JP7729265B2 - Motor control device - Google Patents

Description

The present invention relates to a device that controls a motor using a position sensorless method.

When controlling a motor using a position sensorless method, the rotor positioning required to start the motor involves fixing the current flowing through a drive circuit such as an inverter in a specific direction. For example, for motors that start and stop frequently, positioning is required more frequently. Therefore, if positioning is performed using the same current flow pattern every time, stress caused by the current flowing through the circuit elements and motor windings will be placed on them.

For example, Patent Document 1 discloses a technology for dispersing current stress by circulating current between the inverter's high-side switches or low-side switches and the motor windings.

Japanese Patent Application Laid-Open No. 2007-221969

However, the technology in Patent Document 1 only has two current-carrying patterns, so it cannot be said that the current stress is sufficiently distributed.

The present invention was made in consideration of the above circumstances, and its purpose is to provide a motor control device that can better distribute current stress when performing positioning at startup using a position sensorless method.

According to the motor control device of claim 1, when controlling the motor using a position sensorless method by energizing the polyphase motor via an inverter circuit, the control unit changes the energization pattern used for positioning the motor rotor to three or more types. This configuration allows current stress to be distributed more effectively than in the past. Furthermore, while Patent Document 1 distributes current stress in response to rare overcurrent occurrences, the present invention distributes current stress each time rotor positioning is performed. In other words, current stress can be distributed within the period during which the motor is normally controlled.
The control unit also counts the number of times current is applied to the motor using the counter, and switches the order in which the current application pattern is changed depending on the counted value. With this configuration, it is possible to distribute the current stress in a more diverse manner.
Furthermore, the polyphase motor is mounted on a vehicle, and the counting unit can select whether or not to add the number of times that current is applied during a period when the ignition switch is turned off to the number of times that current is applied during a period when the ignition switch is turned on.

According to the motor control device described in claim 2, the control unit stores the current conduction pattern used in the previous positioning process in the memory unit, and changes the current conduction pattern each time positioning is performed. This configuration makes it possible to more reliably distribute current stress.

FIG. 1 is a functional block diagram illustrating a configuration of a motor control system according to a first embodiment. Functional block diagram showing the internal configuration of the IC FIG. 1 is a diagram showing a schematic configuration of a stator and a rotor of a motor; A diagram showing current vectors corresponding to current conduction patterns A to C. Flowchart showing the processing contents by IC 10 is a flowchart showing the processing performed by an IC according to a second embodiment. Timing chart corresponding to the process shown in FIG. 6 10 is a flowchart showing the processing performed by an IC according to a third embodiment. 10 is a flowchart showing the processing performed by an IC according to a fourth embodiment. FIG. 10 is a functional block diagram showing the internal configuration of an IC according to a fifth embodiment. Flowchart showing the processing contents by IC

(First embodiment)
A first embodiment will now be described. As shown in FIG. 1 , a motor control system 1 of this embodiment controls, for example, a motor 2 that drives a fan for cooling a radiator mounted on a vehicle. A drive circuit 3 includes an inverter 4 and an IC 5. The drive circuit 3 is supplied with power from a power source +B, which is the vehicle's battery power source, and power source IGS via an ignition switch. Hereinafter, the ignition switch may also be referred to as "IGS." The IC 5 corresponds to a control unit and performs position sensorless control of the motor 2 via the inverter 4. Although not shown, the inverter 4, which is an inverter circuit, is configured by connecting six switching elements, such as MOSFETs, in a three-phase bridge configuration.

As shown in Figure 2, IC5 includes counter 6, which counts the number of times that current is applied to motor 2 while the IGS is OFF, and counter 7, which counts the number of times that current is applied while the IGS is ON. The count values of counters 6 and 7 are stored in memory 10 via adder 8 and current application count memory execution unit 9. Memory 10 corresponds to the storage unit. Motor 2 is, for example, a three-phase brushless DC motor. When starting motor 2 that has stopped, IC5 performs rotor positioning processing before starting it. Current pattern No. calculation unit 12 calculates and determines the three-phase current pattern for applying current to inverter 4 when performing positioning processing.

The previous pattern readout unit 11 stores the current conduction pattern determined by the current conduction pattern number calculation unit 12 in memory 10, and also reads the number of current conductions and the current conduction pattern used in the previous positioning process stored in memory 10, and inputs them to the current conduction pattern number calculation unit 12. The current conduction pattern number calculation unit 12 determines the current conduction pattern to be used in the current positioning process based on the input information, and outputs drive signals to each of the six switching elements that make up the inverter 4 via the current conduction instruction unit 13. Note that the number of current conductions described above is not used in this embodiment, but is used in the second and subsequent embodiments.

