JP5147370B2 - Servo motor control device - Google Patents

Description

  The present invention relates to a servo motor control device, and more particularly to the structure of a current detection unit of a servo motor control device.

  Conventionally, as a means for detecting a current flowing through a servo motor in a servo motor control apparatus, resistance detection or detection using a current sensor is generally used. In the case of resistance detection, the resistor is soldered to the substrate and a current is passed through the pattern. The current flowing through the resistor is detected as a voltage value and calculated as the current flowing through the servo motor. Such resistance detection is a highly accurate detection means with little variation in detection due to the ambient temperature. However, when a large current is passed, the temperature of the resistor itself and the temperature of the substrate pattern increase due to heat generation. Since this temperature rise may cause peeling of the solder or damage to the substrate pattern, it is generally unsuitable for a large current detection means.

  On the other hand, the current sensor method detects a current flowing through an electric wire, a conductor, or the like by using a Hall element that is a magnetoelectric conversion element using the Hall effect by passing an electric current through the electric wire, the conductor, or the like. In this case, since the conductor is directly connected to the terminal or terminal block of the power module, the temperature of the substrate pattern does not increase even when a large current is passed, and is generally used as a current detection means for a large current ( For example, refer to FIG.

Japanese Patent Laid-Open No. 2006-38834, FIG.

  However, according to the conventional technique, the current sensor method has a problem that the detection accuracy is deteriorated due to the ambient temperature, and the detection accuracy is inferior to the resistance detection. In addition, the structure of the servo motor control device, such as the arrangement of current sensors and the arrangement of conductors, is complicated as compared with the resistance detection method.

  The present invention has been made in order to solve the above problem, and can detect a large current flowing to the servomotor with high accuracy and can further simplify the structure. The object is to obtain a control device.

  In order to solve the above-described problems and achieve the object, the servo motor control device of the present invention includes a current detection unit that detects a current flowing through the servo motor, and servos using the current value detected by the current detection unit. This is a servo motor control device that controls the motor, and the current detection unit is provided separately from the substrate and supplies power from the power supply unit to the servo motor and serves as a current detection resistor for current detection A dual-purpose conductor and a current detector that detects a current flowing through the servomotor from a voltage output to a current detection terminal connected to two predetermined positions of the dual-purpose resistor conductor.

  According to the present invention, the current detection unit has the resistance-cum-use conductor that serves as a current-detection resistance at the time of current detection while supplying the electric power from the power supply portion to the servo motor. The flowing current is detected as a voltage value and calculated as a current flowing in the servo motor. Therefore, there is little detection variation due to the ambient temperature, and highly accurate current detection is possible. On the other hand, since the resistor / conductor is provided separately from the substrate, the substrate and the substrate pattern do not increase in temperature even when a large current flows. Therefore, it is possible to prevent solder peeling and substrate pattern damage due to temperature rise. Furthermore, since the resistor combined conductor combines the role of a conductor that supplies power from the power supply unit to the servo motor and the role of the current detection resistor at the time of current detection with one member, the number of parts is reduced, The structure is simplified.

  Embodiments of a servo motor control apparatus according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment FIG. 1 is a block diagram of a servo motor control apparatus according to the present embodiment. In FIG. 1, a three-phase AC power source 1 that generates a three-phase (R phase, S phase, T phase) AC power source is connected to a converter unit 2 that rectifies a three-phase AC voltage into a DC voltage. The converter unit 2 is connected to an inverter unit 3 that controls a three-phase AC motor 4 (hereinafter referred to as a motor 4), and the inverter unit 3 and the motor 4 are connected via a current detection unit 6. Here, the converter unit 2 includes AC power supply terminals 41, 42, 43 and DC power supply terminals 21, 22. The AC power supply terminals 41, 42 and 43 are connected to the power supply terminals of the three-phase AC power supply 1. The DC power terminals 21 and 22 of the converter unit 2 are connected to the DC power terminals of the inverter unit 3. In the converter unit 2, DC buses 23 and 24 connected to DC power supply terminals 21 and 22 are arranged, and a smoothing capacitor 40 is connected between the DC buses 23 and 24.

In the converter unit 2, rectifying diodes 15, 16, 17, 18, 19, and 20 are provided. The rectifying diodes 15 and 16, the rectifying diodes 17 and 18, which are connected in series between the DC buses 23 and 24, Three sets of diodes 19 and 20 are connected in parallel. That is, the cathode terminals of the rectifying diodes 15, 17, 19 are connected to the DC bus 23, and the anode terminals of the rectifying diodes 16, 18, 20 are connected to the DC bus 24. Then, the cathode terminal of the anode terminal and the rectifying diode 16 of the rectifying diode 15 is connected to an AC power supply terminal 41 in common. Similarly, the cathode terminal of the anode terminal of the rectifier diode 17 and the rectifying diode 18 is connected to an AC power supply terminal 42 to the common anode terminal of the rectifying diode 19 and the cathode terminal of rectifier diode 20 is common Are connected to the AC power supply terminal 43.

