Professor Charlton S. Inao

Defence University

Bishoftu ,Ethiopia

PE-4030

Introduction To

Mechatronics

Week 1

Orientation and discussion of syllabus Introduction Elements of Mechatronics Classification of Control systems Mechatronic Approach

Introduction

The word mechatronics was first introduced by the senior engineer of a Japanese company; Yaskawa, in 1969, as a combination of "mecha" of mechanisms and "tronics" of electronics, and the company was granted trademark rights on the word in 1971.

Mechatronics - Definition

Mechatronics is synergistic integration of mechanical engineering, electronics and intelligent computer control in design and manufacture of products and processes.

Evolution of Mechatronic Systems The development of mechatronics has gone through

three stages.

The first stage corresponds to the years when this term was introduced. During this stage, technologies used in mechatronic systems developed rather independently and individually.

During the second stage, i.e., with the beginning of the eighties, a synergistic integration of different technologies started taking place, the no-table example is optoelectronics (i.e. an integration of optics and electronics). The concept of hardware/software co-design also started in those years.

The third and the last stage can also be considered as the beginning of the mechatronics age since early nineties.

The most notable aspect of the third stage is the increased use of computational intelligence in mechatronic products and systems. It is due to this development that we can now talk about Machine Intelligence Quotient (MIQ).

Another important achievement of the third stage is the possibility of miniaturization of components; in the form of micro actuators and micro sensors (i.e. micro mechatronics).

Key Elements of Mechatronic System

Actuators

Most mechatronic systems involve motion or action of some sort.

Actuators are the devices used to produce this motion or action.

This motion or action can be applied to any thing from a single atom to a large articulated structure.

It is created by a force or torque that results in acceleration and displacement.

Actuators produce physical changes such as linear and angular displacement.

They also modulate the rate and power associated with these changes.

An important aspect of mechatronic system design is selecting the appropriate type of actuator.

Types of actuation systemsPneumatic and hydraulic actuation systemsMechanical actuation systemsElectrical actuation systems

Sensors

A sensor is an element in a mechtronic or measurement system that acquires a physical parameter and changes it into a signal that can be processed by the system.

Often the active element of a sensor is referred to as a transducer.

Transducers are grouped according to what they are being used to measure

• Displacement position and proximity

• Velocity and motion sensors

• Force

• Fluid pressure

• Liquid flow

• Liquid level

• Temperature

• Light sensors

Smart SensorsConductometric SensorsCapacitive SensorsPiezoelectric SensorsMagnetostrictive SensorsPiezoresistive sensorsOptical SensorsResonant SensorsSemiconductor bases sensorsAcoustic SensorsPolymeric SensorsCarbon Nanotube Sensors

Necessity for Input Signal Conditioning

The transducers which converts physical quantities like temperature, displacement etc., into currents or voltages and gives them in the form of analog signals, which are continuous and time varying.

Often the signal from the traducers may be – Too small (in milli volts) Too noisy (due to electromagnetic interference) Containing wrong information (due to poor transducer design) Having DC offset (due to transducer and instrumentation design)

Many of these these problems can be remedied and the desired signal information can be extracted through appropriate analog signal processing.

The simplest and the most common form of signal processing is amplification, where the magnitude of the signal is increased.

Need for digital signal

Analog signal are continuous and time varying, whereas digital signals have only two stages: high and low.

Since computers and microprocessors require digital signals, any application involving computer measurement or control requires analog to digital conversion.

Control Architectures

To obtain completeness in the integration of mechanical devices sensors signal and power electronics

into the most advanced mechatronic systems, microprocessor based control systems must be included.

Hierarchy of basic control approaches

Analog circuits Digital Circuits PLC’s Microcontroller Single Board Computer Personal Computer.

Copy Machine – A typical example of a Mechatronic System

An office copy machine consists of analog and digital circuits, sensors, actuators and microprocessors.

