Motor actuation control device

A triangle wave generator (4) measures the phase difference between a triangle wave (CA) and the rotor electrical angle (θm) during a first cycle in which the rotation rate of a rotor (7) is detected, and changes the frequency of the triangle wave (CA) when the value of the phase difference between the triangle wave (CA) and the rotor electrical angle (θm) exceeds a threshold value, thereby allowing rapid response to changes in rotor rotation when PWM control is performed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a motor actuation control device, and particularly to a motor actuation control device which is capable of steadily controlling a motor even during rapid changes in the rotation rate of the rotor.

2. Description of the Related Art

In most motor vehicles, including electric vehicles and hybrid vehicles, a direct current power source such as a battery is provided, and an alternating current motor is provided as a power source. In addition, an inverter is provided between the direct current power source and the alternating current motor to convert the direct current power to the alternating current power.

PMW (pulse width modulation) control is a known technique for controlling the alternating current motor via inverters. PWM control is one type of voltage conversion control techniques for voltage type inverters, in which a pulse signal called a PWM signal is supplied to a switching element provided in the inverter to control on/off timing of the switching element. By adjusting the on/off timing of the switching element, it is possible to control the voltage applied to the motor.

PWM signals are generated through a triangle wave comparison method. Specifically, a command signal which determines a voltage value to be applied to the motor is compared to a voltage value of a triangle wave which is also called a carrier wave to generate a PWM signal.

The voltage value of the command signal is determined continuously based on a rotor electrical angle and a torque requirement value. The command signal generally has a sinusoidal waveform and the cycle of the command signal is increased or decreased according to changes of the torque requirement value and the rotation rate of the rotor when the synchronous motor, such as a permanent magnet motor, is used.

The triangle wave is generated through integration of clock signals. The frequency of the clock signals are set by a control unit or the like provided in the motor vehicle.

In generating the PWM signal, the number of pulses of the PWM signal provided during one cycle of the command signal is determined by the ratio of the frequency of the triangle wave to the frequency of the command signal. For example, if the ratio of the frequency of the triangle wave to the frequency of the command signal is 15, then fifteen pulses are provided in the PWM signal during one cycle of the command signal.

On the other hand, if the inverter turns on and off a great number of times within a short period of time, switching loss occurs and the switching element may as a result become overheated, which may lead to performance errors of the element. Measures to avoid overheating of the switching element, such as providing more than one switching element to disperse heat and prevent overheating, have been attempted, but, in order to reduce costs and for other reasons, modern inverters include fewer switching elements compared than earlier conventional inverters. Because the preventive measure noted above cannot be applied to such inverters, the number of pulses of the PWM signal during one cycle of the command signal must be set to a relatively small number.

However, when the number of pulses of the PWM signal during one cycle period of the command signal is set to a relatively small number, it is necessary to change the frequency of the clock signal in response to changes of the frequency of the command signal and maintain the number of pulses of the PWM signal during one cycle period of the command for the sake of the stable PWM control.

For example, if it is desired to increase the rotation rate of the rotor, the frequency of the command signal is increased as well. In contrast, if the frequency of the clock signal is fixed, the number of pulses of the PWM single during one cycle of the command signal is decreased.

If a relatively large number of pulses (e.g., 15-20 pulses) are included in the PWM signal during one cycle of the command signal, the influence of the decrease in the number of pulses may be small. On the other hand, however, if the number of pulses included in the PWM signal during one cycle of the command signal is relatively small (e.g., 5-10 pulses), the pulse number decrease gives a greater influence. In this case, as the number of pulses of the PWM signal during one cycle of the command signal is decreased, the inverter is not able to output an expected voltage as designated by the command signal. Eventually, a control failure, such as overload of the inverter, detuning of the motor, or the like, may occur

To deal with this problem, a control method has been known in which the frequency of the triangle wave is changed before rapid changes in the rotation rate (rpm) of the rotor and a change of the number of pulses of the PWM signal, while the number of pulses of the PWM signal is maintained at a fixed value. For example, Japanese Patent Laid-Open Publication No. 2007-159367 (Patent Document 1) discloses a technique in which the frequency of the triangle wave is raised when the increasing ratio of the rotation rate of the rotor exceeds a threshold value.Patent Document 1: Japanese Patent Laid-Open Publication No. 2007-159367

The rotation rate of the rotor is not calculated until after the rotor is rotated to some extent. Usually, the rotation rate of the rotor is calculated from the change of the electrical angle of the rotor during a predetermined time period while considering external factors, such as changes in the torque requirement value, the running resistance, etc. Because performing such calculation requires about 1 to 3 milliseconds, the frequency of the clock signal is adjusted about every 1 to 3 milliseconds.

