JPS6227036Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a digital servo device that can change the rotation speed, and by switching a reference digital value that is compared with a digital value corresponding to the rotation speed of a motor that rotates at a constant speed, the rotation speed of the motor is controlled. It is an object of the present invention to provide a digital servo device that can switch the number extremely easily and with high precision.

In general, constant speed rotation servo systems for motors include an analog signal servo system that uses analog signals for each circuit making up the servo system, and a digital servo system that uses digital signals. Compared to analog servo systems, digital servo systems can reduce the number of resistors, capacitors, etc. used, and therefore have a simpler circuit configuration. It has the advantages of being small and highly reliable, as it uses highly stable clock pulses as a medium, which greatly reduces drift, and since it handles digital information, it is less susceptible to unnecessary signal superimposition and is highly reliable. There is also a significant improvement from the viewpoint of weight reduction.

The present invention is a digital servo system in which the rotational speed of the motor can be changed easily and accurately, and one embodiment thereof will be described below with reference to the drawings.

FIG. 1 shows a block system diagram of an embodiment of a digital servo device capable of switching the rotational speed according to the present invention. In the figure, reference numeral 1 denotes a controlled motor, and a disk 2 is fixedly attached to one end of its rotating shaft. S-pole and N-pole magnets 3 are alternately arranged at equal intervals on the circumferential side of the disk 2. Also magnet 3
A detection head 4 is provided with a gap surface at a position facing away from the motor 1, and each time the magnet 3 of the disk 2, which rotates integrally with the rotation of the motor 1, crosses in front of the detection head 4, the rotation of the motor 1 is increased. A substantially sinusoidal signal with a repetition frequency proportional to the speed is output from the detection head 4. This approximately sinusoidal signal is converted into a pulse train by the pulse forming circuit 5 and then supplied to the 1/2 frequency divider 6, where conversion errors in the pulse forming circuit 5 are prevented from occurring and the signal is converted into a symmetrical square wave.

This symmetrical square wave is a square wave a having a repetition frequency proportional to the rotational speed of the motor 1 as shown in FIG. At the same time as it is applied to one input terminal, it is applied to the reset terminal of the binary counter 9 of the microcomputer 8 as a reset pulse. Further, a clock pulse b shown in FIG. 2B output from the crystal oscillator 10 is applied to the other input terminal of the AND circuit 7. The repetition frequency of this clock pulse b is constant and is set sufficiently higher than that of the speed detection pulse a to prevent generation of quantization noise. The upper limit is limited to prevent costs from increasing.

In this way, the output of the AND circuit 7 has the second
As shown in FIG.
is applied to and counted here. Therefore, the binary counter 9 counts and outputs the number of clock pulses during the high level period of the speed detection pulse a for each high level period of the speed detection pulse a, thereby converting the rotational speed of the motor 1 into a binary digital quantity N. It will be converted. For example, the binary counter 9, which is reset at the rising edge of the speed detection pulse a, is reset at time t ₁
The number of clock pulses shown as _c1 in Fig. 2C that entered the high level period of the speed detection pulse a from _t2 to t2 is counted, and the count value as shown as d2 in Fig. _2D is calculated as the time.
It is output after t ₂ and held until time t ₃ when the rising edge of the next speed detection pulse a arrives, and it is output during the high level period (from time t ₃ to t ₄ ) of the next speed detection pulse a. The number of clock pulses shown as _c2 in FIG. 2C is counted and a counted value shown as _d3 in FIG. _2D is output after time t4.

