Control device and control method for brushless motor

Abstract

Control device for a brushless three-phase motor (112), comprising: a shunt resistor (220) for measuring a phase current of the brushless motor (112); and a controller (110) that measures the phase current of the brushless motor (112) in a single-shunt system using the shunt resistor (220) and controls the driving of the brushless motor (112) based on the measured phase current, wherein the controller (110) performs a pulse shift when a voltage pulse width in a drive wire (210u, 210v, 210w) of the brushless motor (112) is greater than a predetermined value, whereas the controller (110) does not perform the pulse shift when the voltage pulse width is less than the predetermined value, wherein the controller (110) comprises a drive circuit (200) that drives the brushless motor (112), and a control unit (300) that controls the drive unit (200), and wherein the control unit (300) switches between a state,The system switches between a state in which d-axis and q-axis current controls are performed, and a state in which d-axis and q-axis current controls are not performed, based on whether or not pulse shifting is performed.

Description

TECHNICAL AREA

[0001] The present invention relates to a control device and a control method for a brushless motor for use in an electric actuator, an electric pump and the like. BACKGROUND TECHNOLOGY

[0002] Traditionally, a brushless motor is controlled using vector control, in which the d-axis current and the q-axis current are controlled independently. In vector control, since the d-axis current is a reactive component, it is typically set to 0 A. Since the q-axis current contributes to the motor torque, a current equivalent to the required torque is specified as a command value. To measure the phase current, it is common to use a system employing three shunt resistors (three-shunt system) or a system employing a single shunt resistor (one-shunt system).

[0003] Although the first method can continuously measure the phase current, it requires three shunt resistors, resulting in higher costs. On the other hand, the latter requires only one shunt resistor, and consequently, the costs can be low; however, the current can only be detected when the voltage pulse is applied. Furthermore, if a ringing effect or damped oscillation occurs in the phase current at the time the voltage pulse is applied, an accurate current value cannot be obtained until the current stabilizes. Thus, the voltage pulse width (sensing width) is limited.

[0004] For example, patent document 1 in the fourth embodiment discloses a technique in which the voltage is corrected during a monotonically increasing period of the triangular wave carrier and the correction amount is subtracted from it during a subsequent monotonically decreasing period so that the averaged voltage becomes zero, and then the current is measured at the time when the damped oscillation stops (hereinafter referred to as pulse shift). REFERENCE DOCUMENT DUCK LIST PATENT DOCUMENT

[0005] Patent document 1: WO 2010 / 103565 SUMMARY OF THE INVENTION PROBLEM TO BE SOLVED BY THE INVENTION

[0006] When pulse shifting is used to drive a brushless motor, for example, for position control in an electric actuator within a variable compression ratio (VCR) machine, there is a possibility of unpleasant noise (hissing) occurring while the angle is held constant. This is because the current oscillates (varies) significantly as a result of the pulse shifting. Such noise, occurring during constant-angle control, cannot be ignored in a low-noise machine or one without an idle function, and this could pose a problem.

[0007] The present invention was made in view of such circumstances, and one object of the present invention is to provide a control device and a control method for a brushless motor that can reduce noise resulting from pulse shift processing. MEANS TO SOLVE THE PROBLEM

[0008] According to the present invention, a control or driver device for a brushless three-phase motor comprises: a shunt resistor for measuring a phase current of the brushless motor; and a controller that measures the phase current of the brushless motor in a single-shunt system using the shunt resistor and controls the drive of the brushless motor based on the measured phase current, wherein the controller performs a pulse shift when a voltage pulse width in a drive wire of the brushless motor is greater than a predetermined value, whereas the controller does not perform the pulse shift when the voltage pulse width is less than the predetermined value.

[0009] According to the present invention, a control method for a brushless three-phase motor by measuring a phase current in a single-shunt system further comprises the following steps: Measuring a voltage pulse width in a control wire of the brushless motor; Comparing the measured voltage pulse width with a predetermined value; and Performing a pulse shift if the measured voltage pulse width is greater than the predetermined value, whereas the pulse shift is not performed if the measured voltage pulse width is less than the predetermined value. EFFECTS OF INVENTION

