Robot Anatomy And Motion Analysis.pptx

Fundamentals of Robotics and Applications
Department of Robotics & Automation
JSS Academy of Technical Education, Bangalore-560060
(Course Code: BRA301)

Books
• S.R. Deb, Robotics Technology and flexible automation, Tata McGraw-Hill Education, 2009.
• Mikell P. Groover et al., "Industrial Robots - Technology, Programming and Applications", McGraw
Hill, Special Edition, (2012).
• Ganesh S Hegde, “A textbook on Industrial Robotics”, University Science Press, 3rd edition,
2017.
Reference
• Richard D Klafter, Thomas A Chmielewski, Michael Negin, "Robotics Engineering – An Integrated
Approach", Eastern Economy Edition, Prentice Hall of India Pvt. Ltd., 2006.
• Fu K S, Gonzalez R C, Lee C.S.G, "Robotics: Control, Sensing, Vision and Intelligence", McGraw
Hill, 1987.
Further Learning
https://www.robots.com/applications

Course Learning Objectives (CLO)
• Understand the fundamental/elementary concepts of Robotics.
• Provide insight into different types of robots.
• Explain the intelligent module for robotic motion control.
• Educate on various path-planning techniques.
• Illustrate the working of innovative robotic devices.

Course outcomes (COs) (Course Skill Set)
CO2: Identify and describe the components and anatomy of the robotic system.
At the end of the course, students will be able to,

Continuous Internal Evaluation (CIE)
• Assignment Component = 25 Marks
• Internal Assessment (IA) component = 25 Marks
• Two IA Tests, each of 25 Marks
• Two assignments each of 25 Marks
• For the course, CIE marks will be based on a scaled-down sum of two tests and other
assessment methods.
The minimum passing mark for the CIE is 40% of the maximum marks (20 marks out of 50)

Semester End Examination(SEE)
• The question paper shall be set for 100 marks.
• The duration of SEE is 03 hours.
• The question paper will have 10 questions.
• 2 questions per module. Each question is set for 20 marks.
• The students have to answer 5 full questions, selecting one full question from each module.
• The student has to answer for 100 marks and marks scored out of 100 shall be
proportionally reduced to 50 marks.
• SEE minimum passing mark is 35% of the maximum marks (18 out of 50 marks).
• Students should secure a minimum of 40% (40 marks out of 100) in the sum total of the CIE and SEE
taken together.

Fundamentals of Robotics & Applications
MODULE 2: Robot Anatomy And Motion Analysis

MODULE 2: Robot Anatomy And Motion Analysis
• Anatomy of a Robot, Robot configurations: polar, cylindrical, Cartesian, and jointed arm
configurations.
• Robot links and joints, Degrees of freedom: types of movements, vertical, radial and
rotational traverse, roll, pitch and yaw, Work volume/envelope,
• Robot kinematics: Introduction to direct and inverse kinematics, transformations and rotation
matrix
Content

• Robot anatomy is concerned with the physical construction of the body,
arm and wrist
• Most robots used in plants are mounted on a base and fastened to the
floor.
• The body is attached to the base, and the arm assembly is attached to the
body.
• At the end of the arm, carries the wrist.
• Wrist allows it to be oriented in a variety of positions.
• Relative movements between the links are provided by a series of joints
• The robot’s wrist receives a hand or a tool called the “end effector
• The end effector is not considered as part of the robot’s anatomy
Anatomy of a Robot

Physical configuration
Robot Configurations
Today’s commercially available robots possess four basic configurations;
1. Polar Configuration
2. Cylindrical configuration
3. Cartesian coordinate configuration
4. Jointed arm robots

1. Polar / Spherical Configuration (P2R)
• This combination allows the robot to operate in a spherical
work volume.
The robot arm has following movements.
1. Linear movement: allows the arm to extend and retract
because of one linear joint.
2. Rotary movement: occurs around an axis (vertical)
perpendicular to the base because of one twisting joint.
3. Vertical lift of the arm about the pivot point because of one
rotational joint.

