K.S.Rangasamy College of Technology - Autonomous RegulationR 2010

DepartmentMechanical Programme Code & NameME: B.E. Mechanical Engineering

Semester VII

Course CodeCourse NameHours/ WeekCreditMaximum Marks

LTPCCAESTotal

10 ME 702MECHATRONICS AND ROBOTICS30035050100

Objective(s)The course aims to provide a detailed appreciation of the concepts of mechatronics and robotics in the context of automation industry. It is undertaken with particular on mechatronics drives and controllers with several applications and robot end effectors and programming.

1MECHATRONICS, SENSORS AND TRANSDUCERSTotal Hrs9

Mechatronics systems-Stages in Designing mechatronic systems - Traditional and Mechatronic design- Sensors and Transducers Performance Terminology Sensors for Displacement, Position and Proximity; Velocity, Motion, Force, Fluid Pressure, Liquid Flow, Liquid Level, Temperature,Light Sensors Selection of Sensors

2DRIVES AND CONTROLLERSTotal Hrs9

Introduction of Mechanical Actuation Systems - Electrical Actuation Systems - Solenoids -Stepper and servo Motors.Controllers - PID Controllers- Programmable Logic Controller (PLC) -Introduction-Basic structure-Input /Output Processing - PLC Programming- Timers, Internal relays and counters - Data handling - Analog Input /Output- Selection of a PLC.

3CASE STUDIES OF MECHATRONIC SYSTEMSTotal Hrs9

A pick and place robot Car park barriers Automatic Camera Car engine management Bar code reader Autonomous mobile robot Wireless survillence balloon Antilock braking system (ABS) control Smart homes - Boat autopilot.

4FUNDAMENTALS OF ROBOTTotal Hrs9

Basic structure of robot - classification of robot and robotic systems - laws of robotics - robot motions work space - precision of movement- Introduction of homogeneous transformation matrices

5END EFFECTTORS AND PROGRAMMINGTotal Hrs9

Mechanical grippers - Types of gripper mechanisms - Other types of grippers - Vacuum cups Magnetic grippers - Adhesive grippers.Robot Programming: Lead through programming, Robot programming Languages VAL Programming Motion Commands, Sensor Commands, End effecter commands, and Simple programs.

Total hours to be taught45

Text book:

1Bolton. Mechatronics - Electronic Control systems in Mechanical and Electrical Engineering, 2ndedition, Addison Wesley Longman Ltd., 1999.

2Saeed B. Niku, Introduction to Robotics: Analysis, Systems, Applications, 2nd edition, PearsonEducation India, 2003.

Reference(s):

1M.P.Groover, Industrial Robotics-Technology, Programming and Applications, Tata McGraw Hill, 2008.

2Nitaigour Premchand Mahadik, Mechatronics, Tata McGraw-Hill publishing Company Ltd, 2003

3Michael B. Histand and David G. Alciatore, Introduction to Mechatronics and Measurement Systems,McGraw-Hill, 2000.

UNIT 1 MECHATRONICS, SENSORS AND TRANSDUCERS1. Mechatronics systems 1.1 What is Mechatronics? The term "mechatronics" was first assigned by Mr. Tetsuro Mori, a senior engineer of the Japanese company Yaskawa, in 1969. Mechatronics is a methodology used for the optimal design of electromechanical products. Mechatronics basically refers to mechanical electronic systems and normally described as systems. 1.2 Mechatronics Definition The term Mechatronics is used for the integration of microprocessor control system, electrical systems and mechanical systems. Mechatronics is defined as the integration of precision mechanical & electronic control for the development of smart products & process. Mechatronics is the synergistic a synergistic combination of mechanics, electrical, electronics, computer and control which, when combined, make possible the generation of simple, more economic, and reliable integration of mechanical engineering with electronics & Intelligent control algorithms in the design & manufacture of products process. Examples : washing machine, Robot, automobile electronic fuel injection & antilock brake systems, digital camera etc.1.3 Components of Mechatronics System

