JP2012125844A - Method and program for adjusting control loop gain of servo amplifier, and robot controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize a control loop in a simple control to a change of a power supply voltage of a servo amplifier during an operation of a robot.SOLUTION: A method of adjusting a control loop gain of the servo amplifier is provided for forming a control loop by feeding back a control amount of a servomotor according to a control command from outside to the servomotor provided in each joint of the robot. The method includes the steps of: forming the control loop, and starting driving of the servomotor, based on a default value of the control loop gain and a default one of the power supply voltage of the servo amplifier; detecting the power supply voltage of the servo amplifier; and adjusting a control loop gain changing correlating with the power supply voltage of the servo amplifier out of control gains constituting the control loop gain, so as to change in the opposite direction from the change of the detected power supply voltage of the servo amplifier.

Description

  The present invention relates to a servo amplifier control loop gain adjustment method, a program, and a robot control apparatus.

  The robot has a tool member attached to the distal end portion of the robot arm, and is configured to be able to rotate around the respective rotation axes of the plurality of arm members constituting the robot arm independently of each other. The robot controller that controls the operation of the robot stops the tool member at a desired position in a desired posture by position servo control of each rotation axis of the plurality of arm members, or speed servo of each rotation axis of the plurality of arm members. The tool member is configured to move along a desired path in a desired posture and at a desired speed by the control. Furthermore, the robot controller is configured to perform current servo control for controlling the amount of current flowing in each phase of the servo motor provided on each axis. As specific examples of these servo controls, for example, there are techniques described in Patent Documents 1 to 3 shown below.

  In Patent Document 1, a power supply device for a robot that rectifies three-phase alternating current with an active filter and smoothes and outputs the electric power of the rectified waveform to direct current with a smoothing capacitor, and the voltage between both terminals of the smoothing capacitor is constant. And a control circuit for the power supply apparatus that controls the power supply.

  Patent Document 2 discloses a position control unit that outputs a speed command signal based on a position command signal, a speed control unit that outputs a current value setting command signal based on the speed command signal of the position control unit, A current control unit that controls the current of the servo motor based on the setting command signal of the control unit, and detects the current, rotation speed, and rotation position of the servo motor, and feeds back these detection values to It is disclosed that the robot control apparatus that controls the driving includes a gain switching unit that outputs a switching command signal for switching the gains of the position control unit, the speed control unit, and the current control unit as necessary.

  Patent Document 3 discloses an input voltage measurement method for measuring a power supply voltage input to a servo amplifier, and a control gain setting method for setting a control gain of a servo amplifier based on the measured input voltage.

JP-A-8-251922 Japanese Patent Laid-Open No. 1-255015 Japanese Patent Laid-Open No. 8-205569

  By the way, when servo control that consumes a large amount of power is performed, such as when a workpiece is lifted by acceleration of the robot arm or a tool member at the tip of the robot arm, the power supplied from the commercial power supply is consumed by the servo motor of each axis. The power supply voltage (for example, the voltage between the smoothing capacitors in Patent Document 1) supplied from the power supply unit of the robot to the motor drive circuit may not be in time. If the power supply voltage is reduced in this way, there arises a problem that the response in the current servo control is delayed.

  On the other hand, when the servo control is performed with the regenerative operation in which the servo motor operates as a generator, such as when the workpiece is lowered by the robot arm's deceleration or the tool member at the tip of the robot arm, the regenerative power cannot be consumed due to the regenerative resistance. The power supply voltage may increase. When the power supply voltage increases in this way, the current loop gain of the current servo control increases, which causes a problem that vibrations or abnormal noises occur in the servo motor.

  The above problem applies not only to the current loop gain but also to the overall control loop gain (position velocity loop gain, velocity loop gain, etc.) of the servo amplifier.

  In Patent Document 1, an attempt is made to make the voltage between the smoothing capacitors of the power supply device constant in consideration of the load variation of the robot, but it is necessary to add new hardware (control circuit) for this control. .

