1. Mechatronics
References :
1. Robotic Engineering – An Integrated Approach
Richard D. Klafter, Thomas A. Chmielewski, Michael Negin
2. NPTEL, Mechanical Engineering,
Robotics - Prof. P. Sheshu, Prof. Kurien Issac, Prof. C.
Amarnath, Prof. Bhartendu Seth, Asst. Prof. P.S.Gandhi, IIT,
Bombay
3. Introduction to Robotics – S. K. Saha, Tata McGraw Hill
19 dec 2017
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3. VELOCITY SENSOR - Tachometer
In case of tachometer it is necessary that:
1. Voltage vs. Speed should be linear
2. Output voltage must be free of ripple
3. Should be light in weight
5. Hall Effect Sensor
This component can be used in a circuit to open
and close a contact when exposed to
alternating N and S poles of a magnet. Will also
work if exposed to the same pole on alternative
sides of the sensor.
Many uses including:
Counting revolutions, oscillations, or sequences
Turning LEDs, alarms, or other devices on/off
Detecting presence of magnetized materials
Intruder/theft alarms
Monitor start/stop of a moving process
Robotic effects and magic tricks!
Source: http://www.lessemf.com
7. Accelerometers
The piezoelectric accelerometer is
based on a property exhibited by
certain crystals where a voltage is
generated across the crystal when
stressed. For accelerometers, the
principle is shown in figure. Here, a
piezoelectric crystal is spring-
loaded with a test mass in contact
with the crystal. When exposed to
an acceleration, the test mass
stresses the crystal by a
force (F = ma), resulting in a
voltage generated across the
crystal. A measure of this voltage
is then a measure of the
acceleration.
http://zone.ni.com/devzone/cda/ph/p/id/284
8. Accelerometer
Digital Accelerometer
Example: LIS302 is a 3-axis digital accelerometer
■ 2.16V to 3.6V supply voltage
Application
■ Free-Fall detection
■ Motion activated functions
■ Gaming and virtual reality input devices
■ Vibration monitoring and compensation
Description
The LIS302DL is an ultra compact low-power
three axes linear accelerometer. It includes a
sensing element and an IC interface able to
provide the measured acceleration to the
external World
http://www.st.com/
11. External Sensors
Proximity Sensors -
Non-contact type
- reflected light sensors
*two different object positions produce same
voltage – giving incorrect value
* ambient light
* sensitivity depends on reflectivity of object
* errors due to variations in light-source output,
drift in detector characteristics, environmentally aused
changes in reflectivity of object
17. Digital Sensors for Motion
Measurement
Ref: Introduction to Mechatronics and Measurement Systems, Histand & Alciatore,
1999 McGraw Hill
18.
19.
20. Digital Encoder
• A digital optical encoder converts motion into
a sequence of digital pulses.
• By decoding a set of bits, the pulses can be
converted to relative or absolute position
measurements.
• Encoders have both linear and rotary
configurations.
22. Absolute encoder
• The optical disk of the absolute encoder is designed
to produce a digital word that distinguishes N distinct
positions of the shaft.
23. Incremental encoder
The incremental encoder, sometimes called a relative
encoder, consists of two tracks and two sensors whose
outputs are called channels A and B. As the shaft rotates,
pulse trains occur on these channels at a frequency
proportional to the shaft speed, and the phase relationship
between the signals yields the direction of rotation.
An LVDT transformer is exited with a fixed frequency sine wave. The distance of displacement of the movable core will change the amplitude of the transformer output which is is converted to a dc voltage by the LT1967 True RMS converter. The direction of the core movement is indicated by the phase shift of the sine wave and is detected by a simple phase comparator circuit.
