Unit 121: Engineering Industrial Robot Technology

Lecture (2)

Robot Design

Session Outline:

• Manipulator coordinate systems

• Wrist articulations

• Drive mechanisms

• Speed reducers/ gearheads

Manipulator coordinate systems Cartesian

Cylindrical

Spherical

Selective Compliant Assembly Robot Arm (SCARA)

Articulated Robot

Joint Types

1- Prismatic joint where the pair of links makes

a translational displacement along a fixed axis. In

other words, one link slides on the other along a

straight line. Therefore, it is also called a sliding

joint.

2- Revolute joint where a pair of links rotates

about a fixed axis. This type of joint is often

referred to as a hinge, articulated, or rotational

joint.

Cartesian Coordinates

Cartesian coordinate robot has three

prismatic joints, corresponding to three

axes denoted x, y , and z.

Cylindrical Coordinates

The cylindrical robot consists of one revolute

joint and two prismatic joints, with r, Θ and z

representing the coordinates of the end-effecter.

Spherical Coordinates

the spherical robot has two revolute joints

denoted Θ and Φ and one prismatic joint

denoted r.

SCALAR Type Robot

SCALAR robot consisting of two revolute joints and one prismatic joint.

This robot structure is particularly desirable for assembly automation in

manufacturing systems, having a wide workspace in the horizontal

direction and an independent vertical axis appropriate for insertion of

parts.

Articulated Robot

Articulated robot or an elbow robot, consists of all three revolute joints,

like a human arm. This type of robot has a great degree of flexibility

and versatility, being the most standard structure of robot manipulators.

Wrist articulations Yaw

Pitch

Roll

Degrees of freedom

Wrist articulationsTranslation:

1- Moving up and down

2- Moving left and right

3- Moving forward and backward

Rotation:

4- Tilting forward and backward (pitching);

5- Turning left and right (yawing);

6- Tilting side to side (rolling)

Drive mechanismsMechanical (ball screws, chain/belt, gears)

Pneumatic

Hydraulic

Electrical

Mechanical (ball screws, chain/belt, gears)

A ball screw is a mechanical linear actuator that translates rotational

motion to linear motion with little friction. A threaded shaft provides a

helical raceway for ball bearings which act as a precision screw.

Vid. 1

Vid. 2

Pneumatic System

is a section of technology that deals with the study and application of

pressurized gas to effect mechanical motion.

Advantages of pneumatics

Simplicity of Design And Control

Machines are easily designed using standard cylinders & other components.

Reliability

Pneumatic systems tend to have long operating lives and require very little

maintenance.

Because gas is compressible, the equipment is less likely to be damaged by shock.

The gas in pneumatics absorbs excessive force, whereas the fluid of hydraulics

directly transfers force.

Storage

Compressed gas can be stored, allowing the use of machines when electrical power

is lost.

Hydraulic System

A hydraulic drive system is a drive or transmission system that

uses pressurized hydraulic fluid to drive hydraulic machinery

Speed reducers/ gearheadsHarmonic

Cycloidal

parallel shaft spur gear

Planetary

Cycloidal Drive

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