Servo motor, control method thereof and servo driver

Abstract

The control method of the servo motor comprises the steps that in the precharging process of a bus capacitor, when the voltage of the bus capacitor is smaller than a preset first voltage value, short circuit at the two ends of a precharging resistor is relieved, and short circuit is established between at least two phases of the alternating current output end of an inversion unit; and in the pre-charging process of the bus capacitor, when the voltage of the bus capacitor is larger than a first voltage value, the two ends of the pre-charging resistor are in short circuit, and short circuit between any two phases of the alternating current output end of the inversion unit is relieved. The control method is beneficial to reducing the cost required for increasing the braking function. In addition, the invention also provides a servo driver and a servo motor.

Description

Technical Field

[0001] The present invention relates to the field of motor drives, and in particular to a control method for a servo motor. The present invention also relates to a servo drive using the control method and a servo motor including the servo drive. Background Art

[0002] In the application of servo drives, in order to achieve rapid stopping of the motor in the event of a main power failure, a braking function is usually added to the servo drive. Currently, the software development cost and hardware cost of adding the braking function are relatively high. Summary of the Invention

[0003] The object of the present invention is to provide a control method for a servo motor, which is conducive to reducing the cost required to add a braking function.

[0004] Another object of the present invention is to provide a servo drive, which is conducive to reducing the cost required to add a braking function.

[0005] Still another object of the present invention is to provide a servo motor, which is conducive to reducing the cost required to add a braking function.

[0006] The present invention provides a control method for a servo motor. The servo motor includes a servo drive and a motor. The servo drive includes a rectification unit, a DC bus, an inversion unit, a bus capacitor, and a pre-charge resistor. The rectification unit is connected to an AC main power supply and converts alternating current into direct current. The DC bus is connected to the DC output terminal of the rectification unit. The inversion unit is connected to the DC bus and converts direct current into alternating current. The motor is connected to the AC output terminal of the inversion unit. The bus capacitor and the pre-charge resistor are connected in series between the positive and negative poles of the DC bus. The two ends of the pre-charge resistor can be short-circuited through a circuit. The control method includes: during the pre-charging process of the bus capacitor, when the voltage of the bus capacitor is less than a preset first voltage value, the short circuit at both ends of the pre-charge resistor is released, and a short circuit is established between at least two phases of the AC output terminal of the inversion unit; and during the pre-charging process of the bus capacitor, when the voltage of the bus capacitor is greater than the first voltage value, the two ends of the pre-charge resistor are short-circuited, and the short circuit between any two phases of the AC output terminal of the inversion unit is released.

[0007] The control method of the servo motor can associate the activation and release of short-circuit braking with the switching of the charging mode of the pre-charge circuit during the startup process of the servo motor, which is conducive to reducing the cost required to add a braking function.

[0008] In another exemplary embodiment of the control method of the servo motor, the control method further includes: during the discharging process of the bus capacitor after the main power supply is powered off, when the voltage of the bus capacitor is greater than a preset second voltage value, short-circuit both ends of the pre-charge resistor and release the short-circuit between any two phases of the AC output terminals of the inverter unit, where the second voltage value is less than the first voltage value; and during the discharging process of the bus capacitor after the main power supply is powered off, when the voltage of the bus capacitor is less than the second voltage value, release the short-circuit between both ends of the pre-charge resistor and establish a short-circuit between at least two phases of the AC output terminals of the inverter unit. This helps to further reduce the cost required to add the braking function.

[0009] In yet another exemplary embodiment of the control method of the servo motor, the control method further includes: when the bus capacitor is fully charged, short-circuit both ends of the pre-charge resistor and release the short-circuit between any two phases of the AC output terminals of the inverter unit. This helps to further reduce the cost required to add the braking function.

[0010] In still another exemplary embodiment of the control method of the servo motor, the control method further includes: during the pre-charging process of the bus capacitor, when the voltage of the bus capacitor is less than the first voltage value, control the inverter unit to stop output; and during the pre-charging process of the bus capacitor, when the voltage of the bus capacitor is greater than the first voltage value, control the inverter unit to supply power to the motor. This helps to further reduce the cost required to add the braking function.

[0011] In still another exemplary embodiment of the control method of the servo motor, the control method further includes: during the discharging process of the bus capacitor after the main power supply is powered off, when the voltage of the bus capacitor is greater than a preset third voltage value, control the inverter unit to supply power to the motor, where the third voltage value is less than or equal to the first voltage value and greater than the second voltage value; and during the discharging process of the bus capacitor after the main power supply is powered off, when the voltage of the bus capacitor is less than the third voltage value, control the inverter unit to switch to the free parking mode or the decelerated parking mode. This helps to improve the safety of parking.

