WO2011010341A1

WO2011010341A1 - Current switching device and method used in the device

Info

Publication number: WO2011010341A1
Application number: PCT/JP2009/003410
Authority: WO
Inventors: 浜田英嗣
Original assignee: トヨタ自動車株式会社
Priority date: 2009-07-21
Filing date: 2009-07-21
Publication date: 2011-01-27

Abstract

Provided is a current switching device the output of which does not change abruptly even when an induction motor is controlled by using a plurality of current detection sensors. The currents flowing through the respective phases of the induction motor are detected with a low resolution and a high resolution. When the rotational speed of the induction motor is low, and a torque target value is low, the torque of the induction motor is controlled according to a current detected with the high resolution. On the other hand, when the rotational speed thereof is high, or the torque target value is high, the torque thereof is controlled according to a current detected with the low resolution. The currents detected with the respective resolutions are switched while being gradually changed from one to the other.

Description

Current switching device and method used in the device

The present invention relates to a current switching device, and more particularly to a current switching device mounted on a moving body such as an automobile.

In recent years, vehicles such as automobiles have, for example, an induction motor that is a source of driving force, an induction motor that generates power consumed by in-vehicle devices mounted on the vehicle, and a rear wheel of the vehicle by driving the steering wheel. Various induction motors such as an induction motor for controlling the motor are mounted. As an example of a technique for controlling an induction motor mounted on a vehicle, there is a stepping motor driving method and an apparatus (hereinafter referred to as a conventional technique) disclosed in Patent Document 1.

JP-A-5-207794

When controlling a stepping motor as in the above prior art, generally, a value of a current flowing through a stepping motor is fed back to a CPU (Central Processing Unit) as a current value, and the CPU is based on the fed back current value. To generate pulses for controlling the stepping motor. Here, when the allowable range of the current that can be passed through the stepping motor is relatively wide, if the current value to be fed back is measured by one current detection sensor, the resolution at the time of measurement must be lowered. It is difficult to measure with a resolution corresponding to. Therefore, conventionally, in order to measure the current value flowing through the stepping motor having a large allowable range described above with a resolution corresponding to the measurement range, measurement is performed while switching a plurality of current detection sensors having different resolutions.

However, when measuring a current value while switching a plurality of current detection sensors, it is measured when switching each current detection sensor due to variations in electrical characteristics of each current detection sensor and differences in resolution. Difference in current value. Then, if the stepping motor is controlled based on the current value that causes a difference when switching the current detection sensor, the output of the stepping motor, such as the torque or the rotation speed, changes steeply. This is the same when controlling various induction motors as well as stepping motors.

Therefore, an object of the present invention is to provide a current switching device in which the output does not change sharply even when an induction motor is controlled using a plurality of current detection sensors.

In order to achieve the above object, the present invention has the following features.
According to a first aspect of the present invention, there is provided a first current detection unit that detects a current flowing in each phase of an induction motor as a first current, and a second current having a higher resolution than the first current detection unit. A second current detection unit that detects the current; a control unit that controls the torque of the induction motor to be a target value based on at least one of the first current and the second current; and And switching means for switching while gradually changing the current from one current to the other when the current for controlling the electric motor is switched between the first current and the second current.

According to a second aspect, in the first aspect, when the switching unit switches the current when the control unit controls the induction motor by gradually changing the current between the first current and the second current, The first current and the second current are gradually changed by weighted averaging.

A third aspect further includes a rotation speed detection means for detecting the rotation speed of the rotor of the induction motor in the first aspect, and the control means has a predetermined rotation speed detected by the rotation speed detection means. The induction motor is controlled based on the second current when the target value is less than the second threshold value that is less than the first threshold value.

According to a fourth aspect, in the first aspect described above, the control unit further includes a rotation speed detection unit that detects a rotation speed of the rotor of the induction motor, and the control unit has a predetermined rotation speed detected by the rotation speed detection unit. When the current value is not less than the first threshold value or the target value is not less than the predetermined second threshold value, the induction motor is controlled based on the first current.

In the fifth aspect, in the second aspect, the induction motor generates a driving force that causes the vehicle to travel.

In a sixth aspect according to the first aspect, the induction motor is mounted on a passenger car, and the control means controls the torque of the induction motor having an allowable maximum current of 200 amperes to 1000 amperes.

In a seventh aspect, in the first aspect, the induction motor is mounted on a passenger car, and the control means controls the torque of the induction motor having a maximum power consumption of 20 kilowatts to 200 kilowatts.

The eighth aspect includes a first current detection step for detecting a current flowing in each phase of the induction motor as a first current, and a second resolution with higher resolution than when the current is detected in the first current detection step. A control step for controlling the induction motor torque to be a target value based on at least one of the first current and the second current; And a switching step of switching while gradually changing from one current to the other when switching the current for controlling the induction motor between the first current and the second current.

According to the first aspect, even when the induction motor is controlled by using the first current detection unit and the second current detection unit as a plurality of current detection sensors, the current switching is performed so that the output torque does not change sharply. Equipment can be provided.

According to the second aspect, when the current used for controlling the induction motor is switched from one of the current detected with low resolution and the current detected with high resolution to the other, the torque of the induction motor Can be prevented from changing sharply.

According to the third aspect, when the rotation speed of the induction motor is low and the target torque value is the low torque target value, the torque of the induction motor can be controlled smoothly.

According to the fourth aspect, when the rotation speed of the induction motor is a low rotation speed and the target value of the torque is a high torque target value, the torque of the induction motor is controlled based on an incorrect current value. You can prevent it.

According to the fifth aspect, the vehicle is caused by a steep change in the torque of the induction motor that occurs when switching from one of the current detected with low resolution and the current detected with high resolution to the other. This prevents vibrations from being transmitted to the passenger.

According to the sixth aspect, a markedly high reduction effect can be achieved when reducing vibrations that occur when controlling an induction motor mounted on a passenger car.

According to the seventh aspect, a markedly high reduction effect can be achieved when reducing vibrations that occur when controlling an induction motor mounted on a passenger car.

Further, according to the switching method according to the present invention, the same effects as those of the current switching device according to the present invention can be obtained.

FIG. 1 is a block diagram illustrating a schematic configuration of the current switching device according to the first embodiment. FIG. 2 is a diagram showing a more detailed configuration of the phase current detection unit. FIG. 3A is a diagram comparing an example of values generated by the low resolution detection unit and the high resolution detection unit, respectively. FIG. 3B is a diagram comparing an example of values generated by the low resolution detection unit and the high resolution detection unit, respectively. FIG. 3C is a diagram comparing an example of a low resolution detection value and a high resolution detection value. FIG. 3D is a diagram comparing an example of a low resolution detection value and a high resolution detection value. FIG. 4 is a diagram illustrating an example of a current value calculated so as to gradually change based on the low resolution detection value and the high resolution detection value. FIG. 5 is a flowchart showing processing of the control unit according to the first embodiment.

(First embodiment)
FIG. 1 is a block diagram showing a schematic configuration of a current switching device 1 according to a first embodiment of the present invention. The current switching device 1 according to the present embodiment includes an induction motor 101, a first phase current detection unit 102, a second phase current detection unit 103, a third phase current detection unit 104, and a rotation speed detection unit. 105, a control unit 106, and a drive unit 107.

