Servo driver

Abstract

This invention provides a servo driver that can reduce the frequency of use of dynamic brakes while stopping the servo motor. [Solution] This servo driver is a servo driver that controls a servo motor in a servo system. The servo driver has a dynamic brake used to stop the servo motor. The servo system is provided with a second brake, which is used to stop the servo motor and is different from the dynamic brake. When the servo driver receives a command to stop the servo motor in an emergency, if the estimated braking distance by the second brake is less than or equal to a predetermined target braking distance, it will stop the servo motor using the second brake instead of the dynamic brake.

Description

Technical Field

[0001] The present invention relates to a servo driver. Background Art

[0002] In a servo system, for example, in an emergency or the like, a servo motor may be stopped by a dynamic brake in response to a command from a servo driver (see Patent Document 1). Prior Art Documents Patent Documents

[0003] Patent Document 1 Japanese Unexamined Patent Publication No. Hei 6-315287 Summary of the Invention Problems to be Solved by the Invention

[0004] A servo driver includes a control unit and an inverter unit, and the servo motor may become uncontrollable due to a failure or the like of the inverter unit such as an Intelligent Power Module (IPM). In such a case, in order to make an emergency stop of the servo motor, the control unit uses a dynamic brake to stop the servo motor. However, the use of a dynamic brake increases heat generation of the servo motor. Therefore, frequent use of the dynamic brake increases the load on the servo motor.

[0005] One aspect of the disclosed technology aims to provide a servo driver that can reduce the frequency of use of dynamic brakes while stopping the servo motor. Means for Solving the Problems

[0006] One aspect of the disclosed technology is illustrated by the following servo driver: This servo driver is a servo driver that servo-controls a servo motor in a servo system. The servo driver has a dynamic brake used to stop the servo motor. The servo system is provided with a second brake, which is different from the dynamic brake and is used to stop the servo motor. When the servo driver receives a command to emergency stop the servo motor, if the estimated braking distance by the second brake is less than or equal to a predetermined target braking distance, it will stop the servo motor using the second brake instead of the dynamic brake.

[0007] According to this servo driver, if the braking distance by the second brake is less than or equal to a predetermined target braking distance, the servo motor can be stopped using the second brake instead of the dynamic brake. Therefore, this servo driver can reduce the frequency of use of the dynamic brake. The predetermined target braking distance is determined appropriately based on, for example, the braking distance of the dynamic brake, the required specifications of the servo system including the servo driver, etc. Here, the second brake may be at least one of a third brake provided inside the servo motor and stopping the motor shaft of the servo motor, and a fourth brake provided on the load connected to the motor shaft and stopping the load.

[0008] The servo driver may further have the following features. The second brake includes a third brake provided within the servo motor for stopping the motor shaft of the servo motor, and a fourth brake provided on the load connected to the motor shaft for stopping the load. The servo driver then controls the third brake and the fourth brake. The servo motor is stopped using a brake that achieves a braking distance that is less than or equal to the predetermined target braking distance, and close to the predetermined target braking distance. With a servo driver having such features, the servo driver can be stopped using a brake whose braking distance is closest to the predetermined target braking distance. Therefore, even when the servo motor is stopped using the second brake instead of the dynamic brake, the servo driver can stop the servo motor at a braking distance as close as possible to the predetermined target braking distance.

[0009] This servo driver may further have the following features. The dynamic brake uses a heat consumption unit that consumes the electricity generated by the rotation of the motor shaft of the servo motor as heat. The servo driver estimates the temperature of the heat consumption unit that is expected to occur when the dynamic brake is used, and if the estimated temperature is below a predetermined limit temperature, it stops the servo motor using the dynamic brake instead of the second brake. A servo driver with such features can use the dynamic brake while suppressing the temperature of the heat consumption unit from rising above the limit temperature. In other words, this servo driver suppresses the frequent use of the dynamic brake that would cause the temperature of the heat consumption unit to rise above the limit temperature.

[0010] The servo driver may further have the following feature: The servo driver will stop the servo motor using the dynamic brake instead of the second brake if the elapsed time since the last use of the dynamic brake is below a threshold and the estimated temperature is below the limit temperature. With a servo driver having such a feature, the dynamic brake will only be used when the elapsed time is above the threshold, thus suppressing the frequent use of the dynamic brake.

