Dane oryginału: Robotyzacja procesów produkcyjnych

Copyright © by Wydawnictwo Naukowe PWN SA

Warszawa 2017

Polish language translation: Agnieszka Adamczyk

Reviewers: Prof. Andrzej Buchacz, The Silesian Technical University

Prof. Zbigniew Koruba, Kielce University of Technology

Cover design and title pages: Przemysław Spiechowski

Photo on the cover: PP77LSK/Shutterstock

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English language editor: Małgorzata Kopczyńska

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eBook created for Polish Scientific Publishers PWN by: Marcin Kapusta / konwersja.virtualo.pl

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Polish Chamber of Books

Copyright © by Wydawnictwo Naukowe PWN SA

Warsaw 2019

eBook based on printed edition from year 2019, (1st ed.)

Warszawa 2019

ISBN 978-83-01-20411-2

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Table of Contents

1. Introduction

2. Basic concepts

2.1. Definitions of robots

2.2. Special uses of robots

2.3. Industrial robotics versus automation

2.4. Classification of industrial robots

2.5. Construction of industrial robots

2.6. Technical parameters of industrial robots

2.7. Selected constructions of industrial robots

2.7.1. Five- and six-axis articulated robots

2.7.2. Parallel robots

2.7.3. SCARA robots

2.7.4. Portal robots

2.7.5. Two-armed robots

2.7.6. Collaborative robots

2.8. Coordinate systems of industrial robots

3. Effectors of industrial robots

3.1. Grippers

3.2. Robotic tools

3.3. Tool change systems

4. Sensors and sensor systems of industrial robots

4.1. Measurement sensors

4.2. Vision systems

5. The use of industrial robots in selected applications

5.1. The advantages of robotization

5.2. Robotic welding stations

5.3. Packaging machines versus robots

5.4. New markets for robotics

5.5. Work in dangerous conditions

5.6. Constant development of robotics

6. Analysis of robotic sorting, packaging and palletizing processes

6.1. Designing robotic cells for sorting, packing and palletizing of products

6.2. Construction of robotic sorting, packaging and palletizing work cells

6.2.1. Robotic sorting of products

6.2.2. Robotic packaging of products

6.2.3. Robotic palletizing of products

6.3. Safety and work environment at sorting, packaging and palletizing workstations

6.4. Examples of robotic packaging and palletizing stations

7. Robotic processes of welding, laser welding and cutting

7.1. Robotic processes of arc welding

7.2. Robotic processes of welding

7.3. Examples of robotic welding stations

7.4. Robotic processes of laser cutting and welding

7.5. Summary

8. Robotic machine tending

8.1. Robotic machine tending of machining centers

8.2. Robotic tending of plastic forming stations

9. Robotic assembly

9.1. Types of assembly stations

9.2. Summary

10. Programmable Logic Controllers (PLCs) on robotic production cells

10.1. Role of PLCs in industry

10.2. Construction, operation and programming of PLCs

10.3. Immigration of PLCs to robot controllers

10.3.1. Examples of solutions

10.4. Summary

11. Safety systems at robotic workstations

11.1. Machine safety in the aspect of standards requirements

11.2. Safety categories

11.3. Safety in a robotic production cell

11.4. Safety systems vs. control systems of industrial robots

11.5. Summary

12. The market of robotics and the review of new solutions and trends

12.1. Density of robotization

12.2. Predictions on the development of robotization

12.3. The main factors influencing the development of robotization

12.4. Trends in the development of industrial robots

12.4.1. Construction of manipulators

12.4.2. Generations of controllers

12.4.3. Development of operator panels – Teach Pendant panels

12.4.4. Development of safety systems of industrial robots

12.4.5. Development of industrial robots programming environments

12.4.6. Integrated systems for quick implementation

13. References

Footnotes

1. Introduction

Robotics is a field of technical knowledge that deals with the construction of robots, their control, their programming and application in various domains of science and technology. It is highly interdisciplinary and combines knowledge from many other fields (mechanics, automation, electronics, IT etc.). Today, one can easily notice the presence of robots in industry, medicine, transport, building engineering, administration, the army, agriculture, and space. Robotics is used wherever work is particularly onerous, monotonous and dangerous for humans. The good examples are factory production lines (where, among others, the processes of packing, palletizing, painting, welding and cutting, and manipulation are carried out), work in harmful conditions (low and high temperatures, radiation, sparks and chemical contamination) or unexplored areas, such as sea depths and the outer space. Although the robotics has been developing very fast for many years, the role of humans is still superior. It is possible that in future, the tasks done currently only by humans (including constructing, programming and maintaining) will be carried out also by robots. Already today it is obvious that autonomous workstations with limited human service are the future of robotics industry. The basic branches of robotics include:

• theoretical robotics (theories of robots and manipulators),

• general robotics (the methods and the economic and social aspects),

• metrological robotics (robots for measuring and control purposes),

• robotics of locomotion machines (single- and multi-legged, wheeled, crawling, and wheeled-foot machines),

• medical and psychotherapeutic robotics (robots for surgical and prosthetic and psychotherapeutic purposes),

• industrial robotics (robots in the machine, food, paper and mining industries),

• non-industrial robotics (robots for underwater, military and rescue works, and in the space),

• service robotics (robots for office and cleaning works),

• micro-robotics (miniaturization of robots).

The concept of 'robotics' is very closely related to the concept of a 'robot'. First mechanisms came into being at the times of Plato (circa 400 BC), when, according to the historical sources, first automatic machines (toys capable of making simple movements) were created. In turn, the water clock is considered the first robotic mechanism. It was invented probably around 250 BC and was intended to turn the hourglass. It obtained the name of a robotic device thanks to the cyclically repeated action to which it was intended. Rapid development of movable mechanisms started in the Middle Ages, when constructors were building up mechanically complex clocks and movable figurines driven by either water energy, springs or gravitational forces. It is easy to notice that an attempt to recreate the movements of humans and animals was the common feature of all created mechanisms.

Where did the word 'robot' really come from, used as a term to define a certain type of machine?

'Robot' means a worker in the Czech language. In 1920, the Czech writer Karel Čapek used the word 'robot' to describe artificial, intelligent creatures deprived of human feelings. In his play titled 'R.U.R. – Rossum's Universal Robots', Čapek created a vision of the world in which the only way to survive is to strive for technical development, and anything that does not serve the progress is not important.

Čapek wrote: 'And to manufacture artificial workers is the same thing as to manufacture gasoline motors. The process must be of the simplest, and the product of the best from a practical point of view (...). And what sort of worker (...) is the best from a practical point of view? (...) The one that is the cheapest. The one whose requirements are the smallest. Young Rossum invented a worker with the minimum amount of requirements. He had to simplify him. He rejected everything that did not contribute directly to the progress of work. In fact, he rejected man and made the Robot.'[1]

The term has been adopted all over the world. Today the word 'robot' refers to any technical device which is intended to replace some of human manipulative and locomotive functions and has a certain level of machine intelligence. People's aspiration has always been to create a machine mirroring their own image (a humanoid). With the development of technology, robots were equipped with increasingly better, more modern energy sources, sensors, actuators and control devices. At the beginning of the 20th century, when people began using electricity at a large scale, the robots were equipped with microphones, photocells and loudspeakers, and wireless devices began to be used to control them. In the 1950s, the first models of manipulative machines with software control were produced.

The pioneers of robotics certainly include a designer Joe Engelberger who, together with his friend George Devol, constructed an angular and squat machine called UNIMATE in 1958.

In 1961, UNIMATE (Fig. 1.1) was incorporated into the technological process at the General Motors plant in Ewing Ternstedt in New Jersey.

Fig. 1.1. The UNIMATE robot at the Volvo 650 assembly line (source: http://www.volvocargent.be/nl/)

One of the first tasks of the robot, equipped with a telescopic, hydraulic arm with a joint, was to transport die castings from an assembly line and weld these parts on auto bodies. Later, the robot was also used on assembly lines, including the Volvo cars assembly line. For about 50 years it worked approximately 100,000 h and it delineated the new direction for industry.

