JP2893867B2 - Digital servo drive system - Google Patents

Description

The present invention relates to a digital servo drive system, and more particularly, to a digital servo drive system used for a robot.

[Conventional technology]

In a conventional servo drive system, an electro-mechanical separation system in which the entire servo drive is mounted inside a controller and a power line for each axis is supplied to a machine or a robot (hereinafter, collectively referred to as a robot). Therefore, besides the signal line, the cable connecting the controller and the robot, U, V, W phase and ground
I needed a power cable. Therefore, in the case of a 6-axis robot, 24 power cables were required, and the connection between the controller and the robot was very thick.

FIG. 3 is an example of a servo drive system of the electro-mechanical separation type.

Six servo drives 42 _1, 42 _2, 42 _3, 42 _4, 42 _5, 42 ₆ is mounted inside the controller 41, between the controller 41 and the robot 40 are connected by a thick power cables 43.

Here, if the control section (arithmetic section) and the power section are to be separated in order to shorten the power cable, it is necessary to attach a CPU to the power section and read the contents of the EEPROM as described below.

FIG. 4 is a configuration diagram of an example of a servo drive in which a control section and a power section are separated (hereinafter, referred to as a separated type).

The control section 1A and the power section 2A are configured separately, and both are detachably connected. The power unit 2A receives the calculation result of the control unit 1A as a U, V, W phase PWM command via the line driver 44 and the line receiver 45. The ON delay circuit 46 generates a base drive signal corresponding to each phase PWM command. Inverter 47 drives servo motor 48 in response to each phase base drive signal. The output current value of the inverter 47 is detected by a current detector 49, and PW
After being M-modulated, it is fed back to the control unit 1A as a current feedback signal.

The EEPROM 51 is a constant that is necessary for the control unit 1A to calculate the PWM command and that needs to be changed according to the current capacity of the servo motor, such as the current capacity of the servo motor, the gain of the current detector, and offset data. Has been written.

When starting the servo drive system,
1A, when transmitting a data request signal to the CPU 52 via the T _X D pins, CPU 52 transmits the data of the EEPROM51 reading, the R _X D pin of the control unit 1A. The control unit 1A generates the PWM command using the read content as an internal constant.

As described above, since a part that needs to be changed according to the current capacity of the servomotor 48 is mounted on the power unit, when the current capacity of the servomotor is changed,
Only the power section can be replaced and the control section can be used in common. In this way, by digitizing the servo system and reading the constants required for the calculation of the PWM command from the memory at the initial stage of the operation and calculating the same, the control unit itself can be configured irrespective of the current capacity of the servomotor.

[Problems to be solved by the invention]

In the above electromechanical separation type servo drive system, not only the cable connecting the controller and the robot body becomes thicker, but also the servo drive is housed in the controller, so a large heat sink is required for heat dissipation. However, there is a problem that the controller itself cannot be downsized.

In addition, in a separate servo drive system, if the EEPROM is mounted in the power section according to the technical idea of mounting all the parts to be changed according to the current capacity of the servomotor in the power section, the CPU must be provided in the power section. In addition, there is a problem that a signal line only for transmitting data read from the memory is required.

SUMMARY OF THE INVENTION An object of the present invention is to provide a separated type servo drive system in which a control unit is small, a power cable is thin, and it is not necessary to install a CPU in the power unit.

[Means for solving the problem]

A first digital servo drive system according to the present invention includes a control unit that calculates U, V, and W phase current commands for controlling a servo motor, and drives the servo motor in response to the current command. It consists of a power section that feeds back the generated current feedback signal to the control section, and the control section and the power section are separately provided, and between them, the U, V, W phase current command transmission line and the current feedback signal The transmission section is connected to the power section, and the power section contains constants that are necessary for the servo amplifier, current detection means, and control section to calculate the current command, and that need to be changed according to the current capacity of the servo motor. A digital servo drive system in which a written memory is arranged, wherein the control unit is configured to read a U / V phase current command and read data. When the switching signal is at the first logic level, the U, V phase current command is selected. When the switching signal is at the second logic level, the data read command is selected, and the data read command is selected on the U, V phase current transmission line. A first selector that transmits the signal; and a W-phase current command connected to the transmission line for W-phase current command when the switching signal is at the first logic level; and disconnects the transmission line when the switching signal is at the second logic level. The power unit further includes: a disconnection detection unit that detects disconnection when the W-phase current command transmission line is disconnected, deactivates the servo amplifier, and enables the memory to be read and enabled when the transmission line for the W-phase current command is disconnected. Means for inputting the current feedback signal and the output of the memory, selecting the current feedback signal when the disconnection is not detected, and selecting the memory when the disconnection is detected. And a second selector for selecting the output of the second signal and transmitting the selected signal to the current feedback signal transmission line.