[0011] The servo driver may further have the following features: If the estimated braking distance by the second brake is greater than the predetermined target braking distance, the servo driver will stop the servo motor using the dynamic brake instead of the second brake. In a servo driver with such features, if there is no second brake that can achieve the predetermined target braking distance, the servo motor will stop using the dynamic brake. Therefore, the servo driver is designed to prevent the braking distance from exceeding the predetermined target braking distance. [Effects of the Invention]

[0012] This servo driver can reduce the frequency of using dynamic braking when stopping the servo motor. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 shows an example of a servo system according to an embodiment. [Figure 2] Figure 2 shows an example of a processing block for a servo driver according to an embodiment. [Figure 3] Figure 3 is the first figure showing an example of a brake management table stored in the memory of the servo driver in an embodiment. [Figure 4] Figure 4 is a second figure showing an example of a brake management table stored in the servo driver's memory in an embodiment. [Figure 5] Figure 5 shows an example of the processing flow of the determination process by which the determination unit of the servo driver according to the embodiment determines whether or not the dynamic brake mechanism can be used. [Modes for carrying out the invention]

[0014] <Examples of application> An example of the application of the present invention will now be described. An example of the application of the present invention is a servo driver 2 used in the servo system 100 illustrated in Figure 1. The servo driver 2 servo-controls a servo motor 3. The servo driver 2 is provided with a dynamic brake mechanism DB1 used for emergency stopping of the servo motor 3. The servo motor 3 is provided with an unexcited electromagnetic brake 311 that stops the servo motor 3. A load 5 is also connected to the motor shaft 317 of the servo motor 3. The load 5 is provided with a precision stage 52 that moves on a screw shaft 51 in accordance with the rotation of the motor shaft 317. The load 5 is also provided with an external brake 53 that stops the precision stage 52. The external brake 53 is a brake provided outside the servo motor 3, and when the precision stage 52 is stopped by the external brake 53, the motor shaft 317 is also stopped.

[0015] In the dynamic braking mechanism DB1, the rotation of the motor shaft 317 is stopped by dissipating the heat generated by the rotation of the motor shaft 317 through the dynamic braking resistor R10 and the stator 319. Frequent use of the dynamic braking mechanism DB1 may cause the dynamic braking resistor R10 and the stator 319 of the servo motor 3 to become excessively hot. Therefore, the frequency of use of the dynamic braking mechanism DB1 is often limited.

[0016] In this application example, among the external brake 53 and the non-excitation-operated electromagnetic brake 311, the brake whose estimated braking distance is less than or equal to the target braking distance is used to stop the servo motor 3 in place of the dynamic brake mechanism DB1. Therefore, according to this application example, the servo motor 3 can be stopped at or below the target braking distance while reducing the frequency of use of the dynamic brake mechanism DB1, thereby protecting the servo motor 3. Furthermore, in this application example, braking at or below the target braking distance is achieved even when using a brake other than the dynamic brake mechanism DB1. The target braking distance can be appropriately determined, for example, based on the braking distance of the dynamic brake mechanism DB1.

[0017] <Embodiment> Hereinafter, embodiments will be described with reference to the drawings. Fig. 1 is a diagram showing an example of a servo system 1 according to an embodiment. A servo system 100 includes a PLC 1, a servo driver 2, and a servo motor 3. A load 5 is connected to a motor shaft 317 of the servo motor 3 via a coupling 4. The servo system 100 is a system that drives the load 5 by servo-controlling the servo motor 3 via the servo driver 2.

[0018] The load 5 includes a screw shaft 51, a precision stage 52, and an external brake 53. A precision stage 52 is disposed on the screw shaft 51. The precision stage 52 is displaced on the screw shaft 51 by driving of the servo motor 3. Stoppers (not shown) are provided at both ends of a driving range of the precision stage 52 along the screw shaft 51. Impact generated when the precision stage 52 contacts the stopper is reduced as much as possible by torque control of the servo motor 3. A work 8 is placed on the precision stage 52. Although the servo system 100 illustrated in Fig. 1 is provided with one drive shaft driven by the servo motor 3 as described above, two or more drive shafts may be provided.

