JP7526599B2 - Motor amplifier and motor amplifier control method - Google Patents

Description

The present invention relates in particular to a motor amplifier that is connected to an encoder that detects the rotational position of a motor and controls the rotation of the motor, and a method for controlling the motor amplifier.

Conventionally, there exist a host device such as a PLC (Programmable Logic Controller) that transmits a position command, an encoder that acquires the rotational position of a motor, and a motor amplifier connected to this encoder.
For example, Patent Document 1 describes a control device equivalent to a motor amplifier that acquires position data output from an encoder and controls the rotation of a motor based on the position data (see, for example, paragraph [0022] of the patent document). This control device controls the rotation of the motor by controlling the current or voltage applied to the motor based on the position data. Furthermore, it is described that the control device can also acquire a higher-level control signal from a higher-level device and control the motor so that a rotational force capable of realizing the position, etc. represented by the higher-level control signal is output from the motor shaft.

Here, multiple types of encoders may be connected to the motor amplifier. These multiple types of encoders may have different communication speeds or different numbers of bits indicating the rotation angle.

JP 2014-013163 A

However, conventional motor amplifiers such as those described in Patent Document 1 had the problem that they could not obtain the correct rotational position if an encoder with a communication speed or bit count different from that originally connected was connected.

The present invention was made in consideration of these circumstances, and aims to provide a motor amplifier that can automatically obtain the correct rotational position even when encoders with different communication speeds or bit numbers are connected, thereby resolving the above-mentioned problems.

The motor amplifier of the present invention is a motor amplifier that is connected to an encoder that detects the rotational position of a motor and controls the rotation of the motor, and is equipped with a communication processing unit that, in an initial state, attempts communication with the encoder at a first speed setting, and if a communication error occurs, attempts communication with the encoder at a second speed setting, and when communication with the encoder is established by the communication processing unit, acquires model information of the encoder and sets the number of bits of the rotational position of the encoder corresponding to the model information , and is characterized in that the result of the negotiation attempting communication at the first speed setting or the second speed setting the first time is stored on a recording medium, and from the next time onwards, communication is attempted based on the result .
With this configuration, the correct rotational position can be obtained even if encoders with different communication speeds or bit numbers are connected.

The motor amplifier of the present invention is characterized in that the first speed setting is a setting for communicating with the encoder at the maximum speed possible, and the second speed setting is a setting for communicating at a speed slower than the maximum speed.
With this configuration, communication with the encoder can be established with priority given to communication at the maximum speed.

The motor amplifier of the present invention is characterized in that the bit number setting unit sets the bit number without obtaining the model information when communication with the encoder is established at the second speed setting.
By configuring in this way, it is possible to reduce the waiting time for connection.

The motor amplifier control method of the present invention is a motor amplifier control method executed by a motor amplifier connected to an encoder that detects the rotational position of a motor and controls the rotation of the motor, and is characterized in that in an initial state, communication with the encoder is attempted at a first speed setting, and if a communication error occurs, communication with the encoder is attempted at a second speed setting, and when communication with the encoder is established, model information of the encoder is obtained, the number of bits of the rotational position of the encoder corresponding to the model information is set, the result of the negotiation in which communication was attempted at the first speed setting or the second speed setting the first time is stored on a recording medium, and from the next time onwards, communication is attempted based on the result .
With this configuration, the correct rotational position can be obtained even if encoders with different communication speeds or bit numbers are connected.

According to the present invention, in the initial state, communication with the encoder is attempted at a first speed setting, and if a communication error occurs, communication with the encoder is attempted at a second speed setting. If communication is established, model information is obtained and the number of bits for the rotational position corresponding to the model information is set, thereby providing a motor amplifier that can automatically obtain the correct rotational position even when encoders with different communication speeds or number of bits are connected.

1 is a system configuration diagram of a control system according to an embodiment of the present invention. 4 is a flowchart of an auto-negotiation process according to the embodiment of the present invention. 3 is a timing chart of the auto-negotiation process shown in FIG. 2 .

<Embodiment>
[Configuration of Control System X]
The configuration of a control system X according to an embodiment of the present invention will be described with reference to FIG.
The control system X includes a motor amplifier 1 , a higher-level device 2 , an encoder 3 , and a motor 4 .