Physically, a mechatronic system is composed of four prime components. They are sensors, actuators, controllers and mechanical components. Figure shows a schematic diagram of a mechatronic system integrated with all the above components.1.4 Examples of Mechatronics Systems Robot, Motion and Force Control of an Indirect Drive Robot, program to track straight line, program for collision avoidance in outside corridor, a computer disk drive, washing machine, cargo handling, subsea vehicle, autonomous flight control systems, mining Applications. 2. Stages in designing Mechatronis systems2.1 The Mechatronics Design Process The traditional electromechanical-system design approach attempted to inject more reliability and performance into the mechanical part of the system during the development stage. The control part of the system was then designed and added to provide additional performance or reliability and also to correct undetected errors in the design. Because the design steps occur sequentially, the traditional approach is a sequential engineering approach. A Standish Group survey of software dependent projects found. 31.1% cancellation rate for software development projects. 222% time overrun for completed projects. 16.2% of all software projects were completed on time and within budget. Maintenance costs exceeded 200% of initial development costs for delivered software.The Boston-based technology think tank, Aberdeen Group, provided key information on the importance of incorporating the right design process for a mechatronic system design. Aberdeen researchers used five key product development performance criteria to distinguish best-in-class companies, as related to mechatronic design. The key criteria were revenue, product cost, product launch dates, quality, and development costs. Best-in-class companies proved to be twice as likely as laggards (worst-in-class companies) to achieve revenue targets, twice as likely to hit product cost targets, three times as likely to hit product launch dates, twice as likely to attain quality objectives, and twice as likely to control their development costs. Aberdeens research also revealed that best-in-class companies were. 2.8 times more likely than laggards to carefully communicate design changes across disciplines. 3.2 times more likely than laggards to allocate design requirements to specific systems, subsystems, and components. 7.2 times more likely than laggards to digitally validate system behavior with the simulation of integrated mechanical, electrical, and software components.A major factor in this sequential approach is the inherently complex nature of designing a multidisciplinary system. Essentially, mechatronics is an improvement upon existing lengthy and expensive design processes. Engineers of various disciplines work on a project simultaneously and cooperatively. This eliminates problems caused by design incompatibilities and reduces design time because of fewer returns. Design time is also reduced through extensive use of powerful computer simulations, reducing dependency upon prototypes. This contrasts the more traditional design process of keeping engineering disciplines separate, having limited ability to adapt to mid-design changes, and being dependent upon multiple physical prototypes.The mechatronic design methodology is not only concerned with producing high-quality products but with maintaining them as wellan area referred to as life cycle design. Several important life cycle factors are indicated. Delivery: Time, cost, and medium. Reliability: Failure rate, materials, and tolerances. Maintainability: Modular design. Serviceability: On board diagnostics, prognostics, and modular design. Upgradeability: Future compatibility with current designs. Disposability: Recycling and disposal of hazardous materials.We will not dwell on life cycle factors except to point out that the conventional design for life cycle approach begins with a product after it has been designed and manufactured. In the mechatronics design approach, life cycle factors are included during the product design stages, resulting in products which are designed from conception to retirement. The mechatronic design process is presented in Figure.