The possibility of using a machine which can work 24 hours a day without an operator confirmed the sense of equipping production lines with efficient, programmable machines. The possibility of replacing the three-shift, hard work of the employees triggered mass robotic production for the needs of industry (in the United States in 1963, in Europe and Japan in 1968, in Poland in the early 1970s). Today UNIMATE is an exhibit at the Smithsonian Institution and it is difficult to compare it with robots whose development is currently going along with the avalanche development of microprocessor technology. Today, the widely discussed matter is not a workforce but robot's working environment, the constructors want to empower machines as much as possible, equipping it with sensors that can simulate the human senses. So far, out of the five senses (sight, touch, taste, hearing, and smell) only sight and touch have been widely applied in robotics. Currently, the scientists all over the world are carrying out intensive research on voice control, identification and recognition of a position of the object in three-dimensional space as well as on distance sensors. The full use of three-dimensional systems has become possible thanks to implementing the advanced vision, ultrasonic and laser sensors. Nowadays, the locomotive functions are a great challenge and the scientists are looking for the solution of how to create a grip which would have the properties similar to a human hand? Therefore, the scientists are trying to use electrostatic phenomena and adaptive grippers (adapting their shape to the shape of the object). What devices should be used to replace hydraulic cylinders and electric actuators? How to miniaturize drives? There are still many more questions that today's engineers are trying to answer.

Another separate problem of robotics are control systems in which a simple control of the location is not enough anymore. Today, such multiprocessor systems are being created which allow to create multithreaded applications to cooperate with the surrounding environment, and this stimulates the development of interfaces connecting the two worlds and develops programming techniques. It seems that the best solutions are high-level languages (easily learnt by humans), which allow robots to operate in real time.

2. Basic concepts

Robotics is a field of technical knowledge and, as in most areas, certain principles apply to it. The laws of robotics arose mainly due to considering the threats to the mankind, which may result from high technological advancement of machines. According to the assumptions, robot constructors should respect the defined laws of robotics to prevent such threats [I.28].

The first three laws were formulated in the story titled 'Runaround' in 1942 by the writer Isaac Asimov[2] and they form the so-called canons of robotics. Today, due to the development of robotics and microtechnology, additional laws are being formulated and their role is to cover all the aspects of robots' growing functionalities.

The laws of robotics

The first law:

A robot may not injure a human being or, through inaction, allow a human being to come to harm.

The second law:

A robot must obey the orders given it by human beings except where such orders would conflict with the First Law.

The third law:

A robot must protect its own existence as long as such protection does not conflict with the First or Second Laws.

The fourth law:

A robot must reveal its robotic nature. Especially, a robot must not pretend to be a human being.

The fifth law:

The more complexed are the robot's sensor systems which ensure the perception of environmental conditions, in particular the possibility of autonomously determining actions with its control system, the simpler may the robot's construction be, up to a certain, acceptable degree. This acceptable degree depends on the goal that was set before the robot, and the possibilities of the robot to achieve that goal.

Later, in 1985, in the story 'Robots and Empire'[3], Asimov added the so-called the zeroth law, which became the supreme law: A robot may not harm humanity, or, by inaction, allow humanity to come to harm.

2.1. Definitions of robots

As is with the term 'automation', the term 'robot' is explained in different ways, which depend on a specific context. According to Wikipedia:

A robot is a machine–especially one programmable by a computer–capable of carrying out a complex series of actions automatically. Robots can be guided by human control or the control may be embedded within, or by a set of general rules that are transferred into a robot using artificial intelligence techniques. Robots often replace human beings at monotonous, repetitive activities, which robots can perform much faster than people. Their main tasks comprises those which are dangerous to humans, for example related to the manipulation of substances harmful to health or staying in a hostile environment.[4]

The term 'robot' is also used to name autonomously operating devices which receive information from the environment with their sensors and influence it with the help of the effectors. Such robots are built by researchers investigating artificial intelligence or cognitive science to model cognitive abilities, the way of thinking and behaviours of animals or people. Despite the huge progress in these areas, the goal of creating a robot whose intelligence would, at least, match the human intelligence, still seems very distant.

The term 'robot' refers also to a general concept used to define existing in reality or imaginary automata and machines resembling of humans or animals. We will rather use the word 'robot' to name a human-shaped mobile doll than a highly specialized modern dishwasher – even though the operation of this device fully agrees with the definition of a robot. The reason for this is probably our, humans' anthropomorphism.

Industrial robotics is a field of robotics which deals with applying robots and industrial manipulators to robotised production processes (including welding, painting, palletizing, assembly, pressing, handing, product inspection and testing).

In different parts of the world, the term 'industrial robot' refers to differently configured machines. For instance in Germany, it is required that a robot had more than 3 active axes, although this definition is not commonly accepted. Different definitions of a 'robot' are used in many countries, such as Japan or the USA (in Japan, for example, manually operated manipulators are also classified as robots). Therefore, it is very difficult to assess the statistical level of automation and give the precise number of robots.