  On the other hand, the inverter unit 3 includes switching elements 25, 26, 27, 28, 29 and 30. The DC voltage terminal 21 is connected to collector terminals of switching elements 25, 27, and 29 that constitute the upper arm, and the DC voltage terminal 22 is connected to emitter terminals of switching elements 26, 28, and 30 that constitute the lower arm. Is done. The emitter terminal of the switching element 25 and the collector terminal of the switching element 26 are connected to the AC power supply terminal 37 in common. Similarly, the emitter terminal of the switching element 27 and the collector terminal of the switching element 28 are commonly connected to the AC power supply terminal 38, and the emitter terminal of the switching element 29 and the collector terminal of the switching element 30 are commonly connected to the AC power supply terminal. 39. These switching elements 25, 26, 27, 28, 29, and 30 are respectively connected in parallel with free-wheeling diodes 31, 32, 33, 34, 35, and 36. The cathode terminal of the free-wheeling diode is the collector of the switching element. Connected to the terminal.

The AC power terminals 37, 38, 39 in the inverter unit 3 are connected to the motor 4 and supplied with AC power output by PWM control. In order to detect the current flowing from the inverter unit 3 to the motor 4, a current detection unit 6 is provided. A detection unit 5 is provided for detecting the position feedback, speed feedback, and magnetic pole position of the motor 4. The alternating current values i _ua , i _va , i _wa detected by the current detector 6 and the magnetic pole position θ _re detected by the detector 5 are input to the current controller 46.

  In the U phase, the current detection unit 6 includes a resistance-cum-use conductor (hereinafter referred to as a conductor-integrated current detection resistor) 51 connected in series between the AC power supply terminal 37 of the inverter unit 3 and the motor 4, A current detector 71 that flows to the motor 4 from the voltage output to the current detection terminals 58 and 59 connected to two predetermined positions of the body-type current detection resistor 51; The conductor-integrated current detection resistor 51 is connected between the AC power supply terminal 37 and the motor 4 via energization terminals 56 and 57 provided at both ends. Similarly, in the V phase, the current detection unit 6 includes a conductor-integrated current detection resistor 61 connected in series between the AC power supply terminal 38 of the inverter unit 3 and the motor 4, and predetermined conductor-integrated current detection resistors 61. And a current detector 81 that flows to the motor 4 from the voltage output to the current detection terminals 68 and 69 connected to the two locations. The conductor-integrated current detection resistor 61 is connected between the AC power supply terminal 38 and the motor 4 via energization terminals 66 and 67 provided at both ends. The conductor-integrated current detection resistors 51 and 61 supply power output from the module unit (inverter unit) 3 constituting the power supply unit to the motor 4 and also serve as current detection resistors for current detection.

  FIG. 2 is a perspective view showing a main part of the current detection unit 6 of FIG. In FIG. 2, only the U-phase portion of the current detector 6 is shown, but the V-phase portion has a substantially similar configuration. The conductor integrated current detection resistor 51 is provided separately from the substrate 90. The conductor-integrated current detection resistor 51 is manufactured by bending a plate-shaped metal material having a predetermined electric resistance. The conductor-integrated current detection resistor 51 includes flat portions 51a and 51b that are parallel to the substrate 90, and vertical portions 51c and 51d that are perpendicular to the substrate 90. In particular, the vertical portions 51c and 51d are provided. The heat dissipation is improved. Current detection terminals 58 and 59 are connected to the conductor-integrated current detection resistor 51 at two locations separated by a predetermined distance so as to have a predetermined resistance value. Connection portions of the current detection terminals 58 and 59 are provided in the vertical portions 51c and 51d so that screws can be easily attached when the terminals are attached. For the purpose of arbitrarily changing the resistance value, two or more mounting portions of the current detection terminal may be provided and any two of them may be selected and connected. Further, if the current detection terminals 58 and 59 are connected to the current detection terminals 58 and 59 at a position away from the substrate 90 to the extent that the tool does not interfere with the substrate 90 when the current detection terminals 58 and 59 are attached, the vertical portions 51c and 51d are connected. The present invention is not limited to this, and the same effect can be obtained even if it is provided at other locations.

  A hole 90 a is formed in the substrate 90 for the purpose of installing the conductor integrated current detection resistor 51 without contacting the substrate 90. The energization terminal 56 at one end of the conductor integrated current detection resistor 51 is supported on the power module (inverter unit 3) at a position raised by the stat 3a. An energization terminal 57 at the other end of the conductor integrated current detection resistor 51 is connected to a terminal block 53 on the substrate 90. The conductor-integrated current detection resistor 51 is supported by the stat 3 a and the terminal block 53, and is disposed at a position away from the surface of the substrate 90 by a predetermined distance. The stat 3a and the terminal block 53 constitute a raising means for raising the conductor-integrated current detection resistor 51. The raising means is not limited to the stat 3a and the terminal block 53, but may be constituted by other members or the shape of the conductor integrated current detection resistor 51 itself.