[0010] According to the present invention, since the pulse shift is performed when the voltage pulse width in the drive wire of the brushless motor is greater than the predetermined value, a sufficiently accurate current value for use in a vector control can be detected, and since the pulse shift is not performed when the voltage pulse width is less than the predetermined value, it is possible to reduce noise. List of characters Fig.Figure 1 is a schematic cross-sectional configuration view of a variable compression ratio machine for which a control device for a brushless motor according to the present invention is used. Fig. Figure 2 is a block diagram to illustrate a control device for a brushless motor according to an embodiment of the present invention, wherein the diagram illustrates essential parts extracted from an electric actuator and a VCR controller, which are in Fig. 1 are illustrated. Fig. Figure 3 is a circuit diagram that shows an example of the structure of a drive circuit in the VCR controller of Fig. 2 illustrated. Fig. Figure 4 is a functional block diagram that shows an example of the control unit in the VCR controller of Fig. 2 illustrated. Fig.Figure 5 is a flowchart to illustrate a control method for a brushless motor according to an embodiment of the present invention. Fig. Figure 6A is a waveform diagram to illustrate the acquisition of phase current information when pulse shift processing is performed. Fig. Figure 6B is a waveform diagram to illustrate the acquisition of phase current information when pulse shift processing is performed. Fig. Figure 6C is a waveform diagram to illustrate the acquisition of phase current information when pulse shift processing is performed. Fig. Figure 7 is a waveform diagram illustrating the V-phase current and the U-phase current when the momentum shift is performed. Fig.Figure 8 is a waveform diagram illustrating the V-phase current and the U-phase current when the momentum shift is not performed. MODE FOR EXECUTING THE INVENTION

[0011] The following describes embodiments of the present invention with reference to the accompanying drawings.

[0012] Fig. Figure 1 is a schematic cross-sectional configuration view of a machine and illustrates a variable compression ratio machine for which a control device for a brushless motor according to the present invention is used. This machine 10 contains a mechanism 100 for a variable compression ratio, which determines the position of the top dead center of a piston 12 makes it variable.

[0013] In the mechanism 100 A crankshaft is required for a variable compression ratio. 14 and a piston 12through a lower connecting link 16 and an upper connecting link 18 coupled, and a control link 20 regulates the movement of the lower connecting link 16 , to determine the position of the piston's top dead center 12 to change the compression ratio. Changing the position of the piston's top dead center. 12 to a higher position or a change in the position of the piston's top dead center 12 in that it is a cylinder head 21 This approach is referred to as an increase in the compression ratio. A change in the position of the piston's top dead center. 12 to a lower position or a change in the position of the piston's top dead center 12 away from the cylinder head 21 This is described as a reduction in the compression ratio.

[0014] The lower connecting link 16is designed in such a way that it is divisible into two elements, a right element and a left element, and the lower connecting link 16 is connected by a coupling hole provided essentially in the middle on a crank pin 14b the crankshaft 14 attached. The lower connecting link 16 rotates around the crankpin 14b than the axis.

[0015] The crankshaft 14 includes several bearing journals 14a and crankpin 14b . Each bearing journal 14a is from a cylinder block 22 and a ladder frame 24 Rotatably supported. Each crankpin 14b is off-center from the bearing journal by a predetermined amount 14a arranged, and the lower connecting link 16 is connected to the crank pin 14b Rotatably coupled.

[0016] One end of the lower connecting link 16 is connected by a coupling pin26 with the upper connecting link 18 coupled, and the other end of the lower connecting link 16 is connected via a coupling pin 28 with the control link 20 coupled.

[0017] The lower end of the upper connecting link 18 is through the coupling pin 26 with one end of the lower connecting link 16 coupled, and the upper end of the upper connecting link 18 is through a piston pin 30 with the piston 12 coupled.

[0018] The piston 12 moves due to the combustion pressure exerted on it in a cylinder 22a a cylinder block 22 back and forth.

[0019] One end of the control link 20 is connected by a coupling pin located at the tip of the end. 28 with the lower connecting link 16Rotatably coupled. The other end of the control link 20 is connected by a coupling pin 32 off-center with a control shaft 36 coupled. Consequently, the control link oscillates. 20 around the coupling pin 32 than the middle.

[0020] On the outer circumference of the control shaft 36 A gear is formed. The gear is connected to a pinion. 106 in engagement, which is on a rotating shaft 104 an electric actuator 102 is arranged. The electric actuator 102 drives the control wave 36 so that it rotates, and thereby the coupling pin moves. 32 The electric actuator 102 includes a built-in brushless three-phase motor (BLM) 112 as a power source. The brushless motor 112 It is designed to rotate forwards and backwards. Consequently, the rotating shaft rotates.104 and the pinion 106 and ultimately the control shaft 36 forwards and backwards, and this makes it possible to determine the position of the piston's top dead center. 12 to move to both the side of a low compression ratio and the side of a high compression ratio.