The motor amplifier 1 is a control device connected to a higher-level device 2 and an encoder 3. In this embodiment, the motor amplifier 1, for example, acquires a position command transmitted from the higher-level device 2, and further acquires angle information from the encoder 3, and drives and controls the motor 4 based on these. In this embodiment, an example will be described in which the position command and angle information are absolute values indicating the rotational position of the shaft S of the motor 4 according to the accuracy of the encoder 3, such as 17 bits, 20 bits, or 23 bits.
The detailed functional configuration of the motor amplifier 1 will be described later.

The motor amplifier 1 and the higher-level device 2 are connected, for example, by a field network such as EtherCAT, a serial communication line such as RS-232C, or a parallel communication line. On the other hand, the motor amplifier 1 and the encoder 3 are connected, for example, by a dedicated line and a serial communication line, and power is also supplied to servo-drive the motor 4. This power is supplied to the motor 4 via the encoder 3 or directly. In addition, the motor amplifier 1 may be capable of responding to a data request from the higher-level device 2. Alternatively, the motor amplifier 1 may be capable of acquiring status information such as temperature from the encoder 3.

The higher-level device 2 is a device for a client (customer) that transmits a position command. The higher-level device 2 is, for example, a PLC or a logic board of various devices equipped with a microcontroller.
The higher-level device 2 transmits a control signal for controlling the motor 4 to the motor amplifier 1 as a position command.
Furthermore, the higher-level device 2 can also obtain the detected position data of the motor 4 and other data from the motor amplifier 1 .

The encoder 3 is a device that acquires the rotational position of the motor. In this embodiment, the encoder 3 detects position data of the rotational position of the motor 4 and transmits it to the motor amplifier 1 as angle information. For this reason, the encoder 3 includes, for example, a magnetic or optical angle detection mechanism, a control and calculation means such as an MPU (Micro Processing Unit, microcontroller), a DSP (Digital Signal Processor), or an ASIC (Application Specific Integrated Circuit), and a non-transitory recording medium such as a RAM (Random Access Memory) that stores angle information and temporary data, and a ROM (Read Only Memory) that records a control program.

In this embodiment, the recording medium includes model information. This model information includes the ID (Identification) of the model of the encoder 3 and the motor 4, a serial number, information on the number of bits indicating the format of the angle information of the rotation angle (hereinafter simply referred to as "bit number"), information on the communication speed, and the like. In this embodiment, the number of bits is, for example, the amount of data (bits) of the angle information indicating the angular position corresponding to one rotation of the shaft S, and examples are shown in which the format is 17 bits, 20 bits, or 23 bits. Furthermore, the model information may include information such as the ID and serial number of the motor 4 acquired by the encoder.

The encoder 3 also includes a temperature sensor for measuring the temperatures of the motor 4 and the encoder 3 itself, etc. The encoder 3 may also include a built-in backup battery (not shown) for data, and may be capable of continuing to store position data in a built-in storage medium when the shaft is driven by an external force or the like.
Further, the encoder 3 may be capable of transmitting signals from the temperature sensor, the battery voltage sensor, etc. as a type of data separate from the angle information.

The motor 4 rotates a shaft S, which is a rotary output shaft, about a rotation axis A as a central axis in response to a control signal from the motor amplifier 1 .
The motor 4 is a typical servo motor or the like that includes a rotor, a bearing, a stator, a bracket, and the like.

[Configuration of motor amplifier 1]
To explain in more detail, in this embodiment, the motor amplifier 1 includes a communication control unit 10 and an amplifier control unit 20 .

The communication control unit 10 receives communication, acquires position commands and the like addressed to the motor amplifier 1 from the higher-level device 2 , and transmits them to the amplifier control unit 20 .
The communication control unit 10 includes, for example, a control and calculation means such as an MPU, a DSP, or an ASIC, a non-transitory recording medium such as a RAM or a ROM, and a communication circuit (physical layer).

The amplifier control unit 20 calculates angle information based on the position command obtained from the communication control unit 10, and servo-drives the motor 4 to control the position of the shaft S. At this time, the amplifier control unit 20 can also control the motor 4 by referring to the angle information obtained by the encoder 3. Furthermore, the amplifier control unit 20 can also obtain information from various other sensors and transmit it to the communication control unit 10 together with the angle information.
The amplifier control section 20 includes a control and calculation means such as an MPU, a DSP, or an ASIC, and a non-transitory recording medium such as a RAM or a ROM.

Next, the functional configuration of the motor amplifier 1 will be described.
The amplifier control unit 20 includes a communication processing unit 100 and a bit setting unit 110 .