According to a second digital servo drive system of the present invention, the servo motor of the first digital servo drive system of the present invention is an actuator for operating the robot main body, and the power unit is installed on the robot main body.

[Action]

When the switching signal is at the first logic level, the first selector transmits the U and V phase current commands on the U and V phase current command transmission lines (hereinafter referred to as U and V phase transmission lines), The W-phase connection means connects the W-phase current command to a W-phase current command transmission line (hereinafter, referred to as a W-phase transmission line). Servo pump is U, V, W
The servo motor is driven in response to U, V, W phase current commands transmitted via the phase transmission line. The current feedback signal is fed back to the control unit via a current feedback signal transmission line (hereinafter, referred to as a current feedback transmission line). Hereinafter, the above operation mode is referred to as a drive mode.

When the switching signal is at the second logic level, the first selector transmits a data read command on the U and V phase transmission lines and
The phase transmission line is disconnected. As a result, the disconnection detecting means detects the disconnection, whereby the servo amplifier is deactivated, the memory is enabled for reading, and the data is read. The second selector outputs the data on the current feedback transmission line. The constant written in the memory as described above is directly read out by the control unit without using the CPU, and is used as a parameter in the calculation of the U, V, and W phase current commands. Further, it is not necessary to use a new signal line for this data reading. Hereinafter, this operation mode is referred to as a disconnection mode.

In the servo drive system of the present invention, since the servo amplifier is mounted on the power unit, the power unit is installed on the robot body and the servo amplifier is mounted on the robot body, so that the control unit is downsized and the power cable is connected to the servo amplifier. Only one power cable. Further, since the robot body can be used as a heat sink for the power transistor, it is not necessary to use a dedicated heat sink.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a digital servo drive system according to a first embodiment of the present invention.

The digital servo drive system of the present embodiment includes a control unit 1 and a power unit 2, both of which are U and V
The phase transmission line 20, the W-phase transmission line 21, and the current feedback transmission line 22 are connected.

The control unit 1 includes a selector 3, a U-phase line driver 4, a W-phase line driver 5, an inverter 17, a line receiver 6 for the U-phase and V-phase current feedback transmission lines, and a disconnection for the U-phase and V-phase current feedback transmission lines. The detection circuit 7 is mounted.

Selector 3, corresponds to the first selector according to claim (1) consists of a U-phase selector 3 _1, V-phase selector 3 _2. In each selector 3 _1, 3 ₂ a known two-input one-output selector, U-phase selector 3 _1, V-phase selector 3 ₂ each calculation unit (not shown) is U-phase PWM command computed, the V-phase PWM command A serial clock signal S to be applied as a first input to an EEPROM described later
K, the data read command Di is a second input. U-phase selector 3 _1, V-phase selector 3 _2, switching signal S is U-phase PWM command respectively when the low level, and outputs a V-phase PWM command, respectively serial clock signal SK, and the data read when the switching signal S is at a high level The command Di is output and connected to the U and V phase transmission lines 20 via the line driver 4. The line driver 5 corresponds to the W-phase connection means of claim (1). When the switching signal S is at a low level, the line driver 5 transmits a W-phase PWM command to the W-phase transmission line 21;
Make 21 floating. Line receiver 6 is U, V
The balanced signal transmitted via the phase current feedback transmission line 22 is differentially amplified and transmitted to the operation unit. Disconnection detection circuit 7 for U, V phase current feedback transmission line
In the photocoupler type disconnection detection circuit disclosed in -15599, its input terminal is connected in series to each transmission line,
When the transmission line is disconnected, its output is turned off and the disconnection detection signal D is inverted.

The power section 2 includes an on-delay circuit (not shown), a three-phase inverter (not shown), a disconnection detection circuit 8, an EEPROM 9, inverters 10 and 16, a selector 11, a current detector (not shown), and a line receiver 12. , 13, and line drivers 14 and 15 are mounted.

