JP2012152008A - Robot controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a robot controller capable of inhibiting heat evolution rapidly in motor regenerative operation for driving the motor in an optimum condition.SOLUTION: In a robot controller, during a motor deceleration period, a control part 13 allows a charging of a capacitor 28 to collect a regenerative electric power, and allows a regenerative resistor 32 to collect the regenerative electric power by closing a second switch 33, when the charging voltage of the capacitor 28 reaches the prescribed upper limit. The control part 13 allows the capacitor to reduce the charge voltage by repeatedly opening and closing a first switch 31 in a constant speed period immediately before the motor deceleration. In the voltage drop period, based on the motor deceleration width in the motor deceleration period, the controller specifies a deceleration start voltage which is the capacitor charge voltage at the start of the deceleration, specifies a switching time width of a first switch 31, and reduces the capacitor 28 charge voltage to the voltage of starting the deceleration by controlling the opening/closing of the first switch 31.

Description

  The present invention relates to a robot controller that controls, for example, a motor provided in a movable part of an industrial robot.

  An AC servo motor provided in a movable part such as a joint part of an industrial robot realizes a desired operation by repeatedly performing acceleration control and deceleration control. In this case, various technologies have been proposed in which regenerative power is generated when the motor is decelerated and the regenerative power is recovered using a regenerative resistor. For example, in Patent Document 1, the switching element connected between the DC power supply lines via the regenerative resistor is turned on, and the regenerative power from the motor is bypassed to the DC power supply line side and controlled to be consumed by the regenerative resistor. Yes.

JP 2007-37301 A

  When the regenerative power from the motor is recovered by the regenerative resistor, heat is generated at the regenerative resistor. At this time, in an industrial robot, since the regenerative resistor is generally arranged in the robot controller, the robot controller includes heat generated from the regenerative resistor in addition to heat generated from electronic components such as a CPU. It will be. Here, since the robot controller is equipped with a heat radiating fan, etc., if the robot controller is installed in an environment where the temperature is not so high, heat generated by electronic components and regenerative resistors is exhausted outside the robot controller. It is possible to keep the temperature inside the robot controller at such a level that the electronic parts and the like can normally operate by circulating the air.

  However, since the environment in which the robot controller is installed is determined by the user who uses the robot, it cannot be denied that the robot controller is installed in an extremely high temperature environment in some cases. Under such an extremely high temperature environment, no matter how much the heat generated in the robot controller is exhausted outward by the heat dissipation fan, the air itself that replaces the exhausted air itself is also. Since the temperature is extremely high, the inside of the robot controller may be overheated. In other words, when the motor is decelerating (during regeneration), if a large amount of heat is unexpectedly generated from the regenerative resistor, the air that was originally taken into the robot controller is hot and the electronic components such as the CPU radiate heat. Heat will be further applied to where it is. Therefore, it is considered that the temperature in the robot controller exceeds the operation guarantee temperature, and depending on the situation, the robot controller may be stopped.

  The present invention has been made in view of the above circumstances, and has as its main object to provide a robot controller that suppresses a sudden increase in heat generation during motor regeneration and can drive the motor in a suitable state. To do.

  Hereinafter, means and the like effective for solving the above-described problems will be described while showing functions and effects as necessary.

A first invention rectifies AC power and outputs DC power;
A capacitor connected to the power path on the output side of the rectifier circuit;
DC power is supplied from the rectifier circuit through the power path, and the inverter circuit that drives the motor by converting the DC power into driving power;
A robot controller that controls the inverter circuit to operate the motor according to a predetermined operation pattern consisting of an acceleration period, a constant speed period, and a deceleration period,
A first switch for opening and closing the power path between the rectifier circuit and the capacitor;
A regenerative resistor connected to the power path and recovering regenerative power of the motor by heat conversion;
A second switch connected in series to the regenerative resistor;
During the deceleration period, the regenerative power is recovered by charging the capacitor, and when the charge voltage of the capacitor reaches a predetermined upper limit voltage, the second switch is closed and the regenerative power is generated by the regenerative resistor. Power recovery control means for recovery;
Voltage drop control means for performing a voltage drop process for dropping the charging voltage of the capacitor by repeatedly opening and closing the first switch in a constant speed period immediately before the deceleration period;
With
The voltage drop control means includes
Means for acquiring a motor deceleration width in the deceleration period before starting the voltage drop process in the constant speed period;
Using the relationship between the motor deceleration width and the regenerative resistance heat generated by the regenerative resistance during motor deceleration at that motor deceleration width, based on the acquired motor deceleration width, the voltage at the start of deceleration that is the capacitor charging voltage at the start of deceleration And a switching mode for setting a voltage drop by opening and closing the first switch;
Means for lowering the charging voltage of the capacitor to the set deceleration start voltage by controlling the open / closed state of the first switch in the set switching mode;
It is characterized by providing.

  According to the above configuration, as the basic operation, when the motor is decelerated (regeneration), the regenerative power is recovered by charging the capacitor, and when the charging voltage of the capacitor reaches a predetermined upper limit voltage, 2 The switch is closed and the regenerative power is recovered by the regenerative resistor. Here, the longer the power recovery by the regenerative resistor after the recovery of the regenerative power by charging the capacitor, the more the heat generated by the regenerative resistor, and there is a concern that the robot controller excessively increases in temperature.

  In this regard, the present invention pays attention to the fact that the amount of regenerative power at the time of motor deceleration varies according to the motor deceleration width during the motor deceleration period, and the motor deceleration width at the time of motor deceleration that will occur in the constant speed period immediately before the motor deceleration. Based on the above, a deceleration start voltage that is a capacitor charging voltage at the start of deceleration and a switching mode for performing a voltage drop by opening and closing the first switch are set. In this case, in particular, the deceleration start voltage and the switching mode are set using the relationship between the motor deceleration width and the regenerative resistance heat generated by the regenerative resistance when the motor decelerates within the motor deceleration width. In the constant speed period, the open / close state of the first switch is controlled so that the capacitor charging voltage becomes the deceleration start voltage when the motor deceleration starts. By reducing the capacitor charging voltage before starting the motor deceleration in this way, the amount of power recovered by the capacitor increases when the motor decelerates, and as a result, the power recovery (that is, heat conversion) by the regenerative resistor can be reduced. In addition, the voltage drop process in the constant speed period can be performed after considering (predicting) the regenerative resistance heat generated when the motor is decelerated. Therefore, an excessive temperature rise in the robot controller can be suppressed.

