JP2013070566A - Robot system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply sufficient power to a motor during a high torque operation and effectively use regenerative energy derived from the motor during a slowdown operation without modifying the control content of drive control means for controlling the drive of the motor.SOLUTION: A step-up/down circuit 29 executes a step-up operation of stepping up an input voltage and outputting it, a step-down operation of stepping down the input voltage and outputting it, a power cutoff operation of cutting off the supply of the input voltage, and the like. A power control section 26 controls the operation of the step-up/down circuit 29 so as to execute the step-up operation in a period when a motor M is determined to be sped up on the basis of a detected value of bus voltage, execute the power cutoff operation in a period when it is determined to be slowed down, and execute the step-down operation except in the periods.

Description

  The present invention relates to a robot system including a regeneration consumption circuit for consuming energy regenerated during a deceleration operation from a motor for driving each axis of a robot.

  Each joint (each axis) of the robot is driven by a motor, and these motors are driven by a motor amplifier (driving means) built in the controller. This motor amplifier is composed mainly of an inverter circuit, for example, and converts a DC voltage (bus voltage) supplied from a power supply circuit via a pair of power supply lines into an AC voltage having a predetermined frequency, and supplies power to the motor. Supply.

  In such a configuration, when the motor is decelerated, energy is regenerated from the motor side to the motor amplifier side, and the bus voltage increases accordingly. For this reason, the controller is regenerated so that the bus voltage does not rise beyond the rating of each circuit element connected to the power supply line (switching element of the inverter circuit, capacitor connected between the power supply lines, etc.). A regenerative consumption circuit that converts energy (regenerative energy) into heat energy and releases it is provided.

  In the regenerative consumption circuit, regenerative energy is converted into thermal energy by flowing a regenerative current through a regenerative resistor provided in series between power lines. That is, the regenerative energy is consumed by the regenerative consumption circuit without being effectively used. In order to save energy as a whole robot system, there is a demand to use the regenerative energy effectively. On the other hand, there is also a demand for generating high torque even during high-speed operation, such as during motor acceleration. In order to generate a high torque during high-speed operation, it is necessary to supply the motor with high electric power corresponding to the high torque.

  Patent Document 1 discloses an inverter device including a converter circuit that increases an output voltage at a time before the acceleration of the motor and decreases an output voltage at a time before the motor is decelerated. The timing for increasing and decreasing the output voltage is specified by a program or parameter for controlling the motor.

Japanese Patent No. 3974899

  When the configuration described in Patent Document 1 is used in a robot system, the following problem occurs. That is, the robot system is provided with drive control means for controlling the drive of a plurality of motors corresponding to each axis. By the control (main control) by the drive control means, the hand position of the robot is controlled with high accuracy. When considering the application of the technique described in Patent Document 1 to a robot system, it is necessary to change the content of the main control by the drive control means in order to determine the timing of increase and decrease (step-up and step-down) of the output voltage. .

  Changing the content of the main control related to the drive control of such a motor involves a very complicated operation, leading to an increase in development cost. Further, when the change operation is performed, there is a possibility that an error may occur in the control of the hand position due to a mistake accompanying the change. For these reasons, it is difficult to apply the technique described in Patent Document 1 to a robot system.

  The present invention has been made in view of the above circumstances, and an object thereof is to supply sufficient electric power to the motor during high torque operation without changing the control content of the drive control means for controlling the drive of the motor. Another object of the present invention is to provide a robot system that can effectively use regenerative energy generated from a motor during deceleration operation.

  According to the means described in claim 1, the motor for driving each axis of the robot is driven by the driving means. This driving means operates by receiving an output voltage supplied from the power supply circuit via the output power supply line and the reference power supply line. The drive control means feedback-controls the driving of the motor by the drive means so that the rotation speed of the motor matches the rotation speed command. A regenerative consumption circuit comprising a series circuit of regenerative switch means and a regenerative resistor is provided between the output power line and the reference power line. The regenerative control means turns off the regenerative switch means when the detected value of the output voltage detecting means for detecting the output voltage is less than the regenerative consumption voltage value, and when the detected value is equal to or greater than the regenerative consumption voltage value. In this case, the regeneration switch means is turned on.

  In such a configuration, energy regenerated from the motor during the deceleration operation (regenerative energy) is accumulated as electrostatic energy in a capacitor connected between the output power supply line and the reference power supply line. That is, when the motor is decelerating, the capacitor is charged by regenerative energy, and the output voltage, which is the voltage across the capacitor, increases. When the output voltage (detected value of the output voltage detection means) is equal to or higher than the regenerative consumption voltage value, the regenerative energy is released as heat energy by passing a current through the regenerative resistor of the regenerative consumption circuit, and the output voltage becomes the regenerative consumption voltage value. The voltage rise is suppressed so as to be less than

  The power supply circuit selectively performs a step-up operation, a step-down operation, and a power cut-off operation, and includes an inductor, a first switch unit, a first diode, a second switch unit, and a second diode. Yes. The first switch means is connected between the input power supply line and one terminal of the inductor. The first diode is connected between one terminal of the inductor and the reference power supply line with the reference power supply line side as an anode. The second switch means is connected between the other terminal of the inductor and the reference power supply line. The second diode is connected between the other terminal of the inductor and the output power supply line with the other terminal of the inductor as the anode.

  When the power supply circuit performs the boosting operation, the second switch means is switched (chopper) by the power supply control means with the first switch means turned on. Thus, the power supply circuit functions as a boost converter that boosts the input voltage supplied via the input power supply line and the reference power supply line and outputs the boosted voltage via the output power supply line and the reference power supply line. When the power supply circuit performs the step-down operation, the first switch means is switched by the power supply control means so that the detection value of the output voltage detection means becomes the step-down value in a state where the second switch means is turned off. (Chopper) The step-down value is a predetermined value lower than the input voltage value. As a result, the power supply circuit functions as a step-down converter that steps down the input voltage and outputs it. When the power supply circuit executes the power shutoff operation, the first switch means and the second switch means are turned off. As a result, the supply of the input voltage to the power supply circuit is cut off, and the new power supply to the drive means to which the output voltage is supplied is stopped.

