WO2024065783A1

WO2024065783A1 - Servo motor, control method for same, and servo driver

Info

Publication number: WO2024065783A1
Application number: PCT/CN2022/123522
Authority: WO
Inventors: Jun Ping Zhang
Original assignee: Siemens Aktiengesellschaft; Siemens Ltd., China
Priority date: 2022-09-30
Filing date: 2022-09-30
Publication date: 2024-04-04

Abstract

A control method for a servo motor includes: in a process of pre-charging the bus capacitor, in a case that a voltage of the bus capacitor is less than a predetermined first voltage value, releasing the short circuit between the two terminals of the pre-charge resistor, and establishing a short circuit between at least two phases of the AC power output terminal of the inverter unit; and in the process of pre-charging the bus capacitor, in a case that the voltage of the bus capacitor is greater than the predetermined first voltage value, short-circuiting the two terminals of the pre-charge resistor, and releasing a short circuit between any two phases of the AC power output terminal of the inverter unit. The control method is conducive to lowering costs in additionally configuring a braking function. A servo driver and a servo motor are also disclosed.

Description

SERVO MOTOR, CONTROL METHOD FOR SAME, AND SERVO DRIVER

TECHNICAL FIELD

The present disclosure relates to the technical field of motor driving, and in particular, relates to a control method for a servo motor. The present disclosure further relates to a servo driver using the control method, and a servo motor including the servo driver.

BACKGROUND

In application of a servo driver, in order that a motor is capable of stopping quickly in case of power off of a mains power source, generally, a braking function is configured in the servo driver. At present, costs in software development and hardware for additionally configuring the braking function are high.

SUMMARY

An object of the present disclosure is to provide a control method for a servo motor, which is conducive to lowering costs in additional configuring a braking function.

Another object of the present disclosure is to provide a servo driver, which is conducive to lowering costs in additional configuring a braking function.

Various embodiments of the present disclosure provide a control method for a servo motor. The servo motor includes a servo driver and a motor. The servo driver includes a rectifier unit, a DC bus, an inverter unit, a bus capacitor, and a pre-charge resistor. The rectifier unit is connected to an AC mains power source and capable of converting an AC power to a DC power. The DC bus is connected to a DC power output terminal of the rectifier unit. The inverter unit being connected to the DC bus and capable of converting a DC power to an AC power. The motor is connected to an AC power output terminal of the inverter unit. The bus capacitor and the pre-charge resistor are connected in series and subsequently connected between positive and negative terminals of the DC bus. Two terminals of the pre-charge resistor are short-circuited by a circuit. The control method includes: in a process of pre-charging the bus capacitor, in a case that a voltage of the bus capacitor is less than a predetermined first voltage value, releasing the short circuit between the two terminals of the pre-charge resistor, and establishing a short circuit between at least two phases of the AC power output terminal of the inverter unit; and in the process of pre-charging the bus capacitor, in a case that the voltage of the bus capacitor is greater than the predetermined first voltage value, short-circuiting the two terminals of the pre-charge resistor, and releasing a short circuit between any two phases of the AC power output terminal of the inverter unit.

In the control method for the servo motor, in startup of the servo motor, activation and deactivation of short circuit braking are associated with switching of charge modes of a pre-charge circuit, which is conducive to lowering costs in additional configuring a brake function.

In some exemplary embodiments of the control method for the servo motor, the control method further includes: in a process of discharging the bus capacitor upon power off of the AC mains power source, in a case that the voltage of the bus capacitor is greater than a predetermined second voltage value, short-circuiting the two terminals of the pre-charge resistor, and releasing the short circuit between the any two phases of the AC power output terminal of the inverter unit, wherein the predetermined second voltage value is less than the predetermined first voltage value; and in the process of discharging the bus capacitor upon power off of the AC mains power source, in a case that the voltage of the bus capacitor is less than the predetermined second voltage value, releasing the short circuit between the two terminals of the pre-charge resistor, and establishing the short circuit between the at least two phases of the AC power output terminal of the inverter unit. In this way, costs in additionally configuring a braking function are further lowered.

In some exemplary embodiments of the control method for the servo motor, the control method further includes: in a case that the bus capacitor is fully charged, short-circuiting the two terminals of the pre-charge resistor, and releasing the short circuit between the any two phases of the AC power output terminal of the inverter unit. In this way, costs in additionally configuring a braking function are further lowered.

In some exemplary embodiments of the control method for the servo motor, the control method further includes: in the process of pre-charging the bus capacitor, in the case that the voltage of the bus capacitor is less than the predetermined first voltage value, controlling the inverter unit to stop outputting power; and in the process of pre-charging the bus capacitor, in the case that the voltage of the bus capacitor is greater than the predetermined first voltage value, controlling the inverter unit to supply power to the motor. In this way, costs in additionally configuring a braking function are further lowered.