[0021] Moreover, with one end of the control shaft 36 a rotation angle sensor (for example, a resolver or coordinate converter sensor) 108 connected, which measures a current rotation angle that is a real rotation angle of the control shaft 36 is. A signal of the current rotation angle of a sensor by which this rotation angle sensor 108 The measured current rotation angle is sent to a VCR controller. 110 delivered. The current rotation angle of the control shaft 36is a parameter that corresponds to a current top dead center position (real operating position), which is a real position of the piston's top dead center. 12 is.

[0022] A main controller 42 controls a fuel injection system of a fuel injection device (fuel injection valve) 38 , which injects fuel directly into the cylinder, and controls the ignition timing of a spark plug (ignition coil) 40 This main controller 42 It contains a microcomputer equipped with a CPU, ROM, RAM, input and output interfaces, and the like. The main controller 42 receives measurement signals provided by various sensors, such as a load sensor 44 , which is a machine load TP of the machine 10 measures, a rotation sensor 46 , which is a rotational speed NE of the machine 10 measures, a water temperature sensor48 , which is a temperature (machine temperature) TW of a coolant of the machine 10 measures. The main controller 42 Based on the measurement signals from the various sensors, it provides control signals (operating signals) to a fuel injection device. 38 spark plug 40 or the like.

[0023] Moreover, the main controller estimates 42 a load condition of the machine 10 (for example, the acceleration state of a vehicle) based on the measurement signals from the various sensors. The main controller 42 depending on the estimated load condition of the machine 10 a signal corresponding to the target position of the top dead center (target operating position), which is a target of the position of the top dead center of the piston. 12 It should be a signal indicating a target rotation angle of the control shaft. 36 in the mechanism 100for a variable compression ratio, to a subordinate VCR controller 110 from, which is communicatively connected via an onboard network such as a Controller Area Network (CAN).

[0024] The VCR controller 110 It contains a microcomputer equipped with a CPU, ROM, RAM, input and output interfaces, and the like. This VCR controller 110 controls the electric actuator 102 (brushless motor) 112 ) in the mechanism 100 for a variable compression ratio to the control shaft 36 to rotate based on the angle sensor 108 received signal of the current rotation angle and the signal from the main controller 42 received signal of the target rotation angle of the control shaft 36 This allows the VCR controller 110 the position of the piston's top dead center 12to change the compression ratio (mechanical compression ratio) of the machine 10 to change to a lower compression ratio or a higher compression ratio.

[0025] Specifically, the VCR controller 110 a target current value for the brushless motor 112 supplied current depending on a deviation between the current rotation angle and the target rotation angle of the control shaft 36 and introduces a regulation of the current based on a difference between the set target current value and the current value currently being supplied by the brushless motor. 112The current flowing through the system is controlled by vector control on a dq coordinate system, which is a rotating orthogonal coordinate system. The dq coordinate system is defined such that the direction of a field rotating synchronously with a permanent magnet rotor is aligned along the d-axis, and the torque generation direction, orthogonal to the d-axis, is aligned along the q-axis.

[0026] Fig. Figure 2 illustrates an example of the structure by extracting essential parts from the electrical actuator. 102 and the VCR controller 110 in Fig. 1, which are involved in controlling the brushless motor. The electric actuator 102 includes the built-in brushless motor 112 The brushless motor 112 includes: a (not illustrated) cylindrical stator in which U-phase, V-phase and W-phase coils114u , 114v , 114w are wound; and a rotor 120 , which is a permanent magnet rotor designed to rotate at the center of the stator. The rotational position of the rotor 120 is provided by a rotation angle sensor 108 felt. One end of each of the coils 114u , 114v , 114w is usually connected (connected in a star configuration), and each of the other ends is connected to the corresponding control wire. 210u , 210v , 210w of the VCR controller 110 connected. The brushless motor 112 It could be a motor in which the three-phase coils 114u , 114v , 114w are connected by a delta connection.

[0027] The VCR controller 110 contains a control or driver circuit (inverter circuit) 200 , a shunt resistor (single-shunt system) 220, which measures a phase current at the time a voltage pulse is applied to the brushless motor 112 is installed, an onboard power supply 230 , such as a battery and a control unit 300 The control unit 300 generates gate voltages From , Vvv , VW to control each switching element in the control circuit 200 , which is to be switched on or off, based on an actuator command angle and an actuator angle (measured value) provided by the main controller 42 be provided, a measured value of the three-phase current, which is passed through the shunt resistance 220 is measured, and a signal of the current rotation angle (sensor output for measuring a motor angle), which represents the current rotation angle of the brushless motor. 112 represented, measured by the rotation angle sensor 108 , and then the control unit 300 Gate voltages From, Vvv , VW the control circuit 200 ready.