  The power supply control unit controls the operation of the power supply circuit according to the detection value of the output voltage detection unit. Specifically, the power supply control means controls the operation of the power supply circuit so as to execute the step-down operation first. When the power supply circuit performs a step-down operation, the output voltage is stepped down to a step-down value lower than a normal voltage value (a voltage value substantially equal to the input voltage value).

  When the acceleration operation of the motor is started, the power consumption in the motor increases, so that the output voltage (detected value of the output voltage detecting means) gradually decreases from the steady value (in this case, the step-down value). When the acceleration operation of the motor is completed, the power consumption in the motor is reduced, so that the decrease in output voltage is reduced. In this means, paying attention to the relationship between the operation state of the motor and the output voltage, the acceleration operation period and other periods (non-operation period, constant speed operation period, deceleration operation period) are as follows: , The operating state of the power supply circuit is switched.

  That is, the power supply control means controls the operation of the power supply circuit so as to execute the boosting operation when the detection value of the output voltage detection means falls below a predetermined acceleration start determination value lower than the step-down value during the step-down operation. Note that the step-up operation is executed only for a period until the time point when the step-down operation is resumed (described later). As a result, the power supply circuit performs the boosting operation from the time when the acceleration operation is considered to have started. When the power supply circuit performs the boosting operation, an output voltage obtained by boosting the input voltage is supplied to the driving unit. Therefore, the driving unit can drive the motor by receiving a relatively high output voltage. Therefore, when the power supply circuit performs the boosting operation, it is possible to supply sufficient electric power to the motor to obtain a high torque. Thereby, for example, a high torque can be output even when the motor is rotating at high speed.

  At this time, the output voltage output from the power supply circuit is boosted by the boosting operation, but since the power consumption accompanying the acceleration operation of the motor is large, the rising slope becomes very gradual. Thereafter, when the acceleration operation of the motor is completed, the power consumption in the motor is reduced, and thus the output voltage is rapidly increased by the boosting operation. In view of the above, the power supply control means is configured to execute the step-down operation when the detected value of the output voltage detection means exceeds a predetermined acceleration end determination value higher than the input voltage value during the step-up operation. Control the operation of the circuit. As a result, the power supply circuit performs the step-down operation again from the time point when it is considered that the acceleration operation has been completed.

  The amount of energy that can be stored in the capacitor before the output voltage that rises due to regenerative energy (voltage across the capacitor) reaches the regenerative consumption voltage value when the motor decelerates while the power supply circuit is performing step-down operation Is larger by an amount corresponding to the difference between the normal voltage value and the step-down value than when the output voltage is set to a normal voltage value (conventional configuration). That is, by increasing the free capacity of the capacitor as compared with the conventional configuration, it is possible to store more energy in the capacitor during the deceleration operation.

  In this way, by reducing the output voltage to the step-down value, all the regenerative energy can be effectively used if the voltage across the terminals of the capacitor does not rise to the regenerative consumption voltage value during the deceleration operation. In addition, even when the voltage across the capacitor rises to the regenerative consumption voltage value during deceleration operation, the regenerative consumption circuit operation time can be shortened compared to when the output voltage is set to the normal voltage value. Energy consumed by the consumption circuit (waste energy) can be reduced, and the remaining regenerative energy can be used effectively.

  When the motor decelerates, the output voltage, which is the voltage across the capacitor, increases from the steady value (step-down value) due to regenerative energy from the motor. When the motor decelerates, the regenerative energy disappears, and the increase in output voltage is suppressed. In this means, paying attention to the relationship between the operation state of the motor and the output voltage, the operation state of the power supply circuit is switched during the deceleration operation period as follows.

  That is, the power supply control means controls the operation of the power supply circuit so as to execute the power supply cutoff operation when the detection value of the output voltage detection means rises during the step-down operation. As a result, the power supply circuit executes the power shutoff operation from the point in time when the deceleration operation is considered to have started. When the power supply circuit performs the power shut-off operation, the new power supply to the driving means is stopped, so that the increase in output voltage is alleviated. Thereby, the effect of effectively using the above-described regenerative energy is further enhanced. Thereafter, when the motor decelerates, the regenerative energy disappears, and the output voltage starts to decrease. Based on this, the power supply control means controls the operation of the power supply circuit so as to execute the step-down operation when the detection value of the output voltage detection means decreases during execution of the power shutoff operation. As a result, the power supply circuit performs the step-down operation again from the point in time when it is considered that the deceleration operation has been completed.

  As described above, the power supply control means steps down the output voltage lower than a normal voltage value (a voltage value substantially equal to the input voltage value) in a steady state (a period excluding a period during which acceleration operation is considered to be performed). The operation of the power supply circuit is controlled to step down to the value. As a result, the free capacity of the capacitor is increased as compared with the case where the output voltage is set to a normal voltage value, so that more energy can be stored in the capacitor during the deceleration operation. Further, the power supply control means controls to cut off the supply of the input voltage to the power supply circuit during the period during which the motor decelerates based on the detection value of the output voltage detection means. As a result, during the deceleration operation, new power supply to the drive means (and thus the motor) is stopped and the increase in output voltage is alleviated, so that the effect of effectively using regenerative energy is further enhanced.

  Further, the power supply control means controls the operation of the power supply circuit based on the detection value of the output voltage detection means so as to boost the output voltage during a period during which the motor performs an acceleration operation. As a result, an output voltage obtained by boosting the input voltage during the acceleration operation of the motor is supplied to the driving means, and sufficient power is obtained to obtain the high torque during the acceleration operation that essentially requires high torque. It can be supplied to the motor.

  Thus, according to this means, the operation state of the motor is indirectly determined from the detected value of the output voltage without directly determining the operation state of the motor, and based on the determination result, the power supply circuit The operating state is automatically switched as described above. Therefore, according to this means, sufficient power can be supplied to the motor during high torque operation without changing the control content of the drive control means for controlling the driving of the motor, and from the motor during the deceleration operation. The generated regenerative energy can be used effectively.

  According to the means described in claim 2, the abnormality detection means for detecting the abnormality of the motor is provided. The power supply circuit includes third switch means connected between one terminal of the inductor and the output power supply line. When an abnormality of the motor is detected by the abnormality detection means, or when an emergency stop command for giving an emergency stop command is given from the outside, the power supply control means applies a dynamic brake to the motor as follows. That is, the power control means turns off the first switch means, turns on the second switch means, and turns on the third switch means regardless of the operating state of the power supply circuit at that time. As a result, the motor phases are short-circuited via the third switch means, the inductor and the second switch means. In general, the switch means does not have a resistance value of zero even in the on state, has a predetermined resistance (on resistance), and the inductor has a predetermined equivalent series resistance.