[0012] In still another exemplary embodiment of the control method of the servo motor, the control method further includes: when the bus capacitor is fully charged, control the inverter unit to supply power to the motor.

[0013] The present invention also provides a servo driver for driving a motor. The servo driver includes a rectification unit, a DC bus, an inversion unit, a pre-charge circuit, a switching unit, a voltage detection unit, and a control unit. The rectification unit is used to connect to an AC main power supply and can convert alternating current into direct current. The DC bus is connected to the DC output terminal of the rectification unit. The inversion unit is connected to the DC bus and can convert direct current into alternating current. The AC output terminal of the inversion unit is used to connect to the motor. The pre-charge circuit includes a bus capacitor and a pre-charge resistor. The bus capacitor and the pre-charge resistor are connected in series between the positive and negative poles of the DC bus. The switching unit is connected to the pre-charge circuit to be able to short-circuit both ends of the pre-charge resistor. The switching unit is connected to at least two phases of the AC output terminal of the inversion unit to be able to establish a short circuit between at least two phases of the AC output terminal of the inversion unit. The voltage detection unit can detect the voltage of the bus capacitor and generate a voltage signal. The control unit can control the switching unit according to the voltage signal so that: during the pre-charge of the bus capacitor, when the voltage of the bus capacitor is less than a preset first voltage value, the short circuit across the pre-charge resistor is removed, and a short circuit is established between at least two phases of the AC output terminal of the inversion unit; during the pre-charge of the bus capacitor, when the voltage of the bus capacitor is greater than the first voltage value, both ends of the pre-charge resistor are short-circuited, and the short circuit between any two phases of the AC output terminal of the inversion unit is removed.

[0014] For this servo driver, by detecting the voltage of the bus capacitor, the switching of the short-circuit braking state and the switching of the charging mode of the pre-charge circuit can be synchronously controlled. This servo driver is beneficial for reducing the cost required to add a braking function.

[0015] In another illustrative embodiment of the servo driver, the control unit can control the switching unit according to the voltage signal so that: during the discharge of the bus capacitor after the main power supply is powered off, when the voltage of the bus capacitor is greater than a preset second voltage value, both ends of the pre-charge resistor are short-circuited, and the short circuit between any two phases of the AC output terminal of the inversion unit is removed, and the second voltage value is less than the first voltage value; during the discharge of the bus capacitor after the main power supply is powered off, when the voltage of the bus capacitor is less than the second voltage value, the short circuit across the pre-charge resistor is removed, and a short circuit is established between at least two phases of the AC output terminal of the inversion unit. This is beneficial for further reducing the cost required to add a braking function.

[0016] In still another illustrative embodiment of the servo driver, the control unit can control the switching unit according to the voltage signal so that: when the bus capacitor is fully charged, both ends of the pre-charge resistor are short-circuited, and the short circuit between any two phases of the AC output terminal of the inversion unit is removed. This is beneficial for further reducing the cost required to add a braking function.

[0017] In still another exemplary embodiment of the servo drive, the switching unit includes a pair of first contacts and a set of second contacts. The pair of first contacts are connected in parallel with a pre-charge resistor and then in series with a bus capacitor. The set of second contacts are connected to the AC output terminals of the inverter unit.

[0018] In still another exemplary embodiment of the servo drive, the switching unit includes a first relay and a second relay. The control unit is connected to the control terminals of the first relay and the second relay. The controlled terminal of the first relay includes a pair of first contacts. The controlled terminal of the second relay includes a set of second contacts.

[0019] In still another exemplary embodiment of the servo drive, the switching unit includes a third relay. The control unit is connected to the control terminal of the third relay. The controlled terminal of the third relay includes a pair of first contacts and a set of second contacts.

[0020] In still another exemplary embodiment of the servo drive, the control unit can control the inverter unit according to a voltage signal such that: during the pre-charging of the bus capacitor, when the voltage of the bus capacitor is less than a first voltage value, the inverter unit stops outputting; during the pre-charging of the bus capacitor, when the voltage of the bus capacitor is greater than the first voltage value, the inverter unit supplies power to the motor. This helps to further reduce the cost required to add a braking function.

[0021] In still another exemplary embodiment of the servo drive, the control unit can control the inverter unit according to a voltage signal such that: during the discharging of the bus capacitor after the main power supply is cut off, when the voltage of the bus capacitor is greater than a preset third voltage value, the inverter unit supplies power to the motor, where the third voltage value is less than or equal to the first voltage value and greater than a second voltage value; during the discharging of the bus capacitor after the main power supply is cut off, when the voltage of the bus capacitor is less than the third voltage value, the inverter unit switches to a free stop mode or a deceleration stop mode. This helps to improve the safety of stopping.