  The peripheral portion of the vertical portion 51c on the side where the current detection terminal 59 is attached has a rectangular uneven shape. This is because when the resistance value between the current detection terminals 58 and 59 is adjusted to a predetermined value, the volume (area) of the conductor-integrated current detection resistor 51 is increased or decreased by a predetermined amount. Concavities and convexities having a predetermined width are formed to facilitate the design. The uneven shape is not limited to a rectangle, but may be an arc shape or the like, that is, a predetermined effect can be obtained as long as the volume (area) is easily obtained. Lead wires extending from the current detection terminals 58 and 59 are connected to the connector 54. The connector 54 is connected to the connector 55 on the substrate 90. The connector 55 is connected to a current detector 71 (FIG. 1) (not shown) by a board pattern (not shown).

  The conductor-integrated current detection resistor 51 according to the present embodiment includes flat portions 51a and 51b and vertical portions 51c and 51d. However, this is merely an example, and is not particularly limited to such a shape. It may be a free shape according to the surrounding situation. At this time, by arranging the conductor-integrated current detection resistor at a position away from the surface of the substrate by a predetermined distance as described above, it is possible to obtain an effect such as blocking heat transfer, for example.

  Returning to FIG. 1, the current control unit 46 will be described. The current control unit 46 includes a three-phase AC current → dq axis conversion unit 9, a current controller 11, a current controller 12, a dq axis → three-phase AC voltage conversion unit 10, a PWM waveform generation unit 13, and a subtractor 45a, 45b.

The three-phase alternating current → dq axis conversion unit 9 will be described. The AC current values i _ua , i _va , i _wa and the magnetic pole position θ _re are input to the three-phase AC current → dq axis conversion unit 9. The three-phase alternating current → dq axis converter 9 converts the current value according to the equation (2).

The alternating current value is converted into a current value corresponding to the dq axis by the equation (2). In addition, as shown in FIG. 1, even when the current detection unit is provided only in the U phase and the V phase and the current detection unit is not provided in the W phase, the U, V phase → dq axis conversion is performed by the equation ( 3 ). Can do.

  The above equation is a case where there is no current detection unit in the W phase, but the same can be considered when there is no current detection unit in the U phase or the V phase.

Next, the dq axis → three-phase AC voltage conversion unit 10 will be described. _Differences between the current command values i _qcmd and i _dcmd and the current values i _qa and i _da are calculated by the subtracters 45a and 45b and input to the current controller 11 and the current controller 12, respectively. The voltage commands V _qa and V _da that are the outputs of the current controller 11 and the current controller 12 and the magnetic pole position θ _re are input to the dq axis → three-phase AC voltage converter 10. The dq axis → three-phase AC voltage converter 10 performs the conversion shown in Expression (4).

The dq-axis voltage command is converted into a three-phase AC voltage command V _ua , V _va , V _wa by equation (4).

Next, the PWM waveform generation unit 13 will be described. The PWM waveform generation unit 13 performs on / off control on the switching elements 25, 26, 27, 28, 29, and 30 in the inverter unit 3 based on the three-phase AC voltage commands V _ua , V _va , and V _wa. A pulse signal for performing is generated. The output terminals of the pulse waveform generator are connected to corresponding terminals of the switching elements 25, 26, 27, 28, 29, 30. Thereby, the switching element is turned on / off, and the motor 4 is driven.

  Next, the flow of current control of the servo motor control device including the current control unit will be described with reference to FIG. First, a q-axis current command is input and input to the dq-axis → three-phase AC voltage converter 10 through the current controller. U-phase voltage, V-phase voltage, and W-phase voltage are output and input to the PWM waveform generation unit 13 to perform on / off control on the switching elements 25, 26, 27, 28, 29, and 30 in the inverter unit 3. Send a signal. Accordingly, the switching element is turned on / off, and a current flows through the motor 4. This current is detected by the current detection unit 6 and input to the current control unit 46 for current control.

  When two or more current sensors are used for the current detection unit, the current sensor itself takes up space, which complicates the structure such as the conductor placement method and current sensor placement method. When the conductor integrated type current detection resistors 51 and 61 are used in the current detection unit 6 as in this embodiment, there is an advantage that the structure can be simplified by arranging only the conductor.

  Similarly to the case of using the current sensor, the current-carrying terminals 56, 57, 66, 67 of the conductor integrated current detection resistors 51, 61 are connected to the terminals of the power module (inverter unit 3) and the terminal block 53, respectively. Even if a large current is passed, the substrate temperature can be prevented from rising.