  That is, the motor phases are short-circuited via a predetermined resistance, and the dynamic brake is applied to the motor. Usually, in order to apply a dynamic brake, it is necessary to provide a switch means and a resistor dedicated to the dynamic brake in series between the output power supply line and the reference power supply line. According to this means, it becomes possible to apply dynamic braking by using each switch means and inductor of the power supply circuit, so there is no need to provide switch means and resistors dedicated to dynamic brake, and the circuit configuration is simplified accordingly. And cost reduction can be achieved.

The electric block diagram of the robot system which shows one Embodiment of this invention A diagram schematically showing the configuration of the robot system Flow chart showing contents of operation control of regenerative consumption circuit Diagram showing rotation speed and bus voltage when performing a series of operations Block diagram equivalently showing the contents of motor control Flow chart showing control contents of power supply control unit Diagram showing bus voltage and switch status when performing a series of operations FIG. 7 equivalent diagram when dynamic brake control is executed

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 2 shows a system configuration of a general industrial robot. A robot system 1 shown in FIG. 2 includes a robot 2, a controller 3 that controls the robot 2, and a teaching pendant 4 connected to the controller 3.

  The robot 2 is configured as, for example, a 6-axis vertical articulated robot. The robot 2 includes a base 5, a shoulder unit 6 that is supported by the base 5 so as to be rotatable in the horizontal direction, a lower arm 7 that is supported by the shoulder unit 6 so as to be rotatable in the vertical direction, and a vertical movement by the lower arm 7. A first upper arm 8 rotatably supported, a second upper arm 9 twistably supported by the first upper arm 8, and a second upper arm 9 rotatably supported by the second upper arm 9 The wrist 10 and the flange 11 supported by the wrist 10 so as to be twisted and rotatable.

  The base 5, the shoulder portion 6, the lower arm 7, the first upper arm 8, the second upper arm 9, the wrist 10 and the flange 11 function as an arm of the robot 2. Although not, an end effector (hand) is attached. The base 5, the shoulder portion 6, the lower arm 7, the first upper arm 8, the second upper arm 9, the wrist 10 and the flange 11 function as an arm of the robot 2. Each arm (a plurality of axes) of the robot 2 is driven by a motor (indicated by a symbol M in FIG. 1) provided correspondingly. In the vicinity of each motor, a position detector (not shown) for detecting the rotational position of each rotating shaft is provided.

  The teaching pendant 4 is, for example, a size that can be operated by being carried by a user or carried by a hand, and is formed in, for example, a thin, substantially rectangular box shape. The teaching pendant 4 is provided with various key switches 12, and the user performs various input operations using the key switches 12. The teaching pendant 4 is connected to the controller 3 via a cable, and performs high-speed data transfer with the controller 3 via a communication interface. The teaching pendant 4 is input by operating the key switch 12. Information such as operation signals is transmitted from the teaching pendant 4 to the controller 3.

  FIG. 1 is a block diagram schematically showing an electrical configuration of the robot system. The robot 2 is provided with a plurality of motors M (only one is shown in FIG. 1) for driving each axis. The motor M is, for example, a brushless DC motor. The controller 3 includes a DC power supply circuit 21 that rectifies and smoothes AC supplied from the AC power supply 20, a regenerative consumption circuit 22, an inverter device 23 that drives the motor M, a current detection unit 24, a position detection unit 25, A power supply control unit 26 that controls the operation of the DC power supply circuit 21 and a main control unit 27 that controls these devices and the like are provided.

  The DC power supply circuit 21 includes a rectifier circuit 28, a step-up / step-down circuit 29, and a smoothing capacitor 30. The rectifier circuit 28 has a known configuration in which a diode is connected in the form of a bridge. The AC input terminal of the rectifier circuit 28 is supplied with each phase output of, for example, a three-phase 200V AC power supply 20. The DC output terminals of the rectifier circuit 28 are connected to the input power line 31 and the reference power line 32, respectively.

  The step-up / down circuit 29 (corresponding to a power supply circuit) includes transistors Q1 and Q2, an inductor L1, diodes D1 and D2, and a switch SW1. The transistor Q1 (corresponding to the first switch means) is an N-channel type power MOSFET, its drain is connected to the input power line 31 and its source is connected to one terminal of the inductor L1. The diode D1 (corresponding to the first diode) is connected between one terminal of the inductor L1 and the reference power supply line 32 with the reference power supply line 32 side as an anode. The transistor Q2 (corresponding to the second switch means) is an N-channel type power MOSFET, its drain is connected to the other terminal of the inductor L1, and its source is connected to the reference power line 32.

  The diode D2 (corresponding to the second diode) is connected between the other terminal of the inductor L1 and the output power supply line 33 with the other terminal side of the inductor L1 as an anode. The switch SW1 (corresponding to the third switch means) is a mechanical switch such as a relay, for example, and is connected between one terminal of the inductor L1 and the output power supply line 33. Note that the switch SW1 may be configured by a semiconductor switching element such as a power MOSFET or a bipolar transistor. A capacitor 30 is connected between the output power line 33 and the reference power line 32.

  The step-up / step-down circuit 29 performs any one of a step-up operation, a step-down operation, and a non-step-up / step-down operation. In the step-up operation, an input voltage (DC voltage output from the rectifier circuit 28) given through the input power supply line 31 and the reference power supply line 32 is boosted and output through the output power supply line 33 and the reference power supply line 32. It is. In the step-down operation, the input voltage is stepped down and output via the output power supply line 33 and the reference power supply line 32. The non-step-up / step-down operation is to output the input voltage via the output power supply line 33 and the reference power supply line 32 without increasing or decreasing the input voltage. Further, the step-up / step-down circuit 29 can be in a power-off state in which the supply of input voltage is cut off (power-off operation).

  Each operation by the step-up / step-down circuit 29 is switched according to the driving state of the transistors Q1, Q2 and the open / close state of the switch SW1. Driving of the transistors Q1 and Q2 and opening / closing of the switch SW1 are controlled by the power supply control unit 26. That is, in the present embodiment, the power supply control unit 26 corresponds to a power supply control unit that controls the operation of the step-up / step-down circuit 29.

