3. Sensors & Actuators
Sensor:
A transducer device which converts energy from one form to another for any
measurement or control purpose. Sensors acts as input device
Eg. Hall Effect Sensor which measures the distance between the cushion and
magnet in the Smart Running shoes from adidas
Actuator:
A form of transducer device (mechanical or electrical) which converts signals to
corresponding physical action (motion). Actuator acts as an output device
Eg. Micro motor actuator which adjusts the position of the cushioning element
in the Smart Running shoes from adidas
4. Transducer
A transducer is a device that converts energy
from one form to another.
Physical form: thermal, electric,
mechanical, magnetic, chemical, and
optical
Energy converter
Example:
Microphone : Converts sound to electrical signal
Speaker : Converts electrical signal to sound
Antenna : Converts electromagnetic energy
into electricity and vice versa
Strain gauge : Converts strain to electrical
5. Sensor, Actuator Vs Transducer
• The word transducer is the collective term used for
both sensors and actuators which can be used to
sense a wide range of different energy forms such as
movement, electrical signals, radiant energy, thermal
or magnetic energy etc.. and Actuators which can be
used to switch voltage or current to mechanical &
physical action.
7. Parameters Transducers Sensors Actuators
Definition Converts energy from
one form to another
Converts various forms
of energy into electrical
signals.
Converts electrical
signals into various
forms of energy,
typically mechanical
energy
Domain Can be used to
represent a sensor as
well as an actuator.
It is an input transducer. It is an output
transducer.
Function Can work as a sensor
or an actuator but not
simultaneously
Used for quantifying
environmental stimuli
into signals.
Used for converting
signals into proportional
mechanical orelectrical
outputs
Examples Any sensor or
actuator
Humidity sensors,
Temperature sensors,
Anemometers
Manometers ,
Accelerometers ,Gas
sensors and others
Motors ,
Force heads
Differences between transducers, sensors, and actuators.
8. Sensor
Definition: A sensor is a device which senses the physical phenomena
around it and converts to measurable form.
Ex: Temperature Sensor
In general Sensors are used as input devices to monitor any physical
phenomenon like temperature, pressure, light, etc.
8
9. Examples of Sensors
Temperature and Humidity
sensor – DHT22
Gas (LPG, CH4, and CO) detector
sensor - MQ-5
Ultrasonic sensor - HC-SR04 CMOS Camera
PIR sensor Rain detector sensor Fire detector sensor
9
11. Sensor Characteristics
(considerations)
11
Static characteristics
After steady state condition, how the output of a sensor change
in response to an input change
Dynamic characteristics
The properties of the system’s transient response to an input
12. Static characteristics
12
Accuracy:
• Accuracy is a measure of how close the measured value of a Sensor to
the True or ideal value.
• It is the error between the real and measured value.
13. Precision/repeatability/reproducibility
• It is the measure of consistency or repeatability of measurements i.e.
successive readings in an instrument should not differ.
OR
• It is the deviation between measurements in a sequence under same
conditions
Example: Measure a steady state signal many times. In this case if
the values are close together then it has a high degree of precision or
repeatability. The values do not have to be the true values just grouped
together.
14. Resolution:
14
• The resolution of a sensor is a smallest change it can detect in the
quantity that it is measuring.
• The resolution of a sensor with digital output is usually the smallest
resolution the digital output is capable of processing.
• The more is the resolution of a sensor, the more accurate is its precision.
• A sensor’s accuracy does not depend on its resolution.
15. Sensitivity
15
1.It is the ratio of change in output (or response) of the instrument to
change in input or measured variable
2. A higher sensitivity indicates that the system can respond to even
the
smallest input.
Ex: Jewellery weighing machine
16. Linearity
• Linearity is the maximum deviation between the measured values of a
sensor from ideal curve.
• In the below figure if the is sensor is linear ,then characteristics will be like
blue colour line ideal curve.
• If sensor is non linear then characteristics will be like green colour line
measured curve
17. 17
Drift:
The difference in the measurements of sensor from a specific
reading when kept at that value for a long period of time
Range:
•Gives the highest and the lowest value of the physical quantity
within which the sensor can actually sense.
•Beyond this value there is no sensing or no kind of response
•Ex: If a thermometer can measure between -400
C to 1200
C
So, the range is -400
C to 1200
C
19. Passive Sensor
19
• It does not need any additional energy sources and it
directly generates an electric signal in response to an
external stimuli.
