JP2674024B2 - Servo controller - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a servo controller for an AC servo motor, and in particular to PWM (pulse) based on a sinusoidal commutation signal having a phase corresponding to a rotation phase. The present invention relates to a servo controller that controls an exciting current by wide modulation control. [Prior Art] Generally, a current passing through a stator exciting coil is changed in a sine wave shape in accordance with rotation of a rotor magnetic pole such as a permanent magnet, and a rotating magnetic field is synchronized with rotation of the rotor to effectively generate torque. I am trying. However, when the rotation speed (hereinafter simply referred to as the speed) changes, the phase change of the current occurs due to the phase change factors such as the induced back electromotive force that occurs in the exciting coil and the coil reactance change due to the frequency change. There is a problem that the efficiency is deteriorated due to the collapse of the surface. Therefore, in order to achieve the above-mentioned synchronization, the deviation between the detected waveform of the exciting current and its command waveform is taken, and the exciting current is corrected and controlled on the basis of the deviation to substantially adjust the phase and to detect the detected waveform. The vector was analyzed by A / D conversion, and the phase was adjusted by finding the corrected command value (phase, magnitude) through the correction formula that makes this a vector according to the command (flexibility using a 16-bit microcomputer. Servo controller; Japan Management Association Small Motor Symposium, 1986, B1-3-1-7). [Problems to be Solved by the Invention] However, in the former one of the above-mentioned prior art, since the circuit related to the phase adjustment is formed in analog, the detected waveform of the exciting current contains a noise component. Since it is extremely difficult to design a filter that removes this properly, and because the amplifier and other components are affected by temperature drift, it takes a considerable amount of time to adjust the gain, and ultimately control accuracy and responsiveness are reduced. There is a problem that it is difficult to improve. On the other hand, in the latter case, after performing A / D processing on the waveform obtained from the current detector, a vector operation processor with a high speed and complicated structure is required, and the operation processing time is long, so sampling control is performed. There is a problem that the cycle becomes long and the high-speed response of control is deteriorated. Further, both of them require a current sensor for detecting the exciting current. Since the current sensor is generally large, there is a problem that it hinders downsizing of the device. Further, conventionally, the rotation position of the servo motor has been detected by an incremental rotation encoder. According to this, since only a pulse signal proportional to the rotation amount from an arbitrary position can be obtained, a reference position sensor function is separately provided, and a signal such as a magnetic pole sensor or an origin sensor is stored in a memory device such as a memory in the servo controller. Therefore, it is necessary to provide a means for counting the pulse signals so that the absolute rotational position from the reference position can be recognized. For this reason, if the contents of the memory are lost due to a power failure or the like, it is necessary to readjust the memory. Therefore, there is a problem that a backup memory and a backup power source are required. Furthermore, conventionally, the method of generating the PWM control signal is
An analog circuit compares a sinusoidal current control signal whose current phase is corrected by vector calculation or the like with a basic triangular wave. Therefore, the gain adjustment of the control element that is easily affected by temperature becomes complicated, and there is a limit in improving the control accuracy. An object of the present invention is to solve the above conventional problems,
In other words, it is to provide a servo controller that can improve control accuracy and has a simple configuration. [Means for Solving Problems] In order to achieve the above object, the present invention provides a commutation signal generating means for generating a sinusoidal commutation signal having a phase corresponding to a change in the rotational position of an AC servomotor. And PWM signal generating means for converting a sinusoidal current control signal generated based on the commutation signal and the speed command into a PWM signal, and controlling the excitation current of the AC servomotor based on the PWM signal In the servo controller, the phase adjustment amount is determined in advance by correlating it with the rotation speed to form a table, the phase adjustment amount corresponding to the input speed command is read, and the commutation signal is advanced according to the phase adjustment amount. The servo controller is characterized by being provided with a phase adjusting means for correction. Further, the commutation signal generating means is to generate the commutation signal based on the absolute rotational position signal detected by the absolute rotary encoder that detects the absolute rotational position with respect to the reference position (origin position). . Further, the PWM signal generating means reads a pulse signal having a width correlated with the instantaneous value of the current control signal taken in every predetermined sampling period from the table and outputs it, and the pulse width is the instantaneous value of the current control signal. Is used as a reference value, and a correlation that increases in a positive proportion and decreases in a negative proportion is used. [Operation] With this configuration, by setting the contents of the phase adjustment amount table based on the actual measurement data obtained in advance, the phase adjustment amount suitable for the current speed can be set in an extremely short time. It can be obtained, and the phase of the commutation signal is rapidly advanced based on this. As a result, the phase shift between the rotating magnetic field and the rotor is minimized, and the efficiency is improved. Further, since it is not necessary to detect the current, troublesome problems such as the space of the current sensor and measures against current noise can be solved. Furthermore, since the commutation signal is generated based on the absolute rotation position signal detected by the absolute rotation encoder, the absolute position data of the rotor will not be lost even if a power failure occurs,
It is possible to eliminate the need for a backup power supply and increase the reliability and operating rate of the device. Further, when generating the PWM signal based on the sinusoidal current control signal, the data of the pulse width determined in advance corresponding to the instantaneous value of the current control signal is stored in the ROM,
Since the pulse width corresponding to the instantaneous value input at each sampling cycle is read and the PWM signal is generated based on this, a comparison is made with the basic triangular wave and analog.