  Here, when the voltage drop process is performed, when the first switch is opened and closed (switching operation), heat is considered to be generated by the opening and closing operation. However, even if heat is generated in the switching operation, it is a constant speed period before the start of deceleration (in other words, a period in which regenerative power does not occur). From the time axis, heat generated by the switching operation and power generated by the regenerative resistor The heat generated by the recovery is dispersed back and forth. Therefore, it is possible to suppress inconvenience due to heat generation concentrated in one period. Even if the amount of heat generated during the switching operation of the first switch is greater than the amount of heat generated by the regenerative resistor corresponding to the voltage drop due to the switching operation, the heat generation time (the time for repeatedly opening and closing the first switch) Can be prevented from being concentrated at a time.

  For example, in a configuration in which heat in the robot controller is exhausted by a heat radiating fan, the capacity of the heat radiating fan can be used without waste and efficient heat exhaust can be performed.

  As described above, in the present invention, the heat generation can be distributed and the heat generation amount of the regenerative resistor can be reduced. Even if the temperature in the installation environment of the robot controller is high, the temperature in the robot controller is kept at a predetermined temperature. It is possible to suppress a situation in which the robot controller is unintentionally stopped due to exceeding.

  Further, in the above configuration, since the voltage drop is performed based on the motor deceleration width during the motor deceleration period, the voltage drop can be performed in accordance with the amount of regenerative power that actually occurs during motor deceleration. Therefore, it is possible to suppress an excessive voltage drop before the motor is decelerated, and it is possible to eliminate the influence on the motor drive. Furthermore, in terms of the constant speed period, the voltage gradually decreases by repeatedly opening and closing the first switch. For this reason, it is possible to suppress a situation in which the capacitor charging voltage is excessively lowered due to a rapid voltage drop during the constant speed period, and the voltage drop can be performed without disturbing the constant speed operation of the motor.

  As described above, it is possible to suppress a sudden increase in heat generation during motor regeneration and to drive the motor in a suitable state.

  In a second invention, the voltage drop control means sets, as the switching embodiment, a switching time width that is a time for repeatedly opening and closing the first switch at a predetermined switching cycle based on the motor deceleration width, When the set switching time width is longer than the time width of the constant speed period, the switching time width is limited by the time width of the constant speed period.

  According to the above configuration, when the switching time width is longer than the time width of the constant speed period of the motor, the switching time width is limited by the time width of the constant speed period. In such a case, since the voltage drop process is not performed in the acceleration period, which is the period immediately before the constant speed period, power supply is given priority to motor driving in the acceleration period. Accordingly, it is possible to avoid the inconvenience that the motor driving during the acceleration period is hindered by the voltage drop process.

In a third aspect of the invention, the amount of heat generated when the first switch is opened and closed in the set switching mode, the switching time width of the first switch at the time of opening and closing, the switching cycle, and the first switch Estimating means for estimating based on on-time,
The voltage drop control means changes the switching mode in order to reduce the heat generation amount due to opening and closing of the first switch when the estimated heat generation amount exceeds a predetermined predetermined heat generation amount. .

  According to the above configuration, the amount of heat generated when the first switch is opened and closed is estimated based on the switching time width of the first switch, the switching period, and the ON time of the first switch, so that the amount of heat generated can be obtained correctly. Can do. Further, when the heat generation amount (estimated value) generated when the first switch is opened and closed exceeds a predetermined heat generation amount, the switching mode is changed to reduce the heat generation amount due to opening and closing of the first switch. . As a change of this switching embodiment, it is conceivable to shorten the switching time width of the first switch, shorten the on-time (decrease the on-time ratio), or the like. In such a case, the temperature of the robot controller can be more appropriately managed by considering the amount of heat generated before the motor is decelerated (before regeneration).

  According to a fourth aspect of the present invention, the apparatus further comprises means for interrupting a power path between the rectifier circuit and the capacitor by the first switch during the deceleration period.

  In the above configuration, the power path between the rectifier circuit and the capacitor is interrupted by the first switch during the motor deceleration period. As a result, the power supply from the rectifier circuit to the capacitor is stopped during regeneration due to motor deceleration, and the rate of increase of the capacitor charging voltage is reduced. Therefore, power recovery (that is, heat conversion) due to regenerative resistance can also be reduced.

In a fifth aspect of the invention, the motor is an AC servo motor provided in a movable part of an industrial robot,
Temperature detecting means for detecting the temperature in the environment where the robot controller is installed,
The voltage drop control means determines whether or not to perform the voltage drop process based on the detected temperature.

  In the above configuration, in order to determine whether to perform the voltage drop process based on the detected temperature in the environment where the robot controller is installed, for example, the air taken into the robot controller from the outside is in a predetermined high temperature state. Only in such a situation, the voltage drop process can be implemented. That is, the voltage drop process can be appropriately performed according to the necessity of reducing the heat generation amount.

The block diagram which shows the outline | summary of a motor control system. A time chart for explaining basic operation about motor control. The time chart for demonstrating operation | movement when a robot working room is a high temperature state. The time chart for demonstrating operation | movement at the time of implementing voltage drop control. The flowchart which shows the process sequence of electric power collection | recovery control. The flowchart which shows the process sequence of a voltage drop aspect setting process. (A) is a figure which shows the relationship between motor maximum speed Vp and target voltage EL, (b) is a figure which shows the relationship between target voltage EL and switching time width HT1.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. In the present embodiment, a control system for an AC servo motor incorporated in a movable part (joint part) of an industrial robot is embodied. The control system includes a robot body having a plurality of motors, and the robot body. And a robot controller for controlling the robot. Although not shown because it is a well-known configuration, the robot controller has, for example, a metal casing having a rectangular parallelepiped shape and various boards (control board, power supply board, etc.) provided in the casing. Next, the outline of this control system will be described with reference to FIG.

  As shown in FIG. 1, this control system controls, as main components, a motor (AC servomotor) 11 provided in the robot body, a motor drive device 12 that drives the motor 11, and the motor drive device 12. As a result, a control unit 13 for controlling the motor 11 is provided. First, the motor drive device 12 will be described.