  The power control unit 26 is mainly configured by a microcomputer including a CPU, a ROM, a RAM, an I / O, and the like. The power supply control unit 26 has a function as output voltage detection means for detecting the value of the bus voltage BV (output voltage) between the output power supply line 33 and the reference power supply line 32. The power supply control unit 26 having such a function controls the operation of the step-up / step-down circuit 29 according to the command signal given from the main control unit 27 and the detected value of the bus voltage BV.

When performing the boosting operation, the power supply control unit 26 switches (choppers) the transistor Q2 so that the detected value of the bus voltage BV becomes the boosted value BV _H with the switch SW1 turned off and the transistor Q1 turned on. . The boost value BV _H is a predetermined value higher than the value of the input voltage (for example, about 282 V). Thereby, the step-up / step-down circuit 29 functions as a boost converter that boosts and outputs the input voltage. However, even in the period in which buck circuit 29 is executing the step-up operation, the acceleration operation period of the motor M to be described later, the bus voltage BV is lower than the boost value BV _H.

Power control unit 26, when executing the step-down operation, while turning off the switch SW1 and the transistor Q2, switching (chopper) the transistor Q1 so that the detected value of the bus voltage BV is buck value BV _L. Incidentally, the step-down value BV _L is lower than the value of the input voltage, and may be a minimum required voltage value for driving the motor M, a DC power supply circuit 21, the motor M, the specifications such as the inverter device 23 What is necessary is just to change suitably according to it. Thereby, the step-up / step-down circuit 29 functions as a step-down converter that steps down the input voltage and outputs it. However, the buck-boost circuit 29 is a period for running the step-down operation, the period during which the regenerative energy to be described later occurs, the bus voltage BV is higher than the step-down value BV _L.

When performing the non-step-up / step-down operation, the power supply control unit 26 turns off the switch SW1 and the transistor Q2 and turns on the transistor Q1. Thereby, the step-up / step-down circuit 29 outputs the input voltage without boosting or stepping down. The output voltage (bus voltage BV) at this time is input by the sum of the voltage drop due to the ON resistance of the transistor Q1 (resistance in the ON state) and the equivalent series resistance of the inductor L1, and the forward voltage of the diode D2. the normal value BV _M is lower than the voltage.

  The power supply control unit 26 turns off both the switch SW1 and the transistors Q1 and Q2 when the step-up / step-down circuit 29 is turned off (execution of power supply cut-off). As a result, the supply of the input voltage to the step-up / step-down circuit 29 is cut off, and the new power supply to the inverter device 23 to which the output voltage (bus voltage BV) is supplied is stopped.

  The power supply control unit 26 automatically switches the operation states of the step-up / step-down circuit 29 based on the detected value of the bus voltage BV. That is, based on the detected value of the bus voltage BV, the power supply control unit 26 performs a boosting operation during a period in which the motor M is determined to be in the acceleration operation state, and in a period in which it is determined to be in the deceleration operation state. Performs a power-off operation and controls the operation of the step-up / step-down circuit 29 so as to generally perform a step-down operation during the periods other than those periods (details will be described later).

  The power supply control unit 26 has a function (dynamic brake control) for controlling the operation of the step-up / step-down circuit 29 so as to apply a dynamic brake to the motor M. When an emergency stop command for commanding an emergency stop of the motor M is given from the outside, a command indicating that the dynamic brake is to be turned on is given from the main control unit 27 to the power supply control unit 26. In response to this, the power supply control unit 26 controls the operation of the step-up / step-down circuit 29 as follows. That is, regardless of the control mode set at that time, the power supply control unit 26 drives the transistor Q1 off, drives the transistor Q2 on, and turns on the switch SW1.

  Although details will be described later, the dynamic brake is applied to the motor M by such control. When the controller 3 is configured to include an abnormality detection means (not shown) for detecting an abnormality of the motor M, when the abnormality of the motor M is detected by the abnormality detection means, the main control unit 27 The power supply control unit 26 may be configured to apply the above-described command and execute the above-described control to apply a dynamic brake to the motor M.

  The regenerative consumption circuit 22 is configured by connecting a series circuit of a regenerative resistor R1 and a transistor Q3 (corresponding to regenerative switch means) between the output power line 33 and the reference power line 32. The transistor Q3 is an N-channel type power MOSFET, and its on / off is controlled by the power supply control unit 26. That is, in the present embodiment, the power control unit 26 corresponds to a regeneration control unit that controls the operation of the regeneration consumption circuit 22.

FIG. 3 shows the contents of operation control of the regeneration consumption circuit 22 by the power supply control unit 26. The power supply control unit 26 is configured to execute the control shown in FIG. 3 at predetermined intervals. First, the power supply control unit 26 refers to the bus voltage BV (detected value) at that time (step A1). Subsequently, the power control unit 26, reference bus voltage BV determines whether a regenerative voltage consumption value BV _R above (step A2). In the case the bus voltage BV is regenerative voltage consumption value BV _R or (YES), and ON driving the transistor Q3 (the transistor step A3), the control is ended. On the other hand, when the bus voltage BV is less than the regenerative voltage consumption value BV _R (NO), and OFF drive the transistor Q3 (the transistor step A4), the control is ended. In step A3 or A4, if the transistor Q3 is already turned on or off, the control is terminated while maintaining the state.

FIG. 4 shows the rotational speed of the motor M and the bus voltage when the robot performs a series of operations of acceleration, constant speed, and deceleration. As shown in FIG. 4, the bus voltage BV increases due to energy regenerated from the motor M (regenerative energy) during the deceleration operation. When the bus voltage BV is about to exceed the regenerative voltage consumption value BV _R, so that the regenerative energy by flowing current to the regenerative resistor R1 is discharged as heat energy, bus voltage BV is less than the regenerative voltage consumption value BV _R The voltage rise is suppressed.

Regenerative voltage consumption value BV _R, each circuit element (the switching elements of the inverter device 23, such as a capacitor 30 of the DC power supply circuit 21) connected to the output power supply line 33 and the reference power supply line 32 bus voltage BV exceeds the rating of the A value that does not increase may be set. Further, the regenerative voltage consumption value BV _R, boost value BV _H, normal value BV _M and antihypertensive value BV _L may be set so as to satisfy the following relationship (1).
BV _R > BV _H > BV _M > BV _L (1)

  The transistor Q3 as the regenerative switch means is not limited to the power MOSFET, and may be constituted by other semiconductor switching elements such as a bipolar transistor. The regenerative switch means may be constituted by a mechanical switch such as a relay, for example.

