angular sensor

8/10/2019 Angular Sensor

1/21

Sensors Technology

Angular Displacement

Sensors

Prepared by :Mohd Shafie Sani


2/21

Topic Outline

1. Introduction

2. Angular Sensor Definition

3. Type of Encoders

4. Natural Binary Code Encoder

5. Gray Scale Code Encoder

6. Truth Table for Binary and Gray Code7. Converting between Gray and Binary

8. Incremental Encoder

9. Tutorials

10.Comparison between Absolute and Incremental Encoders11.Conclusion

12.References


3/21

Encoders for crane systems
http://localhost/var/www/apps/conversion/tmp/scratch_6/Encoders%20for%20crane%20systems%20from%20SICK%20-%20YouTube.mpghttp://localhost/var/www/apps/conversion/tmp/scratch_6/Encoders%20for%20crane%20systems%20from%20SICK%20-%20YouTube.flvhttp://localhost/var/www/apps/conversion/tmp/scratch_6/Encoders%20for%20crane%20systems%20from%20SICK%20-%20YouTube.mpghttp://localhost/var/www/apps/conversion/tmp/scratch_6/Encoders%20for%20crane%20systems%20from%20SICK%20-%20YouTube.flv


4/21

Angular displacementof a body is the angle in

radians (degrees, revolutions) through which a

point or line has been rotated in a specified

sense about a specified axis.

As the particle moves along the circle, it travelsan arc length s, which becomes related to the

angular position through the relationship:

1. Introduction


5/21

Thus angular displacement is;


6/21

2. Angular Sensor Definition

A digital optical

encoder, whichconverts motion into

digital signal.

By counting a single

bit, the pulses are

converted to relative

or absolute position

measurements.


7/21

3. Type of Encoders

Absolute encoder

where a unique digitalword corresponds to arotational position of

shaft

Incremental encoder

which produces digital

pulses as the shaftrotates, and measure the

relative position of the

shaft


8/21

Absolute Encoder Incremental Encoder


9/21

4. Natural Binary Code Encoder

Has 16 bits (transition from 0 to 15) for 4 tracks disk

Reads the value from the track, all at once

Problem of differentiating the 7 to 8 bit.

High error when reading the values from the disk.

Natural Binary Code Disk


10/21

5. Gray Scale Code Encoder

Step by step reflected code

Reading the value which alternates from track to track

The percentage of error is low compared to natural

binary code

Gray Code Disk


11/21


12/21

7. Converting betweenGray and Binary
http://localhost/var/www/apps/conversion/tmp/scratch_6/1.avihttp://localhost/var/www/apps/conversion/tmp/scratch_6/1.avihttp://localhost/var/www/apps/conversion/tmp/scratch_6/1.avihttp://localhost/var/www/apps/conversion/tmp/scratch_6/1.avihttp://localhost/var/www/apps/conversion/tmp/scratch_6/1.avihttp://localhost/var/www/apps/conversion/tmp/scratch_6/1.avi


13/21

8. Incremental Encoder

Incremental encoders generate a precisely definednumber of pulses per revolution.

They can measure angular or linear distance

movement.

The phase difference between the signals A and B,which are shifted by 90 degrees, allows evaluation of

the direction of rotation.


14/21

Examples:Decimal Binary Gray ?

10 1 0 1 0

1 1 0 0 11112 0 0 1 0

13 1 1 0 1

9. Tutorials


15/21

Examples:Dec Binary ? Gray

10 1 1 1 1

2 0 0 1 113 1 0 1 1


16/21

10. Comparison between Absolute andIncremental Encoders

Differences Absolute Incremental

Output Binary number, such as

from 0000 to 1111

produces two or three

simple signals.

Mechanisms The disk has a pattern of

black and transparent

blocks

having a series of

alternating black and

transparent blocks of the

same size

Use Works best through a single

rotation. Eg; accurate

positioning using crane or

lift

For continuous rotation. Eg

; wheel spin detector for a

cars anti-lock braking

system

Accuracy High accuracy. Maintain its

position when power loss.

Less accurate than

absolute. Position reset to

zero when power loss.


17/21

Differences Absolute Incremental

Cost Expensive compared to

incremental

Cost effective

Simplicity Signals can be hard to

interpreted due to its

unique codes

Signals can be easily

interpreted


18/21

11. Conclusion

There are 2 types of encoder: Absolute and

incremental encoder

Both encoders can use 2 different type of codes :

Binary and Gray code.


19/21

12. References

1. Industrial ElectronicsTerry L.M. Bartelt, Delmar,1997

2. Mechatronics System DesignS. Devdas, A. K. Richard, PWS, 1997

3. Introduction to Mechatronics and Measurement Systems, Alciatore,1998

4. http://www.wisc-online.com/objects/viewobject.aspx?id=iau8007
http://www.wisc-online.com/objects/viewobject.aspx?id=iau8007http://www.wisc-online.com/objects/viewobject.aspx?id=iau8007http://www.wisc-online.com/objects/viewobject.aspx?id=iau8007http://www.wisc-online.com/objects/viewobject.aspx?id=iau8007


20/21

Q & A

Session


21/21

Practical

Session

angular sensor

Documents