(SEM V) THEORY EXAMINATION 2023-24 ROBOTICS

SECTION A — Very Short Answers (2 × 10 = 20)

(a) What is meant by robot anatomy?

Robot anatomy refers to the physical structure of a robot — its body, joints, links, and actuators — that define its shape, movement, and configuration. It determines how the robot manipulates objects in its workspace.

(b) Classify the word Manipulator.

A manipulator is the arm of a robot designed to move objects. It consists of:

Base and joints (revolute or prismatic)        Links connecting joints

End-effector for handling tasks

Types:

Serial manipulators                 Parallel manipulators           Hybrid manipulators

(c) Write Asimov’s Laws of Robotics.

A robot may not injure a human being or, through inaction, allow a human to come to harm.

A robot must obey orders given by humans except where such orders conflict with the first law.

A robot must protect its own existence as long as this does not conflict with the first or second laws.

(d) What are the types of automation?

Fixed (Hard) Automation – Designed for high-volume, repetitive tasks.

Programmable Automation – Used for batch production with reprogrammable operations.

Flexible (Soft) Automation – Computer-controlled, adaptable to product variations with minimal setup time.

(e) Define Power-to-weight ratio in robotics.

It is the ratio of the robot’s output power to its total weight, indicating how efficiently the robot can perform heavy tasks relative to its mass.

Power-to-weight ratio=Power Output (W)Weight (N)\text{Power-to-weight ratio} = \frac{\text{Power Output (W)}}{\text{Weight (N)}}Power-to-weight ratio=Weight (N)Power Output (W)​ 

(f) What is Repeatability of a robot?

Repeatability is the ability of a robot to return to the same position and orientation repeatedly under identical conditions. It measures precision (not accuracy) and is typically within ±0.1 mm for industrial robots.

(g) What is meant by Work Envelope?

The work envelope or workspace is the 3D volume within which the robot’s end-effector can move. It depends on the configuration, link lengths, and joint ranges.

(h) What is meant by Payload Capacity of a robot?

The maximum weight a robot can handle safely and efficiently without losing accuracy or damaging its joints. It includes the weight of the end-effector and the load.

(i) Discuss the applications of Tactile Sensors.

Detecting contact and pressure during gripping.            Measuring surface texture, hardness, or slip.

Used in robotic hands for object manipulation and assembly tasks.

Helpful in medical robots and quality inspection systems.

(j) Describe the PUMA Robot Configuration.     PUMA (Programmable Universal Machine for Assembly):

6 DOF (Degrees of Freedom) articulated robot.

Structure similar to a human arm: shoulder, elbow, wrist joints.

Uses rotary (revolute) joints.                   Employed in assembly, welding, and pick-and-place tasks.

SECTION B — Short Descriptive (Any 3 × 10 = 30)

(a) Pitch, Yaw, and Roll Motions

Pitch → rotation about Y-axis (up-down).            Yaw → rotation about Z-axis (left-right).

Roll → rotation about X-axis (twist motion).

Sketch the wrist with 3 intersecting axes to illustrate.

(b) Transformation Matrix Problem

For frame {2} rotated 60° about X-axis with displacement D21=[3,2,2]TD_2^1 = [3, 2, 2]^TD21​=[3,2,2]T:

T21=[10030cos⁡60−sin⁡6020sin⁡60cos⁡6020001]T_2^1 = \begin{bmatrix} 1 & 0 & 0 & 3\\ 0 & \cos60 & -\sin60 & 2\\ 0 & \sin60 & \cos60 & 2\\ 0 & 0 & 0 & 1 \end{bmatrix}T21​=​1000​0cos60sin600​0−sin60cos600​3221​​

Then multiply T21×P2T_2^1 \times P_2T21​×P2​ to get P1P_1P1​.

(c) Types of Joints in Robots

Revolute (Rotary)               Prismatic (Sliding)              Cylindrical, Spherical, Helical, Planar

Examples:

SCARA robot → 4 DOF (two rotary + one prismatic + one rotational wrist).

Gantry robot → Cartesian configuration (3 linear joints).

(d) Four Basic Robot Configurations

Cartesian (Gantry)       Cylindrical           Spherical (Polar)        Articulated (Jointed-arm)

Each configuration uses a different coordinate system defining motion freedom.

(e) Hydraulic vs Electrical Actuators
 

Hydraulic Actuators: High force, smooth control, ideal for heavy-duty robots.

Electrical Motors: Fast response, clean operation, good for precision robots.
Pneumatic drives use compressed air with a cylinder-piston arrangement for light, rapid motions.

SECTION C — Long Answer Questions

4. Sensors

Role: Provide feedback for control, position, and environment perception.

Classification: Internal (position, velocity, torque) and external (vision, proximity, tactile).

Functions: Safety, precision, automation, defect detection.

5. Denavit–Hartenberg (D-H) Criterion

Defines four parameters (ai,αi,di,θia_i, \alpha_i, d_i, \theta_iai​,αi​,di​,θi​) to describe link and joint relationships in a standard matrix form for kinematic modeling.

6. Actuating Systems

Hydraulic: High power density.     Pneumatic: Simple, fast response.     Electric: Precise, clean, easy control.

(Diagram on page 2 illustrates hydraulic and electric joint actuation.)

7. Gears and Sensors

Gear types: Spur, helical, bevel, worm.         Tactile sensors: Require contact (e.g., force sensors).

Non-tactile sensors: Optical, ultrasonic, or acoustic (page 2 diagram shows acoustic sensor sketch).