The count value N of the binary counter 9, which has the values shown as d ₁ , d ₂ , and d ₃ in FIG. 2D, is digitally calculated by the microcomputer 8 as follows. The output count value N of the binary counter 9 is subtracted by a subtracter 11 to a reference value N _R corresponding to the reference speed of the motor 1, which is set in a memory 12 having a configuration as described later, as shown in FIG. 2E. The error value N _E (=N-
N _R ) is calculated. This error value N _E is calculated by the arithmetic unit 13
K ₂ times (K ₂ < 1, in this example, K ₂
= 1/2 ^M (M is any integer)) and then sequentially added by the accumulator 14 to obtain the cumulative value (value obtained by the integrating means) N _I (=ΣK ₂ · N _E ). It will be done. This accumulated value N _I is added to the output count value N of the binary counter 9 in an adder 15 to obtain an added value that changes as shown in FIG.
is supplied to K and multiplied by ₁ . Therefore, the computing unit 16
The binary number N ₀ extracted is expressed as K ₁ (N+N _I ), changes as shown in FIG. 2G, and is applied to the DA converter 17 as the output of the microcomputer 8. The timing of the above calculation operation is as shown in FIG.
It is designed to operate at the falling edge of .

The binary number N ₀ obtained by digital calculation by the microcomputer 8 as described above is DA
It is converted into an analog quantity (voltage) by the converter 17 and supplied to the motor drive amplifier 18 as a voltage h as shown in FIG. 2H, where it is amplified and then applied to the motor 1 to control its rotation speed. do.

As described above, in this embodiment, the motor 1, the disc 2, the detection head 4, the pulse forming circuit 5, the 1/2 frequency divider 6, the AND circuit 7, the binary counter 9, the adder 15, the arithmetic unit 16, and the DA In addition to the speed feedback loop consisting of the converter 17 and the motor drive amplifier 18, the digital calculation section of the microcomputer 8 has an error value N _E between the output value N of the binary counter 9 and the reference value N _R of the memory 12. K ₁ after _2x is accumulated
Since an integral feedback loop that multiplies and feeds back is configured, the motor 1 can be controlled to rotate at a constant speed with a simple circuit configuration without using a phase comparator or the like.

Now, assuming that the rotational speed of the motor 1 has become slower than the reference speed set in the memory 12, the period of the rotation detection pulse a will be longer than the reference value, so the output count value N of the binary counter 9 will be large. Then,
At the same time as the output value of the velocity feedback loop increases, N becomes larger than the reference value N _R in the memory 12, so the error value N _E becomes positive and the accumulator 1
The cumulative value N _I within 4 increases, and the output value of the integral feedback loop also increases. Therefore, the output value N ₀ of the microcomputer 8 increases, and the voltage applied to the motor 1 increases, so that the rotational speed of the motor 1 increases. Then, when the rotation speed increases until it becomes equal to the reference speed, the output count value N of the binary counter 9 becomes equal to the reference value N _R in the memory 12, and the error value N _E , which is the difference between them, becomes zero. The cumulative value N _I becomes a constant value and does not change. Therefore, the output value of the microcomputer 8
N ₀ becomes a constant value, and the voltage applied to the motor 1 also becomes a constant level, so that the rotational speed of the motor 1 is stabilized at the reference speed.

On the other hand, when the rotation speed of the motor 1 becomes faster than the reference speed, the output count value N of the binary counter 9 becomes small, and the output value of the speed feedback loop also becomes small. At the same time, since N becomes smaller than the reference value N _R in the memory 12, the error value N _E
becomes negative, the cumulative value N _I decreases, and therefore the output value of the integral feedback loop decreases. Therefore, the output value of the microcomputer 8
N ₀ also decreases, the voltage applied to the motor 1 decreases, and the rotational speed of the motor 1 decreases. Then, when the rotation speed of motor 1 decreases until it becomes equal to the reference speed, the error value N _E between N and the reference value N _R becomes zero as described above, so the output value N ₀ becomes constant and the rotation of motor 1 The speed is also stabilized at a rotational speed equal to the reference speed.

Next, the rotation speed switching operation of the motor 1 will be explained. In this embodiment, the memory 12 stores in advance n types of reference digital values N _R from N _R1 to N _Ro , and any one of the reference digital values can be set by switching a switch connected to the input terminal of the microcomputer 8 or by other means. The configuration is such that digital values are switched and output. Now, for example, the time shown in Figure 2 C
The number of clock pulses output from the gate during the period from t ₁ to t ₂ is 7 as shown by c ₁ , but during this period, the output reference digital value of the memory 12 is N _R1 , which is "7". Sometimes the error value N
_E becomes zero, and the motor 1 is rotated at a constant speed at the first rotation speed as described above.