Manipulating industrial robot is an automatically controlled, programmable, multitasking machine with many degrees of freedom, and of manipulative and locomotive abilities. It may be stationary or mobile, and it is utilized for many important industrial tasks.

In the area of robotics, the robots called 'intelligent' seem to be the most interesting. The term 'intelligent' refers to flexible machines which can change their behaviour under the influence of external factors, are able to manipulate physical objects in a real environment, and to react to external events in an adequate manner. The appearance and size do not affect the level of a robot's intelligence, and the most important criterion is the range of different sensors a robot is equipped with.

2.2. Special uses of robots

Apart from their industrial applications, robots are widely utilized for special purposes. In such cases, the cost of using the machine is not recalculated, because it most often works in extreme conditions, which may be very hazardous for living organisms. The special areas include as follows:

• the outer space,

• medicine,

• laboratories,

• production in 'sterile rooms',

• military applications,

• special industrial and building solutions.

The outer space

In the outer space, a human is a very expensive operator. The training of astronauts, their number and technical systems (such as life-sustaining systems) cause that on Earth huge costs associated with the human factor are borne. Therefore, in space missions, where there is a danger of losing one's life, automatic systems are preferred (Fig. 2.1).

Fig. 2.1. The Canadarm robot arm in space (source: NASA TV)

The outer space applications automated by using robots include as follows:

• carrying out experiments in unmanned space laboratories,

• intercepting and refuelling the satellites and repairing the faulty ones,

• investigating planets using mobile robots (Fig. 2.2).

Fig. 2.2. OPPORTUNITY rover (source: NASA TV)

Laboratories

Robots are utilized in medicine, chemistry and biotechnology for safety reasons and because of their high accuracy. In the above-mentioned fields, the most frequently utilized robots are those of small sizes because they usually operate in a very small space. In laboratories, hermetic workstations are created, where robots perform experiments in sterile conditions (Fig. 2.3).

Fig. 2.3. CSDA10F Robot by Yaskawa Motoman (source: https://www.yaskawa.eu.com/)

Medicine

Manufacturing of medical products requires the highest degree of precision and hygiene. That is why many products of this type are made in sterile rooms, without human factor. Robots perform all the functions, from transport, through an assembly, to packaging in such sterile production rooms. In the future, medical robots will support surgical teams in carrying out surgeries. Teleoperators are already widely utilized today, supporting surgeons' work by mimicking their movements. Of course, scientists are working on robots capable of performing surgeries in an autonomous manner. Their work will be supported by the data and images coming from the tomographs. A good example of such a robot is Robin Heart – Polish surgical robot (Fig. 2.4), which was developed by a team of scientists from the Professor Zbigniew Religa Foundation of Cardiac Surgery Development in Zabrze. This is one of the most modern robots supporting surgeries in the world.

Fig. 2.4. Robin Heart surgical robot (source: http://automatykaonline.pl/)

Sterile rooms

Some production processes, such as production of semiconductors, combined circuits or magnetic media, require appropriate climate conditions and high purity of air. Such processes are hermetized in so-called clean rooms. The special climate and filter installations ensure suitable production conditions, such as constant temperature, humidity and dust filtering.

In clean rooms, robots are most often utilized for transportation purposes, therefore their high precision and repeatability of motions are required (Fig. 2.5). Additionally, the robots must meet the requirements of room sterility and they should not emit more dust than the filter installed in the given room can absorb.

Fig. 2.5. CSDA10F Robot by Yaskawa Motoman in a sterile room (source: https://www.youtube.com/)

Military applications

The development of technology has always been inextricably connected with the use of modern technologies for military purposes. The news concerning modern military robots which support soldiers on the battlefield appear increasingly often in the media around the world. Robots are now utilized in air, water and on land, where they perform particularly dangerous tasks (Fig. 2.6).

Fig. 2.6. MAARS mobile robot (source: http://www.precisionremotes.com/)

2.3. Industrial robotics versus automation

Industrial robotics is tightly connected with automation. Three levels of automation can be distinguished in this context:

1. Automation with fixed functionality. In the case of a large number of products (for instance, cars) the best economic solution is to purchase the optimal equipment for the production, regardless of the high costs caused by the specificity of the production process. Thanks to the division of the costs by the number of products, the unit price may be lower than when using other methods of production.