[0019] Further, the precision stage 52 is fixed so as not to be displaced on the screw shaft 51 when the external brake 53 is locked. As a result, the motor shaft 317 of the servo motor 3 is also stopped. A holding force of the external brake 53 (a force for fixing the precision stage 52 to the screw shaft 51) is set to be larger than an instantaneous maximum torque of the servo motor 3, for example. Therefore, when the external brake 53 is locked, even if the servo motor 3 rotates, the precision stage 52 is not displaced on the screw shaft 51. Further, the precision stage 52 becomes displaceable on the screw shaft 51 when the external brake 53 is turned off. The external brake 53 is an example of "a second brake" and "a fourth brake".

[0020] The PLC 1 outputs a command signal to the servo driver 2. The PLC 1 functions as, for example, a monitoring device for the servo driver 2 by executing processing in accordance with a prepared program in advance.

[0021] The servo driver 2 receives command signals from the PLC 1. Furthermore, the servo driver 2 receives feedback signals from the servo motor 3. The servo driver 2 supplies power to the servo motor 3 via the power line 62 from a predetermined power supply circuit 20. The servo driver 2 has a servo system that performs feedback control using a position controller, a speed controller, a current controller, etc., and uses these controllers to servo control and drive the servo motor 3.

[0022] The servo motor 3 includes a motor body 31 and an encoder 32. The servo motor 3 is, for example, an AC servo motor. The servo motor 3 and the servo driver 2 are connected by an encoder cable 61 and a power line 62. The power line 62 includes a power line 620 and a brake line 624. The power line 620 includes a U-phase power line 621, a V-phase power line 622, and a W-phase power line 623. The power line 620 is a wire used to supply drive power from the servo driver 2 to the servo motor 3. In the power line 620, U-phase power is supplied by the U-phase power line 621, V-phase power is supplied by the V-phase power line 622, and W-phase power is supplied by the W-phase power line 623. The brake line 624 is a wire used to supply power used to release the unexcited electromagnetic brake 311 from the servo driver 2 to the servo motor 3.

[0023] The servo motor 3 is powered by a drive current from the servo driver 2 via the power line 620. The stator 319 of the servo motor 3 is provided for the U, V, and W phases respectively, and generates a magnetic field using the supplied drive current. The rotor 318 of the servo motor 3 rotates the motor shaft 317 by receiving the magnetic field from the stator 319. The encoder 32 detects the displacement of the motor shaft 317. Examples of the displacement of the motor shaft 317 detected by the encoder 32 include the direction of rotation, the amount of rotation, and the rotation speed of the motor shaft 317. The encoder 32 outputs a feedback signal indicating the detected displacement to the servo driver 2 via the encoder cable 61.

[0024] The servo motor 3 also has a non-excitation-operated electromagnetic brake 311 as a mechanism for stopping the motor shaft 317. The non-excitation-operated electromagnetic brake 311 includes a hub 312, a brake lining 313, a movable core 314, a spring 315, and an electromagnetic coil 316. When the non-excitation-operated electromagnetic brake 311 is not receiving power from the servo driver 2 via the brake line 624, no magnetic field is generated by the electromagnetic coil 316, so the movable core 314 is not attracted to the electromagnetic coil 316. Therefore, the movable core 314 is pressed against the brake lining 313 by the elastic force of the spring 315. As a result, the rotation of the motor shaft 317 is stopped when the brake lining 313 is sandwiched between the hub 312 and the movable core 314. The non-excitation-operated electromagnetic brake 311 is an example of a "second brake" and a "third brake".

[0025] When the servo motor 3 receives power from the servo driver 2 via the brake wire 624, the electromagnetic coil 316 generates a magnetic field. The magnetic force of the electromagnetic coil 316 pulls the movable iron core 314 away from the brake lining 313. As a result, the rotation of the motor shaft 317 becomes free, and the motor shaft 317 rotates in accordance with the drive current from the servo driver 2. In other words, in the unexcited electromagnetic brake 311, if power is not supplied from the servo driver 2 via the brake wire 624, the brake locks. Also, in the unexcited electromagnetic brake 311, if power is not supplied from the servo driver 2 via the brake wire 624, the brake locks. When power is supplied via the 624 line, the brakes are released.

