LOCOMOTION Farahnaz AttarHamidi Samaneh Mahmoudi Mehraneh NezamiRad

C HARACTERISATION OF LOCOMOTION CONCEPT

L OCOMOTION C ONCEPTS : THOSE FOUND IN NATURE

L OCOMOTION C ONCEPTS Concepts found in nature  Difficult to imitate technically Technical systems often use wheels or caterpillars/tracks Rolling is more efficient, but not found in nature  Nature never invented the wheel! However the movement of walking biped is close to rolling

B IPED W ALKING

L EGGED LOCOMOTION

W ALKING OR ROLLING ?

M OBILE SYSTEMS WITH LEGS – W ALKING MACHINES Fewer legs complicated locomotion  stability requires at least 3 legs During walking some legs are in the air  Thus a reduction in stability Static walking requires at least 4 legs (and simple gaits)

N UMBER OF JOINT FOR EACH LEG (DOF: D EGREES OF FREEDOM )

C ONTROL OF A WALKING ROBOT Motion control should provide leg movements that generate the desired body motion. Control must consider:  The control gait: the sequencing of leg movement  Control of foot placement  Control body movement for supporting legs

L EG CONTROL PATTERNS Legs have two major states:  Stance: One the ground  Fly: in the air moving to a new postion Fly phase has three main components  Lift phase: leaving the gound  Transfer: moving to a new position  Landing: smooth placement on the ground

E XAMPLE 3 DOF L EG DESIGN

G AITS Gaits determine the sequence of configurations of the legs Gaits can be divided into two main classes  Periodic gaits, which repeat the same sequence of movements  Non-periodic or free gaits, which have no periodicity in the control, could be controlled by layout of environment

T HE NUMBER OF POSSIBLE GAITS ?

M OST OBVIOUS 4 LEGGED GAITS

S TATIC GAITS FOR 6 LEGGED VEHICLE

Examples Of Legged Robot Locomotion Although there are no high-volume industrial applications to date, legged locomotion is an important area of long-term research. Several interesting designs are presented below, beginning with the one-legged robot and finishing with six-legged robots.

1. One Leg The minimum number of legs a legged robot can have is, of course, one. The one-legged robot maximizes the basic advantage of legged locomotion: legs have single points of contact with the ground in lieu of an entire track, as with wheels. A single-legged robot requires only a sequence of single contacts, making it amenable to the roughest terrain. The major challenge in creating a single-legged robot is balance.

The Raibert Hopper

Benjamin Brown And Garth Zeglin The 2D Single Bow Leg Hopper

The Sony SDR-4X II 2003 Sony Corporation

2. Two Legs (Biped) They are able to move, jump and climb up and down the stairs and many other moves. The sony robot has 38 degrees of freedom. 7 microphone to find the sound location. Can detect human face. Can detect audio. It is capable of producing 3D maps based on stereo images.

The Humanoid Robot P2 From Honda In The Commercial Sector, Both Honda And Sony Have Made Significant Advances Over The Past Decade That Have Enabled Highly Capable Bipedal Robot.

3. Four Legs (Quadruped) These robots can stand statically, but their walking is facing problems; because the robot's center of gravity must be actively activated when walking.

4. Six Legs(Hexapod) Due to static stability while walking, the use of 6-foot robots in robotic research is very common. Usually every leg has 3 degrees of freedom.

Walking Vs Running Motion of a legged system is called walking if in all instances at least one leg is supporting the body If there are instances where no legs are on the ground it is called running Walking can be statically or dynamically stable Running is always dynamically stable

LEGGED Stability Stability means the capability to maintain the body posture given the control patterns. Statically stable walking implies that the posture can be achieved even if the legs are frozen / the motion is stoppped at any time, without loss of stability. Dynamic stability implies that stability can only be achieved through active control of the leg motion. Statically stable systems can be controlled using kinematic models. Dynamic walking or running requires use of dynamical models.

Examples Of Walking Machines So far limited industrial applications of walking. A popular research field. An excellent overview from the clawar project

S YSTEMS WITH WHEELS Wheels is often a good solution – in particular indoor Stability Maneuverability Controllability

T YPES OF WHEELS There are four types of wheels Standard wheel: two degrees of freedom – rotation around motorized axle and the contact point Castor wheel: three degrees of freedom: wheel axle, contact point and castor axle

T YPES OF WHEELS – II Swedish wheel: three degrees of freedom – motorized wheel axles, rollers and contact point Ball or spherical wheel: suspension not yet technically solved

W HEEL ARRANGEMENTS Two wheels Three wheels

W HEEL ARRANGEMENTS – II Four wheels Six wheels

STABILITY 2 wheels robot 3 wheels robot more

C ATARPILLAR / T RACKED VEHICLES Frequently used in rough terrain Requires skid steering Poor control of motion. Requires external sensors for accurate control

SHRIMP – WHEELED CLIMBING & MOTION Passive handling of rough terrain 6 wheels for stability Size 60 x 20 cm Overcomes obstacles upto double wheel diameter

R OBOTIC SENSORS

C LASSIFICATION Simple Touch Complex Touch Simple Force Complex Force Simple Vision Complex Vision Proximity External sensor Internal sensor  Position sensor  Velocity Sensor

Thanks for your attention!