2. Programmable automation. For the production of various products in short series the equipment should be designed in such a manner that it can be easily adapted to new conditions. Subsequent adaptations allow to manufacture various products, and the cost of the entire project can be distributed among all manufactured products.

3. Flexible automation. The mechanism of flexible automation consists of a number of commonly useful production links which are connected by the transport and storage system. The central production controller coordinates the distribution of the components to work cells and also delivers to robots all the necessary control programmes. The production system can process both a larger number of product batches, and several single products at the same time.

Flexible production is increasingly often referred to as the basic industrial production system of the future. The economical solution seems to be the one using intelligent robots which can be utilized for both the production and transport purposes. Already today, robots must plan and supervise their functions, recognize the environment and communicate with other machines in order to act autonomously and to achieve effective cooperation with one another. The expanding distributed systems require the use of an increasing number of sensors and connecting all cooperating machines to a data exchange network.

Currently, thanks to the use of artificial intelligence, robots are able to use vision systems in industrial environments. The camera, the robot and the robot controller connected to the computer allow the robot to see, to move and to react in a manner similar to a human [I.19].

2.4. Classification of industrial robots

Machines and tools are categorized according to their functions. If they have several functions, they are classified regarding their main functions. Because of their large number of functions, robots can be classified into different groups. Activities such as welding or painting could justify the inclusion in welding or painting machines, but generally, robots belong to the group of manipulative devices.

There are many criteria for the classification of robots (Fig. 2.7). The most common classifications can be made according to: robots' kinematic structure, the construction of the kinematic unit, the control and type of drives [I.9].

Fig. 2.7. Classification of robots

Classification of robots according to their kinematic structure

• stationary (unable to move in relation to the ground):

– with open kinematic chains (serial connection of kinematic pairs – Fig. 2.8),

Fig. 2.8. Robots with open kinematic chain: a) Cartesian robot by WObit (source: http://www.wobit.com.pl/), b) IRB2600 ID articulated robot by ABB (source: http://www.abb.com/), c) SCARA robot by Adept (source: www.adept.com/)

– with closed kinematic chains (parallel connection of kinematic pairs – Fig. 2.9):

▫ tripods, delta type (three arms forming a closed kinematic chain),

▫ hexapods (six arms forming a closed kinematic chain);

Fig. 2.9. Robots with closed kinematic chain: a) tripod IRB360 by ABB (source: http://www.ABB.com/), b) F200i hexapod by FANUC (source: http://FANUC.com/)

• mobile (able to move in relation to the ground, Fig. 2.10):

– moving along a fixed track (often utilized on factory production lines),

– autonomous – able to move freely.

Fig. 2.10. Mobile robots: a) KL3000, by KUKA, on a guiding track (source: www.kuka.com), b) SUMMIT by Robotnik (source: www.robotnik.eu)

Classification of robots according to the construction of kinematic unit:

• monolithic – robots of the fixed structure of the mechanism, that is, the user has the possibility to attach the exchangeable tips (effectors) to the arm;

• modular – the user has the possibility to construct robots from the elements (segments) provided by the manufacturer;

• pseudo-modular – these are actually monolithic robots, but the manufacturer allows to exchange the selected modules.

Classification of robots according to the control method:

• sequential – robots equipped with a control system which performs motions according to the defined algorithm;

• task-based – robots performing tasks according to a certain algorithm, which describes not only the position and the orientation but also the required speed;

• adaptive – robots able to adapt to the environment (working envelope), thanks to the additional mechanisms (sensors, adaptive algorithms);

• teleoperators – their main feature is the direct control by the operator or a computer (PLC).

Classification of robots according to the types of drives:

• pneumatic – actuators: linear, swinging cylinder, rotary motor;

• hydraulic – linear actuator and rotary motor;

• electric – AC/DC motors, stepping motor;

• combined – a combination of the above solutions.

Other types of robots

Currently, due to the dynamic development, robots equipped with two arms constitute a separate group. (Fig. 2.11). Such robots appeared in the offer of almost all major robot manufacturers in the world. This is undoubtedly related to the adjustment of safety regulations, which allow to closer cooperate the humans and the machine. In addition, it allows to acquire another production area – a complex assembly.

