JPH06101955B2 - Servo speed signal generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a speed signal generator for a servo system.

[Description of Prior Art] Conventionally, a special speed detecting device for obtaining a speed signal,
For example, a speed signal is formed based on a detection signal of a pulse encoder instead of providing a tacho generator, a resistance voltage dividing type speed detection device, or the like. In this method, for example, the speed value is known by counting the number of pulses input within a predetermined time, or by measuring the time during which a predetermined pulse occurs and obtaining the reciprocal of this. Generally speaking, it can be said that the velocity signal can be obtained by appropriately correlating the detection pulse with the reference time.

By the way, pulse encoders are manufactured by various companies and have various characteristics. That is, even if the rotary encoder is taken as an example,
The characteristics such as whether or not a pulse is generated by moving 10 mm will differ depending on the manufacturer and the standard.

On the other hand, in the case of constructing a servo system using the encoder, it is free to design how much detection voltage should be obtained with the movement of the encoder provided in relation to the motor or the moving object. . For example, one would like to obtain a voltage of 3 volts with the rotary encoder rotating 10 times per minute.

Therefore, when a servo system is constructed using an encoder and a speed signal is to be generated from the output pulse of this encoder, the circuit configuration must take into consideration the characteristics of the encoder and the voltage characteristics to be output to the servo amplifier. I had to do it. That is, each time the encoder type is different,
The circuit configuration has to be changed every time the design value of the output voltage is different, which requires a lot of labor for the circuit configuration and leads to high cost because a single product is provided.

[Object of the Invention] The present invention solves the above problems and is applicable to any case regardless of the design characteristic value of the pulse encoder and the characteristic value such as the voltage characteristic value to be output to the servo amplifier. An object of the present invention is to provide a low-speed velocity signal generator which can be applied to all the changes in the characteristic values without the need to configure a circuit for each change in the characteristic values by obtaining the signal generator.

[Configuration of the Invention] As shown in FIG. 1, the present invention for achieving the above object is provided with a pulse encoder in association with a motor or an object to be moved, converts a detection pulse of the encoder into a speed signal, and converts it into a voltage signal. A constant value setting means 1 for setting a characteristic value in the design of the encoder, a voltage characteristic value to be output to the servo amplifier, etc. in a servo system speed signal generating device which is converted into a value and fed back to the servo amplifier. And a reference magnification calculation means 5 for uniformizing the calculation processing in the output value calculation means 3 later based on the characteristic value set by the constant setting means 1, and the detection pulse of the encoder within the sampling time. The input pulse counting means 7 for counting the number of pulses input during this period, and the speed result by appropriately correlating the reference time with the counting result of the input pulse counting means 7. An output value calculation means 3 for forming a dimension and a normal speed signal by multiplying the speed dimension by the reference magnification calculated by the reference magnification calculation means; and an output signal of the output value calculation means 3 It is a speed signal generation device for a servo system, characterized in that it has a digital-analog conversion means 9 for converting this into an analog voltage.

In FIG. 1, the constant setting means 1 is composed of, for example, a DIP switch or the like, and each characteristic may be input by this. The output value calculating means 3 is the input pulse counting means 7
The input pulse is obtained at a predetermined timing from and the calculation for uniform speed signal generation according to the circuit configuration is performed, and the calculation result is multiplied by the reference magnification determined by the above characteristic, so that the characteristic value may be changed even if the characteristic value changes. A single calculation is sufficient, and it can respond to any characteristic value.

[Description of Embodiments] A preferred embodiment of the present invention will be described with reference to FIG.

FIG. 2 is a block diagram of a servo system showing the arrangement of the speed signal generator.

The servo system includes a main controller 11 of the numerical controller and the main controller 11
A pulse distribution unit 13 that outputs a movement command until the count number of the internal counter reaches zero,
It has a servo amplifier 15 which receives a movement command from the pulse distributor and applies a drive voltage to the motor M. A rotary encoder E is provided in the motor M, and a speed signal generator 17 is provided between the encoder E and the servo amplifier. The detection pulse of the encoder E is returned to the pulse distributor 13 and is also input to the speed signal generation device to be formed into an appropriate voltage signal there, and compared with a command voltage to the servo amplifier 15.