[0028] The control circuit 200 provides three-phase connection voltages From , Vvd , VW for controlling the brushless motor 112 under pulse width modulation (PWM) control via the corresponding control wires 210u , 210v , 210w ready.

[0029] As in Fig. As illustrated in section 3, the control circuit contains 200 a three-phase bridge circuit, each phase of which is equipped with a pair of power semiconductor devices (switching elements). 211a until 211f) is equipped to provide power, and the control circuit 200 forms a power converter that uses the power supplied by the onboard power supply 230 converts the supplied DC power into AC power in order to supply the AC power to the brushless motor 112to provide. Although in this example each switching element 211a until 211f While the circuit is formed by an insulated-gate bipolar transistor (IGBT), other semiconductor devices such as field-effect transistors (FETs) can be used to control electrical power. Between the collector and emitter of each IGBT are the cathode and anode of a corresponding diode. 212a until 212f connected in such a way that the direction of power input is reversed.

[0030] The control unit 300 supplies the control port (gate port) of each switching element. 211a until 211f with the corresponding gate voltage From , Vvv , VW , to the switching element 211a until 211f , which is to be switched on or off, to be selectively controlled, and thereby three-phase connection voltages are From , Vvd , VWfor controlling the brushless motor 112 generated. At a time when these voltage pulses generate a voltage VB of the onboard power supply. 230 will then be determined by the shunt resistance 220 The phase current flowing through the three-phase bridge circuit is detected, and the measured value of the three-phase current is sent to the control unit. 300 delivered.

[0031] Fig. 4 is a function block diagram that shows an example of one controlled by the control unit 300 The control process is illustrated. Conventionally, based on an actuator command angle and an actuator angle (measured value), position control (model reference control) is performed to obtain a q-axis voltage, and this voltage is converted into a current to generate a q-axis current command in order to perform q-axis current feedback in a vector control.

[0032] In contrast, according to the present embodiment, when the voltage pulse width in the corresponding control wire 210u , 210v , 210w of the brushless motor 112 If the voltage pulse width is greater than a predetermined value, the pulse shift is performed; whereas if the voltage pulse width is less than the predetermined value, the pulse shift is not performed. Since the phase current cannot be measured if the pulse shift is not performed, the q-axis voltage of the position control is used as is to achieve control that does not require the current.

[0033] The control unit 300 It therefore contains a position feedback (F / B) control unit 310, which outputs a q-axis voltage. The position feedback control unit 310 calculates the q-axis voltage based on the command angle of the electrical actuator. 102and the measured actuator angle to the control shaft 36 in the mechanism 100 to control a variable compression ratio. By using this q-axis voltage, the current top dead center position becomes the target top dead center position of the piston. 12 feedback to the model reference control for setting a manipulated amount of the electric actuator 102 (brushless motor) 112 to carry out.

[0034] The position feedback control unit 310 The output q-axis voltage is transferred to a first fixed contact of a switching unit. 320 fed in. Furthermore, the q-axis voltage is fed into an adder. 330 A decoupling term is fed in, which is calculated by a unit that calculates decoupling terms. 340 The output is added to the q-axis voltage, and the result is fed into a second fixed contact of the switching unit. 320fed in. The switching unit 320 is controlled by a switching signal so that one of the outputs of the position feedback control unit 310 and the output of the adder 330 The switching signal is a signal that represents whether the pulse width of the three-phase supply voltage is selected. From , Vvd , VW in the control wire 210u , 210v , 210w of the brushless motor 112 greater (or smaller) than the predetermined value.

[0035] A d-axis current command is sent to a unit 350 Supplied for d-axis current control and calculation of decoupling terms. Since this d-axis current command is a reactive current component, the d-axis current command is controlled to 0 A; however, if a weak magnetic field is applied, the d-axis current command is controlled to -20 A. To the unit 350For d-axis current control and calculation of decoupling terms, a d-axis current and a q-axis current are used, which are generated by a converter. 360 The unit is delivered and outputs data from three phases across two axes. 350 For d-axis current control and calculation of decoupling terms, a d-axis voltage is calculated based on the d-axis current command, the d-axis current and the q-axis current, and the d-axis voltage is corrected by adding the decoupling term.

