Applications of Mechatronics

Mechatronics has a wide range of applications, as discussed in the following subsections.

Design and Modelling

Design and modelling are simplified to a large extent by the use of mechatronic systems. Basically, design involves drawing, analysis, and documentation. In earlier days, the processes of design were performed manually and it took weeks or months together. Now, the computer is used to complete processes of design faster. There are many designing tools such as AUTOCAD, IDEAS, and PROENGG, through which 2D or 3D drawings can be made. There are a number of tools to edit drawings at a faster rate. Analysis of the design involves working out the stress distribution, temperature distribution, weight analysis, and animations. The virtual modelling of a manufacturing plant gives an idea of the time taken for a particular component to be manufactured and also shows virtually how the operations will be performed. The drum plotter, x-y plotter, printer, etc. give complete documentation of design drawings. Important parameters such as surface roughness and tolerance value can be incorporated in the drawing. Digitizers, plotters, CD drives, and many such devices are mechatronic systems.

Software Integration

Different kinds of software are used in manufacturing, design, testing, monitoring, and control of the manufacturing process. Examples of such software include computer aided design (CAD), computer aided testing (CAT), computer aided engineering (CAE), and computer aided processing planning (CAPP). The integration of the packets of software leads to computer integrated manufacturing (CIM) or just-in-time (JIT) manufacturing. Software integration is not only used for manufacturing but also for communication networks, economic analysis, etc. © Oxford University Press 6 Introduction to Mechatronics

Actuators and Sensors

Mechanical, electrical, hydraulic, and pneumatic actuators are widely used in the industry. Toggle linkage and quick return mechanics are typical examples of mechanical actuators. Switching devices, solenoid-type devices, and drives such as alternative current (ac) and direct current (dc) motors can be used as electrical actuators. Hydraulic and pneumatic drives use linear cylinders and rotary motors as actuators. The term sensor is used for an element which produces a signal relating to the quantity being measured. For example, an electrical resistance temperature device transforms the input of temperature into change in resistance. The term transducer is often used in place of sensor. Transducers are defined as devices which when subject to some physical change experience a related change. In the displacement transducer, force is not an error. Addition of extra force into the system reduces backlash and play. For example, in the dial gauge, an additional tension spring is provided on the rack so that the play between the set of gear trains is minimized. Similarly, in a force-transmitting transducer, the provision of more displacement is not an error. Reduction in the play in forcetransmitting devices produces a loss in power due to friction.

Intelligent Control

Feedback control systems are widespread not only in nature and the home but also in industry. There are many industrial processes and machines which control many variables automatically. Temperature, liquid level, fluid flow, pressure, speed, etc. are maintained constant by process controllers. Adaptive control and intelligent manufacturing are the areas where mechatronic systems are used for decision making and controlling the manufacturing environment.

Robotics

Robot technology uses mechanical, electronic, and computer systems. A robot is a multifunctional reprogrammable machine used to handle materials, tools, or any special items to perform a particular task. Manipulation robots are capable of performing operations, assembly, spot welding, spray painting, etc. Service robots such as mail service robots, household servant robots, nursing robots in hospitals are being used nowadays. © Oxford University Press Mechatronic Systems 7

Manufacturing

In the domain of factory automation, mechatronics has had far-reaching effects in manufacturing. Major constituents of factory automation include computer numerically controlled (CNC) machines, robots, automation systems, and computer integration of all functions of manufacturing. Low volume, more variety, higher levels of flexibility, reduced lead time in manufacture, and automation in manufacturing and assembly are likely to be the future needs of customers, and mechatronic systems will play an important role in this context.

Motion control

A rigid body can have a very complex motion which might seem difficult to describe. However, the motion of any rigid body can be considered to be combinations of translational and rotational motions. By considering a threedimensional space, a translational movement can be considered to be one which can be resolved into components along one or more of three axes. The rotation of a rigid body has rotating components about one or more of the axes. A complex motion may be a combination of translational and rotational motion. Motion control is important in many industrial applications such as robots, automated guided vehicles, NC machines, etc. If the robot arm cannot reach a particular location, then the movements of workpiece have to be analysed further. Any body has six degrees of freedom, three translations and three rotations. A point has only three translations. In a machine tool, the workpiece has six degrees of freedom and the tools also have six degrees of freedom. Thus, a machine tool with twelve degrees of freedom can be manufactured. Such a tool can perform a complicated machining operation.