Advantages
• Long reach capabilities in horizontal position
• Good lifting capabilities
• Suitable for small amount of vertical applications
Applications: Machine loading, Material movement, stacking of components, Heat treatment operations
Limitations
• Low vertical reach
• Reduced mechanical rigidity
Ref: https://electricalworkbook.com/polar-robot/

Workspace of robot / Work volume Geometry of robot major axis

2. Cylindrical Configuration (PRP / 2PR)
• This combination allows the robot to reach work space in a
rotary movement like a cylinder
1. Rotational movement: of the column about its axis because
of one twisting joint
2. Linear movement: of the assembly along the column because
of one linear joint
3. Linear movement in and out, relative to the column axis
because of one orthogonal jointworkspace

Advantages
• Higher load carrying capacity
• Provides high rigidity to the manipulator
• Suitable for pick and place applications
Applications: Conveyor pallet transfer, machine tool loading, forging , packing, precision small assembly etc.
Limitations
• Require more floor space
• Reduced mechanical rigidity because rotary axis
must overcome inertia of the object when rotating
Ref: https://electricalworkbook.com/cylindrical-robot/
Workspace of robot / Work volume
Geometry of robot major axis
2. Cylindrical Configuration (PRP / 2PR)

3. Cartesian Coordinate Configuration
• Also referred as Rectilinear robot or X-Y-Z robot of the
spherical configuration, as it is equipped wit three sliding joints.
1. Linear movement: allows vertical lift to the arm because of
one linear joint.
2. Two sliding movement: perpendicular to each other because
of two orthogonal joint.
This configuration robot process in a rectangular workspace by
three joints movement.

Advantages
• Higher load carrying capacity
• Rigid structure, high degree of mechanical rigidity and accuracy
• High repeatability with least error at good speed.
Applications: Inspection, assembly, machining operations, welding, finishing
operations etc.
Limitations
• Has small and rectangular work envelope
• Has reduced flexibility
Ref: https://electricalworkbook.com/cartesian-robot/

4. Jointed arm Configuration
• Resembles to a human arm
1. Rotary movement: (vertical column that swivels about base)
occurs around an axis (horizontal) parallel to the base
because of twisting joint.
2. Rotary movement: at the top of the column about the shoulder
joint (along the horizontal axis) because of one rotational joint.
3. Rotary movement at the output arm about the elbow joint
(along horizontal axis) because of one rotational joint.
• It has 3 rotary joints and 3 wrist axes which form 6 DOF.

Advantages
• Huge work volume
• Higher flexibility and quick in operation
• 2 rotational joints allows for higher reach from the base
• Provides reaching congested small opening without restrictions
Applications: spray painting, spot welding, arc welding etc.
Limitations
• Difficult operation procedure
• Plenty of components
Ref: https://electricalworkbook.com/jointed-arm-robot/
4. Jointed arm Configuration

Cartesian Cylindrical
Polar / spherical

Robot links and Joints
• A robotic manipulator's two adjacent joint axes are connected, defined by a rigid body called a link.
• The link maintains a fixed relationship between the two joint axes through a kinematic function.
ROBOT LINKS

ROBOT LINKS
• Consider the i-th link in the kinematic chain.
• This link connects two joints.
• At the end of link i, there is an axis with respect to which the following link, i+1, is going to move.
• There is also an axis at the beginning of link i.
• Those two axes are lines in a three dimensional space.
• They are characterized by a common normal.
• This common normal has a length that is called link length.
ai−1 (the link length) denotes the length along the common normal from
axis i−1 to axis i.

ROBOT LINKS
• To define the relative position between two axes in space, in
addition to the common normal, the angle between the axes
needs to be computed.
• Draw a parallel line to axis i at the point where the common
normal intersects the axis i−1.
• The angle between this parallel line and axis i−1, denoted by
αi−1, will be called a link twist.
• This angle is measured in the right-hand sense about the
vector defined by ai−1 directed from axis i−1 to axis i along the
common normal.