Compared with the conventional method of generating a PWM signal, the PWM signal can be generated with high accuracy at high speed and with a simple configuration. Examples Hereinafter, the present invention will be described based on examples. FIG. 1 shows a block diagram of a servo controller of an embodiment to which the present invention is applied. Although this embodiment shows an example applied to a three-phase AC servomotor, the characteristic part of the present invention is not directly related to the number of phases. Therefore, it can be applied to a single-phase servomotor, and the control will be described for one phase. The servo controller 1 has functions such as position control, speed control, and current control of the servo motor. In FIG. 1, for simplification, the parts relating to the position control and the speed control are not shown, and the frequency control and the current control part based on the speed command determined by them are shown. The servo controller 1 is composed of digital circuit means, and outputs to the pre-driver 2 a PWM control current control signal of a frequency corresponding to the speed command for each phase. The pre-driver 2 drives the switch means of the driver 3 according to the input current control signal, controls the exciting current of the servo motor 4 and holds the speed at a specified value. The rotational position of the servo motor 4 is detected by the rotary encoder 5. The rotary encoder 5 is an absolute type that detects the absolute rotational position angle of the rotor from the reference position, and a rotary encoder that can detect the absolute rotational position over multiple revolutions is used if necessary. The rotational position θ of the servo motor 4 detected by this is input to the speed calculation means 11 and the commutation signal generation means 12 of the servo controller 1. The speed calculation means 11 is adapted to obtain the speed υ by the time change of the inputted θ. The commutation signal generation means 12 is adapted to generate and output a sinusoidal commutation signal sin (θ) corresponding to a change in the input θ. That is, as is well known, a basic waveform that forms a magnetic field distribution shape is generated according to the rotation of the magnetic pole position of the rotor. The commutation signal generating means 12 is formed by a ROM (read only memory), and when the absolute rotation position θ is input,
The corresponding sin (θ) is read and output. On the other hand, with respect to the speed command υ ₀ output from the higher-order control means (not shown), the adder 13 obtains the deviation Δυ from the detected speed υ. This deviation Δυ is multiplied by the commutation signal sin (θ) in the multiplier 14 to obtain the current control signal i ₀ = Δυ · sin (θ) having the instantaneous value h of the level according to the speed command. Phase adjusting means 15
Is input to The phase adjusting means 15 is for compensating for the phase delay of the exciting current generated in accordance with the increase in speed as described above, and in advance so as to advance the phase of the current control signal i in correspondence with the input speed command υ _0. It is configured to include a ROM in which the phase adjustment amount φ is tabulated in correspondence with υ ₀ based on an actual measurement value or the like. Then, the input current control signal i ₀ = Δ
As for ν · sin (θ), the current control signal i = Δν · sin (θ, φ) advanced in accordance with the speed command υ ₀ at that time is immediately output. As described above, since the phase adjustment is performed promptly without performing the vector operation processing that takes a long operation time, the digital control cycle (sampling cycle) can be shortened, and the quick response of the control and the accuracy can be improved. . The change in the phase-adjusted current control signal i is input to the pulse width conversion means 16 and has a width (t ₀ × n) according to the instantaneous value h at every constant period tc as shown in FIG. Converted to a signal. Here, t ₀ represents the clock pulse period, and n represents the number thereof. That is, when the instantaneous value h = 0 of the current control signal i is the reference width (t ₀ × n / 2),
It has a minimum value (zero) when it has a positive maximum value hmax, and a proportional relationship in the middle. The correlation is tabulated and stored in advance in the ROM, and the current control signals i _j (j = 1, 2, 3, ...) At a constant cycle tc.
...), read the pulse width data (t ₀ × n _j ) corresponding to the instantaneous value h _j at that time, and down-convert the pulse train signal composed of the pulses having the pulse width corresponding to the down counter 17
Output. A clock pulse (frequency f ₀ ) from the clock oscillator 19 and a carrier pulse (carrier frequency fc) from the frequency divider 20 are input to the down counter 17. Here, the clock pulse f ₀ and the above t ₀ have a relation of t ₀ = 1 / f ₀ , and f ₀ and fc are fc =
There is a relationship of f ₀ / m (m is an integer). Also, there is a relation of fc = 1 / tc. Then, as shown in FIG. 3, the down counter 17 is reset at the timing of the carrier pulse fc and counts the pulse width (t ₀ × n _j ) of the input current control signal at the timing of f _0. , N _j is reached, a countdown signal is output to the flip-flop 18. The flip-flop 18 constitutes an interface with an external circuit, and is set by the carrier pulse fc input from the frequency divider 20 as shown in FIG. 3 and reset by the countdown signal.
