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J. Iqbal, A.H. Khan, N.G. Tsagarakis and D.G. Caldwell, “A novel exoskeleton robotic system for hand
rehabilitation - Conceptualization to prototyping”, Biocybernetics and Biomedical Engineering, 2014, 34(2):79-89](https://image.slidesharecdn.com/roboticssensorsandsimulation-230212161506-2d4d0f65/85/Robotics-Sensors-and-Simulation-pptx-9-320.jpg)
Robotics Sensors and Simulation.pptx
- 1. Mechatronics, Robotics, Sensors and Simulation (500682) Lecture 2: Mechatronic/Robotic System, Motors
- 2. Outlines • Mechatronic/Robotic System – Components, their Role and Types – System Integration and Testing – Signal Perspective • DC Motors (Quick recap) – Working – Types • Special Motors – Servo Motors – Stepper Motors
- 4. Mech. System – Closed-loop Perspective
- 5. Mech. System – Closed-loop Perspective Controller Actuator Plant Sensor Ref. Current - Control for Engineers (500662) Mech., Robotics, Sensors & Simulation (500682) Robotics & Automation (601089) Mechatronic Systems (500680)
- 6. PID (Proportional Integral Derivative) Controller P I D u(t) r(t) r(t) u(t)
- 7. Overall Mechatronic System Signal Generator Motor Driver Test Signal Arduino Oscilloscope Motor Give Test I/p to System Record O/p from Sensor Sensor Data
- 9. Mechatronic System in Operation 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 -0.4 -0.35 -0.3 -0.25 -0.2 -0.15 -0.1 -0.05 0 Time [sec] Angle [rad] Desired Measured 0 1 2 3 4 5 6 7 8 9 10 0 0.2 0.4 0.6 0.8 1 1.2 Time [sec] Angle [rad] Desired Measured Step response Sinusoidal response J. Iqbal, A.H. Khan, N.G. Tsagarakis and D.G. Caldwell, “A novel exoskeleton robotic system for hand rehabilitation - Conceptualization to prototyping”, Biocybernetics and Biomedical Engineering, 2014, 34(2):79-89
- 10. MIMO Systems S. Ullah, A. Mehmood, Q. Khan, S. Rehman and J. Iqbal, “Robust integral sliding mode control design for stability enhancement of underactuated quadcopter”, International Journal of Control, Automation and Systems, 2020, 18(7):1671-1678
- 12. Parts of a Typical Motor • Commutator • Rotor – Rotating portion of the motor – Turns within the magnetic field • Stator – Stationary portion of the motor • Bearing – Allow free rotation of the motor shaft Brushes Electrical connector between armature and power Commutator Mechanical rectifier converts AC to DC Rotor: Armature conductor are connected to the Commutator Stator Produces an external flux + + + = DC Machine
- 13. Types • Motors convert electric energy to mechanical force or motion • Input: – AC/DC electrical energy source • Industrial robots: – AC Servo motor • Mobile robots, Domestic robots: – DC motor – DC Servo motor – Stepper motor • Output: – Output is mechanical motion of the output shaft – Rotation about or a translation along the shaft M O T O R
- 14. Motor Accessories • Motor (Armature) • Shaft • Gear Box • Encoder (Position sensor)
- 15. j.Iqbal@hull.ac.uk Room: 303H RBB DC Motors
- 16. DC Motors • Attractive for Robotics, Medical and Automotive applications – Can be small – Efficient – High and low torque • Classification – Brush DC motor – Brushless DC (BLDC) motor
- 17. Brush DC Motors • A typical Brush DC motor consists of – An armature (or rotor) – A commutator (split ring wrapping around the axle which connect to opposite poles of a power source to deliver positive and negative charges to the commutator) – Brushes – Axle – Field magnet
- 18. Brush DC Motors • Principle – The brushes charge the commutator inversely in polarity to the permanent magnet – This in turn causes the armature to rotate – The rotation’s direction (c/w or anti c/w) can be reversed by reversing the polarity of the brushes, (i.e., reversing the leads on the battery)
- 19. Brush DC Motors Video Content: https://www.youtube.com/watch?v=LAtPHANEfQo
- 20. Brush DC Motors • Advantages – Generally inexpensive and reliable – Simple two wire control – If the brushes are replaceable, these motors also boast a somewhat extended operational life – They tend to handle rough environments reliably – They need few external components or no external components at all • Disadvantages – Require periodic maintenance as brushes must be cleaned – Sometimes replaced for continued operation – (ruling them out for critical medical designs) – Also, if high torque is required, brush motors fall a bit flat – As speed increases, brush friction increases and viable torque decrease – Electromagnetic interference (EMI) generated by brush arcing
