JP2021083219A - Regenerative discharge system - Google Patents

Abstract

To provide a regenerative discharge system for improving reliability of a circuit while reducing components required for applying a brake.SOLUTION: A regenerative discharge system 100 comprises: a motor M which drives a robot; an inverter circuit 101 which controls drive of the motor M; regenerative power processing means constituted of abnormality detection means 108 for detecting abnormal voltage rise of a power line due to regenerative power, a regenerative discharge resistor 106 for processing the regenerative power, and switching means 107 for controlling current flowing to the regenerative discharge resistor 106 by a command from the abnormality detection means 108; a diode 105 for regenerative discharge for applying current to a path from the power line to the regenerative discharge resistor 106 only in its direction; and a diode OR circuit 111 which constitutes each phase of motor wirings, in which output of the diode OR circuit 111 is connected between the diode 105 for regenerative discharge and the regenerative discharge resistor 106.SELECTED DRAWING: Figure 1

Description

The present invention relates to a regenerative discharge system, and more particularly to a regenerative discharge system that reduces deterioration of FETs (field effect transistors) and the like in a motor control circuit due to regenerative discharge.

In a conventional articulated robot, each arm is operated by receiving power from a control panel and rotating a motor attached to each shaft. In order to rotate these motors, an inverter circuit converts DC to three-phase AC or single-phase AC to supply power to the motor, or a switching circuit simply turns DC on and off to supply power to the motor. Is common.

In addition, in recent years, FETs using SiC (silicon carbide) are becoming mainstream as components of the above-mentioned inverter circuit and switching circuit.

Further, the FET using SiC is expected to have a smaller electric resistance at the time of conduction, a faster switching speed, and a significant reduction in loss of an inverter circuit, etc., as compared with a conventional FET using Si (silicon). ing.

When using such a motor, the problem is the processing of regenerative power. Regeneration is a phenomenon in which the motor acts as a generator and generates electric power from the motor toward the control panel when the robot is operated in a direction that follows gravity, or when the brake is applied to stop or decelerate the operation. The power generated at this time is called regenerative power.

If this regenerative power is small, the motor or control panel consumes power, but as the amount of regenerative power increases, the power consumption cannot catch up, the voltage of the power line rises, and each electron connected to the power line. Components are exposed to overvoltage, resulting in circuit failure that exceeds the component's permissible voltage. A technique for dealing with such a problem by reducing wiring is known.

As a technique for reducing wiring, for example, in Patent Document 1, when the voltage of the power line becomes larger than a certain threshold voltage due to the regenerative power, the regenerative power is passed through the regenerative resistance for discharging the regenerative power connected to the power line. A technique for suppressing a voltage rise and preventing an overvoltage by consuming electric power is disclosed. This is said to facilitate the construction of a regenerative discharge system for a plurality of intelligent motors.

When processing the regenerated power by the technique of Patent Document 1, the current due to the regenerated power is passed in the order of the motor, the inverter circuit (or switching circuit), the power line, and the regenerated resistor. At this time, the inverter circuit (or the inverter circuit (or the switching circuit)) is used. The number of circuit components is reduced by using the body diode existing in the FET of the switching circuit).

However, when the technique of Patent Document 1 is used, the body diode cannot be used for any FET, and a product manufactured on the premise of using the body diode must be used. If a forward current is continuously applied to this body diode, the body diode deteriorates and stacking defects increase, and the above-mentioned increase in electrical resistance and loss in the body diode increase. Therefore, in the worst case, the FET It will lead to the failure of. Further, even such a product is difficult to use in such a way that an excessive load is applied, and it is necessary to configure a circuit configuration so that the load is not applied as much as possible.

Therefore, as a circuit for stopping the motor, as disclosed in Patent Document 2, when the motor is desired to be stopped, the switching means is made conductive, and the electric power of each phase of the motor is supplied by an external brake resistor. By consuming, stopping the power supply to the motor and even eliminating the power remaining in the motor, the force to rotate the motor is eliminated, and the motor is stopped by the force of the magnet contained in the motor. There is a technology called direct braking that tries to do so.

