B. Siciliano, L. Sciavicco, L. Villani, G. Oriolo, Robotics: Modelling, Planning and Control, Springer, London, 2009, ISBN 978-1-84628-642-1
- Chapter 1 ─ Introduction
- Chapter 2 ─ Kinematics
- Chapter 3 ─ Differential Kinematics and Statics
- Chapter 5 ─ Dynamics
Introduction to Robotics
Unit 1: Robots and Robotics
Unit 2: Robot Manipulators
Unit 3: Mobile Robots
Textbook: Sections 1.1 + 1.2
Unit 1: Robots and Robotics
Unit 1 in a Nutshell
- The concept of robot is introduced with reference to the evolution of the field from industrial robotics to field and service robotics
- The main components of a robotic system are illustrated
What is a Robot?
- Robot (robota = executive labour);
- One of the human beings’ greatest ambitions has been to give life to their artifacts (mythology);
- People continue to imagine the robot as a humanoid who can speak, walk, see and hear, with gestures and reactions of human type (science fiction);
- The robot is defined as a machine that is able to carry out tasks automatically to replace or improve human work (reality).
Wall-E, Pixar (2008)
- Human-machine interaction;
- A rigid sequence, it is the human to comply;
- Do we really want a fully autonomous machine?
“Modern Times”, Charlie Chaplin (1936)
Robots ― A 50 Year Journey
The development of the field in the second half of the past century is illustrated by this iconic video which was first presented at the 2000 IEEE International Conference on Robotics and Automation in San Francisco, CA:
“Robots ― A 50 Year Journey”, Oussama Khatib (2000)
Robots ― The Journey Continues
The further development of the field in the last fifteen years is illustrated by this lively video which has recently appeared in conjunction with the Second Edition of the Springer Handbook of Robotics.
"Robots ― The Journey Continues", Bruno Siciliano, Oussama Khatib, Torsten Kröger (2016)
Unit 2: Robot Manipulators
Unit 2 in a Nutshell
- The main geometries for a robot arm are presented along with their features in terms of joint type, workspace, mechanical stiffness, accuracy, actuation and industrial applications;
- The spherical wrist is introduced as the main design in terms of compactness and dexterity;
- Both open and closed kinematic chains are considered.
Components of a Robotic System
- Locomotion apparatus (wheels, crawlers, mechanical legs);
- Manipulation apparatus (mechanical arms, end-effectors, artificial hands).
- Animates the mechanical components of the robot;
- Motion control (servomotors, drives, transmissions.
- Proprioceptive sensors (internal information on system);
- Exteroceptive sensors (external information on environment).
- Execution of action set by task planning coping with robot and environment’s constraints;
- Adoption of feedback principle;
- Use of system models.
Robot Mechanical Structure
Mechanical structure of robot manipulator: sequence of rigid bodies (links) interconnected by means of articulations (joints):
- Arm ensuring mobility;
- Wrist conferring dexterity;
- End-effector performing the task required of robot.
- Open vs. closed kinematic chain.
- Prismatic vs. revolute joints.
Degrees of freedom:
- 3 for position + 3 for orientation.
- Portion of environment the manipulator’s end-effector can access.
- Three prismatic joints;
- Very good mechanical stiffness;
- Wrist positioning accuracy constant everywhere in the workspace;
- Low dexterity (all joints prismatic);
- Electric (seldom hydraulic) actuation;
- Employed for transportation and assembly;
Manipulation of objects of large dimensions and heavy weight gantry structure.
- One revolute joint and two prismatic joints;
- Good mechanical stiffness;
- Wrist positioning accuracy decreases as horizontal stroke increases;
- Horizontal prismatic joint makes wrist suitable to access horizontal cavities;
- Employed for carrying objects even of large dimensions;
- Hydraulic actuation preferred to electric actuation.
- Two revolute joints and one prismatic joint (all axes of motion are parallel);
- High stiffness to vertical loads and compliance to horizontal loads Selective Compliance Assembly Robot Arm;
- Positioning accuracy decreases as distance of wrist from first joint axis increases;
- Employed for manipulation of small objects (vertical assembly tasks);
- Electric actuation.
- Three revolute joints;
- Most dexterous structure (similarity with human arm);
- Wrist positioning accuracy varies inside workspace;
- Wide range of industrial applications;
- Electric actuation.
Manipulation of larger payloads closed kinematic chain with higher stiffness to guarantee comparable positioning accuracy (parallelogram geometry between shoulder and elbow joints)
- Multiple kinematic chains connecting base to end-effector;
- High structural stiffness;
- High operational speeds;
- Reduced workspace.
