Dr. S.H. Upadhyay Mechanical & Industrial Engineering Deptt. IIT Roorkee
CWS-25; MTE-25; ETE-50 1.Introduction to mechatronics and mechatronics approach; measurement system; control systems; microprocessor based controllers. 2.Sensors and transducers:Performance terminology; photoelectric transducers; flow transducers; optical sensors and transducers; semiconductor lasers, selection of sensors, mechanical/electrical switches, inputting data by switches. 3.Actuators and mechanisms: Actuation systems; pneumatic and hydraulic systems; process control valves; rotary actuators; mechanical actuation systems; electrical actuation systems
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4. Signal conditioning: Signal conditioning; filtering
digital signals; Multiplexers; Data acquisition; Digital signal processing; Pulse modulation; data Presentation systems. 5. Microprocessors and microcontrollers: Control; microcomputer structure; Microcontrollers; applications; programmable logic controllers. 6. Modeling & system response: Mathematical models; Mechanical, electrical, hydraulic and thermal Systems; Dynamic response of systems; Transfer function and frequency response; closed loop controllers; MATLAB as development tool. 7. Design and Mechatronics: Input/output system; Computer based modular design; System validation; Remote monitoring and control; Designing; Possible design solutions; Case studies.
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Mechatronics: Bolton, W., Longman Introduction to Mechatronics: D.G. Alciatore & Michael B. Histand; Tata Mc Graw Hill Mechatronic system Design; Shetty Dedas, Kolk and Richard Mechatronic handbook: Bishop; CRC press
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“The name [mechatronics] was coined by Ko Kikuchi, now president of Yasakawa Electric Co., Chiyoda-Ku, Tokyo.”
“The word, mechatronics is composed of mecha from mechanics and tronics from electronics. In other words, technologies and developed products will be incorporating electronics more and more into mechanisms, intimately and organically, and making it impossible to tell where one ends and the other begins.” Mechanics
mecha Mechatronics
Eletronics
tronics 5
Harashima, Tomizuka, and Fukada, 1996 “Synergistic integration of mechanical engineering with electronics and intelligent computer control in the design and manufacturing of industrial products and processes.”
Auslander and Kempf, 1996 ◦ Mechatronics is the application of complex decision making to the operation of physical systems.
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Shetty and Kolk in 1997 “Mechatronics is a methodology used for the optimal design of electromechanical products.”
W. Bolton, 1995 “Integration mechanical
of electronics, engineering.”
control
engineering,
and
S. Ashley, 1997 “Synergistic use of precision engineering, control theory, computer science, and sensor and actuator technology to design improved products and processes.”
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D. G. Alciatore and M. B. Histand,1998 “Field of study involving the analysis, design, synthesis, and selection of systems that combine electronics and mechanical components with modern controls and microprocessors.”
Mechatronics is generally ◦ recognized worldwide as a vibrant area of study. ◦ Undergraduate and graduate programs in mechatronic engineering are now offered in many universities. ◦ Refereed journals are being published and dedicated conferences are being organized and are generally highly attended.
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Implementing electronics control in a mechanical system. Enhancing existing mechanical design with intelligent control. Replacing mechanical component with a electronic solution.
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Mechanical Engineering
Electrical Engineering
Computer Engineering
Computer/Information Systems Mechanical Systems
Information Systems
Mechatrnoics Computer Systems
Electrical Systems
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The need
Analysis of problem
Preparation of Specification
Generation of possible solutions
Selection of a suitable solution
Production of a detailed design
Production of working drawings 11
TRADITIONAL DESIGN: The temperature control for a domestic central heating system has been the bi-metallic thermostat of a closed loop control system. The bending of bi-metallic strip changes as the temperature changes and is used to operate an on/off switch for the heating system. The bi-metallic thermostat is comparatively crude and the temperature is not accurately controlled; also devising a method for having different temperatures at different times of the day is complex and not easily achieved.
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MECHATRONIC DESIGN: A mechatronic solution to the problem might be to use a microprocessor controlled system employing perhaps a thermo-diode as the sensor The microprocessor-controlled system can, however, cope easily with giving precision and programmed control. The system is much more flexible. This improvement in flexibility is a common characteristic of mechotronics systems when compared with traditional systems.
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Real life applications: THERMOSTAT
TRADITIONAL DESIGN
MECHATRONICS DESIGN
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TRADITIONAL THERMOSTAT DESIGN SECTIONAL VIEW
COMPONENTS OF THERMOSTAT
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CONVERSION TO MECHATRONIC DESIGN
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A PICKPICK-AND AND-PLACE ROBOT
The basic form of a Pick-and-Place robot unit is shown in the Figure (a).