Japanese Unexamined Patent Publication No. 6-15590 Japanese Unexamined Patent Publication No. 2014-161221

However, in the circuit for stopping the motor described in Patent Document 2, since it is necessary to connect a resistor and a switching means to each phase, there is a problem that the circuit configuration becomes complicated.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a regenerative discharge system that improves the reliability of a circuit while reducing the number of parts required for applying a brake.

In order to solve the above problems, the regenerative discharge system according to the present invention is
The motor that drives the robot and
A motor control circuit that controls the drive of the motor and
An abnormality detecting means for detecting an abnormal voltage rise of a power line due to regenerated power, a regenerative power absorbing means for processing the regenerated power, and a current flowing through the regenerated power absorbing means are controlled by a command from the abnormality detecting means. Regenerative power processing means composed of switching means and
A rectifying element that allows current to flow only in that direction from the power line to the path from the regenerative power absorbing means.
A diode OR circuit constituting each phase of the motor wiring is provided.
The output of the diode OR circuit is connected between the rectifying element and the regenerative power absorbing means.

According to the regenerative discharge system according to the present invention, it is possible to improve the reliability of the circuit while reducing the number of parts required for applying the brake. The effects described here are not necessarily limited, and may be any of the effects described in the present technology.

It is a block diagram which shows the structural example of the schematic circuit of the regenerative discharge system which concerns on 1st Embodiment of this invention. It is a block diagram for demonstrating the operation of the regenerative discharge system which concerns on 1st Embodiment of this invention. It is a block diagram which shows the structural example of the schematic circuit of the regenerative discharge system which concerns on 2nd Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments described below show an example of a typical embodiment of the present invention, and the scope of the present invention is not narrowly interpreted by this. In addition, any of the following configurations of each embodiment can be combined with the configurations of other embodiments.

<First Embodiment>
First, the regenerative discharge system according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a block diagram showing a configuration example of a schematic circuit of the regenerative discharge system 100 according to the first embodiment of the present invention. FIG. 2 is a block diagram for explaining the operation of the regenerative discharge system 100 according to the present embodiment. The regenerative discharge system 100 is a circuit system applicable to a robot or a robot control device.

As shown in FIG. 1, the regenerative discharge system 100 is, for example, an inverter which is a motor control circuit which is connected to a motor M for driving a robot or the like by a three-phase motor wiring and controls the drive of the motor M. A circuit 101, a bridge circuit 102 connected in series to the inverter circuit 101, and an AC power supply 103 connected to the bridge circuit 102 by a power line are provided. Further, the regenerative discharge system 100 includes a backflow prevention diode 104 in which a capacitor C is connected in parallel between the inverter circuit 101 and the bridge circuit 102 and is connected in series between the bridge circuit 102 and the capacitor C.

Further, the regenerative discharge system 100 includes a regenerative discharge diode 105, which is a rectifying element, between the inverter circuit 101 and the capacitor C, which is connected in parallel to the inverter circuit 101 and the bridge circuit 102, and a regenerative discharge resistor 106. The switching means 107 and the abnormality detecting means 108 are provided. The regenerative discharge diode 105 causes a current to flow only in that direction from the power line to the path from the power line to the regenerative discharge resistor 106, which is a regenerative power absorbing means. The regenerative discharge diode 105, the regenerative discharge resistor 106, and the switching means 107 are connected in series to each other, and the output of the abnormality detecting means 108 is connected to the switching means 107. In the regenerative discharge system 100, the regenerative discharge resistor 106, the switching means 107, and the abnormality detecting means 108 constitute a regenerative power processing means for processing the generated regenerative power.