  In Patent Document 2, the gains of the position control unit, speed control unit, and current control unit are switched to high values when moving between workpieces, and are switched to low values when an attractive force or a pressing force is applied between the workpiece and the hand. However, there is no suggestion or disclosure about the fluctuation of the power supply voltage during the robot operation as described above.

  In Patent Document 3, the control gain of the servo amplifier is set based on the measured input voltage in consideration of the fact that there is a certain range in the allowable input voltage of the servo amplifier. It does not take into account fluctuations in the power supply voltage. Further, in setting the control gain of the servo amplifier, the power supply voltage estimated from the reactive current component ratio of the phase current of the servo motor is used, and complicated control is required.

  The present invention has been made to solve the above-described conventional problems, and aims to stabilize a control loop with simple control against fluctuations in the power supply voltage of a servo amplifier during robot operation. To do.

  In order to achieve the above object, a control loop gain adjustment method for a servo amplifier according to the present invention provides a control amount of the servo motor corresponding to a control command from the outside to a servo motor provided at each joint of the robot. A control loop gain adjustment method for a servo amplifier that forms a control loop by feeding back, forming the control loop based on a default value of the control loop gain and a default value of a power supply voltage of the servo amplifier, and A step of starting drive of the servo motor, a step of detecting a power supply voltage of the servo amplifier, and a step of adjusting the control loop gain so as to change in the opposite direction to the detected change of the power supply voltage of the servo amplifier. Are provided.

  According to this method, even if the power supply voltage of the servo amplifier fluctuates while the servo motors provided at each joint of the robot are being driven (during robot operation), control is performed in the opposite direction to the change in the power supply voltage of the servo amplifier. Since the loop gain changes, the control loop can be stabilized.

  In the servo amplifier control loop gain adjustment method, the control loop includes a current loop formed by feeding back the current of the servo motor, and the step of adjusting the control loop gain includes the gain of the entire current loop. The proportional gain included in the current loop gain may be adjusted.

  According to this method, the current loop can be stabilized with simple control against fluctuations in the power supply voltage of the servo amplifier.

  The servo amplifier control loop gain adjustment method may further include a step of limiting the detected power supply voltage of the servo amplifier within a range from an upper limit value to a lower limit value.

  According to this method, the current loop can be further stabilized by simple control.

  The servo amplifier control loop gain adjustment method may further include a step of limiting the adjusted control loop gain within a range from an upper limit value to a lower limit value.

  According to this method, the current loop can be further stabilized by simple control.

  The servo amplifier control loop gain adjustment method may include a step of filtering the detected power supply voltage of the servo amplifier or the adjusted control loop gain.

According to this method, the current loop can be further stabilized by simple control.
In order to achieve the above object, another control loop gain adjustment program of a servo amplifier according to the present invention is provided for controlling a servo motor according to a control command from the outside with respect to a servo motor provided at each joint of a robot. A control loop gain adjustment program for a servo amplifier that forms a control loop by feeding back an amount, wherein a control loop gain based on a default value of the control loop gain and a default value of the power supply voltage of the servo amplifier And starting the drive of the servo motor, detecting the power supply voltage of the servo amplifier, and the control loop so as to change in the opposite direction to the detected change in the power supply voltage of the servo amplifier And a step of adjusting the gain.

  In order to achieve the above object, another robot control device according to the present invention feeds back a control amount of the servo motor in accordance with an external control command to a servo motor provided at each joint of the robot. In the robot control apparatus including a servo amplifier that forms a control loop, the servo amplifier is obtained by rectifying a commercial power supply, a drive unit that drives the servo motor, a control unit that controls the servo amplifier as a whole. A power supply unit that supplies a DC power supply voltage to the control unit, the control unit based on a default value of a control loop gain of the control loop and a default value of the power supply voltage of the power supply unit, Forming a control loop, means for starting the drive of the servo motor by the drive unit, means for detecting the power supply voltage of the power supply unit, Reduced if the power supply voltage out is increased, the power supply voltage is of and means for adjusting said control loop gain to increase in the case of falling.

