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Note for Robotics and Robot Applications - RRA by Ashutosh Jaiswal

  • Robotics and Robot Applications - RRA
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Ashutosh Jaiswal
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Introduction to Robotics UNIT – I INTRODUCTION AUTOMATION: Automation is a technology concerned with the application of Mechanical, Electronic and Computer based systems to operate and control production. This technology includes: i.)Automatic machine tools to process parts ii.)Automatic assembly machines iii.)Industrial Robots iv.)Automatic material handling and storage systems v.)Feedback control and computer process control vi.)Computer systems for planning, data collection and decision making to support manufacturing activities. They are all called automated because they perform their operations with a reduced level of human participation compared with the corresponding manual process. In some highly automated systems, there is virtually no human participation. Automated manufacturing systems can be classified into three basic types: 1. Fixed Automation 2. Programmable Automation 3. Flexible Automation 1. FIXED AUTOMATION: It is used when the volume of production is very high and it is therefore appropriate to design specialized equipment to process the product, very efficiently and at high production rates. In this system, the sequence of operations is fixed. The typical features of Fixed Automation include: 1.High initial investment for custom engineered equipment 2.High production rates 3.Relatively inflexible in accommodating product variety The economic justification of the Fixed Automation is such that, the cost of special equipment can be divided over a large number of units and the resulting unit costs are low relative to the alternative methods of production.

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The risk encountered with Fixed Automation is that, since the initial investment cost is high, if the volume of the production turns out to be lower than anticipated, then the unit costs increases. Another problem with the Fixed Automation is that the equipment is specially designed to produce a part and after that products lifecycle is finished, the equipment is likely to become obsolete. 2.PROGRAMMABLEAUTOMATION: In this system, the production equipment is designed with the capability to change the sequence of operations to accommodate different product configurations. The operation sequence is controlled by a program, which is a set of instructions coded so that they can be read and interpreted by the system. New programs can be prepared and entered into the equipment to produce new products. Some of the features of Programmable Automation include: 1.High investment in general purpose equipment 2.Lower production rates than Fixed Automation 3.Flexibility to deal with variations and changes in product configurations 4.Most suitable for batch production These systems are used in low and medium volume production. The parts or products are typically made in batches. To produce each new batch of a different product, the system must be reprogrammed with the set of machine instructions that correspond to the new product. The physical setup of the machine must also be changed. Tools must be loaded, fixtures must be attached to machine table and the required machine settings must be entered. This changeover procedure takes time. Example: Numerically Controlled Machines and Industrial Robots. 3.FLEXIBLE AUTOMATION: it is an extension of Programmable Automation. A Flexible Automated system is capable of producing a variety of parts (or products) with virtually no time lost for changeovers from one part style to the other. One of the features that distinguish Programmable Automation from Flexible Automation is that, with programmable automation, the products are made in batches. When one batch is completed, the equipment is reprogrammed to process the next batch. With flexible automation, different products can be manufactured at the same time on the same manufacturing system. The typical features of Flexible Automation include: 1. High investment for a flexible system. 2.Continuous production of variable mixture of products 3.Medium Production rates 4. Flexibility to deal with product design variation

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Changing the part programs is generally accomplished by preparing the programs offline on a computer system and electronically transmitting the programs to the automated production system. Therefore, the time required to do the programming for the next job does not interrupt production on the current job. Changing the physical setup between the parts is accomplished by making the changeover offline and then moving it into place simultaneously as the next part comes into position for processing. The use of pallet features that holds the parts and transfer into position at the workplace is one way of implementing this approach. The relative positions of the three types of automation for different production volumes and product varieties are depicted from the Figure below. Figure 1.1: Relative positions of three types of Automation HARD AUTOMATION AND SOFT AUTOMATION In hard automation, specialized machines have been designed and developed for high volume production. However, when each production cycle ends and new models of the parts are to be introduced, the specialized machines have to be shutdown and the hardware is changed (retooled) for the next generation of models. Since periodic modification of the production hardware is required, this type of automation is referred to as hard automation. Here the machines and processes are often very efficient, but they have limited flexibility. In soft automation (flexible or programmable) greater flexibility is achieved through the use of computer control of machine.

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Soft automation is an important development, because the machine can be easily and readily reprogrammed to produce a part having a shape or dimensions different from the one produced just before it. Because of this characteristic, soft automation can produce parts having complex shapes. Since the computer controlled mechanical manipulators can be easily converted through software to do a variety of tasks, they are referred to as examples of soft automation. A qualitative comparison of the cost effectiveness of manual labor, hard automation and soft automation as a function of the production volume, is shown in Figure below. Figure 1.2: A qualitative comparison of cost effectiveness of manual labor, hard automation and soft automation It is evident that for very low production volumes, manual labor is the most cost effective. As the production volume increases, say at point V1, the robots become more cost effective than the manual labor. As the production volume still increases further, it eventually reaches a point V2, where hard automation surpasses both manual and robots in cost effectiveness. ROBOTICS Definition: The official definition of Industrial Robot is provided by Robotics Industries Association (RIA), formerly the Robotics Institute of America (RIA). “An industrial robot is a reprogrammable, multifunctional manipulator designed to move materials, parts, tools or special devices through variable programmed motions for the performance of a variety of tasks”. An industrial robot is a general purpose, programmable machine possessing certain anthropomorphic (humanlike) characteristics. The most obvious characteristic of an industrial

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