  In the motor drive device 12, a rectifier circuit 23 is connected to the AC power source 21 via a noise filter 22. The rectifier circuit 23 is composed of, for example, a bridge full-wave rectifier circuit composed of four diodes. The rectifier circuit 23 converts AC power into DC power. For example, AC power of AC 200 V is output from the AC power source 21, and the AC power is rectified by the rectifier circuit 23, whereby DC power of DC 280 V is output from the rectifier circuit 23.

  Power paths 24 and 25 are connected to the output side of the rectifier circuit 23, and a smoothing circuit 29 including a backflow prevention diode 26, a choke coil 27, and a capacitor 28 is connected to the power paths 24 and 25. ing. In addition, a drive circuit 30 is connected to the power paths 24 and 25 in parallel with the diode 26 and the capacitor 28. The drive circuit 30 includes a three-phase inverter circuit. The drive circuit 30 converts DC power into three-phase AC power, and the three-phase AC power is supplied to the motor 11 as drive power. The motor 11 is driven by the supply of drive power from the drive circuit 30.

  A first switch 31 is provided in the power path 24, and the power path 24 is opened and closed between the rectifier circuit 23 and the capacitor 28 by the first switch 31. When the first switch 31 is turned on (closed), power is supplied from the rectifier circuit 23 to the drive circuit 30 side, and when the first switch 31 is turned off (opened), the rectifier circuit 23 is driven from the drive circuit 30 side. The power supply to is stopped. Further, a series circuit of a regenerative resistor 32 and a second switch 33 is connected between the power paths 24 and 25. The switches 31 and 33 are semiconductor switches such as MOSFETs. During regeneration of the motor 11, the second switch 33 is turned on (closed) so that regenerative power from the motor 11 flows to the regenerative resistor 32. Thereby, the regenerative electric power is converted into heat by the regenerative resistor 32 and recovered (consumed).

  The control unit 13 is a known logical operation circuit having a CPU, various memories, and the like, and performs various motor controls by a control program stored in the memory. For example, the rotation of the motor 11 is controlled by controlling a plurality of switching elements provided in the drive circuit 30 with a PWM signal. In this case, the control unit 13 performs position feedback control of the motor 11 based on the detection signal of the position detection unit 35 formed of a rotary encoder. In addition, the control unit 13 monitors the rotation state of the motor 11 based on the detection signal of the current detection unit 36. The control unit 13 is connected to a voltage detection unit 37 that detects a charging voltage of the capacitor 28 (voltage between the power paths 24 and 25) and a temperature sensor 38 that detects the temperature of the robot working chamber.

  The control unit 13 controls the first switch 31 and the second switch 33, and performs power recovery control and voltage drop control by controlling opening and closing of the switches 31 and 33 during motor regeneration. As the power recovery control, when the motor 11 is regenerated (decelerated), the regenerative power is recovered by charging the capacitor 28, and when the charging voltage of the capacitor 28 reaches a predetermined upper limit voltage, The switch 33 is closed and the regenerative power is recovered by the regenerative resistor 32. As voltage drop control, the capacitor charging voltage at the start of motor regeneration is lowered by repeatedly opening and closing the first switch 31 before the regeneration of the motor 11 is started. However, details of each control will be described later.

  Next, a basic operation relating to motor control will be described using the time chart of FIG. In FIG. 2, (a) shows the change in motor speed, (b) shows the change in ON / OFF state of the first switch 31, and (c) shows the bus voltage which is the capacitor charging voltage (voltage between the power paths 24 and 25). The transition of Ebus, (d) shows the transition of the controller heat amount, which is the amount of heat generated by the robot controller, and (e) shows the transition of the second switch 33 on / off. In FIG. 2, the first switch 31 is kept on throughout the entire period.

  In FIG. 2, it is assumed that both positive side and negative side operations are repeatedly performed on the motor 11, T10 in the figure is a negative side operation period, and T20 is a positive side operation period. A period T30 between the negative operation period T10 and the positive operation period T20 is a transition period from the negative operation to the positive operation (or vice versa). The period T30 is also an operation stop period in which the motor speed = 0. In each of the periods T10 and T20, acceleration control, constant speed control (constant speed), and deceleration control are performed in this order of operation patterns. For example, in the positive operation period T20, T21 is The acceleration period, T22 is a constant speed period, and T23 is a deceleration period. In this embodiment, the maximum speed during negative side operation (negative maximum speed) is Vp1, the maximum speed during positive side operation (positive maximum speed) is Vp2, and | Vp1 | <| Vp2 |.

  A specific operation will be described by taking the positive operation period T20 as an example. First, in the acceleration period T21, the motor control is performed so that the motor speed changes from 0 to the positive side. At this time, the motor speed increases (positive increase) at a constant acceleration, and eventually reaches the positive maximum speed Vp2. In the constant speed period T22, the motor speed is maintained at the maximum positive speed Vp2. Thereafter, in the deceleration period T23, the motor control is performed so that the motor speed decreases from the positive maximum speed Vp2 to 0 at a constant acceleration.

  Here, the relationship between the transition of the motor speed and each transition of the bus voltage Ebus and the controller heat amount will be described. In the acceleration period T21, the bus voltage Ebus decreases with power consumption due to motor acceleration. At this time, in the acceleration period T21, the bus voltage Ebus at the beginning of the period is equal to or higher than a reference voltage Etyp (for example, 280V) that is an output voltage of the rectifier circuit 23, and the bus voltage Ebus is within the synchronization period T21. The voltage drops to a voltage range that is lower than that.

  Thereafter, in the constant speed period T22, the power consumption by driving the motor is reduced. Therefore, the bus voltage Ebus rises and returns to the reference voltage Etyp as power is supplied through the rectifier circuit 23 (provided that the constant speed period T22 is short). Not limited to this).