The line receiver 12 receives the balanced signals on the U and V phase transmission lines 20 and differentially amplifies them, and outputs the U and V phase PWM commands in the drive mode, and outputs the serial clock signal SK and the data read command Di in the disconnection mode. . The line receiver 13 outputs the W-phase PWM command in the drive mode, and does not output the input in the disconnection mode because the input becomes high impedance. The on-delay circuit inputs a base block signal 23 generated by a disconnection detection circuit 8 described later as an enable signal, and generates a base drive signal in response to the U, V, W phase PWM command in the drive mode, and The three-phase inverter is driven, and the base is blocked in the disconnection mode (see FIG. 3). The three-phase inverter drives the servo motor in response to the base drive signal.

Disconnection detecting circuit 8, U-phase, V-phase, U-phase which detect the disconnection of the W-phase transmission line, made in V-phase, W-phase photocoupler 8 _1, 8 _2, 8 _3, the output of the output (light receiving element ) Are connected in series. In this embodiment, the anode of the light receiving element of the U-phase photocoupler is connected to the positive power supply via the resistor R1,
8 ₃ of the anode and cathode of the light receiving element are connected, through said resistor R2 positive power supply, and a ground terminal. U
The anode A ₁ of the phase photocoupler ₈₁ of the light receiving element, the voltage is used to base block the three-phase inverter, as described below with respect to the ground, below, baseblock
Write 23. When any one of the U, V, and W phase transmission lines is disconnected, the base block signal 23 is inverted from a low level to a high level. Further, when the operation of the servo drive system is switched to the disconnection mode from the driving mode, W-phase transmission line of the anode A ₃ of the light-receiving element of the W-phase photocoupler 8 ₃ since the floating, the voltage to ground is a high level from a low level Flip to Hereinafter, this voltage is referred to as disconnection detection signal.
Write 24. The EEPROM 9 is of a serial type and corresponds to the memory disclosed in claim (1). The current capacity of the servomotor, the gain of the current detector, the offset data, and other controls are used for the first arithmetic unit to calculate the current command. Necessary
In addition, a constant to be changed according to the current capacity of the servomotor is written. The EEPROM 9 uses the disconnection detection signal 24 as a chip select signal. In the drive mode, the readout is disabled. In the disconnection mode, the data is written to the address specified by the data readout command Di in synchronization with the serial clock signal SK transferred from the line receiver 12. Outputs the data that is included. The selector 11 corresponds to the second selector in claim (1). The selector 11 receives the output of the U-phase current feedback signal I _U and EEPROM9 output from the U-phase current detector, when the disconnection detection signal 24 is at the low level, selects the U-phase current feedback signal I _U, a high level Sometimes, the output of EEPROM 9 is selected and output. Line driver 1
4 outputs the output of the selector 11 onto the U-phase current feedback transmission line 22. The line driver 15 outputs a balanced signal of the V-phase current feedback signal on the V-phase current feedback transmission line when the base block signal 23 is at a low level, and disables the output when the base block signal 23 is at a high level.

 Next, the operation of this embodiment will be described.

First, at the time of operation in the drive mode, the switching signal S is set to the low level.

At this time, the selector 3 selects the U and V phase PWM commands, and the output of the line driver 5 is enabled. As a result, U,
The V and W phase PWM commands are transmitted to the on-delay circuit via the respective line drivers 4 and 5, the transmission lines 20 and 21, and the line receivers 12 and 13. At this time, since the U, V, and W phase transmission lines 20 and 21 are all connected, the disconnection detection circuit 8 outputs the low-level base block signal 23, and as a result, the on-delay circuit operates and the three-phase The inverter operates and the servo motor is driven. At this time, the output of the line driver 15 is enabled by the inverted signal of the base block signal, and the V-phase current feedback signal is transmitted to the control unit via the line driver 15. Also,
In this operation mode, the disconnection detection signal 24 becomes low level, so that the selector 11 selects and outputs the U-phase current feedback signal, and the signal is transmitted to the control unit via the line driver 14.

The normal operation of the servo drive system is performed in this manner.

Next, when the servo drive system is operated in the disconnection mode, the switching signal S is set to a high level.

Thereby, the selector 3 outputs the serial clock signal SK
And the data read command Di are selected and output. As a result, these signals are transmitted on the output line of the line receiver 12 via the line driver 4, U, and V-phase transmission lines 20.
On the other hand, since the line driver 5 makes the W-phase transmission line 21 floating, the disconnection detection circuit 8 outputs the base block signal.
23 is made high, so that the on-delay circuit is deactivated and the three-phase inverter is base-blocked.
At this time, since the disconnection detection signal 24 is also set to the high level at the same time, the EEPROM 9 is enabled for reading, and the data at the address specified by the data read command Di is read in synchronization with the serial clock signal SK. Further, at this time, the selector 11 selects and outputs the output of the EEPROM 9, so that the data read from the EEPROM 9 is transmitted to the control unit 1 via the line driver 14. Further, the output of the line driver 15 is disabled by the inverted signal of the base block signal, so that the V-phase current feedback signal is not transmitted.

