JP2529297B2 - Servo device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo device equipped with a speed error detector that measures a cycle of a rotation speed signal of a rotating body and outputs error data from a reference value as a digital value. It is a thing.

2. Description of the Related Art FIG. 3 shows a typical functional block diagram of a rotation speed control system of a capstan motor of a home video tape recorder. In FIG. 3, from the frequency generator 2 connected to the capstan motor 1 to the fourth
An AC signal as shown in FIG. 3A is output, but this AC signal has a repeating cycle depending on the rotation speed of the capstan motor 1, and the FG signal amplifier 3 generates a fourth cycle.
The waveform is shaped by being amplified to a square wave as shown in FIG. Further, in the multiplication circuit 4, the signal waveform of FIG. 4 (C) is created from the signal waveform of FIG. 4 (B) and sent to the speed error detector 5. On the other hand, in the velocity error detector 5, the period from the leading edge (leading edge) to the next leading edge of the signal waveform of FIG. 4 (C) is digitally measured by a counter or the like, and the error data from the fixed reference value is obtained. Is output. This error data is supplied to a D / A converter 7 after gain compensation in the frequency domain is performed by a digital filter 6, and an output of the D / A converter 7 is a motor driving circuit for driving the capstan motor 1. 8 is supplied.

Therefore, the block shown in FIG. 3 constitutes a closed rape speed control system for rotating the capstan motor 1 at a low speed. Further, in the apparatus shown in FIG. 3, the multiplication circuit 4 is used to improve the response of the speed control system. That is, the rotation speed of the capstan motor is the fourth
Each time the leading edge of the signal waveform in FIG. 6C arrives, it is measured as an average value of the speed change from the previous leading edge arrival time (generally called a moving average), but the multiplier circuit 4 is used. If not, the distance between the leading edges of the signal waveform shown in FIG. 4 (B) is measured, and the measurement interval becomes long, which deteriorates the response characteristic of the control system. To eliminate this, the frequency generator 2
However, there was a limit due to the problem of mechanical processing accuracy. Therefore, the method of electrically multiplying the output of the frequency generator is often used, and the edge multiplication method as shown in FIG. 4 and the output signals from a plurality of generator coils electrically arranged with different phases are also used. Then, a method of multiplying the frequency of the rotation speed signal is used.

Problems to be Solved by the Invention By the way, the signal waveform diagram shown in FIG. 4 (B) actually has a duty cycle as shown in FIG. 5 (B) due to the input offset voltage Eo of the FG signal amplifier 3. Is deviated from 50%, and as a result, the interval between the leading edges alternates between long and short as shown in FIG. 5 (C). As a result, the error data in the plus direction and the error data in the minus direction are alternately output from the speed error detector 5, and as a result, the ripple of the output voltage of the DA converter 7 increases and the control quality deteriorates. To do.

Means for Solving the Problems In order to solve the above-mentioned problems, in the servo device of the present invention, a speed error that measures a cycle of a rotation speed signal of a rotating body and outputs error data from a reference value as a digital value. Detection means, delay means for holding the sign of the error data until the next measurement, a code collator for collating the sign of the error data with the code held by the delay means, and the rotation speed signal X section and Y which are alternately repeated in series
A flip-flop for generating an identification signal of the section, and a reference for supplying the speed detection means with identification of the X section and the Y section based on the identification signal when a mismatch output signal is supplied from the code collator. A balance corrector that increases the value data in one section and decreases it in the other section, and a drive unit that drives the rotating body based on the error data.