The robot has three axes, about which the motion can occur i.e. rotation in a clockwise or counter clockwise direction of the unit on its base, arm extension or contraction and arm up and down; also the gripper can open and close.
These movements can be actuated by the use of pneumatic cylinders operated by solenoid-controlled valves with limit switches to indicate when a motion is completed.
Thus the clockwise rotation of the unit might result from the piston in a linear cylinder being extended and the counter clockwise direction by its retraction. Likewise the upward movement of the arm might result from the piston in a linear cylinder being extended and the downward motion from it retracting; the extension of the arm by the piston in another cylinder extending and its return movement by the piston retracting.
The gripper can be opened or closed by the piston in a linear cylinder extending or retracting. Figure (b)
Figure (a)
Figure (b)
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MECHATRONICS SOLUTION
Figure below shows how a micro controller could be used to control the solenoid valves and hence the movements of the robot unit.
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CAR PARK BARRIERS
As an illustration of a PLC, consider the coin-operated barriers for a car park. The in-barrier is to open when the correct money is inserted in the collection box and the out-barrier is to open when a car is detected at the car park side of the barrier. The Figure shows the types of valve systems that can be used to lift and lower the pivoted barriers. When a current flows through the solenoid of valve A, the piston in a cylinder moves upwards and causes the barrier to rotate about its pivot and raise to a let a car through. When the current through solenoid of valve A ceases, the return spring of the valve results in the valve position changing back to its original position. When the current is switched to through the solenoid of valve B the pressure is applied to lower the barrier. Limit switches are used to detect when the barrier is down and also when fully up. 19
MECHATRONICS SOLUTION PLC connections
Ladder diagram
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ADVANTAGES OF MECHATRONICS DESIGN
HIGH RESOLUTION & ACCURACY
REDUCES HOUSE HOLD HEATING COST
SELF CALIBRATING
FLEXIBLE DESIGN
ENVIRONMENTAL FRIENDLY
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In the late 1970s, the Japan Society for the Promotion of Machine Industry (JSPMI) classified mechatronic products into Class I: ◦ Primarily mechanical products with electronics incorporated to enhance functionality. ◦ Examples include numerically controlled machine tools and variable speed drives in manufacturing machines. Class II: ◦ Traditional mechanical systems with significantly updated internal devices incorporating electronics. The external user interfaces are unaltered. ◦ Examples include the modern sewing machine and automated manufacturing systems. 22
Class III: ◦ Systems that retain the functionality of the traditional mechanical system, but the internal mechanisms are replaced by electronics. ◦ An example is the digital watch. Class IV: ◦ Products designed with mechanical and electronic technologies through synergistic integration. ◦ Examples include photocopiers, intelligent washers and dryers, and automatic ovens.
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The enable technologies for each mechatronic product class illustrate the progression of electromechanical products in stride with developments in control theory, computation technologies, and microprocessors. Class I products were enabled by servo technology, power electronics, and control theory. Class II products were enabled by the availability of early computational and memory devices and custom circuit design capabilities. Class III products relied heavily on the microprocessor and integrated circuits to replace mechanical systems. Class IV products marked the beginning of true mechatronic systems, through integration of mechanical systems and electronics.
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It was not until the 1970s with the development of the microprocessor by the Intel Corporation that integration of computational systems with mechanical systems became practical. The electronic ignition system was one of the first mechatronic systems to be introduced in the automobile in the late 1970s.
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In several technical areas the integration of products or processes and electronics can be observed. This is especially true for mechanical systems which developed since about 1980. These systems changed from electro-mechanical systems with discrete electrical and mechanical parts to integrated electronic-mechanical systems with sensors, actuators, and digital microelectronics. These integrated systems, as seen in Table are called mechatronic systems , with the connection of MECHAnics and elecTRONICS.
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All these definitions agree that mechatronics is an interdisciplinary field , in which the following disciplines act together (see Figure) mechanical systems (mechanical elements, machines, precision mechanics); electronic systems (microelectronics, power electronics, sensor and actuator technology); and information technology (systems theory, automation, software engineering, artificial intelligence).
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Mechatronics: synergetic integration of different disciplines. 29
Some modern mechanical process like a power producing or a power generating machine. A primary energy flows into the machine and is then either directly used for the energy consumer in the case of an energy transformer, or converted into another energy form in the case of an energy converter. The form of energy can be electrical, mechanical (potential or kinetic, hydraulic, pneumatic), chemical, or thermal. Machines are mostly characterized by a continuous or periodic (repetitive) energy flow. For other mechanical processes, such as mechanical elements or precision mechanical devices, piecewise or intermittent energy flows are typical.