[0036] A switching unit 370 It has a first fixed contact to which a voltage of 0 V is applied, and a second fixed contact to which the output of the unit is applied. 350 It is supplied for d-axis current control and calculation of decoupling terms. The switching unit 370 is controlled by a switching signal such that one of 0 V and the output of the unit 350is selected for d-axis current control and calculation of decoupling terms. The switching unit 320 supplied q-axis voltage and that supplied by the switching unit 370 The supplied d-axis voltage is both transferred to a converter. 380 Provided by two axes in three phases. The converter 380 The conversion from two axes to three phases is based on a motor angle and performs a conversion from two axes to three phases in order to derive gate voltages from the q-axis and d-axis voltages. From , Vvv , VW to produce.

[0037] The one in the converter 380 Gate voltages generated by two axes in three phases From , Vvv , VW a first fixed contact of a switching unit 390 provided and are also used in a momentum shift processing unit 400 provided, and then tensions will be released. From' , Vv' , Wow, which were subjected to pulse shift processing, a second fixed contact of a switching unit 390 provided. The switching unit 390 is controlled by a switching signal such that one of the gate voltages From , Vvv , VW and gate voltages From' , Vv' , Wow is selected.

[0038] The signal of a current rotation angle (sensor output for measuring the motor angle), which is generated by the rotation angle sensor 108 measured current rotation angle of the brushless motor 112 specified is converted into a unit 410 A signal is fed in to calculate a BLM angle and angular velocity, thereby calculating a motor angle and motor angular velocity. The calculated motor angle is then sent to the converter. 360 of three phases in two axes and the converter 380supplied by two axes in three phases, and the calculated motor angular velocity is fed to the decoupling term calculating unit 340 delivered. The converter 360 of three phases in two axes leads based on the unit 410 The calculated motor angle and the measured value of the three-phase current through the shunt resistance are used to calculate the BLM angle and angular velocity. 220 The measurement showed a conversion of three phases into two axes to generate the d-axis current and the q-axis current.

[0039] The generated d-axis current is used in the unit calculating the decoupling terms. 340 and the unity 350 for d-axis current control and calculation of decoupling terms, and the generated q-axis current is fed into the unit 350 The data is used for d-axis current control and the calculation of decoupling terms. The unit calculating the decoupling terms...340 It calculates the decoupling term, and the decoupling term is added to a voltage obtained in the control system at a higher level (i.e., to the output of the position feedback control unit). 310 added) to generate the q-axis voltage.

[0040] In Fig. 4 corresponds to the one marked by a dashed line. 420 surrounding area of ​​a conventional vector control unit.

[0041] In the configuration as described above, if the pulse width of the three-phase connection voltage From , Vdd, Vwd in the control wire 210u , 210v , 210w of the brushless motor 112 If the pulse width is greater than the predetermined value, the pulse shift is performed, whereas if the pulse width is less than the predetermined value, the pulse shift is not performed. Case 1

[0042] A case is described in which pulse shifting is performed. With respect to the q-axis voltage, the switching signal causes a movable contact of the switching unit to move. 320 connects to the first fixed contact, so that the output of the position feedback control unit 310 The q-axis current feedback is selected and performed. Regarding the d-axis voltage, a movable contact of the switching unit is activated. 370 connects to the second fixed contact, so that the output of the unit 350 The following is selected for d-axis current control and calculation of decoupling terms. The resulting q-axis and d-axis voltages are then fed to the converter. 380 provided by two axes in three phases to generate gate voltages From , Vvv , VW to generate, and the generated gate voltages From , Vvv , VWbecome the momentum shift processing unit 400 provided. Moreover, the switching signal causes a movable contact in the switching unit to move. 390 connects to the second fixed contact, so that the output of the pulse shift processing unit 400 selected and tensions From' , Vv' , Wow , which were subjected to pulse shift processing, via the corresponding control wires 210u , 210v , 210w to the coils 114u , 114v or 114w of the brushless motor 112 will be delivered.

[0043] Next, a case is described in which the pulse shift is not performed. With respect to the q-axis voltage, the switching signal causes the movable contact of the switching unit to move. 320connects to the first fixed contact, so that an output from the position feedback control unit 310 The q-axis current feedback is selected and performed. Regarding the d-axis voltage, the movable contact of the switching unit is activated. 370 connects to the first fixed contact so that 0 V is supplied as the d-axis voltage. The resulting q-axis and d-axis voltages are then sent to the converter. 380 provided by two axes in three phases to generate gate voltages From , Vvv , VW to generate. Then, the switching signal causes the movable contact of the switching unit to... 390 connects to the first fixed contact, so that the output of the converter 380 selected from two axes in three phases, and the generated gate voltages From , Vvv , VW via the corresponding control wires 210u , 210v , 210w to the coils114u , 114v or 114w of the brushless motor 112 will be delivered.