FIG. 3 shows a detailed block diagram of the speed signal generator 17.

The speed signal generator 17 includes a central processing unit (CPU) 19 and a ROM 2
1 has a RAM 23, two counters 25, 27 and two D / A converters 29, 3 via a system bus 25 with these
1, the LED display unit 33, and the DIP switch 35 are connected. Two encoders can be connected, and two encoders E1 and E2 are provided with two direction discriminating circuits 37 and 39, respectively. The outputs of these direction discriminating circuits correspond to the two counters 25 and 27, respectively. Connected to enter. The characteristics of encoders E1 and E2 are the same.

On the other hand, the outputs of the two D / A converters 29 and 31 are received by the two buffer amplifiers 41 and 43, respectively, and their outputs are 2
Two servo amplifiers 45 and 47 are connected to output. The direction discriminating circuit, the counter, the D / A converter, and the buffer amplifier are each provided with two motors. For a machine tool having two motors, for example, an X-axis drive motor and a Y-axis drive motor, speed signals of both drive motors are provided. Is used to form the speed signal of the X-axis drive motor, and that of the reference numeral 2 is used to form the speed signal of the Y-axis drive motor. The LED display unit 33 is for processing an alarm described later, and obtains an alarm signal and displays an appropriate alarm.

The DIP switch 35 is for inputting a characteristic value. The characteristic of the encoder E1 (or E2), that is, the number of pulses generated per rotation, and the voltage characteristic to be output to the servo amplifier, that is, 1000 rpm, are used. It allows you to enter what should be given 3 volts. And CPU19
Calculates the reference magnification K for standardizing the output value calculation method described later, based on these set values.

That is, if the output value of the encoder is processed by the calculation method described below and the result is output to the D / A converter, the reference magnification is 1 when the predetermined output voltage can be obtained. The reference magnification K is set to 2 when only half the pulse is generated or when the servo amplifier requires a voltage twice as high.

In order to know the direction of the pulse output from the encoder E1, the direction discrimination circuit 37 is divided into A and B2 phases with different phases.
Entered in. The direction discriminating circuit 37 obtains the two phases A and B and discriminates the direction to generate a signal in the forward direction (CW) and a signal in the reverse direction (CCW). The counter 25 can know the amount and direction by counting in the forward direction and counting in the reverse direction.

Therefore, the CPU 19 sets a predetermined sampling time, for example 0.4.
The count value of the counter 25 is accessed every millisecond to form a speed dimension (movement amount / time). in this case,
The number of counts / sampling time. However, even if this value is given to the D / A converter 29 as it is, the buffer amplifier 41 cannot output an appropriate value (for example, 3 volts per 1000 revolutions per minute of the encoder E1).
Here, the CPU 19 multiplies the dimension of the speed by a reference magnification K determined from the set value of the dip switch 35, outputs the product to the D / A converter 29, and outputs the voltage output from the buffer amplifier 41. Proper value (3V)
And

The above processing is shown below as a specific example.

It is assumed that the number of output pulses of the encoder is 2000 pulses per rotation. In addition, suppose that you want to obtain a voltage of 3 V if you rotate 1000 rpm. It is assumed that the encoder output is input via a quadrupling circuit and has 8000 pulses per rotation.

The minimum resolution of the D / A converter is 4.88 millivolts. That is, the digital value must be about 615 to obtain 3 volts.

On the other hand, the count number P of the output pulses from the encoder rotating 1000 revolutions per minute is about 53 pulses when the sampling time (reference time) is 0.4 milliseconds.

Therefore, if the number of pulses detected within the sampling time shown in is multiplied by about 12, the output voltage of 3 V shown by can be obtained.

The arithmetic expression for obtaining the reference magnification K in this example is: (required number of writes) / (number of detections) K = (V / v) / (N × P ₀ × t × n / 60) (I) In addition, V is a voltage value [volt] to be output to the servo amplifier when the encoder has a predetermined rotation speed N [γpm] (1000 in the above example). v is the resolution of the D / A converter, that is, the output voltage [volt] when written as "1". P ₀ is encoder 1
Number of output pulses per revolution. t is the sampling time [seconds]. n is a coefficient of the multiplier circuit. In the above example, K = 1
It becomes 1.53 (about 12).

