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Velocity sensors in_robotics


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Velocity sensors in_robotics

  2. 2. Velocity Sensor: A velocity or speed sensor measures consecutive position measurements at known intervals and computes the time rate of change in the position values.
  3. 3. Velocity Sensors: 1) Tachometers 2) LSV 3) Piezoelectric Sensors 4) Accelerometer Sensor
  4. 4. Tachometers: A most important device that is used to provide velocity feedback is the tachometer. It is also known as rpm gauge, and revolution counter. A tachometer is employed in a motor to calculate the rotational speed of a shaft. The output is displayed as RPM (revolution per minute) in an analog device.
  5. 5. The two common types of a tachometer are: 1) AC tachometer 2) DC tachometer
  6. 6. 1) AC tachometer: It possesses primary and secondary stators with fixed windings, and a rotor with permanent magnet. If the rotor is stationary, a constant output voltage will be obtained. If the rotor is moving, proportional to the speed of a rotor is induced. This type of tachometer cannot provide information of direction with only one output winding.
  7. 7. 2) DC tachometer: DC tachometer is the most commonly used instrument in the robotics. It is a DC generator implemented to provide an output voltage that is proportional to the angular velocity of the armature. In this mechanism, the rotor and rotational part will be attached directly. It has a stationary device called as commutator, which is connected with the split slip rings.
  8. 8. It is used for picking the induced output signal from the rotating coil.
  9. 9. Laser surface velocimeter: A laser surface velocimeter (LSV) is a non- contact optical speed sensor measuring velocity and length on moving surfaces. Laser surface velocimeters use the laser Doppler principle to evaluate the laser light scattered back from a moving object.
  10. 10. LSV is based on Doppler effect (or Doppler shift) that is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source.
  11. 11. They are widely used for process and quality control in industrial production processes.
  12. 12. Piezoelectric Sensor: A piezoelectric sensor is a device that uses the piezoelectric effect, to measure changes in velocity, pressure, acceleration, temperature, strain, or force by converting them to an electrical charge. The prefix piezo- is Greek for 'press'
  13. 13. Principle of operation: The way a piezoelectric material is cut produces three main operational modes: 1) Transverse 2) Longitudinal 3) Shear.
  14. 14. Two main groups of materials are used for piezoelectric sensors: piezoelectric ceramics and single crystal materials. Schematic of piezoelectric sensor
  15. 15. Piezoelectric sensors are versatile tools for the measurement of various processes. They are used for quality assurance, process control, and for research and development in many industries
  16. 16. ACCELEROMETER SENSOR An accelerometer is a device that measures proper acceleration(Time rate of change of velocity). They are typically used in one of three modes: 1) As an inertial measurement of velocity and position; 2) As a sensor of inclination, tilt, or orientation in 2 or 3 dimensions, as referenced from the acceleration of gravity (1 g = 9.8m/s2); 3) As a vibration or impact (shock) sensor
  17. 17. Accelerometer
  18. 18. THANKYOU