The induction motor 101 is a so-called motor that rotates a rotor with electric power supplied from the drive unit 107. In this embodiment, the case where the induction motor 101 is a three-phase AC induction motor will be described as an example.

The first phase current detection unit 102 detects the value of the current flowing from the drive unit 107 to the first phase (in this embodiment, the U phase) of the induction motor 101. The first phase current detection unit 102 has a first resolution with a relatively high resolution (hereinafter referred to as “high resolution”) and a relatively low resolution (hereinafter referred to as “low resolution”). Detect the value of the current flowing through the phase. The first phase current detection unit 102 generates a detection signal H1 indicating the value of the current detected with high resolution. Further, the first phase current detection unit 102 generates a detection signal L1 indicating the value of the current detected with low resolution.

The second phase current detection unit 103 is configured to reduce the value of the current flowing from the drive unit 107 to the second phase (V phase in the present embodiment) of the induction motor 101 as in the first phase current detection unit 102. And with high resolution. The second phase current detection unit 103 generates a detection signal H2 indicating the value of the current detected with high resolution. Further, the second phase current detection unit 103 generates a detection signal L2 indicating the value of the current detected with low resolution.

The third phase current detection unit 104 is configured to reduce the value of the current flowing from the drive unit 107 to the third phase (W phase in this embodiment) of the induction motor 101 in the same manner as the first phase current detection unit 102. And with high resolution. The third phase current detection unit 104 generates a detection signal H3 indicating the value of the current detected with high resolution. Further, the third phase current detection unit 104 generates a detection signal L3 indicating the value of the current detected with low resolution.

A more detailed description of each of the first phase current detection unit 102 to the third phase current detection unit 104 will be given later.

Rotational speed detector 105 detects the rotational speed of the rotor of induction motor 101. The rotation speed detection unit 105 acquires a speed signal Vs having a voltage corresponding to the rotation speed of the rotor of the induction motor 101. The speed signal Vs is a signal generated by, for example, a resolver or a rotary encoder attached so as to be able to generate a voltage corresponding to the rotation speed of the rotor of the induction motor 101. Then, the rotation speed detection unit 105 converts the voltage of the speed signal Vs into a digital value indicating the rotation speed corresponding to the magnitude of the voltage, and generates a digital signal indicating the converted digital value as the rotation speed signal V. To do.

Based on the values indicated by detection signal H1 to detection signal H3, detection signal L1 to detection signal L3, rotation speed signal V, and torque target signal To, control unit 106 determines when the rotor of induction motor 101 rotates. Control is performed by giving an instruction to the drive unit 107 described later so that the torque becomes a torque target value having a magnitude indicated by the torque target signal To. It is assumed that the torque target signal To is generated by a generator not shown. A more detailed description of the control unit 106 will be described later.

The drive unit 107 controls the voltage and current of power supplied from a power source (not shown) according to an instruction given from the control unit 106, and supplies it to the induction motor 101. The drive unit 107 is typically an inverter circuit including one or more switching elements (in the case where the induction motor 101 is a three-phase induction motor, for example, six switching elements are included). Based on the values indicated by the detection signal H1 to detection signal H3, the detection signal L1 to detection signal L3, the rotation speed signal V, and the torque target signal To, the control unit 106 sets the switching elements included in the drive unit 107, respectively. An instruction to open and close is given, and the timing or duty ratio for opening and closing each is changed. Based on the values indicated by the detection signal H1 to detection signal H3, the detection signal L1 to detection signal L3, the rotation speed signal V, and the torque target signal To, the control unit 106 sets the switching elements included in the drive unit 107, respectively. By changing the timing for opening and closing or the duty ratio, the magnitude of the torque when the rotor of the induction motor 101 rotates becomes the magnitude indicated by the torque target signal To in each phase of the induction motor 101. The so-called PWM (Pulse Width Modulation) control for controlling the flowing current is performed.

The above is the description of the schematic configuration of the current switching device 1 according to the present embodiment.

Next, the first phase current detection unit 102 to the third phase current detection unit 104 according to the present embodiment will be described in detail. FIG. 2 is a block diagram showing a more detailed configuration of the first phase current detection unit 102 to the third phase current detection unit 104 according to the present embodiment. Each of the first phase current detection unit 102 to the third phase current detection unit 104 according to the present embodiment includes a low resolution detection unit 201 that detects a current value at the low resolution described above, and a current at the high resolution described above. And a high-resolution detection unit 202 that detects the value of.

The low resolution detection unit 201 includes an amplification unit 301, an AD converter 302, and a correction unit 303. The amplifying unit 301 amplifies a voltage proportional to the current flowing in the phase detected by each of the first phase current detecting unit 102 to the third phase current detecting unit 104 including the amplifying unit 301. Here, the voltage proportional to the current flowing through the phase will be described. Each path of current flowing from the drive unit 107 to each phase of the induction motor 101 is wired so as to pass through a gap at the center of a ring-shaped magnetic body (not shown) around which a conducting wire is wound. A ring-shaped magnetic body around which a conductive wire is wound is a so-called current transformer, which generates an electromotive force when a current flows through a path passing through a central gap, and is a conductive wire wound with a voltage (potential difference) corresponding to the flowing current. At both ends. In the present embodiment, as an example, a current transformer is provided for each path of the current flowing in each phase so that a voltage corresponding to the current flowing in each of the first to third phases can be generated. It shall be. That is, the voltage proportional to the current flowing in the phase is a voltage detected by a current transformer provided in the path of the current flowing in each phase.

The current transformer provided in the path of the current flowing in the first phase generates a current signal A1 having a voltage proportional to the current flowing in the first phase. Similarly, the current transformer provided in the path of the current flowing through the second phase generates a current signal A2 having a voltage proportional to the current flowing through the second phase. The current transformer provided in the path of the current flowing in the third phase generates a current signal A3 having a voltage proportional to the current flowing in the third phase.

Then, the amplification unit 301 included in the first phase current detection unit 102 acquires the current signal A1 generated by the current transformer provided in the path of the current flowing in the first phase, and the acquired current signal A1 The voltage is amplified with a predetermined amplification factor. Similarly, the amplification unit 301 included in the second phase current detection unit 103 acquires the current signal A2 generated by the current transformer provided in the path of the current flowing in the second phase, and acquires the acquired current signal A2. Is amplified at a predetermined amplification factor. Then, the amplification unit 301 included in the third phase current detection unit 104 acquires the current signal A3 generated by the current transformer provided in the path of the current flowing in the third phase, and the acquired current signal A3 The voltage is amplified with a predetermined amplification factor.

The AD converter 302 converts the magnitude of the voltage amplified by the amplifying unit 301 into a digital value, and generates digital signals D1 to D3 indicating the converted digital values, respectively.