- 21. Brushless DC Motors (BLDC) • Principle – No brush, no commutator – A BLDC motor mounts its permanent magnets, usually four or more, around the perimeter of the rotor in a cross pattern – More expensive but long life – Come in compact packages (viable for a variety of compact designs) – BLDC motors are synchronous motors – Efficiency is a primary selling feature for BLDC motors
- 22. Brushless DC Motors (BLDC) Video Content: https://www.youtube.com/watch?v=bCEiOnuODac
- 23. DC Series Motors • The field winding is connected internally in series to the armature winding • Advantages – High starting torque (∝ square of field current) – Best suited for traction applications
- 24. DC Series Motors • Disadvantages – Poor speed regulation: * With the increase in the load → Speed of the machine decreases * In comparison, DC shunt motor maintains almost constant speed from no load to full load – Should always require being loaded before starting the motor – ∴, they are not suited for applications where load on the motor is completely removed
- 25. DC Shunt Motors • The field windings are shunted to / connected in parallel to the armature winding of the motor • Since they are connected in parallel → the armature and field windings are exposed to the same supply voltage • The torque is ∝ to the armature current (𝐼𝑎) • How to increase torque: – Increase 𝐼𝑎 – by decreasing 𝐼𝑠ℎ – i.e. increase 𝑅𝑠ℎ – Use conductors with less dia (𝑅 = 𝜌 𝑙 𝐴 ) • The field winding must be wound with many turns to increase the flux linkage
- 26. DC Compound Motors • They are made up of both series the field coils and shunt field coils connected to the armature winding
- 28. AC/DC Servo Motors • Features – An obvious choice when higher precision is required – Can get a very high torque in a small and light weight package • Composition – AC/DC Motor – A gearing set – A control circuit – A position-sensor (Potentiometer/Encoder) • Applications – Toy car – RC Helicopters – Planes – Robots – Machines
- 30. AC/DC Servo Motors • Features – Servo motors do not rotate freely like a standard DC motor – Instead the angle of rotation is limited to 180° (or so) back and forth – Pulse Width Modulation (PWM) is used for the control signal of servo motors – When a servo is commanded to move, it will move to the position and hold that position, even if external force pushes against it. The servo will resist from moving out of that position, with the maximum amount of resistive force the servo can exert being the torque rating of that servo
- 31. AC/DC Servo Motors Video Content: https://www.youtube.com/watch?v=LXURLvga8bQ
- 32. Stepper Motors • Features: – A stepper motor can control the angular position of the rotor without a closed-loop feedback – It is simple, accurate and open-loop system – Different method of motorisation to that of servo • Working Principle – A permanent magnet is used for rotor – All the coils are not energised simultaneously – Energised step by step (one after the other)
- 33. Stepper Motors Video Content: https://www.youtube.com/watch?v=eyqwLiowZiU
- 35. Stepper Motors • Advantages – The rotation angle is proportional to the input pulses. – Full torque at standstill – Very low-speed synchronous rotation is possible to achieve – There are no brushes so it is reliable – Speed is directly proportional to the frequency of the input as pulses; hence a wide range of rotational speed can be realised – Low speed with high precision • Disadvantages – Low efficiency – Difficult to operate at very high speed – May produce more noise – For the smooth move, micro stepping is required
Editor's Notes
- #6: Proprioceptive sensors measure the state of the robot itself (wheel position or speed, battery charge, etc.) while exteroceptive sensors measure the state of the environment (mapping, temperature, etc.) Electric Pneumatic Hydraulic Standard Motors AC Motors DC Motors Special Motors AC/DC Servo Motors Stepper Motors