[0022] In still another exemplary embodiment of the servo drive, the control unit can control the inverter unit according to a voltage signal such that: when the bus capacitor is fully charged, the inverter unit supplies power to the motor.

[0023] The present invention also provides a servo motor, which includes a motor and the above-mentioned servo drive. The servo drive can synchronously control the switching of the short-circuit braking state and the switching of the charging mode of the pre-charge circuit by detecting the voltage of the bus capacitor. The servo drive helps to reduce the cost required to add a braking function. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The following drawings only schematically illustrate and explain the present invention and do not limit the scope of the present invention.

[0025] Figure 1 It is a flowchart of a schematic implementation of a control method for a servo motor.

[0026] Figure 2 It is a schematic diagram of a schematic implementation of a servo motor.

[0027] Figure 3 It is used to illustrate the time correspondence relationship between the voltage of the bus capacitor and the on / off states of a pair of first contacts and a pair of second contacts.

[0028] Figure 4 It is a schematic diagram of another schematic implementation of a servo motor.

[0029] Label description

[0030] 10 Rectifier unit

[0031] 20 DC bus

[0032] 30 Inverter unit

[0033] 40 Pre-charge circuit

[0034] 41 Bus capacitor

[0035] 42 Pre-charge resistor

[0036] 50 Switch unit

[0037] 51 First relay

[0038] 53 First contact

[0039] 52 Second relay

[0040] 54 Second contact

[0041] 55 Third relay

[0042] 60 Voltage detection unit

[0043] 70 Control unit

[0044] 100 Servo driver

[0045] 200 Motor Detailed implementation

[0046] For a clearer understanding of the technical features, objectives, and effects of the invention, the detailed implementation of the invention is now described with reference to the accompanying drawings. The same reference numerals in the figures denote components having the same or similar structures but the same functions.

[0047] In this text, "schematic" means "serving as an example, instance or illustration", and any illustration or implementation described as "schematic" in this text should not be construed as a more preferred or advantageous technical solution.

[0048] In this text, "first", "second", etc. do not indicate their importance level or order, etc., but are only used to indicate the difference from each other for the convenience of document description.

[0049] To simplify the drawings, only the parts related to the present invention are schematically shown in each figure, and they do not represent the actual structure of the product.

[0050] Figure 1 It is a flowchart of a schematic implementation of the control method for a servo motor. The servo motor includes a servo driver and a motor. The motor is, for example, a permanent magnet synchronous motor or a separately excited motor.

[0051] As Figure 2 shown, the servo driver 100 of the servo motor, for example, includes a rectification unit 10, a DC bus 20, an inversion unit 30, a pre-charge circuit 40 and a switch unit 50. The rectification unit 10 is used to connect to the AC main power supply and can convert alternating current into direct current. The DC bus 20 is connected to the DC output terminal of the rectification unit 10. The inversion unit 30 is connected to the DC bus 20 and can convert direct current into alternating current. The AC output terminal of the inversion unit 30 is connected to the motor 200. The pre-charge circuit 40 includes a bus capacitor 41 and a pre-charge resistor 42. The bus capacitor 41 and the pre-charge resistor 42 are connected in series between the positive and negative poles of the DC bus 20. The switch unit 50 includes a pair of first contacts 53 and a pair of second contacts 54. The pair of first contacts 53 is connected in parallel with the pre-charge resistor 42 and then in series with the bus capacitor 41. The pair of second contacts 54 are respectively connected to two phases of the AC output terminal of the inversion unit 30. When the pair of first contacts 53 is turned on, the two ends of the pre-charge resistor 42 are short-circuited. When the pair of second contacts 54 is turned on, a short circuit is established between the two phases of the AC output terminal of the inversion unit 30. The specific example of this servo driver is only used to assist in explaining the control method of this schematic implementation, and the control method of this schematic implementation is not limited to being implemented based on the specific example of this servo driver.

[0052] As Figure 1 shown, the control method includes the following steps S10 to step S30. Figure 3 It is used to illustrate the time correspondence relationship between the voltage of the bus capacitor, the on / off of the pair of first contacts, and the on / off of the pair of second contacts in the control method of this schematic implementation, where the abscissa is time t, Vt represents the change of the voltage of the bus capacitor with time, S 53 represents the on / off of the pair of first contacts 53, S 54Indicates the on / off state of a pair of second contacts 54. B indicates off, and C indicates on.