In this embodiment, three current conduction patterns A, B, and C are used for positioning processing, as shown in Figures 3 and 4. Figure 3 shows a schematic diagram of the stator and rotor of the motor 2. In Figure 4, each current conduction pattern is shown as a current vector. "a" in the figure is the unit length of the vector. The current vectors for each current conduction pattern are as follows:
U phase V phase W phase Current conduction pattern A a -4a 3a
・Current pattern B 4a -a -3a
・Current pattern C -3a 4a a
That is, the composite current vector of the current conduction patterns A, B, and C has a relationship in which it transitions so as to rotate at intervals of 120 degrees.

Next, the operation of this embodiment will be described. As shown in FIG. 5, IC5 reads from memory 10 the energization pattern used in the previous positioning process (S0), and then determines the energization pattern to be used in the current positioning process in the following steps S1 to S5. The order in which the energization patterns are used is fixed in advance and changes cyclically as follows: A → B → C → A → B... In other words, if the previous energization pattern was A (S1; Yes), the current energization pattern is set to B (S2); if the previous energization pattern was B (S3; Yes), the current energization pattern is set to C (S4); and if the previous energization pattern was C (S3; No), the current energization pattern is set to A (S5).

Once the current conduction pattern has been determined in this manner, it is stored in memory 10 (S6). Then, the target switching element, such as an FET, is turned ON in accordance with the determined conduction pattern to perform positioning processing (S7). If an abnormality occurs thereafter such that motor 2 rotation stops (S8), motor 2 is restarted (S9; Yes) and then normal motor 2 control is resumed (S10). If restart cannot be performed (S9; No), it is determined that restart is not possible (S11).

As described above, according to this embodiment, in the motor control system 1, the IC 5 applies current to the motor 2 via the inverter 4, changing the current pattern used for positioning the rotor of the motor 2 between three different patterns when controlling the motor using a position sensorless method. This configuration allows the current stress applied to the switching elements that make up the inverter 4 and the windings of the motor 2 to be more dispersed than in the past. Furthermore, in this embodiment, the current stress is dispersed each time the rotor positioning process is performed. In other words, the current stress can be dispersed during the period when the motor 2 is normally controlled, rather than only when an overcurrent occurs, as in Patent Document 1.

The IC5 then stores the current conduction pattern used in the previous positioning process in memory 10, and changes the current conduction pattern each time positioning is performed. This configuration makes it possible to more reliably distribute current stress.

Second Embodiment
Hereinafter, the same parts as those in the first embodiment are denoted by the same reference numerals and their description will be omitted, and only differences will be described. As shown in Fig. 6 , in the second embodiment, the number of times that the motor 2 is energized is counted, and the order in which the energization patterns A, B, and C are switched is changed depending on the number of times that the motor 2 is energized. As shown in Fig. 7 , a counter 6 counts the number of times that the motor 2 is energized while the IGS is OFF, and a counter 7 counts the number of times that the IGS is energized while the IGS is ON. The motor 2, which drives the fan for cooling the radiator, may be energized from the +B power supply even while the IGS is OFF if it is necessary to cool the engine, which is at a high temperature, such as immediately after stopping driving.

The number of energizations varies depending on how the count values of counters 6 and 7, which are the counting unit, are used. In the second embodiment, the number of energizations during the IGS OFF and ON periods is totaled, and the number of energizations before the IGS was turned ON this time is not stored. In this case, in the example shown in Figure 7, the number of consecutive energizations at the previous startup is "4," and the number of energizations at the current startup is "2."

In Figure 7, in steps S21 to S26 following step S0, the total number of energizations is compared with the respective thresholds (1) to (3) to (6). Note that some steps have been omitted for ease of illustration. For example, the thresholds (1) to (6) are set so that their values gradually increase. If the total number of energizations is less than threshold (1) (S21; No), steps S1 to S5 are executed as in the first embodiment. This is referred to as "combination 1." If the total number of energizations is less than threshold (2) (S22; No), steps S27 to S31 are executed. This is a pattern in which steps S4 and S5 of the above "combination 1" are swapped, and is referred to as "combination 2."

If the total number of energizations is less than threshold value (3) (S23; No), "Combination 3" (S32) is executed. Similarly, if the total number of energizations is less than threshold values (4) to (6) (S24-S26; No), "Combinations 4 to 6" are executed (S33-S35). In other words, the "combinations" are permutations of 3P2, for a total of six combinations. From then on, steps S6 to S11 are executed, as in the first embodiment. Note that the difference between threshold values (1) to (6) may be "2" or more. Alternatively, the number of energizations before the IGS was turned on this time may be stored, and the number of energizations since the current startup may be added to that number.

As described above, according to the second embodiment, IC 5 counts the number of times current is applied to motor 2 using counters 6 and 7, and switches the order in which the current pattern is changed depending on the counted value. This configuration allows current stress to be distributed in a more diverse manner.