More specifically, the AD converter 302 included in the first phase current detection unit 102 uses the voltage of the current signal A1 amplified by the amplification unit 301 included in the first phase current detection unit 102 as the voltage. A digital signal D1 indicating the converted digital value is generated by converting into a digital value indicating the magnitude of the current according to the magnitude. Similarly, the AD converter 302 included in the second phase current detection unit 103 converts the voltage of the current signal A2 amplified by the amplification unit 301 included in the second phase current detection unit 103 to the magnitude of the voltage. The digital value indicating the magnitude of the corresponding current is converted into a digital signal D2 indicating the converted digital value. Then, the AD converter 302 included in the third phase current detection unit 104 determines the voltage of the current signal A3 amplified by the amplification unit 301 included in the third phase current detection unit 104 according to the magnitude of the voltage. The digital value indicating the magnitude of the current is converted to a digital signal D3 indicating the converted digital value.

The correction unit 303 corrects the digital value indicated by the digital signal converted by the AD converter 302, and generates the detection signal L1 to the detection signal L3 described above indicating the corrected digital value. More specifically, the correction unit 303 included in the first phase current detection unit 102 corrects the digital value indicated by the digital signal converted by the AD converter 302 included in the first phase current detection unit 102. The detection signal L1 indicating the corrected digital value is generated. Similarly, the correction unit 303 included in the second phase current detection unit 103 corrects and corrects the digital value indicated by the digital signal converted by the AD converter 302 included in the second phase current detection unit 103. A detection signal L2 indicating a digital value is generated. Then, the correction unit 303 included in the third phase current detection unit 104 corrects the digital value indicated by the digital signal converted by the AD converter 302 included in the third phase current detection unit 104, and corrects the digital value. A detection signal L3 indicating a value is generated.

The low resolution detection unit 201 obtains and amplifies the current signal generated by the current transformer described above by the amplification unit 301, converts the magnitude of the voltage of the amplified signal into a digital value by the AD converter 302, and corrects the current signal. Correction is made at 303. Thereby, the low resolution detector 201 included in each of the first phase current detector 102 to the third phase current detector 104 detects the value of the current flowing in each of the first phase to the third phase, Digital signals indicating the detected current values as digital values can be generated as detection signals L1 to L3, respectively.

The high resolution detection unit 202 includes an amplification unit 401 and an AD converter 402. Similarly to the amplification unit 301 included in the low resolution detection unit 201, the amplification unit 401 amplifies a voltage proportional to the current flowing in the phase to be detected with a predetermined amplification factor. However, the amplification factor of the amplification unit 401 included in the high resolution detection unit 202 is determined in advance so as to be higher than the amplification factor predetermined in the amplification unit 301 included in the low resolution detection unit 201.

More specifically, the amplification unit 401 included in the first phase current detection unit 102 acquires and acquires the current signal A1 generated by the current transformer provided in the path of the current flowing in the first phase. The voltage of the current signal A1 is amplified with a predetermined amplification factor. Similarly, the amplification unit 401 included in the second phase current detection unit 103 acquires the current signal A2 generated by the current transformer provided in the path of the current flowing in the second phase, and acquires the acquired current signal A2. Is amplified at a predetermined amplification factor. Then, the amplification unit 401 included in the third phase current detection unit 104 acquires the current signal A3 generated by the current transformer provided in the path of the current flowing in the third phase, and the acquired current signal A3 The voltage is amplified with a predetermined amplification factor.

The AD converter 402 converts the magnitude of the voltage amplified by the amplification unit 401 into a digital value. More specifically, the AD converter 402 included in the first phase current detection unit 102 digitally calculates the magnitude of the voltage of the current signal A1 amplified by the amplification unit 401 included in the first phase current detection unit 102. The detection signal H1 indicating the converted digital value is generated. Similarly, the AD converter 402 included in the second phase current detection unit 103 converts the magnitude of the voltage of the current signal A2 amplified by the amplification unit 401 included in the second phase current detection unit 103 into a digital value. Thus, a detection signal H2 indicating the converted digital value is generated. Then, the amplification unit 401 included in the third phase current detection unit 104 converts the voltage magnitude of the current signal A3 amplified by the amplification unit 401 included in the third phase current detection unit 104 into a digital value. Thus, a detection signal H3 indicating the converted digital value is generated.

The high resolution detection unit 202 converts the magnitude of the voltage of the current signal amplified by the amplification unit 401 having a higher amplification factor than the amplification unit 301 included in the low resolution detection unit 201 into a digital value by the AD converter 402. As a result, the current value can be detected with a higher resolution than that of the low resolution detector 201.

For this reason, a case where the amplification factor of the amplification unit 401 is set in advance by 10 times higher than the amplification factor of the amplification unit 301 will be described as an example. When the amplification factor of the amplification unit 401 is predetermined to be ten times higher than the amplification factor of the amplification unit 301, the digital value converted by the AD converter 402 included in the high resolution detection unit 202 is included in the low resolution detection unit 201. The digital value converted by the AD converter 302 is 10 times larger. Therefore, the digital value converted by the AD converter 402 reflects a change in value that is smaller by one tenth than the digital value converted by the AD converter 302. As a result, the current value detected by the high resolution detection unit 202 is a digital value converted by the AD converter 302, that is, a value that is smaller by one tenth than the current value detected by the low resolution detection unit 201. Is reflected, and the high resolution detection unit 202 can detect the current value with a relatively high resolution higher than that of the low resolution detection unit 201.

The reason why the correction unit 303 corrects the digital value converted by the AD converter 302 is that the amplification factors of the amplification unit 301 and the amplification unit 401 are different from each other. More specifically, for example, when the amplification factor of the amplification unit 402 is 10 times larger than the amplification factor of the amplification unit 302 as in the above-described example, the digital value converted by the AD converter 302 is It becomes a value smaller by 1/10 than the digital value converted in 402. For this reason, the correction unit 303 converts the digital value converted by the AD converter 302 so that the digital value converted by the AD converter 302 matches the digital value converted by the AD converter 402 included in the same phase current detection unit. A correction that amplifies the signal by 10 times is performed. As a result, the digital value corrected by the correction unit 303 becomes a digital value indicating the magnitude of the current in the same manner as the digital value converted by the AD converter 402. The magnification when the correction unit 303 amplifies and corrects the digital value converted by the AD converter 302 is such that the digital value converted by the AD converter 302 matches the digital value converted by the AD converter 402. It is assumed that the amplification unit 301 and the amplification unit 401 are determined in advance based on the respective amplification factors. For example, as described above, if the amplification factor of the amplification unit 401 is determined to be 10 times the amplification factor of the amplification unit 301, the magnification set in advance in the correction unit 303 is 10 times. It becomes.

The above is a more detailed description of the first phase current detection unit 102 to the third phase current detection unit 104. Next, the control unit 106 according to the present embodiment will be described in more detail. The control unit 106 according to the present embodiment performs processing in parallel with the above-described conventionally known PWM control together with the processing shown in the flowchart of FIG. Then, the control unit 106 according to the present embodiment performs control while judging and switching the value of the current used when performing PWM control. Therefore, before describing the processing shown in the flowchart of FIG. 5, first, processing in which the control unit 106 determines a current value used for PWM control will be described.

