JPH0564558B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a ROM that synchronizes with the rotational position of the rotor.
Sequentially read out the sine wave signals stored in advance in the memory of the SM type
This invention relates to a starting circuit for an SM type AC servo motor that controls the current of the armature coil of the AC servo motor. As is well known, this type of S-type AC servo motor has a counter sequentially count pulse signals generated from a speed detector at a period corresponding to the rotational speed of the rotor, and this count value specifies the phase of the sine wave. This phase signal is used to read out a sine wave signal previously stored in a memory to control the current in the armature coil of the SM type AC servo motor. By the way, this type of SM type AC servo motor requires a start signal to start the motor, but conventionally, this start signal indicates the displacement of the rotor from the reference position output from a position detector. The rotary drive signal is coded and formed using a position signal and a speed reference signal given from the outside. That is, the speed reference signal includes a sign that changes depending on the direction of rotation (forward or reverse), and the position signal is assigned a sign using this sign to control the armature current to be positive or negative. Therefore, a coding circuit was required. Furthermore, after the rotor has rotated once and reached the reference position, a switching circuit or the like is required to control the drive current based on the sine wave signal read from the memory using the phase signal generated from the counter. The drawback was that the circuit configuration became complicated. The present invention was made in view of these drawbacks, and its object is to provide an SM type AC servo motor that can generate a starting signal with a simple configuration. In order to achieve the above object, the present invention is configured such that the position detector outputs a reference signal each time the rotor reaches the reference position, and also generates a multiple-bit position signal that goes around each time the rotor rotates by a predetermined electrical angle. and,
At startup, until the position detection outputs the reference position signal, every time this position signal changes, the step-shaped activation signal waveform stored in the memory is read out, and the reference position signal (index signal) is read out. This step-like starting signal is used to control the armature current until the start is generated. Hereinafter, the present invention will be explained in detail based on examples. FIG. 1 is an overall block diagram showing one embodiment of the present invention, where SM is an SM type AC servo motor having, for example, a four-pole permanent magnet rotor, and PD is a position for detecting the rotational position of the rotor. The detector RE is a rotary encoder that outputs a pulse signal with a period inversely proportional to the rotational speed of the rotor, and the output signals of the position detector PD and rotary encoder RE are input to the sine generating circuit SWG. Then, the sine wave generator circuit SWG (including the D/A converter) generates a sine wave signal of the U phase and W phase among the U, V, and W phases based on the output signals of the position detector PD and rotary encoder RE. is generated and this signal is sent to the multiplier 10,1.
Supply to 1. On the other hand, the speed/feedback signal v _p created based on the output signal of the rotary encoder RE is input to the adder 12, where the speed reference signal v _i
The difference is required. This difference signal (v _i −v _p ) becomes a current amplitude command signal i of the armature current flowing through the U, V, and W phase armature coils, and is input to the multipliers 10 and 11, where the U, V, and W phase By being multiplied by the phase sine wave signal, it is converted into U-phase and W-phase current command values a and c. These U-phase and W-phase current command values a and c are pulse-width modulated after the deviations from the U-phase and W-phase armature current feedback signals i _p (U) and i _p (W) are determined, respectively. It is input to circuits (PWM) 13 and 15. On the other hand, the current command value b of the V phase is the U phase,
The W-phase current specified values a and c are determined by -(a+c), and then the deviation from the feedback signal i _p (V) of the V-phase armature current is determined and input to the V-phase pulse width modulation circuit 14. be done. As a result, the pulse width modulation circuits 13, 14, and 15 of each phase generate pulse signals that selectively turn on and off the transistors of the transistor bridge B, and the armature current of each phase changes to the current command values a, b, controlled to a value commensurate with c,
The SM type AC servo motor SM comes to rotate at a rotational speed corresponding to the speed reference signal v _i . By the way, the position detector PD of this embodiment has three sensors arranged at mechanical angle intervals of 60 degrees as shown in Fig. 2.
photo sensors 20A to 20C. Projections 21A and 21 of the slit plate 21 which face the light from the light emitting diodes facing the photo sensors 20A to 20C at a mechanical angle of 180° and have a spread of 90°.
By shielding B in synchronization with the rotation of the rotor, every time the rotor rotates by 90 degrees in mechanical angle, the logic changes to "1" or "0" as shown in the waveform diagram in Figure 3. The timing is electrical angle, and the configuration is such that a 3-bit signal that appears every 60 degrees can be obtained. That is, it is constructed so that a 3-bit signal as shown in Table 1 below, which goes around every 360 degrees in electrical angle, can be obtained.