Further, the inverter circuit 101 has a body diode 109 of the FET, and the bridge circuit 102 has a diode 110 for the bridge circuit. Further, the regenerative discharge system 100 includes a diode OR circuit 111 connected to the inverter circuit 101. The diode OR circuit 111 has three braking diodes 112, 113, 114 connected in parallel, which form each phase of the motor wiring. The anode side, which is the input side of the brake diodes 112, 113, 114, is connected in parallel between the inverter circuit 101 and the motor M, and the cathode side, which is the output side, is the cathode side of the regenerative discharge diode 105 and the regenerative discharge resistor 106. Is connected between. The number of brake diodes included in the regenerative discharge system of the present invention is not limited to this embodiment.

The backflow prevention diode 104 limits the direction so that the current flows only in that direction in the path from the power line to the regenerative discharge resistor 106. The abnormality detecting means 108 detects an abnormal voltage rise of the power line due to the regenerative power. The regenerative discharge resistor 106 is a means for absorbing the regenerative electric power, and the switching means 107 controls the current flowing through the regenerative discharge resistor 106 by commands from the regenerative discharge resistor 106 and the abnormality detecting means 108.

Here, each of the above diodes may have a rectifying action so that a current flows only in a certain direction, and the method and material for realizing the diode are not particularly limited. However, it is necessary to select one in which the forward voltage of the brake diodes 112, 113, 114 is smaller than the sum of the forward voltage of the regenerative discharge diode 105 and the forward voltage of the body diode 109 in the inverter circuit 101. is there. More preferably, it is desirable to select one in which the forward voltage of the brake diodes 112, 113, 114 is smaller than the forward voltage of the body diode 109.

Here, the abnormality detecting means 108 detects an abnormality before the component connected to the motor wiring or the power line becomes an overvoltage due to a voltage rise due to the regenerative power, and instructs the switching means 107 to process the regenerative power. Anything that can be sent is sufficient, and the method of realizing it is not particularly limited.

For example, the regenerative discharge system 100 includes a voltage measuring means for measuring the voltage of the power line or the motor wiring in order to detect the overvoltage, and determines in advance that the voltage value obtained by the voltage detecting means is abnormal. The circuit may be a circuit that compares with the threshold voltage set for the purpose and sends a command to the switching means 107 if the threshold voltage is exceeded.

Alternatively, in order to detect the current flowing back from the motor resulting from the occurrence of the overvoltage, a current detecting means for measuring the current flowing through the power line or the motor wiring is arranged, and the current value obtained by the current detecting means and the current value obtained in advance are arranged in advance. A circuit may be used in which a command is sent if the threshold current is exceeded by comparing with the threshold current set for determining an abnormality. However, when the above current detecting means is used, it is highly likely that a component failure has already occurred at the time when the overcurrent is flowing, so it is desirable to use the voltage detecting means.

However, when the current detecting means is used, it is highly likely that a component failure has already occurred at the time when the overcurrent is flowing, so it is desirable to use the voltage detecting means. The regenerative discharge resistor 106 may be any as long as it can pass a current and consume electric power, and the method for realizing the regenerative discharge resistor 106 is not particularly limited.

Next, an example of the operation of the regenerative discharge system 100 according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 2 is a block diagram for explaining the operation of the regenerative discharge system 100 according to the present embodiment.

In the normal state, as shown in FIG. 1, since the abnormality detecting means 108 does not detect the overvoltage, the switching means 107 is in the non-conducting state. At this time, the regenerative discharge system 100 does not operate at all. However, when regenerative power is generated due to the motor M stopping or decelerating, the voltage of the power line rises, and the voltage becomes equal to or higher than the threshold voltage, the abnormality detecting means 108 detects the overvoltage, as shown in FIG. The switching means 107 becomes conductive, a current flows through the regenerative discharge resistor 106, and the regenerative power is consumed to suppress the voltage rise.

As shown in FIG. 2, the assumed paths of the current flowing out from the motor M are two, the path 1 shown by the alternate long and short dash line passing through the inverter circuit 101 and the path 2 shown by the chain line passing through the diode OR circuit 111. There are two routes.

