mechatronics lecture 2(1)
DESCRIPTION
mech lecture 2TRANSCRIPT
Lecture 2
Dan Zhang, PhD, PEng, FEIC, FCSME, SMIEEE
Faculty of Engineering and Applied Science University of Ontario Institute of Technology
MECE 3390U
Mechatronics
The term mechatronics was ‘invented’ by a Japanese engineer in 1969, as a combination of ‘mecha’ from mechanisms and ‘tronics’ from
electronics. Mechatronics is a co-ordinated, and concurrently
developed, integration of mechanical engineering with electronics and intelligent computer control in the design and manufacture of products and processes.
What is Mechatronics?
•Automobiles:
–Antilock Brakes (ABS)
–Cruise Control
–Active Suspension
•Consumer Products:
–Auto-Focus Camera
–Clothes Dryer
–Computer Printer
•Robotics
•Medical Applications
Defence Application…
Example Applications
MTRAN3 Modular Robot
A system can be thought of as a box or block diagram
which has an input and an output and where we are
not concerned with what goes on inside the box but
only the relationship between the output and the
input.
Systems
Measurement systems can, in general, be
considered to be made up of three basic
elements: sensor, signal conditioner and
display.
Measurement systems
Mechatronics: An integrated and optimal design
of a mechanical system and its embedded
control system
CD player/ Hard disk
Robots
Production machines
There are two basic forms of control system: open
loop and closed loop. With closed loop there is
feedback, a system containing a comparison element,
control element, correction element, process
element and the feedback involving a measurement
element.
Control systems
Open Loop System
A control system is an interconnection of
components. Each component is represented
by a block in a diagram.
Without feedback
Desired
output
Controller Plant
Actuating
signal
Control
signal
Plant
output
Actuator
Relatively simple.
Low cost.
Good reliability.
Inaccurate since there is no correction for
error.
Open-Loop Systems
Elements of a Closed-Loop System
Relatively accurate.
More complex.
More costly.
Less reliable due to the larger number of
components.
Closed-Loop Systems
Example 1 – Household Furnace
If temperature inside the house is below the
desired temperature, furnace turns on until the
temperature inside the house is slightly higher
than the desired temperature
temperature
sensor
Desired
temp.
+
-
Error
signal
gain house
heat Gas valve
signal temp.
furnace
Example 2 – Cruise Control
If the vehicle speed is lower than the desired speed the controller acts on the throttle to increase speed
If the vehicle speed is higher than the desired speed, the controller acts on the throttle to reduce speed
speedometer
Desired
speed
+
-
Error
signal
controller vehicle
traction
force
throttle speed
engine
Signals
Signal: transmission of information
Represented by
Systems
System: representation of a process generally
has two signals
Input
Output
Example: Body Temperature Adjusting
Example: Shaft speed control
Closed-loop vs open-loop control systems
Advantage of the closed-loop control system is the fact that the use of feedback makes the system response relatively
insensitive to external disturbances and internal variations in system parameters.
It is thus possible to use relatively inaccurate and inexpensive components to obtain the accurate control of a given plant, whereas doing so is impossible in the open-loop case.
From the point of view of stability, The open-loop control system is easier to build because
system stability is not a major problem.
The stability is a major problem in the closed-loop control system, which may tend to overcorrect errors that can cause oscillations of constant or changing amplitude.
Sequential control is used when the control is
such that actions are strictly ordered in a time
or event driven sequence.
Examples: dishwasher, washing machine
Sequential Controllers
Example: Washing Machine
A microprocessor is a digital electronic
component with miniaturized transistors on a
single semiconductor integrated circuit (IC).
Many simple systems use an embedded
microcontroller.
Microprocessor-Based Controllers
A Programmable Logic Controller(PLC) is a
microprocessor-based controller which uses
programmable memory to store instructions and to
implement functions such as logic, sequence, timing,
counting, and arithmetic to control events.
Programmable Logic Controller
Example: Automatic Camera
Example: engine management system
The response of a system is not instantaneous.
The response is a function of time.
In order to know how systems will respond to
a known input, we need to devise models that
relate the output to the input.
Response of Systems
Mechatronics System Design
1. Mechanism design (Kinematic design)
2. Establish control objectives—Specification (Control systems)
1. Qualitative
2. Quantitative
3. Establish system configuration and select sensors and actuators---design starts
4. Obtain a model of the plant, the actuator and the sensor
1. Analytic
2. From measured data (system identification)
5. Design a controller
1. Select technique
2. Choose parameters
6. Integration