[0026] Furthermore, the servo driver 2 can also stop the motor shaft 317 using a dynamic brake mechanism DB1. The dynamic brake mechanism DB1 includes a dynamic brake resistor R10, a U-phase switch SW1, a V-phase switch SW2, a W-phase switch SW3, and a closed circuit C1. The dynamic brake resistor R10 includes a U-phase resistor R11 provided in the U-phase, a V-phase resistor R12 provided in the V-phase, and a W-phase resistor R13 provided in the W-phase. When the servo driver 2 uses the dynamic brake mechanism DB1, it turns on the U-phase switch SW1 provided in the U-phase, the V-phase switch SW2 provided in the V-phase, and the W-phase switch SW3 provided in the W-phase to form a closed circuit including the U-phase resistor R11, the V-phase resistor R12, the W-phase resistor R13, and the closed circuit C1. The motor shaft 317 is then stopped by dissipating the heat generated by the rotation of the motor shaft 317 into the dynamic brake resistor R10 and the stator 319. To protect the dynamic brake resistor R10 and stator 319, the frequency of use of the dynamic brake mechanism DB1 is limited. For example, the frequency of use of the dynamic brake mechanism DB1 is limited to less than once every few minutes. The dynamic brake resistor R10 and stator 319 are examples of "heat-consuming parts". The dynamic brake mechanism DB1 is an example of a "dynamic brake".

[0027] The servo driver 2 can be considered an information processing device equipped with a processor and memory. Figure 2 shows an example of a processing block of the servo driver 2 according to an embodiment. The servo driver 2 includes a servo control unit 21, a determination unit 22, and a brake drive unit 23. The servo driver 2 realizes each processing block, such as the servo control unit 21, determination unit 22, and brake drive unit 23 exemplified in Figure 2, by having the processor execute a program stored in memory.

[0028] The servo control unit 21 servo-controls the servo motor 3 using a servo system that performs feedback control using a position controller, speed controller, current controller, etc., based on command signals from the PLC 1 and feedback signals from the servo motor 3.

[0029] The determination unit 22, for example, when it receives a stop command from the PLC1 instructing the servo motor 3 to stop, determines whether the dynamic brake mechanism DB1 can be used. If the determination unit 22 determines that the dynamic brake mechanism DB1 cannot be used, it decides whether to use the non-excitation type electromagnetic brake 311 or the external brake 53 instead of the dynamic brake mechanism DB1.

[0030] The determination unit 22 determines whether the dynamic brake mechanism DB1 can be used, for example, based on the elapsed time since the last use of the dynamic brake mechanism DB1 and the estimated temperature of the stator 319 estimated when the dynamic brake mechanism DB1 is used. The determination unit 22 stores the end time when the dynamic brake mechanism DB1 is used in the memory of the servo driver 2, for example, each time the dynamic brake mechanism DB1 is used. The determination unit 22 may also calculate the elapsed time based on the end time previously stored in the memory of the servo driver 2 and the current time.

[0031] Furthermore, the determination unit 22 obtains the current temperature of the stator 319 (before using the dynamic brake mechanism DB1) by means of means such as a thermometer. The determination unit 22 also estimates the temperature rise of the stator 319 when the dynamic brake mechanism DB1 is used. For example, the following (Equation 1) can be used to estimate the temperature rise.

number

[0032] In (Equation 1), K is a proportionality constant corresponding to the type of servo motor 3, ω is the rotational speed of the motor shaft 317, and J is the inertia. The determination unit 22 can estimate the temperature rise of the stator 319 when the dynamic brake mechanism DB1 is used by using (Equation 1). The determination unit 22 then estimates the temperature of the stator 319 after using the dynamic brake mechanism DB1 by adding the estimated temperature rise to the current temperature of the stator 319 measured by a thermometer, for example.

[0033] The determination unit 22 determines, for example, that the dynamic brake mechanism DB1 can be used if the elapsed time is equal to or greater than the threshold and the estimated temperature is equal to or less than the limit temperature. The determination unit 22 also determines, for example, that the dynamic brake mechanism DB1 cannot be used if the elapsed time is less than the threshold or the estimated temperature is higher than the limit temperature.