[0053] S10: During the pre-charging process of the bus capacitor 41, when the voltage of the bus capacitor 41 is less than a preset first voltage value V1, the short circuit across the pre-charging resistor 42 is removed (i.e., a pair of first contacts 53 are opened), so that the pre-charging circuit is in the low-voltage charging mode, and a short circuit is established between at least two phases of the AC output terminals of the inverter unit 30 (i.e., a pair of second contacts 54 are closed), making the short-circuit braking of the servo motor active. During the pre-charging process of the bus capacitor 41, when the voltage of the bus capacitor 41 is greater than the first voltage value V1, the two ends of the pre-charging resistor 42 are short-circuited (i.e., a pair of first contacts 53 are closed), so that the pre-charging circuit is in the high-voltage charging mode, and the short circuit between any two phases of the AC output terminals of the inverter unit 30 is removed (i.e., a pair of second contacts 54 are opened), making the short-circuit braking of the servo motor deactivated. Among them, the first voltage value V1 is set according to the needs of pre-charging, and it is generally about 90% of the DC bus voltage, but not limited to this.

[0054] Thereby, during the startup process of the servo motor, the activation and deactivation of the short-circuit braking can be associated with the switching of the charging mode of the pre-charging circuit, which is beneficial to reducing the cost required to add the braking function.

[0055] S20: When the bus capacitor 41 is fully charged, the two ends of the pre-charging resistor 42 are short-circuited (i.e., a pair of first contacts 53 are closed), and the short circuit between any two phases of the AC output terminals of the inverter unit 30 is removed (i.e., a pair of second contacts 54 are opened), and the servo motor is in the state of releasing the short-circuit braking. Thereby, during the normal operation process after the startup of the servo motor is completed, the release of the short-circuit braking can be associated with the state of the bus capacitor being fully charged, which is beneficial to further reducing the cost required to add the braking function.

[0056] S30: During the discharging process of the bus capacitor 41 after the main power supply is cut off, when the voltage of the bus capacitor 41 is greater than a preset second voltage value V2, short-circuit both ends of the pre-charge resistor 42 (i.e., a pair of first contacts 53 are turned on), so that the pre-charge circuit is in the high-voltage charging mode, and remove the short-circuit between any two phases of the AC output terminals of the inverter unit 30 (i.e., a pair of second contacts 54 are turned off), so that the short-circuit braking of the servo motor is in the released state. During the discharging process of the bus capacitor 41 after the main power supply is cut off, when the voltage of the bus capacitor 41 is less than the second voltage value V2, remove the short-circuit between both ends of the pre-charge resistor 42 (i.e., a pair of first contacts 53 are turned off), so that the pre-charge circuit is in the low-voltage charging mode, and establish a short-circuit between at least two phases of the AC output terminals of the inverter unit 30 (i.e., a pair of second contacts 54 are turned on), so that the short-circuit braking of the servo motor is in the activated state. Among them, the second voltage value V2 is set according to the needs of braking, and it should be less than the first voltage value V1. Thus, during the shutdown process of the servo motor, the activation and release of the short-circuit braking can be associated with the switching of the charging mode of the pre-charge circuit, which is beneficial to further reducing the cost required to add the braking function.

[0057] In the illustrative embodiment, step S10 further includes: during the pre-charging process of the bus capacitor 41, when the voltage of the bus capacitor 41 is less than the first voltage value V1, control the inverter unit 30 to stop outputting; during the pre-charging process of the bus capacitor 41, when the voltage of the bus capacitor 41 is greater than the first voltage value V1, control the inverter unit 30 to supply power to the motor 200. Thus, during the startup process of the servo motor, the switching of the state of the inverter unit can be associated with the switching of the charging mode of the pre-charge circuit, which is beneficial to further reducing the cost required to add the braking function.

[0058] In the illustrative embodiment, step S30 further includes: during the discharging process of the bus capacitor 41 after the main power supply is cut off, when the voltage of the bus capacitor 41 is greater than a preset third voltage value V3, control the inverter unit 30 to supply power to the motor 200; during the discharging process of the bus capacitor 41 after the main power supply is cut off, when the voltage of the bus capacitor 41 is less than the third voltage value V3, control the inverter unit 30 to switch to the free-stop mode or the deceleration-stop mode. Among them, the third voltage value V3 is set according to the needs, and it should be less than or equal to the first voltage value V1 and greater than the second voltage value V2. During the process of the voltage of the bus capacitor 41 dropping from the third voltage value V3 to the second voltage value V2, the motor 200 gradually decelerates in the free-stop mode or the deceleration-stop mode, and then performs short-circuit braking when the voltage of the bus capacitor 41 drops to the second voltage value V2. This is beneficial to improving the safety of parking. The difference between the third voltage value V3 and the second voltage value V2 is, for example, 10V to 20V.

