Apparatus for automatically controlling the flow rate of a fluid flowing along a duct and refrigeration or cooling system comprising the aforesaid apparatus

An apparatus for automatically controlling the flow rate of a fluid flowing along a duct, comprising:

• a valve element adapted to be interposed along a section of said duct and comprising an obturator configured to vary its position between a first end position of complete interception of said fluid and a second end position of complete opening;
• a direct current servo-motor operatively connected to said obturator to allow positioning said obturator between said first end position and said second end position;
• an electronic control unit operatively connected to said servo-motor and configured to generate an output signal to be provided to said servo-motor, said output signal being adapted for positioning said obturator in a specific first position;
• an electronic interface module operatively connected to said electronic control unit;
• and
• an electrical input connector configured to be connected with external electronic control means adapted to generate an input signal for stepper motors intended to move obturators of valve elements for controlling the flow of a fluid in a duct, wherein said input signal is adapted for positioning the obturators of the valve elements in a specific second position, said electronic interface module being configured to convert said input signal into an intermediate signal placed as input to said electronic control unit, said electronic control unit being configured to convert said intermediate signal into said output signal so that said specific first position corresponds to said specific second position,
• wherein said electronic interface module is configured to receive as input and convert into said intermediate signal two electrical current signals for driving a first phase and a second phase of bipolar stepper motors, said electrical current signals being of the Half-step, Full-step or Microstepping type,
• wherein said electronic interface module, to detect from said input signal the number of movement steps to be performed and the direction of execution of said movement to arrange said obturator in said specific second position, is configured to:
• set a step number variable to 0;
• generate, for said electrical current signal of each of said first phase and second phase, a square wave on two levels, a low level and a high level, the rising edges and the falling edges of said square waves being determined by the transient of each of said electrical current signals through the null value by a negative value and a positive value respectively;
• detect over time, for each predefined sampling period T, the level of said square waves, where said sampling period T is selected so that a sampling frequency 1/T is equal to or four-fold higher than the fundamental frequency of said electrical current signals;
• and for each sampling instant t, said electronic interface module is configured to:
• detect the value of the step based on the combination of the levels of said square waves at the sampling instant t and at the immediately preceding sampling instant t-T, the step is detected as x when the first phase is a high level H and the second phase is a low level L, the step is detected as x+1 when the first phase is the high level H and the second phase is the high level H, the step is detected as x+2 when the first phase is the low level L and the second phase is the high level H, and the step is detected as x+3 when the first phase is the low level L and the second phase is the low level L, where x is a variable whose value is selected from a set of integers Z,
• calculate a subtraction result of subtracting the step value at instant t with the step value at the immediately preceding instant t−T, wherein said subtraction result is set as as −1 when said substraction result is a positive value with an absolute value greater than 1 and said subtraction result is set as +1 when said result is a negative value with an absolute value greater than 1;
• set a required movement direction, wherein said required movement direction is set as a first movement direction selected from the two movement directions when said subtraction result is a positive number and said required movement direction is set as a second movement direction of the two movement directions when said subtraction result is a negative number;
• and
• increase said step number variable by one when the substraction result is a value other than 0.