In some exemplary embodiments of the control method for the servo motor, the control method further includes: in the process of discharging the bus capacitor upon power off of the AC mains power source, in a case that the voltage of the bus capacitor is greater than a predetermined third voltage value, controlling the inverter unit to supply power to the motor, wherein the predetermined third voltage value is less than or equal to the predetermined first voltage value and greater than the predetermined second voltage value; and in the process of discharging the bus capacitor upon power off of the AC mains power source, in a case that the voltage of the bus capacitor is less than the predetermined third voltage value, controlling the inverter unit to switch to a free stop mode or a deceleration stop mode. In this way, safety in stopping cars is enhanced.

In some exemplary embodiments of the control method for the servo motor, the control method further includes: in a case that the bus capacitor is fully charged, controlling the inverter unit to supply power to the motor.

Various embodiments of the present disclosure provide a servo driver configured to drive a motor. The servo driver includes a rectifier unit, a DC bus, an inverter unit, a pre-charge circuit, a switch unit, a voltage detection unit, and a control unit. The rectifier unit is configured to be connected to an AC mains power source and capable of converting an AC power to a DC power. The DC bus is connected to a DC power output terminal of the rectifier unit. The inverter unit is connected to the DC bus and capable of converting an DC power to an AC power. An AC power output terminal of the inverter unit is connected 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 and subsequently connected between positive and negative terminals of the DC bus. The switch unit is connected to the pre-charge circuit to be capable of short-circuiting two terminals of the pre-charge resistor. The switch unit is connected to at least two phases of the AC power output terminal of the inverter unit to be capable of establishing a short circuit between the at least two phases of the AC power output terminal of the inverter unit. The voltage detection unit is capable of detecting a voltage of the bus capacitor and generating a voltage signal. The control unit is capable of controlling the switch unit based on the voltage signal, such that: in a process of pre-charging the bus capacitor, in a case that the voltage of the bus capacitor is less than a predetermined first voltage value, the short circuit between the two terminals of the pre-charge resistor is released, and the short circuit is established between the at least two phases of the AC power output terminal of the inverter unit; and in the process of pre-charging the bus capacitor, in the case that the voltage of the bus capacitor is greater than the predetermined first voltage value, the two terminals of the pre-charge resistor are short-circuited, and a short circuit between any two phases of the AC power output terminal of the inverter unit is released.

The servo driver, by detecting the voltage of the bus capacitor, is capable of synchronously controlling state switching of short circuit braking, and switching of the charge modes of the pre-charge circuit. The servo driver is conducive to lowering costs in additionally configuring a braking function.

In some exemplary embodiments of the servo driver, the control unit is capable of controlling the switch unit based on the voltage signal, such that: in a process of discharging the bus capacitor upon power off of the AC mains power source, in a case that the voltage of the bus capacitor is greater than a predetermined second voltage value, the two terminals of the pre-charge resistor are short-circuited, and the short circuit between the at any two phases of the AC power output terminal of the inverter unit is released, wherein the predetermined second voltage value is less than the predetermined first voltage value; and in the process of discharging the bus capacitor upon power off of the AC mains power source, in a case that the voltage of the bus capacitor is less than the predetermined second voltage value, the short circuit between the two terminals of the pre-charge resistor is released, and the short circuit is established between the at least two phases of the AC power output terminal of the inverter unit. In this way, costs in additionally configuring a braking function are further lowered.

In some exemplary embodiments of the servo driver, the control unit is capable of controlling the switch unit based on the voltage signal, such that: in a case that the bus capacitor is fully charged, the two terminals of the pre-charge resistor are short-circuited, and the short circuit between the any two phases of the AC power output terminal of the inverter unit is released. In this way, costs in additionally configuring a braking function are further lowered.

In some exemplary embodiments of the servo driver, the switch unit includes a pair of contacts and a group of second contacts. The pair of contacts is connected in parallel to the pre-charge resistor and subsequently connected in parallel to the bus capacitor. The group of second contacts is connected to the AC power output terminal of the inverter unit.

In some exemplary embodiments of the servo driver, the switch unit includes a first relay and a second relay. The control unit is connected to a control terminal of the first relay and a control terminal of the second relay. A controlled terminal of the first relay includes the pair of first contacts. A controlled terminal of the second relay includes the group of second contacts.

In some exemplary embodiments of the servo driver, the switch unit includes a third relay. The control unit is connected to a control terminal of the third relay. A controlled terminal of the third relay includes the pair of first contacts and the group of second contacts.

