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Introduction to Mechatronics Based Systems

C1M2T2_V1 Mechatronics Based Systems
Till now, a term or a word has been very regularly used and that term is system. As per as engineering point of view, a system can be defined as a box or a bounded whole or volume which has certain inputs and certain outputs, where there is a set of relationships between the elements. These elements are inputs and outputs. The set of relationship between the input and the output represents the behaviour of the real system. When this relationship is represented in mathematical form, then that process is called the modelling of the system. A simple example of a system is a thermometer. Thermometer is a very common system that one can have. The input to the system or input to the thermometer is temperature. Thermometer measures the temperature. The input element to this system is temperature and from this thermometer we get a value s or a number, displayed on the screen if it is a digital thermometer or if it is an analogue thermometer, then we can see it on the scale. There is a relationship of this number with the input temperature, as the temperature is increasing the number is also increasing. So, it can be said that the number displayed on the screen is directly proportional to the temperature This relationship when represented mathematically is called the modelling of the system. A motor can be taken as the second example. For motor, the input is electrical power and the output is a rotation. Again, there is a relationship, the rotation of the shaft of the motor will rotate at a high speed when more electrical power is applied. So, the motor or a thermometer can be called as systems which are having certain inputs and outputs. One more example of the term system is a typical mechanical system and that typical mechanical system is a spring. The spring is widely used in variety of engineering applications. The most important or the most common application of spring is in suspension of automotive. The springs comes in a variety of types such as; compression spring, extension spring, torsion spring, coil spring and leaf spring. Moreover, another application of the spring is in our previous lecture that is in watches or clocks. Now, considering a typical spring and a force arrangement; in the spring, when a force at the free end of the spring is applied, its end gets displaced. Thus, the input to the system is a force and the output is the displacement. The spring follows the Hooke’s law.Hooke’s law is a principle of physics, that states that, the force needed to extend or compress a spring by some distance is proportional to that distance itself. This law was given by a British physicist in 17th century. When a spring is stretched or compressed, its length changes by an amount x from its equilibrium length, then it exerts a force F, that is in the direction towards the equilibrium position. The force that the spring exerts is nothing, but the restoring force. It restores the spring to its equilibrium length. Mathematically, Hooke’s law can be represented as F = Kx where F is the force in Newton, x is the distance in meters and K is the constant of proportionality and it is called as the stiffness of the spring. The block diagram of a typical spring system can be seen on the above figure. It is known that, a spring has a force and a displacement and it follows the principle of operation as F=Kx . So, this relation would be true in the case of steady state condition. However, in reality, the spring will oscillate and vibrate about its equilibrium position and will achieve its equilibrium position after certain time. So, if a force on the spring is applied, an extension of the spring is observed. However, this will not be the final extension or final value that we will be getting, the spring will oscillate and vibrate and after some time it will get stabilized. Now, the various building blocks of a mechatronic based auto automated system will be discussed. The first building block of an automated system is the measurement system. The measurement system has various sensors, signal conditioning devices and display units. The second building block is the drives and actuation systems. The third one is a microprocessor system and the fourth building block is the software. It is known that, software is a set of programs which are controlling the operations of the microprocessor system. In an arrangement showing the building blocks of an automated system, a mechanical system which is basically being controlled by a microprocessor based control system can be seen. This microprocessor based control system gets inputs from various sensors, which may be digital sensors or analogue sensors. These sensors are further giving signals to signal conditioning devices. The signal conditioning may be conversion of analogue signals into digital signals. It may also have the various functions like amplification, linearization, noise removal, modulation. This signal conditioning will be discussed in detail in our next lectures. The microprocessor gives signals to the actuators through a set of signal conditioning devices. It is known that, the microprocessors are producing a series of pulses and based on that series of pulses we have to actuate the actuators. However, some of the actuators are using the analogue input as motor. In this case, it converts the digital signal which is coming from the microprocessor into the analogue form and that analogue signal will be utilized by the actuator. Actuators are actuating the mechanical system. This is a typical arrangement in which it has basic mechanical system and this is being controlled by a microprocessor based control system. It has the important blocks i.e. the measurement system and the actuation system.

PAGE 2 Assessment Question #1 Which of the following is the mathematical representation of Hooke’s Law? Drag the correct answer into the space provided