Therefore, the output of the flip-flop 18 is the same pulse train signal as the pulse train signal output from the phase adjusting means. The pulse width conversion means 16, the down counter 17, and the flip-flop 18 form a PWM signal generation means. The PWM signal of the current control signal composed of the pulse train thus formed is output to the pre-driver 2, whereby the switch means of the driver 3 is turned ON / OFF to PWM-control the exciting current of the AC servomotor 4, The rotation speed υ is adapted to match the speed command υ ₀ . The PWM signals are formed by shifting the phases of 120 ° corresponding to the three phases and are output to the pre-driver 2. Further, the pre-driver 2 is adapted to generate an inversion signal for driving the switch means of the paired arm of each phase. With the configuration as described above, according to the present embodiment, there are the following effects. When generating a sinusoidal commutation signal, the absolute rotational position of the rotor is detected by detecting the rotational position of the rotor with an absolute rotary encoder and generating it based on this detected rotational position signal. It is possible to always detect regardless of the above, and the problem associated with the memory loss as in the case of the conventional magnetic pole sensor, the increment rotary encoder and the memory is solved. As a result, the reliability of the system is improved, and the readjustment work after the power failure is not necessary and the system can be immediately restarted, so that the productivity is improved. Moreover, since a backup power supply, a magnetic pole sensor, etc. are not required, the number of parts can be reduced. When adjusting the current phase, the phase adjustment amount determined in advance corresponding to the speed is stored in the ROM, and the phase adjustment amount corresponding to the input speed command is read to correct the phase of the current control signal. By doing so, complicated vector operation processing is not required, and the phase adjustment processing time can be extremely shortened, which can improve the high-speed response and enable a wide range from low speed to high speed. Therefore, there is an effect that highly efficient control can be realized. Moreover, a current sensor for phase adjustment, an A / D converter, and a DSP (digital signal processor) for vector calculation are unnecessary. As a result, there is no problem such as noise or temperature drift that has been an obstacle in the analog system including the conventional current sensor, and the gain adjustment is simplified, so that the control accuracy can be improved. In addition, the number of expensive and large parts can be reduced, and the practicability can be improved. When a PWM signal is generated based on a sinusoidal current control signal, the data of the pulse width determined in advance corresponding to the instantaneous value of the current control signal is stored in ROM, and the moment when it is input at each sampling cycle. The pulse width corresponding to the value is read out, and the PWM signal is generated based on this value.
Compared with the conventional method of generating the M signal, there is an effect that the PWM signal can be generated with high accuracy, at high speed, and with a simple configuration. That is, according to the conventional analog method, there are many problems in which it is difficult to remove the influence of noise contained in the detected current and temperature drift of the analog control system. However, according to the present embodiment, such a problem also occurs. Can be resolved. [Effects of the Invention] As described above, according to the present invention, there is an effect that the control accuracy can be improved and the configuration can be simplified.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an embodiment of the present invention, and FIGS. 2 and 3 are diagrams for explaining a PWM signal generation procedure in the embodiment of FIG. 1 ... Servo controller, 2 ... Rotation encoder, 12 ... Commutation signal generating means, 15 ... Phase adjusting means, 16 ... Pulse width converting means, 17 ... Down counter, 18 ... Flip-flop.

   ────────────────────────────────────────────────── ─── Continuation of front page    (56) References JP-A-62-126890 (JP, A)                 JP 60-261386 (JP, A)                 JP 59-117485 (JP, A)

Claims (1)

(57) [Claims] Rotational position detection means for detecting the rotational position of the AC servomotor, speed calculation means for obtaining a rotation speed based on the change in the rotational position detected by the rotation position detection means, and the rotation calculated by the speed calculation means Speed deviation calculating means for obtaining a speed deviation between the speed and the input command speed; a commutation signal generating means for generating a sinusoidal commutation signal having a phase corresponding to the change of the rotational position; Multiplying means for generating a sinusoidal current control signal by multiplying the deviation and the commutation signal, PWM signal generating means for converting the current control signal into a PWM signal, and an AC servomotor based on the PWM signal In the servo controller for controlling the exciting current of, the phase adjusting means for correcting the phase advance of the current control signal based on the speed command is provided. The rotation position detection means is an absolute rotation encoder that detects the rotation position as an absolute position from a reference position, and the commutation signal generation means includes the predetermined commutation signal corresponding to the rotation position. A memory for storing the value of the rotation signal, and reads and outputs the value of the commutation signal corresponding to the rotational position detected by the absolute rotary encoder. Having a memory storing a predetermined amount of phase adjustment correlated with the above, reading the amount of phase adjustment corresponding to the input speed command, and correcting the phase of the current control signal according to the amount of phase adjustment Servo controller characterized in that 2. The PWM signal generating means has a memory in which a predetermined pulse width signal is stored in correlation with the instantaneous value of the current control signal, and is correlated with the instantaneous value of the current control signal taken in every predetermined sampling period. The pulse width signal is read out from the table and output, and the pulse width has a correlation in which it is positively proportionally increased and negatively proportionally decreased with reference to zero of the instantaneous value of the current control signal. The servo controller according to claim 1, wherein: