Functions of Robots

Like other computer systems, robotic systems are composed of hardware and software. Movement is an important function of many robots and it is the hardware and software which facilitate this process.

MOVEMENT

Robotic motion is described in terms of degrees of freedom.

One degree of freedom is equal to one movement either back and forth (linear movement), or around in a circle (rotational).

Degrees of Freedom in the Human Arm

To understand how this works, consider the human arm. The human arm has six degrees of freedom, allowing the following movements:

  • shoulder—up and down (one degree)
  • shoulder—forward and backward (one degree)
  • elbow—up and down (one degree)
  • wrist—rotate (one degree)
  • wrist—up and down (one degree)
  • wrist—left and right (one degree).

Degrees of Fredom in the Human Arm

Degrees of Freedom in a Robot Arm

Additionally the operation of thumbs and fingers gives several more degrees of freedom. In a robotic system, usually one robotic joint corresponds to one degree of freedom, but this depends on how the hardware is connected. Most jointed robots have six degrees of freedom that are similar to the human arm; an articulated arm type, for example, usually has six degrees of freedom. Six degrees of freedom is usually sufficient to conduct most simple tasks.

So, in a robot with an articulated arm, the following movements are possible:

  • arm—up and down (one degree)
  • arm—lengthen and shorten (one degree)
  • body—rotate (one degree)
  • wrist—up and down (one degree)
  • wrist—rotate (one degree)
  • wrist—left and right (one degree).

Degrees of Freedom in a Robotic Arm

Moves of Robots

Robots move in three ways: pick-and-place, point-to point and contouring.

  • Pick-and-place—this movement has only two positions per axis and suits loading and assembly functions in mass-production situations.
  • Point-to-point—this movement is controlled from one point location in space to another. Each point is programmed into the robot’s control memory and then played back during the work cycle. This type of movement is suited to tasks such as spot welding.
  • Contouring—this movement allows the robot to follow a path which forms the shape of a smooth curve. The robot’s gripper carries out a programmable path movement and performs variable functions on this path. Applications include spray painting, continuous welding and grasping objects moving along a conveyor.