An assessment of industrial robots: Capabilities, economics, and impacts

Abstract Production managers and engineers have always tried to find better and less expensive ways of making a product. In recent years their search has led them to consider the use of robots for jobs previously thought to require more judgment and flexibility than a machine can offer. Before robots are introduced onto the factory floor, though, their capabilities and limitations should be fully understood, and an effective implementation plan devised. The purpose of this article is to examine some of the important issues underlying this growing technology and to assess its impacts. In particular, robots have a variety of virtues that go beyond simple cost savings. In many cases they relieve factory workers of tasks that are tediously repetitive or dangerous. From management's viewpoint, though, a robot is justified only when a practical application exists. The simple transfer of objects between work stations, storage facilities, and transport systems was one of the first such applications. In high volume production these “pick and place” operations must be performed accurately and consistently, making them ideal for automation. Though largely an American invention, robots have not taken their place in many domestic factories as fast as they have abroad. Many companies have been reluctant to make the initial investment, particularly when faced with a surplus of capacity and labor, and no pressure to hold down prices. Now, however, heightened competition in many industries previously thought to be secure from foreign intrusion has led to a change in attitude. The need to hold on to existing markets, and in some cases even catch up, has inspired many doubters to take a second look. Not surprisingly, this has brought forth charges that some employers, lacking in social conscience, are substituting machines for people and adding to the nation's jobless roles. The issue has been on the table in labor-management disputes for decades with the machines generally winning out. To a large extent, the residue of unemployment that remains in the economy even in the best of times reflects the effect of change and the problems of adjusting to it. To date there is no evidence that an accelerated introduction of robotics will cause any noticeable disruption in the labor force. Although there may be isolated instances of dislocation, a management sensitive to the concerns of its workers should be able to make the transition smoothly, perhaps allowing excess personnel to shrink through attrition rather than layoff while retraining as many as possible. If we trace the history of programmable devices, we see that most of the early mechanisms were developed by the machine-tool industry. By today's standards, this equipment was slow, heavy, and precise, and was driven by very simple algorithms stored on paper or magnetic tape. Virtually no on-line decision-making capability existed and only fixed, repetitive motions were possible. Still, being programmable automation, these machines could be considered the first robots. As microelectronics became more refined, the repertoire of robot manipulators was extended to include more complex tasks. For example, acts requiring considerable on-line processing such as the creation of straight line motion and the initiation of movement in response to sensed input are now straightforward to implement. To understand better what distinguishes robots from their machine tool predecessors, an examination of their basic features is needed. All robots are composed of three interdependent components: manipulators, a power supply, and a controller. The manipulator is the mechanical structure consisting of linkages and joints that provide motion along different axes. Each separate axis is called a “degree of freedom.” The manipulator, or “arm,” usually has three degrees of freedom while an attachment to the arm, called the “end effector” or “hand,” can furnish an additional three. Still, a seventh degree of freedom can be attained by placing the entire robot on a traversing x-y plane. The power supply is the muscle of the machine. Hydraulic systems comprising an electrical pump, filter, reservoir, and heat exchanger are the most popular because of their reliability and physical efficiency. Pneumatic systems, on the other hand, are typically found on light-weight capacity robots and have the advantage that the air supply needed to drive them is often present in the factory at no additional cost. The third component of any robot is the controller, which may range in sophistication from simple air-logic values to complex micro- and minicomputers. The former are only appropriate for jobs requiring a limited sequence of operations while the latter are capable of sorting and executing thousands of steps. A microcomputer can process feedback pulses and decide which of many actions is called for. The ability to respond to a changing environment is what makes a robot superior to an automated machine. There are three senses used in feedback control: touch, hearing, and vision, with the first being the most common. Depending on the situation, touch determines how much pressure to apply or where to position the arm. The use of hearing to modify operations has received some attention, but mainly in a laboratory setting. Major commercial applications should come in the next five years in the form of voice instructions and system monitoring. Vision is the most advanced sense and is accomplished by processing an array of black and white dots from armmounted television cameras. Depending on the resolution of the dots and the speed at which the computer can process the arrays, the robot's vision can be stated in a four-level hierarchical system: detection, orientation, recognition, and identification. To identify an object from its surroundings, the computer has to precisely describe the object using the limits of its knowledge in conjunction with its resident database. As the technology evolves, more emphasis will be placed on an ability to perform a generic set of tasks rather than a set of broadly-based functions. The next generation of robots will include manipulators with fewer than five degrees of freedom trading off dexterity for speed and accuracy. They will typically work in units of two or more and be designed for specific types of tasks. Some will be light and fast and have large ranges of motion while others will be more like programmable fixtures. Indeed, the most successful applications of robots to date have been those in which the robot either does not contact the workpiece, as in spray painting, or grabs the workpiece to fix a reference, as in spot welding. Finally, it should be mentioned that the biggest impact that robotics is likely to have in the factory is in the area of redesign of workpieces for ease of manufacturing. Often when a part is redesigned so it can be assembled “automatically,” it also becomes much easier for humans to assemble. Study of design-for-assembly for manufacturability is an area that has traditionally been neglected and that has huge potential for increasing productivity.