  The inverter device 23 (corresponding to driving means) is an inverter configured by connecting six switching elements such as IGBTs (only two are shown in FIG. 1) between the output power supply line 33 and the reference power supply line 32 in a three-phase full bridge. Six sets of main circuits and their drive circuits are provided (only one set is shown in FIG. 1). A free-wheeling diode is connected between the collector and emitter of the IGBT. The gate signal is given to the gate of the IGBT from the drive circuit. The drive circuit drives each IGBT by outputting a gate signal (PWM signal) that is pulse-width modulated based on a command signal (energization command Sc) given from the main control unit 27.

  The main control unit 27 (corresponding to drive control means) is configured mainly with a microcomputer including a CPU, a ROM, a RAM, an I / O, and the like. The current detection unit 24 converts a detection signal from a current detector (not shown) that detects a current flowing through the motor M into data that can be input to the main control unit 27 and outputs the data. The position detector 25 converts a detection signal from a position detector (not shown) that detects the rotational position of the motor M into data that can be input to the main controller 27 and outputs the data. The main control unit 27 acquires the value of the current flowing through the motor M based on the data output from the current detection unit 24, and the rotational position and rotational speed of the motor M based on the data output from the position detection unit 25. To get. Although the details will be described later, the main control unit 27 performs feedback control of driving of the motor M by the inverter device 23 using the current value, the rotation position, and the rotation speed acquired in this way. The main control unit 27 outputs various command signals to the power supply control unit 26.

  FIG. 5 is a block diagram equivalently showing the contents of motor control in the robot system 1. As shown in FIG. 5, the main control unit 27 includes a position control unit 41, a speed control unit 42, and a current control unit 43. In FIG. 5, only the configuration related to the control of one motor M is shown, but actually the same configuration is provided for each of all the motors M. In general, an industrial robot operates according to a predetermined operation program created by performing teaching or the like in advance. A host control unit (not shown) interprets the operation program and outputs a command value (position command pref) for controlling each motor M to the position control unit 41 so that the robot 2 performs an operation according to the operation program. To do.

  The position control unit 41 obtains a deviation of the current rotational position p * with respect to the position command pref given from the host control unit, and a speed command vref (rotation) so that the output (deviation) of the subtractor 45 approaches zero. And a position control amplifier 46 that outputs (corresponding to a speed command). The gain of the position control amplifier 46 is Kp. The speed controller 42 includes a differentiator 47, a subtractor 48, and a speed control amplifier 49. The differentiator 47 differentiates the current rotational position p * and converts it to the current rotational speed v *. The subtractor 48 obtains the deviation of the current rotational speed v * from the speed command vref. The speed control amplifier 49 outputs a current command iref so that the output (deviation) of the subtracter 48 approaches zero. The gain of the speed control amplifier 49 is Kv.

  The current control unit 43 obtains a deviation of the current i * flowing through the current motor M with respect to the current command iref, and a command signal (energization) to the inverter device 23 so that the output (deviation) of the subtractor 50 approaches zero. And a current control amplifier 51 that outputs a command Sc). The gain of the current control amplifier 51 is Ki. With such a configuration, the main control unit 27 performs current feedback control, speed feedback control, and position feedback control, and feedback controls the drive of the motor M to control the operation of the arm of the robot 2.

Next, the operation and effect of this embodiment will be described.
The power supply control unit 26 indirectly determines the operation state (acceleration operation state, deceleration operation state) of the motor M based on the detected value of the bus voltage BV. Here, it is assumed that the acceleration operation period and the deceleration operation period of all the motors M are substantially the same. However, there are usually more cases where this assumption is not satisfied. In this case, it is only necessary to determine the operating state of the motor M that operates at the highest acceleration among all the motors M.

  FIG. 6 is a flowchart showing the control content of the power supply control unit 26. FIG. 7 shows the rotational speed of the motor M, the bus voltage, the drive state of the transistors Q1 and Q2, and the open / close state of the switch SW1 when a series of operations (acceleration, constant speed, and deceleration) of the robot 2 are performed. Yes. When the operation control of the step-up / step-down circuit 29 shown in FIG. 6 is performed, the power supply control unit 26 also executes the operation control of the regeneration consumption circuit 22 shown in FIG. 3 at predetermined intervals.

  When the controller 3 is turned on, the power supply control unit 26 performs an initial setting to place the step-up / step-down circuit 29 in a power-off state (step S1). That is, the transistors Q1 and Q2 are turned off and the switch SW1 is turned off. Therefore, at this stage, the input / output voltage is not yet supplied to the step-up / step-down circuit 29 (power supply cutoff state).

In the subsequent step S2, the transistor Q1 is turned on (time ta in FIG. 7). Accordingly, the bus voltage BV, which is output from the buck-boost circuit 29 rises toward the normal value BV _M. An inrush current flows from the AC power supply 20 to the DC power supply circuit 21 at the moment when the transistor Q1 is turned on, but the inrush current is limited by the on-resistance of the transistor Q1 and the equivalent series resistance of the inductor L1.

Thereafter, when a predetermined time has elapsed ( "YES" in step S3), and from that point (time tb in Fig. 7), the transistor Q1 is switched so that the detected value of the bus voltage BV is buck value BV _L (step S4). Accordingly, the bus voltage BV, which is output from the buck-boost circuit 29 is stepped down from the normal value BV _M to buck value BV _L. Then, in the subsequent time when the bus voltage BV has reached the step-down value BV _L, acceleration operation of the motor M is started.

When the acceleration operation of the motor M is started, the power consumption in the motor M increases, so that the bus voltage BV gradually decreases from the steady value (in this case, the step-down value BV _L ). Thereafter, when the acceleration operation of the motor M is completed, the operation is normally shifted to the constant speed operation, so that the power consumption in the motor M is reduced and the decrease in the bus voltage BV is suppressed. In the present embodiment, paying attention to the relationship between the operation state of the motor M and the bus voltage BV, the acceleration operation period of the motor M is determined based on the detected value of the bus voltage BV as follows.

