JP2002354860A - Motor controller provided with function of preventing damage to mechanical apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that, if a mechanical apparatus driven by a motor is brought into abnormal operating state due to malfunction of the apparatus, mixing of foreign matter, or the like, load torque is increased and thus driving torque is increased for continuing operation; and this phenomenon induces damage to the malfunctioning part of the apparatus or damage to the mechanical apparatus due to the mixed foreign matter. SOLUTION: The load torque of the mechanical apparatus driven by the motor is computed by a motor controller, and the differentiated value of the load torque is calculated by a differentiator built in the motor controller. The calculated differentiated value of the load torque is compared with a specified abnormal level for differentiated value of load torque as needed. If abnormal increase in load torque due to malfunction of the mechanical apparatus or the like is detected, that is taken as an anomaly in the mechanical apparatus and the motor controller is operated so as to suppress increase in torque command for driving the mechanical apparatus. Thus, damage to the mechanical apparatus is prevented from occurring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a mechanical device using an electric motor so that the electric motor continues to operate in an unusual operating state due to abnormal operation of the mechanical device or foreign matter contamination. The present invention relates to an electric motor control device having a function of generating a drive torque larger than usual by operating it, and having a function of preventing or minimizing damage to a mechanical device due to damage to an abnormally operating portion of the mechanical device or foreign matter mixed therein.

[0002]

2. Description of the Related Art In recent years, continuous automatic operation of a machine driven by an electric motor, such as a transport machine, a printing machine, and various industrial machines, has been advanced in order to improve work efficiency by using unmanned machines. In general, such an unmanned mechanical device is configured to detect the occurrence of an abnormality that hinders operation and automatically stop the operation.
For example, when a movable part or the like in a mechanical device acts to obstruct the operation of the mechanical device due to an abnormal operation, or when a locking phenomenon occurs in which a foreign substance is mixed into a rotation driving portion of the mechanical device and the rotation is temporarily stopped. Meanwhile, the electric motor driving the mechanical device generates a larger driving torque than in the normal state in order to continue the operation, and there is a possibility that the abnormal operation portion of the mechanical device may be damaged before continuing the operation. In order to prevent or minimize such mechanical device damage, the conventional method calculates the load torque for the motor to drive the mechanical device based on the current detection value, voltage detection value and motor rotation speed of the motor. Monitoring that the load torque calculated by the calculation abnormally increases, and when the abnormally increased load torque reaches a predetermined abnormal level, stops the operation of the motor or rapidly reduces the rotation speed of the motor. It is configured as follows. Also, the load torque reaches an abnormal level, and the drive torque generated by the electric motor is reduced before the protection operation is started, and a predetermined protection operation start level is set to prepare for the protection operation. In some cases.

[0003]

However, in the conventional mechanical device damage prevention system described above, the load torque or the rotation of the motor which is calculated based on the current detection value and the voltage detection value of the motor and the rotation speed of the motor. A torque command generated by proportionally integrating the speed deviation between the output of the number detection means and the speed command value of the electric motor reaches a predetermined abnormal level set in advance to activate the device damage protection. It is configured. The driving torque output by the motor to drive the mechanical device is based on a torque command generated by a torque command generator for proportionally controlling the deviation between the actual rotation speed of the motor and the rotation speed command value. It is obtained by inputting to the power control unit to be controlled. If an abnormality occurs in the mechanical device, a deviation occurs between the actual rotation speed of the electric motor and the rotation speed command value, and the generated deviation is converted into a torque command by the proportional integral control of the torque command generation unit. However, in a motor control system in which a speed deviation is converted into a torque command using proportional integral control, in a device configured to compare a machine torque damage prevention operation with a load torque calculation value and a predetermined abnormality detection level. However, a response delay of the proportional integral control always occurs until the load torque calculation value reaches the abnormality detection level. Due to the response delay, the machine is operated in an abnormal state until the abnormal operation of the mechanical device or the abnormal operation due to foreign matter is detected, and the mechanical device may be damaged before the protection is activated. In some cases, prevention does not work well.