  In the deceleration period T23, regenerative power is supplied to the capacitor 28 along with regeneration due to motor deceleration, and the bus voltage Ebus increases (that is, the regenerative power is recovered by charging the capacitor 28). At this time, when the bus voltage Ebus rises to a predetermined regenerative resistance on voltage Eon (upper limit voltage), the second switch 33 is turned on. Thereby, regenerative electric power is supplied to the regenerative resistor 32, and the regenerative electric power is recovered (consumed) by being converted into heat in the regenerative resistor 32. The regenerative resistor ON voltage Eon is preferably determined based on the upper limit amount of charge of the capacitor 28, and a threshold for switching the recovery of the regenerative power from the recovery by charging the capacitor 28 to the recovery by heat conversion at the regenerative resistor 32. Value.

  Thus, the regenerative electric power is consumed by the regenerative resistor 32, so that the controller heat amount rises from the reference value Qtyp. The reference value Qtyp is a standard heat amount when the robot controller is operated. In such a case, the robot controller is provided with heat radiating means such as a heat radiating fan, and the internal temperature of the robot controller is controlled by the heat radiating fan or the like so that the controller heat quantity becomes the reference value Qtyp. In addition, the structure which provides the temperature sensor which detects the internal temperature of a robot controller, and controls the action | operation of a thermal radiation fan based on the detected temperature may be sufficient.

  In the present control system, an upper limit value Qth of the controller heat quantity for guaranteeing the operation of the control unit 13 or the like is determined. During the basic operation shown in the figure, the controller heat quantity does not reach the upper limit value Qth, and the control unit 13 and the like continuously operate normally.

  After the end of the positive operation period T20, the process proceeds to the negative operation period T10 via the transition period T30. In the negative side operation period T10, basically the same motor control as in the positive side operation period T20 is performed, and each control of acceleration, constant speed, and deceleration is performed in the synchronization period T10. As a result, the bus voltage Ebus and the controller heat amount change in substantially the same manner as in the positive side operation period T20. However, compared with the positive side operation period T20, the magnitudes (absolute values) of the maximum speeds Vp1 and Vp2 are different and | Vp1 | <| Vp2 |. Therefore, at the time of motor regeneration (during deceleration), controller heat amount increases ΔQ1 and ΔQ2 are different, and ΔQ2> ΔQ1.

  By the way, in this embodiment, the case where the robot main body (including the motor drive device 12) and the robot controller (control unit 13) are both provided in the same robot working room is assumed. In such a case, in the robot working room, a change in the room temperature may occur due to a change in the outside air temperature or heat generation in the robot body, and the robot controller (control unit 13) may be adversely affected due to the change in the room temperature. FIG. 3 is a time chart for explaining the operation when the robot working chamber is in a high temperature state according to, for example, the outside air temperature. In FIG. 3, the items of each chart shown in FIGS. 3A to 3E are the same as those in FIG. 2, and the motor speed increase / decrease change pattern and the accompanying parameter change are also the same as those in FIG.

  In FIG. 3, due to the high temperature in the robot working chamber, the controller heat quantity shown in (d) is larger than that shown in FIG. 2, and is higher than the reference value Qtyp throughout the entire period shown. It has become. The transition of the controller heat amount described in FIG. 2 is indicated by a one-dot chain line. In this case, if the controller heat amount rises during motor regeneration (deceleration), the controller heat amount may rise above the upper limit value Qth as shown. Then, when the controller heat quantity> the upper limit value Qth, for example, measures such as operation stop are appropriately performed to avoid abnormal operation of the control unit 13.

  Here, it is not desirable from the viewpoint of driving efficiency that the operation is forced to stop during the robot operation. Therefore, in this embodiment, immediately before regeneration due to motor deceleration, voltage drop control is performed in preparation for a rise in bus voltage (voltage between both electrodes of the capacitor) during subsequent motor regeneration. The voltage drop control actively lowers the bus voltage during the motor regeneration period (deceleration period T23), thereby lowering the peak value of the bus voltage during motor regeneration. The period during which power is consumed by the regenerative resistor 32 is shortened, and the controller heat amount is reduced.

  FIG. 4 is a time chart for explaining the operation when the voltage drop control in this embodiment is performed. In FIG. 4, the items in the charts shown in FIGS. 4A to 4E are the same as those in FIGS. 2 and 3, and the motor speed increase / decrease change pattern and the accompanying parameter change are the same as those in FIGS. is there. Note that the controller heat quantity is larger than that shown in FIG. 2 due to the high temperature in the robot working chamber as in FIG. 3, and is higher than the reference value Qtyp throughout the entire period shown in the figure. It has become.

  In FIG. 4, in the acceleration period T21 of the positive side operation period T20, the bus voltage Ebus decreases with the power consumption due to motor acceleration (similar to FIGS. 2 and 3). After that, in the constant speed period T22, the bus voltage Ebus rises with the power supply through the rectifier circuit 23 in the period when the first switch 31 = ON at the beginning of the period, and thereafter, the ON / OFF of the first switch 31 is performed. The bus voltage Ebus drops as a result of switching off (switching). Specifically, when the first switch 31 is switched on / off, the power path 24 leading from the rectifier circuit 23 to the capacitor 28 is opened (shut off) when the first switch 31 is turned off, and the bus voltage Ebus drops due to power consumption in the motor 11.

  The bus voltage Ebus is limited so that the minimum operating voltage Emin is the lower limit and does not drop below that. The minimum operating voltage Emin is a minimum voltage determined to guarantee the operation of the motor 11 and the control unit 13.

  Comparing the behavior of FIG. 3 and FIG. 4, at the start of the deceleration period T23, Ebus = Etyp in FIG. 3 whereas Ebus = Emin (<Etyp) in FIG. . That is, in FIG. 3, the bus voltage Ebus increases in the constant speed period T22 before the start of motor regeneration, whereas in FIG. 4, the bus voltage Ebus decreases in the constant speed period T22. The bus voltage Ebus at the start of motor regeneration is different.

  In the switching period TA in which the first switch 31 is switched on / off in the constant speed period T22, operating heat is generated along with the switching, and the controller heat amount is increased accordingly.

  Thereafter, in the deceleration period T23, regenerative power is supplied to the capacitor 28 along with motor regeneration, and the bus voltage Ebus increases. At this time, since the bus voltage Ebus at the start of the deceleration period T23 is lower than the reference voltage Etyp as described above, the bus voltage Ebus rises to the regenerative resistance on-voltage Eon as compared with FIG. Therefore, the time required for Ebus ≧ Eon in the deceleration period T23 is shortened. The shortening of the period in which Ebus ≧ Eon means that the ON period of the second switch 33 is shortened, and further, the period in which the regenerative power is thermally converted in the regenerative resistor 32 is shortened. . Therefore, an increase in the controller heat quantity can be suppressed.

