LECTURE № 1

WHAT IS «MECHATRONICS»

 

1.1.         What is «Mechatronics»

 

Mechatronics is a concept of Japanese origin (1970’s) and can be defined as the application of electronics and computer technology to control the motions of mechanical systems (figure 1.1.).

 

Fig. 1.1. Definition of Mechatronics

It is a multidisciplinary approach to product and manufacturing system design (Figure 1.2). It involves application of electrical, mechanical, control and computer engineering to develop products, processes and systems with greater flexibility, ease in redesign and ability of reprogramming. It concurrently includes all these disciplines.

Fig. 1.2. Mechatronics: a multi-disciplinary approach

Mechatronics can also be termed as replacement of mechanics with electronics or enhance mechanics with electronics. For example, in modern automobiles, mechanical fuel injection systems are now replaced with electronic fuel injection systems. This replacement made the automobiles more efficient and less pollutant.

With the help of microelectronics and sensor technology, mechatronics systems are providing high levels of precision and reliability. It is now possible to move (in x – y plane) the work table of a modern production machine tool in a step of 0.0001 mm.

By employment of reprogrammable microcontrollers/microcomputers, it is now easy to add new functions and capabilities to a product or a system. Today’s domestic washing machines are «intelligent» and four-wheel passenger automobiles are equipped with safety installations such as air-bags, parking (proximity) sensors, anti-theft electronic keys etc.

1.2.         Importance of Mechatronics in automation

Fig. 1.2.1. Operations involved in design and manufacturing of a product

Today’s customers are demanding more variety and higher levels of flexibility in the products. Due to these demands and competition in the market, manufacturers are thriving to launch new/modified products to survive. It is reducing the product life as well as lead-time to manufacture a product.  It is therefore essential to automate the manufacturing and assembly operations of a product. There are various activities involved in the product manufacturing process. These are shown in figure 1.2.3. These activities can be classified into two groups viz. design and manufacturing activities.

Mechatronics concurrently employs the disciplines of mechanical, electrical, control and computer engineering at the stage of design itself. Mechanical discipline is employed in terms of various machines and mechanisms, where as electrical engineering as various electric prime movers viz. AC/DC, servo motors and other systems is used. Control engineering helps in the development of various electronics-based control systems to enhance or replace the mechanics of the mechanical systems. Computers are widely used to write various softwares to control the control systems; product design and development activities; materials  and manufacturing resource planning, record keeping, market survey, and other sales related activities.

Using computer aided design (CAD) / computer aided analysis (CAE) tools, three-dimensional models of products can easily be developed. These models can then beanalyzed and can be simulated to study their performances using numerical tools. These numerical tools are being continuously updated or enriched with the real-life performances of the similar kind of products. These exercises provide an approximate idea about performance of the product/system to the design team at the early stage of the product development.  Based on the simulation studies, the designs can be modified to achieve better performances. During the conventional  design-manufacturing process,  the design assessment is generally carried out after the production of first lot of the products. This consumes a lot of time, which leads to longer (in months/years) product development lead-time. Use of CAD–CAEtools saves significant time in comparison with that required in the conventional sequential design process.

CAD-CAE generated final designs are then  sent to the production and process planning section. Mechatronics based systems such as computer aided manufacturing (CAM): automatic process planning, automatic part programming, manufacturing resource planning, etc. uses the design data provided by the design team. Based these inputs, various activities will then be planned to achieve the manufacturing targets in terms of quality and quantity with in a stipulated time frame.

Mechatronics based automated systems such as automatic inspection and quality assurance, automatic packaging, record making, and automatic dispatch help to expedite the entire manufacturing operation. These systems certainly ensure a supply better quality, well packed and reliable products in the market. Automation in the machine tools has reduced the human intervention in the machining operation and improved the process efficiency and product quality. Therefore it is important to study the principles of mechatronics and to learn how to apply them in the automation of a manufacturing system.

 

1.3.         MECHATRONICS SYSTEM

A system can be thought of as a box or a bounded whole which has input and output elements, and a set of relationships between these elements. Figure 1.3.1 shows a typical spring system. It has «force» as an input which produces an «extension». The input and output of this system follows the Hooke’s law F = – kx, where F is force in N, x is distance in m and k is stiffness of the spring.

Fig. 1.3.1. A spring-force system

 

 

Fig. 1.3.2. Constituents of a mechatronics system

A Mechatronics system integrates various technologies involving sensors, measurement systems, drives, actuation systems, microprocessor systems and software engineering. Figure 1.3.3 shows the basic elements of a mechatronics system. Consider the example of a simple spring-mass system as shown in figure 1.3.2. To replace the mechanics of this mechanical system with an equivalent mechatronics based system, we need to have the basic controlling element, a microprocessor. Microprocessor processes or utilizes the information gathered from the sensor system and generates the signals of appropriate level and suitable kind (current or voltage) which will be used to actuate the required actuator viz. A hydraulic piston-cylinder device for extension of piston rod in this case. The microprocessor is programmed on the basis of the principle of Hooks’ Law. The schematic of microprocessor based equivalent spring mass system is shown in figure 1.3.3.

 

 

Fig. 1.3.3. Microprocessor based equivalent spring mass system

The input to the system is a force which can be sensed by suitable electro-mechanical sensors viz. piezo-electric device or strain gauges. These sensors generate either digital signals (0 or 1) or analogue signals (milli-volts or milli-amperes). These signals are then converted into right form and are attenuated to a right level which can properly be used by the microprocessor to take generate the actuation signals. Various electronics based auxiliary devices viz. Analogue-to-Digital Converter (ADC), Digital-to-Analogue Converter (DAC), Op-amps, Modulators, Linearization circuits, etc. are used to condition the signals which are either received by the microprocessor from the sensors or are sent to the actuators from the microprocessor. This mechatronics based spring-mass system has the input signals in the digital form which are received from the ADC and Piezo-electric sensor. The digital actuation signals generated by the microprocessors are converted into appropriate analogues signals. These analogue signals operate the hydraulic pump and control valves to achieve the desired displacement of the piston-rod.

In this course we will be studying in detail the various elements of a Mechtronics system (shown in figure 1.3.2) and their applications to manufacturing automation. In the next lecture we will study the applications of Mechatronics in manufacturing engineering and in the subsequent lectures; above-mentioned elements will be discussed in detail.