Thus, in the disconnection mode, the U, V phase transmission line 2
0 sets the serial clock signal SK and data read command Di.
And the data read from the EEPROM 9 can be transmitted using the U-phase current feedback transmission line 22.

Next, a description will be given of a second embodiment of the servo drive system according to the present invention.

FIG. 2 is a diagram showing an example of an arrangement of a three-phase inverter unit of the digital servo drive system of the present invention.

In the servo drive system of the present embodiment, the servomotor is a robot actuator, and the power unit shown in FIG. 1 is installed in the robot body. Therefore, a power cable for connecting the three-phase inverter and the robot body is not required. Therefore, the power cable is only the power cable 33 for the inverter. Further, since each power transistor of the inverter unit is attached to the robot main body, the robot main body serves as a heat sink. As a result, the heat sink of the power transistor is omitted.

The functions and operations of the servo drive system of the present embodiment are exactly the same as those of the first embodiment.

〔The invention's effect〕

As described above, according to the present invention, the disconnection state of the U, V, and W phase transmission lines is regarded as one status, and the memory is read and read by the disconnection detection signal and the base block signal, which are the status signals indicating the status. Controlling the output of data onto the current feedback transmission line has the following effects.

(1) The memory can be read directly from the control unit without providing a CPU in the power unit and without providing a new signal line.

(2) When the power transistor of the servo amplifier is mounted on the robot main body, only the power cable of the power transistor is required as the power cable, so that the power cable can be made thinner and the robot can be made smaller. Can be a heat sink. And, no matter how the power unit is arranged, the memory can be read directly from the control unit without providing a CPU in the power unit.

[Brief description of the drawings]

FIG. 1 is a block diagram of a digital servo drive system according to a first embodiment of the present invention, FIG. 2 is a diagram showing an example of an arrangement of a three-phase inverter unit of the digital servo drive system of the present invention, and FIG. FIG. 4 is a diagram showing an example of a separation type servo drive system, and FIG. 4 is a configuration diagram of an example of a separation type servo drive system. 1 ... Control section, 2 ... Power section, 3,11 ... Selector, 4,5,14,15 ... Line driver, 6,12,13 ... Line receiver, 7,8 ... Disconnection detection circuit, 8 ₁ , 8 ₂ , 8 ₃ … Photo coupler, 9… EEPROM, 10, 16, 17… Inverter, 23… Base block signal, 24… Disconnection detection signal, 30… Power supply, 31, 32… ... Inverter unit, 33 ... Power cable.

Claims (2)

(57) [Claims] 1. A control section for calculating U, V, W phase current commands for controlling a servomotor, and a current fever dock signal generated by current detection means for driving the servomotor in response to the current command and generating current commands. The control section and the power section are provided separately, and a transmission line for U, V, W phase current command and a transmission line for current feedback signal are connected between the two. In the power section, a memory in which a servo amplifier, current detecting means, and a control section are required to calculate a current command and are written with constants that need to be changed in accordance with the current capacity of the servomotor. In the digital servo drive system, the control unit receives a U, V phase current command and a data read command as inputs, and the switching signal is a first logic signal. A first selector for selecting the U and V phase current commands when the signal is at the bell level, selecting a data read command for transmitting the data read command to the U and V phase current command transmission lines when the signal is at the second logic level; When the logic level is 1, a W-phase current command is connected to the W-phase current command transmission line, and when the switching signal is at the second logic level, the W-phase connection means disconnects the transmission line. When the W-phase current command transmission line is disconnected, disconnection detection means for detecting disconnection, deactivating the servo amplifier, and enabling reading of the memory, and the current feedback signal and the output of the memory. When the disconnection is not detected, the current feedback signal is selected. When the disconnection is detected, the output of the memory is selected to transmit the current feedback signal. Digital servo drive system, characterized in that it comprises a second selector for transmitting on the line. 2. The digital servo drive system according to claim 1, wherein said servo motor is an actuator for operating a robot main body, and said power section is installed in said robot main body.