JPS61285086A - Controller for servo motor - Google Patents

Abstract

PURPOSE:To readily detect the overload of a servo motor by providing an overload detector for detecting an overload on the basis of the difference between a deviation signal and a speed signal. CONSTITUTION:A subtractor 10 inputs a deviation signal 6a and a speed signal 3a and outputs a signal 10a in response to the difference of the both signals. A comparator 11 compares the input signal 10a with a variable set value contained therein, and outputs an overload detection signal 11a when the value of the signal 10a is the set value or higher. Thus, when a servo motor becomes an overload, the speed of the motor is decelerated to increase the difference between the deviation signal and the speed signal. As a result, the overload detection of the motor can be readily detected without influence to the amplitude of the current of the motor.

Description

Detailed Description of the Invention [Technical Field to which the Invention Pertains] The present invention relates to a servo motor control device used for an arm positioning mechanism in a robot, etc., and particularly to an overload detection device that can easily detect overload of a servo motor. The present invention relates to a configuration of a servo motor control device having a section.

[Prior art and its problems]

FIG. 4 is a block diagram of a conventional servo motor control device.

In the figure, 1 is a servo motor that drives a load (not shown), such as an arm in a robot device, and 2 is a pulse sensor that outputs a pulse signal according to the rotation state of the servo motor 1 as a rotation signal 2a. It is an encoder. The rotation signal 2a is a signal in which the integrated value of the number of pulses constituting the signal corresponds to the rotation angle of the servo motor 1, and the frequency of the pulses corresponds to the rotation speed of the servo motor 1. 3 is a speed signal generation unit which receives the rotation signal 2a and converts the frequency of the pulse into a speed signal 3a as an analog voltage signal corresponding to the rotation speed; 4;
is an up/down force counter in which the positioning command signal 5 for the servo motor 1, which is composed of a series of pulse trains, is inputted to the increasing terminal Cζ, and the rotation signal 2a is inputted to the decreasing terminal, and 6 is stored in the counter 4. This is a D/A converter that converts the number N of pulses into an analog voltage signal 6a and outputs it. Since the signal 6a is a signal formed as described above, it is a deviation signal corresponding to the difference between the positioning command signal 5 and the rotation signal 2a, and 7 is a deviation signal corresponding to the difference between the positioning command signal 5 and the rotation signal 2a.
and a D/A converter 6, which outputs a command signal 5 and a rotation signal 2.
This is a deviation calculation section which receives input signal 6a and outputs a deviation signal 6a. The servo motor 1 performs a predetermined control operation using the deviation signal 6a as a set value and the speed signal 3a as a feedback value, and the running current is controlled by the output signal 8a of the speed control section 8 which outputs a control signal 8a. (speed controlled). Reference numeral 9 denotes a servo motor control device consisting of the above-mentioned parts except for the servo motor 1.

In FIG. 4, the servo motor control device 9 is configured as described above, and the command signal 5 has a relationship curve between the frequency of the pulse train constituting this signal and the elapsed time that is approximately trapezoidal, and Since it is customary that the cumulative number of pulses corresponding to the area of the trapezoid corresponds to the required rotation angle of the servo motor 1, when the command signal 5 is input in FIG. 1 accelerates from a stopped state, shifts to uniform rotational motion, and eventually decelerates and stops at a predetermined rotational position commanded by signal 5. In FIG. 4, the servo motor 1 operates in this manner, but when the motor is overloaded, the normal current flowing becomes excessive. For this reason, conventionally, the overload state of the motor 1 has been detected by
, <1 flow is monitored and detected. However, if such a motor overload detection mechanism is adopted, the normal motor current value changes depending on the speed commanded to the upper motor by the motor control device f, so the servo motor may become overloaded. As a result, when the amount of overload of the servo motor is small, the increase in the motor current is small, so an overload state of the motor is detected based on the current Cζ. The problem is that it is difficult.

[Purpose of the invention]

An object of the present invention is to provide a servo motor control device equipped with an overload detection section that can easily detect overload of a servo motor by solving the above-mentioned problems in conventional servo motor control devices. With the goal.