Fig. 2.11. Two-arm robots: a) a robot by Comau (source: www.comau.com), b) YUMI by ABB (source: www.abb.com), c) a robot by EPSON (source: www.epson.com), d) CSDA10F by Yaskawa Motoman (source: www.youtube.com), e) UR5 dual arm 2 by Universal Robots (source: www.universal-robots.com/)

Collaborative robots are a new group of robots. Their development is the next stage of bringing robots closer to people and ensuring safety consistent with the established directives.

2.5. Construction of industrial robots

The construction of industrial robots depends on the production needs. Replacing people at their workplaces has forced (and still does, especially in the case of modernization of existing workstations) the use of machines which could fit in a given workplace and could operate the tools that were previously used by man (e.g. a welding torch, a drill, a spot welding gun). Hence, the payload of robots, the number of degrees of freedom and their range of operation are comparable to the capabilities of man. Naturally, the use of tools by robots requires the preparation of appropriate power supply and control interfaces, as well as the sending of necessary media. Currently, due to the high level of technological development and the creation of sophisticated technological tools, it is noticeable that building multiple versions of robots of a given type (e.g. ABB IRB 2600 robot is available in versions 12 and 20 kg with a range of 1.65 and 1, 85 m, respectively) allows to select the appropriate robot for a given technological process (e.g. a robot with a payload of up to 12 kg for MIG/MAG welding; for laser welding – a robot with a payload of up to 20 kg, due to the weight of the laser head).

The main components of the robot system are as follows (Fig. 2.12):

• the manipulator (mechanical unit),

• the controller with power supply,

• the programmer (Teach Pendant),

• the effector (a specialist tool or a gripper),

• drives,

• the sensors (internal and external),

• the robot additional axes (track, positioner).

The robot system is responsible for controlling the operation of all devices included in it.

Fig. 2.12. The main components of the robot

Robot manipulators

The manipulators of industrial robots are designed to ensure the performance of tasks in a defined working envelope. Due to the fact that in most solutions robots replace people, their working envelopes are similar to those occupied by manual workers. The construction itself, if the appropriate range of the tool and the reachability of points inside the working envelope are ensured, must be of an adequate stiffness to perform the tasks with the predefined accuracy.

The basic elements of the manipulator are as follows (Fig. 2.13):

• the robot base – the first part of the robot's kinematic system,

• the arms – kinematic elements of the robot,

• the axes – active robot connectors (drive motors and transmission systems),

• the robot's wrist – a robot's motion system (usually rotating) connecting the robot positioning system.

Fig. 2.13. Robot construction (source: KUKA)

The construction elements of a robot, such as a robot's base body and arms, are most often made as castings containing slots for active axes servomotors. The drive of the axes can be transmitted by gears or toothed belts (Fig. 2.14).

Fig. 2.14. Transmission of a drive using a toothed belt on the fifth axis of the LR Mate 200iC by FANUC

In case of robots with a parallel kinematic structure, the robot's drive is carried out by the servomotors moving the appropriate arms, whose resultant motion is responsible for moving the robot's wrist (Fig. 2.15). Such robots, depending on the function they are to perform, have a four- or six-axis structure, where the rotation around the fifth and sixth axes is carried out via a special wrist.

Fig. 2.15. Transmission of drives on the axes of M-1iA by FANUC

In robots with a high payload, the drive components (servomotors) are placed outside the structure due to their dimensions. Such a solution provides easier cooling of the servomotors (Fig. 2.16).

Fig. 2.16. The position of servomotors on manipulator constructions in R-2000iC robot by FANUC and in IRB 6620 by ABB

In smaller constructions (if possible) the drives and the power cords are installed inside the body, which increases the tightness of the structure and allows to utilize the manipulator in high humidity or dustiness, or where a high degree of purity is required. In addition, for smaller robots, the often used solution is to relocate the part of the robot's inputs/outputs, both electric and pneumatic, to the forearm (Fig. 2.17), thus enabling easier connection of accessories (e.g. the grippers, technological tools).

Fig. 2.17. Location of the robot's input/output sockets in the forearm of the robot manipulator (from the left): Agilus by KUKA, LR Mate by FANUC, IRB 120 by ABB

Footnotes

[1] Čapek, Karel: 'Rossum's Universal Robots', translation: Paul Selver and Nigel Playfars.

[2] Isaac Asimov, 'Runaround' in: 'Astounding Science Fiction', Street &Smith, USA, 1942.

[3] Isaac Asimov, 'Robots and Empire', Doubleday Books, USA, 1985.

[4] https://en.wikipedia.org/wiki/Robot.