  According to the present invention, the control loop can be stabilized with simple control against fluctuations in the power supply voltage of the servo amplifier during robot operation.

FIG. 1 is a diagram showing an overall configuration of a robot control system including a servo amplifier according to an embodiment of the present invention. FIG. 2 is a diagram showing a detailed configuration of the robot control apparatus shown in FIG. FIG. 3 is a schematic block diagram of the current servo control system shown in FIG. FIG. 4 is a flowchart for explaining the adjustment operation of the current loop gain of the robot controller shown in FIGS. FIG. 5 is a graph showing temporal transitions of the current loop gain KCP and the PN voltage PNvoltage when the flowchart shown in FIG. 4 is performed.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the following description, the same or corresponding elements are denoted by the same reference symbols throughout the drawings, and redundant description thereof is omitted unless otherwise specified.

[Robot control system configuration]
FIG. 1 is a diagram showing an overall configuration of a robot control system including a servo amplifier according to an embodiment of the present invention.

  The articulated robot 100 is configured as a so-called floor-standing 6-axis vertical robot in which the base 2 is installed on the floor surface below the work space. That is, the articulated robot 100 includes a wrist provided at the tip and six joints JT1 to JT6 provided in order from the predetermined base end toward the wrist, and the six joints JT1 to JT6 are first to first. It has 6 rotation axes A1 to A6, respectively, and is configured to rotate the next joint around each rotation axis A1 to A6. Note that the symbols (JT1 to JT6, A1 to A6) given to the six joints and the six rotation shafts are given for convenience, and any of the six joints and the six rotation shafts can be identified. It may be a code.

  When the base 2 is properly installed on the floor surface, the first to sixth rotation axes A1 to A6 are arranged such that the rotation axes of all adjacent joints are perpendicular to each other. A swivel base 3, arm members (links) 4, 5, 6, 7 and an attachment 9 are connected to the base 2 in this order. A tool member 11 (not shown) appropriately selected according to various work contents is detachably attached to the flange surface forming the tip of the attachment 9. The continuous members 2 to 7 and 9 from the base 2 to the attachment 9 are connected so as to be rotatable relative to each other. Hereinafter, the member groups 2 to 7 and 9 connected to each other through the six joints JT1 to JT6 are defined as robot arms.

  The arm members 6 and 7 and the attachment 9 form a structure 10 (hereinafter referred to as a wrist device) resembling a human wrist for causing the tool member 11 attached to the attachment 9 to perform a fine operation. . The first rotation axis A1, the second rotation axis A2, and the third rotation axis A3 are used as rotation axes for horizontally turning or swinging the tool member 11 together with the wrist device 10, and are the main axes of the articulated robot 100. Is made. The fourth rotation axis A4, the fifth rotation axis A5, and the sixth rotation axis A6 are rotation axes set in the wrist device 10.

  The first to sixth joints JT1 to JT6 are provided with servomotors M1 to M6 and position detectors E1 to E6, respectively. The position detectors E1 to E6 are composed of, for example, a rotary encoder. By driving the servo motors M1 to M6, the first to sixth joints JT1 to JT6 are allowed to rotate around the first to sixth rotation axes A1 to A6, respectively. Each servo motor M1 to M6 can be driven independently of each other. When the servo motors M1 to M6 are driven, the position detectors E1 to E6 set the rotational positions of the servo motors M1 to M6 around the first to sixth rotation axes A1 to A6. Detection is performed.

