Unit 1: Introduction to Robotics and Robot Anatomy

I. Foundations of Robotics

Robotics is the interdisciplinary field concerned with designing, constructing, programming, sensing, controlling, and applying robots. A robot is a reprogrammable physical machine that senses its environment, processes information, and performs actions with some degree of autonomy.

• Governing principle: A robotic system operates through a repeated sense–plan–act cycle:
  • Sense: Acquire data using encoders, cameras, force sensors, or other devices.
  • Plan: Interpret data and determine motion or action through a controller.
  • Act: Use actuators to move joints, tools, wheels, or other mechanisms.
• Reprogrammability: Changing software, task data, or tooling allows one robot to perform different operations.
• Embodiment: Unlike purely digital automation, a robot interacts physically with its environment.
• Autonomy: Robots range from directly teleoperated machines to systems that independently perceive, plan, and act.
• Interdisciplinary basis: Robotics combines mechanical engineering, electronics, control theory, computer science, artificial intelligence, and human factors.
• Core performance measures:
  • Accuracy: Closeness of the achieved position to the commanded position.
  • Repeatability: Ability to return consistently to the same position.
  • Payload: Maximum load safely handled, commonly measured in kilograms.
  • Speed: Joint speed, linear speed, or cycle time.
  • Resolution: Smallest detectable or commandable change in position.

II. Development and Classification — Origins and Major Robot Categories

A. Evolution of robotics

The evolution of robotics reflects the progression from mechanical automata to programmable, sensor-rich, and increasingly autonomous machines.

• Early automata: Ancient and medieval water-, weight-, and clockwork-driven figures demonstrated predetermined mechanical motion but lacked reprogrammability.
• Origin of “robot”: Czech writer Karel Čapek popularized the word in the play R.U.R. (1920); it derives from robota, associated with forced labour.
• Origin of “robotics”: Isaac Asimov used the term in the early 1940s in science-fiction writing about intelligent machines.
• Programmable industrial robotics: George Devol developed the programmable manipulation concept in the 1950s; the Unimate robot entered General Motors production in 1961 for material handling.
• Computer-controlled manipulators: Robots such as the Stanford Arm and PUMA helped establish electrically driven, multi-joint manipulation during the 1960s and 1970s.
• Sensor-based robotics: Machine vision, force sensing, and microprocessor control expanded welding, assembly, inspection, and adaptive handling in the 1980s and 1990s.
• Modern development: Twenty-first-century systems include collaborative robots, autonomous mobile robots, surgical robots, drones, warehouse robots, and AI-assisted service robots.
• Continuing trend: Development is moving from fixed, repetitive automation toward flexible operation in uncertain environments shared with humans.

B. Classification of robots

Robots are classified according to structure, mobility, control, application, and interaction with people.

• By mechanical configuration:
  • Cartesian, cylindrical, spherical, SCARA, articulated, and parallel robots differ in joint arrangement and workspace geometry.
• By mobility:
  • Fixed robots: Mounted on a base, as in an industrial welding arm.
  • Mobile robots: Travel using wheels, tracks, legs, propellers, or thrusters.
• By control level:
  • Teleoperated: Human commands motion remotely, as in some bomb-disposal robots.
  • Programmed: Executes stored trajectories or sequences.
  • Autonomous: Uses sensing and planning to select actions without continuous human control.
• By drive system:
  • Electric drives offer clean, precise control.
  • Hydraulic drives provide high force for heavy machinery.
  • Pneumatic drives provide rapid, simple motion for light loads.
• By application: Major groups include industrial, medical, agricultural, military, domestic, logistics, educational, and entertainment robots.
• By human interaction: Conventional industrial robots usually operate in safeguarded spaces, while collaborative applications use risk-reduction measures for closer human–robot operation.

III. Robotic Structure — Hardware and Mechanical Organization

A. Components of a robotic system

A complete robotic system integrates mechanical hardware, actuation, sensing, computation, power, and communication.

• Mechanical structure: Links, joints, frames, transmissions, and bearings support and guide motion.
• Actuators: Electric motors, hydraulic cylinders, or pneumatic cylinders convert energy into movement.
• Transmission: Gears, belts, chains, ball screws, and harmonic drives modify actuator speed, torque, or direction.
• Sensors:
  • Proprioceptive sensors measure internal state; encoders report joint angle in degrees or radians.
  • Exteroceptive sensors observe the environment; examples include cameras, lidar, ultrasonic sensors, and tactile arrays.
• Controller: A computer or programmable control unit processes commands, closes feedback loops, and coordinates joints.
• End effector: The tool attached to the final link performs the task, such as gripping, welding, painting, drilling, or inspection.
• Power supply: Electrical mains, batteries, hydraulic pumps, or compressed-air systems provide operating energy.
• Software and interface: Programs define trajectories and logic, while teach pendants, dashboards, or network interfaces allow supervision.
• Safety system: Emergency stops, guards, interlocks, safety scanners, and torque limits reduce hazardous motion.

