Robotics & Vision Analysis, systems, Applications

"I can't define a robot, but I know one when I see one." What is a robot? Joseph Engelberger, a pioneer in industrial robotics: "I can't define a robot, but I know one when I see one."

Arkin (1998) “An intelligent robot is a machine able to extract information from its environment and use knowledge about its world to move safely in a meaningful and purposive manner”

What is Robotics? Robotics is the art, knowledge base, and the know-how of designing, applying, and using robots in human endeavors. Robotics is an interdisciplinary subject that benefits from mechanical engineering, electrical and electronic engineering, computer science, biology, …..

What is a Robot ? Random House Dictionary A machine that resembles a human being and does mechanical routine tasks on command. Robotics Association of America An industrial robot is a re-programmable, multifunctional manipulator designed to move materials, parts, tools, or specialized devices through variable programmed motions for the performance of a variety of tasks.

What are Robots? To qualify as a robot, a machine must be able to: Machines with sensing, intelligence and mobility To qualify as a robot, a machine must be able to: 1) Sensing and perception: get information from its surroundings 2) Carry out different tasks: Locomotion or manipulation, do something physical–such as move or manipulate objects 3) Re-programmable: can do different things 4) Function autonomously and/or interact with human beings

Classification of Robots - JIRA (Japanese Industrial Robot Association) Class1: Manual-Handling Device Class2: Fixed Sequence Robot Class3: Variable Sequence Robot Class4: Playback Robot Class5: Numerical Control Robot Class6: Intelligent Robot

Classification of Robots - RIA (Robotics Institute of America) Variable Sequence Robot(Class3) Playback Robot(Class4) Numerical Control Robot(Class5) Intelligent Robot(Class6)

Classification of Robots AFR (Association FranÇaise de Robotique) Type A: Manual Handling Devices/ telerobotics Type B: Automatic Handling Devices/ predetermined cycles Type C: Programmable, Servo controlled robot, continuous point-to-point trajectories Type D: Same type with C, but it can acquire information.

Position: The translational (straight-line) location of something. Robotics Terminology Position: The translational (straight-line) location of something. Orientation: The rotational (angle) location of something. Link: A rigid piece of material connecting joints in a robot.

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.

Robotics Terminology Manipulator: Electromechanical device capable of interacting with its environment. Anthropomorphic: Like human beings.

Robot Anatomy Manipulator consists of joints and links Joints provide relative motion Links are rigid members between joints Each joint provides a “degree-of-freedom” Base Link0 Joint1 Link2 Link3 Joint3 End of Arm Link1 Joint2

Robotics Terminology Workspace: The volume in space that a robot’s end-effector can reach, both in position and orientation.

Robotics Terminology End-effector: The tool, gripper, or other device mounted at the end of a manipulator, for accomplishing useful tasks. 2004

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 The speed is usually specified at a specific load or assuming that the robot is carrying a fixed weight. Load Bearing Capacity The maximum weight-carrying capacity of the robot.

Robotics Terminology Accuracy The ability of a robot to go to the specified position without making a mistake. Accuracy is therefore defined as the ability of the robot to position itself to the desired location with the minimal error (usually 25 mm). Repeatability The ability of a robot to repeatedly position itself when asked to perform a task multiple times.

What is a Robot ? A robot is composed of a series of links connected to each other via joints. Each joint usually has an actuator (a motor for eg.) connected to it. These actuators are used to cause relative motion between successive links. One end of the manipulator is usually connected to a stable base and the other end is used to deploy a tool.

Manipulator Joints Translational motion Rotary motion Linear joint (type L) Orthogonal joint (type O) Rotary motion Rotational joint (type R) Twisting joint (type T) Revolving joint (type V)

The Robotic Joints 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.

The Robotic Joints Prismatic joints (L) are also known as sliding as well as linear joints. 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.

The Robotic Joints 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.

