MIDDLE EAST TECHNICAL UNIVERSITYMechanical Engineering Department ME 445 Integrated Manufacturing Systems
Robotics Terminology Robot: An electromechanical device with multiple degrees-of-freedom(DOF) that is programmable to accomplish a variety of tasks. Industrial robot: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 theperformance of a variety of tasks”
Robotics Terminology Robotics: The science of robots. Humans working in this area are called roboticists.
Robotics Terminology DOF degrees-of-freedom: the number of independent motions a device can make. (Also called mobility) five degrees of freedom
Robotics Terminology Manipulator:Electromechanical device capable ofinteractingwith its environment. Anthropomorphic:Like human beings. ROBONAUT (ROBOtic astroNAUT), an anthropomorphic robot with two arms, two hands, a head, a torso, and a stabilizing leg.
Robotics Terminology End-effector:The tool, gripper, or other device mounted at the end ofa manipulator, for accomplishing useful tasks.
Robotics Terminology Workspace:The volume in space that a robot’s end-effectorcan reach,both in position and orientation. A cylindrical robots’ half workspace
Robotics Terminology Position:The translational (straight-line) location of something. Orientation:The rotational (angle) location of something. A robot’s orientation is measured by roll, pitch, and yawangles. Link:A rigid piece of material connecting joints in a robot. Joint:The device which allows relative motion betweentwo links in a robot. A robot joint
Robotics Terminology Kinematics:The study of motion without regard to forces. Dynamics:The study of motion with regard to forces. Actuator:Provides force for robot motion. Sensor:Reads variables in robot motion for use in control.
Robotics Terminology • Speed • The amount of distance per unit time at which the robot can move,usually specified in inches per second or meters per second. • The speed is usually specified at a specific loadorassuming that the robot is carrying a fixed weight. • Actual speed may vary dependingupon the weight carried by the robot. • Load Bearing Capacity • The maximum weight-carrying capacity of the robot. • Robots that carry large weights, but must still be preciseare expensive.
Robotics Terminology • Accuracy • The ability of a robot to go to the specified position without makinga mistake. • It is impossible to position a machine exactly. • Accuracy is therefore defined as the ability of the robot to positionitself to the desired location with the minimal error (usually 25 mm). • Repeatability • The ability of a robot to repeatedly position itself when asked toperform a task multiple times. • Accuracy is an absolute concept, repeatability is relative. • A robot that is repeatable may not be very accurate, visaversa.
350 B.C The Greek mathematician, Archytas builds a mechanical bird named "the Pigeon" that is propelled by steam. 322 B.C. TheGreekphilosopher Aristotle writes; “If every tool, when ordered, or even of its own accord, could do the work that befits it... then there would be no need either of apprentices for the master workers or of slaves for the lords.”... hinting how nice it would be to have a few robots around. 200 B.C. The Greek inventor and physicist Ctesibus of Alexandria designs water clocks that have movable figures on them. Robotics History
Robotics History 1495 Leonardo DaVinci designs a mechanical device that looks like an armored knight. The mechanisms inside "Leonardo's robot" are designed to make the knight move as if there was a real person inside.
Robotics History Leonardo’s Robot
Robotics History 1738 Jacques de Vaucanson begins building automata. The first one was the flute player that could play twelve songs. 1770 Swiss clock maker and inventor of the modern wristwatch Pierre Jaquet-Droz start making automata for European royalty. He create three doll, one can write, another plays music, and the third draws pictures. 1801 Joseph Jacquard builds an automated loom that is controlled with punched cards.
Robotics History Joseph Jacquard’s Automated Loom
Robotics History 1898 Nikola Tesla builds and demonstrates a remote controlled robot boat.
Robotics History 1921 Czech writer Karel Capek introduced the word "Robot" in his play "R.U.R" (Rossuum's Universal Robots). "Robot" in Czech comes from the word "robota", meaning "compulsory labor“. 1940 Issac Asimov produces a series of short stories about robots starting with "A Strange Playfellow" (later renamed "Robbie") for Super Science Stories magazine. The story is about a robot and its affection for a child that it is bound to protect. Over the next 10 years he produces more stories about robots that are eventually recompiled into the volume "I, Robot" in 1950.Issac Asimov's most important contribution to the history of the robot is the creation of his “Three Laws of Robotics”.
Robotics History • Three Laws of Robotics: • A robot may not injure a human being, or, through inaction, allow a human being to come to harm. • A robot must obey the orders given it by human beings except where such orders would conflict with the First Law. • A robot must protect its own existence as long as such protection does not conflict with the First or Second Law. • Asimov later adds a "zeroth law" to the list: • Zeroth law: A robot may not injure humanity, or, through inaction, allow humanity to come to harm.
Robotics History 1946 George Devol patents a playback device for controlling machines. 1961 Heinrich Ernst develops the MH-1, a computer operated mechanical hand at MIT. 1961 Unimate, the company of Joseph Engleberger and George Devoe, built the first industrial robot, the PUMA (Programmable Universal Manipulator Arm). 1966 The Stanford Research Institute creates Shakey the first mobile robot to know and react to its own actions.
Robotics History Unimate PUMA SRI Shakey
Robotics History 1969 Victor Scheinman creates the Stanford Arm. The arm's design becomes a standard and is still influencing the design of robot arms today.
Robotics History 1976 Shigeo Hirose designs the Soft Gripper at the Tokyo Institute of Technology. It is designed to wrap around an object in snake like fashion. 1981 Takeo Kanade builds the direct drive arm. It is the first to have motors installed directly into the joints of the arm. This change makes it faster and much more accurate than previous robotic arms. 1989 A walking robot named Genghis is unveiled by the Mobile Robots Group at MIT.
Robotics History 1993 Dante an 8-legged walking robot developed at Carnegie Mellon University descends into Mt. Erebrus, Antarctica. Its mission is to collect data from a harsh environment similar to what we might find on another planet. 1994 Dante II, a more robust version of Dante I, descends into the crater of Alaskan volcano Mt. Spurr. The mission is considered a success.
Robotics History 1996 Honda debuts the P3.
Robotics History 1997 The Pathfinder Mission lands on Mars 1999 SONY releases the AIBO robotic pet.
Robotics History 2000 Honda debuts new humanoid robot ASIMO.
Power Sources for Robots • An important element of a robot is the drive system. The drive system supplies the power, which enable the robot to move. • The dynamic performance of a robot mainly depends on the type of power source.
There are basically three types of power sources for robots: 1. Hydraulic drive • Provide fast movements • Preferred for moving heavy parts • Preferred to be used in explosive environments • Occupy large space area • There is a danger of oil leak to the shop floor
2. Electric drive • Slower movement compare to the hydraulic robots • 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
3. 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
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:
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.
2.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.
3. 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.
4. 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. • 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.
The Hand of a Robot: End-Effector 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
The Hand of a Robot: End-Effector At times, 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 and Precision 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.
Robot Movement and Precision 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.
The precision of robot movement is defined by three basic features: • 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.
2. 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. This definition of accuracy applies in the worst case when the target point is between two control points.The reason is that displacements smaller than one basic control resolution unit (BCRU) can be neither programmed nor measured and, on average, they account for one-half BCRU.
The accuracy of a robot is affected by many factors. For example, when the arm is fully stretched out, the mechanical inaccuracies tend to be larger because the loads tend to cause deflection.
3. Repeatability: It is the ability of the robot to position the end effector to the previously positioned location.
The 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.