No abstract

Purpose. Development of a mathematical model of the air flow movement in a motorized filter respirator (hereinafter referred to as MFR), which allows ensuring the control of the fan parameters, taking into account external and internal influences on the duration of the protective action and favourable operating conditions. Methodology. To describe linear objects of the “input-output” type, it is convenient to use their transfer functions as mathematical models. In this case, to determine the mathematical description of the MFR operation, two tasks need to be solved. The first is related to finding the structure of the mathematical model, and the second involves determining the coefficients of the polynomials in the numerator and denominator of the transfer function that describes the motion of the air flow in the MFR. Findings. A mathematical model of airflow in a MFR has been developed in the form of a transfer function of the third order; it can be used to develop a pressure control system for the air in the under-mask space in accordance with the user’s work mode in order ensure comfortable working conditions. The presented mathematical model of airflow in the MFR differs from the existing approaches by taking into account the influence of the following external and internal parameters of the system on the performance indicators: the user’s work mode, atmospheric pressure, filter resistance, pressure drop in air ducts with the effect of air accumulation in the under-mask space based on the “capacity-resistance” principle. Numerical coefficients of the mathematical model of airflow in the air duct of the MFR have been determined, which allow adjusting the number of fan rotations according to the time of operation, the increase in resistance on the filters, and the operating mode. Originality. A correlation has been established between the external and internal parameters of the MFR: atmospheric pressure, pressure drop in the air duct, filter resistance, and the user’s work mode with the effect of air accumulation in the sub-mask space reflected according to the “capacity-resistance” principle. Practical value. The parameters of the mathematical model have been determined, which can be used when developing a control system for the airflow movement in the MFR: changes in air flow rate in accordance with different conditions of physical exertion of the user when performing professional activities.

Working conditions, in terms of hygiene, harmful impurities in the air of the working area, often do not meet regulatory requirements. In such cases, motorized filter respirators are used to protect respiratory organs, which require the development of an appropriate system for managing operational indicators for effective operation. The purpose of the article was to improve the control system of a motorized filter respirator to increase protective efficiency, due to the development of a new parametric scheme of the control object, taking into account the functional relationships between the operating mode, air flow, filter resistance and the term of protective action. To create an appropriate control system, a structural-parametric synthesis of operational indicators management was applied, based on the relationships between the main variables (outgoing regulated variables, controlling influences and disturbances). A new working diagram of the control object with selected design elements of the blower has been developed, the main difference of which is the use of the “Arduino Uno R3” board, the “LCD Keypad Shield” module with a two-line display for controlling the air flow modes, in accordance with the change of the filter resistance taking into account the accumulation dust deposit based on the assumption that the transfer function can be represented by an aperiodic link of the 1st order with sufficient accuracy for practice. To work out the operating modes and determine the duration of the protective effect, a software model of the operation of the motorized filter respirator was created, which made it possible to evaluate the influence of the dust concentration on the change in air flow through the filter elements, taking into account the accumulation of dust sediment on the protective effectiveness. Recommendations have been developed to ensure the effective functioning of the protective device in accordance with the requirements under the most unfavorable conditions. The practical value of the work lies in the fact that the modes of movement of the air flow are determined, in accordance with the speed of rotation of the fan blade from the width of the PWM pulses, which depend on the resistance of the filter, the accumulation of dust deposits based on the transfer function