The Robotic Joints 2004

The Robotic Joints A twisting joint (T) is also a rotational joint, where the rotation takes place about an axis that is parallel to both adjoining links. 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 Coordinates Fig. 1.4  Cartesian/rectangular/gantry (3P) : 3 cylinders joint  Cylindrical (R2P) : 2 Prismatic joint and 1 revolute joint  Spherical (2RP) : 1 Prismatic joint and 2 revolute joint  Articulated/anthropomorphic (3R) : All revolute(Human arm)  Selective Compliance Assembly Robot Arm (SCARA): 2 paralleled revolute joint and 1 additional prismatic joint

Robot Workspace Fig. 1.7 Typical workspaces for common robot configurations

ROBOT CLASSIFICATION Cylindrical Configuration: Robots with cylindrical configuration have one rotary ( R) joint at the base and linear (L) joints succeeded to connect the links. 2004

ROBOT CLASSIFICATION 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 rotatory (R) and linear (L) joints follow. 2004

ROBOT CLASSIFICATION 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. 2004

TRL notation 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)

Cylindrical Body-and-Arm Assembly Notation 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

Cartesian Coordinate Body-and-Arm Assembly Notation LOO: Consists of three sliding joints, two of which are orthogonal Other names include rectilinear robot and x-y-z robot

Jointed-Arm Robot Notation TRR:

SCARA Robot Notation VRO 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

Wrist Configurations:RRT End effector is attached to wrist assembly Function of wrist assembly is to orient end effector Body-and-arm determines global position of end effector Two or three degrees of freedom: Roll Pitch Yaw

Example Sketch following manipulator configurations (a) TRT:R, (b) TVR:TR, (c) RR:T. Solution:

Robotics Terminology DOF degrees-of-freedom: the number of independent motions a device can make. (Also called mobility) five degrees of freedom

Robots degrees of freedom Degrees of Freedom: Number of independent position variables which would has to be specified to locate all parts of a mechanism. In most manipulators this is usually the number of joints.

The Robotic Joints These degrees of freedom, independently or in combination with others, define the complete motion of the end-effector. These motions are accomplished by movements of individual joints of the robot arm. The joint movements are basically the same as relative motion of adjoining links. Depending on the nature of this relative motion, the joints are classified as prismatic or revolute.

DOF of a Rigid Body In a plane In space

Degrees of Freedom 3 position 3D Space = 6 DOF 3 orientation In robotics: DOF = number of independently driven joints positioning accuracy As DOF computational complexity cost flexibility power transmission is more difficult

Degrees of Freedom Degree of freedom - one joint one degree of freedom Simple robots - 3 degrees of freedom in X,Y,Z axis Modern robot arms have up to 7 degrees of freedom XYZ, Roll, Pitch and Yaw The human arm can be used to demonstrate the degrees of freedom. Crust Crawler- 5 degrees of freedom

Robot Joints Revolute Joint 1 DOF ( Variable - q) Spherical Joint Due to mechanical design considerations manipulators are generally constructed from joints which exhibit just one degree of freedom. Most manipulators have revolute joints or have sliding joints. In the rare case that a mechanism is built with a joint having n degrees of freedom it can be modeled as n joints of one degree of freedom connected with n-1 links of zero length. Spherical Joint 3 DOF ( Variables - q 1, q 2, q 3) Prismatic Joint 1 DOF (linear) (Variables - d)

Link Link n q n+1 a n q n Joint n+1 Joint n z n x n x n+1 z n+1 A link is considered as a rigid body which defines the relationship between two neighboring joint axes of a manipulator.

Link Length and Twist Axis i Axis i-1 ai-1 i-1 The distance between two axes in 3-space is measured along a line which is mutually perpendicular to both axes. Link twist: If we imagine a plane whose normal is the mutually perpendicular line just constructed, we can project both axes I-1, I onto this plane and measure the angle between them. The angle is measured from i-1 to I by Right-Hand-Rule about the common normal. Note: If the axes intersect, then a is zero, and  is still measured from axis i-1 to axis i.

Link and Joint Parameters Axis i-1 Axis i ai di i For kinematical studies we only need two more quantities to completely define the relative position of two neighboring links. The Distance between the two common normals “di” at joint-i. This distance is called the “Link-Offset” (. Angle of rotation about their common axis-i, between one link and its neighbor, “i”. This angleis called the “Joint-Angle” (“i” is the angle between ai-1 and ai about axis-i). ai-1 i-1

Affixing Frames to Links Link n-1 Link n zn-1 yn-1 xn-1 zn xn yn zn+1 xn+1 yn+1 dn an Joint n+1 Joint n-1 Joint n an-1 In the case of ai=0 Xi is normal to plane of Zi and Zi+1 This convention does not result in a unique attachment of frames to links…

Example: Puma 560