Chapter 2 Lecture

• CE315 Mobile Robotics, Prof. H. Hu, School of CSEE University of Essex
• School year


  2023-2024
• Lecture 3: Robot Platforms and Mobility

  1. Introduction

  2. Wheeled mobile robots

  3. Tricycle mobile robots

  4. Car-like mobile robots

  5. Differential drive mobile robots

  6. Tracked mobile robots

  7. Legged mobile robots

  8. One-legged hopping robots

  9. Two-legged walking robots

  10. Multi-legged walking robots

  11. Underwater robots

  12. Flying mobile robots

  13. Robot guidance and control

  14. Summary
• Wheeled/tracked mobile robots


  • Able to operate both indoor and outdoor- simple to control, stable
• Flying mobile robots


  • Able to fly in many DOFs in the space, but difficult to control
• Legged mobile robots


  • Able to walk around rough ground and stairs, but difficult to control
• Underwater mobile robots


  • Underwater is an extremely difficult environment for robots
  • Difficult to control comparing with the wheeled or tracked robots
• Popular mobile robots


  • Wheeled/tracked mobile robots
  • Flying mobile robots
  • Legged mobile robots
  • Underwater mobile robots
• Some basic terminologies: Locomotion – the process of causing an autonomous robot to move. Forces must be applied to the robot in order to produce motion. Dynamics – the study of motion in which forces are modelled. Includes the energies & speeds associated with these motions. Kinematics – the study of the mathematics of robot motion. To deal with the geometric relationships that govern the system. To deal with the relationship between control parameters and behaviour of a system in state space
• Wheeled Mobile Robots


  • Achieve wheel-to-ground contact without a suspension system
  • The Centre-of-Rotation (COR) is located at the midpoint of the rear axle
  • Able to turn at the centre of rotation without moving forward
  • Two rear wheels must rotate at different speeds during turning
  • The robots are 2-degree-of-freedom platform (2 control variables)
• Tricycle Drive Mobile Robots

  There are two main configurations of tricycle mobile robots: Rear-wheel driven and front wheel steering, Single front wheel driven and steering
• Equations related to Tricycle Drive Mobile Robots
• CE315, Prof. H. Hu, School of CSEE, University of Essex
• Tricycle Drive Mobile Robots
• Tricycle Drive Mobile Robots


  • Path Guidance
  • Drive Controller
  • Steer Controller
  • Amplifier
  • Drive Motor
  • Steer Motor
  • Robot Kinematics
  • Optical encoder
  • Odometry
• Simple block diagram of the motion control for both tricycle and car-like mobile robots
• Car-like Mobile Robots
• Car-like mobile robots have limited manoeuvrability, inside wheels rotate slower than outside when turning corners, need a suspension system to keep 4 wheels to ground contact, and are 2-degree-of-freedom vehicles
• Differential Drive Mobile Robots
• Differential Drive Mobile Robots

  • Two wheels are driven independently & other wheels are castors
  • Steering is accomplished by driving the wheels at different speeds
  • The robot can turn around the centre of rotation (ROF)
  • The robots are 2-degree-of-freedom platforms
  • Castors are used to achieve stability
• Kinematics equations for Differential Drive Mobile Robots
• 𝑣௟ = 8𝑐��/𝑠; 𝑣௥ = 10𝑐𝑚/𝑠; 𝑊 = 50𝑐𝑚 𝑥 0 = 80𝑐𝑚; 𝑦(0) = 30𝑐𝑚; 𝜃(0) = 𝜋/3
• Question: We assume Write C code to calculate the robot trajec
• CE315, Prof. H. Hu, School of CSEE, University of Essex

  2023-2024
• The Wealth of Nations was written

  1776
• Rational


  (in classical economic theory) economic agents are able to consider the outcome of their choices and recognise the net benefits of each one
• Consumers act rationally by


  Maximising their utility
• Producers act rationally by


  Selling goods/services in a way that maximises their profits
• Workers act rationally by


  Balancing welfare at work with consideration of both pay and benefits
• Governments act rationally by


  Placing the interests of the people they serve first in order to maximise their welfare
• A firm increases advertising

  Demand curve shifts right
• Write C code to calculate the robot trajectory (k=0,1,2,3,4,5,6,7,8,9,10) using the odometry equations above
• Odometry calculation


  Equations provided in the text
• Two speed-control loops in parallel
• Tracked Mobile Robots are able to traverse rough terrain and smooth ground. They are 2-degree-of-freedom vehicles and differentially driven. Their skid-steering operation provides rather poor odometry
• Legged walking robots can be grouped into two classes: Static stable systems with three or more legs and Dynamic stable systems with one or two legs
• One-Legged Walking Robot was built at CMU. It has a circular body with a cylindrical leg. Its body and leg are connected by a gimbal joint to form a hip. Two linear hydraulic actuators control the angles between the body and leg
• Two-legged Walking Robots have main features
• Two linear hydraulic actuators control the angles between the body and leg
• CE315 Mobile Robotics, Prof. H. Hu, School of CSEE, University of Essex

  2023-2024