[0034] Here, the determination unit 22 may acquire brake constraints when selecting the brake to use. Brake constraints are, for example, information indicating whether the external brake 53 and the non-excitation-operated electromagnetic brake 311 can be used. Brake constraints include, for example, the presence or absence of the external brake 53 and the non-excitation-operated electromagnetic brake 311, and the user's specification of whether the non-excitation-operated electromagnetic brake 311 can be used or not. Based on these conditions, whether the external brake 53 and the non-excitation-operated electromagnetic brake 311 can be used or not can be determined, for example, by the following (Equation 2).

number

[0035] In (Equation 2), ExBrake is a value indicating the presence or absence of the external brake 53, which is "1" if the external brake 53 is present and "0" if it is not present. InBrake_user is a value indicating whether the user can use the unexcited electromagnetic brake 311, which is "1" if the user allows it to be used and "0" if the user does not allow it to be used. InBrake_system is a value indicating the presence or absence of the unexcited electromagnetic brake 311, which is "1" if the unexcited electromagnetic brake 311 is present and "0" if it is not present. According to (Equation 2), if Ex_Brake_able is "1", the external brake 53 is usable, and if ExBrake_able is "0", the external brake 53 is not usable. Also, according to (Equation 2), if InBrake_able is "1", the unexcited electromagnetic brake 311 is usable, and if InBrake_able is "0", the unexcited electromagnetic brake 311 is not usable.

[0036] If the determination unit 22 determines that the dynamic brake mechanism DB1 is unusable, it estimates the braking distance for both the unexcited electromagnetic brake 311 and the external brake 53. The determination unit 22 then selects the brake whose estimated braking distance is closest to a preset target braking distance from the unexcited electromagnetic brake 311 and the external brake 53 to be used to stop the servo motor 3. For example, the following equation (3) is used to estimate the braking distance.

number

[0037] In equation (3), J is the inertia, ω0 is the rotational speed of the motor shaft 317 at the start of braking, and T is the braking torque. The braking torque varies depending on the combination of brakes used. n is the braking distance estimated by (Equation 3). In this embodiment, S nThe value of n is selected from three possible values: 1, 2, and 3. When n is 1 (case S1), it indicates the braking distance of the external brake 53; when n is 2 (case S2), it indicates the braking distance of the non-excitation-operated electromagnetic brake 311; and when n is 3 (case S3), it indicates the braking distance when both the external brake 53 and the non-excitation-operated electromagnetic brake 311 are used in combination.

[0038] Furthermore, to estimate the braking distance considering whether or not the brakes can be used, for example, the following formula (Equation 4) can be used.

number

[0039] In (Equation 4), J is the inertia, ω0 is the rotational speed of the motor shaft 317 at the start of braking, and T EX The braking torque of the external brake 53, T IN is the braking torque of the motor shaft 317. Also, S1, S2, and S3 are the same as in (Equation 3). In (Equation 4), the braking distance of an unusable brake is "0". For example, if the external brake 53 is unusable, ExBrake_able becomes "0", so the value of S1 becomes "0". The estimated braking distance is stored, for example, in the brake management table 221 described later.

[0040] Figure 3 shows an example of a brake management table 221 stored in the memory of the servo driver 2 in an embodiment. The brake management table 221 stores the correspondence between the combination of the external brake 53 and the non-excitation-operated electromagnetic brake 311 used to stop the servo motor 3 and the braking distance. In Figure 3, the non-excitation-operated electromagnetic brake 311 is labeled as "internal brake". In "Condition 1" of the brake management table 221, the braking distance when the external brake 53 is used but the non-excitation-operated electromagnetic brake 311 is not used is stored as "S1". In "Condition 2" of the brake management table 221, the braking distance when the external brake 53 is not used but the non-excitation-operated electromagnetic brake 311 is used is stored as "S2". In "Condition 3" of the brake management table 221, the braking distance when both the external brake 53 and the non-excitation-operated electromagnetic brake 311 are used is stored as "S3". In "Condition 4" of the brake management table 221, the braking distance when neither the external brake 53 nor the non-excitation-operated electromagnetic brake 311 is used is stored as "S4". The braking distances "S1", "S2", "S3", and "S4" are stored as results estimated by, for example, (Equation 3). Note that the braking distances "S1", "S2", "S3", and "S4" may be measured in advance when the servo system 100 is constructed, and the measured results may be stored in the brake management table 221.

