JPH02146984A - Detection system of overspeed of ac servomotor - Google Patents

Abstract

PURPOSE:To eliminate the need for an encoder by leading out the differential signals of forward rotation and reverse rotation of three-phase pulses from feedback currents and detecting overspeed on the basis of the differential signals. CONSTITUTION:A DC power 1 is changed into AC through an inverter, and fed to a motor 4. The load currents of U phase and V phase are detected by current transformers 3a, 3b, and input to comparators 6, 7 and positive or negative charges are discriminated while the positive or negative charges of W phase are discriminated by a comparator 5 and input to a comparator 8. These signals are synchronized with clock pulses CP in a D-FF 9, phase inverters 10, 11, 12 and multiplexers 13, 14 and differentiated. The pulese are passed through a backlash circuit composed of an FF 15a, NAND circuits 16, 17 and a NOR circuit 18, an output is acquired only when two or more of pulses in the same direction are continued, and the output is measured by a period measuring circuit, thus detecting overspeed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an overspeed detection method for an AC servo motor as a measure for detecting the U-motion of a motor while driving the AC servo motor and ensuring safety.

(Prior art) Conventionally, as this type of device, A
There is something related to overspeed detection of C servo motor.

Up until now, overspeed detection has been performed by counting the feedback signal of the output pulses of the encoder "OBTACO" attached to the motor using a counter.

(Issue to be Solved by the Invention jVI) However, in such a conventional system, if an encoder failure or circuit breakage occurs, basically no pulses are output, so the speed becomes zero.

Also, since the speed calculation is based on software, there is no guarantee, and there is a possibility of the system running out of control. In this way, in reality, it cannot respond to encoder abnormalities and is of little use.

Unlike a DC motor, an AC servo motor uses a controller to control its phase, so it should normally stop when feedback stops coming, and it will not run out of control like a DC motor.

However, in robots, it is necessary to detect overspeed using hardware rather than software for safety reasons.

Here, the present invention overcomes the difficulties of the conventional method and furthermore, in order to meet the above-mentioned requirements, in view of the fact that the object is an AC servo motor, the present invention uses the motor current itself as a pulse signal to generate its feedback. The objective is to provide an overspeed detection method for AC servo motors that measures the cycle and determines whether the speed is higher than the rated speed using hardware on the servo φ drive side to detect an abnormality.

(Means for Solving the Problems) The present invention uses three-phase signals obtained by shaping the feedback current of an AC servo motor using a comparator, and delays these signals by one clock pulse using a D-flip-flop. Positive,
Combine negative logic signals, positive.

By selecting one of the six negative logic signals from the three-phase signals, the three-phase pulse is rotated in the normal direction.

Create a reverse differential circuit, and create a circuit that outputs a differential signal from this differential circuit only when pulses in the same direction come in succession, and a circuit that outputs a pulse only when the pulses output from that circuit arrive within a certain amount of time. This is an overspeed detection method for AC servo motors, which is characterized in that each circuit is provided with a signal output circuit to detect when the AC servo motor exceeds a certain speed.

(Function) Since it is configured as described above, the differential signals of normal rotation and reverse rotation of three-phase pulses are derived from the feedback current of the AC servo motor, and when pulses in the same direction come consecutively, An alarm is issued when a pulse that is output only within a certain period of time is received, so even if there is no encoder, the AC
Servo motor overspeed can be detected reliably.

(Embodiment) FIG. 1 shows a block diagram showing a circuit configuration in an embodiment of the present invention.

Reference numeral 1 denotes a DC power supply that supplies power to the AC servo motor 4, which is converted to AC via an inverter 2 and then applied.

The load current to the AC servo motor 4 is detected by a current transformer (13a, 3b, which may be a shunt) for two phases, and the current amplifier (current amplifier) outputs it to the DC power supply 1 so that the load current flowing through the AC servo motor 4 becomes an appropriate value. (not shown).

From the voltage waveform of the current detected by this load current, the differential values DIU, DIV of the highest values of the three AC phases U, V, and W of the load current,
Ask for DIW. 5.6.7.8 are all comparators, 4a, 4b, 4c are resistors, comparator 5 calculates the W phase, comparator 6, 7.8
The differential values DIU, DIV, and DIW are calculated and output.