On the other hand, the rotor electrical angle continuously increases and decreases in proportion to the rotation of the motor, particularly, for example, when road conditions cause tire slip to occur in a motor vehicle. This may cause the rotor electrical angle to change rapidly. In response, the frequency of the command signal may also change rapidly in less than 1 to 3 milliseconds, thereby increasing or decreasing the number of pulses of the PWM signal during one rotation of the rotor.

In consideration of the above, an object of the present invention is to enable rapid response to changes in the rotation of the motor when PWM control is performed.

SUMMARY OF THE INVENTION

A motor actuation control device according to the present invention includes a control unit which outputs a command signal and a triangle wave to generate a PWM signal, and an angle sensor which detects a rotor electrical angle. The control unit outputs the command signal by determining a voltage value of the command signal based on the rotor electrical angle and a torque requirement value. The control unit also calculates a rotation rate of the rotor for a first cycle based on the rotor electrical angle, and determines the frequency of the triangle wave for the first cycle based on the rotor rotation rate to output the triangle wave. Then, the control unit detects a phase difference between the triangle wave and the rotor electrical angle for a second cycle which is shorter than the first cycle, and changes the frequency of the triangle wave when the value of the phase difference between the phase angle of the triangle wave and the rotor electrical angle exceeds a predetermined threshold value.

In a motor actuation control device according to the present invention, the control unit stores the number of pulses to be output in the PWM signal during one cycle of the command signal as a designated pulse number. The control unit calculates a reference angle by multiplying the rotor electrical angle by the designated pulse number, detects the phase difference between the phase angle of the triangle wave and the reference angle, and changes the frequency of the triangle wave when the phase difference between the phase angle of the triangle wave and the reference angle exceeds a threshold value.

Also, in a motor actuation control device according to the present invention, the threshold value is set to ±180°.

With the present invention, it is possible to change the frequency of the triangle wave based on an instantaneous value for the rotor electrical angle. As a result, increase or decrease of the number of pulses of the PWM signal is reliably prevented, as compared to changing the frequency based on the information of the rotor rotation rate that is calculated through a certain time interval.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

FIG. 1is a schematic diagram showing a control unit1, a motor to be controlled2, and peripheral components thereof. In this embodiment, the motor2is a synchronous motor, such as an permanent magnet motor.

The configuration of the control unit1is explained below. The control unit1includes a command signal generating element3, a triangle wave generating element4, and a PWM control element5.

The command signal generating element3generates a command signal S and supplies it to the PWM control element5. The triangle wave generating element4generates a triangle wave CA and supplies it to the PWM control element5. The PWM control element5receives the command signal S and the triangle wave CA and generates a PWM signal PI. In the following description, operations, process steps, etc. to be carried out in each of the command signal generating element3, the triangle wave generating element4, and the PWM control element5are described in detail.

First, the command signal generating element3is explained. The command signal generating element3receives an electrical angle of a rotor7from a rotational angle sensor6, such as a resolver, and also receives a torque requirement value TR from a HV control module8. Then, the command signal generating element3generates a command signal S based on the received electrical angle θm and the torque requirement value TR. It is noted that a motor vehicle described in this embodiment is typically a hybrid vehicle, so that the HV control module8detects a depression amount of the accelerator pedal and calculates the torque requirement value TR to be transmitted to the motor2and the engine that is not shown.

The command signal generating element3calculates a voltage value Vsof the command signal S based on the signal representing the rotor electrical angle θmand the torque requirement value TR. The command signal S is sent to the PWM control element5. As the command signal generating element3continuously receives the rotor electrical angle θmand the torque requirement value TR, the voltage value Vsof the command signal S is also calculated continuously. Because the command signal S is output synchronously with the rotation of the rotor7, the cycle of the command signal S is substantially in tune with the cycle of the rotor electrical angle θm.