Operation According to the present invention, with the above-described configuration, it is possible to realize a servo device that can perform high-quality control even when the edge interval of the rotation speed signal is unbalanced.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a servo system according to an embodiment of the present invention, and the same blocks as in FIG. 3 are shown by the same reference numbers. In the apparatus of FIG. 1, the error data from the speed error detector 5 is sent to the digital filter 6, and the data including the sign bit (usually, the most significant bit of the data is treated as the sign bit) is delayed. It is also sent to one input side of the device 11 and the code collator 12. The output data of the delay unit 11 is supplied to the other input side of the code collator 12, and the output of the code collator 12 is supplied to the balance corrector 13 constituting the reference value correction block 10 as a reference value correction command signal. Has been sent. On the other hand, the output signal of the multiplication circuit 4 is supplied to the speed error detector 5 and also to the flip-flop 14 constituting the reference value correction block 10, and the output of the flip-flop 14 is used as the area switching signal. It is supplied to the balance corrector 13. Further, the fixed reference value data from the reference value generator 15 is the balance correction device 13
Is supplied to the speed error detector 5 after being subjected to appropriate numerical correction.

Regarding the servo apparatus configured as described above, the block configuration diagram of FIG. 1 and the operation flowchart of FIG.
The operation will be described with reference to the signal waveform diagram of FIG. The speed error detector 5 shown in FIG. 1 includes a counter that measures the interval by the number of clock pulses each time the leading edge of the output signal of the multiplier circuit 4 arrives, and a reference value generator 15 based on the count amount of the counter. It is assumed that the error correction data is created by subtracting the correction amount stored in the balance corrector 13 from the fixed reference value output by.

First, in branch 51 of FIG. 2, it is determined whether or not the leading edge of the signal waveform of FIG. 5 (C) has arrived, and if the edge has not arrived, the process ends without executing anything. If so, the process is moved to the branch 52. The branch 52 determines whether or not the output of the flip-flop 14 in FIG. 1 is "0". This is for dividing the X section and the Y section in FIG. The balance corrector 13 stores the X and Y correction amounts corresponding to each section. If the determination result in the branch 52 is “yes”, in the processing block 53, the correction amount of the X section stored in the balance corrector 13 is changed from the count amount of the counter configuring the speed error detector 5 to the fixed reference value. Is subtracted, the result is output as error data, and the process is transferred to the branch 54. In the branch 54, the previous error data held in the delay device 11, that is, the sign of the error data in the Y section and the sign of the error data measured this time are collated, and if they match, the subsequent processing is executed. Although the process ends without doing so, the process moves to the branch 55 if they do not match. In the branch 55, it is determined whether the measurement result this time is an error in the plus direction or an error in the minus direction. If the former, the process moves to the processing block 56, and if the latter, the process moves to the processing block 57. . In the processing block 56, the correction amount in the X section stored in the balance corrector 13 is increased,
The correction amount in the Y section is reduced by the same amount. That is, X
Even if the reference value corresponding to each section is corrected by maintaining the balance such that the correction amount of the section and the correction amount of the Y section are always zero, the average reference value is still the reference value generator. It is equal to the fixed reference value output by 15, and the rotation speed of the capstan motor 1 does not fluctuate.
Further, in the processing block 57, the correction amount in the X section is decreased,
The correction amount in the Y section is increased by the same amount. Processing block
After changing the correction amount of the X section and the Y section in 56 or the processing block 57, the error data sent to the digital filter 6 is also changed in the processing block 58. Even if this operation is omitted, the correction amount of each section has been changed, so error data with less section fluctuation will be obtained from the next time, but if you consider the response as a servo system, it will be a little faster. It is preferable to reflect the result.

Now, if the determination result in the branch 52 is "no", the process is transferred to the process block 59, but the process is almost the same as the process block 53 here. That is, the processing block
In 53, the error data is calculated using the fixed reference value and the correction amount in the X section, but in the processing block 59, the fixed reference value and the Y value are calculated.
The error data is calculated using the correction amount of the section. Also, branch 60 and branch 61 following processing block 59.
Makes the same determination as branch 54 and branch 55.

As described above, the servo device shown in FIG. 1 has a reference value (balanced with a fixed reference value from the reference generator 15) adapted to each section even if section imbalance exists in the period of the speed detection signal. Since the sum of the correction amounts stored in the corrector 13) can be obtained by sequential learning, finally D-A
The output ripple of the converter 7 is almost eliminated, and only the natural oscillation component based on the quantization error is left.