Analog circuits control the lamp, heater and other power circuits in the machine.

Digital circuits controls the digital displays, indicator lights, buttons and switches forming the user interface.

Optical sensors and micro switches detects the presence or absence of the paper, its proper positioning and whether or not doors and latches are in their correct positions.

Other sensors include encoders used to track the motor rotation.

Actuators include servo and stepper motors that load and transport the paper, turn the drum and index the sorter.

Microprocessors coordinate all the functions in the machine

Examples of Mechatronic Systems (MS)

computer disk drive

clothes washer

CLASSIFICATION OF

CONTROL SYSTEMS

Open Loop Control System In an open loop control system, the input

to the plant does not in any way depend on the current and past values of the output of the plant.

The design of the open loop controller is based on inversion.

Relatively simple and consequently low cost with generally good reliability.

Disadvantages of OLCS The biggest problem with the open loop

control systems is that they rely totally in calibration, and ca not effectively deal with exogenous disturbances.

They can not effectively deal with changes in the process.

Can not deal with uncertainty. Can not stabilize an unstable system. Often in accurate since there is no

correction for error.

Closed Loop Control System Closed loop control system make the control system robust to

uncertainty and disturbances. It senses the output of the system and adjust the control input using

feedback rules, which are based on how the system output deviates from the system behaves.

The feedback helps compensate for the differences, if the system behaves slightly differently than the model.

Relatively accurate in matching the actual to the required values.

DISADVANTAGE

More complex, and more expensive, greater chance of breakdown due to number of components.

Very sensitive Hard and expensive to maintain; Requires highly specialized expertise and skill; Prone to throw away stuff - disposables.

Open Loop system: Heating a room

Basic Elements of a Closed Loop system Comparison element Control element Correction Element Process element Measurement element

Closed Loop system: Heating a room

DESIGN OF

MECHATRONIC SYSTEMS

STAGES IN DESIGN PROCESS

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 Manufacturing of prototypes Mass production

TRADITIONAL DESIGN VS MECHATRONICS DESIGN

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.

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.

THERMOSTAT

TRADITIONAL DESIGN MECHATRONICS DESIGN

TRADITIONAL THERMOSTAT DESIGN

SECTIONAL VIEW COMPONENTS OF THERMOSTAT

CONVERSION TO MECHATRONIC DESIGN

ADVANTAGES OF MECHATRONICS DESIGN

HIGH RESOLUTION & ACCURACY

REDUCES HOUSE HOLD HEATING COST

SELF CALIBRATING

FLEXIBLE DESIGN

ENVIRONMENTAL FRIENDLY

TINY MCUs IN SWITCHES & POTENTIOMETERS

Applications in Mechatronics

Manufacturing

Noteworthy Mechatronic Applications

Automotive Industry:

• Vehicle diagnostics and health monitoring. Various sensors are used to detect the environment or road conditions; Sensors to monitor engine coolant, temperature and quality; Engine oil pressure, level, and quality; tire pressure; brake pressure.

• Pressure, temperature sensing in various engine and power train locations Manifold control with pressure sensors; exhaust gas analysis and control; Crankshaft positioning; Fuel pump pressure and fuel injection control; Transmission force and pressure control.

• Airbag safety deployment system. Micro-accelerometers and inertia sensors mounted on the chassis of the car measures car deceleration in x or y directions can assist in airbag deployment.

• Antilock brake system, cruise control. Position sensors to facilitate antilock braking system; Displacement and position sensors in suspension systems.

• Seat control for comfort and convenience. Displacement sensors and micro actuators for seat control; Sensors for air quality, temperature and humidity, Sensors for defogging of windshields.

Health Care Industry:

• Medical diagnostic systems, non-invasive probes such as ultrasonic probe. Disposable blood pressure transducer; Intrauterine pressure monitor during child delivery.

• Pressure sensors in several diagnostic probes. Systems to control the intravenous fluids and drug flow; Catheter tip pressure sensor.