The control unit 106 according to the present embodiment detects the current value used for PWM control by the low resolution detection unit 201 included in each of the first phase current detection unit 102 to the third phase current detection unit 104. Each current value (digital value indicated by each of the detection signals L1 to L3; hereinafter referred to as a low resolution detection value L) and each current value detected by the high resolution detection unit 202 included therein (detection) The digital value indicated by each of the signals H1 to H3 (hereinafter referred to as a high resolution detection value H). More specifically, the control unit 106 according to the present embodiment uses the low resolution detection value L indicated by the detection signal L1 to the detection signal L3 and the detection signal H1 to the detection signal H3 as current values used for PWM control. PWM control is performed while switching between the high-resolution detection values H indicated by. The control unit 106 indicates a rotation speed indicated by the rotation speed signal V generated by the rotation speed detection unit 105 (hereinafter simply referred to as a rotation speed) and a torque target signal To generated by a generation unit (not shown). On the basis of the torque target value (hereinafter simply referred to as torque target value), it is determined which of the low resolution detection value L and the high resolution detection value H is used as the current value used for PWM control.

The control unit 106 is a low rotational speed whose rotational speed is less than a predetermined threshold th1 (hereinafter referred to as a low rotational speed), and a small torque target value less than a predetermined threshold th2. When it is a torque target value (hereinafter referred to as a low torque target value), it is determined to use the high-resolution detection value H described above for PWM control. This is because if the PWM control is performed based on the low resolution detection value L, the torque when the rotor of the induction motor 101 rotates cannot be controlled smoothly. More specifically, as is clear from the above description, the low resolution detection value L is a value obtained by amplifying the digital value converted by the AD converter 302 at a predetermined magnification, and is intermittent according to the magnification. Since it is a value (for example, an intermittent value of a multiple of 10 if the magnification is 10 times), the resolution is relatively low compared to the resolution of the high resolution detection value H detected by the high resolution detection unit 202 The current value detected at. That is, the low resolution detection value L is an intermittent value that can show only a relatively large change. When the control unit 106 performs PWM control based on the low resolution detection value L, the low resolution detection value L indicating a relatively large change is fed back, so that the torque controlled by the control unit 106 is also relative. Therefore, control can be performed only to make a large and steep change, so-called torque ripple occurs, and smooth control cannot be performed.

For example, when the induction motor 101 according to the present embodiment is used for generating a driving force for driving a moving body such as an automobile (hereinafter referred to as the host vehicle), the low rotation speed described above and the low torque described above are used. When the control unit 106 performs PWM control based on the low resolution detection value L when the target value is reached, a relatively large and sharply changing torque is transmitted to the passenger as vibration of the host vehicle.

On the other hand, as is clear from the above description, even when the detected current value changes relatively small, the high resolution detection value H reflects the changed current value. That is, the high-resolution detection value H is a value that can indicate a relatively small change in addition to a relatively large change. When the control unit 106 performs PWM control based on the high-resolution detection value H, the high-resolution detection value H that indicates a relatively small change is fed back, so that the torque controlled by the control unit 106 is also relative. The torque can be controlled so as to change slightly, and the torque can be controlled so as to change more smoothly.

Therefore, the control unit 106 according to the present embodiment determines to use the high-resolution detection value H for PWM control when the rotation speed is low and the torque target value is low. The control unit 106 performs PWM control that can smoothly change the torque by performing PWM control using the high resolution detection value H when the rotation speed is low and the target torque value is low. Can do.

On the other hand, the controller 106 has a high rotational speed whose rotational speed is not less than the aforementioned threshold value th1 (hereinafter referred to as high rotational speed), or a high torque target value whose torque target value is not less than the aforementioned threshold value th2. When it is (hereinafter referred to as a high torque target value), it is determined that the low resolution detection value L is used for PWM control. This is because the control unit 106 controls the drive unit 107 so that the current flowing through the induction motor 101 becomes relatively large when the rotational speed is high or the target value is a high torque. More specifically, when the rotational speed is high or the target torque value is high, the value of the current flowing from the driving unit 107 to each of the first to third phases is relatively large. As described above, the high resolution detection unit 202 has a higher amplification rate than the amplification unit 301 included in the low resolution detection unit 201 and has a relatively large amount flowing in each of the first to third phases. The amplifying unit 401 amplifies the voltages of the relatively high current signals A1 to A3 that are proportional to the current value.

Therefore, as described above, when the rotation speed is high or the torque target value is high, the magnitude of the relatively high voltage amplified by the amplification unit 401 with a relatively high amplification factor is set as the AD converter 402. Converts to a digital value. However, an allowable voltage range of a voltage that can be converted into a digital value by the AD converter 402 is determined in advance. For this reason, when a relatively high voltage amplified with a relatively high amplification factor is converted into a digital value by the AD converter 402, the AD converter 402 is not saturated even though the digital value converted by the AD converter 302 is not saturated. The digital value converted by is saturated. Therefore, the high resolution detection value H detected when the rotation speed is high or the target torque value is a value that does not accurately indicate the value of the current flowing in each phase.

Therefore, the control unit 106 according to the present embodiment determines to use a digital value that does not saturate, that is, the low resolution detection value L, for PWM control when the rotational speed is high or the target torque value is high. Based on the high-resolution detection value H that does not indicate an accurate value by performing PWM control using the low-resolution detection value L when the control unit 106 has a high rotation speed or a high torque target value. This prevents PWM control.

When the control unit 106 performs PWM control based on the low resolution detection value L, smooth control cannot be performed as described above. However, for example, when the induction motor 101 according to the present embodiment is used to generate a driving force that causes the host vehicle to travel, the host vehicle is relatively less than when it has a high rotational speed or a high torque target value. It can be considered that the vehicle is traveling at a high traveling speed, or a relatively high torque load is applied to the rotor of the induction motor 101 of the host vehicle. When the host vehicle is traveling at a relatively high traveling speed or when a relatively high load is applied to the induction motor 101 of the host vehicle, the torque when the rotor of the induction motor 101 rotates is increased. Even if the change is relatively large and steep, the vibration of the host vehicle that occurs as described above is not noticeable to the passenger of the host vehicle.

The above is the description of the process in which the control unit 106 determines the value of the current used for the PWM control. The control unit 106 according to the present embodiment determines the current value used for the PWM control as described above, and performs the PWM control with the determined value, so that the optimum current according to the rotation speed and the torque target value is obtained. PWM control can be performed using the value of the switched current. For example, when the induction motor 101 according to the present embodiment is used to generate a driving force for driving the host vehicle, the control unit 106 calculates the low resolution detection value L and the high resolution detection value H as described above. By performing PWM control while switching, it is possible to reduce the vibration of the host vehicle caused by a sharp change in torque.

As described above, when the control unit 106 performs PWM control while switching between the low resolution detection value L and the high resolution detection value H, during the period in which the PWM control is performed using any of the detection values, It is possible to reduce the vibration of the host vehicle caused by the change. However, when the control unit 106 performs PWM control while switching between the low resolution detection value L and the high resolution detection value H, the torque may change greatly at the time of switching. There are two reasons why the torque changes greatly when switching between the low resolution detection value L and the high resolution detection value H.

The first cause is a variation in the electrical characteristics of the electric circuits constituting the low resolution detector 201 and the high resolution detector 202, respectively.

More specifically, the amplification units 301 included in each of the first phase current detection unit 102 to the third phase current detection unit 104 have the aforementioned variation in electrical characteristics even if the same amplification factor is determined in advance. As a result, the amplification factor also varies. The same applies to the amplification unit 401 included in each of the first phase current detection unit 102 to the third phase current detection unit 104.