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Mechanical process and information processing develop towards mechatronic systems. 31
Division of Functions between Mechanics and Electronics Improvement of Operating Properties Addition of New Functions
General scheme of a (classical) mechanical-electronic system.
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•More features •Higher precession •User friendly •More flexible •Lower cost, Efficient •Environment friendly. •Smaller geometry. •More reliable. •Safer
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Above figure illustrates all the components in a typical mechatronic system. The actuators produce motion or cause some action. The sensors detect the state of the system parameters, input, and output; digital devices control the system; Conditioning and interfacing circuits provide connections between the control circuits and input/output devices and Graphical display provide visual feedback to users. 35
System can be thought of as a box 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.
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A fundamental part of many mechatronic system is a measurement system composed of the three basic parts shown in fig. The transducer is a sensing device that converts a physical input into an output, usually a voltage. The signal processor performs filtering, amplification, or other signal conditioning on the transducer output. The term sensor is often used to refer to the transducer or to the combination of transducer and signal processor. Finally recorder is an instrument, a computer, a hard-copy device or simply a display that maintains the sensor data for online monitoring or subsequent processing.
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Transducer
Signal processor
Recorder
Elements of a measurement system
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A black box used for making measurements. It has the input the quantity being measured and output the value of the quantity. Example: temperature measurement system Output
Input Temperature
Thermometer
Number on a scale
An example of a measurement system 39
The given figure is also another example of a measurement system. The thermocouple is a transducer that converts temperature to a small voltage. The amplifier increases the magnitude of the voltage; the A/D (analog-to-digital) converter is a device that changes the analog signal to a coded digital signal; The LED (light emitting diodes) display the value of the temperature.
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signal conditioner
display
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A control system can be thought of as a black box which is used to control its output to some particular value or particular sequence of value. For example, a domestic central heating control system has as its input the temperature required in the house and as its output the house at the temperature. i.e set the required temperature on the thermostat or controller and the heating furnace adjusts itself to pump water through radiators and so produce the required temperature in the house. 42
Input
Required temperature
Output
Central Heating System
Temper ature of the set value
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Open loop systems
Closed loop systems
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Open Loop System Input Decisi on to switch on or off
Switch
Electric fire
Electric power
Output
Temper ature change
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Comparison element + Input Switch Requir Deviation ed signal temper ature
Electric fire
Electric power
Output
A constant tempera ture
Measuring device
Feedback of temperature signal 46
Comparison element + Control unit Refer ence Error value signal
Correction unit
Process
Controlled variable
Measuring device
Measured value 47
Comparison element ◦ This compares the required or reference value of the variable condition being controlled with the measured value of what is being achieved and produces and error signal. It can be regarded as adding the reference signal, which is positive, to the measured value signal, which is negative in this case: Error signal= reference value signal – measured signal
value
Control element
◦ This decides what action to take when it receives an error signal.
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Correction element ◦ The correction element produces a change in the process to correct or change the controlled condition. ◦ Thus it might be a switch which switches on a heater and so increase the temperature of the process or a valve which opens and allows more liquid to enter the process.
Process element
◦ The process is what is being controlled. ◦ It could be a room in a house with temperature being controlled or a tank of water with its level being controlled.
Measurement element
◦ The measurement element produces a signal related to the variable condition of the process that is being controlled. 49
Controlled variable - the room temperature Reference value - the required room temperature Comparison element -the person comparing the measured value with the required value of the temperature Error signal -the difference between the measured and required temperatures Control unit -the person Correction unit -the switch on the fire Measuring device - a thermometer
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The digital integrated circuit (IC) called a microprocessors [Figure]. This revolution has occurred because the microprocessor brings the flexibility of program control and the computational power of a computer to bear on any problem. Microprocessors are now rapidly replacing the mechanical cam-operated controllers and being used in general to carry out control functions. 52
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In many simple systems there might be just an embedded microcontroller, this being a microprocessor with memory all integrated on one chip, which has been specifically programmed for the task concerned. microprocessor-based control systems are rapidly replacing many older control systems based on analog circuits or electromechanical relays One of the first microprocessor-base controllers made specifically for control applications was the programmable logic controller (PLC). 54
This is a microprocessor-based controller which used programmable memory to store instructions and to implement functions such as logic, sequence, timing counting and arithmetic to control events and can be readily reprogrammed for different tasks. A microprocessor by itself is not a computer; additional components such as memory and input/output circuits are required to make it operational
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Control program Inputs
Outputs
A B
P Controller
Q
C
R
D
S Programmable logic controller
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However, the microcontroller Figure, which is a close relative of the microprocessor, does contain all the computer functions on a single IC, Microcontroller lack some of the power and speed of the newer microprocessors, but their compactness is ideal for many control applications; most so-called microprocessor controlled devices, such as vending machines, are really using microcontrollers.
