JPH04265682A - Servo amplifier with upper limit rotation speed limit function - Google Patents

Abstract

PURPOSE:To suppress rotational speed below a predetermined level even upon occurrence of transient missing or pulsation of load torque by inputting a correction signal when the rotational signal exceeds a set value. CONSTITUTION:Upon occurrence of transient missing or pulsation in the load torque of a servo motor, a load current signal Ir decreases abruptly and the input difference of an ACR 2 increases abruptly. When the rotational speed of the servo motor increases and a rotational speed signal Nr exceeds an upper limit signal Nu, an upper limit rotational speed limiting circuit 1 outputs a signal Nc according to the polarity of the signal Nr thus compensating for the abrupt decrease of the signal Ir quickly. Consequently, the input difference of the ACR 2 is recovered to a steady value, i.e., zero, or thereabout and thereby excessive increase of the rotational speed of the servo motor can be prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a servo amplifier for controlling a servo motor which has a function to limit an excessive increase in rotational speed of the servo motor under torque control in response to a temporary loss of load torque or the like.

0002

2. Description of the Related Art Conventional servo amplifiers for controlling servo motor drives of this type have been designed to prevent transient effects in the load torque of the servo motor when the servo amplifier performs torque control, such as tension control in winding control. If a loss or the like occurs and the rotational speed becomes excessive, an overspeed detection circuit added to the servo amplifier detects the overspeed state and functions to stop the operation of the servo motor and generate an alarm. something is known.

0003

[Problems to be Solved by the Invention] However, in the conventional servo amplifier as described above, when the servo amplifier performs torque control, a temporary loss of torque or similar torque pulsation occurs in the load of the servo motor to be controlled. If this occurs and the rotational speed abnormally increases, the operation of the servo motor must be stopped each time, which is extremely inconvenient in terms of load system operation, and the type of load that can be applied must be restricted. In view of this, the present invention provides a servo motor with an upper limit rotational speed limiting function that can suppress an abnormal increase in the rotational speed of the servomotor and continue its operation even in the torque control of a servomotor that drives a load with torque fluctuations as described above. The purpose is to provide amplifiers.

0004

[Means for Solving the Problems] In order to achieve the above object, a servo amplifier with an upper limit rotational speed limiting function of the present invention has the following features:
Regarding a torque control circuit in a servo amplifier of a servo motor drive control system, there is provided a rotation speed setting device for setting an upper limit value of the rotation speed of the motor, and a rotation speed upper limit setting value set by the setting device and the detected actual rotation speed value. and a comparator which receives as an input and outputs a DC voltage signal of a predetermined value when the actual value becomes larger than the upper limit set value, and has an appropriate dead band in the comparison calculation of both inputs, and the torque control The output signal of the comparator is added to the deviation signal between the torque setting value at the input section of the circuit and the actual load current value of the motor, which is a feedback signal corresponding to the setting value, with the polarity of increasing feedback signal amount. shall be taken as a thing.

[0005]

[Operation] In general, torque control of a servo motor is performed by using the required torque setting value as a target value, using the actual value of the load current that has a specific relationship with the output torque of the servo motor as a feedback signal, and making the deviation between the two signals zero. This is done by configuring a negative feedback current control system. Therefore, if the load torque of the servo motor under torque control is lost or significantly reduced, the required load current will be reduced accordingly, and the deviation will increase rapidly, commanding a large increase in the output torque of the servo motor. However, as described above, since the load torque is being lost, the rotational speed of the servo motor increases significantly.