Another problem will be specifically described with reference to a timing chart shown in FIG. FIG.
In the graph, N is the locus of the rotational speed according to the time, and τ is the locus of the load torque according to the time. At time t0, when an abnormality occurs in the mechanical device and the load torque sharply increases, the rotation speed of the electric motor falls below the rotation speed command value N0. When the rotation speed decreases, the torque command generator acts to reduce the speed deviation to zero, and the torque generated by the electric motor also sharply increases. At this time, the torque generated by the electric motor increases until the speed deviation becomes zero, and when the speed deviation reaches zero, a driving torque capable of maintaining the state where the speed deviation is zero is generated. Eventually, it becomes the same as the load torque τe at time t2. Here, if the load torque τe is equal to or higher than the abnormality detection level, the motor control device operates to immediately stop the operation of the motor. FIG.
(B) At time t1, the rotation speed changes from a decrease to an increase, and the rotation speed is recovered so as to match the rotation speed command. However, during the period from time t1 to t2, the operation is performed in spite of the abnormal operation period. Is a region where a large drive torque is generated and the mechanical device is forcibly driven even if the motor does not reach the abnormality detection level. The driving torque generated by the electric motor during the period from time t1 to time t2 is originally unnecessary torque as the torque for driving the mechanical device, and a load is applied to a portion that hinders the operation of the mechanical device due to abnormal operation. Equivalent to torque. Therefore, even if the mechanical device is not immediately damaged, there may be a case where abrasion of a load-applied portion or metal fatigue is promoted, resulting in damage.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to improve the operation delay of a mechanical device damage prevention function due to a response delay until a load torque calculation value reaches an abnormal detection level. It is another object of the present invention to provide a motor control device having a mechanical device damage prevention function capable of operating a mechanical device reliably and without malfunction.

[0006]

In order to achieve the above object, a means for detecting the number of rotations of a motor for driving a mechanical device according to claim 1 is provided. Is obtained, and the obtained deviation is converted into a torque command of the electric motor by proportional-integral control.The obtained torque command is inputted to a power control unit for controlling the power supply to the electric motor. In a motor control device configured to obtain a load drive torque and including a load torque calculation unit that calculates a load torque of the motor from a current and a voltage supplied to the motor and a rotation speed of the motor, an output of the load torque calculation unit is provided. And a comparator that compares the output of the differentiator with a predetermined value set in advance.If the output of the differentiator exceeds a predetermined value, it is determined that the mechanical device is in an abnormal operation state. Outputs from the comparator a signal to the torque command increases stop, configured to stop the rise of the torque command. The acceleration torque at the time of accelerating the mechanical device based on the total inertia moment obtained by adding the numerical value obtained by converting the inertia moment of the mechanical device to the electric motor shaft and the electric motor inertia moment and the acceleration time ratio set in the electric motor control device. An upper limit value is obtained, and a numerical value obtained by adding a margin to the obtained upper limit value is set as a predetermined value to be compared with the differential value of the output of the load torque calculation unit.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a motor control device having a function to prevent mechanical device damage according to the present invention. FIGS. 2A and 2B are operation timing diagrams for preventing mechanical device damage, and FIG. Block diagram of a torque command generator,
FIG. 4 is a block diagram of a circuit for stopping the increase of the torque command when the mechanical device damage prevention function according to the present invention is operated.

[0008] The apparatus of the present invention is configured as shown in FIG. That is, in the first embodiment, the electric motor 1 is coupled to the mechanical device 13 to drive the mechanical device 13 serving as a load on the electric motor 1. Rotation speed detector 2
Is directly attached to the motor 1 so as to detect the rotation speed of the motor 1. The torque command generator 5 obtains a deviation from the output of the rotation speed detector 2 and the output of the rotation speed command setting device 11, and generates a torque command by performing a proportional integral operation on the obtained deviation. In the torque command generator 5, as shown in FIG.
The output of the rotational speed detector 2 and the output of the rotational speed command setter 11 are input to a subtractor 51 to determine a deviation Nerr. The obtained deviation Nerr is input to a proportional-plus-integral calculator 52, which calculates a product of the deviation Nerr and a proportional gain Kp.
3. Integrator 54 for integrating the error Nerr with time constant Ki over time.
Enter The proportional-integral calculator 52 acts to generate a torque command so that the deviation Nerr between the output of the rotation speed detector 2 and the output of the speed command setting device 11 becomes zero. The sum of the outputs of the devices 54 is output from the torque command generator 5 and input to the power controller 6 that controls the power supply to the electric motor 1. Power controller 6
Then, the electric power is controlled so that the electric motor 1 outputs the driving torque corresponding to the input torque command.