• Example: Thermo couple which generates its own voltages
output when exposed to heat.
20. Active Sensor
20
• Require external power called excitation signal and
sensor modify excitation signal to provide the output
Example: Strain Gauge
21. Analog Sensor
• Analog sensors produce a continuous output signal or
voltage which is generally proportional to the quantity being
measured.
Example: analog Temperature sensor, LDR, analog
pressure sensor, A LDR shows continuous variation in its
resistance as a function of intensity of light falling on it.
LDR
22. Digital Sensor
• Digital Sensors produce discrete digital output signals or voltages
that are digital representation of the quantity being measured.
• Digital sensors produce a binary output signal in the form of logic
“1” or logic “0” , “ON” or “OFF”.
• Digital signal only produces discrete (non-continuous) values, which
may be output as a single “bit” (serial transmission), or by
combining the bits to produce a single “Byte” output (parallel
transmission).
• Example: Digital temperature sensor (DHT22)
23. Scalar Sensor
23
• Scalar sensors produce output signal or voltage which is
generally proportional to the magnitude of the quantity
being measured.
• Physical quantities such as temperature, pressure, color,
strain etc. are all scalar quantities as only their magnitude is
sufficient to convey an information.
For example, the temperature of a room can be measured
using a thermometer or thermocouple which responds
to temperature changes irrespective of the orientation
of the sensor or its direction.
Example: Temperature, gas, strain, color, and smoke sensors
24. Vector Sensors
• Vector Sensors produce output signal or voltage which is
generally proportional to the magnitude, direction, as well
as the orientation of the quantity being measured.
• Physical quantities such as sound, image, velocity,
acceleration, orientation etc. are all vector quantities, as only
their magnitude is not sufficient to convey the complete
information.
Example: the acceleration of a body can be measured
using an accelerometer, which gives the components
of acceleration of the body with respect to the x, y, z
coordinate axes.
Example sensors : Accelerometer, gyroscope, magnetic field
and motion detector sensors.
25. Errors in Sensors (sensor deviations)
Hysteresis Error:
• It is the difference in output when input is varied in two ways- increasing
and decreasing..
•Typically in analog sensors, magnetic sensors, heating of metal strips.
26. Quantization error
• If the sensor has a digital output, the output is essentially an
approximation of the measured property. This error is called
Quantization error.
27. Aliasing errors
•If the signal is monitored digitally, the sampling frequency can
cause a dynamic error, or if the input variable or added noise
changes periodically at a frequency proportional to the multiple
of the sampling rate, aliasing errors may occur
28. LDR (Light Dependent Resistor)
•A Light Dependent Resistor (LDR) or a photo resistor is a
device whose resistivity is a function of the incident
electromagnetic radiation.
•LDRs are light sensitive devices.
•also called as photo conductors, photo conductive cells or
simply photocells.
29. DHT22:
Temperature: A measure of the warmth or coldness of an object
or substance with reference to some standard value.
Humidity: A quantity representing the amount of water vapour in
the atmosphere.
DHT22: Digital Humidity Temperature sensor
1.The DHT-22 (also named as AM2302) is a digital-output relative humidity
and temperature sensor. It uses a capacitive humidity sensor and a
thermistor to measure the surrounding air, and spits out a digital signal on
the data pin.
Features:
•The range of operating voltage ( ) is 3 V to 5 V power.
•It measures temperature in a range of -40°C to +125°C with an accuracy of ±
0.5 degrees.
•The measuring range for humidity is from 0 to 100% with an accuracy of 2-5%.
•The maximum operating current for DHT22 sensor is 2.5mA.
•The sampling rate for DHT22 sensor is 0.5 Hz. It takes measurement once
every 2seconds.
30. Pin Description:
The DHT22 sensor is very simple and easy to use. It has
only four pins.
•Vcc is the power pin. Apply voltage in a range of 3.5 V
to 5.0 V at this pin.
•Data Out is the digital output pin. It sends out the value
of measured temperature and humidity in the form of
serial data.
•N/C is a not connect pin.
•GND: Connect the GND pin to main ground.
31. PIR SENSOR
•A passive infrared sensor (PIR sensor) is an electronic
sensor that measures infrared (IR) light radiating from objects
in its field of view.(range)
•PIR sensors are commonly used in security alarms and
automatic lighting applications.