B. Robot anatomy

Robot anatomy describes the physical arrangement of a robot’s supporting structure, arm, wrist, joints, and task tool.

• Base: Anchors a stationary robot or connects a manipulator to a mobile platform.
• Links: Rigid members form the robot’s mechanical skeleton; link length directly affects reach.
• Joints:
  • Revolute joint (R): Produces angular motion about an axis.
  • Prismatic joint (P): Produces linear motion along an axis.
• Body-and-arm assembly: Positions the wrist within the workspace through large-scale motions such as shoulder and elbow rotation.
• Wrist assembly: Orients the end effector, commonly through roll, pitch, and yaw rotations.
• End effector:
  • Grippers handle objects using fingers, suction cups, magnets, or adhesive surfaces.
  • Process tools perform operations such as arc welding, spraying, polishing, or cutting.
• Kinematic chain: A serial chain connects links end-to-end; a parallel chain connects the platform to the base through multiple branches.
• Joint variables: Robot posture is represented by a vector such as
  
  TEXT

    q = [q₁, q₂, …, qₙ]ᵀ

  
  where (q_i) is the displacement of joint (i), and (n) is the number of independently controlled joints.

IV. Robot Motion Geometry — Movement, Frames, and Reach

A. Degrees of freedom (DOF)

Degrees of freedom indicate the number of independent variables required to specify a robot’s configuration.

• Joint contribution: An ideal revolute or prismatic joint normally contributes one DOF.
• Serial manipulator mobility:
  
  TEXT

    M = Σ fᵢ

  
  where (M) is mobility and (f_i) is the independent motion provided by joint (i), assuming no additional closed-chain constraints.
• Rigid-body pose: A free body in three-dimensional space has six DOF—translations (x,y,z) and rotations roll, pitch, yaw.
• Manipulator requirement: A robot generally needs six independent DOF to place an end effector at an arbitrary reachable position and orientation.
• Redundancy: A manipulator with more DOF than required for a task can avoid obstacles, joint limits, or undesirable postures.
• Underactuation: A robot with fewer controlled DOF than task variables cannot independently achieve every desired pose.
• Constraint distinction: DOF describes independent motion, not simply the physical number of joints; closed-loop mechanisms may have many joints but low mobility.

B. Robot coordinate systems

Coordinate systems provide reference frames for describing robot position, orientation, velocity, and motion commands.

• World frame: A fixed global reference used to locate robots, fixtures, and objects in a workcell.
• Base frame: Attached to the robot base and used as the primary reference for manipulator kinematics.
• Joint coordinates: Express configuration using joint angles and linear displacements, such as (q=[\theta_1,\theta_2,d_3]^T).
• Tool frame: Attached to the end effector; its origin is often placed at the tool centre point.
• Object or user frame: Attached to a workpiece, conveyor, table, or other task feature for convenient programming.
• Cartesian pose: Position is represented by ((x,y,z)), while orientation may be represented by rotation matrices, Euler angles, or quaternions.
• Frame transformation:
  
  TEXT

    pᴬ = ᴬTᴮ pᴮ

  
  where (p^B) is a point expressed in frame (B), (p^A) is the same point in frame (A), and ({}^AT_B) is a homogeneous (4 \times 4) transformation containing rotation and translation.
• Programming significance: A motion commanded along tool-frame (z) follows the tool’s current direction, whereas motion along world-frame (z) follows the fixed global vertical axis.

C. Robot workspace

Robot workspace is the set of positions, or poses, that the end effector can reach.

• Reachable workspace: Contains points attainable in at least one end-effector orientation.
• Dexterous workspace: Contains points where all required orientations can be achieved; it is usually smaller than the reachable workspace.
• Determinants: Link lengths, joint ranges, mechanical interference, base geometry, and obstacles establish workspace boundaries.
• Workspace shape: Cartesian robots produce box-like regions, cylindrical robots produce cylindrical regions, and articulated arms usually produce irregular shell-like volumes.
• Two-link example: For planar links (L_1=0.6\,\text{m}) and (L_2=0.4\,\text{m}), radial reach satisfies
  
  TEXT

    |L₁ − L₂| ≤ r ≤ L₁ + L₂
    0.2 m ≤ r ≤ 1.0 m

  
  where (r) is distance from the first joint, assuming unrestricted rotation.
• Practical reduction: Payload limits, singularities, cables, tooling, and safety zones may make part of the geometric workspace unusable.