That is, in step S5, it is determined whether or not the detected value of the bus voltage BV is less than the acceleration start determination value V _AS . In step S5, in order to prevent an erroneous determination when the bus voltage BV fluctuates due to the influence of noise or the like, the detected value of the bus voltage BV is determined to start acceleration continuously a predetermined number of times (or a predetermined time). If it is less than the value V _AS , “YES” is determined.

Acceleration start determination value V _AS may be appropriately changed as long as a value lower than the step-down value BV _L. Note that as the acceleration start determination value V _AS is set higher, from the time when the acceleration operation is actually started (time tc in FIG. 7) to the time when “YES” is determined in step S5 (time td in FIG. 7). The delay time Ta becomes shorter. That is, the higher the acceleration start determination value V _AS is set, the higher the determination accuracy at the time when the acceleration operation of the motor M starts. However, in this case, the possibility of erroneous determination due to noise or the like increases. On the other hand, the lower the acceleration start determination value V _AS is, the longer the delay time is. That is, the lower the acceleration start determination value V _AS is set, the lower the determination accuracy at the start of the acceleration operation of the motor M is. However, in this case, the possibility of erroneous determination due to noise or the like is reduced.

If it is determined that the detected value of the bus voltage BV is less than the acceleration start determination value V _AS (“YES” in step S5, time td in FIG. 7), the process proceeds to step S6. In step S6, the transistor Q2 is switched so that the detected value of the bus voltage BV becomes the boosted value BV _H while the transistor Q1 is turned on. As a result, the bus voltage BV output from the step-up / step-down circuit 29 is boosted from the step-down value BV _L toward the step-up value BV _H. Therefore, the inverter device 23 drives the motor M by receiving a relatively high bus voltage BV compared to the conventional configuration in which the voltage output from the rectifier circuit 28 is supplied to the inverter device as it is. Therefore, the inverter device 23 can supply sufficient power to the motor M to obtain a high torque during the acceleration operation period. As a result, for example, high torque can be output even when the motor M is rotating at high speed.

At this time, the bus voltage BV output from the step-up / step-down circuit 29 is boosted by the boosting operation, but due to the increase in power consumption accompanying the acceleration operation of the motor M, the rising slope becomes very gentle ( Time td to te in FIG. Therefore, the bus voltage BV does not rise to the boost value BV _H during the acceleration operation period of the motor M. In other words, it is necessary to set the boosted value BV _H to a value that satisfies such a condition in consideration of the specifications of the device.

After that, when the acceleration operation of the motor M is completed, the operation shifts to a constant speed operation, so that power consumption in the motor M is reduced (time te in FIG. 7). As a result, the bus voltage BV increases rapidly due to the boosting operation. Therefore, in step S7, it is determined whether or not the detected value of the bus voltage BV has reached the boost value BV _H. In the present embodiment, the boost value BV _H corresponds to an acceleration end determination value for determining the end point of the acceleration operation. If it is determined that the detected value of the bus voltage BV has reached the boost value BV _H (“YES” in step S7, time tf in FIG. 7), the process proceeds to step S8. In step S8, the transistor Q2 is in a state of being off-drive, transistor Q1 is switched so that the detected value of the bus voltage BV is buck value BV _L. Accordingly, the acceleration operation results in the buck circuit 29 from the time that is considered to be finished executing the step-down operation again, the bus voltage BV decreases toward the buck value BV _L.

  When step S8 is executed, the transistor Q2 is first turned off, and then the switching of the transistor Q1 is started. The reason is that when switching of the transistor Q1 is started first, the transistors Q1 and Q2 may be turned on simultaneously. Then, an energization path that short-circuits the input power supply line 31 and the reference power supply line 32 through the transistors Q1 and Q2 and the rectifier circuit 28 is formed. In such a case, an excessive current flows through the transistors Q1 and Q2 and the rectifier circuit 28, and in the worst case, a failure may be caused. In order to prevent such a situation, the transistor Q2 is reliably turned off as described above, and then the switching of the transistor Q1 is started.

In this state, with the step-up / step-down circuit 29 performing the step-down operation, the motor M is operated at a constant speed, and then the deceleration operation is performed. When the deceleration operation is started, the bus voltage BV is stepped down to a lower step-down value BV _L than the normal value BV _M. Therefore, during deceleration of the motor M, the amount of energy which can be stored in the capacitor 30 until the bus voltage BV (inter-terminal voltage of the capacitor 30) reaches the regenerative voltage consumption value BV _R to increase the regenerative energy, the bus voltage BV is compared to when the normal value BV _M (the case of the conventional configuration), increased by the amount of energy J _C shown in the following equation (2).
J _C = {(1/2) · C · BV _M ² } − {(1/2) · C · BV _L ² }
= (1/2) · C · ( BV M 2 -BV L 2) ... (2)

As shown in equation (2) above, the amount of energy which can be stored in the capacitor 30 is larger by an amount J _C in accordance with the difference between the normal value BV _M and the step-down value BV _L. That is, by increasing the free capacity of the capacitor 30 as compared with the conventional configuration, more energy can be stored in the capacitor 30 during the deceleration operation.

Thus, by reducing the bus voltage BV to buck value BV _L, if the voltage across the terminals of the capacitor 30 rises to the regenerative voltage consumption value BV _R during deceleration operation, can be effectively utilized all regenerative energy . Further, even when the terminal voltage of the capacitor 30 during the deceleration is increased to regenerative voltage consumption value BV _R, as compared with the conventional configuration bus voltage BV is a normal value BV _M, the operation time of the regenerative consumption circuit 22 Since it can be shortened, the energy consumed by the regeneration consumption circuit 22 (waste energy) can be reduced, and the remaining regeneration energy can be used effectively.

Now, when the deceleration of the motor M is started, the bus voltage BV is a terminal voltage of the capacitor 30 due to regenerative energy from the motor M is increased from the step-down value BV _L. Then, when the deceleration operation of the motor M is completed, the regeneration of energy from the motor M is stopped, so that the increase of the bus voltage BV is stopped. In the present embodiment, paying attention to the relationship between the operation state of the motor M and the bus voltage BV, the deceleration operation period of the motor M is determined based on the detected value of the bus voltage BV as follows.

