cai 4th.pdf

8/9/2019 cai 4th.pdf

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Fourth Assignment

Industrial Control and Automation 2014/2015

João Carvalho nº 62905

1 Robot

a) A robot is an articulated mechanical device that is also reprogrammable, that can perform autonomous tasks

by using it´s processing capabilities

Obtain information of it´s surrounding by using sensors;

Make decisions about what task to perform by accessing information gathered by the robot

and inserted into the robot à priori;

Manipulate objects in its surrounding through the use of actuators;

One of the main advantages and goals of robotics is to release humans from performing hard, repeatable and

hazardous work tasks

Advantages:

Robots can substitute humans in hazardous and uncomfortable work environments;

A robot can perform its work cycle with a consistency and repeatability that cannot be

attained by humans;

Robots can be reprogrammed and equipped with different tooling to perform a different

task;

Robots are computer controlled and so can be connected with other robots in order to

achieve integrated manufacturing;

In terms of disadvantages we have a higher vulnerability to virus development, more maintenance is alsorequired, and finally it also requires a more strict control policy and high initial capital investment.

b)

A manipulating robot is a reprogrammable manipulator, multifunctional, designed to move materials, parts,

tools or special devices in variable movements programmed to perform a set of tasks;

Regarding manipulators it´s a robot arm with industrial applications that have a rigid body/link that are

connected by joints (revolute or prismatic). Also have a drive (electrical or hydraulic), and finally an end

effector or tool mounted on a flange or plate secured to the wrist joint of the robot.

The robot arm executes movements is space transferring objects and tools point to point, oriented by the

controller. The actuator in the extremity of the arm executes the tasks.

c) These industrial robots can be classified accordingly to the number of joints, the type of control and actuatorsand also it´s geometry.

But normally they are classified accordingly to the type of joint, because they are one of the major things that

restrict the degrees of freedom of the robot.

Linear joint (L): allows the movement of the links in a linear way;

Rotational joint (R): rotation movement relative to the perpendicular axis of the joint between the two links;

Torsion joint (T): rotation movement relative to the parallel axis of the joint between

the two links;

Revolving Joint (V): rotation movement with parallel axis to the entry link ( closest to

the basis) and perpendicular to the exit;

There are several robot configurations possible such as Cartesian (PPP), Cylindrical (RPP), Spherical,

Articulated (RRR), Scara (RRP), hand coordinate;

The configuration can affect the possible tasks to perform, for instance for spot welding, loading & unloading

it´s used a sequence of discrete points in a point to point control. For painting, gluing or arc welding we use a

controlled path motion in a prescribed path.


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d) The programming system of the robot can be structured, object oriented or dedicated, and can be implemented

in different platforms using different programming language. The controllers used nowadays are

microprocessors and have several communications interface.

When robot joints are operated at high speeds and undergo fast accelerations, the modelling of the robot

manipulators becomes a complex mechanism since we need to consider centrifugal and Coriolis forces andstudy their behavior on the system, for that we will use dynamic programming.

It is clear that the system programing can affect the system performance and versatility because we can addmore constraints to the system and choose performance index in order to limit velocities, torques, and even

derivatives of the acceleration in order to protect the robot from mechanical failure and increase its reliability

e) The ability to communicate within an informatics system in an industrial context, allows the integration of

several manipulators robots within an industrial floor.

The most important aspect is the ability to interconnecting robotic systems and controllers, this leads to aincrease in modularity and flexibility when compared to traditional wired systems, by integrating information

and opening communication ports to the robot controllers inside a factory, it is now possible to interface robotic

work cells to the internet, allowing in that way to remote site monitoring and control.

2 Remote Manipulators

The remote manipulators are different from a fixed automation system due to the fact of being flexible, i.e. programmable.

The robot is able to adapt to changes in the process, by the means of his sensing system and its actuators. One fundamental

tool that allows this flexibility his it´s computational vision that transforms a image in a command or control interface.

The remote manipulators normally have a higher degrees of freedom than fixed manipulators.

3 Automated Guided Vehicles

A AGV is an automated guided vehicle, that is programmed by an computer system to move around the factory floor

delivering parts to work stations or removing waste, it´s main characteristics are:

Automation of loading/ unloading

Command

Repeatability and precision

Cargo capacity and robustness

Interface with the external environment

Synchronism with external environment

The main difference between the AGV´s and the manipulators, is that the manipulators have a fixed based, and the

AGV’s have a locomotion system (wheels, caterpillar, paws), this characteristic makes them suitable for logistics and

supply chain operations.

In terms of industrial purposes it´s suitable not only for movement of raw materials and other products, but also to perform operations that are in separate physical locations within the factory.


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4 AGV’s Economic Implications

If we take in account that in an industrial environment one of biggest operational costs are labor related, agv ’s have

higher productivity than people and special suitable for transportation operations because they have a relatively high cargo

capacity and an adequate speed of movement.

This can result in more efficiency in all the supply chain activities, and reduce costs significantly, despite the maintenance

costs for this vehicles being relatively high.For example within a warehouse AGV’s the real time control of this systems allows a precise identification of the location

of each product and it´s path, reducing in this way inventory costs, reducing the time of response to change, better work

environment, reduction in damages of materials.

The main economic factors to take in account while selecting an AGV are: navigation system (laser, magnetic strips, optical

guide) autonomy of the batteries, charging times for the batteries. There are several case studies of AGV´s implementation

in industry ( Soporcel, Kiva…) and all of them report a very high return of investment and a low payback period.

5 Fixed and Flexible Automation

The fixed automation are related with dedicated systems for serial processing due to the execution of fixed and specific

tasks, low operations costs, large production batches and ease to control and efficient.

The flexible automation appeared due to the necessity of having reprogrammable robots, capable of performing multiple

tasks with easy adapt to variations. And also to small and medium scale production volumes, however this flexible

automation systems require more rigid maintenance.

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