[0006] Now, if the load torque loss described above is temporary or pulsating, it is necessary to control the signal There is no need to immediately reduce the deviation between signals to zero and maintain the zero state, but instead, it is possible to send a compensation signal of sufficient magnitude to bring the deviation between signals within a required value without erroneous direction.
Therefore, it is sufficient to immediately apply it in the same direction as the feedback signal of the load current. In accordance with the above, the present invention provides a comparator for detecting a state in which the actual value of the rotational speed is larger than its upper limit set value, and adjusts the stepped DC voltage signal outputted from the comparator to an appropriate voltage value. Afterwards, a force is applied to the deviation in the direction of suppressing its increase, suppressing the deviation within a predetermined value, and preventing the rotational speed from increasing excessively as described above. Incidentally, in order to avoid rapid repetitive operations in the above-mentioned comparison calculation of both speed signals and to maintain smoothness of the above-mentioned compensation control, the comparator is provided with a dead zone of an appropriate width.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the circuit diagram shown in FIG. This figure shows an excerpt of the current regulator input signal synthesis section of the torque control circuit in a servo amplifier for forward/reverse variable speed drive of a servo motor, and each input signal in the synthesis section corresponds to the forward/reverse rotation of the servo motor. The polarity is changed depending on the direction and is given as a voltage signal. In FIG. 1, reference numeral 1 denotes an upper limit rotational speed limiting circuit, and a detection signal Nr of the actual rotational speed of the servomotor whose polarity is changed according to the forward and reverse rotational directions of the servomotor is used as an upper limit value setting signal for the rotational speed. When the current is larger than Nu, a stepped signal Nc of an appropriate magnitude is output as a compensation signal for suppressing the increase in rotational speed while the state continues, depending on the polarity of the signal Nr, and the DC constant an upper limit rotational speed setter VR that divides a voltage to obtain the predetermined signal Nu; an input/output signal polarity inversion amplification section consisting of an amplifier OP1 and resistors R1 and R2; and a buffer consisting of an amplifier OP11 and resistors R11 and R12. an amplification section, a first voltage comparison section made up of resistors R3, R4, R5, a capacitor C1, and an amplifier OP2; a second voltage comparison section made up of resistors R13, R14, R15, a capacitor C11, and an amplifier OP12; It consists of a diode D1 and a resistor R6, as well as two sets of output signal selection sections consisting of D11 and R16. Note that each of the two sets of voltage comparators has a dead zone of an appropriate width.

[0008] Next, the second ACR (current regulator) outputs a required value setting signal Tc for converting the output torque into a load current, which is proportional to the square of the primary load current of the servo motor, and the primary load current. It inputs the deviation from the actual value detection signal Ir, performs a control operation so as to make the deviation zero, and outputs a control signal Sc. Now, if a temporary loss or similar pulsation occurs in the load torque of the servo motor, the load current signal Ir will suddenly decrease, and therefore the AC
The R input deviation sharply increases from its steady state, but due to the loss of load torque as described above, the rotational speed of the servomotor results in a significant increase, and at this time, if the detection signal Nr of the rotational speed changes from its upper limit setting signal If it becomes larger than Nu, the signal Nc is output from the upper limit rotational speed limiting circuit 1 according to the polarity of the signal Nr as described above, rapidly compensating for the sudden decrease in the signal Ir, and reducing the input deviation of the ACR. The rotational speed of the servo motor is restored to a steady value of zero or around it, and an excessive increase in the rotational speed of the servo motor is suppressed. Such suppression control is not repeated rapidly near the signal Nu due to the dead zone of the two sets of voltage comparators in the limiting circuit 1, and ends when the load torque recovers.

[0009]

According to the present invention, regarding a torque control circuit in a servo amplifier of a servo motor drive control system, there is provided a rotation speed setting device for setting an upper limit value of the rotation speed of the motor, and a rotation speed upper limit setting by the setting device. and the detected actual rotational speed value are input, and when the actual value becomes larger than the upper limit set value, a DC voltage signal of a predetermined value is output, and an appropriate dead band is set in the comparison calculation of both inputs. and a comparator having an output signal of the comparator in response to a deviation signal between the torque setting value at the input section of the torque control circuit and the actual load current value of the motor serving as a feedback signal corresponding to the setting value. By adding the values according to the polarity of the feedback signal amount increase, even if there is a temporary loss in the load torque of the servo motor during torque control operation or a similar pulsation occurs, the increase in the rotation speed of the servo motor can be kept within a predetermined value. It is possible to continue the operation while suppressing the servo motor, and it is possible to improve the stability of the servo motor operation.

[Brief explanation of the drawing]

[Fig. 1] Circuit diagram showing an embodiment of the present invention

[Explanation of symbols]

1 Upper limit rotation speed limiting circuit 2 ACR (current regulator) C1, C11 Capacitor O
P1, OP11 Amplifier OP2, OP21 Amplifier R1 to R6 Resistor R11 to R16 Resistor

Claims (1)

[Claims] 1. A torque control circuit in a servo amplifier of a servo motor drive control system, comprising: a rotation speed setter for setting an upper limit value of the rotation speed of the motor; a comparator that receives an actual rotational speed value as an input, outputs a DC voltage signal of a predetermined value when the actual value becomes larger than the upper limit setting value, and has an appropriate dead zone in a comparison operation of both inputs. established,
The output signal of the comparator is set to have a polarity that increases the feedback signal amount in response to a deviation signal between the torque setting value at the input section of the torque control circuit and the actual load current value of the motor, which is a feedback signal corresponding to the setting value. A servo amplifier with an upper limit rotation speed limiting function.