•PIR sensors detect general movement, but do not give
information on who or what moved.
PIN DESCRIPTION
•Pin1 corresponds to the drain terminal of the device, which
connected to the positive supply 5V DC.
•Pin2 corresponds to the source terminal of the device, which
connects to the ground terminal via a 100K or 47K resistor. The
Pin2 is the output pin of the sensor.
•Pin3 of the sensor connected to the ground.
32. •The PIR sensor itself has two slots in it, each slot is made of
a special material that is sensitive to IR.
•When the sensor is idle, both slots detect the same amount
of IR
the ambient amount radiated
from the room or walls or outdoors.
•When a warm body like a human or animal passes by, it first
intercepts one half of the PIR sensor, which causes a positive
differential change between the two halves.
•When the warm body leaves the sensing area, the reverse
happens, whereby the sensor generates a negative
differential change. These change pulses are what is
detected.
34. An ultrasonic sensor is an electronic device that measures
the distance of a target object by emitting ultrasonic sound
waves, and converts the reflected sound into an electrical
signal.
•The HC-SR04 is a type of ultrasonic sensor which uses sonar to find out the
distance of the object from the sensor.
•It provides an outstanding range of non-contact detection with high accuracy
& stable readings.
• It includes two modules like ultrasonic transmitter & receiver.
•This sensor is used in a variety of applications like measurement of direction
35. HC-SR04 Ultrasonic Sensor Pin Configuration
This sensor includes four pins and the pin configuration of this
sensor is discussed below.
•Pin1 (Vcc): This pin provides a +5V power supply to the
sensor.
•Pin2 (Trigger): This is an input pin, used to initialize
measurement by transmitting ultrasonic waves by keeping this
pin high for 10us.
•Pin3 (Echo): This is an output pin, which goes high for a
specific time period and it will be equivalent to the duration of
the time for the wave to return back to the sensor.
•Pin4 (Ground): This is a GND pin used to connect to the GND
of the system.
36. Features:
•The power supply used for this sensor is +5V DC
•Dimension is 45mm x 20mm x 15mm
•Quiescent current used for this sensor is <2mA
•The input pulse width of trigger is10uS
•Operating current is 15mA
•Measuring angle is 30 degrees
•The distance range is 2cm to 800 cm
•Resolution is 0.3 cm
•Effectual Angle is <15°
•Operating frequency range is 40Hz
Accuracy is 3mm
37. Description
The HC-SR04 Ultrasonic sensor comes with four pins
namely Vcc pin, Trigger pin, Echo pin, & Ground pin. This
sensor is used to measure the accurate distance between
the target and the sensor. This sensor mostly works on the
sound waves.
When the power supply is given to this module, it
generates the sound waves to travel throughout the air to
hit the necessary object. These waves strike and come
back from the object, then collects by the receiver module.
38. Here both the distance as well as time has
taken is directly proportional because the
time taken for more distance is high. If the
trigger pin is kept high for 10 µs, then the
ultrasonic waves will be generated which will
travel at the sound speed. So it creates eight
cycles of sonic burst that will be gathered
within the Echo pin. This ultrasonic sensor is
interfaced with Arduino to gauge the
necessary distance between sensor &
object. The distance can be calculated using
the following formula.
S = (V x t)/2
39. Where the ‘S’ is the required distance
‘V’ is the sound’s speed
‘t’ is the time taken for sound waves to return back after
striking the object.
The actual distance can be calculated by dividing its value
with 2 as the time will be twice once the waves travel and get
back from the sensor.
40. Applications:
The applications of HC-SR04 sensor include the following,
•This sensor is used to measure speed as well as the direction
between two objects
•It is used in wireless charging
•Medical ultrasonography
•This is used to detect objects & avoid obstacles using robots
such as biped, path finding, obstacle avoidance, etc.
•Depth measurement
•Humidifiers
•This sensor is used to plot the objects nearby the sensor by
revolving it
•Non-destructive testing
•By using this sensor depth of pits, wells can be measured by
transmitting the waves through water.
