Servo system and gain adjustment method for servo motor control

Abstract

The present invention is provided with: a servo motor; a servo driver which supplies a driving current to the servo motor and drives the servo motor; and an information processing device which transmits, to the servo driver, an operation command signal of the servo motor, wherein a movement range limiting device is further provided, which executes, on the basis of the operation command signal from the information processing device, automatic tuning that adjusts a gain in a servo motor control, and which prevents, in the automatic tuning, the servo motor from moving beyond a permissible range by returning the position of the servo motor to a prescribed start position.

Claims

1. A servo system, comprising: a servo motor; a servo driver supplying a driving current to the servo motor to drive the servo motor; and an information processing device sending an operation command signal of the servo motor to the servo driver, wherein a gain adjustment for adjusting a gain in control of the servo motor is performed based on the operation command signal from the information processing device, and the servo system further comprises a movement range limiting device that prevents the servo motor from moving beyond a permissible range by returning a position of the servo motor to a predetermined start position in the gain adjustment, the gain adjustment comprises a gain adjustment process of adjusting the gain by repeatedly moving the servo motor between the start position and a predetermined movement position while changing the gain, and the movement range limiting device returns the servo motor to the start position at the start of the gain adjustment process, or when the servo motor is stopped in the middle of the gain adjustment process.

2. The servo system according to claim 1, wherein the servo driver comprises a check process implementation device that performs a check process of operating the servo motor by the gain obtained by the gain adjustment, the servo driver performs the check process when receiving a check process start command from the information processing device, and the check process implementation device returns the servo motor to the start position at the start of the check process.

3. A gain adjustment method for servo motor control, which adjusts a gain in control of a servo motor, the gain adjustment method comprising: a gain adjustment process of adjusting the gain by repeatedly moving the servo motor between a predetermined start position and a predetermined movement position while changing the gain, wherein a position of the servo motor is returned to the start position at the start of the gain adjustment process, or when the servo motor is stopped in the middle of the gain adjustment process.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a block diagram showing a schematic configuration of the servo system according to an embodiment of the invention.

(2) FIG. 2 is a diagram showing a change of the position of the servo motor in the conventional gain adjustment process and check process.

(3) FIG. 3 is a second diagram showing a change of the position of the servo motor in the conventional gain adjustment process and check process.

(4) FIG. 4 is a diagram showing a change of the position of the servo motor in the gain adjustment process and the check process according to an embodiment of the invention.

(5) FIG. 5 is a second diagram showing a change of the position of the servo motor in the gain adjustment process and the check process according to an embodiment of the invention.

(6) FIG. 6 is a flowchart showing the processing of an automatic tuning routine according to an embodiment of the invention.

DESCRIPTION OF THE EMBODIMENTS

First Embodiment

(7) Hereinafter, an embodiment for carrying out the invention will be described in detail with reference to the drawings as an example. FIG. 1 is a schematic configuration diagram of a servo system 1 according to the present embodiment. The servo system 1 includes an information processing device 2, a servo driver 3, a servo motor 4, and a load device 5 to which the servo motor 4 is physically connected.

(8) The information processing device 2 includes servo setting software 2a for the servo driver 3. The servo setting software 2a has functions of reading the position of the servo motor 4 from the servo driver 3, writing gain parameters of the servo motor 4 to the servo driver 3, reading the gain parameters of the servo motor 4 from the servo driver 3, etc. In addition, the servo driver 3 has a function of issuing an automatic tuning command. Moreover, the information processing device 2 is provided with a storage device 2b, a display device 2c, and a communication part 2d. The storage device 2b is a non-volatile memory that stores the position of the servo motor 4. The display device 2c displays a UI (user interface) provided by the servo setting software 2a. The communication part 2d communicates various pieces of information with the servo driver 3.

(9) The servo driver 3 also has a control part 3a that controls the current supplied to the servo motor 4. The control part 3a has gain parameters internally and calculates the current supplied to the motor according to the gain parameters. In addition, the control part 3a receives the automatic tuning command (to be described later) from the servo setting software 2a and controls the current supplied to the servo motor 4 in automatic tuning. The servo driver 3 further has an output part 3b and a communication part 3c. The output part 3b supplies a direct current to the servo motor 4. The communication part 3c communicates with the servo motor 4 and the information processing device 2.

(10) The servo motor 4 is physically connected to the load device 5 and transmits a rotational torque to the load device 5. The servo motor 4 includes an output part 4a, an encoder 4b, and a communication part 4c. The output part 4a outputs the rotational torque to the load device 5. The encoder 4b detects position (rotational position) information of the servo motor 4. The communication part 4c feeds back the position (rotational position) information to the servo driver 3. The load device 5 is connected to the servo motor 4 and is an object that a user (adjustment operator) tries to move.