  The robot control device 200 is disposed around the base 2 of the articulated robot 100. The articulated robot 100 may be disposed remotely, or may be connected to the articulated robot 100 in a physically detachable form. The robot control device 200 includes a servo amplifier 210. The servo amplifier 210 passes the tool member 11 attached to the attachment 9 to an arbitrary position and posture with respect to each of the servo motors M1 to M6 included in the first to sixth joints JT1 to JT6 of the multi-joint robot 100. Servo control to move along

  The servo amplifier 210 includes a drive unit 230, a control unit 240, and a power supply unit 250. Note that the control unit 240 and the power supply unit 250 may be provided outside the servo amplifier 210. In other words, the servo amplifier 210 may be configured by only the drive unit 230.

  The drive unit 230 is a DC-AC converter that drives the servo motors M1 to M6 of the articulated robot 100, and is configured by an inverter including a full bridge circuit or a half bridge circuit, for example. A plurality of servo amplifiers 210 are provided so as to form individual servo loops for each of the servo motors M1 to M6. However, the servo motors M1 to M6 are driven in a unified manner by one servo amplifier 210. May be configured. In this case, only the drive unit 230 is provided for each of the servo motors M1 to M6.

  The control unit 240 controls the entire robot control apparatus 200 including the servo amplifier 210, and includes, for example, a microcontroller, CPU, MPU, PLC, DSP, ASIC, or FPGA. The control unit 240 may be configured by a plurality of controllers that perform distributed control in cooperation with each other. For example, the system may be configured such that the CPU is in charge of interface processing with the host controller and the DSP is in charge of basic calculations (position loop calculation, speed loop calculation, and current loop calculation) of the servo amplifier 210.

  The power source unit 250 is an AC-DC converter that supplies a power source voltage (a voltage PN voltage PN described later) obtained by rectifying the commercial power source 220 (primary power source) to a direct current to the driving unit 230. For example, a thyristor rectifier, It is composed of a switching power supply.

  The robot control device 200 is communicably connectable with a peripheral device (not shown) such as a teach pendant. The robot controller 200 receives a position command (control command) for translating or rotating the articulated robot 100 according to the position information stored by the operation of the operator of the peripheral device. Then, the robot control device 200 calculates a target position where the tool member 11 should be positioned after the control time has elapsed, based on the position command input every control time. Such a target position is calculated based on a movement distance obtained from a control time and a predetermined movement speed limit of the tool member 11, and the tool coordinate system (orthogonal coordinate system) so that the controller 240 can calculate the target position. Is converted into the format of coordinate data defined in. Then, the control unit 240 performs an inverse conversion process of the coordinate data of the target position, calculates joint angles θ1 to θ6 necessary for moving the tool member 11 to the target position after the control time has elapsed, The operations of the servo motors M1 to M6 provided in the first to sixth joints JT1 to JT6 based on the deviation between the joint angles θ1 to θ6 and the rotational position at power-on detected by the position detectors E1 to E6. The amount command value is calculated and supplied to each of the servo motors M1 to M6. As a result, the tool member 11 is moved to the target position every time the control time elapses.

[Robot controller configuration]
FIG. 2 is a diagram showing a detailed configuration of the robot control apparatus shown in FIG. Reference numerals M and E shown in the figure represent any one of the servo motors M1 to M6 and the position detectors E1 to E6 of the axes A1 to A6 shown in FIG. The drive unit 230 and the control unit 240 are provided on each of the axes A1 to A6. Also, the thick line shown in the figure represents the current loop of the current servo system.

  The power supply unit 250 includes a full-wave rectifier 251 that full-wave rectifies three-phase AC or single-phase AC supplied from the commercial power supply 220, a smoothing capacitor 252 that smoothes the output of the full-wave rectifier 251 to DC, and a servo motor M. Are provided with a regenerative resistor 253 and a regenerative power discharging transistor 254 that are used during regenerative operation. The DC voltage between both terminals of the smoothing capacitor 252 is used as a power supply voltage for a source transistor T1 and a sink transistor T2 of the driving unit 230 described later. Hereinafter, the voltage between both terminals of the smoothing capacitor 252 is referred to as an inter-PN voltage PNvoltage. In order to detect this inter-PN voltage PNvoltage, a voltage detector 255 is provided.