  In the deceleration period T23, the first switch 31 is held in the off state. Therefore, the power supply from the rectifier circuit 23 to the capacitor 28 is stopped, and the rise of the bus voltage Ebus is suppressed.

  In the above series of operations, operating heat is generated by the switching operation of the first switch 31 during the switching period TA in the constant speed period T22. However, this operation heat is generated ahead of the heat conversion of the regenerative power by the regenerative resistor 32, and the heat generation is performed in a distributed manner when viewed as a whole in the positive side operation period T20. That is, the heat generation during the positive-side operation period T20 includes heat generation due to the switching operation of the first switch 31 (heat generation during the constant speed period T22) and heat generation due to power recovery at the regenerative resistor 32 (heat generation during the deceleration period T23). And distributed. Therefore, it is possible to suppress a situation in which heat is concentrated at a specific time when the motor 11 is operated, and thus an excessive temperature rise in the robot controller is suppressed.

  Next, power recovery control performed by the control unit 13 will be described. FIG. 5 is a flowchart showing a processing procedure of power recovery control, and this processing is repeatedly performed by the control unit 13 at a predetermined time period.

  In FIG. 5, first, in step S11, it is determined whether a precondition for performing the voltage drop control is satisfied. This precondition is, for example, that the temperature in the robot working room (temperature detected by the temperature sensor 38), which is the temperature in the environment where the robot controller is installed, is equal to or higher than a predetermined determination value (for example, 30 ° C.). If the temperature of the robot working chamber is equal to or greater than the determination value, step S11 is affirmed. And if step S11 is affirmed, voltage drop control will be implemented by each step after step S12.

  When step S11 is NO, normal power recovery control (not shown) is performed. This normal power recovery control corresponds to control for realizing the operation described in the time chart of FIG. That is, in such power recovery control, the first switch 31 is always kept on, and the second switch 33 is temporarily turned on when the bus voltage Ebus> the regenerative resistance on voltage Eon during motor regeneration. It is like that.

  In step S12, it is determined whether or not it is currently in the transition period (transition period T30 in FIG. 4 etc.) between the negative and positive operation periods. If it is currently the transition period, the process proceeds to step S13, and a voltage drop mode setting process is performed. In this voltage drop mode setting process, based on the motor deceleration width in the motor deceleration period (motor regeneration period), the target voltage VL (deceleration start voltage), which is the bus voltage Ebus at the start of motor regeneration, is dropped. This is a process of setting a time width (switching time width) of the switching period TA for the purpose. The details will be described later.

  Also, if it is not currently the transition period (if step S12 is NO), acceleration, constant speed, and deceleration are currently performed in each of the negative and positive operation periods by the determination processes in steps S14 and S15. It is determined in which period. And if it is an acceleration period (it is YES at step S14), it will progress to step S16 and will perform control which hold | maintains the 1st switch 31 in an ON state. If it is the constant speed period (YES in step S15), the process proceeds to step S17, and the first switch 31 is based on the voltage drop mode (time width of the switching period TA) set in the voltage drop mode setting process in step S13. Is switched on / off. If steps S14 and S15 are YES, the second switch 33 is held off.

  Moreover, if it is a deceleration period (step S15 is NO), it will progress to step S18. In step S18, control for holding the first switch 31 in the OFF state is performed. In the subsequent step S19, the second switch 33 is controlled to be in an on state when the bus voltage Ebus> the regenerative resistance on voltage Eon.

  FIG. 6 is a flowchart showing a processing procedure of the voltage drop mode setting process (step S13 in FIG. 5).

  In FIG. 6, first, in step S21, based on a predetermined operation pattern, a speed command value in either the positive or negative operation period of the motor 11 is acquired, and the maximum value of the motor 11 is obtained from the speed command value. Read speed Vp. Note that the speed data of the operation pattern can be acquired by an operation test or the like in the teaching stage, and therefore the maximum speed Vp can be acquired even before the regeneration is started. At this time, “Vp1” is read as the maximum speed Vp in the negative side operation period T10 of FIG. 4, and “Vp2” is read as the maximum speed Vp in the positive side operation period T20. In the present embodiment, the maximum speed Vp corresponds to a “motor deceleration width” in the motor regeneration period, and step S21 corresponds to “a means for acquiring a motor deceleration width”.

  As a configuration for obtaining the maximum speed Vp of the motor 11, it is also possible to obtain a speed change at each acceleration operation and obtain the maximum speed Vp from the speed change.

  Next, in step S22, a peak value (hereinafter referred to as peak voltage Ebus1) of the bus voltage Ebus in the current motor operation period (either the negative side operation period T10 or the positive side operation period T20 in FIG. 4) is calculated. . The peak voltage Ebus1 is calculated based on Vp and Etyp using the motor maximum speed Vp and the reference voltage Etyp (output voltage of the rectifier circuit 23) as parameters. Specifically, the peak voltage Ebus1 may be calculated based on the following equation (2) obtained from the following equation (1).

なお、（１）式、（２）式において、ｍは、モータ１１による駆動される可動部（ロボットアーム）の質量であり、Ｃはコンデンサ２８の静電容量である。

In equations (1) and (2), m is the mass of the movable part (robot arm) driven by the motor 11, and C is the capacitance of the capacitor 28.

  Thereafter, in step S23, it is determined whether or not the peak voltage Ebus1 is larger than the regenerative resistance on voltage Eon. If Ebus1> Eon, the process proceeds to the subsequent step S24, and if Ebus1 ≦ Eon, the process ends. In this case, if Ebus1 ≦ Eon, the second switch 33 is not turned on during motor regeneration, and regenerative power is recovered only by charging the capacitor 28.