[0041] The brake drive unit 23 uses the brake selected by the determination unit 22 from among the external brake 53, the non-excitation type electromagnetic brake 311, and the dynamic brake mechanism DB1. Stop servo motor 3.

[0042] <Processing Flow> Figures 4 and 5 show an example of the processing flow of the determination process by the determination unit 22 of the servo driver 2 according to this embodiment, which determines whether or not the dynamic brake mechanism DB1 can be used. The processing flow of the determination process by the determination unit 22, which determines whether or not the dynamic brake mechanism DB1 can be used, will be described below with reference to Figures 4 and 5. In Figures 4 and 5, the dynamic brake mechanism DB1 is referred to as "DB".

[0043] In step S1, the servo driver 2 receives a stop command from the PLC 1, for example, which instructs the servo motor 3 to stop. The stop command from the PLC 1 is output, for example, when some kind of abnormality occurs.

[0044] In step S2, the determination unit 22 determines whether the elapsed time since the last use of the dynamic brake mechanism DB1 is greater than or equal to a threshold. The determination unit 22 makes a positive determination if the elapsed time is greater than or equal to a threshold previously stored in the memory of the servo driver 2. The determination unit 22 makes a negative determination if the elapsed time is less than a threshold previously stored in the memory of the servo driver 2. If a positive determination is made (YES in step S2), the process proceeds to step S3. If a negative determination is made (NO in step S2), the process proceeds to step S11.

[0045] In step S3, the determination unit 22 estimates the temperature rise of the stator 319. The determination unit 22 estimates the temperature rise of the stator 319 using, for example, (Equation 1).

[0046] In step S4, the determination unit 22 obtains the temperature of the stator 319 by means of, for example, a thermometer. The determination unit 22 adds the obtained temperature and the temperature rise value estimated in step S3 to estimate the temperature of the stator 319 when the dynamic brake mechanism DB1 is used. The determination unit 22 may also consider a predetermined margin when estimating the temperature of the stator 319. That is, the determination unit 22 may add the obtained temperature, the temperature rise value estimated in step S3, and the margin to estimate the temperature of the stator 319 when the dynamic brake mechanism DB1 is used. By adding a margin when estimating the temperature of the stator 319, the dynamic brake mechanism DB1 can be used with a margin of safety relative to the limit temperature.

[0047] In step S5, the determination unit 22 determines whether the temperature of the stator 319 when using the dynamic brake mechanism DB1 estimated in step S4 is below the limit temperature. If it is below the limit temperature (YES in step S5), the process proceeds to step S6. If it is not below the limit temperature (NO in step S5), the process proceeds to step S11.

[0048] In step S11, the determination unit 22 acquires the brake constraint conditions. As described above, the brake constraint conditions are information indicating whether the external brake 53 and the non-excitation type electromagnetic brake 311 can be used. The determination unit 22 acquires the brake constraint conditions, for example, using (Equation 2) above.

[0049] In step S12, the determination unit 22 estimates the braking distance of each brake that is deemed usable under the brake constraint conditions obtained in step S11. The determination unit 22 estimates the braking distance of each brake using, for example, the above-mentioned (Equation 3).

[0050] In step S13, the determination unit 22 determines that the braking distance estimated in step S12 is the target braking distance Determine whether there are any brakes that are less than detached. If there are (YES in step S13), the process proceeds to step S14. If there are no brakes (NO in step S13), the process proceeds to step S6.

[0051] In step S14, the determination unit 22 selects the brake whose braking distance is closest to the target braking distance from among the brakes whose braking distance was determined to be less than the target braking distance in step S13, and uses that brake to stop the servo motor 3. The brake drive unit 23 uses the selected brake to stop the servo motor 3.

[0052] <Effects of the Embodiment> In this embodiment, if there is a brake among the external brake 53 and the non-excitation type electromagnetic brake 311 that can achieve a braking distance less than the target braking distance, the servo motor 3 can be stopped using that brake instead of the dynamic brake mechanism DB1. Therefore, according to this embodiment, the frequency of use of the dynamic brake mechanism DB1 can be reduced.