Next, the triangle wave generating element4is explained. The triangle wave generating element4includes a clock signal generator9which outputs a clock signal CLK. The triangle wave generating element4supplies the clock signal CLK to an integrating circuit to generate a triangle wave CA. The control unit1stores a designated pulse number Kpwhich is used to output the clock signal CLK. The designated pulse number Kpis the number of pulses to be generated in the PWM signal PI during the interval corresponding to one cycle of the command signal S. The designated pulse number Kpmay be preset in the control unit1, or otherwise be appropriately determined and by operators.

The triangle wave CA is generated as described below. The triangle wave generating element4receives the electrical angle of the rotor θmfrom the rotational angle sensor6. Further, the triangle wave generating element4measures values of the rotor electrical angle θmuntil the rotor7is rotated once, calculates a rotation rate Rmm (rpm) of the rotor when the rotor7is rotated once, and stores it. It takes about 1 to 3 milliseconds for one rotation of the rotor7. Therefore, the triangle wave generating element4calculates the rotation rate Rmm of the rotor for every 1 to 3 milliseconds and updates the stored rotation rate Rmm of the rotor.

Then, the triangle wave generating element4calculates a rotational frequency fm, of the rotor from the rotation rate Rmm of the rotor, and multiplies the frequency fm, the number of pole pairs of the rotor7, and the designated pulse number Kptogether to get a frequency fCLKof the clock signal. The clock signal CLK is integrated in the integrating circuit to generate the triangle wave CA which is then sent to the PWM control element5.

The PWM control element5compares the magnitude of the voltage value Vsof the command signal S to the voltage value VCAof the triangle wave CA, and generates the PWM signal PI, which is a pulse signal, based on the result of this comparison.

The PWM signal PI output from the PWM control element5is sent to an inverter10. In the inverter10, on/off control of the switching element is performed based on the PWM signal PI, such that the DC voltage applied to the inverter10is converted to an actuation voltage for actuating the motor2. The motor2works to generate torque corresponding to the torque requirement value TR from the HV control module8.

In the following, the motor actuation control carried out by the control unit1will be described with reference toFIGS. 2-9.

First Embodiment of the Motor Actuation Control

The control unit1calculates a phase difference between the rotor electrical angle θmand the phase angle θCAof the triangle wave CA, compares the phase difference with a predetermined threshold value and, when the phase difference exceeds the threshold value, determines that the rotation rate of the rotor7is rapidly changed, thereby changing the frequency of the triangle wave CA during one rotation of the rotor7. By such motor actuation control, the number of pulses of the PWM signal PI during one cycle of the command signal S is kept to the designated pulse number Kp. In the following, the motor actuation control according to this embodiment will be described in detail.

The triangle wave generating element4provided in the control unit1measures the phase difference between the rotor electrical angle θmand the phase angle θCAof the triangle wave CA at each predetermined measurement timing during one rotation of the rotor7.

FIG. 2shows the time varying phase shift of the rotor electrical angle θmand the phase angle θCAduring the cycle t1(sec) of the rotor electrical angle θm. Herein, the designated pulse number Kpis set to 6. In this embodiment, the measurement timing is when the phase angle θCAof the triangle wave is 0°. By setting the measurement timing as such, because θCA=0°, the phase difference Δθ between the rotor electrical angle θmand the phase angle θCAof the triangle wave CA equals to the rotor electrical angle θm, thereby facilitating the measurement. As shown inFIG. 2, the triangle wave generating element4samples values of the rotor electrical angle θmfor each cycle of the triangle wave CA. In the operation shown inFIG. 2, the rotor electrical angle θmis acquired five times from θm1to θm5, and the difference between each of these values and a threshold value is measured.

The triangle wave generating element4sets two kinds of threshold values consisting of an upper threshold value Thθm—UL and a lower threshold value Thθm—LL. The upper threshold value Thθm—UL and the lower threshold value Thθm—LL are set as described below.

