ROBOTICS 1

Robotics

an applied science that emerges from the utilization of knowledge in many disciplines together for analyzing and designing robots. One of the fundamental sciences is mechanical engineering which will be useful for the design and analysis of the mechanisms that can produce the desired motion of an industrial robot.

robot

a reprogrammable, multifunctional manipulator designed to move materials, parts, tools, or specialized devices through variable programmed motion for the performance of a variety of tasks. A robot can also be defined as a computer controlled machine with some degrees of freedom.

Body

the skeleton of the robot

Arm or Manipulator

positioning of tools, mimic human functions

End Effectors

devices attached to the robotic wrist, acts as a hand, EOAT (end of arm tooling)

Drive Mechanism

engine or motor responsible for power and movement

Controller

– serves as the robot’s brain

Sensors and transducers

– provides feedback and other abilities

Degrees of Freedom

The ability to move about its environment.

Linear joint - type L

Axes of input and output link are parallel

Orthogonal joint (type O)

Input and output links are perpendicular

Rotational joint (type R)

Axis of rotation is perpendicular to input and output link axis

Twisting joint (type T)

Axis of rotation parallel to axis of links

Revolving joint (type V)

Axis of rotation parallel to input but perpendicular to output

Hydraulic

§ High strength and high speed § Large robots, Takes floor space § Mechanical Simplicity § Used usually for heavy payloads

Electric Motor

§ High accuracy and repeatability § Less floor space § Low cost § Easy maintenance

Pneumatic

Smaller units, quick assembly § High cycle rate § Easy maintenance

Spherical / Polar (RRP)

Notational TRL

Consists of a sliding arm (L joint) actuated relative to the body, which can rotate about both a vertical axis (T joint) and horizontal axis (R joint).

Used for handling machine tools

Cylindrical

• Notational TLO
• Consists of a vertical column, relative to which an arm assembly is moved up or down.
• The arm can be moved in or out relative to the column • Used for assembly, handling machine tools, spot welding, and handling at-die casting machines.

Cartesian

• Notational LOO
• Consists of three sliding joints, two of which are orthogonal
• Other names include rectilinear robot and x-y-z robot
• Used commonly for lifting heavy objects

Articulated / Jointed-arm

• Notational TRR
• Consists of three sliding joints, two of which are orthogonal
• Other names include rectilinear robot and x-y-z robot
• Used for assembly operations

SCARA

• Notational VRO
• Stands for Selectively Compliant Assembly Robot
• Similar to jointed-arm robot except that vertical axes are used for shoulder and elbow joints to be compliant in horizontal direction for vertical insertion tasks.

Spherical/Polar Robots

• Repeatability: poor 0.5 - 1mm
• No. Of axes: 3 arm-axes (1 linear radial), 1-2 additional wrist-axes
• Working envelope: large vertical envelope relative to the unit size • Payload: 5-100kg
• Speed: low (linear motions are not smooth and accurate – require coordination of multiple axes)

Applications: Material handling, spot welding, machine loading

Cylindrical Robots

• Wide range of sizes
• Repeatability: vary 0.1 – 0.5mm
• No. Of axes: 3 arm-axes (2 linear) • Working envelope: typically large (vertical stroke as long as radial stroke) • The structure is not compact
• Payload: 5-250kg
• Speed: 1000mm/s, average
• Cost: inexpensive for their size and payload

Applications: • Small robots: precision small assembly tasks • Large robots: material handling, machine loading/ unloading

Cartesian Coordinate Robots

Repeatability: high 0.015 – 0.1mm
• No. Of axes: 3 linear arm-axis
• Working envelope: relatively large
• Payload: 5-100kg
• Speed: fast

Applications: Precise assembly, arc welding, material handling

Articulated Coordinate Robots

• Repeatability: high 0.1 – 0.5mm (large sizes not adequate for precision assembly)
• No. Of axes: 3 rotary arm-axes, 2-3 additional wrist axis (excellent wrist articulation)
• Working envelope: large relative to size, structure compact, but not so rigid
• Payload: 5-130kg
• Tool-tip speed: fast 2000mm/s

Applications: Welding, painting, sealing, deburring, and material handling

SCARA Coordinate Robots

• Repeatability: < 0.025mm (high)
• No. Of axes: min. 4 axes
• Vertical motions smoother, quicker, precise (due to dedicated vertical axis)
• Good vertical regidity, high compliance in the horizontal plane • Working envelope: range < 1000mm
• Payload: 10-100kg
• Tool-tip speed: fast 1000-5000mm/s

Applications: Precision, high-speed, light assembly

Gantry Robots

• Repeatability: 0.1 – 1mm
• No. Of axes: 3 linear traverse-axes, 1-3 additional wrist axes
• Working envelope: very large
• Payload: vary function of size, support very heavy 10-1000kg
• Speed: low for large masses

Applications: Handling very large parts, moving material on long distances, welding, gluing