KR100942128B1 - Method for Calculating Revolution Per Unit time using High Speed Counter - Google Patents

Abstract

According to the present invention, when a revolution per unit time (RPU) is calculated using a high speed counter, the revolution per unit time is accurately reflected by a change in the number of input pulses, so that the rotation time per unit time is different. Make sure you can count numbers correctly. To this end, the interrupt generation cycle is subdivided according to the RPU unit time and display value update cycle set by the user, and the number of pulses inputted in each interrupt generation cycle is stored and then used for calculating the number of revolutions per unit time. Accordingly, even if a difference occurs in the pulse input speed, an error in calculating the number of revolutions per unit time can be improved by minimizing the effect.

High speed counter, revolution per unit time (RPU), interrupt generation cycle, update cycle

Description

Method for Calculating Revolution Per Unit time using High Speed Counter}

The present invention relates to a method for calculating the number of revolutions per unit time using a high speed counter, in particular, when calculating the number of revolutions per unit time (RPU) using a high speed counter accurately reflects the change in the number of input pulses RPU unit time and display Even when the value update period is different, the number of revolutions per unit time can be calculated accurately.

Revolution Per Unit time (RPU) information is used across many sectors of the industry. If the number of pulses generated per one rotation is known when the pulses are generated according to the rotation of the predetermined rotor, the number of rotations per unit time can be calculated by counting the number of pulses using a high speed counter.

As a specific example, a programmable logic controller (PLC) provides a high speed counter function in the form of a built-in base unit or an expansion module for counting a high speed pulse train.

Referring to FIG. 1, in order to use the RPM measurement function per unit time of the PLC, a PC may be generally installed using a personal computer (PC) or a human machine interface (HMI) device 11. 12) Basic information such as RPU unit time, number of pulses per revolution, and period for displaying the calculation result (hereinafter referred to as display value update cycle) are set.

The high speed pulse input circuit 12-1 converts a high speed pulse string input from the encoder 13 to a CMOS level and transmits the same to the microprocessor 12-2 (MPU), and the microprocessor 12-2 receives the high speed pulse. The pulse train inputted through the input circuit 12-1 is counted, and when the display value update cycle is reached, the number of revolutions per unit time is calculated based on the relationship between the number of input pulses, the number of pulses per revolution, and the RPU unit time. It stores in the buffer 12-3. Then, the personal computer or HMI device 11 reads the value stored in the output buffer 12-3 and displays it on the screen to inform the user of the current rotation speed per unit time.

Referring to Figure 2 will be described a conventional method for calculating the number of revolutions per unit time.

When the high speed counter function of the PLC is activated, the microprocessor 12-2 starts receiving the high speed pulse by the internal firmware and counts the number of pulses input until the high speed counter stop command is received (S21).

At this time, if the rotational speed measurement function per unit time is activated by the personal computer or the HMI device 11, the microprocessor 12-2 starts the internal timer interrupt so that an interrupt occurs every display value update period (S22).

On the other hand, the microprocessor 12-2 counts the pulse string transmitted from the high speed pulse input circuit 12-1, and when the display timer update cycle occurs and the internal timer interrupt occurs, the microprocessor 12-2 proceeds to the interrupt service routine (S23).

The interrupt service routine first calculates the number of pulses input in this display value update period by subtracting the initial value of the RPU interval from the accumulated total number of input pulses (S24), and calculates the revolutions per unit time as shown in Equation 1 below. (S26).

Now, the number of revolutions per unit time calculated in step S25 is stored in the output buffer 12-3 for reading by the personal computer or HMI device 11 (S26). The microprocessor 12-2 ends the interrupt service routine after storing the current high speed counter value as the initial value of the RPU interval in order to calculate the number of revolutions per unit time.

As can be seen from Equation 1, conventionally, a method of estimating the total number of input pulses during an RPU unit time by multiplying or dividing the number of pulses input during a display value update period by a proportional relationship with the RPU unit time is used. That is, if the display value update period is 1 second and the RPU unit time is 3 seconds as shown in the example shown in FIG. 3A, the number of pulses in the remaining sections is estimated using the number of pulses input during the current display value update period 1 second. This causes the following problems.