[0044] Therefore, in this case 1 During the pulse shift, the q-axis voltage is changed back to the present value to obtain the q-axis current, and thus the q-axis current feedback is performed in the vector control. Case 2

[0045] This describes a case in which pulse shifting is performed. With respect to the q-axis voltage, the switching signal causes the movable contact of the switching unit to move. 320 connects to the second fixed contact, so that the output of the adder 330 The voltage is selected, and thus the voltage obtained by adding the q-axis voltage of the reference model and the decoupling term is selected. Regarding the d-axis voltage, the movable contact of the switching unit is caused to... 370connects to the second fixed contact, so that the output of the unit 350 The following is selected for d-axis current control and calculation of decoupling terms. The resulting q-axis and d-axis voltages are then fed to the converter. 380 provided by two axes in three phases to generate gate voltages From , Vvv , VW to generate, and the generated gate voltages From , Vvv , VW become the momentum shift processing unit 400 provided. The switching signal then causes the movable contact of the switching unit to open. 390 connects to the second fixed contact, so that the output of the pulse shift processing unit 400 selected and tensions From' , Vv' , Wow , which were subjected to pulse shift processing, via the corresponding control wires 210u , 210v , 210w to the coils114u , 114v or 114w of the brushless motor 112 will be delivered.

[0046] Next, a case is described in which the pulse shift is not performed. With respect to the q-axis voltage, the switching signal causes the movable contact of the switching unit to move. 320 connects to the second fixed contact, so that the output of the adder 330 The voltage is selected, and thus the voltage obtained by adding the q-axis voltage of the reference model and the decoupling term is selected. Regarding the d-axis voltage, the movable contact of the switching unit is caused to... 370 connects to the first fixed contact so that 0 V is supplied as the d-axis voltage. The resulting q-axis and d-axis voltages are then sent to the converter. 380 provided by two axes in three phases to generate gate voltages From , Vvv , VWto generate. Then, the switching signal causes the movable contact of the switching unit to... 390 connects to the first fixed contact, so that the output of the converter 380 is selected from two axes in three phases and the generated gate voltages From , Vvv , VW via the corresponding control wires 210u , 210v , 210w to the coils 114u , 114v or 114w of the brushless motor 112 will be delivered.

[0047] Regardless of the presence or absence of the pulse shift, the q-axis current feedback is therefore not performed, and accordingly, the control is always carried out using the q-axis voltage as it is.

[0048] Fig. Figure 5 illustrates a flowchart to explain a control method for a brushless motor according to an embodiment of the present invention. Fig. Section 5 describes a procedure for measuring the phase current in the single-shunt system. First, the pulse width of the voltage is determined. From , Vvv , VW in a control wire 210u , 210v , 210w of the brushless motor 112 measured (step S1 Next, the measured voltage pulse width and the predetermined value, previously stored in a memory unit of the VCR controller, are used. 110 (or alternatively, the main controller) 42 ) was saved, compared (step S2 ).

[0049] If the measured voltage pulse width is greater than the predetermined value, will the brushless motor then 112 controlled, whereby the pulse shift is performed (step S3 ), whereas if the measured voltage pulse width is less than the predetermined value, the brushless motor 112is controlled without performing the pulse shift (step S4 Since the phase current cannot be measured if the pulse shift is not performed as described above, at this time the control which does not require the current is executed by using the q-axis voltage of the position control as it is.

[0050] As described above, in the present embodiment the vector control, in which the d-axis and q-axis currents are both controlled, is not performed, and the q-axis voltage is determined based on the voltage supplied by the main controller. 42 was obtained at the higher level. Regarding the q-axis current, if the pulse width is applied to the brushless motor 112If the applied voltage is low (the duty cycle is low), the current measurement is not performed, and the d-axis voltage is set to 0 [V], whereas if the duty cycle is not low, the current measurement is performed to carry out the current control.

[0051] Even if a damped oscillation occurs in the phase current at the time the voltage pulse is applied in the single-shunt system, it is possible to perform the current measurement at the point when the damped oscillation is stopped by the pulse-shift processing, thus enabling the acquisition of the precise current value sufficient for use in vector control. Conversely, if the voltage pulse width is smaller than the predetermined value, it is possible to reduce noise by eliminating the pulse shift.

[0052] Fig. 6A to Fig.Figures 6C are waveform diagrams, each illustrating the acquisition of phase current information when pulse-shift processing is performed. As in Fig. As illustrated in the 6A diagram, current flows when a desired pulse voltage width (= duty cycle) is reached. ΔD1 is small, the phase current through the shunt resistor 220 only in a short time, and thus the phase current information is strongly influenced by the damped oscillation, resulting in a decrease in the measurement accuracy of the phase current.

