Robotics Terminology

WELCOME TO ALL

Department of Engineering Sciences and Humanities (DESH) at Vishwakarma Institute of Technology
Focus: First Year - Department of Engineering Sciences and Humanities

ROBOTICS: TERMINOLOGY

Department of Engineering Sciences and Humanities (DESH) at Vishwakarma Institute of Technology
Focus: First Year - Department of Engineering Sciences and Humanities
Lectures 2 & 3

KEY POINTS OF DISCUSSION

This section outlines important concepts related to robotics, which include:

  • Robot Terminology: Analogy with the human body, examining how robotic components correspond to human anatomy.

  • Kinematics: Discussion on Degrees of Freedom, Robot coordinates, Roll-Pitch-Yaw, Workspace, Linkages, Reference frames, Forward and Inverse kinematics.

  • Introduction to Transformation Matrix: Basic introduction to transformation matrices used in kinematic analysis.

KINEMATICS

Kinematic Link

A kinematic link is defined as a rigid body or an assembly of rigid bodies in a machine that has relative motion concerning other connected parts.

Types of Links

Three types of links are used to transmit motion:

  1. Rigid Link:

    • A link that does not undergo any deformation while transmitting motion.

    • Practical examples include crank shafts, pistons, and connecting rods.

  2. Flexible Link:

    • A link that undergoes partial deformation without affecting the transfer of motion.

    • Examples include ropes, belts, chains, and springs.

  3. Fluid Link:

    • A link which consists of a fluid contained within a reservoir, where motion is transmitted through changes in pressure or compression.

    • Examples include fluids utilized in hydraulic presses and jacks.

KINEMATIC PAIRS

Definition

A kinematic pair is the joint of two links or elements of a machine that possess relative motion between them.

Example: Slider Crank Mechanism

In a slider crank mechanism:

  • Link 2 rotates relative to Link 1, forming a turning pair.

  • Additionally, the pairs formed by Links 2 & 3 and Links 3 & 4 also constitute turning pairs.

  • Link 4 acts as a slider that reciprocates relative to Link 1, forming a sliding pair.

CLASSIFICATION OF KINEMATIC PAIRS

Kinematic pairs can be classified based on the nature of contact between the surfaces:

  1. Lower Pair:

    • Formed when there is surface or area contact between the links.

    • Examples include sliding pairs, turning pairs, and screw pairs.

    • Common instances: Shaft rotating in bearing and universal joints.

  2. Higher Pair:

    • Characterized by point or line contact between the moving parts.

    • Includes cam-follower pairs and other similar devices.

DEGREES OF FREEDOM

Definition

The degree of freedom (DOF) of a pair is defined as the number of independent relative motions available, whether translational or rotational.

  • The formula to determine DOF is given by:
    DOF = 6 - ext{Number of Restraints}
    Unconstrained rigid bodies moving in space can achieve the following independent motions:

  • Translational motions along the x, y, and z directions.

  • Rotational motions about the three axes.

  • Thus, a rigid body in space has six degrees of freedom (DOFs).

Restraint Definition

Restraint refers to any limitation placed on the movement or motion of an object.

ANATOMY OF A ROBOT

The mechanical structure of a robotic manipulator is composed of various components:

  • Base Link: The stationary part typically fastened to a fixed surface or mobile platform.

  • Links (Arms): Segmented assemblies made up of rigid bodies connected by joints.

    • Arm 1 and Arm 2 ensure mobility and reachability for the manipulator.

  • Joints (Joint 1 and Joint 2): Allow relative motion between links, pivotal for operating the robotic system.

  • Wrist: Allows the orientation of the end effector.

  • End Effector: The component that performs the required tasks, such as a gripper.

ROBOT TERMINOLOGY

Analogy Between Human Body and Robots

The study of a robot's anatomy draws parallels with human anatomy:

  • Links are likened to bones.

  • Joints correspond to joints in the human body.

  • Sensors are analogous to sensory organs.

  • Actuators represent muscles.

  • Wires can be compared to nerves.

BASIC COMPONENTS OF ROBOTS

Key components of robots generally involve:

  • End Effectors: These can be of various types:

    • Mechanical (e.g., grippers)

    • Vacuum (for lifting with suction)

    • Magnetic (using magnetic fields to attract objects)

  • Tools: Examples include welding guns, spray paint guns, drilling spindles, screwdrivers, and heating torches.

FUNCTIONS OF A ROBOT

The fundamental functions of a robot include:

  1. Sensing:

    • Utilizing external sensors to perceive the environment (vision, voice, touch, proximity, etc.).

  2. Decision Making:

    • Making informed decisions based on sensor data.

  3. Performing Tasks:

    • Executing actions as per received commands through actuators.

ROBOT TERMINOLOGY: ACTUATORS

Actuators serve as the robot’s artificial muscles. They can be categorized into:

  1. Electric Motors: Predominantly used for various applications.

  2. Pneumatic Cylinders:

    • Found in smaller robots for fast operations at low power.

  3. Hydraulic Cylinders:

    • Utilized in larger robots due to their ability to deliver high power, albeit with slower operations.

ROBOT TERMINOLOGY: SENSORS

Sensors help robots understand and interact with their environment. Common types include:

  • Proximity Sensors: Identify nearness of objects.

  • Tactile Sensors: Sense touch or pressure.

  • Current Sensors: Measure the current flowing through a circuit.

  • Tilt Sensors: Identify inclination.

  • Gyroscope: Measures orientation or angular velocity.

  • Encoders: Provide the speed of motors.

  • Hall Effect Sensors: Detect magnetic fields.

  • Temperature Sensors: Monitor environmental temperature.

  • Acceleration Sensors and Image Sensors: Including cameras to interpret visual data.

PROGRAMMING INTERFACE

Robots may use various programming languages and interfaces to perform tasks:

  • Embedded C

  • Python

  • MATLAB: Provided by MathWorks.

  • RobotC: Used with LEGO robotics.

  • KRL: KUKA Robotics Language.

  • KAREL: Used by Fanuc robots.

TERMINOLOGY OF A ROBOT

  • Repeatability: The ability of a robot to perform the same task consistently with the same accuracy and precision.

  • Precision: The measure of how closely a series of measurements or task completions are to each other.

  • Accuracy: Refers to how close a robot's output is to the programmed target.

COMPARISON OF ACCURACY AND PRECISION

The comparison can be illustrated as follows:

  • Very Low Accuracy and Very Low Precision

  • Good Accuracy but Low Precision

  • Low Accuracy but High Precision

  • High Accuracy and High Precision

Resolution

Resolution is defined as the smallest movement or measurement that a robot can achieve. It reflects the capability of the robot to exhibit fine details in its operations, where pixel stands for Picture Element.

THANK YOU!

This concludes the notes from the modules discussed in the Robotic Terminology lectures at the Vishwakarma Institute of Technology.