1) Since the number of pulses for the entire section of the RPU unit time is predicted using only the number of pulses input during one display value update period, even if the pulse input speed during a specific display value update period changes slightly, the number of revolutions per unit time is calculated. The fluctuation range of becomes large. This phenomenon becomes larger as the difference between the display value update period and the RPU unit time increases.

As an example, assuming that the number of pulses per revolution is 2, the RPU unit time is 3 seconds, and the display value update period is 1 second, as shown in FIG. Also, the error is enlarged in the result value of the revolutions per unit time.

2) Since the number of pulses input during the display value update cycle is multiplied or divided by the ratio of the display value update cycle and the RPU unit time, a device that measures the number of revolutions per unit time, such as PLC, calculates floating point. If this is impossible, an error occurs in the calculation result of the revolutions per unit time.

For example, suppose that the display value update cycle is 1.5 seconds, the RPU unit time is 10 seconds, the number of pulses per revolution is 2, and the number of pulses is rotated once per second. The calculation of revolutions per hour shall be '3.333'. However, when floating point processing is not possible, it becomes '3', which causes an error in the calculation result. This problem becomes larger as the pulse input speed is higher.

Accordingly, the present invention has been made to solve the above problems, by subdividing the interrupt generation cycle according to the RPU unit time and the display value update period to store the number of input pulses input to each section, the number of rotations per unit time calculation It is an object of the present invention to provide a method for calculating the number of revolutions per unit time using a high speed counter that can reduce the error.

In order to achieve the above object, the method for calculating the number of revolutions per unit time using the high speed counter according to the present invention, the count of the input pulse using the high speed counter is started, the user the RPU unit time, display value update cycle, once Setting the number of pulses per turn; The interrupt generation period is set to the largest value among the values having an integer multiple of both the RPU unit time and the display value update period, and an incremental variable equal to the number n divided by the RPU unit time by the interrupt generation period is set. Setting up; And an interrupt generating step of generating an interrupt when the timer interrupt is activated to generate the interrupt, thereby performing an interrupt service routine consisting of steps a) to d) below.

The interrupt service routine, a) calculates the number of pulses input during this interrupt generation cycle and stores them sequentially in each of the set incremental variables, starting from the interrupt occurrence of the 'n + 1' th time, and circulating the values stored in each incremental variable. Storing the value in which the storage order is the fastest; b) monitoring the number of interrupt occurrences and determining that the display value update cycle is completed each time the interrupt occurs by the display value update cycle / interrupt generation cycle; c) calculating the number of revolutions per unit time using the values stored in each incremental variable when the display value update period is completed as a result of the determination; And d) terminating the interrupt service routine and returning to the interrupt generation step.

The interrupt generating step includes storing the high speed counter value in a variable 'count_ini' first, and the number of pulses input during the current interrupt generation period is the variable 'count_ini' at the high speed counter value at the time of the interrupt occurrence. And calculate by subtracting the value.

The number of revolutions per unit time is expressed by the equation when the number of interrupt occurrences is less than n

It can be configured to calculate according to.

Here, RPU is the number of revolutions per unit time, T1 is the interrupt generation cycle, and N1 is the number of interrupt occurrences.

The number of revolutions per unit time is expressed as the interrupt occurrence frequency when n or more

It can be configured to calculate according to.

According to the present invention, even if the display value update period and the RPU unit time are different from each other, and there is a difference in the number of pulses input in each display value update period, it is possible to minimize the effect of such a difference on the calculation of revolutions per unit time. . Accordingly, it is possible to reduce the error that may occur when calculating the number of revolutions per unit time.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Referring to FIG. 4, first, an input pulse count is started using a high speed counter, and a user who wants to use the rotational speed measurement function per unit time includes an RPU unit time, a display value update cycle, and a rotational speed per unit time, such as a pulse number per revolution. The basic information necessary to calculate is set (S41). In the example of PELC shown in FIG. 1, PSI is inputted through a personal computer or an HMI device.

Now, using the information set in step S41, an interrupt generation cycle and a variable for storing the number of pulses input during each interrupt generation cycle (hereinafter, referred to as "incremental variables") will be set. S42).

