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Industrial Robots
Oct 1, 1996

1. Introduction

The word ‘robot’ was first used in the 1922 play R.U.R. by the Czech playwright Karel Capek: the title is an acronym for Rossum’s Universal Robots which become so sophisticated that they take over the world. ‘Robot’ is compounded from the Czech words ‘robota’ or work, and ‘robotnik’ or serf (Capek. 1923).

The use of industrial robots, first clearly identified in the 1960s, along with computer aided design (CAD) and computed aided manufacturing (CAM) systems, characterizes the latest trends in the automation of the manufacturing process (Roth, 1983). These technologies arc leading industrial automation through another transition, the scope of which is still unknown.

Growth of the robotics market has slowed compared to the early 1980s. The use of industrial robots is at present concentrated in rather simple, repetitive tasks which do not to require high precision. However, manufacturing market analysis predicts that early next century industrial robots will become increasingly viable in applications which require more precision and sensory sophistication such as assembly tasks. The automotive industry, where robots have been economically justified since the 1970s, will continue to be the leading user. However, the major growth of the US robot population will occur in non-automotive industries.

2. Robot classes and characteristics

Robots can be classified in many ways. To establish a generic classification system, we shall refer to dimensions or degrees of freedom or DOF.

The DOF of a mechanical system refers to the number of physical axes through which motion can occur. In robotics, DOF can often be equated with the number of joints in the robot.

Typical present-day industrial robots have from one to six-DOF, although more are certainly possible. For example, a wrist can be made more flexible by adding rotation to the twisting already in that joint. Similarly, a fourth DOF can be added to the shoulder, where the arm joins the base to allow additional rotation of the arm. Industrial robots are also classified by the mechanical configuration of the individual elements of the arm and actuators. Theses classifications are: rectangular class (X,Y,Z): cylindrical class (R,?,Z): spherical class (R,?,?); and jointed class (?1,?1,?). This classification begins with simple movements in a rectangular co-ordinate system such as the x-y co-ordinate system.

3. World’s robot population

More than 610.000 industrial robots are now at work according to a new annual publication by the secretariat of the United Nations Economic Commission for Europe (UN/ECE) and the International Federation of Robotics (IFR).

The world’s robot population grew by about 6% in 1993 compared with 8% the year before. These growth rates fall significantly short of those of 16-23% recorded in the booming late 1980s and early 1990s. However, in view of the deep recession which commenced at the end of 1990 in robot-using countries and resulted in large reductions in investment and industrial employment, growth in the robot stock of 6%-8% is still quite impressive. 

Japan accounts for more than half of the world robot stock. However, the net increase in Japanese robot stock fell sharply in both 1992 and 1993. In 1993, the net increase in the robot stock was only about a third of the record year 1990, underscoring the depth of the Japanese recession.

With 325 robots for every 10.000 persons employed in manufacturing, Japan has by far the world’s highest robot density followed by Singapore with 109, Sweden with 73, Italy with 70 and Germany with 62. As a result of falling employment in the manufacturing industry in 1992-1993, robot density increased rapidly in many countries even though the robot stock increased only modestly.

In most countries, welding is the predominant application area for robots, particularly for major motor vehicle producing countries, accounting for more than 20% of the total robot stock. In a few countries machining was the largest application area. Assembly was the largest application area in Japan, accounting for 40% of the total stock of robots. It is worth noting that in Japan assembly accounted for 50% of the net increase in stock while welding only had a share of 9%.After a solid recovery in 1994, the robot market is forecast to boom in the period up to 1998. Based on macroeconomics forecast of the development of world economics the UN/ECE and IFR forecast that the world stock of industrial robots will increase from some 610,000 units at the end of 1993 to over 830.000 units at the end of 1997. As the number of personnel employed in industry is falling, the density of robots measured as the number of robots per 10.000 workers will continue to surge. In terms of units, shipments are estimated to increase from about 54.000 units in 1993 to over 103,000 units in 1997.

While the robot market was expected to be somewhat hesitant in Japan in 1994 and 1995, it was expected to boom in the United States, Western Europe and the dynamic Asian economies. If growth and world trade gain momentum as predicted from 1995, the prospects for the robotics business seem extremely bright.

The potential for expansion of robotics is enormous. If other industrialized countries were to approach the robot densities of Japan and if industry in general were to reach only half the robot density of the motor vehicle sector, the robot stock would increase manifold, and this is not counting the potential for robots in the service industries. The following example gives an illustration of the potential: if industry in France and the United Kingdom were to achieve a robot density half that of the motor vehicle industry in those countries, the robot stock would more than double; if it reached half the density of the Japanese motor vehicle industry, the robot stock in those countries would increase more than 20 times.

4. Summary

The emphasis in this article has been on industrial robots and techniques currently used in that environment. The future of robotics depends on improvements in many technologies to reduce cost and increase the range of performance so that robots become effective in more environments. These technologies include motors, actuators, contact sensors, non contact sensors, mechanisms, lubrication, electronics, computers and artificial intelligence.


  • CAPEK. K. (1923) R.U.R.. Samuel French. London.
  • ROTH. B. (1983) Principles of Automation, in Future Directions in Manufacturing Technology, based on the Unilever Research and Engineering Division Symposium held at Port Sunlight, April 1983. Unilever Research. UK