Therefore, even if the magnification of the correction unit 303 is determined in advance based on the amplification factor of the amplification unit 301 and the amplification factor of the amplification unit 401, the amplification unit 301 included in the same phase current detection unit, and the amplification unit Variations occur in the amplification factors of the units 401. For this reason, there may be a discrepancy between the respective digital values indicated by the detection signals generated by the low resolution detector 201 and the high resolution detector 202 included in the same phase current detector.

The low-resolution detector 201 and the low-resolution detector 201 included in the first phase current detector 102 in the case where a mismatch occurs between the digital values indicated by the detection signals generated by the high-resolution detector 202 and the high-resolution detector 202, and A description will be given by comparing values indicated by signals generated in the high-resolution detection unit 202, respectively.

FIG. 3A illustrates a case where each of the amplifying unit 301 and the amplifying unit 401 is assumed to have no variation in electrical characteristics, and each of the amplifying unit 301 and the amplifying unit 401 includes a low-resolution detecting unit 201 included in the first phase current detecting unit 102. It is a figure which compares and shows an example of the value shown by the signal produced | generated and the signal each produced | generated inside the high-resolution detection part 202 contained in the same phase current detection part. 3A shows the voltage of the current signal A1 amplified by the amplification unit 301 included in the first phase current detection unit 102, the digital value obtained by converting the voltage of the current signal A1 by the AD converter 302, and the digital value. A digital value (low resolution detection value L) corrected by the correction unit 303, the voltage of the current signal A1 amplified by the amplification unit 401 included in the same phase current detection unit, and the voltage of the current signal A1 are converted into an AD converter. The digital value (high resolution detection value H) converted in 402 is shown. In FIG. 3A, only the digital value corrected by the correction unit 303 is indicated by a broken line for convenience of illustration. In addition, the example illustrated in FIG. 3A illustrates signals generated when an amplification factor of the amplification unit 401 is determined in advance by an amplification factor that is ten times higher than the amplification factor of the amplification unit 301. When an amplification factor that is 10 times higher than the amplification factor of the amplification unit 301 is predetermined in the amplification unit 401, the correction unit 303 has a predetermined magnification of 10 times, as is apparent from the above description. Therefore, the digital value converted by the AD converter 302 is corrected to 10 times the value.

When there is no variation in the amplification factors of the amplification unit 301 and the amplification unit 401, the voltage of the current signal A1 amplified by the amplification unit 301 is converted into a digital value by the AD converter 302, and then the correction unit 303 performs 10 minutes. As shown in FIG. 3A, the digital value corrected so as to be 1 is the same value as the digital value converted by the AD converter 402.

On the other hand, FIG. 3B is generated inside the low-resolution detection unit 201 included in the first phase current detection unit 102 when variation in electrical characteristics occurs in each of the amplification unit 301 and the amplification unit 401. It is a figure which compares and shows an example of the value shown by the signal and the signal each produced | generated inside the high resolution detection part 202 contained in the same phase current detection part. 3B shows the voltage of the current signal A1 amplified by the amplifier 301 included in the first phase current detector 102, the digital value obtained by converting the voltage of the current signal A1 by the AD converter 302, and the digital value. A digital value (low resolution detection value L) corrected by the correction unit 303, the voltage of the current signal A1 amplified by the amplification unit 401 included in the same phase current detection unit, and the voltage of the current signal A1 are converted into an AD converter. The digital value (high resolution detection value H) converted in 402 is shown. In FIG. 3B, only the digital value corrected by the correction unit 303 is indicated by a broken line for convenience of illustration.

In the example shown in FIG. 3B, the amplification factor 401 has an amplification factor that is 10 times higher than the amplification factor of the amplification unit 301 in advance. In fact, a signal generated when the amplification unit 401 amplifies the voltage of the current signal A1 by 9.5 times the amplification factor of the amplification unit 301 is shown. As shown as an example in FIG. 3B, when the above-described variation in electrical characteristics occurs, the digital value corrected by the correction unit 303 does not match the digital value converted by the AD converter 402. This is because the amplification factor of the amplification unit 401 varies even though the magnification of the correction unit 303 is predetermined based on the amplification factor predetermined for each of the amplification unit 401 and the amplification unit 301. This is because. More specifically, when the amplification factor of 10 times that of the amplification unit 301 is predetermined in the amplification unit 401, the magnification predetermined in the correction unit 303 is 10 times as described above. However, in actuality, the amplifying unit 401 amplifies the voltage of the signal at an amplification factor 9.5 times that of the amplifying unit 301. For this reason, when the digital value obtained by converting the voltage of the amplified current signal A1 by the AD converter 302 is corrected to a value 10 times by the correction unit 303, the corrected digital value is the AD value included in the same phase current detection unit. This is because it is 10 / 9.5 times the digital value converted by the converter 402.

The digital value corrected by the correction unit 303, that is, the high resolution detection value H detected by the high resolution detection unit 202, and the digital value converted by the AD converter 302, that is, the low resolution detection value L are one. If not, when the control unit 106 switches between the low resolution detection value L and the high resolution detection value H as described above, the current value detected by the first phase current detection unit 102 becomes the first value. From the value indicated by the detection signal L1 generated by the low resolution detection unit 201 included in the phase current detection unit 102, the detection signal H1 generated by the high resolution detection unit 202 included in the same phase current detection unit is indicated. Switch instantly to the value. That is, the value of the current used by the control unit 106 for PWM control greatly changes to a different value. For this reason, the electric current of the electric power which the control part 106 controls the drive part 107 and supplies to the induction motor 101 changes a lot according to the value of the electric current which the control part 106 uses for PWM control. Therefore, when the control unit 106 performs PWM control while switching between the low resolution detection value L and the high resolution detection value H as described above, the torque greatly changes at the time of switching. This is the explanation of the first cause.

The second cause is that the resolution of the low resolution detector 201 and the resolution of the high resolution detector 202 when the range of current that can be passed through the induction motor 101 (hereinafter referred to as the allowable current range) is relatively large. This is the reason why the difference between The second cause will be described by taking, as an example, a difference that occurs in the resolution of the low resolution detection unit 201 and the high resolution detection unit 202 included in the first phase current detection unit 102.

Here, the AD converter 302 and AD converter 402 included in the first phase current detection unit 102 respectively change the voltage allowable range of the current signal (hereinafter referred to as the allowable voltage range), the resolution, and the like. In other words, it is assumed that the induction motor 101 having a relatively large allowable current range is used without changing the specifications of each AD converter. In addition, the range of current values that can be detected by the low-resolution detection unit 201 according to the present embodiment (hereinafter referred to as a detection range) is the same as the allowable current range of the induction motor 101. In the present embodiment, if the allowable current range of the induction motor 101 is relatively increased without changing the specifications of the AD converter 302, the detection range of the low resolution detection unit 201 becomes the same range as the allowable current range of the induction motor 101. Must be expanded as follows. For this reason, the resolution of the low resolution detector 201 is further lowered.