  That is, in step S9, it is determined whether or not the detected value of the bus voltage BV is increasing. Here, for example, when the determination that the detected value of the bus voltage BV is higher than the previously referred value is N times (N is an integer), it is determined that the bus voltage BV tends to increase. Like to do. The value of N can be changed as appropriate. However, as the value is decreased, the time when “YES” is determined in step S9 from the time when the deceleration operation is actually started (time tg in FIG. 7) (in FIG. 7). The delay time Tb until time th) is shortened. That is, the smaller the value of N, the higher the determination accuracy at the start of the deceleration operation of the motor M. However, in this case, the possibility of erroneous determination due to noise or the like increases. On the other hand, as the value of N is increased, the determination accuracy at the start of the deceleration operation of the motor M is lowered. However, in this case, the possibility of erroneous determination due to noise or the like is reduced.

  If it is determined that the detected value of the bus voltage BV is increasing (“YES” in step S9, time th in FIG. 7), the process proceeds to step S10. In step S10, the transistor Q1 is driven off. As a result, the step-up / step-down circuit 29 enters the power shut-off state from the time point when the deceleration operation is considered to have started. Therefore, new power supply to the inverter device 23 is stopped, and the rise of the bus voltage BV is alleviated. That is, since the rising slope of the bus voltage BV becomes gentle, the peak value of the bus voltage BV during the deceleration operation period can be kept low. By doing in this way, the effect of using the above-mentioned regenerative energy effectively further increases.

  Thereafter, when the deceleration operation of the motor M is completed, the regeneration of energy from the motor M is stopped, so that the bus voltage BV starts to decrease (time ti in FIG. 7). Therefore, in step S11, it is determined whether or not the detected value of the bus voltage BV is decreasing. The determination of the decreasing tendency in step S11 can be performed by the same method as the determination of the increasing tendency in step S9, for example.

If it is determined that the detected value of the bus voltage BV is decreasing ("YES" in step S11, time tj in FIG. 7), the process proceeds to step S12. In step S12, the transistor Q1 is switched so that the detected value of the bus voltage BV is buck value BV _L. Thereby, the step-up / step-down circuit 29 starts the step-down operation again from the time point when the deceleration operation is considered to be completed. After execution of step S12, the process returns to step S5, and the step-down operation is continued until it is determined that the next acceleration operation is started (during “NO” in step S5).

As described above, the power control unit 26, in the steady state (period excluding the period considered to be accelerating operation period and deceleration period), lower buck value than the normal value BV _M of the normal bus voltage BV BV _The operation of the step-up / step-down circuit 29 is controlled so as to execute a step-down operation that steps down to _L. Thus, compared to the bus voltage BV when the normal value BV _M (conventional configuration), the amount of energy which can be stored in the capacitor 30 becomes larger by an amount shown in equation (2). That is, since the free capacity of the capacitor 30 is increased as compared with the conventional configuration, it is possible to store more energy as electrostatic energy in the capacitor 30 during the deceleration operation of the motor M. The power supply control unit 26 determines the deceleration operation period of the motor M based on the detected value of the bus voltage BV, and controls the operation of the step-up / step-down circuit 29 so that the power supply is cut off during that period. As a result, during the deceleration operation period of the motor M, new power supply to the inverter device 23 (and thus the motor M) is stopped and the rise of the bus voltage BV is alleviated, so that the effect of effectively using regenerative energy is further enhanced.

  Further, the power supply control unit 26 determines the acceleration operation period of the motor M based on the detected value of the bus voltage BV, and during that period, the boosting / lowering circuit 29 performs a boosting operation to boost the bus voltage BV. Control the behavior. As a result, the bus voltage BV boosted during the acceleration operation of the motor M is supplied to the inverter device 23, and sufficient electric power is obtained to obtain the high torque during the acceleration operation that essentially requires high torque. Can be supplied to the motor M.

  Thus, according to the present embodiment, the operation state (acceleration operation state, deceleration operation state) of the motor M is indirectly determined from the detected value of the bus voltage BV without directly determining the operation state of the motor M. The operation state of the step-up / step-down circuit 29 is automatically switched as described above based on the determination result. Therefore, the control content of the power supply control unit 26 can be simplified. In addition, the above-described operations and effects can be obtained without changing the control content of the main control unit 27 that controls the driving of the motor M.

  In general, the power supply control unit 26 that performs control related to the power supply and the main control unit 27 that performs control related to driving of the motor M are developed by different persons (groups in charge). According to the present embodiment, the control content of the power supply control unit 26 may be changed without changing the control content of the main control unit 27, and therefore, there are fewer improvements related to control (software) from the conventional configuration. Therefore, software development is facilitated and the development cost can be suppressed.

  In addition, in order to limit the inrush current when the power is turned on, the power supply circuit is provided with a resistor for limiting the inrush current so as to be interposed in series with the input line of the power supply, and switch means for short-circuiting between the terminals of the resistor (For example, a mechanical relay or the like) is generally provided. On the other hand, according to the present embodiment, the inrush current is limited by the configuration (transistor Q1, inductor L1) that is essentially required for the step-up / step-down circuit 29 to perform the step-up / step-down operation. For this reason, it is not necessary to provide the inrush current limiting resistor and the switch means, and accordingly, the circuit configuration can be simplified and the manufacturing cost can be reduced.

  Furthermore, the power supply circuit is generally provided with an electromagnetic contactor (contactor) or the like so as to be interposed in series in the power supply path from the AC power supply to the DC power supply circuit so that the power supply can be cut off. In this embodiment, since it can set to the power-supply-shutdown state which interrupts | blocks supply of the input voltage with respect to the pressure | voltage rise / fall circuit 29, it is possible to abbreviate | omit the electromagnetic contactor. If an electromagnetic contactor or the like is omitted, the circuit configuration can be simplified correspondingly and the manufacturing cost can be reduced.

  Next, dynamic brake control by the power supply control unit 26 will be described. FIG. 8 shows the rotational speed of the motor M, the bus voltage, the drive state of the transistors Q1 and Q2, and the open / close state of the switch SW1 when the dynamic brake control is executed. Here, a case where dynamic brake control is performed during a period in which the motor M is operating at a constant speed will be described.

  When an emergency stop command is given at the time ta in FIG. 8, the power supply control unit 26 drives the transistor Q1 off and drives the transistor Q2 on regardless of the control mode set at that time. Further, the switch SW1 is turned on. As a result, the phases of the motor M are short-circuited via the switch SW1, the inductor L1, and the transistor Q2.

