Man-Machine System

a system consisting of a human operator or group of operators and a machine, by means of which the operator performs a task involving, for example, the production of material goods, the management of some type of operation, or the processing of information. Human labor in a man-machine system is based on interaction according to received information with both the object of labor or control and the machine through the mediation of control elements.

Interest in man-machine systems arose in the mid-20th century, when systems of various kinds became with increasing frequency the objects of technical planning and design. The effectiveness of these systems, which included those for the control of production, transportation, communications, and space flights, was largely determined by the activity of the human operators. The combination of human abilities and capabilities of a machine or complex of technological devices significantly increases the effectiveness of control. Although there is a joint performance of control functions by the human operator and machine, each of the two components of the system is governed in its work by its own unique rules. The effectiveness of the system as a whole is determined by the extent to which characteristic features of the operator and machine, both limitations and potentials, are identified and taken into account when building the system. These features are most fully identified in the process of coordinating the external, that is, technological, means of action and the internal means of action, that is, means inherent to the operator. Coordination includes the construction of information and conceptual models.

The information model is a representation, organized according to a definite system of rules, of the states of the object of labor or control, the man-machine system itself, the environment, and the procedures for acting upon these states. Physically speaking, information models are built using data display equipment. With an information model at hand, the operator uses his own knowledge and experience to formulate a conceptual model—the aggregate of his own ideas about the goals and objectives of the labor activity and about the states of the object of labor, the man-machine system itself, the environment, and the procedures for acting upon the states.

One of the key problems in constructing man-machine systems is the optimal distribution of functions between the operator and technological devices, that is, determining which operations must be performed by the operator and which by the machine to ensure the required effectiveness. There are two basic variations in the distribution of functions. In the first, the operator merely monitors the machine performing the task and confirms the result; in the second, the operator and machine must perform certain motions jointly. Here, a result cannot be obtained without joint operation. The first variation is a type of parallel organization of interaction between the operator and machine, while the second reflects a sequential, or stepwise, organization. In choosing one variation or the other, consideration must be given to methodological factors relating to the social function of man as the doer of labor and to the practical recommendations of management science, including recommendations on the organization of control at the higher levels of the system. Assessments from engineering psychology and results from studies on the psychophysiological functions of man should have an important place in these considerations. According to current ideas, an efficient, and even an optimal, distribution of functions should be based on quantitative evaluations of the quality of task performance by the operator and by the machine and on evaluations of the effect of this quality on the overall effectiveness of the system.

No uniform classification of man-machine systems has yet been made. Human functions in such systems that reflect a fundamental change in the technological method of linking man and machine may serve as the distinguishing criterion. “Labor,” wrote Marx in describing automated production, “is now not so much part of the process of production as it is a role whereby man assumes the attitude of controller and regulator in relation to the process of production. Instead of being the main agent of the production process, the worker assumes a place alongside the process” (K. Marx and F. Engels, Soch, 2nd ed., vol. 46, part 2, p. 213).

There are five basic classes of man-machine systems. In the first, the human operator is included in the technological process, to which he must constantly attend. He is guided in his work by instructions, which cover virtually all possible situations and solutions. Operators at transfer lines and operators who receive and transfer information are part of this type of man-machine system. In systems of the second class, operators monitor and control a process. Operators in radar systems and traffic controllers in transportation systems are part of these systems. The third class of man-machine systems requires the operator to issue commands to robots, manipulators, and machines that amplify human muscular energy. In systems of the fourth class, the operator acts as an investigator. Decipher clerks and computer operators are examples of operators in this class. In systems of the fifth class, the operator is called upon to make management decisions. Organizers, planners, and executives work with systems in this class. In the second, fourth, and fifth classes of systems, the operator can set up a dialogue with the machine. Here, the operator and machine alternate in performance of the task.

Study of man-machine systems can and must be carried out as an investigation of the functional whole. Treating the human being as a special component in a technical system makes it possible to increase the effectiveness of the system. This approach, however, is not without limitations; by treating man as a “black box,” both the social nature of labor and the role of man as the doer of labor are overlooked. The relation between man and machine is above all a relation between the doer of labor and the implement of labor.

The basic difficulty in studying man-machine systems lies in the need to combine research from such different branches of science as physiology, engineering, psychology, human-factors engineering, and cybernetics, each of which has its own methodology and terminology.