[0053] As in Fig. As illustrated in Figure 6B, a voltage pulse with the smallest possible duty cycle is therefore applied first. ΔD2 , to reliably detect the phase current, applied to detect the phase current, and then a voltage pulse with a corrected duty cycle is used as the second voltage pulse. ΔD3Applied (a voltage pulse in a counter-torque direction can occur in some cases), without capturing phase current information. In this case, the corrected duty cycle is ΔD3 “ΔD3 = 2 x ΔD1 - ΔD2”.

[0054] Fig. 6C is an enlarged view illustrating the area that is in Fig. 6B is surrounded by a dashed line. The phase current information is acquired during the first voltage pulse after the damped oscillation stops. Since the second voltage pulse is affected by the damped oscillation, no phase current information is acquired. Consequently, a desired duty cycle can be set. ΔD1 this can be achieved by averaging two successively applied voltage pulses.

[0055] Fig. Figure 7 is a waveform diagram illustrating the V-phase current and the U-phase current when the momentum shift is performed, and Fig.Figure 8 is a waveform diagram illustrating the V-phase current and the U-phase current when the momentum shift is not performed. As in Fig. As illustrated in Figure 7, this occurs when the duty cycle of the brushless motor 112 When the applied voltage is low (low voltage), current oscillation occurs due to pulse shifting, generating buzzing noise. However, since pulse shifting is not performed, the current oscillation can be reduced during constant-angle control, thus reducing the noise, as shown in Fig. Figure 8 illustrates this.

[0056] The present invention is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the invention. Modification 1

[0057] For example, although the state in which the phase shift is performed and the state in which the phase shift is not performed can be based on the pulse width of the three-phase supply voltage From , Vvd , VW in the control wire 210u , 210v , 210w of the brushless motor 112 In the above embodiment, switching is performed by a signal according to the operating requirements of the electrical actuator. 102 can be controlled.

[0058] Furthermore, the state in which the pulse shift is performed and the state in which the pulse shift is not performed can be determined based on a comparison of a deviation between a position command value and a sensed position of the electrical actuator. 102The switching can be performed using a predetermined value, or the state in which the pulse shift is performed and the state in which the pulse shift is not performed can be switched based on an instruction value and a current value of the machine's compression ratio. Furthermore, switching can be performed based on a combination of these values. Modification 2

[0059] Additionally, the state in which the d-axis and q-axis current controls are performed, and the state in which the d-axis and q-axis current controls are not performed, can be switched based on whether the pulse shift is performed or not, and the d-axis current control is not performed if the d-axis voltage is less than or equal to a predetermined value. Modification 3

[0060] Furthermore, in a case where control is performed in a weak field, when the command value of the d-axis current becomes 0 A, the d-axis current control can be switched from a state in which it is performed to a state in which it is not performed. Modification 4

[0061] As switching conditions of the d-axis voltage in a case where the pulse shift is switched to the state in which it is not performed during an execution of the pulse shift, in addition to the conditions above, the d-axis voltage is switched to 0 V when the d-axis voltage becomes 0 V or the polarity is changed.

[0062] Alternatively, since a situation may arise where the command value of the d-axis current is 0 A, or the command under a weak field during the pulse shift sets the d-axis current to one other than 0 A (although the d-axis current is generally set to 0 A), the pulse shift can be switched to the state in which it is not performed when the d-axis current returns to 0 A. Reference symbol list 10 machine 42 Main Controllers 100 Mechanism for a variable compression ratio 102 electric actuator 108 Rotation angle sensor 110 VCR controllers 112 brushless motor 114u, 114v, 114w coils 200 control circuit 210u, 210v, 210w control wires 211a-211f Switching elements 220 shunt resistor 230 onboard power supply 300 control unit Vu, Vv, Vw gate voltages Vud, Vvd, Vwd Three-phase connection voltages 310 Position feedback control unit 320 switching unit 330 Adders 340 decoupling terms calculating unit 350 units for d-axis current control and calculation of decoupling terms 360° converter of three phases in two axes 370 switching unit 380 converters of two axes in three phases 390 switching unit 400 Impulse Shift Processing Unit 410 Unit for calculating a BLM angle and an angular velocity QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 2010 / 103565

[0005]