  In step S24, the target voltage EL is set as the target value of the bus voltage Ebus at the time of voltage drop. The target voltage EL is a relationship between the motor deceleration width (motor maximum speed Vp) during the motor deceleration period and the regenerative resistance heat generated by the regenerative resistance when the motor decelerates at that motor deceleration width, that is, the regenerative resistance increases as the motor deceleration width increases. This is a deceleration start time voltage calculated based on the motor deceleration range for each time, using a relationship that increases the assumed amount of heat. In this embodiment, the motor maximum speed Vp is used as a calculation parameter, and the target voltage EL is calculated based on the relationship shown in FIG. FIG. 7A is created from the relationship between the motor maximum speed Vp and the regenerative resistance heat, and the target voltage EL increases as the motor maximum speed Vp increases (that is, the assumed amount of regenerative resistance heat increases). Is set as a small value. In other words, a relationship is defined such that the greater the motor maximum speed Vp, the greater the voltage drop width (for example, the voltage difference from the reference voltage Etyp).

  In the time chart of FIG. 4, in the negative side operation period T10, the motor maximum speed Vp = Vp1, and the target voltage EL is set as “EL1”, and in the positive side operation period T20, the motor maximum speed Vp = Vp2. Yes, the target voltage EL is set as “EL2”. In this case, since | Vp1 | <| Vp2 |, EL1> EL2.

  As a method for setting the target voltage EL, it is also possible to calculate the heat generation amount Qreg of the regenerative resistor 32 during motor regeneration, and to calculate the target voltage EL based on the heat generation amount Qreg and the motor maximum speed Vp. The heat generation amount Qreg is calculated based on Vp and Etyp using the motor maximum speed Vp and the reference voltage Etyp (output voltage of the rectifier circuit 23) as parameters. Specifically, the calorific value Qreg may be calculated based on the following equation (3).

そして、回生抵抗３２の発熱量Ｑｒｅｇとモータ最大速度Ｖｐとをパラメータとして、これらＱｒｅｇ、Ｖｐに基づいて目標電圧ＥＬを算出する。具体的には、次の（４）式に基づいて目標電圧ＥＬが算出されるとよい。

Then, the target voltage EL is calculated based on these Qreg and Vp using the heat generation amount Qreg of the regenerative resistor 32 and the motor maximum speed Vp as parameters. Specifically, the target voltage EL may be calculated based on the following equation (4).

その後、ステップＳ２５では、モータ等速期間（図４のＴ２２）においてバス電圧Ｅｂｕｓを目標電圧ＥＬまで電圧降下させるために必要な時間であるスイッチング期間ＴＡの時間幅（以下、スイッチング時間幅ＨＴ１という）を算出する。スイッチング時間幅ＨＴ１は、モータ減速期間でのモータ減速幅（モータ最大速度Ｖｐ）に基づいて算出される電圧降下実施時間である。本実施形態では、モータ最大速度Ｖｐに基づいて算出される目標電圧ＥＬを演算パラメータとして、図７（ｂ）の関係に基づいてスイッチング時間幅ＨＴ１を算出する。図７（ｂ）では、目標電圧ＥＬが小さいほど（すなわち、電圧降下幅が大きいほど）、スイッチング時間幅ＨＴ１が大きい値として設定されるような関係が定められている。

Thereafter, in step S25, the time width of the switching period TA (hereinafter referred to as the switching time width HT1), which is the time required to drop the bus voltage Ebus to the target voltage EL in the motor constant speed period (T22 in FIG. 4). Is calculated. The switching time width HT1 is a voltage drop execution time calculated based on the motor deceleration width (motor maximum speed Vp) in the motor deceleration period. In the present embodiment, the switching time width HT1 is calculated based on the relationship of FIG. 7B using the target voltage EL calculated based on the motor maximum speed Vp as an operation parameter. In FIG. 7B, a relationship is set such that the smaller the target voltage EL is (that is, the larger the voltage drop width), the larger the switching time width HT1 is set.

  It is also possible to calculate the switching time width HT1 based on the motor maximum speed Vp with the horizontal axis of FIG. When the horizontal axis is the motor maximum speed Vp, the relationship is such that the switching time width HT1 is set to a larger value as the motor maximum speed Vp increases.

  Thereafter, in step S26, it is determined whether or not the switching time width HT1 is smaller than the time width HT2 of the motor constant speed period. The time width HT2 of the motor constant speed period is a time predetermined as an operation pattern. If HT1 <HT2, the process proceeds directly to step S28 without changing the switching time width HT1. On the other hand, if HT1 ≧ HT2, the process proceeds to step S27, where the switching time width HT1 is rewritten with the time width HT2 of the motor constant speed period, and then the process proceeds to step S28. That is, when the switching time width HT1 calculated in step S25 is longer than the time width HT2 of the constant speed period, the switching time width HT1 is limited by the time width HT2 of the constant speed period.

  Thereafter, in step S28, the heat generation amount Qsw when the first switch 31 performs the switching operation with the calculated switching time width HT1 is calculated. The calorific value Qsw is calculated based on HT1, Tf, and Ton using at least the switching time width HT1, the switching period Tf, and the on-time Ton of the first switch 31 as parameters. Specifically, the calorific value Qsw may be calculated based on the following equation (5).

なお、Ｉｐは負荷ピーク電流（第１スイッチ３１＝オン時の電流）、Ｔｓｗは第１スイッチ３１のターンオン及びターンオフに要するディレイ時間、Ｒｏｎは第１スイッチ３１のオン抵抗である。

Note that Ip is a load peak current (first switch 31 = current when turned on), Tsw is a delay time required for turning on and turning off the first switch 31, and Ron is an on resistance of the first switch 31.

  In step S29, it is determined whether or not the heat generation amount Qsw of the first switch 31 is smaller than a predetermined upper limit value Qth. If Qsw <Qth, the process is terminated without changing the switching time width HT1. If Qsw ≧ Qth, the process proceeds to step S30 to shorten the switching time width HT1. At this time, the switching time width HT1 that does not exceed the upper limit value Qth may be calculated based on the following equation (6).

モータ１１の各動作期間では、上記のように算出されたスイッチング時間幅ＨＴ１に基づいて電圧降下の処理が実施される。これにより、各動作期間の等速期間において、モータ減速期間での回生電力の回収に備えて事前にバス電圧Ｅｂｕｓ（コンデンサ充電電圧）が降圧されることとなる。

In each operation period of the motor 11, a voltage drop process is performed based on the switching time width HT1 calculated as described above. Thus, the bus voltage Ebus (capacitor charging voltage) is stepped down in advance in preparation for recovery of regenerative power during the motor deceleration period in the constant speed period of each operation period.