[Table] On the other hand, in the sine wave generation circuit SWG, for example, the circuit that generates the U-phase sine wave signal U is composed of a gate circuit G, a counter CRT, and a memory MEM, as shown in FIG. G remains open until the index signal Z is input from the rotary encoder RE as a reference position signal indicating that the rotor has made one revolution and reached the reference position, and the 3-bit output from the position detection monitor PD remains open. The position signals U _p , V _p , W _p are applied as upper address signals A ₁₁ to _{A 9} of the memory MEM. For example, 8-bit phase signals B ₈ to B ₁ for specifying the phase of the sine waveform are inputted to the memory MEM as lower address signals A ₈ to _{A 1} from the counter CTR, but the counter CTR receives the first index signal. A reset state is maintained until Z occurs. Therefore, until the first index signal Z is generated, that is, until the rotor makes one revolution, the lower address signals A ₈ to _{A 1} are stored in the memory MEM.
are all "0", and the address signals of the position signals U _p , V _p , and W _p are input as the upper address signals A ₁₁ to _{A 9} . Therefore, A ₁₁ = U _p , A ₁₀ = V _p , A ₉ = W _p , A ₈ ~
If a starting signal waveform that changes in positive and negative polarities in a stepwise manner is stored at the address of _A1 ="0", for example, as shown in FIG. During this time, this step-like activation signal waveform is read out from the memory MEM.
Therefore, by using this step-like starting signal waveform as the U-phase starting signal U, the SM type AC servo motor can be started without providing a signed circuit or the like. The same holds true for the remaining W phases. After the motor is started, the gate circuit G is closed while the first index signal Z is generated, the reset state of the counter CTR is released, and the speed pulse signal A generated from the rotary encoder RE is sent to the counter CTR. Sequentially count and convert the count value to the phase signal _B8 of the sine wave meter.
By supplying the signal as _B1 to the memory MEM, a sine wave signal as shown in FIG. 5b, which has been previously stored in the memory MEM, can be read out. After this, the count value of the counter CTR is reset every time the index signal Z is generated, and it counts the speed pulse signal A again, and repeatedly outputs the phase signals B ₈ to B ₁ of 0° to 360° in electrical angle. It becomes like this. As a result, the SM type AC servo motor SM shifts from the startup mode to the normal rotation mode and continues to rotate. In this case, if the position signals U _p , V _p , W _p are further subdivided and the number of change steps is increased, and the number of change steps of the start signal waveform is further increased, the start signal will approach a sine wave and the start will be smoother. It can be done. As is clear from the above description, the present invention has a configuration in which the position detector outputs a reference signal each time the rotor reaches the reference position, and also generates a multiple-bit position signal that goes around each time the rotor rotates by a predetermined electrical angle. year,
Furthermore, until the reference position signal (index signal) is generated, every time this position signal changes, the step-shaped start signal waveform stored in the memory in advance is read out, and the electric machine is activated by this step-like start signal. The device is configured to start by controlling the slave current. This eliminates the need for a coding circuit for activation. In addition, during startup until the reference position signal is output, a step-shaped startup signal waveform is read out from the memory using the multi-bit position signal output by the position detector, and the step-like startup signal waveform is read out from the memory according to the positive or negative sign indicated by the speed reference signal. Controls the armature current to rotate the armature forward and reverse. This eliminates the need for the switching circuit described as the conventional technology, allowing for a simple configuration.
Can start SM type AC servo motor. Furthermore, by increasing the number of steps in which the starting signal waveform changes, smooth starting can be achieved.

[Brief explanation of the drawing]

Fig. 1 is an overall block diagram showing an embodiment of the present invention, Fig. 2 is a diagram showing an embodiment of a position detector, Fig. 3 is a diagram showing an output signal waveform of the position detector, and Fig. 4 is a diagram showing an output signal waveform of the position detector.
This figure is a block diagram showing an embodiment of a circuit for generating a sine wave signal of an arbitrary phase and a starting signal, and FIG. 5 is a diagram showing the waveforms of the starting signal and sine wave signal generated in FIG. 4. SM...SM type AC servo motor, RE...Rotary encoder, PD...Position detector, SWG...
Sine wave generator circuit, G... gate circuit, CTR...
Counter, MEM...memory.

Claims (1)

[Claims] 1 Every time the rotation of the SM type AC servo motor reaches a reference position, a counter is reset by the reference position signal output from the rotary encoder, and the counter is set at a period inversely proportional to the rotational speed of the rotor. The pulse signals generated from the rotary encoder are counted to generate a phase signal that specifies the phase of the sine wave, and this phase signal is used to read out the sine wave signal previously stored in the memory.
In the SM type AC servo motor that controls the current of the armature coil of the AC servo motor, a position detector is installed that generates a multiple-bit position signal that goes around each time the rotor rotates by a predetermined electrical angle.
In addition to the storage address specified by the phase signal outputted from the counter, the memory is provided with a storage address specified by the plurality of bits of position signal, and this storage address has a memory address specified by the plurality of bits of position signal. Correspondingly, a starting signal waveform that changes in a stepwise manner is stored, and the multi-bit position signal is applied to the address input of the memory during starting until the first reference position signal from the position detector is generated. A starting circuit for an SM type AC servo motor, characterized in that the current in an armature coil is controlled by a step-like starting signal waveform corresponding to the position signal.