Claims

[1] Control device for a brushless three-phase motor, comprising: a shunt resistor for measuring a phase current of the brushless motor; and a controller that measures the phase current of the brushless motor in a single-shunt system using the shunt resistor and controls the driving of the brushless motor based on the measured phase current, wherein the controller performs a pulse shift when a voltage pulse width in a drive wire of the brushless motor is greater than a predetermined value, whereas the controller does not perform the pulse shift when the voltage pulse width is less than the predetermined value. [2] Control device for the brushless motor according to claim 1, wherein the controller comprises a control circuit that controls the brushless motor and a control unit that controls the control unit. [3] Control device for the brushless motor according to claim 2, wherein the control circuit comprises a three-phase bridge circuit, each phase of which is provided with a pair of switching elements, wherein the control circuit converts a DC power supplied by a power supply into an AC power in order to provide the AC power to the brushless motor. [4] Control device for the brushless motor according to claim 3, wherein the shunt resistor is connected between the three-phase bridge circuit and the power supply. [5] Control device for the brushless motor according to claim 4, wherein the control unit performs a current measurement using the shunt resistor when the voltage pulse is applied to the brushless motor. [6] Control device for the brushless motor according to claim 2, wherein the control unit includes a pulse shift processing unit which performs pulse shift processing, wherein the pulse shift processing unit corrects a voltage during a monotonically increasing period of a triangular wave carrier and subtracts the correction amount from the corrected voltage during a monotonically decreasing period following the monotonically increasing period, so that an averaged voltage becomes zero. [7] Control device for the brushless motor according to claim 1, wherein the brushless motor is a power source of an electric actuator for use in a machine and switches between a state in which the pulse shift is performed and a state in which the pulse shift is not performed, based on an operating requirement of the electric actuator. [8] Control device for the brushless motor according to claim 7, wherein the electric actuator is used for use in the machine for a mechanism for varying a compression ratio of a variable compression ratio machine. [9] Control device for the brushless motor according to claim 8, wherein the control unit controls the control circuit based on the compression ratio of the variable compression ratio machine to switch between the state in which the pulse shift is performed and the state in which the pulse shift is not performed. [10] Control device for the brushless motor according to claim 7, wherein the control unit controls the control circuit based on a comparison of a deviation between a position command value and a sensed position of the electric actuator with a predetermined value in order to switch between the state in which the pulse shift is performed and the state in which the pulse shift is not performed. [11] Control device for the brushless motor according to claim 1, wherein the control unit switches between a state in which d-axis and q-axis current controls are performed and a state in which the d-axis and q-axis current controls are not performed, based on whether the pulse shift is performed or not. [12] Control device for the brushless motor according to claim 11, wherein the control unit does not allow the d-axis current control to be carried out if a d-axis voltage is less than or equal to a predetermined value. [13] Control device for the brushless motor according to claim 11, wherein in a case where control is carried out in a weak field, the control unit switches from a state in which the d-axis current control is carried out to a state in which the d-axis current control is not carried out when a command value of the d-axis current becomes 0 A. [14] Control device for the brushless motor according to claim 1, wherein the control unit generates a q-axis voltage by adding a decoupling term to a voltage obtained in a control in a system of a higher level. [15] Method for controlling a brushless three-phase motor by measuring a phase current in a single-shunt system, the method comprising the steps: Measuring a voltage pulse width in a control wire of the brushless motor; Comparing the measured voltage pulse width with a predetermined value; and Performing a pulse shift if the measured voltage pulse width is greater than the predetermined value, whereas the pulse shift is not performed if the measured voltage pulse width is less than the predetermined value. [16] Method for controlling the brushless motor according to claim 15, wherein performing the pulse shift comprises correcting a voltage during a monotonically increasing period of a triangular wave carrier, subtracting the correction amount from the corrected voltage during a monotonically decreasing period following the monotonically increasing period, so that an averaged voltage becomes zero, in order to perform a current measurement. [17] Method for controlling the brushless motor according to claim 15, wherein comparing the measured voltage pulse width with the predetermined value comprises comparing the measured voltage pulse width with a predetermined value that was previously stored in a storage unit. [18] Method for controlling the brushless motor according to claim 15, wherein the brushless motor is a power source of an electric actuator for use in a machine and switches between a state in which the pulse shift is performed and a state in which the pulse shift is not performed, based on an operating requirement of the electric actuator. [19] Method for controlling the brushless motor according to claim 18, wherein the electric actuator is used for use in the machine for a mechanism for varying a compression ratio of a variable compression ratio machine. [20] Method for controlling the brushless motor according to claim 19, wherein the state in which the pulse shift is performed and the state in which the pulse shift is not performed are switched based on the compression ratio of the variable compression ratio machine.

Images