Types of Robot Motion

Types of Robot Motion

As you become more familiar with how the arm mounted on the V5 Workcell moves, it becomes easier to understand the requirements of its motion. For example, to move the arm mounted on the Workcell in a straight line from the back to the front of the Workcell, two of the joints could be powered, one at a time. However, to move in a straight line from side to side on the platform, three of the joints need to be powered at the same time and at differing speeds. Industrial robots have the same types of movement requirements.

Non-Servo and Servo Robots and Their Motion

Some industrial robots use pneumatic cylinders as actuators. The motion for these robots is caused by the cylinders’ shafts being either fully in or fully out. This creates a point to a point motion without the ability to stop between those two points. These robots are known as non-servo robots.

In comparison, robots with stepper motors, servo motors, or hydraulic systems have the ability to stop at any point along the path between the two points and are known as servo-driven robots.

Many industrial robots have all their axes move at the same time to have their tool center point (TCP) follow a specific path. This path could be along a line, the shortest possible arc (part of a curve) of the arm’s joint, or a circular arc. These motion types are defined as Linear motion and Joint motion. With each of these motions, the axes involved start and stop at the same time, forcing the robot to move some axes faster than the others to complete its motion.

EOAT and Other Relevant Devices

End-of-arm tooling (EOAT) is attached to a robot after the purchase of the robot. These are also known as end effectors and can be custom-made for a specific application or purchased as a standard attachment. End effectors are used for manipulating parts such as:

• transferring parts
• assembling parts
• drilling, grinding, spot welding, or painting parts

An EOAT device can be a mechanical gripper driven electrically, by compressed air, or vacuum suction cups. An end effector can also perform a production function with tools like glue applicators, welding apparatus, drill bits, paint sprayers, etc.

Electrical EOAT can also include solenoid (electromagnetic) based devices similar to the electromagnets used in moving cars in junkyards. The V5 Workcell has a V5 Electromagnet EOAT.

The weight and design of an EOAT device has an impact on the robot operation. Engineers need to include the end-of-arm tool’s weight when making robot dynamics calculations.

Most EOAT are designed for a single function. For example, a gripper may be designed to move paint cans. This gripper would be able to pick up cans that are within a small range of sizes. This type of gripper would be known as a fixed design.

However, recently flexible gripper designs are being used to hold objects with different shapes. These grippers can also manipulate a wide range of object sizes. An example of a flexible gripper can be found on the robot used at the International Space Station (ISS).

Industrial robots may also use hand-exchange devices. These are tools that can be attached and detached pneumatically by the robot. Engineers can program these exchanges between different EOAT devices. As the robot completes one task it can automatically replace the existing EOAT with a new one for the next task.