Industrial Automation and Robotics Muhajir Ab. Rahim School of Mechatronic Engineering UniMAP

Introduction The Robotics Industries Association (RIA) defines robot in the following way: “An industrial robot is a programmable, multi- functional manipulator designed to move materials, parts, tools, or special devices through variable programmed motions for the performance of a variety of tasks” An industrial robot consists of a number of rigid links connected by joints of different types, controlled and monitored by a computer. To a large extend, the physical construction of a robot resembles a human arm.

Industrial Robots Robots are used in a wide range of industrial applications. The earliest applications were in materials handling, spot welding, and spray painting. Robots were initially applied to jobs that were hot, heavy, and hazardous such as die casting, forging, and spot welding.

Welding Applications Perhaps the most popular applications of robots is in industrial welding. The repeatability, uniformity quality, and speed of robotic welding is unmatched. The two basic types of welding are spot welding and arc welding, although laser welding is done. The automotive industry is a major user of robotic spot welders

Spray Painting Applications Another popular and efficient use for robots is in the field of spray painting. The consistency and repeatability of a robot's motion have enabled near perfect quality while at the same time wasting no paint

Assembly Operations Robots lend themselves well to the tedious and repetitive nature of assembly tasks provided that the proper planning and design have been done. In addition, their high level of repeatability has allowed the development of some new technologies in electronic assembly

Palletizing and Material Handling

Power Sources for Robots An important element of a robot is the drive system. The drive system supplies the power, which enables the robot to move. (Electric, Hydraulic, Pneumatic) The dynamic performance of a robot mainly depends on the type of power source.

Hydraulic Drive Preferred for moving heavy parts Not preferred to be used in explosive environments Occupy large space area There is a danger of oil leak to the shop floor

Electric Drive Good for small and medium size robots Better positioning accuracy and repeatability stepper motor drive: open loop control DC motor drive: closed loop control Cleaner environment The most used type of drive in industry

Pneumatic Drive Preferred for smaller robots Less expensive than electric or hydraulic robots Suitable for relatively less degrees of freedom design Suitable for simple pick and place application Relatively cheaper

System characteristics Mechanical systems use solid materials such as metal, wood, or plastic formed into shafts, gears, pulleys, levers, rods, cams and other parts to transmit power. Hydraulic systems use a liquid, usually oil, which is pumped into hydraulic cylinders or hydraulic motors and made to do work. Pneumatic systems use a gas, usually air, which is pressurized and then directed into pneumatic cylinders and made to do work.

Advantages 1.pose little or no safety hazard when not operating 2.easy to troubleshoot and repair 3.reliable to harsh environment 4.many ready standardized parts available in market Disadvantages 1.heavy and adds inertia 2.need periodic lubrication and protection 3.power transmission is limited 4.must be made strong Mechanical System

Hydraulic System Advantages 1.high force level 2.amount of force can be controlled with high degree precision 3.motion can be reversed/started/stopped quickly 4.can be made portable and stored Disadvantages 1.must be totally enclosed 2.entire system must be located closed to the point of actual usage 3.always have potential of fire hazard 4.limited speed of operation

Pneumatic System Advantages 1.air is readily available 2.low pressure loss in air lines (single compressor can supply pressurized air to several machines place a great distance away) 3.motion can be reversed very quickly 4.can stored energy for reserve or emergency use Disadvantages 1.lack of precision control 2.when air is compressed, heat is produced 3.air taken from atmosphere need to be filtered and dried 4.leaks can produce high pitch noise (hazardous to hearing)

Why? Why speed of operation is limited in hydraulic systems? If hydraulic oil flows to fast, it becomes turbulent and losses pressure. Why motion can be reversed very quickly in hydraulic and pneumatic systems? Little inertia

Robotic Sensors Sensors provide feedback to the control systems and give the robots more flexibility. Sensors such as visual sensors are useful in the building of more accurate and intelligent robots. The sensors can be classified as follows a) Position Sensors b) Range Sensors c) Velocity Sensors d) Proximity Sensors

Position Sensors Position sensors are used to monitor the position of joints. Information about the position is fed back to the control systems that are used to determine the accuracy of positioning.

