## Robot Locomotion

Locomotion is the method of moving from one place to another. The mechanism that makes a robot capable of moving in its environment is called as robot locomotion.

There are many types of locomotion's:-

- Wheeled
- Legged
- Tracked slip/skid
- Combination of legged and wheeled locomotion

**Legged locomotion**

- It comes up with the variety of one, two, four, and six legs. If a robot has multiple legs then leg coordination is required for locomotion.
- Legged locomotion consumes more power while demonstrating jump, hop, walk, trot, climb up or down etc.
- It requires more number of motors for accomplish a movement. It is suited for rough as well as smooth terrain where irregular or too smooth surface makes it consume more operational power. It is little difficult to implement because of stability issues.

The total number of possible gaits (a periodic sequence of release and lift events for each of the total legs) a robot can travel depending upon the number of robot legs.

If a robot has K legs, then the number of possible events is,

In case of a two-legged robot (K=2), therefore the number of possible events is

Hence, there are six possible different events:-

- Lifting the Right leg
- Lifting the Left leg
- Releasing the right leg
- Releasing the left leg
- Releasing both the legs together
- Lifting both the legs together

In case of K=4 legs, there are 5040 possible events. Hence the complexity of robots is dependent on number of legs of robots. On increasing legs of a robot the complexity of robotic system increases.

**Wheeled Locomotion**

It requires less number of motors for accomplishing a movement. It is little easy to implement as there are lesser stability issues in case of more number of wheels. It is more power efficient as compared to legged locomotion.

**Castor wheel -** It rotates around the offset steering joint and wheel axle.
**Standard wheel -** It rotates around the contact and the wheel axle.
**Ball or spherical wheel -** This wheel is technically difficult to implement due to architectural complexity. It is an Omni directional wheel with only one directional movement is allowed.
**Swedish 45 and Swedish 90 wheels -** It is an Omni-wheel, which rotates around the contact point, around the wheel axle, and around the rollers.

**Slip/Skid Locomotion**

In Slip/Skid locomotion the vehicles use tracks as available in a tank. The robot is steered by moving tracks with different speeds in the same or opposite direction. It offers stability because of large contact area of ground and track.