[0053] In this embodiment, the servo motor 3 is stopped using the brake that has the braking distance closest to the target braking distance among the brakes capable of achieving a braking distance less than the target braking distance. Therefore, according to this embodiment, the servo motor 3 can be stopped at a braking distance close to the target braking distance even when an abnormality occurs.

[0054] In this embodiment, the temperature of the stator 319 when the dynamic brake mechanism DB1 is used is estimated, and if the estimated temperature of the stator 319 is higher than the limit temperature, the use of the dynamic brake mechanism DB1 is suppressed. Therefore, according to this embodiment, the servo motor 3 is protected because the overheating of the stator 319 due to the use of the dynamic brake mechanism DB1 is suppressed.

[0055] In this embodiment, if the elapsed time since the last use of the dynamic brake mechanism DB1 is less than a threshold, the use of the dynamic brake mechanism DB1 is suppressed. Therefore, according to this embodiment, the frequency of use of the dynamic brake mechanism DB1 can be suppressed.

[0056] In this embodiment, if a braking distance less than the target braking distance cannot be achieved using either the external brake 53 or the non-excitation-operated electromagnetic brake 311, the dynamic brake mechanism DB1 is used to stop the servo motor 3. Therefore, according to this embodiment, even if a braking distance less than the target braking distance cannot be achieved using either the external brake 53 or the non-excitation-operated electromagnetic brake 311, the servo motor 3 can be stopped before the target braking distance. Furthermore, according to this embodiment, even if the dynamic brake resistor R10 is damaged due to the use of the dynamic brake mechanism DB1, the servo motor 3 (stator 319) can be stopped without damage, thus protecting the servo motor 3.

[0057] <Variation> In this embodiment, an external brake 53 is provided, but the external brake 53 may be omitted, or multiple external brakes 53 may be provided. Also, in this embodiment, the servo motor 3 is provided with a non-excitation-operated electromagnetic brake 311, but the non-excitation-operated electromagnetic brake 311 may be omitted. It is sufficient that a brake to stop the servo motor 3 is provided in addition to the dynamic brake mechanism DB1.

[0058] In the embodiment described above, the temperature of the stator 319 was estimated when the dynamic brake mechanism DB1 was used, but the temperature of the dynamic brake resistor R10 may also be estimated when the dynamic brake mechanism DB1 is used. For estimating the temperature of the dynamic brake resistor R10, for example, an equation relating to the temperature rise value, such as equation (1) above, may be used. If the estimated temperature of the dynamic brake resistor R10 is higher than a predetermined limit temperature, the use of the dynamic brake mechanism DB1 may be suppressed. Alternatively, the temperatures of both the stator 319 and the dynamic brake resistor R10 when the dynamic brake mechanism DB1 is used may be estimated. In such a case, if the estimated temperature of at least one of the stator 319 and the dynamic brake resistor R1 is higher than a predetermined limit temperature, the use of the dynamic brake mechanism DB1 should be suppressed.

[0059] The embodiments and modifications described above can be combined.