•Embedded system
•Burglar alarms
41. Actuator
A actuator is a device which takes input as electrical signal or energy
and produces physical phenomenon like force or motion
In general Actuators are used as output devices to produce any
physical phenomenon
4
1
Actuator
Energy Signal
Motion / Force
42. Actuator….
A control signal is input to an actuator and an energy
source is necessary for its operation
Example: Electric motor, solenoid, hard drive stepper
motor, comb drive, hydraulic cylinder, piezoelectric
actuator, and pneumatic actuator
42
DC MOTOR
43. I/O Devices - Light Emitting Diode (LED)
• Light Emitting Diode (LED) is an output device for visual
indication in any embedded system
• LED can be used as an indicator for the status of various
signals or situations. Typical examples are indicating the
presence of power conditions like ‘Device ON’, ‘Battery low’
or ‘Charging of battery’ for a battery operated handheld
embedded devices
• LED is a p-n junction diode and it contains an anode and a
cathode. For proper functioning of the LED, the anode of it
should be connected to +ve terminal of the supply voltage
and cathode to the –ve terminal of supply voltage
• The current flowing through the LED must limited to a value
below the maximum current that it can conduct. A resister is
used in series between the power supply and the resistor to
limit the current through the LED
R
GND
Vcc
44. 7-Segment LED Display
• The 7 – segment LED display is an output device for displaying alpha
numeric characters
• It contains 8 light-emitting diode (LED) segments arranged in a
special form. Out of the 8 LED segments, 7 are used for displaying
alpha numeric characters
• The LED segments are named A to G and the decimal point LED
segment is named as DP
• The LED Segments A to G and DP should be lit accordingly to display
numbers and characters
• The 7 – segment LED displays are available in two different
configurations, namely; Common anode and Common cathode
• In the Common anode configuration, the anodes of the 8 segments
are connected commonly whereas in the Common cathode
configuration, the 8 LED segments share a common cathode line
45. 7-Segment LED Display
Based on the configuration of the 7 – segment LED unit, the LED
segment anode or cathode is connected to the Port of the
processor/controller in the order ‘A’ segment to the Least significant
port Pin and DP segment to the most significant Port Pin.
The current flow through each of the LED segments should be limited
to the maximum value supported by the LED display unit
The typical value for the current falls within the range of 20mA
The current through each segment can be limited by connecting a
current limiting resistor to the anode or cathode of each segment
A
B
C
D
E
F
G
DP
Common Cathode LED Display
Cathode
A
B
C
D
E
F
G
DP
Common Anode LED Display
Anode
46. Push button switch
Push Button switch is an input device
Push button switch comes in two configurations,
namely ‘Push to Make’ and ‘Push to Break’
The switch is normally in the open state and it makes
a circuit contact when it is pushed or pressed in the
‘Push to Make’ configuration
In the ‘Push to Break’ configuration, the switch is
normally in the closed state and it breaks the circuit
contact when it is pushed or pressed
The push button stays in the ‘closed’ (For Push to
Make type) or ‘open’ (For Push to Break type) state as
long as it is kept in the pushed state and it
breaks/makes the circuit connection when it is released
Push button is used for generating a momentary pulse
48. Pi Camera
•There are now several official Raspberry Pi camera modules. The
original 5-megapixel model was released in 2013, it was followed by an 8-
megapixel Camera Module 2 which was released in 2016. The latest
camera model is the 12-megapixel Camera Module 3 which
was released in 2023. The original 5MP device is no longer available
from Raspberry Pi.
•All of these cameras come in visible light and infrared versions, while the
Camera Module 3 also comes as a standard or wide FoV model for a
total of four different variants.
•Camera Module 3 (left) and Camera Module 3 Wide (right)
49. Connecting the Camera
•The flex cable inserts into the connector labelled CAMERA on the
Raspberry Pi, which is located between the Ethernet and HDMI ports.
•The cable must be inserted with the silver contacts facing the HDMI port.
• To open the connector, pull the tabs on the top of the connector
upwards, then towards the Ethernet port.
•The flex cable should be inserted firmly into the connector, with care
taken not to bend the flex at too acute an angle.
•To close the connector, push the top part of the connector towards the
HDMI port and down, while holding the flex cable in place.