These differential values DIU, DIV, and DIW are introduced into the D-flip-flop 9 at the next stage. This D-flip-flop 9 is, for example, a 5N74LS273 shown in FIG.
[This is the product name, 0c manufactured by Texas Instruments.
tal D-1ype Flip-Ftop wi
th C1ear] and its ID.

Differential values DIU, DIV, and DIW are applied to the 2D and 3D input terminals, respectively, and the outputs from the IQ, 2Q, and 3Q output terminals are sent to select terminals A, B, and C of multiplexers 13 and 14.
At the same time, the outputs from the IQ, 2Q, and 3Q output terminals are again applied to the 5D and 60.7D of the D-flip-flop 9.
The outputs from the 5Q, 6Q, and 7Q output terminals are returned to the input terminals and sent to the data input terminals 2, 4.1 of the multiplexer 13.
is applied to the data input terminal 4.1.2 of the multiplexer 14, and the outputs from the 5Q, 6Q, and 7Q output terminals are inverted in phase via the phase inverters 10, 11.12, and input to the data input terminal of the multiplexer 13. 5. 3.6 and data input terminals 3.6.5 of the multiplexer 14, respectively. Note that the clock pulse CP to the clock terminal CK in the D-flip-flop 9 [for example,
2 MHz] is given, and its clear terminal C
LK is maintained at the 'H' level.The multiplexers 13 and 14 are, for example, 5N74L shown in FIG.
S151 [This is the product name, DataSelector/Multip manufactured by Texas Instruments.
lexer] and each 5 TOROBE
(ENABl, E) terminal is grounded and the multiplexer
The output from the output terminal V of 13 is the flip-flop 15.
In addition, the output from the output terminal V of the multiplexer 14 is applied to the first input terminal of the NAND circuit 17, and the output from the output terminal W of the multiplexer 14 is The output is given to the input terminal of flip-flop 15a.

The flip-flop 15a and the flip-flop 15b arranged at the output stage of this device are, for example, 5N74LS109A shown in FIG.
osHIve-Edge-Trlggered F 1
ip-F 1aps with P reseL
and Cfear], and a flip-flop 15a.

Both the preset terminal PR and clear terminal CLK of 15b are maintained at the "H" level, and a clock pulse CP is applied to the clock terminal CK.

The output from the output terminal Q of the flip flop 15a is applied to the second input terminal of the NAND circuit 16, and the output from the output terminal Q is applied to the second input terminal of the NAND circuit 17.

The outputs of the NAND circuits 16 and 17 are input to the NOR circuit 18,
The output of this NOR circuit 18 is applied to the load terminal LD of the counter 20 and becomes the first input of the NAND circuit 19.

The counter 20 is, for example, 5N74LS1 shown in FIG.
61A [This is the product name, 5ynehronounces 4-bit Count manufactured by Texas Instruments
t8 is applied, a clock pulse CP is applied to the clock terminal CK, the enable terminal T and the clear terminal CLK are both maintained at the 'H' level, and the ripple-carry-out output from the flat terminal RC is maintained at the 'H' level. The output is input to the NAND circuit 21 as the first input, and the output of this NAND circuit 21 is input to the enable terminal P of the counter 20, and the data terminals DO, DI D2, . D3
The time required for this counter 20 to count clock pulses CP until it overflows is set. Also,
A sample pulse Tsaa+ple at constant intervals is input as a second input to the NAND circuit 21 (although this pulse has a smaller pulse width than the calculation pulse "L", and the pulse interval is approximately 1 millisecond).

The output of the NAND circuit 19 is the flip-flop 15b.
Hit input terminal J and send out an alarm (ARM) signal from output terminal Q. AC due to this alarm (ARM) ici issue
When overspeed of servo motor 4 is detected,
A reset (RES) signal is applied to the input terminal K of the flip-flop 15b to silence the alarm (ARM) signal.

Next, the operation of this circuit will be explained.

Normal AC servo drive [DC power supply 1. In/ (−
9-2] and motor 4, this motor current is detected by current transformers or shunts 3a and 3b for two phases [U phase, Here, these are the signals of the W phase], and these are the signals of the comparator 5.
6, 7.8, and make them "H" and "L" logic signals.

Then, the logic signals output from the comparators 6.7.8 are transferred to the D-flip-flop 9, the phase inversion SI
0, 11, 12, multiplexers 13, 14 synchronize with the clock ◆ pulse CP and differentiate it.