The load torque calculator 7 receives the detected values of the current and the voltage supplied to the motor 1 from the current detector 3 and the voltage detector 4 and calculates the load torque from the rotation speed of the motor 1. The calculated load torque value is calculated by the differentiator 8.
And the load torque differential value can be regarded as an instantaneous change amount of the load torque. The larger the numerical value of the instantaneous change amount of the load torque is, the more suddenly the load torque change
Since the load applied to the mechanical device is increased, the comparator 9 and the torque command rise / stop circuit 10 are configured so that the instantaneous change amount of the load torque can be limited to a predetermined value. The comparator 9 compares the instantaneous change amount of the load torque with the abnormal level set value preset in the torque differential value abnormal level setting unit 12, and when the instantaneous change amount of the load torque exceeds the abnormal level, the mechanical device malfunctions. And outputs an abnormal signal to the torque command rise stop circuit 10. Regarding the set amount of the torque differential value abnormal level setter 12,
Set the damage level calculated from the mechanical and structural rigidity of each part of the machine. Next, as shown in FIG. 4, when the torque command rise stop circuit 10 receives the mechanical device abnormal operation signal, the switch 101 is switched to the point B to operate so that the torque command does not further rise, and the torque command generator 5 The output is prevented from being directly output to the power controller 6. Figure 4
In the block diagram of the torque command rise stop circuit, a configuration example for holding the torque command is shown. However, in the method of the present invention, the drive torque command of the electric motor 1 is stopped from rising when the load torque differential value reaches an abnormal level. Thus, even if the operation of the electric motor control device is continued, the output torque of the electric motor 1 does not increase to a level that causes mechanical damage, and the mechanical device is not damaged.

The operation of each unit described above will be described with reference to the timing chart of FIG. In the timing chart, N is the locus of the rotation speed of the electric motor 1 according to time, τ is the locus of the load torque calculation value at time, and Δτ is the locus of the load torque differential value at time. At time t0, when an abnormality occurs in the mechanical device and the load torque sharply increases, the rotation speed of the electric motor 1 becomes lower than the rotation speed command value N0. When the rotation speed decreases, the torque command generator 5 acts to make the speed deviation zero, and the torque generated by the electric motor 1 also sharply increases. When the load torque increases from time t0, the differentiator 8 outputs the signal as Δτ. The differentiator 8 indicates the instantaneous change amount of the load torque calculation value, and an output appears when the load torque increases as shown in the timing chart. That is, the differentiator
By monitoring the output of 8, it is possible to easily detect even small changes occurring in the mechanical device. Further, the load torque continues to increase, and at time t3, the output of the differentiator 8 is compared with the predetermined torque differential value abnormal level ΔτL by the comparator 9, and as a result, the output of the differentiator 8 becomes the torque differential value abnormal level ΔτL Is exceeded, the comparator 9 outputs an abnormal signal to the torque command rise stop circuit 10. When an abnormal operation signal is input from the comparator 9, the torque command increase stop circuit 10 moves the switch 101 to the point B side to operate to stop the increase of the torque command.

When the operation in the abnormal state is continued, the rotation speed of the electric motor 1 becomes zero at time t4. This is because, at time t3, the torque command value was operated so as to stop increasing at τB, and the motor 1 was unable to output a torque for driving an increase in load torque due to an abnormality in the mechanical device. . At time t4, the rotation of the motor 1 becomes zero, and when the operation time at the zero rotation reaches time t5 at which a predetermined time has passed, the motor control device 20 automatically stops the operation. At time t5, the motor control device 2
0, the output of the abnormal signal of the comparator 9 is stopped, and the switch 10 of the torque command rise stop circuit 10 is stopped.
1 is returned to the normal point A side, and after the trouble that caused the abnormal operation of the mechanical device is removed, the operation can be restarted immediately.