The interrupt generation period is set to the largest value among the integer multiples of both the RPU unit time and the display value update period.

In other words, if the RPU unit time and the display value update cycle are integer multiples of each other, the interrupt generation cycle becomes the update cycle. For example, if the RPU unit time is 3 seconds and the update cycle is 1 second, an interrupt is generated every 1 second. If the RPU unit time and the update period are not in integer multiples, the interrupt generation cycle is the largest value that has an integer multiple of both values at the same time. For example, if the RPU unit time is 4 seconds and the update period is 1.5 seconds, the interrupt generation cycle is 0.5 seconds, which is the largest value among the integer multiples of both values.

In addition, the number of incremental variables is the number n divided by the interrupt generation period of the RPU unit time, and each incremental variable is initialized.

5 shows the relationship between the interrupt generation cycle, the incremental variable, the RPU unit time, and the display value update cycle. If the RPU unit time is 4 seconds and the update period is 1.5 seconds as described above, 0.5 seconds is the interrupt generation period, and a total of eight incremental variables (delta [0] to delta [7]) are set.

Then, temporary variables i and u are set (S43). The variable i is for indicating the total number of times the interrupt has occurred, the variable u is for indicating that each display value update cycle is completed, and all initial values are set to zero.

Now, the process of measuring the interrupt occurrence period by starting the timer interrupt is performed (S44). In step S44, the current value of the high speed counter is first stored in the variable 'count_ini'. This value is later used to check the number of pulses entered in each interrupt generation cycle.

When the measured value of the timer reaches the interrupt generation cycle, an interrupt is generated and branches to the interrupt service routine (S45). The process below step S46 is a process performed in the interrupt service routine. When the interrupt service routine ends, the process returns to step S44 again to start a timer interrupt to repeat the process of measuring the interrupt occurrence cycle.

The interrupt service routine will now be described.

First, the variable i is compared with the value n (S46). That is, since n is the number of incremental variables and variable i represents the number of interrupts generated, it is a process of determining whether interrupts are generated by the number of incremental variables.

As a result of the determination in step S46, if the value of the variable i is less than the value of n, the number of pulses input during this interrupt generation period is stored in the incremental variable delta [i] of the current order (S47-1). That is, until the total interrupt occurrence number is equal to n value, the number of pulses input during this interrupt generation cycle is stored in each incremental variable sequentially.

At this time, the number of pulses input during this interrupt generation cycle can be confirmed by subtracting the variable count_ini value stored in step S44 from the value of the high speed counter when the interrupt occurred in step S45.

However, as a result of the determination in step S46, if the value of the variable i is equal to or greater than n, the value stored in each incremental variable is circulated so that the number of pulses input during this interrupt generation cycle is replaced by the value having the fastest storage order. (S47-2). That is, each incremental variable delta [0] to delta [n-2] is cyclically replaced with a value of delta [1] to delta [n-1], respectively, and the interrupt occurrence period is incremented to the incremental variable delta [n-1]. The number of pulses entered during is stored. This means that if the number of interrupt occurrences exceeds n, the number of pulses entered in each of the most recent n interrupt cycles is stored in the increment variable.

Now check whether the update cycle is completed (S48).

Step S48 can be confirmed through the variable u value. When the variable u value is "display value update cycle / interrupt generation cycle", the display value update cycle can be determined to be completed according to the contents set in step S42.

As a result of the determination in step S48, when the display value update period is not completed, the variable u value is increased by one (S49-1).

However, when the display value update cycle is completed as a result of the determination in step S48, the number of revolutions per unit time is calculated using each incremental variable (S49-2), and the variable u value is determined to determine the display value update cycle again. Initialize (S49-3).

After the interrupt processing is completed, the value of the variable i is increased by one, and then all interrupt service routines are terminated, and the process returns to step S44 again (S49-4).

On the other hand, the method for calculating the number of revolutions per unit time in step S49-2 can be configured as follows according to the total number of interrupts generated.

1) If the total number of interrupts is less than n, calculate the number of revolutions per unit time according to Equation 2 below.