[0059] In a schematic embodiment, step S20 further includes: when the bus capacitor 41 is fully charged, controlling the inverter unit 30 to supply power to the motor.

[0060] The present invention also provides a servo driver for implementing the above-mentioned control method of the servo motor. The servo driver is used to drive a motor, where the motor is, for example, a permanent magnet synchronous motor or a separately excited motor. Figure 2 A schematic embodiment of the servo driver is shown. As Figure 2 shown, the servo driver 100 includes a rectifier unit 10, a DC bus 20, an inverter unit 30, a pre-charge circuit 40, a switch unit 50, a voltage detection unit 60, and a control unit 70.

[0061] As Figure 2 shown, the rectifier unit 10 is used to connect to the AC main power supply and can convert alternating current into direct current. The DC bus 20 is connected to the DC output terminal of the rectifier unit 10. The inverter unit 30 is connected to the DC bus 20 and can convert direct current into alternating current. The AC output terminal of the inverter unit 30 is used to connect to the motor 200.

[0062] The pre-charge circuit 40 includes a bus capacitor 41 and a pre-charge resistor 42. The bus capacitor 41 and the pre-charge resistor 42 are connected in series between the positive and negative poles of the DC bus 20.

[0063] The switch unit 50 is connected to the pre-charge circuit 40 to be able to short-circuit both ends of the pre-charge resistor 42. The switch unit 50 is connected to at least two phases of the AC output terminal of the inverter unit 30 to be able to establish a short circuit between at least two phases of the AC output terminal of the inverter unit 30. Specifically, in this schematic embodiment, the switch unit 50 includes a third relay 55. The controlled end of the third relay 55 includes a pair of first contacts 53 and a pair of second contacts 54. A pair of first contacts 53 is connected in parallel with the pre-charge resistor 42 and then connected in series with the bus capacitor 41. A pair of second contacts 54 are respectively connected to two phases of the AC output terminal of the inverter unit 30. When a pair of first contacts 53 conducts, both ends of the pre-charge resistor 42 are short-circuited. When a pair of second contacts 54 conducts, a short circuit is established between two phases of the AC output terminal of the inverter unit 30.

[0064] The voltage detection unit 60 can detect the voltage of the bus capacitor 41 and generate a voltage signal. The control unit 70 is connected to the control terminal of the third relay 55. The control unit 70 can control the switch unit 50 according to the voltage signal, so that: during the pre-charging process of the bus capacitor 41, when the voltage of the bus capacitor 41 is less than a preset first voltage value V1, the short circuit across the pre-charge resistor 42 is released (i.e., a pair of first contacts 53 are disconnected), the pre-charge circuit is in the low-voltage charging mode, and a short circuit is established between at least two phases of the AC output terminal of the inverter unit 30 (i.e., a pair of second contacts 54 are conducted), so that the short-circuit braking of the servo motor is in the active state; during the pre-charging process of the bus capacitor 41, when the voltage of the bus capacitor 41 is greater than the first voltage value V1, the pre-charge resistor 42 is short-circuited (i.e., a pair of first contacts 53 are conducted), the pre-charge circuit is in the high-voltage charging mode, and the short circuit between any two phases of the AC output terminal of the inverter unit 30 is released (i.e., a pair of second contacts 54 are disconnected), so that the short-circuit braking of the servo motor is in the released state. Among them, the first voltage value V1 is set according to the need of pre-charging, and it is generally about 90% of the DC bus voltage, but not limited to this.

[0065] For this servo driver, by detecting the voltage of the bus capacitor, the switching of the state of the short-circuit braking and the switching of the charging mode of the pre-charge circuit can be synchronously controlled. This servo driver is beneficial to reducing the cost required to add the braking function.