  According to the embodiment described in detail above, the following excellent effects can be obtained.

  Before starting the regeneration of the motor 11, the target voltage EL (deceleration) that is the target value of the bus voltage Ebus at the start of the motor regeneration is based on the motor maximum speed Vp (the motor deceleration width during the motor regeneration period) in each operation period of the motor 11. A voltage at which the bus voltage Ebus is lowered to the target voltage EL by setting the switching time width HT1 (switching mode) of the first switch 31 and controlling the open / closed state of the first switch 31. did. According to this configuration, the amount of power recovered by the capacitor 28 increases during motor regeneration, and as a result, power recovery (that is, heat conversion) by the regenerative resistor 32 can be reduced.

  Here, when performing the voltage drop process, when the first switch 31 is opened and closed (switching operation), heat is generated by the opening and closing operation, but the switching operation heat is generated at a constant speed period (in other words, the regeneration operation). In a time axis, the heat generated by the switching operation of the first switch 31 and the heat generated by the power recovery by the regenerative resistor 32 are distributed back and forth. Therefore, it is possible to suppress inconvenience due to heat generation concentrated in one period. Speaking of a configuration in which the heat in the robot controller is exhausted by the heat radiating fan, the capacity of the heat radiating fan can be used without waste and efficient exhaust heat can be implemented.

  As described above, in this embodiment, the heat generation can be distributed and the heat generation amount of the regenerative resistor 32 can be reduced. Even if the temperature (the temperature of the robot working chamber) in the installation environment of the robot controller is high, It is possible to suppress a situation in which the temperature inside the robot controller exceeds a predetermined temperature and the robot controller is stopped unintentionally. As a result, the robot can be continuously operated regardless of the installation environment of the robot controller, and as a result, the operation efficiency of the robot can be kept good.

  In the above configuration, since the voltage drop is performed based on the motor maximum speed Vp using the relationship between the motor maximum speed Vp and the regenerative resistance heat, the amount of regenerative power actually generated during motor regeneration (regeneration resistance heat assumption) The voltage drop can be implemented according to the amount agreed. Therefore, it is possible to suppress an excessive voltage drop before the motor regeneration, and to eliminate the influence on the motor drive. Furthermore, in terms of the constant speed period, the voltage gradually decreases by repeatedly opening and closing the first switch 31. Therefore, it is possible to suppress a situation in which the capacitor charging voltage is excessively lowered due to a rapid voltage drop during the constant speed period, and the voltage drop can be performed without disturbing the constant speed operation of the motor 11.

  As described above, it is possible to suppress a sudden increase in heat generation during motor regeneration and to drive the motor 11 in a suitable state.

  In order to reduce the heat generated by the regenerative resistor 32 during motor regeneration, it is conceivable to increase the amount of power recovered by the capacitor 28 (that is, increase the capacity of the capacitor), but such treatment is desirable in view of the utilization efficiency of electronic components. It can not be said. In this regard, according to the present embodiment, it is not necessary to increase the power recovery amount of the capacitor 28, and the utilization efficiency of the electronic component can be suitably maintained.

  When the switching time width HT1 is longer than the time width HT2 of the motor constant speed period, the switching time width HT1 is limited by the time width HT2 of the motor constant speed period. In this case, since the voltage drop process is not performed in the acceleration period, which is the period immediately before the constant speed period, power supply is given priority to motor driving in the acceleration period. Accordingly, it is possible to avoid the inconvenience that the motor driving during the acceleration period is hindered by the voltage drop process.

  The heat generation amount Qsw generated when the first switch 31 is opened and closed is estimated, and when the heat generation amount Qsw exceeds a predetermined upper limit value Qth, the switching mode is changed to reduce the heat generation amount due to opening and closing of the first switch 31. The configuration. Specifically, the switching time width HT1 is shortened. In such a case, the heat generation amount of the robot controller can be monitored in consideration of the heat generation amount before the start of motor regeneration, and the heat generation amount can be more appropriately managed.

  The power path 24 between the rectifier circuit 23 and the capacitor 28 is cut off by the first switch 31 during the deceleration period (motor regeneration period) of the motor 11. Thereby, the power supply from the rectifier circuit 23 to the capacitor 28 is stopped at the time of motor regeneration, and the rising speed of the capacitor charging voltage is slowed down. Therefore, power recovery (that is, heat conversion) by the regenerative resistor 32 can also be reduced.

  A period including an acceleration period, a constant speed period, and a deceleration period is defined as one operation period (negative operation period or positive operation period), and a voltage drop mode is set for each operation period. Specifically, the configuration is such that the target voltage EL and the switching time width HT1 in the next motor operation period are set in each transition period (period of motor speed = 0) between a plurality of operation periods. Thereby, even when the motor maximum speed Vp is different in each operation period, the voltage drop process can be performed in a mode suitable for each operation period.

  Necessity of reducing the amount of heat generated because it is configured to determine whether or not to perform voltage drop processing based on the temperature of the robot work room (that is, the temperature in the environment where the robot controller is installed) Accordingly, the voltage drop process can be appropriately performed. For example, the voltage drop processing can be performed only in a situation where the robot controller is overheated.

[Other Embodiments]
The present invention is not limited to the description of the above embodiment, and may be implemented as follows, for example.

  In the above embodiment, when the bus voltage Ebus (capacitor charging voltage) is decreased in the constant speed period before the regeneration of the motor 11 starts, the switching time width HT1 based on the target voltage EL (or the motor maximum speed Vp) each time. And the first switch 31 is opened and closed within the period of the switching time width HT1 (switching period TA in FIG. 4). However, this may be changed. For example, the ON time (duty ratio) of the first switch 31 in the switching period TA may be variably set based on the target voltage EL (or the motor maximum speed Vp) each time. That is, as the switching mode, the on-time (duty ratio) of the first switch 31 is set instead of the switching time width HT1. At this time, as the time width of the switching period TA is made constant and the target voltage EL is smaller (that is, the voltage drop width is larger), the on-time (duty ratio) of the first switch 31 is made smaller, and the voltage drop speed is set. Enlarge.