In some exemplary embodiments of the servo driver, the control unit is capable of controlling the inverter unit based on the voltage signal, such that: in the process of pre-charging the bus capacitor, in the case that the voltage of the bus capacitor is less than a predetermined first voltage value, the inverter unit stops outputting power; and in the process of pre-charging the bus capacitor, in the case that the voltage of the bus capacitor is greater than the predetermined first voltage value, the inverter unit supplies power to the motor. In this way, costs in additionally configuring a braking function are further lowered.

In some exemplary embodiments of the servo driver, the control unit is capable of controlling the inverter unit based on the voltage signal, such that: in the process of discharging the bus capacitor upon power off of the AC mains power source, in a case that the voltage of the bus capacitor is greater than a predetermined third voltage value, the inverter unit supplies power to the motor, wherein the predetermined third voltage value is less than or equal to the predetermined first voltage value and greater than the predetermined second voltage value; and in the process of discharging the bus capacitor upon power off of the AC mains power source, in a case that the voltage of the bus capacitor is less than the predetermined third voltage value, the inverter unit switches to a free stop mode or a deceleration stop mode In this way, safety in stopping cars is enhanced.

In some exemplary embodiments of the servo driver, the control unit is capable of controlling the inverter unit based on the voltage signal, such that: in a case that the bus capacitor is fully charged, the inverter unit supplies power to the motor.

Various embodiments of the present disclosure provide a servo motor. The servo motor includes a motor and a servo motor as described above. The servo driver, by detecting the voltage of the bus capacitor, is capable of synchronously controlling state switching of short circuit braking, and switching of the charge modes of the pre-charge circuit. The servo driver is conducive to lowering costs in additionally configuring a braking function.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are merely for schematic and illustrative description and demonstration of the present disclosure, instead of limiting the scope of the present disclosure.

FIG. 1 is a flowchart of a control method for a servo motor according to an exemplary embodiment of the present disclosure;

FIG. 2 is a schematic structural diagram of a servo motor according to an exemplary embodiment of the present disclosure;

FIG. 3 illustrates a time correspondence relationship between a voltage of a bus capacitor and connection and disconnection of a pair of first contacts and connection and disconnection of a pair of second contacts; and

FIG. 4 is a schematic diagram of a servo motor according to an exemplary embodiment of the present disclosure.

Reference numerals and denotations thereof:

10–Rectifier unit

20–DC bus

30–Inverter unit

40–Pre-charge circuit

41–Bus capacitor

42–Pre-charge resistor

50–Switch unit

51–First relay

53–First contact

52–Second relay

54–Second contact

55–Third relay

60–Voltage detection unit

70–Control unit

100–Servo driver

200–Motor

DETAILED DESCRIPTION

For clearer descriptions of the technical features, objects, and the technical effects of the present disclosure, the specific embodiments of the present disclosure are hereinafter described with reference to the accompanying drawings. In the drawings, like reference numerals denote elements having the same structure or having the similar structure but the same function.

In this specification, the term "exemplary" or "schematic" is used herein to mean "serving as an example, instance, or illustration, " and any illustration or embodiment described herein as "exemplary" shall not be necessarily construed as preferred or advantageous over other illustrations or embodiments.

In this text, the terms "first, " "second, " and the like do not represent degrees of importance or a sequence, but only for differentiation, and for ease of description.

For brevity, parts relevant to the present disclosure are merely illustrated in the drawings, and these parts do not denote the actual structure of the product.

FIG. 1 is a flowchart of a control method for a servo motor according to an exemplary embodiment of the present disclosure; 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.

As illustrated in FIG. 2, a servo driver 100 of the servo motor, for example, includes a rectifier unit 10, a DC bus 20, an inverter unit 30, a pre-charge circuit 40, and a switch unit 50. The rectifier unit 10 is configured to be connected to an AC mains power source and capable of converting an AC power to a DC power. The DC bus 20 is connected to a DC power output terminal of the rectifier unit 10. The inverter unit 30 is connected to the DC bus 20 and capable of converting an DC power to an AC power. An AC power output terminal of the inverter unit 30 is connected to a 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 and subsequently connected between positive and negative terminals 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 contacts 53 is connected in parallel to the pre-charge resistor 42 and subsequently connected in parallel to the bus capacitor 41. The group of second contacts 54 is connected to two phases of the AC power output terminal of the inverter unit 30. The pair of first contacts 53 is conducted, and then two terminals of the pre-charge resistor 42 are short-circuited. The pair of second contacts 54 is conducted, and then a short circuit is established between two phases of the AC power output terminal of the inverter unit 30. A specific example of the servo driver is given merely for illustrating the control method according to this exemplary embodiment. However, the control method according to this exemplary embodiment is not limited to implementation based on this specific example.