In the initial state, the communication processing unit 100 attempts to communicate with the encoder 3 at a first speed setting, and if a communication error occurs, attempts to communicate with the encoder 3 at a second speed setting. Here, the first speed setting is a setting for communicating at the maximum speed at which communication with the encoder 3 can be performed. In this embodiment, an example in which the first speed setting is 4 Mbps (bits per second) will be described. On the other hand, the second speed setting is a setting for communicating at a speed slower than the maximum speed. In this embodiment, an example in which the second speed setting is 2.5 Mbps will be described.

When communication with the encoder 3 is established by the communication processing unit 100, the bit number setting unit acquires model information of the encoder 3 and sets the format of the bit number indicating the rotational position of the encoder 3 corresponding to the model information. In this embodiment, for 23-bit and 20-bit encoders 3, the bit number is set corresponding to this model information. In addition, when communication with the encoder 3 is established at the second speed setting, the bit number setting unit can also set the bit number without acquiring the model information. In this embodiment, an example will be described in which only the 17-bit encoder 3 has a communication speed of 2.5 Mbps.

Here, the amplifier control unit 20 functions as the communication processing unit 100 and the bit setting unit 110 by executing a control program stored in the recording medium of the amplifier control unit 20. Note that it is also possible to configure some or all of these components as circuits using logic circuits or FPGAs (Field Programmable Gate Arrays), etc.

[Auto negotiation processing]
Next, the auto-negotiation process according to the embodiment of the present invention will be described with reference to FIG. 2 and FIG.
In the auto-negotiation process of this embodiment, in the initial state, communication with the encoder 3 is attempted at a first speed setting. If a communication error occurs, communication with the encoder 3 is attempted at a second speed setting. Then, when communication with the encoder 3 is established, model information is obtained from the encoder 3, and the number of bits of the rotational position of the encoder 3 corresponding to the model information is set.

In the auto-negotiation process of this embodiment, the amplifier control unit 20 mainly executes a control program (not shown) stored in a storage medium in cooperation with each unit, using hardware resources.
The auto-negotiation process of this embodiment will be described in detail below for each step using the flowchart of FIG. 2 and with reference to the timing chart of FIG. 3 as appropriate.

(Step S101)
First, the communication processing unit 100 performs a first speed setting process.
As an initial state, the communication processing unit 100 sets the baud rate to a first speed setting that communicates with the encoder 3 at the maximum possible speed. In this embodiment, an initial setting is used that sets the baud rate to 4 MBps. The communication processing unit 100 also performs other initialization processes and waits for a time period, for example, several milliseconds to several seconds, until the encoder 3 starts up.

(Step S102)
Next, the communication processing unit 100 performs an initial communication process.
The communication processing unit 100 attempts to communicate with the encoder 3 at the first speed setting as the initial communication. In this embodiment, the communication processing unit 100 performs the initial communication at 4 Mbps (timing T101).

(Step S103)
Next, the communication processing unit 100 judges whether or not communication has been established (timing T102). If the communication processing unit 100 receives the expected reply from the encoder 3 and is able to establish communication, the result is Yes. If the communication processing unit 100 is unable to receive the expected reply from the encoder 3 in communication, i.e., if there is a communication abnormality (communication error), the result is No.
If the answer is Yes, the communications processing unit 100 advances the process to step S108.
If the answer is No, the communications processing unit 100 advances the process to step S104.

(Step S104)
In the case of a communication error, the communication processing unit 100 performs a second speed setting re-communication process.
The communication processing unit 100 attempts to communicate with the encoder 3 at the second speed setting. In this embodiment, the communication processing unit 100 sets the baud rate to 2.5 MBps and attempts communication again (timing T103).

(Step S105)
Next, the bit setting unit 110 judges whether or not communication has been established (timing T104). If communication has been established, the bit setting unit 110 judges as Yes. If a communication error occurs even at the second speed, the bit setting unit 110 judges as No. In this embodiment, if a communication error occurs even at 2.5 Mbps, the bit setting unit 110 judges as No.
If the answer is Yes, the bit setting section 110 advances the process to step S106.
If the answer is No, the bit setting unit 110 advances the process to step S107.

(Step S106)
When communication is established at the second speed setting, the bit setting unit 110 performs a second speed bit number setting process.
The bit number setting unit sets the bit number without acquiring model information. In this embodiment, the bit number setting unit determines that the bit number of the encoder 3 is a 17-bit format.
Thereafter, the bit setting unit 110 ends the auto-negotiation process of this embodiment, and immediately starts communication such as obtaining angular information of the rotational position from the encoder 3 .