Here, in order to simplify the description of each of the above paths, the one-phase brake diode 112 among the three-phase brake diodes 112, 113, and 114 in the diode OR circuit 111 will be focused on.

First, in the one-point chain line path 1, power is consumed from the motor M through the FET and the body diode in the inverter circuit 101 and through the regenerative discharge resistor 106.

Next, in the chain line path 2, power is consumed from the motor M through the brake diode 112 and the regenerative discharge resistor 106.

Here, assuming that the forward voltage of each diode of the regenerative discharge system 100 is the same, the one-point chain wire path 1 has a voltage drop due to the two diodes of the body diode 109 and the regenerative discharge diode 105, and the chain wire path. In No. 2, since a voltage drop occurs due to one braking diode 112, current is less likely to flow in the path 1 than in the path 2.

For example, assuming that each diode of the regenerative discharge system 100 is an ideal diode, the voltage of the motor M is 100 V, and the resistance value of the regenerative discharge resistor 106 is 10 Ω, the one-point chain line path 1 is about 90 nA, and the chain line path 2 is about about 90 nA. A current of 910 mA will flow.

From the above results, according to the regenerative discharge system 100 according to the present embodiment, most of the regenerative power generated by the motor M flows from the chain wire path 2 to the regenerative discharge resistor 106 and passes through the body diode 109 in the inverter circuit 101. Since the current is small, deterioration of the FET in the inverter circuit 101 can be reduced.

According to the regenerative discharge system 100 according to the present embodiment, the number of system components is reduced by sharing the regenerative discharge resistor 106 and the diode OR circuit 111, and further, when the regenerative power is generated by the motor M, the regenerative power is regenerated. Since the electric power flows into the regenerative discharge resistor 106 via the diode OR circuit 111, the current passing through the body diode 109 of the FET in the inverter circuit 101 is reduced, so that the reliability of the circuit can be improved.

<Second Embodiment>
Next, the regenerative discharge system according to the second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a block diagram showing a configuration example of a schematic circuit of the regenerative discharge system 200 according to the present embodiment. The regenerative discharge system 200 according to the present embodiment is different from the regenerative discharge system 100 according to the first embodiment in that a logical sum means is provided between the abnormality detecting means 108 and the switching means 107.

The regenerative discharge system 200 according to the present embodiment includes the brake command means 201 and the OR means 202 in addition to the same configuration as the regenerative discharge system 100 according to the first embodiment. The OR means 202 is provided between the abnormality detecting means 108 and the switching means 107. The abnormality detecting means 108 and the output side of the brake commanding means 201 are connected to the input side of the OR means 202, and the switching means 107 is connected to the output side of the OR means 202. The switching means 107 is controlled by the output of the OR means 202.

In the regenerative discharge system 200, the logical sum means 202 controls the switching means 107 by the logical sum of the abnormality detection command value of the abnormality detection means 108 and the brake command value of the brake command means 201, and the output value thereof.

Here, even in a configuration such as the regenerative discharge system 100 according to the first embodiment, when the brake is applied, if the power is cut off, the power supplied to the motor M is exhausted, the motor M is stopped, and the brake is stopped. The regenerative power at that time causes a voltage rise, and the regenerative discharge system 100 operates, so that the motor M can be braked.

However, in such a method, as shown in FIG. 1, the state in which the motor M does not stop for a short time can continue even if the power is cut off by the electric charge accumulated in the capacitor C in the regenerative discharge system 100. If the power in the motor M is exhausted and the voltage of the power line is also equal to or lower than the threshold voltage, the switching means 107 is in a non-conducting state and the regenerative discharge resistance 106 does not consume power, so that the braking may be delayed. ..

To solve such a problem, as shown in FIG. 3, a logical sum is obtained between the abnormality detection command value of the abnormality detection means 108 and the brake command value of the brake command means 201, and a regenerative discharge is received by receiving either signal. The current may flow through the resistor 106.

Next, an example of the operation of stopping the motor M by the regenerative discharge system 200 according to the present embodiment will be described with reference to FIG.