As illustrated in FIG. 1, the control method includes the following steps S10 to S30. FIG. 3 illustrates a time correspondence relationship between a voltage of a bus capacitor and connection and disconnection of a pair of first contacts and connection and disconnection of a pair of second contacts according to an exemplary embodiment of the present disclosure. As illustrated in FIG. 3, an abscissa represents time t, Vt represents a variation of the voltage of the bus capacitor with time, S ₅₃ represents connection and disconnection of a pair of first contacts 53, S ₅₄ represents connection and disconnection of a pair of second contacts 54, B represents disconnection, and C represents connection.

In S10, in a process of pre-charging the bus capacitor 41, in a case that a voltage of the bus capacitor 41 is less than a predetermined first voltage value V1, the short circuit between the two terminals of the pre-charge resistor 42 is released (that is, the pair of first contacts 53 is disconnected) such that the pre-charge resistor is in a low-voltage charge mode, and the short circuit is established between at least two phases of the AC power output terminal of the inverter unit 30 (that is, the pair of second contacts 54 is connected) such that short circuit braking of the servo motor is in an activated state. In the process of pre-charging the bus capacitor 41, in a case that a voltage of the bus capacitor 41 is greater than the predetermined first voltage value V1, the two terminals of the pre-charge resistor 42 are short-circuited (that is, the pair of first contacts 53 is connected) such that the pre-charge circuit is in a high-voltage charge mode, and the short circuit between at least two phases of the AC power output terminal of the inverter unit 30 is released (that is, the pair of second contacts 54 is disconnected) such that short circuit braking of the servo motor is in a deactivated state. The first voltage value V1 needs to be defined according to the needs of pre-charging, which is generally 90%of the voltage of the DC bus, but is not limited to this value.

In this way, in startup of the servo motor, activation and deactivation of short circuit braking are associated with switching of charge modes of the pre-charge circuit, which is conducive to lowering costs in additionally configuring a braking function.

In S20, in a case that the bus capacitor 41 is fully charged, the two terminals of the pre-charge resistor 42 are short-circuited (that is, the pair of first contacts 53 is connected) , and a short circuit between any two phases of the AC power output terminal of the inverter unit 30 is released (that is, the pair of second contacts 54 is disconnected) such that short circuit braking of the servo motor is in the deactivated state. In this way, in normal operation of the servo motor upon completion of startup, deactivation of short circuit braking is associated with a state where the bus capacitor is fully charged, which is conducive to further lowering costs in additionally configuring a braking function.

In S30, in a process of discharging the bus capacitor 41 upon power off of the AC mains power source, in a case that the voltage of the bus capacitor 41 is greater than a predetermined second voltage value V2, the two terminals of the pre-charge resistor 42 are short-circuited (that is, the pair of first contacts 53 is connected) such that the pre-charge circuit is in the high-voltage charge mode, and the short circuit between the any two phases of the AC power output terminal of the inverter unit 30 is released (that is, the pair of second contacts 54 is disconnected) such that short circuit braking of the servo motor is in the deactivated state. In the process of pre-charging the bus capacitor 41, in a case that the voltage of the bus capacitor 41 is less than the predetermined second voltage value V2, the short circuit between the two terminals of the pre-charge resistor 42 is released (that is, the pair of first contacts 53 is disconnected) such that the pre-charge circuit is in the low-voltage charge mode, and the short circuit is established between the at least two phases of the AC power output terminal of the inverter unit 30 (that is, the pair of second contacts 54 is connected) such that short circuit braking of the servo motor is in the activated state. The second voltage value V2 needs to be defined according to the need of braking, which should be less than the first voltage value V1. In this way, in shutdown of the servo motor, activation and deactivation of short circuit braking are associated with switching of charge modes of a pre-charge circuit, which is conducive to further lowering costs in additionally configuring a braking function.

In some exemplary embodiments, step S10 further includes: in the process of pre-charging the bus capacitor 41, in the case that the voltage of the bus capacitor 41 is less than the predetermined first voltage value V1, controlling the inverter unit 30 to stop outputting power; and in the process of pre-charging the bus capacitor 41, in the case that the voltage of the bus capacitor 41 is greater than the predetermined first voltage value V1, controlling the inverter unit 30 to supply power to the motor 200. In this way, in startup of the servo motor, activation and deactivation of short circuit braking are associated with switching of charge modes of a pre-charge circuit, which is conducive to lowering costs in additionally configuring a braking function.

In some exemplary embodiments, step S30 further includes: in the process of discharging the bus capacitor 41 upon power off of the AC mains power source, in a case that the voltage of the bus capacitor 41 is greater than a predetermined third voltage value V3, controlling the inverter unit 30 to supply power to the motor 200; and in the process of discharging the bus capacitor 41, in a case that the voltage of the bus capacitor 41 is less than the predetermined third voltage value V3, controlling the inverter unit 30 to switch to a free stop mode or a deceleration stop mode. The third voltage value V3 needs to be defined according to the need of braking, which should be less than or equal to the first voltage value V1 and greater than the second voltage value V2. In a process that the voltage of the bus capacitor 41 is decreased from the third voltage value V3 to the second voltage value V2, the motor 200 is gradually decelerated under the free stop mode or the deceleration stop mode, and short circuit braking is implemented in the case that the voltage of the bus capacitor 41 is decreased to the second voltage value V2. In this way, safety in stopping cars is enhanced. A difference between the third voltage value V3 and the second voltage value V2 ranges, for example, from 10 V to 20 V.