  The switch SW1 has a predetermined resistance value even in the on state. The inductor L1 has a predetermined equivalent series resistance. Further, the transistor Q2, which is a power MOSFET, has a predetermined on-resistance. For this reason, the phases of the motor M are short-circuited via the resistance when the switch SW1 is on, the equivalent series resistance of the inductor L1, and the on-resistance of the transistor Q2, and dynamic braking is applied to the motor M. As a result, the rotation speed of the motor M decreases rapidly and stops at the time tb in FIG. At this time, since the transistor Q1 is turned off, the bus voltage BV also decreases abruptly similarly to the rotation speed, and becomes zero at the time tb.

  Usually, in order to apply the dynamic brake, it is necessary to provide a switch means and a resistor dedicated to the dynamic brake in series between the power supply lines supplying the bus voltage BV (between the output power supply line 33 and the reference power supply line 32). On the other hand, according to the present embodiment, when the power supply control unit 26 performs the dynamic brake control described above, the dynamic brake can be applied using the switch SW1, the inductor L1, and the transistor Q2 of the step-up / down circuit 29. It becomes. For this reason, there is no need to provide a switch means and a resistor dedicated to the dynamic brake, the circuit configuration can be simplified correspondingly, and the manufacturing cost can be reduced.

The present invention is not limited to the embodiment described above and illustrated in the drawings, and the following modifications or expansions are possible.
What is necessary is just to provide about dynamic brake control by the power supply control part 26 as needed. When the dynamic brake control is not provided, the switch SW1 can be omitted.
The power supply control unit 26 may be configured to turn on the transistor Q1 and the switch SW1 and turn off the transistor Q2 when performing the non-step-up / step-down operation. In this way, the output voltage (bus voltage BV) during the non-boosting operation becomes a value lower than the input voltage by the voltage drop due to the resistance when the switch SW1 is on. And the effect of reducing the power loss by the inductor L1 and the diode D2 is acquired.

The present invention is not limited to a configuration using a DC brushless motor as the motor M, and can also be applied to a configuration using various motors such as a DC motor and an AC motor. In the case where a DC motor is used as the motor M, as a driving means for driving the motor M, for example, a driving circuit mainly composed of an H bridge circuit may be used instead of the inverter device 23.
In the above-described embodiment, the example in which the present invention is applied to the six-axis vertical articulated robot 2 has been described. However, the present invention can be applied to all robots configured to drive each axis by a motor.

  In the drawings, 1 is a robot system, 2 is a robot, 22 is a regeneration consumption circuit, 23 is an inverter device (drive means), 26 is a power supply control unit (output voltage detection means, regeneration control means, power supply control means), 27 is a main Control unit (drive control means), 29 is a step-up / step-down circuit (power supply circuit), 30 is a capacitor, 31 is an input power supply line, 32 is a reference power supply line, 33 is an output power supply line, D1 is a first diode, and D2 is a first diode 2, diode L1, inductor, M motor, Q1 transistor (first switch means), Q2 transistor (second switch means), Q3 transistor (regeneration switch means), R1 regenerative resistor, SW1 A switch (third switch means) is shown.

Claims (2)

A motor for driving each axis of the robot;
Boosting operation for boosting an input voltage applied via an input power supply line and a reference power supply line and outputting the boosted voltage via an output power supply line and the reference power supply line, and stepping down the input voltage for the output power supply line and the reference power supply A power supply circuit that selectively executes a step-down operation that is output via a line and a power-off operation that cuts off the supply of the input voltage;
A capacitor connected between the output power line and the reference power line;
Driving means for operating the motor by receiving supply of an output voltage given via the output power line and the reference power line; and
Drive control means for controlling the drive of the motor by the drive means so as to match the rotation speed of the motor with a rotation speed command;
Output voltage detection means for detecting the output voltage;
A regenerative consumption circuit comprising regenerative switch means and a regenerative resistor provided in series between the output power supply line and the reference power supply line;
When the detection value of the output voltage detection means is less than the regeneration consumption voltage value, the regeneration switch means is turned off, and when the detection value is equal to or greater than the regeneration consumption voltage value, the regeneration switch means is turned on. Regeneration control means;
Power control means for controlling the operation of the power supply circuit according to the detection value of the output voltage detection means,
The power supply circuit is
Inductor, first switch means connected between the input power line and one terminal of the inductor, the reference power line side connected as an anode between the one terminal of the inductor and the reference power line A first diode that is connected, a second switch means connected between the other terminal of the inductor and the reference power supply line, and a second switch means connected between the other terminal of the inductor and the output power supply line. A second diode connected with the other terminal side as an anode,
The step-up operation is performed by switching the second switch means in a state where the first switch means is turned on,
With the second switch means turned off, the first switch means is switched so that the detection value of the output voltage detection means becomes a predetermined step-down value lower than the value of the input voltage. The step-down operation is performed,
When the first switch means and the second switch means are turned off, the power shutoff operation is executed,
The power control means includes
Controlling the operation of the power supply circuit to perform the step-down operation first,
During the step-down operation, when the detection value of the output voltage detection means falls below a predetermined acceleration start determination value lower than the step-down value, the operation of the power supply circuit is controlled to execute the step-up operation,
During the step-up operation, when the detected value of the output voltage detection means exceeds a predetermined acceleration end determination value higher than the input voltage value, the operation of the power supply circuit is controlled to execute the step-down operation,
During the step-down operation, when the detection value of the output voltage detection means rises, the operation of the power supply circuit is controlled to execute the power-off operation,
A robot system that controls the operation of the power supply circuit so as to execute the step-down operation when the detection value of the output voltage detecting means decreases during the power-off operation. Comprising an abnormality detection means for detecting an abnormality of the motor;
The power supply circuit includes third switch means connected between one terminal of the inductor and the output power supply line,
When the abnormality of the motor is detected by the abnormality detection means, or when an emergency stop command for giving an emergency stop command is given from the outside, the first switch means is turned off regardless of the operating state of the power supply circuit. At the same time, the second switch means is turned on, and further the third switch means is turned on, whereby the phases of the motor are short-circuited via the third switch means, the inductor, and the second switch means. The robot system according to claim 1, wherein:

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