  In the drive unit 230, for example, a source transistor T1 and a sink transistor T2 are connected in series between the positive electrode P and the negative electrode N that define the PN voltage PNvoltage for each phase of the servo motor M. The coil current is supplied to the corresponding coil of the servo motor M from this connection point. Further, the drive unit 230 is provided with a current detector 231 that detects a coil current supplied from the drive unit 230 to the coil of the servo motor M for current servo control. Further, the driving unit 230 forms the regenerative diodes D1 and D2 in parallel with respect to the source transistor T1 and the sink transistor T2, respectively, in order to form a reactive current and a current path during regeneration when the servo motor M operates as a generator. Provided. In FIG. 2, only the configuration of the driving unit 230 for one phase of the servo motor M is illustrated for the sake of simplification.

  The control unit 240 includes a position control unit 241, a speed control unit 242, a current control unit 243, a pulse width modulation unit 244, a regeneration control unit 245, and a gain adjustment unit 246. The position control unit 241 outputs a speed command corresponding to the deviation between the position command from the robot controller 200 and the rotational position detected by the position detector E of the servo motor M. The speed control unit 242 outputs a current command (torque command) corresponding to the deviation between the speed command output from the position control unit 241 and the differential value (rotational speed) of the rotational position detected by the position detector E. The current control unit 243 outputs a voltage command corresponding to the deviation between the current command output from the speed control unit 242 and the coil current detected by the current detector 231. The pulse width modulation unit 244 compares the voltage command output from the current control unit 243 with a triangular wave signal, and generates and outputs a PWM signal for turning on and off the source transistor T1 and the sink transistor T2 of the driving unit 230.

  Based on the result of comparing the PN voltage PNvoltage detected by the voltage detector 255 with a predetermined threshold voltage (for example, a value equal to or higher than an upper limit value PNVOLT_MAX described later), the regenerative control unit 245 controls the regenerative power discharging transistor 254. A switching control signal for turning on / off is output. Specifically, the regenerative control unit 245 turns on the regenerative power discharging transistor 254 when the inter-PN voltage PNvoltage exceeds the threshold voltage, and turns off the regenerative power discharging transistor 254 when the inter-PN voltage PNvoltage falls below the threshold voltage. In this manner, the switching control signal is output.

  The gain adjusting unit 246 adjusts the current loop gain of the current control unit 243 based on the level of the PN voltage PNvoltage detected by the voltage detector 255.

  FIG. 3 is a schematic block diagram of the current servo control system shown in FIG. As shown in the figure, the current control unit 243 receives a deviation between the current command i output from the speed control unit 242 and the coil current detected by the current detector 231, and uses the deviation as a proportional gain. A proportional element 247 that outputs the output of the transfer function of KCP, and an integral element 248 that outputs the output of the transfer function of the integral gain KCI that receives the output of the proportional element 247, and the output of the proportional element 247 and the integral element The result obtained by adding the output of 248 is output as a voltage command v. The voltage command v output from the current control unit 243 is switched by the pulse width modulation unit 244 on the electronic circuit, and then applied to the servo motor M having the resistance component R and the inductance component L, and the coil current i as a response is given. Feedback is made to the input of the current control unit 243.

  Here, in the block configuration of the current control unit 243, since the integral element 248 acts as a simple time constant element, the action of the proportional element 247 is dominant. Therefore, the current loop gain of the current control unit 243 shown in FIG. 3 can be handled only by the proportional gain KCP of the proportional element 247. In the current control unit 243, the proportional gain KCP of the proportional element 247 is converted to the PN voltage PNvoltage. The gain is variable according to the level.

[Robot controller operation (current loop gain adjustment)]
FIG. 4 is a flowchart for explaining the adjustment operation of the current loop gain of the robot controller shown in FIGS.

