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4.3 Then the students should solve the problems and tasks (should determine
basic parameters of the system “Human – Machine”) according to the variant given
by teacher. They may use references [1, 2] and theoretical data from basic theory.
Task 3.1. Find the time required for a driller to assess the situation during
the drilling process for the following: force and torque applied to the bit, pressure
and flowrate of the drilling fluid. The average duration of visual fixations for
assessing data of each parameter is 0,31 s, and the average length of searching eye
movements– 0,025 sec.
Task 3.2. At the initial stage of drill string sticking during the drilling the
pressure increased (indicated by the gauge indicators) and the load on the drill line
reduced (indicated by hydraulic weight indicator - HWI). Determine the time of
signs of danger of drill string sticking prior to operations aimed to its prevention
(stopping of rotor table and turning on the drawworks) for the following
conditions: time required to assess the gauge indicators and indicator of HWI –
150 ms and 160 ms respectively, time required to transfer the view from one unit
to the other– 0,25 s, the duration of involuntary distraction of the driller – 140 ms,
time required to perform actions related to stopping the rotor and starting
drawworks – 100 ms and 110 ms respectively.
Task 3.3. Find the required duration of free time in work of operator during
8-hour work shift, if the degree of harmfulness for the environment factor is 50
points, and the duration of its action during working hours is 7,2 hours.
Task 3.4. Process control system includes an operator and three technical
devices with chain (serial) connection, which have the following characteristics:
the reliability of each technical unit 0,99; 0,97; 1,0 respectively; the error of each
working unit 2; 5; 0. The random error in the operator’s action is 3. The reliability
of cycle implementation should be at least 0,95, and the random root mean square

error must not exceed 9 points.
Define:
a) what requirements must follow (satisfy) an operator for a reliable
operation?
b) will the error of conduction cycle regulation be provided under these
specified circumstances?
Task 3.5. Find the spatial position of the optimal zone for installation of an
indicator (control panel) and also find the minimal distance from the panel to the
floor level that would ensure the control of machine without tilting the worker to
panel for the following conditions: distance from bench to worker L, cm (initial
data is shown in Table 3.1), the angular size of indication zone is , (initial data is
shown in Table 3.1), height of worker’s eyes h eyes , cm (initial data is shown in
Table 3.1), height of the shoulders of the worker h , cm (initial data is shown in
sh
Table 3.1), the length of the hand of worker L hand , cm (initial data is shown in
Table 3.1). The average deviation of the height level of the shoulder placement and
length of worker’s hand are respectively  =5.5 cm and  hand =3.5 cm, the
sh
coefficient of variation k=1,65. The working areas of the machine are shown in
Figure 3.1.

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