The mechatronic design process consists of three phases: modeling and simulation, prototyping, and deployment. All modeling, whether based on first principles (basic equations) or the more detailed physics, should be modular in structure. A first principle model is a simple model which captures some of the fundamental behavior of a subsystem. A detailed model is an extension of the first principle model providing more function and accuracy than the first level model. Connecting the modules (or blocks) together may create complex models. Each block represents a subsystem, which corresponds to some physically or functionally realizable operations, and can be encapsulated into a block with input/output limited to input signals, parameters, and output signals. Of course, this limitation may not always be possible or desirable; however, its use will produce modular subsystem blocks which easily can be maintained, exercised independently, substituted for one another (first principle blocks substituted for detailed blocks and vice versa), and reused in other applications. Because of their modularity, mechatronic systems are well suited for applications that require reconfiguration. Such products can be reconfigured either during the design stage by substituting various subsystem modules or during the life span of the product. Since many of the steps in the mechatronic design process rely on computer-based tasks (such as information fusion, management, and design testing), an efficient computer-aided prototyping environment is essential.Important Features Modeling: Block diagram or visual interface for creating intuitively understandable behavioral models of physical or abstract phenomenon. The ability to encapsulate complexity and maintain several levels of subsystem complexity is useful. Simulation: Numerical methods for solving models containing differential, discrete, hybrid, partial, and implicit nonlinear (as well as linear) equations. Must have a lock for real-time operation and be capable of executing faster than real time. Project Management: Database for maintaining project information and subsystem models for eventual reuse. Design: Numerical methods for constrained optimization of performance functions based on model parameters and signals. Monte Carlo type of computation is also desirable. Analysis: Numerical methods for frequency-domain, time-domain, and complex-domain design. Real-Time Interface: A plug-in card is used to replace part of the model with actual hardware by interfacing to it with actuators and sensors. This is called hardware in the loop simulation or rapid prototyping and must be executed in real time. Code Generator: Produces efficient high-level source code from the block diagram or visual modeling interface. The control code will be compiled and used on the embedded processor. The language is usually C. Embedded Processor Interface: The embedded processor resides in the final product. This feature provides communication between the process and the computer-aided prototyping environment. This is called a full system prototype.Because no single model can ever flawlessly reproduce reality, there always will be errorbetween the behavior of a product model and the actual product. These errors, referred to as unmodeled errors, are the reason that so many model-based designs fail when deployed to the product. The mechatronic design approach also uses a model-based approach, relying heavily on modeling and simulation. However, unmodeled errors are accounted for in the prototyping step. Their effects are absorbed into the design, which significantly raises the probability of successful product deployment.Hardware-in-the-Loop Simulation In the prototyping step, many of the non-computer subsystems of the model are replaced with actual hardware. Sensors and actuators provide the interface signals necessary to connect the hardware subsystems back to the model. The resulting model is part mathematical and part real. Because the real part of the model inherently evolves in real time and the mathematical part evolves in simulated time, it is essential that the two parts be synchronized. This process of fusing and synchronizing model, sensor, and actuator information is called real-time interfacing or hardware-in-the-loop simulation, and is an essential ingredient in the modeling and simulation environment.TABLE: DIFFERENT CONFIGURATIONS FOR HARDWARE-IN-THE-LOOP SIMULATION

So far, we have only discussed one configuration for hardware-in-the-loop simulation. This and other possibilities are summarized in Table. Table assumes the following six functions. Control: The control algorithm(s) in executable software form. Computer: The embedded computer(s) used in the product. Sensors Actuators Process: Product hardware excluding sensors, actuators, and the embedded computer. Protocol (optional): For bus-based distributed control applications.The comprehensive development of mechatronic systems starts with modeling and simulation, model building for static and dynamic models, transformation into simulation models, programming and computer-based control, and final implementation. In this atmosphere, hardware-in-the-loop simulation plays a major part. Using visual simulation tools in a real-time environment, major portions of the mechatronic product could be simulated along with the hardware-in-the-loop simulation. The hardware-in-the-loop model (Figure) shows the different components of a mechatronics system. It is possible to simulate the electronics where the actuators, mechanics and sensors are the real hardware. On the other hand, if appropriate models of the mechanical systems, actuators, and sensors are available, the electronics could be the only hardware. There are different ways in which hardware-in-the-loop could be simulated, such as electronics simulation, simulation of actuators and sensors, or simulation of mechanical systems alone.

3. Traditional and Mechatronic Design3.1 The traditional and Mechatronics approach of design Sl. no.Traditional DesignMechatronics design

1It is based on traditional system such as mechanical, hydraulic and pneumaticIt is based on mechanical, electronics, computer technology and control engineering

2Less flexibleMore flexible

3Less accurateMore accurate

4More complicate mechanism in designLess complicate mechanism design

5It involves more components and moving partsIt involves fewer compounds and moving parts

Case study: Temperature control for a domestic central heating system

Bimetallic thermostat in a closed loop control systemMicroprocessor-controlled system employing perhaps a thermo diode as the sensor.

3.2 The advantages and limitations of mechatronics system Advantages: Simplified mechanical design Rapid machine setup Rapid development trials Adaption possibilities Optimized performance, productivity, reliabilityLimitations: Increased power requirements Real-time calculations/mathematical models