More specifically, in order to expand the detection range of the low resolution detection unit 201 without changing the allowable voltage range of the AD converter 302 included in the low resolution detection unit 201, a current signal A1 having a relatively large voltage is generated. Even so, the amplification factor of the amplifying unit 301 must be relatively small so as not to exceed the allowable voltage range of the AD converter 302. However, even if the amount of change in voltage of the current signal A1 is the same, if the amplification factor of the amplification unit 301 is relatively small, the amplification factor of the amplification unit 301 is not relatively small compared to the case where the amplification factor 301 is not relatively small. The amount of change in the voltage of the signal A1 is relatively reduced. As described above, when the voltage of the current signal A1 whose amount of change is relatively reduced without changing the resolution of the AD converter 302 is converted into a digital value by the AD converter 302, the converted digital value is converted into the current signal A1. A relatively small change in the voltage is not reflected. For this reason, as described above, when the induction motor 101 having a relatively large allowable current range is used without changing the specifications of the AD converter 302, the resolution of the low resolution detection unit 201 becomes lower.

On the other hand, the resolution of the high resolution detection unit 202 is determined in advance so as to be a resolution corresponding to the smoothness of control required when the rotation speed is low and the target torque value is low as described above. Further, as is apparent from the above description, the resolution of the high resolution detection unit 202 is determined by the amplification factor of the amplification unit 401 regardless of the allowable current range of the induction motor 101. For this reason, even if the allowable current range of the induction motor 101 is relatively increased without changing the specifications of the AD converter 402, the resolution of the high resolution detection unit 202 can be reduced by setting the amplification factor of the amplification unit 401 in advance. The required high resolution can be achieved.

Therefore, if the allowable current range of the induction motor 101 is relatively increased without changing the specifications of the AD converter 302 and the AD converter 402, the resolution of the low resolution detector 201 is relatively lowered, and the high resolution detector The resolution of 202 need not be changed. For this reason, when the allowable current range of the induction motor 101 is relatively increased, the difference between the resolution of the low resolution detector 201 and the resolution of the high resolution detector 202 is relatively increased.

FIG. 3C shows the value of the current detected by the low resolution detection unit 201 included in the first phase current detection unit 102 when the allowable current range of the induction motor 101 is relatively small, that is, the low resolution detection value L. FIG. 6 is a diagram comparing an example of a current value detected by a high resolution detection unit 202 included in the same phase current detection unit, that is, a high resolution detection value H. In FIG. 3C, the high resolution detection value H is indicated by a solid line, and the low resolution detection value L is indicated by a broken line. Further, in FIG. 3C, the voltage of the current signal A1 is indicated by a solid line. As shown in FIG. 3C, the largest difference between the low resolution detection value L and the high resolution detection value H that occurs when the allowable current range of the induction motor 101 is relatively small is Δ1.

On the other hand, FIG. 3D shows a low resolution detected by the low resolution detection unit 201 and the high resolution detection unit 202 included in the first phase current detection unit 102 when the allowable current range of the induction motor 101 is relatively large. It is a figure which compares an example of the resolution detection value L and the high resolution detection value H. In FIG. 3D, as in FIG. 3C, the high resolution detection value H is indicated by a solid line, and the low resolution detection value L is indicated by a broken line. Further, in FIG. 3D, the voltage of the current signal A1 is indicated by a solid line. 3D also shows the difference Δ1 shown in FIG. 3C for comparison. As shown in FIG. 3D, the largest difference between the low resolution detection value L and the high resolution detection value H when the allowable current range of the induction motor 101 is relatively large is Δ2 which is larger than the above-described difference Δ1.

Therefore, when the induction motor 101 having a relatively large allowable current range is used, when the difference between the low resolution detection value L and the high resolution detection value H becomes relatively large as shown in FIG. 3D as an example. In addition, when the control unit 106 switches the low resolution detection value L and the high resolution detection value H as described above, the torque of the induction motor 101 changes greatly. This is the explanation of the second cause.

In the above description, the low resolution detected by the low resolution detection unit 201 and the high resolution detection unit 202 included in the first phase current detection unit 102 respectively indicates that the torque greatly changes due to the first cause. The mismatch occurring between the detection value L and the high resolution detection value H has been described as an example. However, the low resolution detection value L and the high resolution detection value detected by the low resolution detection unit 201 and the high resolution detection unit 202 included in the second phase current detection unit 103 to the third phase current detection unit 104, respectively. Needless to say, there may be a discrepancy with H due to the same first cause.

In the above description, the low resolution detected by the low resolution detection unit 201 and the high resolution detection unit 202 included in the first phase current detection unit 102 respectively indicates that the torque greatly changes due to the second cause. The difference generated between the detection value L and the high resolution detection value H has been described as an example. However, the low resolution detection value L and the high resolution detection value detected by the low resolution detection unit 201 and the high resolution detection unit 202 included in the second phase current detection unit 103 to the third phase current detection unit 104, respectively. Needless to say, there may be a difference from H due to the same second cause.

As is clear from the above description, when the control unit 106 switches between the low resolution detection value L and the high resolution detection value H, the torque of the induction motor 101 is caused by the first cause and the second cause described above. It will change greatly. For example, when the induction motor 101 is used to generate a driving force for running the host vehicle, the torque change caused by the first cause and the second cause described above becomes the vibration of the host vehicle. Will be transmitted to the passenger.

In the present embodiment, as described above, the detection range of the low resolution detection unit 201 is the same as the allowable current range of the induction motor 101. If the amplification factor of the amplification unit 401 is set higher than the amplification factor of the amplification unit 301, the digital value converted by the AD converter 302 is not saturated as described above as the current flowing through the induction motor 101 increases. Nevertheless, the digital value converted by the AD converter 402 is saturated. That is, in the present embodiment, the low resolution detection unit 201 accurately measures all currents within the allowable current range of the induction motor 101 with low resolution, and the high resolution detection unit 202 performs relative measurement within the allowable current range of the induction motor 101. In particular, the current flowing in a low range is measured with high resolution more accurately and accurately.

As described above, the torque of the induction motor 101 may greatly change due to the first cause and the second cause. Therefore, when the control unit 106 according to the present embodiment determines and switches the value of the current used when performing PWM control from the low resolution detection value L and the high resolution detection value H, the control unit 106 changes the current value from one to the other. Change gradually to value. FIG. 4 is a diagram for explaining a method of gradually changing the current value used by the control unit 106 for PWM control between the low resolution detection value L and the high resolution detection value H. FIG. 4 shows, as an example, a case where the current value used by the control unit 106 for PWM control is gradually changed from the high resolution detection value H to the low resolution detection value L and switched. In FIG. 4, as an example of the low resolution detection value L and the high resolution detection value H switched by the control unit 106, the low resolution detection unit 201 and the high resolution detection unit included in the first phase current detection unit 102. A low-resolution detection value L and a high-resolution detection value H detected at 202 are shown.

When the control unit 106 switches the current value used for the PWM control between the low resolution detection value L and the high resolution detection value H, the respective values are gradually changed by weighted averaging. More specifically, when the control unit 106 switches between the low-resolution detection value L and the high-resolution detection value H by gradually changing the calculation, the control unit 106 performs an operation represented by the following formula.