In some exemplary embodiments, step S20 further includes: in a case that the bus capacitor 41 is fully charged, controlling the inverter unit 30 to supply power to the motor.

Various embodiments of the present disclosure provide a servo driver, which is configured to perform the control method for the servo motor as described above. The servo motor is configured to drive the motor, wherein the motor is, for example, a permanent-magnet synchronous motor or a separately excited motor. FIG. 2 illustrates a servo driver according to an embodiment of the present disclosure. As illustrated in FIG. 2, a 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.

As illustrated in FIG. 2, the rectifier unit 10 is configured to be connected to an AC mains power source and capable of converting an AC power to a DC power. The DC bus 20 is connected to a DC power output terminal of the rectifier unit 10. The inverter unit 30 is connected to the DC bus 20 and capable of converting an DC power to an AC power. An AC power output terminal of the inverter unit 30 is configured to be connected to a 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 and subsequently connected between positive and negative terminals of the DC bus 20.

The switch unit 50 is connected to the pre-charge circuit 40 to be capable of short-circuiting two terminals of the pre-charge resistor 42. The switch unit 50 is connected to at least two phases of the AC power output terminal of the inverter unit 30 to be capable of establishing a short circuit between the at least two phases of the AC power output terminal of the inverter unit 30. Specifically, in the exemplary embodiments, the switch unit 50 includes a third relay 55. A controlled terminal of the third relay 55 includes a pair of first contacts 53 and a pair of second contacts 54. A pair of contacts 53 is connected in parallel to the pre-charge resistor 42 and subsequently connected in parallel to the bus capacitor 41. A pair of second contacts 54 is connected to two phases of the AC power output terminal of the inverter unit 30. The pair of first contacts 53 is conducted, and then two terminals of the pre-charge resistor 42 are short-circuited. The pair of second contacts 54 is conducted, and then the short circuit is established between two phases of the AC power output terminal of the inverter unit 30.

The voltage detection unit 60 is capable of detecting a voltage of the bus capacitor 41 and generating a voltage signal. The control unit 70 is connected to a control terminal of the third relay 55. The control unit 70 is capable of controlling the switch unit 50 based on the voltage signal, such that: in a process of pre-charging the bus capacitor 41, in a case that the voltage of the bus capacitor 41 is less than a predetermined first voltage value V1, the short circuit between the two terminals of the pre-charge resistor 42 is released (that is, the pair of first contacts 53 is disconnected) such that the pre-charge circuit is in a low-voltage charge mode, and the short circuit is established between the at least two phases of the AC power output terminal of the inverter unit 30 (that is, the pair of second contacts 54 is connected) such that short circuit braking of the servo motor is in an activated state; and in the process of pre-charging the bus capacitor 41, in a case that the voltage of the bus capacitor 41 is greater than the predetermined first voltage value V1, the two terminals of the pre-charge resistor 42 are short-circuited (that is, the pair of first contacts 53 is connected) such that the pre-charge circuit is in a high-voltage charge mode, and a short circuit between any two phases of the AC power output terminal of the inverter unit 30 is released (that is, the pair of second contacts 54 is disconnected) such that the short circuit braking of the servo motor is in a deactivated state. The first voltage value V1 needs to be defined according to the needs of pre-charging, which is generally 90%of the voltage of the DC bus, but is not limited to this value.

In some exemplary embodiments, the control unit 70 is capable of controlling the switch unit 50 based on the voltage signal, such that: in a process of discharging the bus capacitor 41 upon power off of the AC mains power source, in a case that the voltage of the bus capacitor 41 is greater than a predetermined second voltage value V2, the two terminals of the pre-charge resistor 42 are short-circuited (that is, the pair of first contacts 53 is connected) such that the pre-charge circuit is in the high-voltage charge mode, and the short circuit between the at least two phases of the AC power output terminal of the inverter unit 30 is released (that is, the pair of second contacts 54 is disconnected) such that short circuit braking of the servo motor is in the deactivated state; and in the process of discharging the bus capacitor 41 upon power off of the AC mains power source, in a case that the voltage of the bus capacitor 41 is less than the predetermined second voltage value V2, the short circuit between the two terminals of the pre-charge resistor 42 is released (that is, the pair of first contacts 53 is disconnected) such that the pre-charge circuit is in the low-voltage charge mode, and the short circuit is established between the at least two phases of the AC power output terminal of the inverter unit 30 (that is, the pair of second contacts 54 is connected) , such that the short circuit braking of the servo motor is in the activated state. The second voltage value V2 needs to be defined according to the need of braking, which should be less than the first voltage value V1. In this way, in shutdown of the servo motor, activation and deactivation of short circuit braking are associated with switching of charge modes of a pre-charge circuit, which is conducive to further lowering costs in additionally configuring a braking function.