  In the above embodiment, the switching time width HT1 is limited by the time width HT2 of the motor constant speed period so that the switching time width HT1 does not become longer than the time width HT2 of the motor constant speed period. That is, the voltage drop is not performed during the motor acceleration period. This configuration may be changed. Even during the motor acceleration period, a voltage drop by opening and closing the first switch 31 may be performed. However, in order to prevent the acceleration operation of the motor 11 from being affected, for example, in the motor acceleration period, the on-time (duty ratio) of the first switch 31 may be set longer than the motor constant speed period. That is, when the voltage drop process is performed not only in the motor constant speed period but also in the motor acceleration period, it is preferable that the control contents be different between the motor acceleration period and the motor constant speed period.

  When the switching time width HT1 is longer than the time width HT2 of the motor constant speed period, in addition to limiting the switching time width HT1 by the time width HT2 of the motor constant speed period, for example, the ON time of the first switch 31 ( The switching mode may be changed by reducing the (duty ratio), thereby increasing the voltage drop rate. In this case, the desired voltage drop can be realized while avoiding the disadvantage that the motor drive during the acceleration period is hindered by the voltage drop process.

  In the above embodiment, it is assumed that the motor speed decreases from the maximum speed Vp to 0 when the motor 11 is decelerated. However, the present invention is also applied to a case where the motor speed decreases from the maximum speed Vp to a predetermined speed greater than 0. Applicable. In this case, the target voltage EL and the switching time width HT1 may be calculated based on the motor deceleration width that is the difference between the motor maximum speed Vp and a predetermined speed (the motor speed at which deceleration is stopped).

  In the above embodiment, the target voltage EL is set based on the maximum motor speed Vp (the motor deceleration range during the motor regeneration period). Instead, the maximum motor speed Vp and the temperature of the robot working chamber each time. The target voltage EL may be set based on (temperature under the setting environment of the robot controller). In this case, the higher the temperature of the robot working chamber, the higher the possibility that the controller heat amount reaches the upper limit value. Therefore, the target voltage EL may be set to a smaller value as the temperature of the robot working chamber is higher.

  -It is good also as a structure which uses the internal temperature of a robot controller as temperature information in the setting environment of a robot controller instead of the temperature of a robot working room. In this case, the internal temperature of the robot controller may be detected by a temperature sensor.

  In the above embodiment, when the switching heat generation amount Qsw of the first switch 31 exceeds the predetermined upper limit value Qth, the switching mode is changed by shortening the switching time width HT1, thereby reducing the switching heat generation amount. However, this may be changed. For example, the switching mode is changed by reducing the ON time (duty ratio) of the first switch 31, thereby increasing the voltage drop speed. In this case, it is possible to realize a desired voltage drop while reducing the amount of heat generated by switching by reducing the number of times of switching (number of times of switching on / off).

  In the above embodiment, for example, the first switch 31 is maintained in the OFF state in the deceleration period T23 illustrated in FIG. 4, but this is changed and the first switch 31 is switched on / off (switching). It is also possible. Also in this case, since power supply from the rectifier circuit 23 to the capacitor 28 is restricted during motor regeneration, it is possible to reduce power recovery (that is, heat conversion) by the regenerative resistor 32.

  DESCRIPTION OF SYMBOLS 11 ... Motor, 12 ... Motor drive device, 13 ... Control part (power recovery control means, voltage drop control means), 21 ... AC power supply, 23 ... Rectifier circuit, 24, 25 ... Power path, 28 ... Capacitor, 30 ... Drive Circuit, 31 ... first switch, 32 ... regenerative resistor, 33 ... second switch, 38 ... temperature sensor (temperature detecting means).

Claims (5)

A rectifier circuit that rectifies AC power and outputs DC power;
A capacitor connected to the power path on the output side of the rectifier circuit;
DC power is supplied from the rectifier circuit through the power path, and the inverter circuit that drives the motor by converting the DC power into driving power;
A robot controller that controls the inverter circuit to operate the motor according to a predetermined operation pattern consisting of an acceleration period, a constant speed period, and a deceleration period,
A first switch for opening and closing the power path between the rectifier circuit and the capacitor;
A regenerative resistor connected to the power path and recovering regenerative power of the motor by heat conversion;
A second switch connected in series to the regenerative resistor;
During the deceleration period, the regenerative power is recovered by charging the capacitor, and when the charge voltage of the capacitor reaches a predetermined upper limit voltage, the second switch is closed and the regenerative power is generated by the regenerative resistor. Power recovery control means for recovery;
Voltage drop control means for performing a voltage drop process for dropping the charging voltage of the capacitor by repeatedly opening and closing the first switch in a constant speed period immediately before the deceleration period;
With
The voltage drop control means includes
Means for acquiring a motor deceleration width in the deceleration period before starting the voltage drop process in the constant speed period;
Using the relationship between the motor deceleration width and the regenerative resistance heat generated by the regenerative resistance during motor deceleration at that motor deceleration width, based on the acquired motor deceleration width, the voltage at the start of deceleration that is the capacitor charging voltage at the start of deceleration And a switching mode for setting a voltage drop by opening and closing the first switch;
Means for lowering the charging voltage of the capacitor to the set deceleration start voltage by controlling the open / closed state of the first switch in the set switching mode;
A robot controller comprising:   The voltage drop control means, as the switching embodiment, sets a switching time width that is a time for repeatedly opening and closing the first switch at a predetermined switching period based on the motor deceleration width, and the set switching time width 2. The robot controller according to claim 1, wherein the switching time width is limited by the time width of the constant speed period when is longer than the time width of the constant speed period. The amount of heat generated when the first switch is opened / closed in the set switching mode is estimated based on the switching time width of the first switch, the switching cycle, and the ON time of the first switch when the switching is performed An estimation means for
The voltage drop control means changes the switching mode to reduce the amount of heat generated by opening and closing the first switch when the estimated amount of heat generation exceeds a predetermined heat generation amount. The robot controller as described in.   4. The robot controller according to claim 1, further comprising means for interrupting a power path between the rectifier circuit and the capacitor by the first switch during the deceleration period. 5. The motor is an AC servo motor provided in a movable part of an industrial robot,
Temperature detecting means for detecting the temperature in the environment where the robot controller is installed,
5. The robot controller according to claim 1, wherein the voltage drop control unit determines whether or not to execute the voltage drop process based on the detected temperature. 6.

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