In the above equation (1), S is a current value gradually changed for use in PWM control, λ is a coefficient, L is the aforementioned low resolution detection value L, and H is the above high resolution detection value H. As illustrated in FIG. 5 as an example, when the switching start time Ts1 for switching from the high resolution detection value H to the low resolution detection value L has arrived, the control unit 106 starts the calculation represented by the above formula (1), The current value used for the PWM control is gradually changed from the high resolution detection value H to the low resolution detection value L. Here, when the switching start time Ts1 for switching from the high resolution detection value H to the low resolution detection value L (hereinafter simply referred to as the switching start time Ts1) has arrived, the rotation speed is the low rotation speed described above, Further, this corresponds to the state where the torque target value is the low torque target value described above and the rotational speed is the high rotational speed described above or the torque target value is the high torque target value described above.

When the switching start time Ts1 arrives, the control unit 106 gradually increases the above-mentioned λ from 0 to 1 as shown in FIG. 5 until the switching end time Te1 arrives. Then, the current value S used for the PWM control is sequentially calculated. The controller 106 uses the calculated current value S for PWM control while sequentially calculating the current value S. Thereby, as is clear from the above formula (1), the control unit 106 determines the value of the current used for PWM control from the time when the switching start time Ts1 arrives until the time when the switching end time Te1 arrives. Switching can be performed while gradually changing from H to a low resolution detection value L. When the switching end time Te1 arrives and the switching ends, the control unit 106 performs PWM control using the low resolution detection value L.

Note that, unlike the case described above with reference to FIG. 5, the control unit 106 also switches the current value used for PWM control from the low resolution detection value L to the high resolution detection value H. Perform the operation indicated by. More specifically, when the switching start time Ts2 for switching from the low resolution detection value H to the high resolution detection value L has arrived, the control unit 106 starts the calculation represented by the above formula (1) and uses it for PWM control. The current value is gradually changed from the low resolution detection value L to the high resolution detection value H. Here, when the switching start time Ts2 for switching from the low resolution detection value L to the high resolution detection value H has arrived (hereinafter simply referred to as the switching start time Ts2), the rotation speed is the high rotation speed described above or the torque target. This corresponds to a state where the value is the aforementioned high torque target value and the rotational speed is the aforementioned low rotational speed and the torque target value is the aforementioned low torque target value.

When the switching start time Ts2 arrives, the control unit 106 gradually decreases the above-described λ from 1 to 0, unlike the case described above with reference to FIG. 5 until the switching end time Te2 arrives. The current value S used for the PWM control is sequentially calculated by performing the calculation represented by the above formula (1). The controller 106 uses the calculated current value S for PWM control while sequentially calculating the current value S. As a result, as in the case of switching from the high resolution detection value H to the low resolution detection value L described above, the value used for the PWM control after the switching start time Ts2 arrives and until the switching end time Te2 arrives. Switching can be performed while gradually changing from the low resolution detection value L to the high resolution detection value H.

In addition, after the control part 106 complete | finishes switching to either one of the low resolution detection value L and the high resolution detection value H, it is the value after switching (low resolution detection value L or high resolution detection value H). May be used directly, or a value calculated by continuing the calculation represented by the mathematical formula (1) may be used. To continue the calculation represented by the above formula (1), specifically, after switching to the low resolution detection value L, the calculation is continued by setting λ to 1, and after switching to the high resolution detection value H, λ This means that the calculation is continued with 0 being set to 0.

The above is the description of the method in which the control unit 106 according to the present embodiment switches the low resolution detection value L and the high resolution detection value H while gradually changing them. In the above description, the low-resolution detection unit included in the first phase current detection unit 102 is used to describe a method of gradually changing the low-resolution detection value L and the high-resolution detection value H that are switched by the control unit 106. Only the low resolution detection value L and the high resolution detection value H detected by the high resolution detection unit 201 and the high resolution detection unit 202 have been described with reference to FIG. However, when the control unit 106 according to the present embodiment switches the low resolution detection value L and the high resolution detection value H, the low resolution detection value L and the high resolution detection value detected for each of the phase current detection units, respectively. The current value S is sequentially calculated for each phase current detection unit using H in the calculation represented by the above formula (1). Then, the control unit 106 sequentially calculates the current value S for each phase current detection unit, and applies the calculated current value S to the PWM control as the current value detected by each phase current detection unit. Use.

Also, the period from the switching start time Ts1 to the switching end time Te1 and the period from the switching start time Ts2 to the switching end time Te2 may be periods of any arbitrary length.

Next, processing of the control unit 106 according to the present embodiment will be described with reference to the flowchart shown in FIG. Note that the processing shown in the flowchart of FIG. 5 is started when power supply is started to the current switching device 1 according to the present embodiment, and is ended when power supply is stopped. For example, when the current switching device 1 according to the present embodiment is mounted on the host vehicle, the ignition switch of the host vehicle is turned on, and power supply to the current switching device 1 is started as shown in the flowchart of FIG. The process is terminated when the ignition switch is turned off and the power supply to the current switching device 1 is stopped. This is the same as the processing for PWM control processed by the control unit 106 in parallel with the processing shown in the flowchart shown in FIG. 5 as described above.

In step S101, the control unit 106 determines whether the rotation speed of the rotor of the induction motor 101 is the low rotation speed described above or the high rotation speed described above. An example of specific processing in step S101 will be described. In step S101, the control unit 106 acquires the rotation speed signal V generated by the rotation speed detection unit 105, and the rotation speed indicated by the acquired rotation speed signal V. Is less than the above-mentioned threshold value th1. When the control unit 106 determines in step S101 that the rotation speed is less than the threshold th1, the control unit 106 determines that the rotation speed is a low rotation speed and advances the process to step S102. On the other hand, when determining in step S101 that the rotation speed is not less than the threshold value th1, the control unit 106 determines that the rotation speed is a high rotation speed and advances the process to step S104.

In step S102, the control unit 106 determines whether the torque target value given from a generating unit (not shown) is the above-described low torque target value or the above-described high torque target value. An example of specific processing in step S102 will be described. In step S101, the control unit 106 acquires a torque target signal To generated by a generation unit (not shown), and a torque target value indicated by the acquired torque target signal To. Is less than the threshold value th2. When the control unit 106 determines in step S102 that the torque target value is less than the threshold value th2, the control unit 106 determines that the torque target value is a low torque target value, and advances the process to step S103. On the other hand, when it is determined in step S102 that the torque target value is not less than the threshold value th2, the control unit 106 determines that the torque target value is a high torque target value, and advances the process to step S104.

In step S103, the control unit 106 determines whether or not the current value used for PWM control is the high-resolution detection value H. An example of a specific process in step S103 will be described. In step S103, the control unit 106 recognizes and recognizes the value of the current used in the parallel PWM control process as described above. It is determined whether or not the value of the measured current is the high resolution detection value H. When the control unit 106 determines in step S103 that the current value used for the PWM control is not the high resolution detection value H, the control unit 106 proceeds to step S105. On the other hand, when the control unit 106 determines in step S103 that the current value used for PWM control is the high-resolution detection value H, the process returns to step S101.

In step S104, the control unit 106 determines whether or not the current value used for PWM control is the low-resolution detection value L. An example of a specific process in step S104 will be described. In step S104, the control unit 106 recognizes the current value used in the parallel PWM control process as described above, It is determined whether or not the recognized current value is the low resolution detection value L. When the control unit 106 determines in step S103 that the current value used for PWM control is not the low resolution detection value L, the control unit 106 proceeds to step S105. On the other hand, when the control unit 106 determines in step S103 that the current value used for the PWM control is the low resolution detection value L, the control unit 106 returns the process to step S101.