For example, when the upper threshold value Thθm—UL and the lower threshold value Thθm—LL are set for the rotor electrical angle θm1when the triangle wave CA enters the second cycle, the upper and lower threshold values are calculated based on the conditions where the number of pulses output in the PWM signal PI during one cycle of the command signal S is greater or smaller than the designated pulse number Kp. For example, if the designated pulse number Kpis 6, the number of pulses output in the PWM signal PI during one cycle of the command signal S becomes a value other than 6 when the triangle wave CA has five or less or seven or more cycles during one cycle of the command signal S. Considering that the number of cycles of the command signal S is substantially the same as the number of cycles of the rotor electrical angle θmof the rotor7, the number of pulses of the PWM signal PI during one cycle of the command signal S becomes a value other than the designated pulse number when the triangle wave CA has 5 or less or 7 or more cycles during one cycle of the rotor electrical angle θm.

If five cycles are output in the triangle wave CA during one cycle of the rotor electrical angle θm, the rotor electrical angle θmis 360°/5=72° at the end of the first cycle of the triangle wave CA to give the upper threshold value Th θm1—UL of 72°.

On the other hand, if seven cycles are output in the triangle wave CA during one cycle of the rotor electrical angle θm, the rotor electrical angle θmis 360°/7=51.4° at the end of the first cycle of the triangle wave CA to give the lower threshold value Thθm1—LL of 51.4°.

As such, the upper and lower threshold values for θm2to θm5are calculated successively. When the upper and lower threshold values for θm 2to θm5are calculated, each threshold value is set in the triangle wave generating element4. When any of the rotor electrical angles θm1to θm5is at or below the lower threshold value, or at or above the upper threshold value, the triangle wave generating element4then changes the frequency of the triangle wave CA. By changing the frequency of the triangle wave CA, the time taken to get six cycles in the triangle wave CA is reduced from t1to t1′, as shown inFIG. 3. In the example shown inFIG. 3, the frequency of the triangle wave CA is increased by detecting that the rotor electrical angle θmis at or above the upper threshold value. By increasing the frequency of the triangle wave CA, the number of pulses output in the PWM signal PI during one cycle of the command signal S can be changed from five to six.

Concerning the calculation cycle, instead of setting it to the interval between 0° to the next 0° of the phase angle of the triangle wave CA, the calculation cycle may be set as desired.

Second Embodiment of the Motor Actuation Control

In the above description, the phase difference between the rotor electrical angle θmand the phase angle of the triangle wave CA is directly measured, but a reference angle, which will be described below, may be calculated as a virtual angle value to facilitate measurement of the phase θmtriangle wave CA.

A reference angle θsis calculated using the following Equation 1:
θs=(Kp×θm)−(360°×b)  Equation 1

wherein Kpis a designated pulse number and b is a coefficient to be set based on the value of the rotor electrical angle θm.

The coefficient b is next explained. The value for b may be any natural number from 0 to Kp−1. The triangle wave generating element4sets the value of b. Specifically, b=0 while the rotor electrical angle θmis between 0° and 60°. b=1 while the rotor electrical angle θmis between 61° and 120°. In this way, the value of b is incremented by 1 every time the rotor electrical angle θmis increased 60°. When the rotor electrical angle θmis 360°, the triangle wave generating element4returns b to zero. After that, the process is repeated. In this case, the rotor electrical angle θm, the coefficient b, and the reference angle θsare changed as in the following table 1. It is noted that the designated pulse number Kpis set to 6.

It can be recognized that the phase angle θCAof the triangle wave CA and the reference angle θsare in-phase when the rotor7rotates at a steady speed because both the reference angle θsand the triangle wave CA complete six cycles during one cycle of the rotor electrical angle θm. By calculating the reference angle θsso that it has the same cycle and phase as the triangle wave CA, the phase difference between the rotor electrical angle θmand the phase angle θCAof the triangle wave CA can be detected more easily.

If, when calculating the reference angle θs, the control unit1does not consider the component 360°×n (n is a natural number not less than 1), the equation will be θs=(Kp×θm).

FIGS. 4 and 5show the reference angle θsand the phase angle of the triangle wave θCAwhen the rotation rate of the rotor7changes rapidly due to tire slip or the like.