[0066] In the illustrative embodiment, the control unit 70 can control the switch unit 50 according to the voltage signal, so that: during the discharging process of the bus capacitor 41 after the main power supply is powered off, when the voltage of the bus capacitor 41 is greater than a preset second voltage value V2, the pre-charge resistor 42 is short-circuited (i.e., a pair of first contacts 53 are conducted), the pre-charge circuit is in the high-voltage charging mode, and the short circuit between any two phases of the AC output terminal of the inverter unit 30 is released (i.e., a pair of second contacts 54 are disconnected), so that the short-circuit braking of the servo motor is in the released state; during the discharging process of the bus capacitor 41 after the main power supply is powered off, when the voltage of the bus capacitor 41 is less than the second voltage value V2, the short circuit across the pre-charge resistor 42 is released (i.e., a pair of first contacts 53 are disconnected), the pre-charge circuit is in the low-voltage charging mode, and a short circuit is established between at least two phases of the AC output terminal of the inverter unit 30 (i.e., a pair of second contacts 54 are conducted), so that the short-circuit braking of the servo motor is in the active state. Among them, the second voltage value V2 is set according to the need of braking, and it should be less than the first voltage value V1. Thereby, during the shutdown process of the servo motor, the activation and release of the short-circuit braking can be associated with the switching of the charging mode of the pre-charge circuit, which is beneficial to further reducing the cost required to add the braking function.

[0067] In a schematic embodiment, the control unit 70 can control the switch unit 50 according to a voltage signal such that: when the bus capacitor 41 is fully charged, the two ends of the pre-charge resistor 42 are short-circuited (i.e., a pair of first contacts 53 are turned on), and the short circuit between any two phases of the AC output terminal of the inverter unit 30 is released (i.e., a pair of second contacts 54 are turned off), and the servo motor is in a state of releasing the short-circuit braking. Thereby, during the normal operation after the servo motor starts, the release of the short-circuit braking can be associated with the state that the bus capacitor is fully charged, which is beneficial to further reducing the cost required to add the braking function.

[0068] In a schematic embodiment, the control unit 70 can control the inverter unit 30 according to a voltage signal such that: during the pre-charging process of the bus capacitor 41, when the voltage of the bus capacitor 41 is less than the first voltage value V1, the inverter unit 30 stops outputting; during the pre-charging process of the bus capacitor 41, when the voltage of the bus capacitor 41 is greater than the first voltage value V1, the inverter unit 30 supplies power to the motor 200. Thereby, during the starting process of the servo motor, the switching of the state of the inverter unit can be associated with the switching of the charging mode of the pre-charge circuit, which is beneficial to further reducing the cost required to add the braking function.

[0069] In a schematic embodiment, the control unit 70 can control the inverter unit 30 according to a voltage signal such that: during the discharging process of the bus capacitor 41 after the main power supply is powered off, when the voltage of the bus capacitor 41 is greater than a preset third voltage value V3, the inverter unit 30 supplies power to the motor 200; during the discharging process of the bus capacitor 41 after the main power supply is powered off, when the voltage of the bus capacitor 41 is less than the third voltage value V3, the inverter unit 30 switches to the free-stop mode or the deceleration-stop mode. Among them, the third voltage value V3 is set according to needs, and it should be less than or equal to the first voltage value V1 and greater than the second voltage value V2. During the process that the voltage of the bus capacitor 41 drops from the third voltage value V3 to the second voltage value V2, the motor 200 gradually decelerates in the free-stop mode or the deceleration-stop mode, and then performs short-circuit braking when the voltage of the bus capacitor 41 drops to the second voltage value V2. This is beneficial to improving the safety of parking. The difference between the third voltage value V3 and the second voltage value V2 is, for example, 10V to 20V.

[0070] In a schematic embodiment, the control unit 70 can control the inverter unit 30 according to a voltage signal such that: when the bus capacitor 41 is fully charged, the inverter unit 30 supplies power to the motor 200.

[0071] Figure 4 Shows another schematic embodiment of the servo drive. The servo drive of this schematic embodiment is the same as Figure 2The same or similar parts of the servo driver shown are not described herein again. The differences are as follows. In this illustrative embodiment, the third relay 55 of the switch unit 50 is replaced by a first relay 51 and a second relay 52. The control unit 70 is connected to the control terminals of the first relay 51 and the second relay 52. The controlled terminal of the first relay 51 includes a pair of first contacts 53, and the controlled terminal of the second relay 52 includes two pairs of second contacts 54. A pair of first contacts 53 is connected in parallel with the pre-charge resistor 42 and then in series with the bus capacitor 41. The two pairs of second contacts 54 are connected to the AC output terminals of the inverter unit 30. By conducting the two pairs of second contacts 54 (i.e., Figure 4 the pair of second contacts 54 on the upper side is conducted, and the pair of second contacts 54 on the lower side is conducted), a short circuit can be established between the three phases of the AC output terminals of the inverter unit 30. The timing of conduction and disconnection of a pair of first contacts 53 in this illustrative embodiment is the same as that of Figure 2 the pair of first contacts 53 described in the servo driver shown. The timing of conduction and disconnection of each pair of second contacts 54 in this illustrative embodiment is the same as that of Figure 2 the pair of second contacts 54 described in the servo driver shown.