In some exemplary embodiments, the control unit 70 is capable of controlling the switch unit 50 based on the voltage signal, such that: in a case that the bus capacitor 41 is fully charged, the two terminals of the pre-charge resistor 42 are short-circuited (that is, the pair of first contacts 53 is connected) , and a short circuit between any two phases of the AC power output terminal of the inverter unit 30 is released (that is, the pair of second contacts 54 is disconnected) , such that short circuit braking of the servo motor is in the deactivated state. In this way, in normal operation of the servo motor upon completion of startup, deactivation of short circuit braking is associated with a state where the bus capacitor is fully charged, which is conducive to further lowering costs in additionally configuring a braking function.

In some exemplary embodiments, the control unit 70 is capable of controlling the inverter unit 30 based on the voltage signal, such that: in the process of pre-charging the bus capacitor 41, in the case that the voltage of the bus capacitor 41 is less than a predetermined first voltage value V1, the inverter unit 30 stops outputting power; and in the process of pre-charging the bus capacitor 41, in the case that the voltage of the bus capacitor 41 is greater than the predetermined first voltage value V1, the inverter unit 30 supplies power to the motor 200. In this way, in startup of the servo motor, activation and deactivation of short circuit braking are associated with switching of charge modes of a pre-charge circuit, which is conducive to lowering costs in additionally configuring a braking function.

In some exemplary embodiments, the control unit 70 is capable of controlling the inverter unit 30 based on the voltage signal, such that: in the process of discharging the bus capacitor 41 upon power off of the AC mains power source, in a case that the voltage of the bus capacitor 41 is greater than a predetermined third voltage value V3, the inverter unit 30 supplies power to the motor 200; and in the process of discharging the bus capacitor 41 upon power off of the AC mains power source, in a case that the voltage of the bus capacitor 41 is less than the predetermined third voltage value V3, the inverter unit 30 switches to a free stop mode or a deceleration stop mode The third voltage value V3 needs to be defined according to the need of braking, which should be less than or equal to the first voltage value V1 and greater than the second voltage value V2. In a process that the voltage of the bus capacitor 41 is decreased from the third voltage value V3 to the second voltage value V2, the motor 200 is gradually decelerated under the free stop mode or the deceleration stop mode, and short circuit braking is implemented in the case that the voltage of the bus capacitor 41 is decreased to the second voltage value V2. In this way, safety in stopping cars is enhanced. A difference between the third voltage value V3 and the second voltage value V2 ranges, for example, from 10 V to 20 V.

In some exemplary embodiments, the control unit 70 is capable of controlling the inverter unit 30 based on the voltage signal, such that: in a case that the bus capacitor 41 is fully charged, the inverter unit 30 supplies power to the motor 200.

FIG. 4 illustrates a servo driver according to an embodiment of the present disclosure. The common or similar points between the servo driver according to this exemplary embodiment and the servo driver as illustrated in FIG. 2 are not described herein any further, and the differences between these two servo drivers are described hereinafter. In some exemplary embodiments, 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 a control terminal of the first relay 51 and a control terminal of the second relay 52. A 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 contacts 53 is connected in parallel to the pre-charge resistor 42 and subsequently connected in parallel to the bus capacitor 41. Two pairs of second contacts 54 are connected to the AC output terminal of the inverter unit 30, and short circuits are established between three phases of the AC output terminal of the inverter unit 30 by connecting the two pairs of second contacts 54 (that is, a pair of second contacts 54 at an upper side in FIG. 4 is connected, and a pair of second contacts 54 at a lower side in FIG. 4 is connected) . In this exemplary embodiment, the time for connection and disconnection of a pair of first contacts 53 is the same as the time for connection and disconnection of a pair of first contacts 53 described in the servo driver as illustrated in FIG. 2. In this exemplary embodiment, the time for connection and disconnection of a pair of second contacts 54 is the same as the time for connection and disconnection of a pair of second contacts 54 described in the servo driver as illustrated in FIG. 2.

Various embodiments of the present disclosure provide a servo motor. In an exemplary embodiment, the servo motor includes a motor 200 and a servo driver 100 as illustrated in FIG. 2 or 4. The motor 200 is, for example, a permanent-magnet synchronous motor or a separately excited motor. The servo motor is conducive to lowering costs in additionally configuring a braking function.