Next, when switching the rotation speed of the motor 1, the output reference digital value in the memory 12 is changed from N _R1 to another value, for example N _R2 . Assuming that the value of N _R2 is "14" which is twice N _R1 , the above error value N _E becomes "-7". Therefore, accumulator 14
The output value N _I decreases, and the output binary number of the arithmetic unit 16
N ₀ also decreases, and the rotation speed of the motor 1 increases until the error value N _E becomes zero based on the operating principle described above.
That is, the repetition frequency of the rotation detection pulse a becomes 1/2 of the previous frequency and decreases until the output count value N of the binary counter 9 reaches "14". As a result, the motor 1 is rotated at a constant speed at a second rotation speed that is 1/2 times the first rotation speed.

Furthermore, when the output reference digital value N _R of the memory 12 is set to a value other than N _R1 or N _R2 , the rotation speed of the motor 1 is switched in inverse proportion to the reference digital value based on the same operating principle as above. It will be done.

Note that the output reference digital value of the memory 12 can be switched, for example, using a predetermined program or the like, but since this can be easily carried out by those skilled in the art, a detailed explanation thereof will be omitted.

As described above, the digital servo device capable of switching the rotational speed of the present invention gate-outputs a clock pulse of a constant frequency every pulse width period of a rotation detection pulse with a repetition frequency corresponding to the rotational speed of the motor, and By counting the number of clock pulses generated by the motor using a counter, a digital quantity corresponding to the rotation speed of the motor is obtained.
digital quantity converting means; means for switching and outputting one reference digital value from a plurality of reference digital values corresponding to the digital quantity and a plurality of preset reference rotational speeds of the motor; and the digital value and the reference rotational speed. a first _calculating means for comparing respective reference digital values corresponding to the respective reference digital values and calculating and _outputting the error values thereof; a second arithmetic means that integrates the error value by sequential addition; and a second arithmetic means that adds the output digital value of the second arithmetic means and the digital amount from the rotational speed-digital amount conversion means, respectively. Since it is composed of a third arithmetic means and a means for converting the output digital value of the third arithmetic means into an analog signal and applying it as a drive signal to the motor, the repetition frequency of the clock pulse is not changed in any way. In addition, the motor rotation speed can be changed extremely easily without the need for operations such as changing the predetermined center voltage of the motor, which was conventionally done with analog servo systems, and because digital information is used, It has the advantage of being able to construct a highly accurate switching device.

[Brief explanation of the drawing]

FIG. 1 is a block system diagram showing one embodiment of the device of the present invention, and FIGS. 2A to 2H are time charts for explaining the operation of FIG. 1, respectively. 1...Controlled motor, 8...Microcomputer, 9...Binary counter, 11...Subtractor, 1
2...Memory, 13, 16...Arithmetic unit, 14...
Accumulator, 15... Adder, 17... DA converter.

Claims (1)

[Scope of utility model registration request] a rotation speed-digital quantity conversion means for gate-outputting a clock pulse of a constant frequency for each pulse width period of a rotation detection pulse having a repetition frequency corresponding to the rotation speed of the motor and counting the number of gate-output clock pulses by a counter to obtain a digital quantity corresponding to the rotation speed of the motor; a means for switching and outputting one reference digital value from the digital quantity and a plurality of reference digital values corresponding to a plurality of reference rotation speeds of the motor that have been set in advance; a first calculation means for comparing the digital quantity with the reference digital value corresponding to the reference rotation speed and calculating and outputting an error value therebetween; and a multiplication circuit for multiplying the error value from the first calculation means by _K2 (where _K2 is a multiplication factor).
a second calculation means for integrating said error value by successively adding up the error value after calculating the error value by the formula (1), a third calculation means for performing an addition operation on the output digital value of said second calculation means and the digital amount from said rotation speed-digital amount conversion means, and a means for converting the output digital value of said third calculation means into an analog signal and applying it as a drive signal for said motor,
A digital servo device capable of switching revolutions per minute, which is provided with not only a speed feedback loop but also an integral feedback loop based on said first and second calculation means.