[0072] For this servo driver, by detecting the voltage of the bus capacitor, the switching of the short-circuit braking state and the charging mode of the pre-charge circuit can be synchronously controlled. This servo driver is beneficial to reducing the cost required to add a braking function.

[0073] The present invention also provides a servo motor. In one of its illustrative embodiments, the servo motor includes a motor 200 and a Figure 2 or Figure 4 the servo driver 100 shown. The motor 200 is, for example, a permanent magnet synchronous motor or a separately excited motor. This servo motor is beneficial to reducing the cost required to add a braking function.

[0074] In the above, the deceleration stop mode means that: the inverter unit gradually reduces the output frequency according to the set deceleration time, and stops after the frequency drops to 0 Hz. The free stop mode means that: the inverter unit terminates the output, and the motor stops freely according to the mechanical inertia.

[0075] It should be understood that although this specification is described according to each embodiment, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0076] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent implementation or change made without departing from the technical spirit of the present invention, such as the combination, division, or repetition of features, shall be included within the protection scope of the present invention.

Claims

1. A control method for a servo motor, the servo motor comprising a servo driver and a motor, the servo driver comprising a rectifying unit, a DC bus, an inverting unit, a bus capacitor and a pre-charge resistor, the rectifying unit being connected to an AC main power supply and converting AC power into DC power, the DC bus being connected to the DC power output terminal of the rectifying unit, the inverting unit being connected to the DC bus and converting DC power into AC power, the motor being connected to the AC power output terminal of the inverting unit, the bus capacitor and the pre-charge resistor being connected in series between the positive and negative poles of the DC bus, and both ends of the pre-charge resistor being short-circuited through a circuit. Characterized in that, The control method comprises: During the pre-charging of the bus capacitor, when the voltage of the bus capacitor is less than a preset first voltage value, the short circuit at both ends of the pre-charge resistor is released, and a short circuit is established between at least two phases of the AC power output terminal of the inverting unit; and During the pre-charging of the bus capacitor, when the voltage of the bus capacitor is greater than the first voltage value, both ends of the pre-charge resistor are short-circuited, and the short circuit between any two phases of the AC power output terminal of the inverting unit is released.

2. The control method for a servo motor according to claim 1, Characterized in that, The control method further comprises: During the discharging of the bus capacitor after the main power supply is powered off, when the voltage of the bus capacitor is greater than a preset second voltage value, both ends of the pre-charge resistor are short-circuited, and the short circuit between any two phases of the AC power output terminal of the inverting unit is released, the second voltage value being less than the first voltage value; and During the discharging of the bus capacitor after the main power supply is powered off, when the voltage of the bus capacitor is less than the second voltage value, the short circuit at both ends of the pre-charge resistor is released, and a short circuit is established between at least two phases of the AC power output terminal of the inverting unit.

3. The control method for a servo motor according to claim 1, Characterized in that, The control method further comprises: when the bus capacitor is fully charged, both ends of the pre-charge resistor are short-circuited, and the short circuit between any two phases of the AC power output terminal of the inverting unit is released.

4. The control method for a servo motor according to claim 1, Characterized in that, The control method further comprises: During the pre-charging of the bus capacitor, when the voltage of the bus capacitor is less than the first voltage value, controlling the inverting unit to stop output; and During the pre-charging of the bus capacitor, when the voltage of the bus capacitor is greater than the first voltage value, controlling the inverting unit to supply power to the motor.

5. The control method for a servo motor according to claim 2, Characterized in that, The control method further comprises: During the discharging of the bus capacitor after the main power supply is powered off, when the voltage of the bus capacitor is greater than a preset third voltage value, controlling the inverting unit to supply power to the motor, wherein the third voltage value is less than or equal to the first voltage value and greater than the second voltage value; and During the discharging of the bus capacitor after the main power supply is powered off, when the voltage of the bus capacitor is less than the third voltage value, controlling the inverting unit to switch to a free parking mode or a decelerating parking mode.

6. The control method for a servo motor according to claim 1, Characterized in that, The control method further includes: controlling the inverter unit to supply power to the motor when the bus capacitor is fully charged.

