, and the corresponding contact points, the snake

progresses.

The only place where concertina progression is primarily used is by arboreal

snakes on tree limbs as one part is always attached to the tree ,here LU and

RP are difficult.

•Sidewinding is used by desert snakes that need to move on sand; Fastest

mode of locomotion can be thought of as equivalent to horse galloping. In this

mode, the snake lifts a part of the body to maintain only a few contact points

with the ground, using them to move the rest of the body.

Other types of locomotion:

Climbing:The two most common ways of ascent are LU and RP. Hard to

believe a snake lashing itself up a tree, but it does work and ascent is fluid.

When on branches the much safer concertina mode is used in place of the other

two

Swimming:The horizontal undulatory progression lends itself well to moving

through water and is employed by most aquatic serpents. Even large snakes

like Python reticulatus and Eunectes murinus are known to use HUP in the

water (something large boids generally avoid doing on land).

Flying:Flying snakes have longitudinal hinges on their ventral scales which

allows them to create a concavity which creates more surface area for air to

pass through which creates drag, which slows descent and voila, we have flight.

Simulation of Motion

Miller et. Al.

Simulation Implementation

Which Gait should we choose??

Factors influencing Selection

• Speed

• Terrain

• Ability to maneuver

• Energetic efficiency

Lateral Undulation

Configuration Parameters

•Design

•Morphology

•Control System

Design

• Segments – “vertebrae”

• Actuators – “Muscles”

Morphological Segments connected by universal joints

Actuator is a mechanical device for controlling a mechanism.

Takes Energy and converts into motion

Mechanism was proposed by Dr. Hirose and is called Active Cord

Mechanism5

Design Optimization

• Number of Scales and Angle of rotation

For Speed Number Of Segments

But , Number Of Segments Design Complexion

Earlier Models –

Dr. Hirose et. Al.

10 Segments – 20

actuators

S5 – Miller et. Al.

Closest to natural snake

locomotion

32 Segment – 64

actuators

Snakes usually have 100-400 segments

Morphology

Low friction force -in the direction of forward

movement

High friction force - in lateral directions

Achieved By Directionality of scales

Dowling et. al.

Fiber Skins with

various surface

treatments

Control System

“Follow the Head”

Travelling Wave

propagated from head to

tail

Generated from predefined gait

patterns, usually computed as sine

waves

Works pretty well for uniform terrains

Velocity changes with friction

coefficients

What will happen when the terrain changes??

phase difference between the head and tail

joints will not remain constant – Snake will wriggle in

place

Jae-Kwan Ryu et all.

Central Pattern Generators (CPG)

Matsuoka’s neural oscillators on each joints –

take velocity as input and modulate frequency

can be defined as neural networks that can endogenously produce

rhythmic patterned outputs

Jae-Kwan Ryu et

al.

Work On

Feedback

Mechanis

m

Existing Models

1. Robots that move using powered wheels

http://zedomax.com/blog/wp-content/uploads/2007/04/servo-snakebot.jpg

Existing Models

2. Robots that move by applying torques on the joints between the segments. Can have passive wheels.

Ref : Hirose et. al

Technical Concerns

• For search and rescue missions, and possible medical applications.

Waterproofing.

Completely autonomous.

Distributed control

Different type of movement for different terrains.

Remote controlled - GSM against radio-

waves

Degree of freedom

Falling over

The movement patterns obtained with the

robot have to be compared to biological

data.

Proposed Design

Multiple identical elements – same algorithm, easy to replace , redundancy

Distributed actuation, power and control

Each individual element is made waterproof

The center of gravity is placed below the geometrical center.

Large lateral surfaces for good swimming efficiency.

Asymmetric friction for the lateral undulatorylocomotion

Controlled by a CPG mechanism

Remotely controlled in terms of speed and direction commands, but otherwise have an onboard locomotion controller for coordinating its multiple degrees of freedom.

For better control – servo motors in head and tail with paddles.

Sensing – points of contact with the ground.

Miniaturization – use of bionic arm like mechanism. 70 % weight is due to motors.

Proposed Model

Linker Design and mechanism

Ref : Dowling et. al.

Expected outcome

• Based on the work plan we will get a fully functional robotic snake which should be capable of autonomous motion in a 3d environment by mimicking the snake movement of lateral undulation.

• The robot will be easy to control and will be able to traverse through rough terrain, rubble, sand, fluids or over obstacles with ease.

• Making the robot design simple(bionic arm method) , we should be successfully be able to miniaturize it thus giving us a lot more interesting applications like medical applications.

Amphibious ACM R5 robot snake –

Hirose Fukushima Robotics Lab

Snake Bot – Sacros designs,

Utah

Applications

• Can be used to detect leaks in oil pipes

• Can be used in search and exploration missions during earthquakes and floods.

• Essentially can be used to reach or explore places which are not easily accessible.

• If scaled down significantly, it could even be used for a very specific drug delivery system.

Anna Konda – a fire fighting robot, SINTEF Norway

Robot motion in a fluid

Future work

• With advancement in technology, we should be able to make smaller motors which will enable us to make smaller robot snakes with good control.

• By studying all the methods of movement, we can design a robot snake to change its motion from serpentine to concertina to side-winding, simply by providing different inputs to each segment.

• The material used to make the robot must be improved upon to better mimic the scales and stretchable skin of the snake.

Take home message…

• Motivation/Background

•Motion of the snake

•Models and Work plan

•Applications and challenges

snake robot project

Documents