(Step S107)
If a communication error occurs even at the second speed setting, the bit setting unit 110 performs error processing.
The bit setting unit 110 indicates that communication with the encoder 3 cannot be established due to a communication abnormality by changing the color or blinking of an LED (Light Emitting Diode) or the like that indicates the state of the motor amplifier 1. Furthermore, the bit setting unit 110 notifies the higher-level device 2 of the error that communication with the encoder 3 cannot be established.
Thereafter, the bit setting unit 110 ends the auto-negotiation process of this embodiment.

(Step S108)
When communication is established at the first speed setting, the bit setting unit 110 performs a model information acquisition process.
The bit setting unit 110 transmits a command (instruction) to the encoder 3 to instruct it to transmit the model information. Upon receiving this command, the encoder 3 transmits the model information stored in the recording medium to the motor amplifier 1 (timing T105).
The bit setting unit 110 acquires the model information of the encoder 3 and temporarily stores it in a recording medium. As described above, the model information may include model information of the motor 4.

(Step S109)
Next, the bit setting unit 110 performs a process of setting the number of model information bits.
The bit setting unit 110 analyzes the model information and sets the format of the number of bits related to the angle information of the rotational position. In this embodiment, specifically, it sets that the encoder 3 is a 20-bit or 23-bit encoder. For example, the bit setting unit 110 refers to a table that indicates the model ID and the number of bits stored in the recording medium, and determines whether the encoder 3 is a 20-bit encoder or a 23-bit encoder.
This completes the auto-negotiation process according to the embodiment of the present invention.

After the number of bits is set in this manner, the motor amplifier 1 transmits the set number of bits to the higher-level device 2 .
Then, the motor amplifier 1 acquires angular information of the rotational position from the encoder 3 with the corresponding number of bits, and transmits it to the higher-level device 2. Furthermore, the motor amplifier 1 receives a position command from the higher-level device 2, and controls the rotational position of the shaft S of the motor 4 in response to this command.

[Major Effects of the Present Embodiment]
With the above configuration, the following effects can be obtained.
In recent years, there has been a need among users to use different encoders depending on the purpose.
However, the conventional motor amplifier described in Patent Document 1 was not designed to connect to other encoders with different communication speeds or bit numbers. Therefore, when such other encoders were connected, the correct rotation position could not be obtained unless the user directly set it. In other words, conventionally, a motor amplifier connected to a 17-bit (communication baud rate: 2.5 Mbps) encoder could not communicate or obtain the rotation position even if a 23-bit (baud rate: 4 Mbps) encoder was connected.

In contrast, the motor amplifier 1 according to an embodiment of the present invention is a motor amplifier that is connected to an encoder 3 that detects the rotational position of a motor 4 and controls the rotation of the motor 4, and is characterized by having a communication processing unit 100 that, in the initial state, attempts to communicate with the encoder 3 at a first speed setting, and if a communication error occurs, attempts to communicate with the encoder 3 at a second speed setting, and a bit number setting unit that, when communication with the encoder 3 is established by the communication processing unit 100, obtains model information of the encoder 3 and sets the number of bits of the rotational position of the encoder 3 that corresponds to the model information.

By configuring it in this way, even if an encoder 3 with a different communication speed or bit number is connected, the correct rotation position can be obtained without any special settings. In other words, auto-negotiation can be performed with the encoder 3 to obtain angle information of the rotation position. This makes it possible to support automatic connection of a 23-bit (baud rate: 4 Mbps) encoder 3. In addition, it is also possible to automatically connect 17-bit and 23-bit formats without changing parameters or settings.

The motor amplifier 1 according to the embodiment of the present invention is characterized in that the first speed setting is a setting for communicating with the encoder 3 at the maximum possible speed, and the second speed setting is a setting for communicating at a speed slower than the maximum speed.

With this configuration, communication with the encoder 3 can be established with priority given to communication at the maximum speed. That is, for example, if 4 Mbps is set as the default (prescribed) communication speed baud rate and an encoder 3 that can be connected at 4 Mbps is connected, communication becomes possible immediately. In this case, it is not necessary to attempt communication by negotiating from a slow speed such as 2.5 Mbps.
In other words, when an encoder 3 capable of high-speed communication is connected, connection is possible without taking time for initial communication. Therefore, even if an encoder capable of high-speed communication is put into a power saving state such as sleep, it will immediately return to a state where communication is possible at maximum speed. On the other hand, it is also possible to use an inexpensive or old-style encoder 3 that does not require the same communication speed as an encoder 3 capable of high-speed communication.