(11) Next, the automatic tuning performed in the servo system 1 according to the present embodiment will be described. The automatic tuning is that: in order to set the gain parameters such as position gain and speed gain corresponding to each operation instruction based on the servo setting software 2a that instructs a series of operations, the servo motor 4 is enabled to perform a predetermined operation for updating the gain parameters corresponding to each operation. The automatic tuning is one of the adjustment methods for adjusting the gain in the servo system 1.

(12) The automatic tuning includes a gain adjustment process of adjusting the gain parameters by trial and error while reciprocating the servo motor 4. The automatic tuning may also include a check process that is performed after the gain adjustment process to reciprocate the servo motor 4 based on the gain adjusted in the gain adjustment process to check if the value of the gain is appropriate.

(13) In the gain adjustment process of the automatic tuning, the number of trials is undefined because the load device 5 is operated until the target response characteristic is obtained. In the first trial, the servo motor 4 moves in a fixed direction (forward direction) by a fixed amount from the position at the start (hereinafter, also referred to as the start position) and reaches the position after one trial (hereinafter, also referred to as the movement position). Then, in the second trial, the servo motor 4 moves in the direction opposite to the first trial by the same amount as the first trial and returns to the start position. Here, if the gain adjustment process is completed with an even number of trials, the position of the servo motor 4 at the time when the gain adjustment process is ended is the same as the start position. Therefore, when the check process is subsequently performed, the check process is performed based on the start position.

(14) On the other hand, as shown in FIG. 2, if the gain adjustment process is completed with an odd number of trials, the position of the servo motor 4 at the end of the gain adjustment process is the movement position. Then, in the subsequently performed check process, another trial is performed based on the movement position different from the start position. Also, in the check process, the servo motor 4 is moved in the forward direction by the fixed amount and then returned in the opposite direction. Thus, in the check process, the movement amount of the servo motor 4 in the forward direction temporarily increases. The movement amount of the servo motor 4 at this time may exceed a permissible range of the load device 5 and cause damage to the load device 5.

(15) In addition, in the automatic tuning, as shown in FIG. 3, for example, if the servo motor 4 is stopped for some error in the middle of the gain adjustment process, the gain adjustment process is performed again directly after the error is eliminated. That is, in this case, the gain adjustment process is started based on the position where the servo motor 4 stops. In this case, the movement amount of the servo motor 4 may also exceed the permissible range of the load device 5 and cause damage to the load device 5.

(16) Furthermore, as shown in FIG. 3, when the gain adjustment process is ended in such a situation, if the check process is then started from the state where the servo motor 4 is at the position when the gain adjustment process is ended, similarly, the movement amount of the servo motor 4 may exceed the permissible range of the load device 5 and cause damage to the load device 5 in the check process.

(17) In contrast thereto, in the present embodiment, as shown in FIG. 4, if the gain adjustment process is completed with an odd number of trials, the servo motor 4 is returned to the start position before the check process starts. Accordingly, it is possible to prevent the check process from being started from a state where the servo motor 4 is at a position different from the start position, and it is possible to prevent the servo motor 4 from going beyond the permissible range of the load device 5 in the check process.

(18) Also, in the present embodiment, as shown in FIG. 5, for example, the servo motor 4 is stopped for an error in the gain adjustment process, and the servo motor 4 is returned to the start position before the gain adjustment process is performed again. Accordingly, it is possible to prevent the gain adjustment process from being performed again from a state where the servo motor 4 is at a position different from the start position, and it is possible to prevent the servo motor 4 from going beyond the permissible range of the load device 4.

(19) FIG. 6 shows a flowchart of the processing content of an automatic tuning routine that is executed when automatic tuning is performed in the present embodiment. The routine is one of the servo setting software 2a possessed by the information processing device 2. When the routine is executed, first, in S101, a motor position that serves as the predefined start position, or an actual motor position at the start of the gain adjustment process of the automatic tuning is stored in the storage device 2b. When the process of S101 ends, the processing proceeds to S102.

(20) In S102, the servo motor 4 performs a reciprocating motion and the gain adjustment process is started. That is, the servo motor 4 repeatedly moves between the start position and the movement position to perform a reciprocating motion. The movement position in this case is within the permissible range of the load device 5, and there is no problem as long as the servo motor 4 is moving in this range. When the process of S102 ends, the processing proceeds to S103. In S103, whether any error has occurred in the gain adjustment process is determined.

(21) Here, if it is determined that no error has occurred, the processing proceeds to S104. If it is determined that an error has occurred, the processing proceeds to S109. In S109, the servo motor 4 is urgently stopped. Then, the processing proceeds to S110, and after the error is eliminated, the processing proceeds to S111 and the servo motor 4 is returned to the start position. When the process of S111 ends, the processing proceeds to S112, and whether this error is an error in the check process is determined. Here, since this error is an error in the gain adjustment process, a negative determination is made here. The processing returns to S102, the reciprocating motion of the servo motor 4 is restarted, and the gain adjustment process is performed again.