50. Hardware Specification
Camera Module v1
Camera Module v2 Camera Module 3 Camera Module 3 Wide HQ Camera
Net price $25 $25 $25 $35 $50
Size Around 25 × 24 × 9
mm
Around 25 × 24 × 9
mm
Around 25 × 24 × 11.5
mm
Around 25 × 24 × 12.4
mm
38 x 38 x 18.4mm (excluding
lens)
Weight 3g 3g 4g 4g
Still resolution 5 Megapixels 8 Megapixels 11.9 Megapixels 11.9 Megapixels 12.3 Megapixels
Video modes 1080p30, 720p60 and
640 × 480p60/90
1080p47, 1640 ×
1232p41 and 640 ×
480p206
2304 × 1296p56, 2304
× 1296p30 HDR, 1536
× 864p120
2304 × 1296p56, 2304
× 1296p30 HDR, 1536
× 864p120
2028 × 1080p50, 2028 ×
1520p40 and 1332 × 990p120
Sensor OmniVision OV5647 Sony IMX219 Sony IMX708 Sony IMX708 Sony IMX477
Sensor resolution 2592 × 1944 pixels 3280 × 2464 pixels 4608 x 2592 pixels 4608 x 2592 pixels 4056 x 3040 pixels
Sensor image area 3.76 × 2.74 mm 3.68 x 2.76 mm (4.6
mm diagonal)
6.45 x 3.63mm
(7.4mm diagonal)
6.45 x 3.63mm
(7.4mm diagonal)
6.287mm x 4.712 mm (7.9mm
diagonal)
Pixel size 1.4 µm × 1.4 µm 1.12 µm x 1.12 µm 1.4 µm x 1.4 µm 1.4 µm x 1.4 µm 1.55 µm x 1.55 µm
Optical size 1/4" 1/4" 1/2.43" 1/2.43" 1/2.3"
Focus Fixed Adjustable Motorized Motorized Adjustable
Depth of field Approx 1 m to ∞ Approx 10 cm to ∞ Approx 10 cm to ∞ Approx 5 cm to ∞ N/A
Focal length 3.60 mm +/- 0.01 3.04 mm 4.74 mm 2.75 mmm Depends on lens
Horizontal Field of
View (FoV)
53.50 +/- 0.13 degrees 62.2 degrees 66 degrees 102 degrees Depends on lens
Vertical Field of View
(FoV)
41.41 +/- 0.11 degrees 48.8 degrees 41 degrees 67 degrees Depends on lens
Focal ratio (F-Stop) F2.9 F2.0 F1.8 F2.2 Depends on lens
Maximum exposure
times (seconds)
6 11.76 112 112 670.74
Lens Mount N/A N/A N/A N/A CS- or M12-mount
54. Electric Linear
Actuator
• Powered by electrical signal.
• Mechanical device containing linear guides, motors, and drive
mechanisms
• Converts electrical energy into linear displacement
• Used in automation applications including electrical bell, locking
doors, and braking machine .
https://www.youtube.com/watch?
v=I2q1gFYSz2w
55. Fluid Power Linear Actuator
55
• Powered by hydraulic fluid, gas, or differential air pressure
• Mechanical devices have cylinder and piston mechanisms
Produces linear displacement
• Primarily used in automation applications including clamping
and welding.
https://www.youtube.com/watch?v=ClOXkkVDIiY
56. Electric Rotary Actuator
• Powered by electrical signal
• Converts electrical energy into rotational motion
• Applications including quarter-turn valve windows and
robotics
56
https://www.youtube.com/watch?v=0KrmX2E4VNs
57. Fluid Power Rotary Actuator
• Powered by fluid, gas, or differential air pressure
• Consisting of gearing, and cylinder and piston mechanisms
Converts hydraulic fluid, gas, or differential air pressure into
rotational motion
• Primarily applications of this actuator are opening and closing
dampers, doors, and clamping.
https://www.youtube.com/watch?v=yUaxZCnhqQs
58. Linear Chain Actuator
• Mechanical devices containing sprockets and sections of chain
• Provides linear motion by the free ends of the specially
designed chains
• Primarily used in motion control applications.
58
https://www.youtube.com/watch?v=J3SUM1u47iU
https://www.youtube.com/watch?v=diXEm9aw1Dc
59. Manual Linear Actuator
59
• Provides linear displacement through the translation of
manually rotated screws or gears
• Consists of gearboxes, and hand operated knobs or wheels
• Primarily used for manipulating tools and work pieces
60. Manual Rotary Actuator
Provides rotary output through the translation of manually
rotated screws, levers, or gears
Consists of hand operated knobs, levers, hand wheels and
gearboxes
Primarily used for the operation of valves.