Range Sensors Range sensors measure distances from a reference point to other points of importance. Range sensing is accomplished by means of television cameras or sonar transmitters and receivers

Velocity Sensors They are used to estimate the speed with which a manipulator is moved. The velocity is an important part of the dynamic performance of the manipulator. The DC tachometer is one of the most commonly used devices for feedback of velocity information. The tachometer, which is essentially a DC generator, provides an output voltage proportional to the angular velocity of the armature. This information is fed back to the controls for proper regulation of the motion

Proximity Sensors They are used to sense and indicate the presence of an object within a specified distance without any physical contact. This helps prevent accidents and damage to the robot. Examples of proximity sensors are; - infra red sensors - acoustic sensors - touch sensors - force sensors - tactile sensors (for more accurate data on the position)

The Hand of a Robot: End-Effector The end-effector (commonly known as robot hand) mounted on the wrist enables the robot to perform specified tasks. Various types of end-effectors are designed for the same robot to make it more flexible and versatile. End-effectors are categorized into two major types: (grippers and tools)

Grippers Grippers are generally used to grasp and hold an object and place it at a desired location. - mechanical grippers - vacuum or suction cups - magnetic grippers - adhesive grippers - hooks, scoops, and so forth

Tools A robot is required to manipulate a tool to perform an operation on a workpiece. In such applications the end-effector is a tool itself - spot-welding tools - arc-welding tools - spray-painting nozzles - rotating spindles for drilling - rotating spindles for grinding

Robot Movement Speed of response and stability are two important characteristics of robot movement. Speed defines how quickly the robot arm moves from one point to another. Stability refers to robot motion with the least amount of oscillation. A good robot is one that is fast enough but at the same time has good stability Speed and stability are often conflicting goals. However, a good controlling system can be designed for the robot to facilitate a good trade- off between the two parameters

Robot Precision The precision of robot movement is defined by three basic features; a) Spatial resolution b) Accuracy c) Repeatability

Spatial Resolution The spatial resolution of a robot is the smallest increment of movement into which the robot can divide its work volume. It depends on the system’s control resolution and the robot's mechanical inaccuracies.

Accuracy Accuracy can be defined as the ability of a robot to position its wrist end at a desired target point within its reach. In terms of control resolution, the accuracy can be defined as one-half of the control resolution.

Repeatability It is the ability of the robot to position the end effector to the previously positioned location.

Robotic Basic Movement The basic movements required for a desired motion of most industrial robots are: 1) Rotational movement: This enables the robot to place its arm in any direction on a horizontal plane. 2) Radial movement: This enables the robot to move its end-effector radially to reach distant points. 3) Vertical movement: This enables the robot to take its end-effector to different heights.

Robotic Joints A robot joint is a mechanism that permits relative movement between parts of a robot arm. The joints of a robot are designed to enable the robot to move its end-effector along a path from one position to another as desired The joints are classified as prismatic or revolute.

Prismatic joints Prismatic joints are also known as sliding as well as linear joints (L), the links are generally parallel to one another. In some cases, adjoining links are perpendicular but one link slides at the end of the other link. They are called prismatic because the cross section of the joint is considered as a generalized prism. They permit links to move in a linear relationship

Revolute joints Revolute joints permit only angular motion between links. Their variations include: - Rotational joint (R) - Twisting joint (T) - Revolving joint (V)

Rotational joint A rotational joint (R) is identified by its motion, rotation about an axis perpendicular to the adjoining links. Here, the lengths of adjoining links do not change but the relative position of the links with respect to one another changes as the rotation takes place

Twisting joint A twisting joint (T) is also a rotational joint, where the rotation takes place about an axis that is parallel to both adjoining links.

Revolving joint A revolving joint (V) is another rotational joint, where the rotation takes place about an axis that is parallel to one of the adjoining links. Usually, the links are aligned perpendicular to one another at this kind of joint. The rotation involves revolution of one link about another

Robot Classification Robots may be classified, based on: - physical configuration - control systems Classification Based on Physical Configuration: - Cartesian configuration - Cylindrical configuration - Polar configuration - Joint-arm configuration

Cartesian Configuration Robots with Cartesian configurations consist of links connected by linear joints (L). A Cartesian coordinate robot has three principal prismatic axes (X, Y and Z) that are at right angles to each other Cartesian coordinate robots with the horizontal member supported at both ends are sometimes called Gantry robots. They are often quite large. Gantry robots usually hang upside down. Like gantry cranes, they are suspended from an X or X/Y axis beam. Gantry robots are Cartesian robots (LLL).

Cylindrical Configuration Robots with cylindrical configuration have one rotary ( R) joint at the base and linear (L) joints succeeded to connect the links The robot arm in this configuration can be designated as TLL. The space in which this robot operates is cylindrical in shape, hence the name cylindrical configuration

Polar Configuration Polar robots have a work space of spherical shape. Generally, the arm is connected to the base with a twisting (T) joint and rotary (R) and linear (L) joints follow The designation of the arm for this configuration can be TRL or TRR. Robots with the designation TRL are also called spherical robots. Those with the designation TRR are also called articulated robots. An articulated robot more closely resembles the human arm

Joint-arm Configuration The jointed-arm is a combination of cylindrical and articulated configurations. The arm of the robot is connected to the base with a twisting joint. The links in the arm are connected by rotary joints. Many commercially available robots have this configuration