(Third embodiment)
8, in the third embodiment, the current supply pattern No. to be used is determined as the remainder when the cumulative number of times the motor 2 is energized while the IGS is ON is used as the "current supply number," and the "current supply number" is divided by the number of current supply patterns, "3" (S41). In other words, the current supply pattern No. will be either "0, 1, or 2," and current supply patterns A, B, or C are selected in accordance with the corresponding current supply pattern No. in step S41.

As described above, according to the third embodiment, the current pattern No. to be used is determined using only the cumulative number of times the motor 2 is energized while the IGS is ON as the "current count," so the capacity of the memory 10 that stores the current count can be reduced compared to the second embodiment.

(Fourth embodiment)
9, in the fourth embodiment, when step S0 is executed, the values of each digit when the number of times the IGS is energized during its ON period is expressed in decimal notation is summed, and when this sum is divided by "3", which is the number of phases of the motor 2, it is determined whether the remainder is "0" (S50). If the remainder is "0" (Yes), steps S1 to S11 are executed as in the first embodiment. On the other hand, if the remainder is not "0" (No), steps S51 to S55 are executed, and then the process proceeds to step S6.

The energization patterns -B, -C, and -A shown in steps S52 to S55 are obtained by inverting the polarity of the phase current vectors of energization patterns B, C, and A shown in Figure 4. Note that energization patterns A to C correspond to the non-inverted pattern group, and energization patterns -A to -C correspond to the inverted pattern group. If the previous energization pattern was A or -A (S51; Yes), the current energization pattern is set to -B (S52). If the previous energization pattern was B or -B (S53; Yes), the current energization pattern is set to -C (S54). If the previous energization pattern was C or -C (S53; No), the current energization pattern is set to -A (S55).

As described above, according to the fourth embodiment, IC5 selects whether to use the non-inversion pattern group or the inversion pattern group depending on whether the remainder obtained by dividing the number of times current is applied to motor 2, counted by counter 7, by the number of phases of motor 2 is zero. This configuration makes it easy to increase the number of variations in current application patterns, further distributing current stress.

Fifth Embodiment
In the fifth embodiment, IC21 shown in Fig. 10 is used instead of IC5. IC21 includes circuits 22(0) to 22(2) that generate binary numeric data "00,""01," and "10," respectively, when power supply +B is energized (Fig. 11; S60). These circuits 22 are configured by combining logic circuits such as AND and OR.

A random function is also implemented using software, and the above numerical data "00," "01," and "10" are input into the random function (S62), and one of the numerical data is selected by the random function. The selected numerical data is set as the current conduction pattern No., and is designated as the current conduction pattern to be used (S63).

In step S61, the numerical data generated by circuits 22(0) to 22(2) is stored. In this case, the data may be stored in memory 10, or each of the blocks "Output: 00" to "Output: 10" shown in FIG. 10 may be used as a memory or register and the data may be stored in those blocks.
As described above, according to the fifth embodiment, the current pattern to be used can be selected randomly using a random function. Note that IC5 may be provided with the same functions as IC21.

(Other embodiments)
The number of phases of the motor is not limited to "3".
The current conduction patterns are not limited to three types, A, B, and C, and four or more types may be used.
The load driven by the motor is not limited to a radiator cooling fan.
Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

In the drawing, 1 represents the motor control system, 2 represents the motor, 4 represents the inverter, 5 represents the IC, 6 and 7 represent counters, and 10 represents memory.

Claims (4)

By energizing the polyphase motor (2) via an inverter circuit (4), the motor is controlled by a position sensorless method;
a control unit (5, 21) for changing the energization pattern used in the positioning process of the rotor of the motor into three or more types ;
The control unit (5) includes a counting unit (6, 7) that counts the number of times the motor is energized,
switching the order in which the current conduction pattern is changed according to the value counted by the counting unit;
The polyphase motor is mounted on a vehicle,
The counting unit is capable of counting by selecting whether or not to add the number of times that an ignition switch is turned off to the number of times that an ignition switch is turned on . The control unit includes a storage unit (10) that stores the current pattern used in the previous positioning process,
2. The motor control device according to claim 1, wherein the current conduction pattern is changed every time the positioning process is performed. The three or more types of current conduction patterns include a non-reversal pattern group in which the current conduction state for each phase is determined;
3. The motor control device according to claim 1, further comprising an inversion pattern group in which the polarity of the non-inversion pattern group is inverted to that of the phases. the control unit includes a counting unit that counts the number of times that the motor is energized,
4. The motor control device according to claim 3, wherein the motor control device selects whether to use the non-inversion pattern group or the inversion pattern group depending on whether a remainder obtained by dividing the value counted by the counting unit by the number of phases of the motor is zero or not.