Operator-machine systems analysis

Once potential ergonomic problems have been recognized and superficially evaluated for specific jobs or locations, the operator-machine system is used to categorize major conditions contributing to ergonomic problems. Operator-machine system analysis examines... 

Gertman, D. I., Haney, L. N., Jeirkins, J. P., Blackman, H. S. (1985). Operator Decision Making Under Stress. In G. Johannsen, G. Mancini, L. Martensson (Eds.). Analysis Design and Evaluation of Man-Machine Systems (Proceedings of the 2nd IFAC/IFIP/IFORS Conference, Varese, Italy). 

This data is assessed using activity analysis methods. These methods are apphed to different operators belonging to the same class, and consist in analysing the man-machine system in predefined contexts (chosen at the previous stage). The inputs/outputs of each operator are also measured and memorized, and his workload, visual strategies (using occulometric methods [1]), displacements, etc., studied. 

Goodstein LP. An integrated display set for process operators. Congrys IFAC Analysis, Design and Evaluation of Man-Machine Systems, Baden-Baden, September 1982. 

The purpose of the human reliability analysis is to assess factors that may impact human reliability in the operation of the system. The analysis is appropriate where reliable human performance is necessary for the success of the human-machine systems (Tarrents, 1980). 

The three significant OSD attributes are its sequential flow, its classification of activity type, and its ability to describe interactions between people and machines. In these respects, OSDs are similar to the Decision/Action charts, but more complex. The OSD can be seen as a static simulation of the system operations. This is also the reason why OSDs can become tedious to develop in the analysis of complex systems. 

Steady-state analysis techniques are based on acquiring vibration data when the machine or process system is operating at a fixed speed and specific operating parameters. For example, a variable-speed machine-train is evaluated at constant speed rather than over its speed range. 

Steady-state analysis can be compared to a still photograph of the vibration profile generated by a machine or process system. Snapshots of the vibration profile are acquired by the vibration analyzer and stored for analysis. While the snapshots can be used to evaluate the relative operating condition of simple machine-trains, they do not provide a true picture of the dynamics of either the machine or its vibration profile. 

Comparative analysis directly compares two or more data sets in order to detect changes in the operating condition of mechanical or process systems. This type of analysis is limited to the direct comparison of the time-domain or frequency-domain signature generated by a machine. The method does not determine the actual dynamics of the system. Typically, the following data are used for this purpose (1) baseline data, (2) known machine condition, or (3) industrial reference data. 

PCs all have one thing in common. They monitor the process variables, compare them to values known to be acceptable, and make appropriate corrections without operator intervention. The acceptable range of values can be determined by using melt flow analysis software and/or trial and error when the machine is first starting its production. Using the software approach, the acceptable process values are known before the mold or die is ever built. It should be noted that none of the PC solutions address the problem of the lack of skilled setup people. Most of the PC systems available today are rather complex and require skilled people to use them efficiently or at least start up the line. 

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