61. • Actuator Considerations
• Picking powered actuators entails knowing such parameters as
loading, stroke length, timing, etc. Many of these parameters
have limits as to speed and force and narrowing the selection
in this manner can bring the appropriate technology into focus.
Other considerations include the kinds of services available.
Hydraulic actuators provide large forces in small sizes but need
a source of hydraulic pressure.
• Air-powered actuators use readily available factory air but
there is a tradeoff to be made due to their bigger sizes for
equivalent forces. Electric actuators have the advantages of
better controllability and are less prone to leaking. Electric
actuators do tend to have appreciably higher first costs. They
also have advantages in outdoor installation where air systems
can freeze.
62. •Pneumatic actuators for valves fall into two camps: double acting and
spring return. Double-acting means that air pressure moves the valve in
both directions. Spring return means that a spring is used on one stroke
which the air pressure must overcome to open (or close) the valve. It
makes a difference as to how the valve will behave upon a loss of air
pressure. A spring return valve will return the valve to its unpowered state
upon an air-pressure loss. Hydraulic actuators can be fitted in similar
fashions.
•For motion control, some linear actuators are designed for
micropositioning and rely on piezo crystals to produce very small, high-
resolution motions which are useful in the nanometer world of optics,
semiconductor manufacturing, etc. More typically, belt and ball screw-
based actuators impart motion to positioning stages and the like to
achieve repeatability measured in thousandths of an inch. A linear
actuator can be used with hand controls, such as in dental chairs.
63. Important Actuator Attributes
Mounting Configuration
This describes the way in which the actuator attaches to the actuated
device. Valve actuators sometimes mount directly to the valve flange
or use trunnion mounts to give access to valve stem packing glands.
Actuation Features
Selecting double acting or spring return here will choose the failure
mode of the actuator upon loss of air or hydraulic pressure.
Output Torque
Output torque applies to both electric and fluid powered rotary
actuators and describes the rotational force the actuator can apply to
the valve to close it. It is usually expressed in in-lb. or Nm.
64. Maximum Extension/Retraction/Holding Force
These attributes apply to linear actuators and may sometimes be expressed as a
single value such as maximum thrust force. They are usually given in lbf or N.
Maximum Speed
For powered actuators, this is the highest linear or rotational speed the unit can
deliver. It is usually expressed as rpm for rotary actuators and as in/sec for linear
devices.
Enclosure Protection Rating
Electrical enclosures are specified in accordance with NEMA or IEC criteria for the
environment and ingress protection.
65. Weight: The physical weight of actuators limits its application scope. For
example, the use of heavier actuators is generally preferred for industrial
applications and applications requiring no mobility of the IoT deployment. In
contrast, lightweight actuators typically find common usage in portable systems in
vehicles, drones, and home IoT applications. It is to be noted that this is not
always true. Heavier actuators also have selective usage in mobile systems, for
example, landing gears and engine motors in aircraft.
Actuator Characteristics/ Considerations
66. Power Rating: This helps in deciding the nature of the application with which
an actuator can be associated. The power rating defines the minimum and
maximum operating power an actuator can safely withstand without damage to
itself. Generally, it is indicated as the power-to-weight ratio for actuators. For
example, smaller servo motors used in hobby projects typically have a
maximum rating of 5 VDC, 500 mA, which is suitable for an operations-driven
battery-based power source. Exceeding this limit might be detrimental to the
performance of the actuator and may cause burnout of the motor. In contrast to
this, servo motors in larger applications have a rating of 460 VAC, 2.5 A, which
requires standalone power supply systems for operations. It is to be noted that
actuators with still higher ratings are available and vary according to application
requirements.
67. Torque to Weight Ratio: The ratio of torque to the weight of the
moving part of an instrument/device is referred to as its torque/weight
ratio. This indicates the sensitivity of the actuator. Higher is the weight
of the moving part; lower will be its torque to weight ratio for a given
power.
• Stiffness and Compliance: The resistance of a material against
deformation is known as its stiffness, whereas compliance of a material
is the opposite of stiffness. Stiffness can be directly related to the
modulus of elasticity of that material. Stiff systems are considered more
accurate than compliant systems as they have a faster response to the
change in load applied to it. For example, hydraulic systems are
considered as stiff and non-compliant, whereas pneumatic systems are
considered as compliant