  First, the AC power of the commercial power supply 220 is full-wave rectified by the full-wave rectifier 251, and the smoothing capacitor 252 is charged with a PN voltage PNvoltage of DC and a default value PNVOLT_DEF (for example, effective value 210V, rectified value 297V). The PN voltage PNvoltage is output as the power supply voltage of the bridge circuit of the drive unit 230. Further, the gain adjustment unit 246 initially sets the current loop gain (proportional gain) KCP of the current control unit 243 to the default value KCP_Default (step S400).

  Next, the robot control apparatus 200 starts position servo control, speed servo control, and current servo control for the servo motors M1 to M6 of the articulated robot 100. Then, when servo control with a large amount of power consumption is performed, such as when the workpiece is lifted by the acceleration of the robot arm or the tool member 11 at the tip of the robot arm, the electric power supplied from the commercial power supply 220 is the servo motor of each axis. The PN voltage PNvoltage supplied from the power supply unit 250 to the bridge circuit of the driving unit 230 may decrease in time for the power consumed by M1 to M6. Alternatively, when the servo control accompanied by the regenerative operation in which the servo motors M1 to M6 operate as a generator is performed, such as when the workpiece is lowered by the tool member 11 at the tip of the robot arm or the robot arm tip, the servo is performed by the regenerative resistor 253. The regenerative power generated by the motors M1 to M6 may not be consumed, and the PN voltage PNvoltage may increase.

  Therefore, the gain adjustment unit 246 changes the current loop gain KCP of the current control unit 243 to 1 / α times the default value KCP_Default when the PN voltage PNvoltage becomes α times the default value PNVOLT_DEF. Thereby, even if the voltage PNvoltage between PN fluctuates with the operation state of the robot arm, the current loop characteristic of the current servo control can be kept constant.

  Specifically, the gain adjustment unit 246 acquires the PN voltage PNvoltage detected by the voltage detector 255 and substitutes it into a predetermined variable (step S401), and the variable value of the PN voltage PNvoltage is the upper limit value PNVOLT_MAX. It is determined whether or not it is within a range from (for example, 350V) to a lower limit value PNVOLT_MIN (for example, 250V) (step S402). If the variable value of the inter-PN voltage PNvoltage is within the range from the upper limit value PNVOLT_MAX to the lower limit value PNVOLT_MIN (step S402: YES), the current loop gain KCP of the current control unit 243 is calculated by the following equation to obtain a predetermined buffer. (Step S403).

KCP = (PNVOLT_DEF [V] / PNvoltage [V]) * KCP_default (Expression 1)
(Expression 1) indicates that an inversely proportional relationship is established between the PN voltage PNvoltage and the current loop gain KCP.

  If the variable value of the PN voltage PNvoltage is not less than the upper limit value PNVOLT_MAX (step S402: NO), the variable value of the PN voltage PNvoltage is maintained at the upper limit value PNVOLT_MAX, and if the variable value is not more than the lower limit value PNVOLT_MIN (step S402: NO). The variable value of the PN voltage PNvoltage is maintained at the lower limit value PNVOLT (step S404). The reason for this is to suppress the instability of current servo control that accompanies a rapid change in the current loop gain KCP. Then, the process proceeds to step S403, and the current loop gain KCP is calculated based on (Equation 1). That is, the upper limit value KCP_MAX and the lower limit value KCP_MIN of the current loop gain KCP are each expressed by the following equations.

KCP_MAX = (PNVOLT_DEF [V] / PNVOLT_MIN [V]) * KCP_default (Expression 2)
KCP_MIN = (PNVOLT_DEF [V] / PNVOLT_MAX [V]) * KCP_default (Expression 3)
Next, the gain adjustment unit 246 performs low-pass filter processing on the variable value of the current loop gain KCP written in the buffer (step S405), and limits the value so as to fall within the range from the upper limit value KCP_MAX to the lower limit value KCP_MIN. Processing is executed (step S406). This is to further suppress the instability of current servo control that accompanies a rapid change in the current loop gain KCP.