In response to the rapid change of rotation rate of the rotor7, the reference angle θscalculated from the rotor electrical angle θmis also changed rapidly. On the other hand, in the conventional motor actuation control, the cycle of the triangle wave CA does not change until after the rotor completes one rotation. Therefore, the phase angle of the triangle wave CA gradually becomes out of phase with the reference angle θs, and the phase of the triangle wave CA is delayed from the phase of the reference angle θs, as shown inFIG. 4.

FIG. 5shows the time varying phase difference between the phase angle θCAof the triangle wave CA and the reference angle θs. The phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsincreases linearly along a linear function over the interval between 0° and 180°. When the phase difference exceeds −180°, the phase difference is measured between the third cycle of the phase angle θCAof the triangle wave CA and the fourth cycle of the reference angle θs, instead of measuring the phase difference between the third cycle of the phase angle θCAof the triangle wave CA and the third cycle of the reference angle θs. That is to say, the number of cycles of the phase angle θCAof the triangle wave CA differs from that of the reference angle θsby 1 cycle in measuring the phase difference. After that, calculation of the phase difference continues by comparing the phase angle θCAof the triangle wave CA with the reference angle θs, with the number of cycles of both angles being mismatched by one cycle. As a result, as shown inFIG. 4, there are only five cycles in the triangle wave CA during six cycles of the reference angle θs. In this case, the PWM signal PI has five pulses, which is less than the designated pulse number of six, during one cycle of the command signal S, which may cause the malfunction of the control unit1.

As described above, when the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsexceeds 180°, there is a mismatch in the number of cycles of the phase angle θCAof the triangle wave CA and the reference angle θs. In this embodiment, therefore, the frequency of the triangle wave CA is changed before the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsexceeds 180°.

Specifically, the triangle wave generating element4measures the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsfor each predetermined calculation cycle, calculates the phase difference value of the next calculation cycle succeeding to the current cycle based on the phase difference value of the current and previous calculation cycles, and determines whether or not an obtained value deviates from ±180°. This control method will be described below with reference toFIGS. 6-8.

FIG. 6is a flowchart for determining whether or not the triangle wave generating element4should change the cycle of the triangle wave CA. The calculation cycle is set in the triangle wave generating element4to calculate the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θs(S1).

The triangle wave generating element4measures the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsfor each calculation period, calculates the slope of a line representing the increase in phase difference, based on the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsfor the current calculation cycle TC(0) and the previous calculation cycle TC(−1), and then calculates the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsfor the next calculation cycle TC(+1) (S2inFIG. 6).

The triangle wave generating element4determines whether or not the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsis at or below −180° or at or above 180° for the next calculation cycle TC (+1) (S3). If the phase difference falls within the range between −180° and +180°, the frequency of the triangle wave CA is not changed (S4), but if it is determined that the phase difference is at or below −180° or at or above +180°, the frequency of the triangle wave CA is changed (S5). As a result, the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsis gradually decreased, allowing the triangle wave CA to output six cycles during six cycles of the reference angle θs, as shown inFIG. 8.

If it is determined that the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsis at or below −180° during the current calculation cycle TC (+1), the triangle wave generating element4increases the frequency of the clock signal CLK that forms the triangle wave CA to advance the phase of the signal, because the phase angle θCAof the triangle wave CA is delayed from the reference angle θs. By advancing the phase, the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsis diminished, thereby preventing malfunction of the control unit1.

In addition, at the next operation cycle TC (+1) after the current period, if it is determined that the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsis at or above +180°, which represents that the phase angle θCAof the triangle wave CA is advanced from the phase of the reference angle θs, the triangle wave generating element4decreases the frequency of the clock signal CLK from the current frequency to delay the phase of the triangle wave CA.

As such, with this embodiment, it is possible to estimate the deviation of the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsfrom ±180°, thereby preventing malfunction of the control unit1.

Third Embodiment of the Motor Actuation Control

In the above embodiment, the deviation of the phase difference from ±180° between the phase angle θCAof the triangle wave CA and the reference angle θsis predicted based on the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsover the interval from the current calculation cycle TC (0) to the previous operation cycle (TC−1). Instead, it is also possible to change the frequency of the triangle wave CA by setting a predetermined threshold value and detecting whether or not the value of the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsexceeds the threshold value. In this case, the threshold value may be any value between −180° and +180°, because the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsmay take any value as long as it does not exceed ±180°. For example, when the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsis measured continuously, ±180° is set as the threshold value.

