Methods Time Measurement Research Articles

Work methods measurement—a comparison between robot and human task performance

SUMMARY The industrial robot, already an accepted element in modern manufacturing, when coupled with sensors and controlled by a computer, is better modelled as an operator than as a machine. In this paper the basic characteristics of sensor controlled robots are defined : workspace, actuation, positioning, orientation, sensing and decision making. Actual values of these characteristics are given for the Stanford Arm running under the WAVE system. In order to compare a robot to a human operator we consider each of the task elements defined in an established methodology for human work analysis, method time measurement (MTM). We translate each of these work elements into robot program statements. From this comparison we find that a robot can be modelled as an operator but that a different set of work elements is appropriate. We develop a new methodology, which we call RTM (robot time and motion) and describe an actual robot assembly operation. The same assembly task is described using MTM for a human operator as a comparison. RTM differs from MTM in that element times are based on physical parameters of the robot, maximum torque-, resolution, sensors, etc., leading to an exact method of predicting task times, unlike MTM which must take human variability into account in providing estimates of work element times. RTM provides a method of comparing robots by comparing work element times for each robot. A translation table from MTM into RTM is also developed, allowing robot performance to be compared to human operator performance for existing tasks.

Long-range motor performance changes in levodopa-treated patients with Parkinson's disease.

A precise measurement of motor function, Methods-Time Measurement, was used to analyze motor performance in patients with Parkinson9s disease receiving levodopa therapy. The data indicate an initial improvement, in all motions of the upper extremity, that reaches a maximum and then slowly declines over a period of years. Thus it appears that Parkinson9s disease continues to advance despite treatment with L-dopa. It is unlikely that a biochemical disorder is the basis of the illness. More likely a basic neuropathologic disorder is responsible for inducing dopamine deficiency, so that arresting the condition will depend on identification and correction of this more fundamental defect.

A HUMAN FACTORS APPROACH FOR SELECTING PROSPECTIVE PRODUCTION WORKERS AND PREDICTING THEIR FUTURE PERFORMANCE

SUMMARY A set of personnel selection tests was developed to give employers a guide for selecting prospective production workers for bench type assembly operations. The resulting methodology incorporated a battery of eight personnel selection tests which were administered to 29 production workers for measuring the individual's sensory, motor and psychomotor abilities believed pertinent to such tasks. Using the test measurements as independent variables, time to perform elemental motions of the Methods-Time Measurement predetermined time system was predicted. Elemental motion performance predictions were then combined to provide a prediction of total job performance for a prospective employee. Such an approach is unique in that the methodology predicts performance on elemental motions. Thus, the prediction of performance on any job could be attempted if the basic elements of the job were known.

Precision in movements.

Under some circumstances the channel capacity of the human motor system has boon shown to be constant. Relationships based on information theory have been developed between the time for movement and the amplitude and tolerance of the movement. In the present experiment movements were made in one plane only, and it was hoped to test the general applicability of the relationships. The apparatus provided a pointer, which was swivelled by the subject through a vertical plane between two separated targets The experimental results have shown a significant relationship between the time for one rotary movement and a binary logarithmic index which related amplitude with target width. The time taken was affected by the inertia of the rotary system. There was variation between the eight subjects in the time taken. A comparison was made to see whether an index from the movement amplitude and target width was simply related to the values for the test determined from three Predetermined Motion Time Systems. Satisfactory times were not evolved from two of the throe Predetermined Motion Time Systems, but one system, Methods-Time Measurement, gave reasonable data.

A PROBABILISTIC APPROACH TO THE DEVELOPMENT OF A SIMPLIFIED WORK MEASUREMENT SYSTEM

SUMMARY A probabilistic approach to the development of a simplified work measurement system is presented. As a result of this approach, expected time values and accompanying variances can be calculated for each element under investigation. General Purpose Date (GPD) and Master Standard Data (MSD), standard data systems which are simplifications of a more detailed predetermined time system, Methods-Time Measurement (MTM), were used to illustrate the applicability of this method. In order to pursue this probabilistic approach, the various combinations of MTM elements which satisfy each investigated GPD and MSD element have been enumerated. The probability of occurrence of each of these possible combinations has been developed using historical data. Given the time value and the probability of occurrence for each possible combination, the expected time value and accompanying variances were generated for the “simplified” element.

A comparison between work factor and methods time measurement systems in work measurement for short cycles

A comparison between work factor and methods time measurement systems in work measurement for short cycles

Methods-Time Measurement Analysis of Some Milk Plant Cleaning Operations

Methods-Time Measurement Analysis of Some Milk Plant Cleaning Operations