The word, mechatronics, is composed of “mecha” from mechanism and the “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. According to the original definition of mechatronics proposed by the Yasakawa Electric Company and the definitions that have appeared since, many of the engineering products designed and manufactured in the last 25 years integrating mechanical and electrical systems can be classified as mechatronic systems. Mechatronics has a variety of applications as products and systems in the area of manufacturing automation. Some of these applications are as follows: · Computer numerical control (CNC) machines · Tool monitoring systems · Advanced manufacturing systems. · Industrial robots · Automatic inspection systems: machine vision systems · Automatic packaging systems Following are the key elements of mechatronics systems: 1. Systems Modeling 2. Sensors and Actuators 3. Signals and Systems 4. Computers and Logic Systems 5. Software and Data Acquisition Measurement is an important subsystem of a mechatronics system. Its main function is to collect the information on system status and to feed it to the micro-processor(s) for controlling the whole system. Measurement system comprises of sensors, transducers and signal processing devices. Today a wide variety of these elements and devices are available in the market. For a mechatronics system designer it is quite difficult to choose suitable sensors/transducers for the desired application(s). It is therefore essential to learn the principle of working of commonly used sensors/transducers. Sensor is defined as an element which produces signal relating to the quantity being measured. According to the Instrument Society of America, sensor can be defined as a device which provides a usable output in response to a specified measurand. Here, the output is usually an electrical quantity and measurand is a physical quantity, property or condition which is to be measured. Thus in the case of, say, a variable inductance displacement element, the quantity being measured is displacement and the sensor transforms an input of displacement into a change in inductance. Transducer is defined as an element when subjected to some physical change experiences a related change or an element which converts a specified measurand into a usable output by using a transduction principle. It can also be defined as a device that converts a signal from one form of energy to another form. A wire of Constantan alloy (copper-nickel 55-45% alloy) can be called as a sensor because variation in mechanical displacement (tension or compression) can be sensed as change in electric resistance. This wire becomes a transducer with appropriate electrodes and input-output mechanism attached to it. Thus we can say that ‘sensors are transducers’. Transducers sense physical phenomenon such as rise in temperature and convert the measurand into an electrical signal viz. voltage or current. However these signals may not be in their appropriate forms to employ them to control a mechatronics system. Figure 2.6.1 shows various signal conditioning operations which are being carried out in controlling a mechatronics based system. The signals given by a transducer may be nonlinear in nature or may contain noise. Thus before sending these signals to the mechatronics control unit it is essential to remove the noise, nonlinearity associated with the raw output from a sensor or a transducer. It is also needed to modify the amplitude (low/high) and form (analogue/digital) of the output signals into respective acceptable limits and form which will be suitable to the control system. These activities are carried out by using signal conditioning devices and the process is termed as ‘signal conditioning'. Signal conditioning system enhances the quality of signal coming from a sensor in terms of: · Protection: To protect the damage to the next element of mechatronics system such microprocessors from the high current or voltage signals. · Right type of signal: To convert the output signal from a transducer into the desired form i.e. voltage / current. · Right level of the signal: To amplify or attenuate the signals to a right /acceptable level for the next element. · Noise: To eliminate noise from a signal. · Manipulation: To manipulate the signal from its nonlinear form to the linear form. Data Conversion Devices are very important components of a Machine Control Unit (MCU). MCUs are controlled by various computers or microcontrollers which are accepting signals only in Digital Form i.e. in the form of 0s and 1s, while the signals received from signal conditioning module or sensors are generally in analogue form (continuous). Therefore a system is essentially required to convert analog signals into digital form and vis-à-vis. Analog to Digital Converter is abbreviated as ADC. Based on the signals received from sensors, MCU generates actuating signals in the Digital form. Most of the actuators e.g. DC servo motors only accept analogue signals. Therefore the digital signals must be converted into Analog form so that the required actuator can be operated accordingly. For this purpose Digital to Analog Converters are used, which are abbreviated as DAC.
S B S
Gyan Ganga Institute of technology and sciences jabalpur