ROBOT LINKS

ROBOT JOINTS
• The Robot Joints are an essential element in a robot that helps the links travel in different movements.
• In a robot, the connection of different manipulator joints is called Robot Links.
• The integration of two or more links is called a Robot Joint.
The five major types of joints such as:
1. Rotational joint
2. Linear joint
3. Twisting joint
4. Orthogonal joint
5. Revolving joint

ROBOT JOINTS
• A rotational joint can also be represented as R – Joint.
• This type will allow the joints to move in a rotary motion along
the axis, which is vertical to the arm axes.
1. Rotational Joint (R)
• Linear joint can be indicated by the letter L – Joint.
• This type of joint can perform both translational and sliding
movements.
• These motions will be attained in several ways such as
telescoping mechanism and piston.
• The two links should be in parallel axes to achieve linear
movement.
2. Linear Joint (L)

ROBOT JOINTS
• Twisting joint will be referred to as V – Joint.
• This joint makes a twisting motion between the output and input link.
• During this process, the output link axis will be vertical to the rotational axis.
• The output link rotates about the input link.
3. Twisting Joint (T)
• Orthogonal joint is denoted by O
• Similar to the linear joint.
• The only difference is that the output and input links will move
at the right angles.
4. Orthogonal Joint (O)

ROBOT JOINTS
• Revolving joint is generally known as V Joint.
• The output link axis is perpendicular to the rotational axis,
• The input link is parallel to the rotational axes.
• Similar to a twisting joint, the output link spins about the input link.
5. Revolving Joint (V)

ROBOT JOINTS
Notation scheme for Designating the robots
Joint Notation Scheme
• Considering the arm and body joints, the letters can be used to designate the particular robot configuration.
• Start with the joint closest to the base and proceed to the joint that connects to the wrist.
• Typical notations for the four basic configurations are summarized in the table

ROBOT MOTIONS
• Industrial robots are designed to perform productive work such as pick and place, welding, assembly, etc.
• To accomplish the work, the robot has to move its body, arm and wrist through a series of motions and
positions.
• The individual joint motions associated with the performance of a task are referred to by the term DOF
• Industrial robot will have 4 – 6 DOF
• Opening and closing of the gripper is not considered DOF
• Three joints are normally associated with the action of the arm and body.
• Two or three joints are used to actuate the wrist

DOF (Degrees of Freedom)
• A body in 3D space can have 6 DOF (3 are Rotary & 3 are translatory).
• 6 DOF are positive & 6 DOF are negative.
• 3 DOF are translatory along +ve axis & 3 DOF are along –ve axis.
• The number of independent motions in which the end effector can move is defined by
the number of axes of motion of the manipulator.
ROBOT MOTIONS

• The more DOF, the greater the complexity of motions encountered.
• For applications that require more flexibility, additional degrees of freedom are used in the wrist of the robot.
• Three degrees of freedom located in the wrist give the end effector all the flexibility.
ROBOT MOTIONS

1. The rotational traverse: rotation of the arm about the vertical axis,
such as the left-and-right swivel of the robot’s arm on a base.
2. The radial traverse involves extension or retraction (In or Out) of
the arm from the vertical centre of the robot (Base)
For polar, cylindrical or jointed arm configuration, the 3 DOF associated with arm and body motions are
3 DOF associated with the arm and body of a polar coordinate robot.

The vertical traverse: Capability to move the wrist up or down to provide the desired vertical attitude
3 DOF associated with the arm and body of a polar coordinate robot.

1. The rotational traverse
2. The radial traverse
3. The vertical traverse

ROBOT MOTIONS
• The wrist movement is designed to enable the robot to orient the end effector properly with respect to the task
being performed, such as welding, painting, grasping, etc.
• To overcome/solve this problem, normally the wrist is provided with up to 3 DOF (configuration)
1. Wrist Roll / Wrist swivel
2. Wrist Pitch / Wrist bend
3. Wrist Yaw
Three degrees of freedom associated with the robot wrist

ROBOT MOTIONS
The 3 DOF located in the wrist of a robotic system:
1. Pitch: Bend or up and down movement.
2. Yaw: Right and left movement.
3. Roll: Swivel or rotation of the wrist/hand.

