Types of wheels locomotion systems

Types of wheels locomotion systems

Locomotion system stands for the rotation and alignment of the your robot body.

Basically there are five type of wheel locomotion

Differential drive

This is perhaps the most commonly used type of locomotion systems in mobile robots, because it is simple and easy to design as well as implement. This type of structure balances itself on three wheels; two of them are motor driven, while the third one is free.

The free wheel, also called pivot wheel, can be mounted at the front or at the back of the pair of wheels driven by the motors. Practically, the pivot wheel is best mounted at the back, so it acts as a ‘trailing’ wheel and not as a ‘steering’ wheel.

When both the motor driven wheels rotate in the same direction, the robot moves straight. If both wheels rotate in clockwise direction, and the robot moves forward, then when both wheels rotate in anticlockwise direction, the robot will move backward.

The robot turns when the motor driven wheels move in opposite direction. When left wheel moves clockwise and right wheel moves anticlockwise (as seen from the right side of robot), the robot turns right. On the other hand, when right wheel moves clockwise and left moves anticlockwise (again, as seen from right side of the robot), the robot turns left.

In differential type drive, zero radius of turning can be achieved by rotating the wheels at same rate in opposite direction. Another point to be noted here is that this design requires the use of two independent motors, and both of which are used in both rotational and translational motion.

Car type design

This design makes use of four wheels, two of them at the front for steering, and the rest two at the back to provide forward/ backward motion.

This design type is very common in real world, and almost all the four wheeled vehicles make use of this design. However, this design type is fairly complex and thus is generally avoided in basic robotics.

Skid steer drive

This type is very similar to the differential drive design type. There are multiple numbers of driving wheels present in this, and there is no need of pivot wheel. The left and right groups of wheels are driven independently. 

This type of drive is commonly utilized in military tanks. In robotics, we make use of this type of design when there is a need of high friction and grip on the surface, for example, they are widely used in wall climbing robots. Turning in this type of design is achieved by moving the set of wheels on each side at different rate or in different directions.

Synchronous drive

This type of design relies on synchronous movement of all the wheels to achieve motion as well as turning.  Generally, this type of design is consists of 2 sets of motors,

one set used to drive the wheels, the other set used to turn the wheels simultaneously at same angle.

Articulated drive

Probably it is the most complex design which can be used for locomotion. The body of the robot is modified to achieve rotation. Two motors are needed in this design, one of them used for translation, the other used tochange the pivot direction.

Since the body of the robot is moving internally too, mounting the circuit board and batteries on this type of structure is difficult, and hence it requires lot of planning. This type of design is followed in ‘snake type robots’.