Similar to the first embodiment, in the normal state, the switching means 107 is in the non-conducting state because the abnormality detecting means 108 has not detected the overvoltage. At this time, the regenerative discharge system 200 does not operate at all. However, when regenerative power is generated due to the motor M stopping or decelerating, the voltage of the power line rises, and the voltage exceeds the threshold voltage, the abnormality detecting means 108 detects the overvoltage, and the switching means 107 becomes conductive. , A current flows through the regenerative discharge resistor 106 and consumes the regenerative power to suppress the voltage rise.

First, an external controller (not shown) outputs an output stop command value to the inverter circuit 101, which is a motor control circuit for decelerating or stopping the motor M, and outputs a brake command value to the brake command means 201.

Next, the inverter circuit 101 that receives the output stop command value output from the external controller stops the output to the motor M.

Further, the brake command means 201 that receives the brake command value output from the external controller starts braking the motor M, and the motor M starts decelerating.

Then, the OR means 202 receives the abnormality detection command value output from the abnormality detection means 108 and the brake command value output from the brake command means 201. The logical sum means 202 takes the logical sum of the received abnormality detection command value and the brake command value, and outputs a switch ON command to the switching means 107.

Then, the switching means 107 is turned on, and the regenerative discharge resistor 106 starts discharging the electric power accumulated in the motor M.

On the other hand, regenerative power is generated by decelerating the motor M. The generated regenerative power of the motor M is discharged by the regenerative discharge resistor 106 through the diode OR circuit 111.

Then, the motor M is stopped by the brake and the regenerative power and the discharge of the power accumulated in the motor M.

Based on the above, the regenerative discharge system 200 according to the present embodiment reduces the number of parts required for braking and further reduces the current flowing through the body diode 109 of the FET, similarly to the regenerative discharge system 100 according to the first embodiment. The reliability of the circuit can be improved by reducing the amount.

Here, there are two conditions for generating the regenerative power of the motor M: deceleration or acceleration in a direction following gravity, and applying the brake corresponds to deceleration. That is, since regenerative power is generated when the brake is applied, if the regenerative discharge system 200 is operated when the brake command is output without waiting for the abnormality detecting means 108 to detect the overvoltage, the abnormality detecting means It is possible to prevent the generation of the current flowing through the body diode by the time the 108 detects the overvoltage.

Further, according to the regenerative discharge system 200, the electric power of the motor M can be consumed by the regenerative discharge resistor 106, so that the effect of so-called direct braking can be realized.

The present invention is built in an industrial robot arm to reduce deterioration of FET in an inverter circuit due to regenerative discharge, and has industrial applicability.

100, 200 Regenerative discharge system 101 Inverter circuit 102 Bridge circuit 103 AC power supply 104 Backflow prevention diode 105 Regenerative discharge diode 106 Regenerative discharge resistance 107 Switching means 108 Abnormality detection means 109 Body diode 110 Bridge circuit diode 111 Diode OR circuit 112, 113 , 114 Brake diode 201 Brake command means 202 Logical sum means C capacitor M motor

Claims (2)

The motor that drives the robot and
A motor control circuit that controls the drive of the motor and
Abnormality detecting means for detecting an abnormal voltage rise of a power line due to regenerated power, regenerative power absorbing means for absorbing the regenerated power, and switching for controlling the current flowing through the regenerated power absorbing means by a command from the abnormality detecting means. Regenerative power processing means composed of means,
A rectifying element that allows current to flow only in that direction from the power line to the path from the regenerative power absorbing means.
A diode OR circuit constituting each phase of the motor wiring is provided.
A regenerative discharge system in which the output of the diode OR circuit is connected between the rectifying element and the regenerative power absorbing means. Further provided with a logical sum means for taking the logical sum of the abnormality detection command value and the brake command value of the abnormality detection means.
The regenerative discharge system according to claim 1, wherein the switching means is controlled by the output of the OR means.

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