7. A servo driver for driving a motor (200), characterized in that the servo driver includes: a rectifier unit (10) for connecting to an AC main power supply and capable of converting alternating current into direct current; a DC bus (20) connected to the DC output terminal of the rectifier unit (10); an inverter unit (30) connected to the DC bus (20) and capable of converting direct current into alternating current, and the AC output terminal of the inverter unit (30) is used to connect to the motor (200); a pre-charge circuit (40) including a bus capacitor (41) and a pre-charge resistor (42), and the bus capacitor (41) and the pre-charge resistor (42) are connected in series between the positive and negative poles of the DC bus (20); a switch unit (50) connected to the pre-charge circuit (40) to be able to short-circuit both ends of the pre-charge resistor (42), and the switch unit (50) is connected to at least two phases of the AC output terminal of the inverter unit (30) to be able to establish a short circuit between at least two phases of the AC output terminal of the inverter unit (30); a voltage detection unit (60) capable of detecting the voltage of the bus capacitor (41) and generating a voltage signal; and a control unit (70) capable of controlling the switch unit (50) according to the voltage signal, so that: during the pre-charging process of the bus capacitor (41), when the voltage of the bus capacitor (41) is less than a preset first voltage value, the short circuit at both ends of the pre-charge resistor (42) is released, and a short circuit is established between at least two phases of the AC output terminal of the inverter unit (30); during the pre-charging process of the bus capacitor (41), when the voltage of the bus capacitor (41) is greater than the first voltage value, both ends of the pre-charge resistor (42) are short-circuited, and the short circuit between any two phases of the AC output terminal of the inverter unit (30) is released.

8. The servo driver according to claim 7, characterized in that the control unit (70) is capable of controlling the switch unit (50) according to the voltage signal, so that: during the discharging process of the bus capacitor (41) after the main power supply is powered off, when the voltage of the bus capacitor (41) is greater than a preset second voltage value, both ends of the pre-charge resistor (42) are short-circuited, and the short circuit between any two phases of the AC output terminal of the inverter unit (30) is released, and the second voltage value is less than the first voltage value; during the discharging process of the bus capacitor (41) after the main power supply is powered off, when the voltage of the bus capacitor (41) is less than the second voltage value, the short circuit at both ends of the pre-charge resistor (42) is released, and a short circuit is established between at least two phases of the AC output terminal of the inverter unit (30).

9. The servo driver according to claim 7, characterized in that The control unit (70) can control the switching unit (50) according to the voltage signal such that: when the bus capacitor (41) is fully charged, the two ends of the pre-charge resistor (42) are short-circuited, and the short circuit between any two phases of the AC output terminals of the inverter unit (30) is released.

10. The servo driver according to claim 7, characterized in that the switching unit (50) includes a pair of first contacts (53) and a set of second contacts (54). The pair of first contacts (53) is connected in parallel with the pre-charge resistor (42) and then connected in series with the bus capacitor (41), and the set of second contacts (54) is connected to the AC output terminals of the inverter unit (30).

11. The servo driver according to claim 10, characterized in that the switching unit (50) includes a first relay (51) and a second relay (52). The control unit (70) is connected to the control terminals of the first relay (51) and the second relay (52). The controlled terminals of the first relay (51) include the pair of first contacts (53), and the controlled terminals of the second relay (52) include the set of second contacts (54); or the switching unit (50) includes a third relay (55). The control unit (70) is connected to the control terminal of the third relay (55), and the controlled terminals of the third relay (55) include the pair of first contacts (53) and the set of second contacts (54).

12. The servo driver according to claim 7, characterized in that the control unit (70) can control the inverter unit (30) according to the voltage signal such that: during the pre-charging process of the bus capacitor (41), when the voltage of the bus capacitor (41) is less than the first voltage value, the inverter unit (30) stops outputting; during the pre-charging process of the bus capacitor (41), when the voltage of the bus capacitor (41) is greater than the first voltage value, the inverter unit (30) supplies power to the motor (200).

13. The servo driver according to claim 8, characterized in that the control unit (70) can control the inverter unit (30) according to the voltage signal such that: during the discharging process of the bus capacitor (41) after the main power supply is cut off, when the voltage of the bus capacitor (41) is greater than a preset third voltage value, the inverter unit (30) supplies power to the motor (200), where the third voltage value is less than or equal to the first voltage value and greater than the second voltage value; during the discharging process of the bus capacitor (41) after the main power supply is cut off, when the voltage of the bus capacitor (41) is less than the third voltage value, the inverter unit (30) switches to the free parking mode or the decelerating parking mode.

14. The servo driver according to claim 7, characterized in that The control unit (70) can control the inverter unit (30) according to the voltage signal such that: when the bus capacitor (41) is fully charged, the inverter unit (30) supplies power to the motor (200).

15. A servo motor, characterized in that it includes a motor (200) and a servo driver as described in claim 7.

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