ROBOT MOTIONS
PUMA (Programmable Universal Machine for Assembly, or Programmable Universal Manipulation Arm)
PUMA robot having six degrees of freedom

Work Volume
• Work volume refers to the space within which the robot can manipulate its wrist end.
• The extreme position of the robot axes describes a boundary for the region in which the robot operated.
• The end effector is an addition to the basic and should not be counted as part of the robot’s working space.
The following physical characteristics determine the work volume.
1. The robot’s physical configuration (type of Joint, structure of links)
2. The size of the body, arm and wrist components
3. The limits of the robot’s joint movements.

Work volumes for different types of robots: (a) Polar (b) Cylindrical (c) Cartesian
Work Volume

Robot Kinematics: Forward and Inverse Kinematics

• Kinematics is the study of motion without considering the forces/efforts that affect the motion
• The kinematics of a robot manipulator describes the relationship between the motion of the
joints of the manipulator and the resulting motion of the rigid bodies (links) that form the
robot

What is Forward Kinematics?
• Forward Kinematics is the calculation of the position and
orientation of an end effector using the variables of the
joints and linkages connecting to the end effector.
• Given the current positions, angles, and orientation of
the joints and linkages, forward kinematics can be used
to calculate the position and orientation of the end
effector.

What is Inverse Kinematics?
• Inverse Kinematics is the calculation of the variables of the
set of joints and linkages connected to an end effector.
• Given the position and orientation of the end effector,
inverse kinematics can be used to calculate the variables
regarding those joints and linkages including position,
angle, and orientation.

Direct ( Forward) Kinematics (FK / DK)
• Given: Joint angles and links geometry
• Compute: Position and orientation of the end effector relative to the base frame
Forward Kinematics
• Given: Position and orientation of the end effector relative to the base frame
• Compute: All possible sets of joint angles and links geometry that could give the position and
orientation of the end effector
Inverse Kinematics (IK)

TRANSFORMATIONS AND ROTATION MATRIX
Transformations
• To describe the position and orientation of the tool with respect to the base frame.
• It is necessary to know and formulate the body coordinate frame along the joint axis for each links in
the manipulator of the robot.
• The relation between the body frame with the base frame of reference is described by transformation
matrix.
• The transformation matrix is represented by the following component transformation
1. Rotation matrix
2. Translation or position vector
3. Perspective transformation
4. Scaling or stretching

Transformations
• The transformation matrix is a 4 x 4 matrix which consists of 4 sub matrix as shown below

Transformations
• In study of robotics we represents position and rotation (Orientation) as follows

Transformations
Concept of Projection
Rotation matrix

Transformations
• We are looking at rotation of one frame inside another frame.
• We have 3 vectors rotating together x, y & z
• Consider frame 0 and frame 1 as shown in fig.
• In this, frame 1 is aligned with frame 0 exactly.
Rotation matrix

Transformations
How to represent the rotation of frame 1 inside the frame 0 as shown in fig.
Represent the rotation matrix, indicates the rotation of frame 1 inside / relative the frame 0
Rotation matrix

Transformations
In a coordinate frame, each of the axes have a length of 1
Rotation matrix

Transformations
Rotation about X
Rotation about Y
Rotation about Z
Rotation matrix

Transformations
• Not all the rotation consists of just rotation about x, y & z
• Consider one frame rotated about another frame as shown in fig.
• This rotation is a combination of other rotation
• How to write rotation matrix for such arbitrary rotation like this?
Frame 1 is rotated about 45º around Z rotated about 45º around x-axis
Rotation matrix

Frame 1 is rotated about 45º around Z rotated about 45º around x-axis
Rotation matrix
Standard rotation matrix about z x Rotation about x
Rotation of x1, y1 & z1 about the X0, Y0 & Z0

Rotation Matrix
GEOMETRIC INTERPRETATION OF ROTATION MATRIX

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