Introduction to Mechatronics

• Lectures are provided by Assoc. Prof. Magdy Roman

Topics Covered

• Introduction
• Sensors & Transducers
• Signal Conditioning
• Actuators
• Digital Circuits
• Microprocessors & Microcontrollers
• Data Acquisition & Microcontroller/PC interfacing
• Industrial Control Systems and Networking

What is Mechatronics?

• It is a synergistic interdisciplinary integration of multiple engineering fields
• These fields include mechanical, electrical, electronics, computer, control systems, and information technology
• It is used to design, develop, and test intelligent systems with embedded learning capabilities
• The design methodology is based on a concurrent, rather than sequential, approach to discipline design

Multidisciplinary vs Mechatronic Systems

• The difference lies in the design order
• Multidisciplinary systems historically employed a sequential design-by-discipline approach
• In this approach the mechanical design is completed first
• Power and Microelectronics are then designed
• Control algorithm design and implementation are last
• A major drawback is that fixing the design at various points creates new constraints that are passed on

Old Electromechanical Product Design Teams

• They included engineers for mechanical components
• They included engineers for electrical components, such as actuators, sensors, and amplifiers
• They include engineers for computer hardware and software implementation
• Mechatronic design takes on all three functions

Examples of Mechatronic Systems

• Robots and robotic systems
• Automotives
• One example is the engine management system, which manages ignition and fueling
• Production lines
• CNC machines
• Washing machines
• Electrohydraulic systems
• Electropneumatic systems

Typical Mechatronics Systems Structure

• At its core, there is a mechanical system to be commanded or controlled
• Examples include vehicle braking systems, positioning tables, ovens, and assembly machines
• Controllers need system state information, which is obtained from sensors
• Sensors can provide proximity, velocity, temperature, or displacement data
• Signals from sensors often need signal conditioning before being read by the controller
• Conditioned signals are converted to digital form using an analog-to-digital converter
• The signals are converted if they are not already digital, and then they are presented to the controller

Controllers

• The controller is the 'mind' of the system, processing user commands and sensed signals
• It generates command signals sent to the actuators
• The choice depends on cost, size, ease of development, and transportability
• Many systems use PCs with data acquisition capabilities
• Examples include control of manufacturing processes like welding, cutting, and assembly
• Controllers are often implemented using a Microcontroller Unit(MCU), a single-chip device
• This includes a processor, memory, and input-output devices
• Microcontrollers are used for consumer devices and vehicle safety systems
• Control systems using MCUs are referred to as embedded control systems

User Commands

• They are obtained from devices like command buttons, GUIs, touch screens, or pads
• Sometimes, command signals are sent to actuators without feedback
• This is called open-loop operation, requiring good calibration to minimize disturbances
• Closed-loop mode is more common, using feedback from sensors
• Closed-loop mode is better for handling disturbances and noise

Discrete Event vs Feedback Control Systems

• Control systems can be classified as discrete event or feedback
• In a discrete-event system, the controller executes a sequence of events
• In a feedback control system, the controller adjusts variables using feedback sensors
• Realistic systems combine both types

Command Signals to Actuators

• They are first converted from digital to analog form
• Amplifiers, as drive circuits, amplify command signals sent to the actuators
• The actuator converts electrical signals into mechanical motion or action

Mechatronics Design

• It is an improvement upon existing lengthy and expensive design processes
• Engineers from various disciplines work simultaneously and cooperatively
• It eliminates problems from design incompatibilities, reduces design time, and improve ability to adapt to mid-design changes
• The Aberdeen Group provided information on incorporating design processes
• Aberdeen researchers used five key product development performance criteria to distinguish best-in-class companies
• The criteria were revenue, product cost, product launch dates, quality, and development costs
• Best-in-class companies are more likely to hit product cost targets
• They are also more likely to hit product launch dates
• Best in class are more likely to attain quality objectives
• They are more likely to communicate design changes across disciplines
• These firms are more likely to digitally validate system behavior with component simulation
• These firms are more likely to achieve revenue targets

Scale Example

• Mechatronic systems can improve performance beyond what is achievable using manual means
• Bathroom scales are considered in terms of spring compression and motion conversion
• Weight indication should not depend on the person's position
• The behavior of mechanical parts should not depend on how warm the room is
• Springs might be replaced by load cells with strain gauges
• A microprocessor can then be used to digitally readout the weight on an LED display
• The resulting scales might be mechanically simpler, involving fewer components and moving parts
• The complexity shifts to the software

Design Process

• It consists of the following stages:
• The need
• Analysis of the problem
• Preparation of a specification
• Generation of possible solutions
• Selections of a suitable solution
• Production of a detailed design
• Production of working drawings

The Need

• The design process begins with a need from a customer or client
• This may be identified by market research

Analysis of the Problem

• The first stage is finding out the true nature of the problem
• Not defining the problem accurately can lead to wasted time on designs that will not fulfill the need

Preparation of a Specification

• Following the analysis, a specification of the requirements should be prepared

Specifications include

• Functions and features that are required of the design
• Required constraints on the solution
• Criteria which may be used to judge the quality of the design
• Statements of mass, accuracy, input and output requirements, dimensions, and types and range of motion

Generation of Possible Solutions

• Often termed the conceptual stage
• Outline solutions are prepared to indicate the means of obtaining each of the specified functions
• Figure out what has been done before for similar problems, so there is no need in reinventing the wheel

Selections of a Suitable Solution

• The various solutions are evaluated and the most suitable one is selected
• Evaluation will often involve the representation of a system by a model, and then simulation to establish how it might react to inputs

Production of a Detailed Design

• The detail of the design is now worked out
• This might require the production of prototypes or mock-ups in order to determine the different details of the design

Production of Working Drawings

• The selected design is translated into circuit diagrams so that the item can be made

Life-Cycle Design

• It includes life-cycle factors
• Delivery (time and cost)
• Reliability (failure rate, materials, and tolerances)
• Maintainability (modular design)
• Serviceability (on board diagnostics and prognostics)
• Upgradeability (future compatibility with current designs)
• Disposability (recycling and disposal of hazardous materials)