“A robot is a re-programmable, multifunctional machine designed to manipulate materials, parts, tools,or specialized devices, through variable programmed motions for the performance of a variety of tasks.”
Robotics Industries Association
Robots are introduced into manufacturing operations for many reasons, some of which include: Work environment hazardous for human beings; Repetitive tasks; Boring and unpleasant tasks; Multishift operations; Infrequent changeovers; Performing at a steady pace; Operating for long hours without rest; Responding in automated operations; Minimizing variation. Typically they’re used for Welding / Painting / Assembly / Pick-and-place / Material handling / Drilling / Military applications / Explosive material removal.
Robot Coordinate Frames:
The vast majority of today’s commercially available robots possess five distinct design configurations
Cartesian Robots (eg Gantry robot)
Advantages:
They can obtain large work envelope because travelling along the x-axis, the volume region can be increased easily.
Their linear movement allows for simpler controls.
They have high degree of mechanical rigidity, accuracy, and repeatability due o their structure.
They can carry heavy loads because the weight-lifting capacity does not vary at different locations withing the work envelope.
Disadvantages:
They makes maintenance more difficult for some models with overhead drive mechanisms and control equipment.
Access to the volume region by overhead crane or other material-handling equipment may be impaired by the robot-supporting structure.
Their movement is limited to one direction at a time.
Cylindrical Robots
Advantage:
Their vertical structure conserves floor space.
Their deep horizontal reach is useful for far-reaching operations.
Their capacity is capable of carrying large payloads.
Disadvantage:
Their overall mechanical rigidity is lower than that of the rectilinear robots because their rotary axis must overcome inertia.
Their repeatability and accuracy are also lower in the direction of rotary motion.
Their configuration requires a more sophisticated control system than the rectangular robots.
Spherical Robots
Advantage:
Versatile
Large Working Envelope
Disadvantage:
Its more difficult to control the end effectors position
A large area (at the base of the robot) cannot be reached.
Articulated Robots
Advantage:
Extremely flexible
Can reach anywhere within the workspace
Joints can be completely sealed
Disadvantage:
Can be difficult to program – the controller can be quite complex
Payload can be quite low
SCARA (Selective Compliance Assembly Robot Arm) Robots
Advantage:
Very fast
Compact and can operate through 360 degrees (plan)
Disadvantage:
Medium to low payload
Limited vertical movement
Typical Robot Components
Controller
Every robot is connected to a computer controller, which regulates the components of the arm and keeps them working together. The controller also allows the robot to be networked to other systems, so that it may work together with other machines, processes, or robots. Almost all robots are pre-programmed using “teaching” devices or off-line software programs (OLP). In the future, controllers with artificial intelligence (AI) could allow robots to think on their own, or even program themselves. This could make robots more self-reliant and independent.
Arm
The arm is the part of the robot that positions the end-effector and sensors to do their pre-programmed business. Many are built to resemble human arms, and have shoulders, elbows, wrists, even fingers. Each joint is said to give the robot 1 degree of freedom. A simple robot arm with 3 degrees of freedom could move in 3 ways: up and down, left and right, forward and backward. Most working robots today have 6 degrees of freedom to allow them to reach any possible point in space within its work envelope (or ‘working volume’).
Drive
The links (the sections between the joints) are moved into their desired position by the drive. Typically, a drive is powered by pneumatic or hydraulic pressure, or, most commonly, electricity.
Hydraulic drives: powerful, deliver large forces, require pumps.
Pneumatic: cheap, practical (most factories have air lines), safe, difficult to control.
Electric: good precision, good accuracy, stepper or DC servo (most common)
End-effector (or tool)
The end-effector could be thought of as the “hand” on the end of the robotic arm. There are many possible end-effectors including a gripper, a vacuum pump, tweezers, scalpel, blowtorch, welding gun, spray gun, axe, hair clippers, or just about anything that helps it do its job. Some robots can change end-effectors, and be reprogrammed for a different set of tasks.
Sensors
A sensor sends information, in the form of electronic signals back to the controller. Sensors also give the robot controller information about its surroundings and lets it know the exact position of the arm, or the state of the world around it. One of the more interesting areas of sensor development is in the field of computer vision and object recognition. Other types of sensors include ultrasonic, lasers, force/touch etc.
Find out more about Robots in our Posts
Information sourced from:
– The society of robots http://www.societyofrobots.com/robot_arm_tutorial.shtml
– SME Robot http://smerobot-tools.prospektiv.de/robotic/eng/robot_types.html
If you would like to learn about robots in greater detail, I recommend the following sources:
http://www.ene.ttu.ee/elektriajamid/oppeinfo/materjal/AAR0040/01_Robotics.pdf
http://www2.tec.ilstu.edu/students/tec_234/ABB_Procedures/coordinate_systems.pdf
www.kuka.com/en/products/systems
www.kawasakirobot.co.uk/applications