The motor amplifier 1 according to the embodiment of the present invention is characterized in that the bit number setting unit sets the bit number without acquiring model information when communication with the encoder 3 is established at the second speed setting.

By configuring in this way, for an encoder 3 that communicates at the second speed setting, even if a communication error occurs when communicating at the maximum speed, it is possible to connect with reduced waiting time. That is, for example, by attempting communication at 4 Mbps and assuming that there is no response, a 17-bit connection is made, so that even in the case of an inexpensive or old encoder 3, connection can be made with little waiting.

Other Embodiments
In the above embodiment, an example has been described in which the first speed setting is 4 Mbps and the second speed setting is 2.5 Mbps. Furthermore, examples have been described in which the 17-bit, 20-bit, and 23-bit encoders 3 are used.
However, it is of course possible to use other communication speed settings, bit number settings, etc. Even in this case, if a communication error occurs during communication attempt, the communication speed setting may be changed and the model information may be acquired after that. Furthermore, if a communication error occurs even at the second speed setting, communication may be performed at a third speed setting that is a setting for communicating at a speed slower than the second speed setting. Alternatively, the first speed setting may be configured to be slower than the second speed setting.
Such a configuration makes it possible to support the encoder 3 with various communication speeds and bit numbers.

In the above embodiment, the auto-negotiation process is executed every time the motor amplifier 1 is started up.
However, after performing auto-negotiation once at the initial time, the result may be stored in the recording medium of the amplifier control unit 20, and this may be performed every time as the "priority mode." Even in this case, if connection is possible at the first speed setting, the bit setting unit 110 may obtain model information just to be sure, and confirm that the bit number format, etc. are the same as those stored in the recording medium.
By configuring in this manner, it becomes possible to establish communication more quickly and obtain angular information of the rotational position after the first communication.

In the above embodiment, an example has been described in which the encoder 3 supports a single combination of speed setting and number of bits.
However, it is also possible to use an encoder 3 capable of communicating at multiple speeds or capable of communicating angle information in a format with different bit numbers.
In this case, for example, if communication errors occur frequently at the first speed setting, the amplifier control unit 20 may communicate at the second speed setting. Alternatively, the amplifier control unit 20 may convert the torque using a current feedback value of the control of the motor 4, and if there is a lot of vibration, etc., may reduce the number of bits to lower the accuracy. In these cases, the amplifier control unit 20 may transmit a command to the higher-level device 2 and the encoder 3 to instruct them to perform such processing.
Such a configuration makes it possible to accommodate a flexible configuration.

It goes without saying that the configurations and operations of the above-described embodiments are merely examples and can be modified as appropriate without departing from the spirit and scope of the present invention.

REFERENCE SIGNS LIST 1 Motor amplifier 2 Upper device 3 Encoder 4 Motor 10 Communication control unit 20 Amplifier control unit 100 Communication processing unit 110 Bit setting unit A Rotating shaft S Shaft X Control system

Claims (4)

A motor amplifier connected to an encoder that detects a rotational position of a motor and controls the rotation of the motor,
a communication processing unit that, in an initial state, attempts to communicate with the encoder at a first speed setting, and when a communication error occurs, attempts to communicate with the encoder at a second speed setting;
a bit number setting unit that acquires model information of the encoder when communication with the encoder is established by the communication processing unit, and sets a bit number of the rotation position of the encoder corresponding to the model information ;
The result of the negotiation in which communication is attempted at the first speed setting or the second speed setting at the first time is stored in a recording medium, and from the next time onwards, communication is attempted based on the result.
A motor amplifier comprising: the first speed setting is a setting for communicating with the encoder at a maximum speed at which communication is possible;
The motor amplifier according to claim 1 , wherein the second speed setting is a setting for communicating at a speed slower than the maximum speed. The bit count setting section is
3. The motor amplifier according to claim 1, wherein, when communication with the encoder is established at the second speed setting, the number of bits is set without acquiring the model information. A motor amplifier control method executed by a motor amplifier that is connected to an encoder that detects a rotational position of a motor and controls the rotation of the motor, comprising:
Attempting communication with the encoder at a first speed setting in an initial state;
If a communication error occurs, attempt to communicate with the encoder at a second speed setting;
When communication with the encoder is established, model information of the encoder is acquired, and a number of bits of a rotational position of the encoder corresponding to the model information is set ;
The result of the negotiation in which communication is attempted at the first speed setting or the second speed setting at the first time is stored in a recording medium, and from the next time onwards, communication is attempted based on the result.
A motor amplifier control method comprising:

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