Robot Mechanical Transmission Systems

The links and joints of a robot will require anyone of the drive systems (electric, hydraulic, and pneumatic) to perform several motions. However, the necessary speed or torque is not gained even with the use of an actuator. As a result, the mechanical transmission system is applied. There are many methods for transferring mechanical power such as:

  • Gears
  • Belts
  • Harmonic Drives


The rotational motion of one shaft is transmitted to another with the help of gears. The transferring of power can be either in intersecting or parallel shafts. It is the most frequently used mechanical transmission system in the robots. The added advantage of the gears is that the speed can be decreased or increased according to the operation.

Types of gears:

  • Spur gears
  • Bevel gears
  • Helical gears
  • Worm and Worm Wheel

a) Spur gears:

The arrangement of two parallel and coplanar shafts is done by the spur gears. These gears can be fitted externally and internally as well. The spur gear will rotate in the same way in the internal gearing, and it revolves in the opposite way in the external gearing. It is used in the clocks, gear box, and lathe back gear.

b) Bevel gears:

The bevel gears are implemented for connecting two coplanar intersecting shafts. It is capable of transferring power up to 900. It is mostly used in drill chuck key, differential of automobile, etc.

c) Helical gears:

The connection of intersecting shafts and non-parallel or parallel shafts is performed by the helical gears. The major benefit of this gear is that it transfers high power. The operation is done smoothly and creates less vibration too. It is used in IC engines shaft & timing gears, and automobile gear box.

d) Worm and Worm Wheel:

It can integrate shafts that are perpendicular to each other. Here, the driver is worm and driven is worm wheel. The advantage of using worm and worm wheel is that it can transmit high power and efficiency along with the reduced velocity ratio. Some of the applications are wind shield wiper, index head, and steering gear box.


  • Better efficiency
  • High Durability
  • Compact


  • High manufacturing cost
  • Improper arrangement of tooth causes high noise.


The belts are another type of power transmission system. It is used in the robots to transmit the power. It is not so physically powerful, but it can deliver smooth and quiet process with the help of the shock absorber.

Types of belts:

  • V belt
  • Flat belt
  • Circular belt

V Belt:

The V belt is highly used to transmit the maximum amount of power to the pulleys. It has the cross-section of trapezoidal. It is the best type to connect the pulleys that are close to each other.


  • Less floor space
  • No possibility of slip
  • Easy to maintain


  • Difficult to construct
  • High cost

Flat Belt:

The flat belt combines the pulleys up to 10 meters distance, and transmits a medium amount of power. It is of rectangular cross section type. It can be classified into three key types namely cross belt, open belt, and compound belt.


  • Simple in construction
  • Smooth process
  • Low cost


  • Huge in size
  • Possibility of slip

Circular Belt:

The circular belt is also known as the rope drive in which the cross section is circular. It is largely included in the robots for gaining maximum amount of power between the pulleys. If the center distance of one pulley and the other is more than 5 meters, then this type of belt is mostly used.


The harmonic drives are incorporated for increasing and decreasing the speed. It is related to the mechanism of non rigid material. The decrease ratio of harmonic drives is 1:1 to Infinity: 1 and it is commonly set as 100:1. An important advantage is that it can work for life time with less maintenance. When this drives is compared to the gears, it is less efficient.

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