In this specification, in the deceleration stop mode, the inverter unit progressively decreases an output frequency in accordance with a predetermined deceleration time, and decreases the frequency to 0 Hz such that the motor stops. In the free stop mode, the inverter stops outputting power, and the motor stops freely in accordance to a mechanical inertial force.

It should be understood that, although this specification is described based on the embodiments, not each of the embodiments discloses an independent technical solution. Such description manner of the specification is only for clarity. A person skilled in the art should consider the specification as an entirety. The technical solutions according to the embodiments may also be suitably combined to derive other embodiments that may be understood by a person skilled in the art.

A series of detailed descriptions given in this specifically are merely intended to illustrate feasible embodiments of the present disclosure, instead of limiting the protection scope of the present disclosure. Any equivalent embodiments or modifications, for example, combinations, segmentations, or repetition of features, derived without departing from the spirit of the present disclosure shall fall within the protection scope of the present disclosure.

Claims

A control method for a servo motor, the servo motor comprising a servo driver and a motor, the servo driver comprising a rectifier unit, a DC bus, an inverter unit, a bus capacitor, and a pre-charge resistor, the rectifier unit being connected to an AC mains power source and capable of converting an AC power to a DC power, the DC bus being connected to a DC power output terminal of the rectifier unit, the inverter unit being connected to the DC bus and capable of converting a DC power to an AC power, the motor being connected to an AC power output terminal of the inverter unit, the bus capacitor and the pre-charge resistor being connected in series and subsequently connected between positive and negative terminals of the DC bus, two terminals of the pre-charge resistor being short-circuited by a circuit, wherein the control method comprises:

in a process of pre-charging the bus capacitor, in a case that a voltage of the bus capacitor is less than a predetermined first voltage value, releasing the short circuit between the two terminals of the pre-charge resistor, and establishing a short circuit between at least two phases of the AC power output terminal of the inverter unit; and

in the process of pre-charging the bus capacitor, in a case that the voltage of the bus capacitor is greater than the predetermined first voltage value, short-circuiting the two terminals of the pre-charge resistor, and releasing a short circuit between any two phases of the AC power output terminal of the inverter unit.
The control method according to claim 1, further comprising:

in a process of discharging the bus capacitor upon power off of the AC mains power source, in a case that the voltage of the bus capacitor is greater than a predetermined second voltage value, short-circuiting the two terminals of the pre-charge resistor, and releasing the short circuit between the any two phases of the AC power output terminal of the inverter unit, wherein the predetermined second voltage value is less than the predetermined first voltage value; and

in the process of discharging the bus capacitor upon power off of the AC mains power source, in a case that the voltage of the bus capacitor is less than the predetermined second voltage value, releasing the short circuit between the two terminals of the pre-charge resistor, and establishing the short circuit between the at least two phases of the AC power output terminal of the inverter unit.
The control method according to claim 1, further comprising: in a case that the bus capacitor is fully charged, short-circuiting the two terminals of the pre-charge resistor, and releasing the short circuit between the any two phases of the AC power output terminal of the inverter unit.
The control method according to claim 1, further comprising:

in the process of pre-charging the bus capacitor, in the case that the voltage of the bus capacitor is less than the predetermined first voltage value, controlling the inverter unit to stop outputting power; and

in the process of pre-charging the bus capacitor, in the case that the voltage of the bus capacitor is greater than the predetermined first voltage value, controlling the inverter unit to supply power to the motor.
The control method according to claim 2, further comprising:

in the process of discharging the bus capacitor upon power off of the AC mains power source, in a case that the voltage of the bus capacitor is greater than a predetermined third voltage value, controlling the inverter unit to supply power to the motor, wherein the predetermined third voltage value is less than or equal to the predetermined first voltage value and greater than the predetermined second voltage value; and

in the process of discharging the bus capacitor upon power off of the AC mains power source, in a case that the voltage of the bus capacitor is less than the predetermined third voltage value, controlling the inverter unit to switch to a free stop mode or a deceleration stop mode.
The control method according to claim 1, further comprising: in a case that the bus capacitor is fully charged, controlling the inverter unit to supply power to the motor.
A servo driver, configured to drive a motor (200) , wherein the servo driver comprises:

a rectifier unit (10) , configured to be connected to an AC mains power source and being capable of converting an AC power to a DC power;

a DC bus (20) , connected to a DC power output terminal of the rectifier unit (10) ;

an inverter unit (30) , connected to the DC bus (20) and being capable of converting an DC power to an AC power, wherein an AC power output terminal of the inverter unit (30) is connected to the motor (200) ;

a pre-charge circuit (40) , comprising a bus capacitor (41) and a pre-charge resistor (42) , wherein the bus capacitor (41) and the pre-charge resistor (42) are connected in series and subsequently connected between positive and negative terminals of the DC bus (20) ;