4. Sensors and TransducersThe term sensor is used for an element which produces a signal relating to the quantity being measured. Thus in the case of, say, an electrical resistance temperature element, the quantity being measured is temperature and the sensor transforms an input of temperature into a change in resistance.The term transducer is often used in place of the term sensor. Transducers are defined as elements that when subjected to some physical change, experience a related change. Thus sensors are transducers.Some sensors come combined with their signal conditioning all in the same package. Such an integrated sensor does still, however, require further data processing. However, it is possible to have the sensor and signal conditioning combined with a micro processor all in the same package. Such an arrangement is termed a smart sensor. A smart sensor is able to have such functions as the ability to compensate for random errors, to adapt to changes in the environment, give an automatic calculation of measurement accuracy, adjust for non-linearities to give a linear output, self-calibrate ad give self-diagnosis of faults.5. Performance Terminology The following terms are used to define the performance of transducers, and often measurement systems as a whole.5.1 Range and SpanRange: lowest and highest values of the stimulusSpan: the arithmetic difference between the highest and lowest values of the input that being sensed.Input full scale (IFS) = spanOutput full scale (OFS): difference between the upper and lower ranges of the output of the sensor.Dynamic range: ratio between the upper and lower limits and is usually expressed in dbExample: a sensors is designed for: -30 C to +80 C to output 2.5V to 1.2VRange: -30C and +80 CSpan: 80- (-30)=110 CInput full scale = 110 COutput full scale = 2.5V-1.2V=1.3VDynamic range=20log(140/30)=13.38db5.2 Errors and AccuracyErrors: is the difference between the result of the measurement and the true value of the quantity being measurederror= measured value true valueAs a percentage of full scale (span for example) error is calculated as;e = t/(tmax-tmin)*100 where tmax and tmin are the maximum and minimum values the device is designed to operate at.

Accuracy: is the extent to which the measured value might be wrong and normally expressed in percentage Example: A thermistor is used to measure temperature between 30 and +80 C and produce an output voltage between 2.8V and 1.5V. Because of errors, the accuracy in sensing is 0.5C. so the measured value may be high than or lower than by 0.5 C a. In terms of the input as 0.5Cb. Percentage of input: error = 0.5/(80+30)*100 = 0.454%c. In terms of output. From the transfer function: error= 0.059V. ?5.3 HysteresisHysteresis is the deviation of the sensors output at any given point when approached from two different directions

Caused by electrical or mechanical systems Magnetization Thermal properties Loose linkagesIf temperature is measured, at a rated temperature of 50C, the output might be 4.95V when temperature increases but 5.05V when temperature decreases.This is an error of 0.5% (for an output full scale of 10V in this idealized example).5.4 NonlinearityNonlinearity is defined as the maximum deviation from the ideal linear transfer function.

Nonlinearity must be deduced from the actual transfer function or from the calibration curve A few methods to do so:a. by use of the range of the sensor Pass a straight line between the range points (line 1)b. use a linear best fit (least squares) through the points of thecurve (line 2)c. use the tangent to the curve at some point on the curveTake a point in the middle of the range of interest Draw the tangent and extend to the range of the curve (line 3)5.5 DeadbandDeadband: the lack of response or insensitivity of a device over a specific rangeof the input.In this range which may be small, the output remains constant.A device should not operate in this range unless this insensitivity is acceptable.

5.6 Output impedanceOutput impedance: ratio of the rated output voltage and short circuit current of the port (i.e. current when the output is shorted)output impedance is important for interfacing Example: 500 sensor (output impedance) connected to a processorb. Processor input impedance is infinitec. Processor input impedance is 500 W

5.7 Repeatability Also called reproducibility: failure of the sensor to represent the same value under identical conditions when measured at different times. usually associated with calibration given as percentage of input full scale of the maximum difference between two readings taken at different times under identical input conditions.Repeatability = 5.8 SensitivitySensitivity of a sensor is defined as the change in output for a given change ininput, usually a unit change in input. Sensitivity represents the slope of the transfer function.Also is used to indicate sensitivity to other environment that is not measured.Example: sensitivity of resistance measurement to temperature change

5.9 ResolutionResolution: the minimum increment in stimulus to which the sensor can respond. It is the magnitude of the input change which results in the smallest observable output.Example: a digital voltmeter with resolution of 0.1V is used to measure the output of a sensor. The change in input (temperature, pressure, etc.) that will provide a change of0.1V on the voltmeter is the resolution of the sensor/voltmeter system.In digital systems generally, resolution may be specified as 1/ 2N (N is the number of bit.)5.10 StabilityThe stability of a transducer is its ability to give the same output when used to measure a constant input over a period of time. The term drift is often used to describe the change in output that occurs over time. The drift may be expressed as a percentage of the full range output. The term zero drift is used for the change that occur in output when there is zero input.5.11 Output impedanceWhen a sensor giving an electrical output is interfaced with an electronic circuit it is necessary to know the output impedence since this impedence is being connected in either serried or parallel with that circuit. The inclusion of the sensor can thus significantly modify the behavior of the system to which it is connected.6.