  Next, the gain adjustment unit 246 changes the default value KCP_Default that is initially set in the current control unit 243 to the current loop gain KCP obtained in Step S406 (Step S407). As the subsequent processing, the gain adjustment unit 246 repeatedly executes steps S401 to S407.

  FIG. 5 is a graph showing the temporal transition of the PN voltage PNvoltage and the current loop gain KCP when the current loop gain KCP is adjusted according to the flowchart shown in FIG. Specifically, it is a graph showing the temporal transition of the current loop gain KCP when the PN voltage PNvoltage is equal to or higher than the upper limit value PNVOLT_MAX. The situation that appears in the figure will be described below.

  By decelerating the robot arm or lowering the workpiece by the tool member 11 at the tip of the robot arm, the PN voltage PNvoltage rises from the default value PNVOLT_DEF to the upper limit value PNVOLT_MAX. At this time, since the inter-PN voltage PNvoltage is within the range from the upper limit value PNVOLT_MAX to the lower limit value PNVOLT_MIN, the gain adjusting unit 246 determines the current in inverse proportion to the increase in the inter-PN voltage PNvoltage according to the above (Equation 1). The current loop gain KCP of the control unit 243 is lowered.

  If the inter-PN voltage PNvoltage is equal to or greater than the upper limit value PNVOLT_MAX, the gain adjustment unit 246 maintains the current loop gain KCP of the current control unit 243 at the lower limit value KCP_MIN. Note that the servomotor M operates as a power generator as the inter-PN voltage PNvoltage increases. Then, the regenerative control unit 245 switches the regenerative power discharging transistor 254 from OFF to ON when the inter-PN voltage PNvoltage becomes a threshold voltage equal to or higher than the upper limit value PNVOLT_MAX. As a result, the inter-PN voltage PNvoltage falls. Since the regenerative operation continues, when the inter-PN voltage PNvoltage falls to the upper limit value PNVOLT_MAX, the regenerative control unit 245 switches the regenerative power discharging transistor 254 from on to off, and the inter-PN voltage PNvoltage rises again. . In this manner, the PN voltage PNvoltageage repeatedly rises and falls by turning on and off the regenerative power discharging transistor 254.

  When the regenerative operation ends, the PN voltage PNvoltage gradually decreases from the upper limit value PNVOLT_MAX to the default value PNVOLT_DEF. At this time, since the inter-PN voltage PNvoltage is within the range from the upper limit value PNVOLT_MAX to the lower limit value PNVOLT_MIN, the gain adjusting unit 246 determines the current in inverse proportion to the decrease in the inter-PN voltage PNvoltage according to (Equation 1). The current loop gain KCP of the control unit 243 is increased from the lower limit value KCP_MIN. Note that the current loop gain KCP is maintained at the default value KCP_Default after the inter-PN voltage PNvoltage has reached the default value PNVOLT_DEF.

[Modification]
The current control loop gain that is varied according to the level of the PN voltage PNvoltage may be both the proportional gain KCP and the integral gain KCI of the current control unit 243. In addition, the current control unit 243 may be configured to perform PID control. In this case, the current control loop gain to be varied according to the level of the PN voltage PNvoltage is proportional gain, proportional gain + integral gain, proportional gain. It may be any one of + differential gain, or proportional gain + integral gain + differential gain.
The low-pass filter process executed for the current loop gain KCP may be executed for the PN voltage PNvoltage acquired from the voltage detector 255.
The low-pass filter process executed on the current loop gain KCP may be another filter process such as a band-pass filter process.

  The robot to be controlled by the robot control apparatus 200 is not limited to the above-described 6-axis articulated robot 100, and may be an arbitrary robot. For example, a multi-axis joint robot other than six axes or a robot other than a joint robot may be used.

  In addition to the above-described transistors, GTO, IGBT, SI thyristor, or the like can be used as a switching element constituting the bridge circuit of the driving unit 230.