(22) If it is determined in S103 that no error has occurred, in S104, whether a completion condition has been satisfied is determined. That is, in the gain adjustment process, whether the targeted response characteristic is obtained is checked. Then, if it is determined that the completion condition has not been satisfied, it is determined necessary to further perform the reciprocating motion of the servo motor 4 and the gain adjustment, so the processing returns to S102. On the other hand, if it is determined that the completion condition has been satisfied, the processing proceeds to S105. When the process of S104 ends, the gain adjustment process ends.

(23) In S105, whether the number of trials in the gain adjustment process is an odd number is determined. Here, if the number of trials is determined to be an odd number, the servo motor 4 is at the movement position. Therefore, it is determined that if the processing proceeds to the check process in such a situation, the position of the servo motor 4 may go beyond the permissible range of the load device 5 and cause damage to the load device 5, so the processing proceeds to S106. On the other hand, if the number of trials is determined to be an even number, the servo motor 4 is at the start position. Therefore, it is determined that the position of the servo motor 4 will not go beyond the permissible range of the load device 5 even if the processing proceeds to the check process in such a situation, so the processing proceeds to S107.

(24) In S106, the position of the servo motor 4 is returned to the start position. When S106 ends, the processing proceeds to S107. In S107, the check process is started, and movement of the servo motor 4 between the start position and the movement position is repeated based on the gain adjusted in the gain adjustment process. When the process of S107 ends, the processing proceeds to S108. In S108, whether any error has occurred in the check process is determined. Here, if it is determined that an error has occurred, the processing proceeds to S109. On the other hand, if it is determined that no error has occurred, it is determined that the check process ends normally, so the routine temporarily ends. Since the check process is basically completed with an even number of trials of the servo motor 4 (unlike the gain adjustment process, the number of trials is not undefined), the servo motor 4 has returned to the start position at the time when the routine ends.

(25) Further, if it is determined in the check process that an error has occurred, the servo motor 4 is urgently stopped in S109, the error is eliminated in S110, and the servo motor 4 is returned to the start position in S111. Then, in S112, it is determined whether the error has occurred in the check process. Here, it is determined that the error has occurred in the check process and it is determined necessary to perform the check process again, so the processing returns to S107, and the movement of the servo motor 4 between the start position and the movement position is performed again based on the gain adjusted in the gain adjustment process. In the automatic tuning routine shown in FIG. 6, the information processing device 2 that performs the processes of S105 and S106, and S103 and S108 to S111 corresponds to the movement range limiting device in the present embodiment.

(26) As described above, in the present embodiment, first, whether the number of trials of the servo motor 4 is an odd number or an even number is determined in the gain adjustment process of the automatic tuning. Then, if the number of trials is determined to be an odd number, it is determined that the servo motor 4 is stopped at the movement position, so the position of the servo motor 4 is returned to the start position before the processing moves on to the check process. In addition, if the number of trials of the servo motor 4 is determined to be an even number, it is determined that the servo motor 4 has returned to the start position at this time, so the processing moves on to the check process directly.

(27) Moreover, if it is determined that an error has occurred in the middle of the gain adjustment process or the check process, it is determined that the servo motor 4 is stopped at a position different from the start position, so the position of the servo motor 4 is returned to the start position and then the gain adjustment process or the check process is performed again. According to the present embodiment, by further moving the servo motor 4 from a position different from the start position or from the movement position, it is possible to prevent the servo motor 4 from going beyond the permissible range of the load device 5 and causing damage to the load device 5.

(28) The above embodiment illustrates an example of applying the invention to automatic tuning. However, the invention may also be applied when the user manually adjusts the gain. Similarly, the invention may also be applied when the user manually performs the check process. In addition, the above embodiment illustrates an example that the automatic tuning includes both the gain adjustment process and the check process. However, the invention may be applied to automatic tuning that includes only the gain adjustment process. For example, in FIG. 6, the gain adjustment is ended when the completion condition is satisfied in S104. Then, the servo driver performs the check process when receiving a command to start the check process from the information processing device. In that case, the servo motor is returned to the start position when the check process starts. Further, if the invention is applied to automatic tuning that includes only the gain adjustment process, the servo motor may be returned to the start position when the gain adjustment ends. Furthermore, the above embodiment illustrates that an error has occurred and caused the servo motor to be stopped in the gain adjustment process or the check process. However, the cause of the stop of the servo motor in the gain adjustment process or the check process is not necessarily an error, and the servo motor may be stopped at the discretion of the user.

(29) In addition, the above embodiment illustrates an example that the motor as the start position is stored in the storage device 2b of the information processing device 2. However, the subject that stores and restores the start position is not necessarily the information processing device 2. The start position may be stored in a memory (not shown) included in the servo driver 3 and restored by the servo driver 3. The configuration of the servo system 1 in the above-described embodiment is merely an example, and it is possible to make any change without departing from the spirit of the invention.