  Since the distance between the current detection terminals 58, 59, 68, and 69 of the conductor integrated current detection resistors 51 and 61 becomes the current detection resistance value, the resistance value increases by increasing the distance between the terminals. In the current detection method using resistance detection, the voltage between the current detection terminals is detected, and the current value is calculated based on this value.

If the current detection resistance value R in the equation ( 5 ) is increased, the voltage V between terminals can be increased even if the current value I flowing through the servomotor is small, and highly accurate current detection can be performed. However, the resistance heat generation temperature is determined by the resistance value and the flowing current. When the current detection resistor soldered to the substrate passes a large current, it is general to suppress the heat generation by reducing the current detection resistance value R.

  Since the conductor integrated current detection resistors 51 and 61 of the present embodiment are the entire conductor, the heat generation amount of the current detection resistor is the heat generation amount of the entire conductor and does not depend on the current detection resistance value. Therefore, even if the current detection resistance value is increased, the amount of generated heat does not change. Therefore, by increasing the current detection resistance value as much as possible in the structure, current detection with higher accuracy can be realized.

  Moreover, if a low resistance material such as copper is attached to the resistor part outside the current detection terminals that do not directly detect current, the resistance value of the entire conductor can be reduced and the amount of heat generated can be reduced. .

  As described above, the servo motor control device according to the present invention is useful for a servo motor control device in which simplification of the structure and improvement in detection accuracy are desired. It is optimal for servo motor control devices that require accurate current detection.

It is a block diagram which shows embodiment of the servomotor control apparatus concerning this invention. It is a perspective view which shows the principal part of the electric current detection part of FIG.

Explanation of symbols

1 Three-phase AC power supply 2 Converter unit 3 Inverter unit 3a Stat 4 Three-phase AC motor 5 Detection unit
6 Current detector 9 Three-phase AC current → dq axis converter 10 dq axis → Three phase AC voltage converter 11, 12 Current controller 13 PWM waveform generator 15, 16, 17, 18, 19, 20 Rectifier diode 21 , 22 DC power supply terminal 23, 24 DC bus 25, 26, 27, 28, 29, 30 Switching element 31, 32, 33, 34, 35, 36 Free-wheeling diode 37, 38, 39 AC power supply terminal 40 Smoothing capacitor 41, 42 , 43 AC power supply terminals 45a, 45b Subtractor 46 Current control unit 51, 61 Conductor-integrated current detection resistor (resistance and conductor)
53 Terminal block 54, 55 Connector 56, 57, 66, 67 Current terminal
5 8, 59, 68, 69 Current detection terminal
7 1,81 Current detector 90 Substrate

Claims (8)

In a servo motor control device that includes a current detection unit that detects a current flowing through the servo motor, and that controls the servo motor using a current value detected by the current detection unit,
The current detector is
The substrate provided separately supplies the power from the power supply unit without going through the substrate to the servo motor, and resistance combined conductor which serves as a current detecting resistor at the time of current detection,
A current detector for detecting a current flowing through the servomotor from a voltage output to a current detection terminal connected to two predetermined positions of the resistor-cum-conductor,
A first support member that supports one end of the resistance-cum-use conductor so that the resistance-use conductor does not contact the substrate;
A second support member for supporting the other end of the resistor / conductor so that the resistor / conductor does not contact the substrate;
I have a,
The servo motor control device according to claim 1, wherein the resistor / conductor is configured to radiate heat without passing through the substrate . The first support member supports one end of the resistor / conductor so as not to contact the substrate, and electrically connects one end of the resistor / conductor to a power module;
The second support member supports the other end of the resistor / conductor in a position raised from the substrate , and electrically connects the other end of the resistor / conductor to the servo motor. The servo motor control device according to claim 1. The resistance combined conductor, have a vertical portion extending away from the substrate than the first and second ends,
The servo motor control device according to claim 1, wherein the vertical portion has an inverted U shape that is farther from the substrate at a central portion than at one end side and the other end side . The servomotor control device according to any one of claims 1 to 3, wherein the resistance-use conductor is formed by bending a plate-shaped metal material. The servomotor control device according to any one of claims 1 to 4, wherein the resistance-use conductor is provided with two or more current detection terminal mounting portions. The resistance-use conductor is supported by the first support member and the second support member, and is disposed at a predetermined distance from the substrate. 6. Servo motor control device according to item. The mounting portion of the current detection terminal is provided on the resistance-use conductor at a position away from the substrate so that the tool does not interfere with the substrate when the current detection terminal is attached. The servo motor control device according to any one of 1 to 6. The servo motor control device according to claim 3, wherein an uneven shape is formed in a peripheral portion of the vertical portion, and the resistance value is easily adjusted by increasing or decreasing the uneven shape.

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