V. Manipulator Configurations — Fixed-Base Robot Forms

A. Types of robotic manipulators

Robotic manipulators are distinguished mainly by their sequence of revolute and prismatic joints.

• Cartesian manipulator: Uses three perpendicular prismatic axes, commonly denoted PPP; it offers a rectangular workspace, high rigidity, and simple position control.
• Cylindrical manipulator: Combines base rotation with linear radial and vertical motion; its workspace is approximately cylindrical.
• Spherical or polar manipulator: Uses rotational motion with radial extension, producing a spherical-sector workspace.
• SCARA manipulator: Uses two parallel rotary joints for horizontal motion and a vertical prismatic axis; it is fast and selectively compliant for assembly and insertion.
• Articulated manipulator: Uses several revolute joints resembling shoulder, elbow, and wrist joints; six-axis versions provide flexible position and orientation.
• Parallel manipulator: Connects a moving platform through multiple kinematic chains; Delta robots achieve very high-speed pick-and-place operation with low moving mass.
• Configuration trade-off: Serial arms offer large, flexible reach but accumulate link deflection, whereas parallel robots offer stiffness and speed but usually have smaller, more complex workspaces.
• Selection factors: Required payload, reach, precision, speed, orientation, mounting position, environmental protection, and cost determine the suitable manipulator.

VI. Mobile Robotic Systems — Locomotion and Navigation

A. Mobile robots

Mobile robots move their entire bodies through an environment rather than remaining fixed to one base location.

• Wheeled robots: Differential-drive, car-like, and omnidirectional platforms provide efficient movement on prepared surfaces.
• Tracked robots: Continuous tracks improve traction on loose or uneven ground but increase turning friction and energy use.
• Legged robots: Bipeds and quadrupeds can cross steps and irregular terrain, although balance and control are complex.
• Aerial robots: Multirotor and fixed-wing unmanned aerial vehicles support mapping, inspection, photography, and delivery.
• Underwater robots: Remotely operated and autonomous underwater vehicles use thrusters for exploration and infrastructure inspection.
• Navigation functions:
  • Localization estimates the robot’s pose using encoders, inertial sensors, GNSS, lidar, or cameras.
  • Mapping represents environmental features and obstacles.
  • Path planning finds a feasible route to a goal.
  • Obstacle avoidance modifies motion in response to detected hazards.
• Differential-drive motion:
  
  TEXT

    v = (vᵣ + vₗ)/2
    ω = (vᵣ − vₗ)/b

  
  where (v) is forward velocity, (\omega) is angular velocity, (v_r) and (v_l) are right- and left-wheel velocities, and (b) is wheel separation.
• Operational challenge: Uneven terrain, wheel slip, dynamic obstacles, limited battery energy, and uncertain sensor data reduce navigation reliability.

VII. Robot Applications — Production and Human-Centred Tasks

A. Industrial and service robots

Industrial robots primarily automate production processes, while service robots perform useful tasks for people or equipment outside conventional industrial automation.

1. Industrial robots

   • Purpose: Execute repetitive, hazardous, fast, or precision-demanding manufacturing operations.
   • Applications: Spot welding, arc welding, painting, machine tending, assembly, palletizing, packaging, and inspection.
   • Strengths: High repeatability, continuous operation, programmable motion, and consistent process quality.
   • Integration: A workcell may contain conveyors, fixtures, machine vision, programmable logic controllers, guards, and interlocked doors.
   • Limitations: High setup cost, specialist programming, maintenance requirements, and difficulty handling unstructured variation.

2. Service robots

   • Purpose: Assist humans or maintain equipment in domestic, commercial, medical, public, or field environments.
   • Applications: Robotic surgery, floor cleaning, hospital delivery, rehabilitation, hospitality, agriculture, inspection, and disaster response.
   • Operating conditions: Service robots frequently encounter people, changing layouts, uncertain objects, and incomplete sensor information.
   • Human interaction: Interfaces may include speech, touchscreens, gestures, shared control, or direct physical guidance.
   • Limitations: Perception errors, privacy concerns, limited battery life, social acceptance, liability, and safety remain major constraints.

• Explicit contrast: Industrial environments are generally structured around the robot, whereas service robots must often adapt to environments designed for humans.
• Shared requirement: Both categories require risk assessment, reliable control, suitable end effectors, maintainability, and safe failure behaviour.