[Key points of the invention]

In order to achieve the above-mentioned object, the present invention includes a rotation detection section that outputs a rotation signal according to the rotation state of the servo motor;
a speed signal generator that outputs a speed signal according to the rotational speed of the servo motor; a deviation calculation section that receives a positioning command signal and a rotation signal for the servo motor and outputs a deviation signal according to the difference between the two signals; A servo motor control device comprising: a speed control section that controls the speed of the servo motor using a signal as a set value and a speed signal as a feedback value; detecting overload of the servo motor based on a difference between a deviation signal and a speed signal This is a servo motor control device with an overload detection section provided with an overload detection section.With this configuration, when the servo motor becomes overloaded, the speed of the motor slows down and a deviation signal is generated. Since the difference from the speed signal becomes large, it is possible to obtain a servo motor control device with an overload detection section that can easily detect overload of the servo motor without being affected by the magnitude of the current flowing through the servo motor. This is what I did.

[Embodiments of the invention]

FIG. 1 is a block diagram of an embodiment of the present invention, and the difference from FIG. 4 is that an overload detection section 12 consisting of a subtraction section 10 and a comparison section 11 is provided. Here, subtraction part 1
0 is configured to input a deviation signal 6a and a speed signal 3a and output a signal 10a according to the difference between the two signals, and a comparator 11 compares the input signal 10a with a built-in variable setting value. In comparison, if the value of the signal 10a is greater than or equal to the set value, the overload detection signal 11a is output.

Next, the principle by which the signal 11a is output from the overload detection section 12 will be explained. Figure 2 (Al is the deviation signal 6 in Figure 1)
FIG. 3 is an explanatory diagram illustrating a temporal change between zero and a and a speed signal 3a. 1 and 2 (5) tζ, if at time T1 the positioning command signal 5 having the above-mentioned trapezoidal time curve begins to be input to the counter 4, then at this point the servo motor 1 has not started rotating due to its inertia, so the rotation signal from pulse encoder 2 is
2a is not output, so the counter 4 receives the command signal 5.
The number of pulses of the command signal 5 is stored in the counter, and as a result, the counter is equal to the number of pulses stored in the counter 4 (hereinafter, this number of pulses may be referred to as the number of accumulated pulses). 4 count content N
increases successively, and the deviation signal 6 increases in proportion to the increase in the number N.
The voltage at a increases. Eventually, at time T2, servo motor 1
begins to rotate, so the voltage of the speed signal 3a gradually rises, but around time T, the speed of the servo motor 1 is slower than the speed corresponding to the frequency of the pulses in the command signal 5, so the counter 4 receives more and more pulses. is accumulated, and as a result, the voltage of signal 6a further increases.

Therefore, the servo motor 1 is further accelerated by the speed control section 8. At time T following time T2, the frequency of the pulses in the command signal 5 becomes constant.

In other words, from time T onwards, the command signal 5 will command the servo motor 1 to rotate at a constant speed, but since the servo motor 1 is still being accelerated at this point, the degree of increase in the signal 6a becomes gradual, and eventually When the speed of the servo motor 1 reaches the above-mentioned constant rotational speed commanded by the command signal 5 at time T4, the voltage of the signal 6a also becomes a constant value X. Therefore, the voltage of the signal 3a also becomes equal to time T and thereafter to X.

At time T following time T4, the pulse frequency in the command signal 5 begins to decrease, and as a result, the servo motor 1 begins to be commanded to decelerate.At this point, the servo motor has not yet been decelerated, so the count content N of the counter 4 changes. Decreased,
Therefore, the voltage of the signal 6a decreases, and as a result, the servo motor tab is decelerated, so that the voltage of the signal 3a decreases behind the voltage of the signal 6a. Time T! From then on, the pulse frequency of the rotation signal 2a output from the pulse encoder is greater than the pulse frequency of the command signal 5, so the count content N eventually becomes zero at time T6, and as a result, the voltage of the signal 6a also decreases at time T. It becomes zero. Since the speed of the servo motor 1 becomes zero at time T, which is later than time T6, the voltage of the signal 3a also becomes zero at time T.

In FIG. 2 (5), the signals 6a and 3a change over time as described above, so the output signal 10a of the subtraction section in FIG. 1 becomes as shown in FIG. 2 (end). That is, the signal 10a has a positive waveform when the servo motor 1 is in an acceleration state, and has a negative waveform when the servo motor 1 is in a deceleration state.