• Endoscopic and orthopedic surgery. Angioplasty pressure sensor; Respirators; Lung capacity meters.

• Other products such as Kidney dialysis equipment; MRI equipment.

 

Aerospace Industry:

• Landing gear systems; Cockpit instrumentation; Pressure sensors for oil, fuel, transmission; Air speed monitor; Altitude determination and control systems.

• Fuel efficiency and safety systems; Propulsion control with pressure sensors; Chemical leak detectors; Thermal monitoring and control systems.

• Inertial guidance systems; Accelerometers; Fiber-optic gyroscopes for guidance and monitoring.

• Communication and radar systems; High bandwidth, low-resistance radio frequency switches; Optical instrumentation using laser communications.

 

Consumer Industry:

• Consumer products such as auto focus camera, video, and CD players; Consumer electronic products; User-friendly washing machines with water level controls, dish washers, and other home appliances.

• Video game entertainment systems; Virtual instrumentation in home entertainment.

• Home support systems; Garage door opener; Sensors with heating, ventilation, and air-conditioning system; Home security systems.

Industrial Systems and Products:• Monitoring and control of the manufacturing process; CNC machine tools;

Advanced high speed machining and quality monitoring; Intelligent machining and on-line quality check; Digital torque wrenches, variable speed drilling and other hand tools.

• Rapid prototyping; Manufacturing cost saving by rapid creation of models done by CAD/CAM integration and rapid prototyping equipment.

• Autonomous production cells with image-based object recognition; Flexible manufacturing and other factory automation systems.

• Specialized manufacturing process such as the use of welding robots; Procedure for automatically programming and controlling a robot from CAD data; Robotics in nuclear inspection and space applications.

• Automatic guided vehicles, space application; Use of automated navigation system for NASA projects; Use of automated systems in under water monitoring and control.

Other Applications:

• Telecommunications.

• Biorobotics, which utilize the biofunctions for applications in environmental control.

• Magnetically levitated vehicles.

• Scanners and copying machines and other office eqpt

Example: Mechatronic Design of the Hewlett-Packard DESKJET 560C Printer

The mechatronic related design objectives for this printer are shown in Table below.

MECHATRONIC DESIGN

Figure illustrates the mechatronic design of the printer.

The printer uses three motors: a dc motor drives the scanning carriage, one permanent magnet “tin-can” stepper motor drives the paper feed system, and a second permanent magnet stepper motor actuates the print cartridge service station.

Figure : HP deskjet Mechatronic System

All three of these motors are controlled with less than 10% of the bandwidth of an inexpensive 8-bit Z-80 microprocessor

Figure : Control System Block Diagram

Modern Trends of MS Development

Office equipment;Computer facilities;Photo and video equipment;

Machine-tool construction and equipment for automation of technological processes;Robotics;

Modern Trends of MS Development Aviation, space and military

techniques; Motor car construction

Modern Trends of MS Development Simulators for training of

pilots and operators; Show-industry; Control and measuring

devices and machines; Micro machines; Non-conventional

vehicles.

Fundamental Problems

Structural integration of mechanical, electronic and information departments into a uniform creative staff;

Education and training of engineers specialized in mechatronics and managers able to organize integration and supervise work of strictly specialized experts with different qualifications;

Integration of information technologies from various scientific and technical fields into a uniform toolkit to provide computer support of mechatronic problems;

Standardization and unification of all used elements and processes at designing and manufacturing MS.

Levels of Mechatronic Systems’ Integration

The First Level

conveyors, rotary tables,auxiliary manipulators

Levels of Mechatronic Systems’ Integration

The Second Level

operated power machines (turbines and generators),machine tools and industrial robots with numerical program management

Levels of Mechatronic Systems’ Integration

The Third Level Synthesis of new precise information and measuring high technologies gives a basis for designing and producing intellectual mechatronic modules and systems.