By assuming that tire slip does occur, it is also possible to calculate the threshold value in advance from the difference in rotation rate Δr between the rotation rate Rma, which is the rotation rate during tire slip, and the rotor rotation rate Rmm, which is the rotation rate stored in the triangle wave generating element4. Specifically, an increase amount X, which represents the amount that the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsincreases during one calculation cycle, may be calculated based on the difference in rotation rate Δr, and the threshold value is set according to the increase amount X of the phase difference. Such a calculation method of the threshold value will be described below.

By using the following Equation 2, the increase amount X of the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsduring one calculation cycle may be found:
X=|Δr|×T×Kp×P/60×360°  Equation 2

wherein

X is an increase amount of the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsduring one calculation period,

Δr is a difference between the actual rotation rate Rma of the rotor and the rotation rate Rmm of the rotor stored in the triangle wave generating element4,

T is a calculation cycle to calculate the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θs,

Kpis a designated pulse number, and

P is the number of pole pairs of the rotor.

For example, when the equation 2 is calculated at Δr=1,000 rpm, T=0.1 msec, Kp=6, and P=6, X will be 21.8°. This represents that, when the rotation rate of the rotor7is changed rapidly and the actual rotation rate Rma becomes 1,000 rpm faster than the rotation rate Rmm stored in the triangle wave generating element4, the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsis increased by 21.6° for every 0.1 milliseconds.

While the increase amount of the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsis determined from Equation 2, then the threshold value can be set. Specifically, as the increase amount of the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsduring one calculation cycle is 21.6°, the threshold value to be set is ±158° from 180°−21.6°. In other words, as shown inFIG. 9, if the current phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsis at or above 158.4°, or at or below −158.4°, the frequency of the triangle wave CA is changed.

In addition, the calculation cycle used in the above example is 0.1 milliseconds, but if the calculation cycle is set to 0.2 ms, for example, the threshold value to be set will be ±136.8°.

Changing the Cycle of the Triangle Wave CA

A method to determine whether or not the frequency of the triangle wave is changed based on the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θshas been described above. When it is determined that the frequency of the triangle wave CA should be changed, the triangle wave CA is changed as described below.

In this embodiment, when it is determined that the frequency of the triangle wave should be changed, the triangle wave generating element4increases or decreases a predetermined percentage of frequency from the current frequency. Specifically, the triangle wave generating element4changes the frequency of the clock signal CLK by setting a coefficient a in the following Equation 3:
New clock frequency=Current clock frequency×(1+a)  Equation 3

In the above equation, a is a coefficient which may be any real number; for example, if it is desired to increase the frequency of the triangle wave CA by 10 percent, a may be set to 0.1. It should be noted that a=0 while the motor actuation control continues smoothly. On the other hand, if it is desired to decrease the frequency of the triangle wave CA by 10%, a is −0.1 according to the above Equation 3.

In the embodiments described above, after changing the clock frequency fCLKduring one rotation of the rotor, the control unit1returns to calculate the rotation rate of the rotor according to one rotation of the rotor7, and again sets the clock frequency fCLKbased on the obtained rotation rate of the rotor. Instead, after changing the frequency of the triangle wave CA during one rotation of the rotor7, the clock frequency fCLKmay be fixed for a predetermined period of time to stably secure the pulse number of the PWM signal PI.

Instead of calculating the reference angle θsby multiplying the rotor electrical angle θmby the designated pulse number Kp, it is also possible to calculate a reference angle θs′ by dividing the phase angle θCAof the triangle wave CA by the designated pulse number Kpto measure the phase difference between the reference angle θs′ and the rotor electrical angle θm.

Although the rotor rotation rate Rm is calculated for each rotation of the rotor in this embodiment, the calculation timing of the rotor rotation rate may be set arbitrarily. Even so, the advantage of the present invention can be provided by setting a shorter calculation cycle of calculating the phase difference between the phase angle θCAof the triangle wave CA and the reference angle θsthan the calculation cycle of the rotor rotation rate.

APPLICABLE FIELD OF THE INVENTION

The present invention is applicable to the field of motor actuation control provided on motor vehicles including electric vehicles and hybrid vehicles.

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