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Some specific reasons for using a digital, microprocessr design in control systems are the following: ◦ Low level signals from sensors once converted to digital, can be transmitted long distances virtually error-free. ◦ A microprocessor can easily handle complex calculations and control strategies. ◦ Long term memory is available to keep track of parameters in slow moving system. ◦ Changing the control strategy is easy by loading in a new program; no hardware changes are required. ◦ Microprocessor-base controllers are more easily connected to the computer network within an organization. This allows designer to enter program changes and read current system status from their desk terminals.
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When buying or ordering an MBC the following is a step by step procedure to simplify the process. ◦ 1. Specify Digital Inputs - List the Digital inputs and their voltage ranges. ◦ 2. Specify Analog Inputs - List the Analog inputs and their voltage swings. ◦ 3. Specify Data Inputs - List any Data inputs. ◦ 4. Specify On/Off Outputs - List On/Off outputs and their current ratings. ◦ 5. Specify Proportional Outputs - List Proportional outputs and their current ratings. ◦ 6. Specify Data Outputs - List the Data outputs. ◦ 7. Describe the desired MBC operation. Describe any monitoring, limiting or automation to be done by the MBC
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Engine speed Crankshaft position Spark timing feedback
Micro processor
Spark timing
Air Fuel Mixture Solenoid
Engine temperature Throttle position
Fuel injection valve
Mass air flow 63
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It has Analog and digital circuits, actuators, and microprocessors.
Working
sensors,
◦ User places an original in a loading bin and pushes a button to start the process. ◦ The original is transported to the platen glass ◦ A high intensity light source scans the original and transfers the corresponding image as a charge distribution to a drum. ◦ Blank piece of paper is retrieved from loading cartridge, and image is transferred onto the paper with an electrostatic deposition of ink toner powder that is heated to bond to the paper. ◦ A sorting mechanism then delivers the copy to an appropriate bin.
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Control
Sensors
Actuators
◦ Analogue circuits control the lamp, heater, and other power circuit. ◦ Digital circuit controls digital display, indicator lights, buttons, switches forming the user interface. ◦ Other digital ckt include logic ckts and microprocessor that coordinates all the functions of the machine.
◦ Optical sensors and micro switches detect the presence on absence of paper, its proper positioning, and whether or not door and latches are in proper position. ◦ Encoders used to track motor rotation. ◦ (servo/stepper) load and transport the paper, turn the drum and index the drum.
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Actuators
Sensors
Micro Controller
◦ Servo Motors ◦ ◦ ◦ ◦ ◦
IR Sensor for obstruction detection Bumper Sensor for obstruction detection Compass, for orientation detection Accelerometer, for tilt detection Ultrasonic sensor, for range detection.
◦ BASIC Stamp 2 module
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Growth in mechatronic systems will be fueled by the growth in the constituent areas. Advancements in traditional disciplines fuel the growth of mechatronics systems by providing “enabling technologies.” For example, the invention of the microprocessor had a profound effect on the redesign of mechanical systems and design of new mechatronics systems. We should expect continued advancements in costeffective microprocessors and microcontrollers, sensor and actuator development enabled by advancements in applications of MEMS, adaptive control methodologies and real-time programming methods, networking and wireless technologies, mature CAE technologies for advanced system modeling, virtual prototyping, and testing.
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The continued rapid development in these areas will only accelerate the pace of smart product development. The Internet is a technology that, when utilized in combination with wireless technology, may also lead to new mechatronic products. While developments in automotives provide bright examples of mechatronics development, there are numerous examples of intelligent systems in all walks of life, including smart home appliances such as dishwashers, vacuum cleaners, microwaves, and wireless network enabled devices. In the area of “human-friendly machines” we can expect advances in robot-assisted surgery, and implantable sensors and actuators. Other areas that will benefit from mechatronic advances may include robotics, manufacturing, space technology, and transportation. The future of mechatronics is wide open.
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Mechatronic system designs are complex by nature, and are becoming more complex day by day. As the system design grow in overall size to accommodate ever increasing demands for functionality and performance, these design must integrate analog and digital hardware, as well as the software that controls them. Mechatronic system’s behavior is determined by interdependencies between different components. Therefore, an integrated and interdisciplinary engineering approach is necessary. For this reason, engineers must be assisted by tools which allow a systems analysis with respect to capabilities, capacities and behavior without really constructing the system. This necessitates an appropriate modeling and simulation tool for mechatronic systems. 76
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