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Internal sensors

Internal sensors. Josep Amat and Alícia Casals Automatic Control and Computer Engineering Department . Program. Chapter 1. Introduction Chapter 2. Robot Morphology Chapter 3. Control Chapter 4. Robot programming Chapter 5. Perception

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Internal sensors

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  1. Internal sensors Josep Amat and Alícia Casals Automatic Control and Computer Engineering Department

  2. Program Chapter 1. Introduction Chapter 2. Robot Morphology Chapter 3. Control Chapter 4. Robot programming Chapter 5. Perception Chapter 6. Mobile robots. Architecture, components and characteristics Chapter 7. Robotics applications. Robotization

  3. Chapter 2. Robot Morphology 2.1 – Mechanical Structures. Classical Architectures. 2.2 – Characteristics of a Manipulator. Definitions. 2.3 - Actuators. Pneumatic, Hydraulic and Electrical. 2.4 – Movement transmission systems: Gearboxes, movement transmission and conversion. 2.5 – Robot internal sensors. Position sensors, speed and acceleration. 2.6 – End Effectors.

  4. Components of a Robot External Sensors Environment Programming Net Internal Sensors Control Unit Actuators Mechanical Structure User

  5. Detectors Position sensors Mechanical: Internal sensors Actuators Mechanical structure

  6. Electromagnetic: Detection from the variations of the oscillation conditions of an L – C sensor circuit Detectors Internal sensors Position sensors Actuators Mechanical structure

  7. Detectors Position sensors Optical: From the interruption of a light beam, or reflection. Internal sensors Actuators Mechanical structure

  8. Types of sensors Angular Linear

  9. Digital Vcc R1 V = Vcc R R R2 a R a R1 V = Vcc = Vcc a a0 a0R 0 V Types of sensors Resistive (Potentiometers) Angular Analog

  10. Ve = A sin (wt) Ve = A sin(wt ) cos a Ve = A sin(wt ) sin a Types of sensors Resistive (Potenciometers) Angular Inductive ( Resolver ) Analog Digital A is obtained through the lecture in a look up table of arcsin and arccos

  11. Low resolution conversions S1 = V cos a a aX A/D A/D D/A a S2 = V sin a High resolution conversions mcontroler aX e A S1 S2 Ve = V sin (wt) S1 = V sin(wt ) cos a S2 = V sin(wt ) sin a Possibility of obtaining the value of a by means of “tracking”

  12. Resistive (Potentiometers) Angular Inductive ( Resolver ) Absolute Incremental Analog Digital Types of sensors

  13. Optical Encoder Absolute Fotoelectric sensor n paths 2n divisions n optical barriers 2 paths 4 divisions

  14. Ambiguity when reading the natural binary code Commercially 10 bits 1024 div.  Resol. 0.35º 12 bits 4096 div.  Resol. 0.088º 14 bits 16384 div.  Resol. 0.022º Encoder diameters: de 50 a 175 mm Elimination of the reading ambiguity using the Gray code

  15. Example of a disc with the Gray code Example of an angular encoder

  16. Types of Sensors Resistive (Potentiometers) Angular Inductive ( Resolver ) Absolute Incremental Analog Digital

  17. Commercially 10 bits 1024 div.  Resol. 0.35º 12 bits 4096 div.  Resol. 0.088º 14 bits 16384 div.  Resol. 0.022º Signal obtained after displacing the sensor over a coded disc 1 2 3 4 5 6 7 8 9 10 11 12 Gray code

  18. Commercially 10 bits 1024 div.  Resol. 0.35º 12 bits 4096 div.  Resol. 0.088º 14 bits 16384 div.  Resol. 0.022º Gray code Possibility of detecting the counting sense using two sensors

  19. Incremental Optical Encoder A B R 1 mark = 4divisions

  20. 0 1 200 x 4 = 800 P Q Q P

  21. r 120 cm. 60 60 j = 60º 360 360 q = 210 l = 2 p 1200 l = 1256 mm. 1256 mm. r = 170,6 Computing resolution = = q = 170,6 Using a a 10 bits encoder directly coupled to the motor axis = 7,3 mm. js

  22. Measuring strategies 1 : 1 0 j Arm 0 360º 0 j Encoder Absolute Code j dn-1 . . . . do dn-1 . . . . do Incremental Counter

  23. Arm 360º j n = Absolute Code j dn-1 . . . . do dn-1 . . . . do Incremental Counter Measuring strategies 1 : n 0 j 0 360º Encoder

  24. Arm 360º n = m j m · · · m = 2 m = 1 Code j Absolute + Inc. dn+p-1 . . dn-1 · · · · do dn+p-1 . . dn-1 · · · ·do Counter Incremental Measuring strategies 1 : n 0 j Encoder 0 360º 0 360º Encoder coupledto the arm with atransmissionratio: m x n

  25. r 120 cm. j = 60º l = 1256 mm. 1256 mm. r = x 6 x 8 8192 Computing resolution q = 8 · 210 = q = 8192 = 0,15 mm. Using a 10 bits encoder coupled with a 1:64 transmission ratio

  26. l = 1256 mm. 1256 mm. r = 204.800 0 1 2 3 · · · 199 200 With a 10 bits A/D converter r’ = r/1024 200 x 1024 = 204.800 = 0,006 mm. Sinusoidal light obtained from Moore interference r < 0,01 mm.

  27. Types of sensors Resistive (Potentiometers) Angular Inductive ( Resolver ) Incremental Absolute Analog Digital Resistive Inductive ( Inductosyn ) Linear LVDT Optical rule Analog Digital

  28. R Sensing with a linear potentiometer

  29. Types of sensors Resistive (Potentiometers) Angular Inductive ( Resolver ) Incremental Absolute Analog Digital R Resistive Inductive ( Inductosyn ) Linear LVDT Optical rule Analog Digital

  30. 0,2 mm Inductosyn sensor With two secondary sensors shifted 90º, the resolution is: 0,2 / 28 < 0.001 mm * * With an analog interpolation using a 8 bits ADC

  31. Resistive (Potentiometers) Angular Inductive ( Resolver ) Incremental Absolute Analog Digital Resistive Inductive ( Inductosyn ) Linear LVDT Optical rule Analog Digital Types of sensors

  32. LVDT LVDT = Linear Voltage Differential Transformed) Linear sensing displacements

  33. LVDT V1 v V2 V1 V2 V1- V2 Linear sensing displacements

  34. Analog Digital Analog Digital Types of sensors Resistive (Potentiometers) Angular Inductive ( Resolver ) Incremental Absolute Resistive Inductive ( Inductosyn ) Linear LVDT Optical rule

  35. Incremental optical rule Head reader Absolute optical rule

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