Figure 2 (A), (Bl is the servo motor IE in Figure 1.
This is a case where no overload condition occurs, but if an overload condition occurs in the servo motor, the speed of the servo motor 1 will be extremely reduced compared to the speed commanded by the command signal 5, so in this case, the speed The voltage of the signal 3a changes as shown in the third section, and in this case, the pulse frequency of the rotation signal 2a also changes according to the signal 3af, so the number of accumulated pulses in the counter 4 temporarily increases. As a result, the change in pressure in the section ' of the signal 6a becomes upwardly convex as shown in the third section.

In FIG. 3 (5), Y, Z, and W represent states in which the speed of the motor 1 temporarily decreases due to an overload state occurring when the servo motor 1 accelerates, rotates at a constant speed, and decelerates, respectively. Illustrated. In FIG. 1, when an overload condition as shown in FIG. 3 (5) occurs in the servo motor 1, the output signal 10a of the subtraction section becomes as shown in FIG. 3 (5). R in FIG. 3(b) is the aforementioned setting value set in the comparison section 11 of FIG.
As shown in FIG. 1, the overload detection signal 11a is output when the value of the signal 10a is equal to or higher than R.

In FIG. 1, the subtraction section 10 and the comparison section 11 □
Since the servo motor 1 is configured as described above, the overload condition of the servo motor 1 can be known from the detection signal 11a. That is, 12 is an overload detection section that detects overload of the servo motor 1 based on the difference between the deviation signal 6a and the speed signal 3a, and 13 is each illustrated section other than the motor 1 provided with such a detection section 12. This is a servo motor control device consisting of: In FIG. 1, the overload detection section 12 is configured as described above, so as is clear from FIG. This is done almost unaffected by the level. Therefore, such an overload detection section 12
According to the above, even when the amount of overload is small, overload can be easily detected regardless of the magnitude of the speed commanded to the servo motor.

In the above-mentioned embodiment, the speed signal generator 3 outputs the speed signal 3a by inputting the rotation signal 2a, but in the present invention, the speed signal generator 3 is directly connected to the motor 1. The speed signal 3a may be configured to be output by a mechanism such as a generator.

〔Effect of the invention〕

As described above, the present invention includes a rotation detection section that outputs a rotation signal according to the rotation state of the servo motor, a speed signal generation section that outputs a speed signal according to the rotation speed of the servo motor, and a rotation detection section that outputs a rotation signal according to the rotation state of the servo motor. a deviation calculation section that receives a positioning command signal and a rotation signal and outputs a deviation signal according to the difference between the two signals; and a speed control section that controls the speed of the servo motor using the deviation signal as a set value and the speed signal as a feedback value. In the servo motor control device equipped with , an overload detection section is provided to detect overload of the servo motor based on the difference between the deviation signal and the speed signal. With this configuration, when the servo motor is overloaded Eζ, the speed of the motor slows down and the difference between the deviation signal and the speed signal increases, so that the servo motor flow is not affected by the magnitude of the current ( This has the effect of providing a servo motor control device with an overload detection section that can easily detect overload of the servo motor.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of one embodiment of the present invention, Fig. 2 (5), Fig. 3 (b), Fig. 3 (5), and Fig. 3 (B) are respectively
FIG. 4 is a diagram illustrating different states of output signals of important parts in the figure, and is a configuration diagram of a conventional servo motor control device. 1... Servo motor, 2a... Rotation signal, 3...
Speed signal generation section, 3a... Speed signal, 5... Positioning command signal, 6a... Deviation signal, 7... Deviation calculation section, 8... Speed control section, 9.13... Servo Motor control device, 12... overload detection section. ′@ 1 closed v, 2 flash 3 fig.

Claims (1)

[Claims] a rotation detection section that outputs a rotation signal according to the rotational state of the servo motor; a speed signal generation section that outputs a speed signal according to the rotation speed of the servo motor; and a positioning command signal for the servo motor and the rotation signal. a deviation calculation unit that receives the input signal and outputs a deviation signal according to the difference between the two signals, and a speed control unit that controls the speed of the servo motor by using the deviation signal as a set value and using the speed signal as a feedback value. A servo motor control device according to the present invention, further comprising an overload detection section that detects overload of the servo motor based on the difference between the deviation signal and the speed signal.