By the way, the processing flow shown in FIG. 2 is executed every time the leading edge of the velocity signal in FIG.
In 57, the learning gain is determined by how much the section correction amount is increased or decreased. If the learning gain is set too high, the servo system becomes unstable, and if it is too low, it takes a long time to complete the learning. If the correction is made in the processing block 56 or the processing block 57 according to the magnitude of the error, the learning gain itself also decreases toward the convergence of the error, which is preferable also from the stability of the system. Specifically, the value obtained by multiplying the error data measured at each time point by a coefficient (learning coefficient) smaller than 1 may be increased or decreased from the section correction value.

By the way, in the embodiment shown in FIG.
Although the case where the output signal of is multiplied and used is described, the present invention can be applied to the fifth embodiment even in a device that does not use the multiplier circuit.
The same effect can be obtained if there is an imbalance in the cycle of the rotation speed signal as shown in FIG.
For example, when using a photoelectric detection type frequency generator that synthesizes and outputs the outputs of a plurality of light receiving elements arranged at a minute pitch, or for a frequency generator having a plurality of generating coils as described above. However, a sufficient effect can be obtained.

Further, in the embodiment of FIG. 1, for convenience of explanation, individual blocks such as a speed error detector 5, a delay device 11, a code collator 12, a balance corrector 13, a flip-flop 14, a reference value generator 15 are arranged. However, some of the functions of other blocks can be used, and of course, these can be realized by a program of a microprocessor. For example, since the digital filter 6 generally has a buffer memory on the input side, the delay device 11 becomes unnecessary if the function of the buffer memory is used, and the reference value generator 15 uses the fixed memory of the microprocessor. You can
The main part of the speed error detector 5, the code collator 12, the balance corrector 13, and the flip-flop 14 can all be realized by a program.

EFFECTS OF THE INVENTION As is clear from the above description, the servo device of the present invention measures the period of the rotation speed signal of the rotor and outputs the error data from the reference value as a digital value. A detector 5), a delay unit (delay unit 11) that holds the sign of the error data until the next measurement, and a code collator 12 that matches the sign of the error data with the code held by the delay unit. A flip-flop 14 for generating an identification signal for the X section and the Y section, which are alternately repeated in time series from the rotation speed signal, and the identification signal based on the identification signal when a mismatch output signal is supplied from the code collator. Then, the X section and the Y section are discriminated, and the reference value data supplied to the speed detecting means is increased in one section and decreased in the other section, and based on the error data. In addition, since the driving means (motor drive circuit 8) for driving the rotating body is provided, high-quality control with less error detection ripple can be performed even when the edge inverter of the rotation speed signal is unbalanced. Has the effect.

[Brief description of drawings]

FIG. 1 is a block diagram of a servo system showing an embodiment of the present invention, FIG. 2 is a flow chart explaining the operation of the system of FIG. 1, FIG. 3 is a block diagram showing a conventional example, FIG. 4 and FIG. FIG. 5 is a signal waveform diagram of the main part of FIG. 5 ... Speed error detector, 8 ... Motor drive circuit, 10 ... Reference value correction block, 11 ... Delay device, 12 ... Sign collator.

Claims (1)

(57) [Claims] 1. A speed error detecting means for measuring a cycle of a rotation speed signal of a rotating body and outputting error data from a reference value as a digital value, and a delay means for holding a sign of the error data until the next measurement. And a code collator for collating the code of the error data with the code held in the delay means,
X that is alternately repeated in time series from the rotation speed signal
When a discrepancy output signal from the code collator and a flip-flop for generating an identification signal for the section and the Y section are supplied, the X section and the Y section are identified based on the identification signal, and the speed detecting means. A servo device comprising: a balance corrector for increasing the reference value data supplied to one section in one section and decreasing the reference value data in the other section; and a drive unit for driving the rotating body based on the error data.