Here, RPU is the number of revolutions per unit time, T1 is the interrupt generation cycle, and N1 is the number of interrupt occurrences.

2) If the total number of interrupts is n or more, calculate the number of revolutions per unit time according to Equation 3 below.

6 shows an example in which the display value update period is 1 second and the RPU unit time is 3 seconds.

In this case, conventionally, the number of pulses to be input for 3 seconds was estimated using the number of pulses input every 1 second, and then the number of revolutions per unit time (RPU) was calculated through this. The number of revolutions per unit time (RPU) is calculated using the number of input pulses, the number of input pulses accumulated for two seconds at a second time point, and the number of input pulses accumulated for three seconds after a third time.

This makes it possible to calculate the revolutions per unit time using the actual number of pulses input during the corresponding unit time of the RPU. It is possible to improve the calculation error.

In the example of FIG. 6A, since the interrupt generation period and the display value update period are the same as 1 second, the expression is indicated as an 'update period' for the sake of understanding.

In addition, FIG. 6B shows the state of each incremental variable as the display value update period is increased, and each incremental variable value is circulated after the fourth display value update period.

FIG. 7 illustrates a result of calculating rotation speed per unit time under the same conditions as the example of FIG. 3B.

When a change in the number of input pulses as shown in the N second interval occurs, the rotation value per unit time of '158' is calculated when using the conventional method, but under the same conditions when using the improved method according to the present invention. It is calculated as '154'.

That is, using the method according to the present invention it can be seen that the number of revolutions per unit time than the conventional method is calculated.

Each embodiment described above is intended to help the understanding of the present invention, the present invention is not limited to the above embodiments and can be variously modified and implemented by those skilled in the art without departing from the technical spirit of the present invention. Of course.

1 is an example of a PLC system having a high-speed timer function,

2 is an example of a process of calculating the number of revolutions per unit time in the related art;

3 is a schematic example of a process of calculating the number of revolutions per unit time in a conventional manner;

Figure 4 is an embodiment of a method for calculating the number of revolutions per unit time using a high speed counter according to the present invention,

5 is an overview for explaining an interrupt generation period and an incremental variable;

6 and 7 are schematic examples of the process of calculating the revolutions per unit time in the manner according to the invention.

Claims (4)

Counting the input pulses using the high speed counter, and the user setting the RPU unit time, display value update period, and number of pulses per revolution; The interrupt generation period is set to the largest value among the values having an integer multiple of both the RPU unit time and the display value update period, and an incremental variable equal to the number n divided by the RPU unit time by the interrupt generation period is set. Setting up; An interrupt generation step of activating a timer interrupt to generate an interrupt when the interrupt generation cycle is reached so that an interrupt service routine consisting of steps a) to d) is performed; a) Calculate the number of pulses input during this interrupt generation cycle and store them sequentially in each set increment variable, but from the 'n + 1' interrupt, the value stored in each increment variable is circulated to obtain the fastest value. Alternatively storing; b) monitoring the number of interrupt occurrences and determining that the display value update cycle is completed each time the interrupt occurs by the display value update cycle / interrupt generation cycle; c) calculating the number of revolutions per unit time using the values stored in each incremental variable when the display value update period is completed as a result of the determination; And d) A method for calculating the number of revolutions per unit time using a high speed counter comprising the step of ending an interrupt service routine and returning to the interrupt generation step. The method of claim 1, The interrupt generation step includes first storing the fast counter value in a variable 'count_ini', The number of pulses input during the interrupt generation period is calculated by subtracting the variable 'count_ini' value from the high speed counter value at the time when the interrupt occurs. The method of claim 1, When the frequency of occurrence of the interruption is less than n, the number of revolutions per unit time is calculated.

(RPU: revolutions per unit time, T1: interrupt occurrence cycle, N1: interrupt occurrence count) Method for calculating the number of revolutions per unit time using a high speed counter, characterized in that configured to calculate according to. The method of claim 1, When the number of interrupt occurrences is more than n, the number of revolutions per unit time

(RPU: revolutions per unit time) Method for calculating the number of revolutions per unit time using a high speed counter, characterized in that configured to calculate according to.

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