Referring to the above formula (I), in the formula, only V, N, and P ₀ are numerical values to be determined externally, and v, t, and n are all circuit constants. Therefore, V, N, P ₀ , that is, the first
If the dip switch 35 is used to specify the number of pulses P ₀ generated per encoder rotation and secondly the condition that V Volt is to be generated when the encoder rotates N rotations per minute, the reference magnification K is automatically set. Will be required. It should be noted that such a reference magnification can be applied to any speed calculation method. That is, for example, even when a time pulse (clock) until a predetermined pulse is generated is measured, this is divided by a predetermined number of pulses, and a speed value is obtained from the reciprocal number, a similar reference magnification exists. It will be. In addition, the method of determining the characteristic value is not limited to the method of determining whether the voltage of the directional bolt per predetermined number of rotations of the encoder should be output as in the above equation, but if the moving target actually moves, Of course, it is possible to determine how much voltage should be generated.

Furthermore, a condition for generating an alarm on the alarm display 33 shown in FIG. 3 is that the count value of the counter 25 or the counter 2 is abnormally large or abnormally small. For example, if the signal from the encoder E1 or E2 is no longer input due to a wire break, the count number will be zero, but this is a situation that normally cannot occur, so this is judged as a wire break and an alarm is displayed. You can do it.

FIG. 4 shows a flowchart of the processing performed by the CPU 19.

The process starts at step 401 and is initialized at step 403. In step 405, the setting switch is read, that is, the first and second conditions are read as constants.
In step 407, the magnification K is obtained from these constants.

In step 409, the count of counter 1 (counter 25) is read. The counter is cleared immediately after this reading operation, and then starts counting the number of pulses from the direction discriminating circuit 37. In step 411, the value read from the counter 1 is divided by the sampling time t to make the dimension of the speed, and this value is multiplied by the reference magnification K to obtain the product thereof in step 41.
Output to D / A1 (D / A converter 29) at 7. If this value seems to be an abnormal value at this point, it can be judged in step 413 and an alarm process can be performed in step 415. Of course, the alarm processing can be performed not only by displaying but also by stopping the machine.

The processing from step 419 to step 425 is processing relating to the other encoder and the servo amplifier corresponding thereto, and is similar to the processing from step 409 to step 417. Step 427 adjusts the sampling time.

[Effects of the Invention] As is apparent from the above description, according to the present invention, in any case, regardless of the design characteristic value of the pulse encoder and the characteristic value such as the voltage characteristic value to be output to the servo amplifier. It is possible to provide a low-cost speed signal generator that can be applied to all the changes in the characteristic values without having to configure a circuit for each change in the characteristic values. it can.

[Brief description of drawings]

FIG. 1 is a block diagram showing a speed signal generator for a servo system according to the present invention. 2 and the following shows an embodiment of the present invention, FIG. 2 is a block diagram of a servo system, FIG. 3 is a block diagram showing details of a speed signal generator, and FIG. 4 is a central processing shown in FIG. It is a processing flowchart which a device (CPU) performs. DESCRIPTION OF SYMBOLS 1 ... Constant number setting means 3 ... Output value calculation means 5 ... Reference magnification calculation means 7 ... Input pulse counting means 9 ... Digital-analog conversion means

Claims (1)

[Claims] 1. A speed signal generation system for a servo system, wherein a pulse encoder is provided in association with a motor or an object to be moved, and a detection pulse of the encoder is converted into a speed signal, which is converted into a voltage value and fed back to a servo amplifier. In the device, a constant value setting means for setting a designed characteristic value of the encoder and a voltage characteristic value to be output to the servo amplifier, and a subsequent output value calculation based on the characteristic value set by the constant value setting means. Means for uniformizing the arithmetic processing in the means, input pulse counting means for receiving the detection pulse of the encoder within the sampling time and counting the number of pulses input during this time, and the input pulse counting means The reference time is appropriately associated with the counting result of (1) to form a speed dimension, and the reference magnification calculation means is added to the dimension of this speed. And an output value calculation means for forming a normal speed signal by multiplying the reference magnification calculated in step 1, and a digital-analog conversion means for obtaining an output signal of the output value calculation means and converting the output signal into an analog voltage. Servo system speed signal generator.