a switch unit (50) , connected to the pre-charge circuit (40) to be capable of short-circuiting two terminals of the pre-charge resistor (42) , wherein the switch unit (50) is connected to at least two phases of the AC power output terminal of the inverter unit (30) to be capable of establishing a short circuit between the at least two phases of the AC power output terminal of the inverter unit (30) ;

a voltage detection unit (60) , capable of detecting a voltage of the bus capacitor (41) and generating a voltage signal; and

a control unit (70) , capable of controlling the switch unit (50) based on the voltage signal, such that: in a process of pre-charging the bus capacitor (41) , in a case that the voltage of the bus capacitor (41) is less than a predetermined first voltage value, the short circuit between the two terminals of the pre-charge resistor (42) is released, and the short circuit is established between the at least two phases of the AC power output terminal of the inverter unit (30) ; and in the process of pre-charging the bus capacitor (41) , in the case that the voltage of the bus capacitor (41) is greater than the predetermined first voltage value, the two terminals of the pre-charge resistor (42) are short-circuited, and a short circuit between any two phases of the AC power output terminal of the inverter unit (30) is released.
The servo driver according to claim 7, wherein the control unit (70) is capable of controlling the switch unit (50) based on the voltage signal, such that: in a process of discharging the bus capacitor (41) upon power off of the AC mains power source, in a case that the voltage of the bus capacitor (41) is greater than a predetermined second voltage value, the two terminals of the pre-charge resistor (42) are short-circuited, and the short circuit between the at any two phases of the AC power output terminal of the inverter unit (30) is released, wherein the predetermined second voltage value is less than the predetermined first voltage value; and in the process of discharging the bus capacitor (41) upon power off of the AC mains power source, in a case that the voltage of the bus capacitor (41) is less than the predetermined second voltage value, the short circuit between the two terminals of the pre-charge resistor (42) is released, and the short circuit is established between the at least two phases of the AC power output terminal of the inverter unit (30) .
The servo driver according to claim 7, wherein the control unit (70) is capable of controlling the switch unit (50) based on the voltage signal, such that: in a case that the bus capacitor (41) is fully charged, the two terminals of the pre-charge resistor (42) are short-circuited, and the short circuit between the any two phases of the AC power output terminal of the inverter unit (30) is released.
The servo driver according to claim 7, wherein the switch unit (50) comprises a pair of contacts (53) and a group of second contacts (54) , wherein the pair of contacts (53) is connected in parallel to the pre-charge resistor (42) and subsequently connected in parallel to the bus capacitor (41) , and the group of second contacts (54) is connected to the AC power output terminal of the inverter unit (30) .
The servo driver according to claim 10, wherein the switch unit (50) comprises a first relay (51) and a second relay (52) , wherein the control unit (70) is connected to a control terminal of the first relay (51) and a control terminal of the second relay (52) , a controlled terminal of the first relay (51) comprises the pair of first contacts (53) , and a controlled terminal of the second relay (52) comprises the group of second contacts (54) ; or

the switch unit (50) comprises a third relay (55) , the control unit (70) is connected to a control terminal of the third relay (55) , and a controlled terminal of the third relay (55) comprises the pair of first contacts (53) and the group of second contacts (54) .
The servo driver according to claim 7, wherein the control unit (70) is capable of controlling the inverter unit (30) based on the voltage signal, such that: in the process of pre-charging the bus capacitor (41) , in the case that the voltage of the bus capacitor (41) is less than a predetermined first voltage value, the inverter unit (30) stops outputting power; and in the process of pre-charging the bus capacitor (41) , in the case that the voltage of the bus capacitor (41) is greater than the predetermined first voltage value, the inverter unit (30) supplies power to the motor (200) .
The servo driver according to claim 8, wherein the control unit (70) is capable of controlling the inverter unit (30) based on the voltage signal, such that: in the process of discharging the bus capacitor (41) upon power off of the AC mains power source, in a case that the voltage of the bus capacitor (41) is greater than a predetermined third voltage value, the inverter unit (30) supplies power to the motor (200) , wherein the predetermined third voltage value is less than or equal to the predetermined first voltage value and greater than the predetermined second voltage value; and in the process of discharging the bus capacitor (41) upon power off of the AC mains power source, in a case that the voltage of the bus capacitor (41) is less than the predetermined third voltage value, the inverter unit (30) switches to a free stop mode or a deceleration stop mode.
The servo driver according to claim 7, wherein the control unit (70) is capable of controlling the inverter unit (30) based on the voltage signal, such that: in a case that the bus capacitor (41) is fully charged, the inverter unit (30) supplies power to the motor (200) .
A servo motor, comprising: a motor (200) and the servo driver as defined in claim 7.