In other words, the signal DI input to the D-flip-flop 9
The U, DIV, and DIW (7) output signals are further input to the D-flip number flop 9 to generate a one-stage delay (DERY). The output signal of the former D-flip-flop 9 operates the multiplexers 13 and 14, and the output signal of the latter D-flip-flop 9 operates the multiplexers 13 and 14.
- Select the output signal of the flip φ flop 9 to configure a three-phase pulse differentiating circuit.

Even if the output signal of the latter D-flip-flop 9 is used for the multiplexers 13 and 14, an equivalent circuit can be constructed.

These output signals are generated every 60'' during a rotation of 360'' in electrical angle, and similarly to the two phases A and B, pulses are generated for each of the forward and reverse rotations.

This pulse is processed by flip-flop 15a1 NAND circuit 16.17 in order to ignore pulses caused by whiskers, backlash, etc.
．． A backlash circuit consisting of a NOR circuit 18 is passed through. This does not output pulses unless two or more pulses in the same direction occur. This logical sum is taken and inputted to the next stage period measuring circuit.

The period jl constant circuit is counter 20, NAND circuit 19
, 21, and a flip-flop 15b, this circuit connects the data terminals of the counter 20 between the pulses DO, DI D2 . If the data set in D3 is the output ■ of the NOR circuit 18, the RC output ■ of the counter 20, and the output ■ of the NAND circuit 19 shown in FIG.
Time until overflow [times tl, t2. t3
], and if a pulse comes before the overflow point E t5], it is detected by outputting an alarm (ARM) signal at E time t4]. That is, when Noel's O is input, the RCC output pulse of the counter 20 becomes "Lo", and the cycle continues and the pulse ■ returns to "H".At this time, if the period of the input pulse ■ is "L" of pulse b. If it is shorter than the time, the pulse O becomes "H" and an alarm (ARM) signal is output.

However, this pulse ■ is not limited to one as shown in the figure, and it is of course possible to use a circuit that outputs an alarm (ARM) signal when a predetermined number or more pulses occur within a predetermined time. be.

Therefore, the cycle of W alarm (ARM) signal detection is determined by the data set in the counter 20.

This makes it possible to detect motor overspeed without using an encoder or the like.

〔Effect of the invention〕

Thus, according to the present invention, an AC servo motor that is compact and has improved reliability can be achieved by making advanced use of the basic mechanism of an AC servo drive, without requiring a complicated mechanism such as an obtach and complicated adjustments. A method that can reliably detect overspeed can be obtained, and its usefulness will become apparent when applied to, for example, industrial robots, which is a special effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the circuit configuration in one embodiment of the present invention, FIGS. 2 to 5 are block diagrams showing the internal connections of the circuit elements, and FIG. 6 is a time chart showing the operation. 1... DC power supply 2... Inverter 3a, 3b... Current transformer [shunt etc. may be used] 4...
・AC servo motors 4a, 4b, 4c ---Resistance 5.6, 7.8
...Comparator 9...D-flip-flop [for example, 5N74LS273 (trade name) shown in Fig. 2, 0ctal D-type F 1ip manufactured by Texas Instruments
-Ft. p with C1ear. ]10.11.
12...Phase inverter 13.14...Multiplexer [For example, 5N74LS151 (trade name) shown in FIG.
ILIpleXer. ] 15a, 15b...Flip number flow tube [For example, 5N74LS109A (trade name) listed in Fig. 4, Dual J-K P manufactured by Texas Instruments
osltlve-Edge-Trlggered F
lip-Flops vlthPreset and
C1ear] 16.17, 19.21...
NAND circuit 18...NOR circuit 20...Counter [for example, SN74L shown in FIG.
S161A (product name), Synechronous-bit Counter manufactured by Texas Instruments.]

Claims (1)

[Claims] 1. Three-phase signals obtained by shaping the feedback current of an AC servo motor using a comparator, and positive and negative logic signals obtained by delaying these signals by one clock pulse using a D-flip and flop. By selecting one of the six combinational, positive and negative logic signals from the three-phase signals,
A circuit is provided to obtain differential signals for forward rotation and reverse rotation of three-phase pulses,
A circuit that outputs a pulse only when pulses in the same direction come in succession from the differentiated signal from this differentiating circuit, and a circuit that outputs a signal when a predetermined number of pulses from that circuit are received within a predetermined time. An overspeed detection method for an AC servo motor, which is characterized in that it detects when the speed of the AC servo motor exceeds a certain level.