  From the foregoing description, many modifications and other embodiments of the present invention are obvious to one skilled in the art. Accordingly, the foregoing description should be construed as illustrative only and is provided for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and / or function may be substantially changed without departing from the spirit of the invention.

  The present invention relates to a servo amplifier control loop gain adjustment method, a program, and a robot control apparatus, and is useful for stabilizing a control loop with simple control against fluctuations in power supply voltage of a servo amplifier during robot operation. .

DESCRIPTION OF SYMBOLS 100 ... Articulated robot M1-M6 ... Servo motors E1-E6 ... Position detector A1-A6 ... Rotating shaft JT1-JT6 ... Joint 2 ... Base 3 ... Turning base 4-7 ... Arm member 9 ... Attachment 10 ... Wrist device DESCRIPTION OF SYMBOLS 11 ... Tool member 200 ... Robot control apparatus 210 ... Servo amplifier 220 ... Commercial power supply 230 ... Drive part 231 ... Current detector T1 ... Source transistor T2 ... Sink transistor D1, D2 ... Regenerative diode 240 ... Control part 241 ... Position control part 242 ... speed controller 243 ... current controller 244 ... pulse width modulator 245 ... regenerative controller 246 ... gain adjuster 247 ... proportional element 248 ... integral element 250 ... power supply 251 ... full-wave rectifier 252 ... smoothing capacitor 253 ... regenerative resistor 254 ... Regenerative power discharging transistor 255 ... Voltage detector

Claims (7)

A control loop gain adjustment method for a servo amplifier that forms a control loop by feeding back a control amount of the servo motor according to a control command from the outside to a servo motor provided at each joint of the robot,
Based on the default value of the control loop gain and the default value of the power supply voltage of the servo amplifier, forming the control loop and starting driving the servo motor;
Detecting a power supply voltage of the servo amplifier;
Adjusting the control loop gain to change in the opposite direction to the detected change in power supply voltage of the servo amplifier;
A control loop gain adjustment method for a servo amplifier comprising: The control loop includes a current loop formed by feeding back the current of the servo motor,
The servo amplifier control loop gain adjustment method according to claim 1, wherein the step of adjusting the control loop gain adjusts a proportional gain included in a current loop gain that is a gain of the entire current loop.   2. The servo amplifier control loop gain adjusting method according to claim 1, further comprising a step of limiting the detected power supply voltage of the servo amplifier within a range from an upper limit value to a lower limit value.   The method of adjusting a control loop gain of a servo amplifier according to claim 1, further comprising a step of limiting the adjusted control loop gain within a range from an upper limit value to a lower limit value.   The servo amplifier control loop gain adjustment method according to claim 1, further comprising a step of filtering the detected power supply voltage of the servo amplifier or the adjusted control loop gain. A control loop gain adjustment program of a servo amplifier that forms a control loop by feeding back a control amount of the servo motor according to a control command from the outside to a servo motor provided at each joint of the robot,
On the computer,
Based on the default value of the control loop gain and the default value of the power supply voltage of the servo amplifier, forming the control loop and starting driving the servo motor;
Detecting a power supply voltage of the servo amplifier;
Adjusting the control loop gain to change in the opposite direction to the detected change in power supply voltage of the servo amplifier;
This is a servo amplifier control loop gain adjustment program. In a robot control apparatus provided with a servo amplifier that forms a control loop by feeding back a control amount of the servo motor according to a control command from the outside to a servo motor provided at each joint of the robot,
The servo amplifier is
A drive unit for driving the servo motor;
A control unit that controls the entire servo amplifier;
A power supply unit that supplies a DC power supply voltage obtained by rectifying a commercial power supply to the control unit,
The controller is
Based on the default value of the control loop gain of the control loop and the default value of the power supply voltage of the power supply unit, the control loop is formed, and the drive unit starts driving the servo motor;
Means for detecting the power supply voltage of the power supply unit;
Means for adjusting the control loop gain to decrease when the detected power supply voltage rises and to increase when the power supply voltage decreases;
A robot control device comprising:

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