In the second aspect, the load torque calculator 7
For a predetermined value to be compared with a numerical value obtained by differentiating the output, a numerical value J obtained by converting the moment of inertia Jc of the mechanical device 13 into a motor shaft.
The acceleration torque at the time of acceleration of the mechanical device 13 is determined from the total inertia moment J obtained by adding the mc and the inertia moment Jm of the electric motor 1 and the acceleration time ratio ΔN set when the electric motor 1 is increased. Is obtained, and a numerical value obtained by adding a control margin to the obtained maximum value is set in the torque differential value abnormal level setting unit 12. Based on the acceleration time ratio ΔN and the total moment of inertia Jm, the load torque during acceleration is given by the following equation (1). J × ΔN = τm + τL (1) where τm is the drive torque of the electric motor 1 and τL is the load torque of the mechanical device. In the motor control device 20,
Since the acceleration time ratio ΔN is set before the driving operation, the acceleration time does not suddenly change during the driving operation. Therefore, if the total moment of inertia J and the acceleration time ratio ΔN are known in advance, the torque increase ratio required for accelerating the mechanical device 13 in the shortest time is the maximum value Δτmax of the load torque differential value of the mechanical device 13. Therefore, the torque differential value abnormal level setter 12 is configured to set a numerical value obtained by adding a control margin to the Δτmax. As a result, even when the acceleration time ratio ΔN of the mechanical device 13 is changed before the driving operation, the torque differential value abnormal level is automatically set in the torque differential value abnormal level setting unit 12 by the motor control device 20 to prevent damage to the mechanical device. The level can be automatically corrected.

[0013]

As described above, according to the present invention, the torque command of the motor is calculated from the difference between the rotation speed of the motor driving the mechanical device and the rotation speed command value of the motor, and the load driving torque is calculated by the motor control unit. To the motor control device that calculates the load torque from the current and voltage supplied to the motor and the number of revolutions of the motor, and compares the output of the differentiator that temporally differentiates the calculated value of the load torque with a predetermined value, When the differential value of the load torque calculation value exceeds a predetermined value, it is determined that the mechanical device is in an abnormal operation state, and the increase in the torque command output is stopped. With this configuration, it is possible to monitor the abnormal rise of the load torque without delay in response from the point in time when the lock phenomenon occurs due to the operation abnormality or the entry of foreign matter into the mechanical device. It is possible to suppress an increase in the torque command before the arrival, and to prevent damage to the mechanical device, which is extremely useful in practical use.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is an operation timing chart of the present invention.

FIG. 3 is a block diagram of a torque command generator according to the present invention.

FIG. 4 is a block diagram of a torque command rise stop circuit according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Electric motor 2 ... Rotation speed detector 3 ... Current detector 4 ... Voltage detector 5 ... Torque command generator 6 ... Electric power controller 7 ... Load torque Computing unit 8: Differentiator 9: Comparator 10: Torque command rise / stop circuit 11: Rotational speed command setting device 12: Torque differential value abnormal level setting device 13: Mechanical device 20 ... Electric motor control devices

Claims (2)

[Claims] An electric motor for driving a mechanical device; a rotational speed detecting means for detecting a rotational speed of the electric motor; a current detecting means and a voltage detecting means for detecting a current and a voltage supplied to the electric motor; A torque command generator for generating a torque command for the electric motor by calculating a deviation between the output of the number detection means and the rotational speed command value of the electric motor, and performing a proportional integral control of the deviation; An electric motor comprising: a power control unit for controlling power supply to the electric motor; and a load torque calculating unit for calculating a load torque of the electric motor based on an output of the current detecting unit, an output of the voltage detecting unit, and an output of the rotation speed detecting unit. A differentiator for differentiating the output of the load torque calculator over time;
A comparator for comparing the output of the differentiator with a predetermined value of a torque differential value abnormality level set in advance; and a mechanical device abnormality signal output from the comparator being input to increase the output of the torque command generator. A torque command increase / stop circuit for stopping the motor, a decrease in the motor rotation speed due to an abnormal operation of a mechanical device or the like is detected by the rotation speed detector, and the torque command is set so that the motor rotation speed follows the rotation speed command value. When the generator is operated, a load torque differential value indicating the slope of the load torque is obtained from the differentiator, and the load torque differential value is compared with a predetermined value of the torque differential value abnormal level by the comparator. When the differential value exceeds a predetermined value of the torque differential value abnormality level, the torque command rise / stop circuit is configured to input a mechanical device abnormality signal from the comparator. A motor control device that has a function to prevent installation damage. A predetermined value for comparison with an output of a differentiator for time-differentiating an output of the load torque calculating unit; and a total inertia moment of a motor inertia moment and a numerical value obtained by converting an inertia moment of a mechanical device into a motor shaft; 2. The mechanical device damage prevention function according to claim 1, wherein an upper limit value of the acceleration torque at the time of acceleration of the mechanical device is obtained from an acceleration time ratio set in the electric motor control device, and a value obtained by adding a margin to the upper limit value is obtained. Motor control device.