[0060] <Note 1> A servo driver (2) that controls a servo motor (3) in a servo system (100), The servo driver (2) has a dynamic brake (DB1) used to stop the servo motor (3), The servo system (100) is provided with a second brake (53, 311) which is used to stop the servo motor (3) and is different from the dynamic brake (DB1). The servo driver (2) is When an emergency stop command is received for the servo motor (3), if the estimated braking distance by the second brake (53, 311) is less than or equal to a predetermined target braking distance, the servo motor is stopped using the second brake (53, 311) instead of the dynamic brake (DB1). Servo driver (2). <Note 2> The aforementioned second brake (53, 311) is, A third brake (311) is provided within the servo motor (3) to stop the motor shaft (317) of the servo motor (3), and The motor shaft (317) is connected to a load (5), and includes at least one of the following: a fourth brake (53) that stops the load (5), The servo driver described in Appendix 1. <Note 3> The aforementioned second brake (53, 311) is, A third brake (311) is provided within the servo motor (3) and stops the motor shaft (317) of the servo motor (3), A fourth brake (53) is provided on the load (5) connected to the motor shaft (317) and is used to stop the load (5), The servo driver (2) is The servo motor (3) is stopped using the brake among the third brake (311) and the fourth brake (53) that achieves a braking distance that is less than or equal to the predetermined target braking distance and close to the predetermined target braking distance. The servo driver (2) as described in Appendix 1. <Note 4> In the aforementioned dynamic brake (DB1), a heat consumption unit (R10, 319) is used that consumes the electricity generated by the rotation of the motor shaft (317) of the servo motor (3) as heat. The servo driver (2) is When the dynamic brake (DB1) is used, the temperature of the heat consumption section (R10, 319) is estimated, and if the estimated temperature is below a predetermined limit temperature, The servo motor (3) is stopped using the dynamic brake (DB1) instead of the second brake (53, 311). The servo driver (2) as described in Appendix 1 or Appendix 2. <Note 5> The servo driver (2) is If the elapsed time since the last use of the dynamic brake (DB1) is below a threshold, and the estimated temperature is below the limit temperature, the servo motor (3) is stopped using the dynamic brake (DB1) instead of the second brake (53, 311). The servo driver (2) described in Appendix 4. <Note 6> The servo driver (2) stops the servo motor (3) using the dynamic brake (DB1) instead of the second brake (53, 311) if the estimated braking distance by the second brake (53, 311) is greater than the predetermined target braking distance. A servo driver (2) as described in any one of the appendices 1 to 5. [Explanation of Symbols]

[0061] 1··PLC 2. Servo driver 3. Servo motor 4. Coupling 5. Load 8. Work 21. Servo Control Unit 22... Judgment section 23. Brake drive unit 31. Motor body 32 encoders 51. Screw shaft 52. Precision Stage 53. External brakes 61. Encoder Cable 62. Power lines 221 ··Brake Management Table 100 Servo System 311. Non-excitation type electromagnetic brake 312 hub 313. Brake lining 314. Movable Iron Core 315 ··Spring 316. Electromagnetic coil 317. Motor shaft 318 Rotor 319 stater 620·Power line 621...U phase power line 622...V phase power line 623...W phase power line 624 ··Brake wire C1...Closed circuit DB1 Dynamic Brake Mechanism R10 Dynamic Brake Resistor R11...U phase resistor R12...V phase resistor R13...W phase resistor SW1··U-phase switch SW2 ··V-phase switch SW3··W phase switch

Claims

1. A servo motor control servo driver in a servo system, The servo driver has a dynamic brake used to stop the servo motor. The servo system is provided with a second brake, which is used to stop the servo motor and is different from the dynamic brake. The aforementioned servo driver When an emergency stop command for the servo motor is received, if the estimated braking distance using the second brake is less than or equal to a predetermined target braking distance, the servo motor is stopped using the second brake instead of the dynamic brake. Servo driver.

2. The aforementioned second brake is, A third brake is provided within the servo motor to stop the motor shaft of the servo motor, and A fourth brake provided on a load connected to the motor shaft, which stops the load, is included, at least one of the following: The servo driver according to claim 1.

3. The aforementioned second brake is, A third brake is provided within the servo motor to stop the motor shaft of the servo motor, It includes a fourth brake provided on the load connected to the motor shaft, which stops the load, The aforementioned servo driver The servo motor is stopped using the brake among the third brake and the fourth brake that achieves a braking distance that is less than or equal to the predetermined target braking distance and close to the predetermined target braking distance. The servo driver according to claim 1.

4. In the aforementioned dynamic brake, a heat consumption unit is used that consumes the electricity generated by the rotation of the motor shaft of the servo motor as heat. The aforementioned servo driver The temperature of the heat-consuming part expected when the dynamic brake is used is estimated, and if the estimated temperature is below a predetermined limit temperature, the servo motor is stopped using the dynamic brake instead of the second brake. The servo driver according to claim 1.

5. The aforementioned servo driver If the elapsed time since the last use of the dynamic brake is below a threshold, and the estimated temperature is below the limit temperature, the servo motor is stopped using the dynamic brake instead of the second brake. The servo driver according to claim 4.

6. The servo driver stops the servo motor using the dynamic brake instead of the second brake when the estimated braking distance using the second brake is greater than the predetermined target braking distance. A servo driver according to any one of claims 1 to 5.

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