Hybrid structure employed for execution of manipulation tasks requiring large values of force along vertical direction:
- Parallel arm;
- Serial kinematic chain.
Wrist and End-effector
Three revolute joints determining end-effector orientation;
High compactness and dexterity;
Position and orientation decoupling.
Specified according to task the robot should execute;
For material handling tasks gripper of proper shape and dimensions determined by object to be grasped;
For machining and assembly tasks tool or specialized device (welding torch, spray gun, mill, drill, screwdriver, etc).
Unit 3: Mobile Robots
Unit 3 in a Nutshell
- Mobile robots are introduced to provide locomotion to robotic systems;
- Wheeled mobile robots are classified according to different types of wheels;
- Mobile manipulation combines dexterity of the articulated arm with unlimited mobility of the base.
Wheeled Mobile Robots
The mechanical structure of a mobile robot consists of one or more rigid bodies equipped with a locomotion system.
Wheeled mobile robots:
- Base (chassis);
- Wheels (providing motion with respect to ground);
- Eventually trailers, also equipped with wheels, connected to base by means of revolute joints.
Legged mobile robots:
- Multiple limbs;
- Feet periodically in contact with ground to realize locomotion;
- Design often inspired by living organisms (biomimetic robotics).
- Can rotate about an axis going through center of wheel and orthogonal to wheel plane;
- Constant orientation with respect to chassis (rigidly attached).
- First rotation axis same as fixed wheel;
- Second rotation axis going through center of wheel;
- Variable orientation with respect to chassis.
- Vertical axis not going through center of wheel (displaced by constant offset);
- Automatic swivel rapidly aligning with direction of motion of chassis;
- Supporting point for static balance without affecting mobility of chassis (commonly used in shopping carts and wheelchairs).
Differential-drive Mobile Robot
- Two fixed wheels with common axis of rotation, separately controlled;
- One or more passive caster wheels, whose function is to keep robot statically balanced;
- Can rotate on the spot, without moving midpoint between wheels, provided that angular velocities of the two wheels are equal and opposite.
Synchro-drive Mobile Robot
- Three aligned steerable wheels synchronously driven by only two motors through mechanical coupling (chain or transmission belt);
- First motor controls rotation of wheels about horizontal axis (vehicle traction);
- Second motor controls rotation of wheels about vertical axis (vehicle steering);
- Often, third motor used to rotate independently upper part of chassis (turret) with respect to lower part (orienting directional sensor or recovering orientation error).
Car-like Mobile Robot
- Two fixed wheels mounted on rear axle;
- Two steerable wheels mounted on front axle;
- One motor provides (front or rear) traction;
- Another motor changes orientation of front wheels with respect to chassis;
- Two front wheels must have different orientation (avoiding slippage);
- Internal wheel slightly more steered with respect to external one (Ackermann steering device).
Mobile Robots Features
- A three-wheel robot is statically balanced as long as its center of mass falls inside the support triangle defined by the contact points between wheels and ground;
- Robots with more than three wheels have a support polygon (typically easier to guarantee balance);
- When robot moves on uneven terrain, a suspension system is needed to maintain contact between each wheel and ground.
- Workspace of mobile robot potentially unlimited;
- Local mobility of non-omnidirectional mobile robot always reduced;
- A tricycle robot cannot move instantaneously in a direction parallel to rear wheel axle, yet can be manoeuvered so as to obtain net displacement in that direction at end of motion;
- Number of robot’s DOFs (number of admissible instantaneous motions) lower than number of its configuration variables.
Risorse della lezione
- Introduction to Robotics
- Quiz: Quiz Lesson 1 - Introduction to Robotics
- Industrial Robotics and Advanced Robotics
- Quiz: Quiz Lezione 2 - Industrial Robotics and Advanced Robotics
- Representation of Orientation
- Quiz: Quiz Lezione 3 - Representation of Orientation
- Direct Kinematics
- Quiz: Quiz Lezione 4 - Direct Kinematics
- Inverse Kinematics
- Quiz: Quiz Lezione 5 - Inverse Kinematics
- Quiz: Quiz Lezione 6 - Jacobian
- Differential Kinematics
- Quiz: Quiz Lezione 7 - Differential Kinematics
- Inverse Kinematics Algorithms
- Quiz: Quiz Lesson 8 - Inverse Kinematics Algorithms
- Quiz: Quiz Lesson 9 - Statics
- Lagrange Formulation
- Quiz: Quiz Lesson 10 - Langrange Formulation
- Use of Dynamic Model
- Quiz: Quiz Lesson 11 - Use of Dynamic Model
- Newton-Euler Formulation
- Quiz: Quiz Lesson 12 - Newton-Euler Formulation