Vibration and Noise Control

When a machine member is subjected to a periodic dynamic force, it will vibrate. If the vibration level ranges from a frequency of 20 Hz to 20,000 Hz, it produces noise. Vibration and noise isolation are important in industry. Vibration isolation can be achieved by passive, semi-active, or active dampers. In passive dampers the structure is mounted on damping materials with initial spring loading. In semi-active dampers, both passive and active damping elements are used. In active damping, extra energy is used to damp the structure. When a structure is subjected to a pulse input, a shock is produced. Different types of shock absorbers are used to reduce the shock amplitude. Noise isolation is equally important in industry since noise is harmful to human beings. Adaptive control techniques are used for noise isolation. In this method, the system predicts the noise level in each interval of time and noise is introduced © Oxford University Press 8 Introduction to Mechatronics through the speaker in phase opposition. This adaptive control system reduces the noise level.

Microsystems

It is fair to say that microsystems are a major step towards the ultimate miniaturization of machines and devices such as dust-size computers and needletype robots. The advancement of nanotechnology will certainly result in the realization of superminiaturized machinery. The need for miniaturization has increased manifold in recent years, and engineering systems and devices have become more and more complex and sophisticated. Picosatellites, spacecrafts, table-top manufacturing units, and microelectromechanical systems will become a reality in the future. The knowledge of mechatronics is very useful for microsystems.

Optics

All slip gauge blocks are calibrated against light wavelength as a standard. Angle gauges can be calibrated to an accuracy of 0.1 sec using a light wave standard—the angstrom unit. A combination of optical and electronic principles has led to the development of instruments such as the midarm which measures angular displacement with an accuracy of 0.05 sec. Optical angle measurement systems for inertial guidance with an accuracy of 0.02 sec have been in use since 1961. Opto-electronic systems use a lens or telescope to form an optical image of an object under study on a photocathode image detector tube. The motion of the object causes the motion of the photocathode optical image and the corresponding motion of the electron image. The optical image is obtained by a conventional videcon camera or a coupled charge device. The camera converts an array of analog signals, in 236 ¥ 236 pixels in a square centimetre. The analog signals are then converted into digital signals for each pixel and transmitted to an electron image grabber to produce an electron image. As the image starts deviating from the neutral position, the photo multiple layer output tends to drive back by means of a deflection coil. Thus, any main object can be brought to the aperture continuously. The application of still and motion picture photography often allows qualitative and quantitative analyses of complex motion. The photoelastic method is convenient to determine the stress distribution in a machine element. The basic phenomenon of double refraction under load is used in photoelasticity. Double refraction takes place when light travels at a different speed in a transparent material depending on the direction of travel relative to the direction of the principle stress and also depending on the magnitude of the difference between principle stresses for two-dimensional fields. Due to double refraction, light © Oxford University Press Mechatronic Systems 9 waves form an interference pattern of fringes on a photograph. The photograph is then used to determine the principal stresses. By the use of the frozen stress technique, the method can be extended to three-dimensional problems. The cathode ray tube provides display devices for computers and other entertainment devices such as the television, projector, etc. Electron guns with basic columns can be obtained in a pixel. Cathode ray tubes for picture displays usually have 256 ¥ 256 pixels/cm2 . As the number of pixels increases per square centimetre, the clarity of the picture becomes better. Systems are available which permit each pixel in grey levels (256 levels) in a black-and-white display. Grey levels (light intensity levels) are called grey scaling. With the basic three colours 2563 colour combinations can be obtained with grey scaling. In the ordinary film, only the magnitude of intensity is recorded, which in turn gives two-dimensional images. By recording the amplitude and phase of the reflected light from an object, a hologram can be obtained. A hologram gives three-dimensional ghost images of three-dimensional objects. An optical computer with a hologram will give faster computation in future. Coding and decoding is not required as in conventional computer operation. A ghost image from the hologram gives a grey-scaled image on each voxel. 2563 voxels can be accommodated in a cubic centimetre of laser hologram. Sintering in each voxel can be obtained by packing the metal particles in the ghost image. Thus in future any complicated article can be manufactured in seconds using the laser hologram technique.