In step S105, the control unit 106 switches the current value used for the PWM control between the low resolution detection value L and the high resolution detection value H by the above-described method. An example of a specific process in step S105 will be described. When the control unit 106 determines in step S105 that the process has proceeded from the process in step S103 to step S105, the switching start time Ts2 has been reached. As described above, the current value used for the PWM control is switched while gradually changing from the low resolution detection value L to the high resolution detection value H as described above. The reason why the control unit 106 can determine that the aforementioned switching start time Ts2 has arrived when the process proceeds from step S103 to step S105. The control unit 106 can advance the process from step S103 to step S105 because it is determined in step S101 that the rotation speed is a low rotation speed, and in step S102, the torque target value is a low torque target. Only when it is determined that there is. The control unit 106 can determine that the current value used for PWM control in step S103 is not the high resolution detection value H. The control unit 106 that repeats the processing shown in the flowchart of FIG. Is a time when the current value used for the PWM control is already switched to the low resolution detection value L because it is determined that the rotational speed is high or the torque target value is high.

That is, when the control unit 106 proceeds from step S103 to step S105, the low rotational speed and the low torque target value are obtained from the state of the high rotational speed or the high torque target value as described above. When Therefore, when the processing proceeds from step S103 to step S105, the control unit 106 determines that the above-described switching start time Ts2 has arrived, and determines the current value used for PWM control by the above-described method using the low-resolution detection value L. Is switched while gradually changing from 1 to the high-resolution detection value H.

On the other hand, if the control unit 106 determines in step S105 that the process has proceeded from step S104 to step S105, the control unit 106 determines that the switching start time Ts1 has been reached, and performs PWM control as described above. The current value to be used is switched while gradually changing from the low resolution detection value L to the high resolution detection value H. The reason why it can be determined that the above-described switching start time Ts1 has arrived when the control unit 106 proceeds from step S104 to step S105. The reason for this is that the control unit 106 can proceed from step S104 to step S105 because it is determined in step S101 that the rotation speed is a high rotation speed, or in step S102, torque is determined. Only when it is determined that the target value is a high torque target. The control unit 106 can determine that the current value used for the PWM control in step S104 is not the low resolution detection value L. The control unit 106 that repeats the processing shown in the flowchart of FIG. , When it is determined that the rotation speed is low and the target torque value is low, and the current value used for PWM control has already been switched to the high resolution detection value H.

That is, when the control unit 106 advances the process from step S104 to step S105, the low rotational speed and the low torque target value are changed to the high rotational speed or the high torque target value as described above. When Therefore, when the process proceeds from step S104 to step S105, the control unit 106 determines that the above-described switching start time Ts1 has arrived, and determines the current value used for the PWM control by the above-described method using the high-resolution detection value H. To low resolution detection value L.

When the process of step S105 is completed, the control unit 106 returns the process to step S101.

The above is the description of the current switching device 1 according to the present embodiment. The current switching device 1 according to the present embodiment uses a low-resolution detection value L and a high-resolution detection value H detected by the first phase current detection unit 102 to the third phase current detection unit 104, respectively, to detect a phase current. It is used for PWM control by switching while gradually changing each part. Therefore, according to the current switching device 1 according to the present embodiment, it is possible to eliminate a large change in the torque of the induction motor 101 that occurs when switching between the low resolution detection value L and the high resolution detection value H. For example, when the induction motor 101 according to the present embodiment is mounted on the host vehicle, it is caused by a large change in the torque of the induction motor 101 that occurs when switching between the low resolution detection value L and the high resolution detection value H. It is possible to prevent the vibration of the own vehicle from being transmitted to the passenger.

Further, according to the current switching device 1 according to the present embodiment, when the rotation speed of the induction motor 101 is low and the torque target value is the low torque target value, the high resolution detected by each phase current detection unit. Since PWM control is performed based on the detected value H, torque can be controlled smoothly. On the other hand, according to the current switching device 1 according to the present embodiment, when the rotation speed of the induction motor 101 is a high rotation speed or the torque target value is a high torque target value, the low resolution detected by each phase current detection unit. Since PWM control is performed based on the detection value L, it is possible to prevent PWM control based on a saturated inaccurate value.

Note that the control unit 106 according to the present embodiment typically includes an integration of a CPU (Central Processing Unit), an LSI (Large Scale Integration), a microcomputer, and the like that can interpret and execute the above-described control and processing programs. It may be realized by a circuit. Further, when the control unit 106 according to the present embodiment is realized by the above-described integrated circuit, an electronic circuit capable of realizing the functions of the first phase current detection unit 102 to the third phase current detection unit 104 in the integrated circuit. May be integrated.

In the description of the first embodiment, the case where the induction motor 101 is a three-phase AC induction motor has been described as an example. However, if the control unit 106 can control the torque based on the flowing current, the induction motor is used. 101 may be any electric motor. In addition, the motor that can be used as the induction motor 101 is a motor having two or less phases or a motor having four or more phases by increasing or decreasing the number of phase current detection units according to the phase of the motor used as the induction motor 101. Various electric motors can be used.

In the first embodiment, the control unit 106 performs PWM control. However, if the torque of the induction motor 101 can be controlled based on the current flowing through the induction motor 101, PFM (Pulse Frequency Modulation) is used. Other control methods such as control may be used.

In addition, the gain of the amplification unit 301 included in each of the first phase current detection unit 102 to the third phase current detection unit 104 according to the first embodiment is calculated by the control unit 106 using the torque of the induction motor 101. As long as it can be controlled as described in the first embodiment, the amplification factors may be the same or different from each other.

In the first embodiment, the control unit 106 has been described as performing control according to the rotation speed of the rotor of the induction motor 101. However, the control unit 106 is based on the rotation speed of the rotor of the induction motor 101. As described in the first embodiment, the control may be performed while switching between the low resolution detection value L and the high resolution detection value H.

Further, in the first embodiment, the current values detected by the two detection units of the low resolution detection unit 201 and the high resolution detection unit 202 are switched while being gradually changed by weighted averaging. However, in another embodiment, the current values detected by the three or more detection units may be switched while being weighted and averaged in order.

In the first embodiment, the weighted average is used when the current values detected by the two detection units of the low resolution detection unit 201 and the high resolution detection unit 202 are gradually changed. However, in another embodiment, it may be gradually changed by a method using other mathematical expressions such as a quadratic function using the current value detected by each detection unit as a variable.

Further, as a specific example of the allowable voltage range of the AD converter 302 and the AD converter 402 included in each of the first phase current detection unit 102 to the third phase current detection unit 104 according to the first embodiment, 0V-5V etc. are mentioned. A specific example of the resolution of each of the AD converter 302 and the AD converter 402 is 10 bits (1024 steps from 0 to 1023).

In the first embodiment, the case where the value of the current flowing in each phase of the induction motor 101 is detected with low resolution and high resolution has been described. However, in another embodiment, other types of values such as a rotation speed or a rotation speed calculated based on the speed signal Vs generated by the resolver or the rotary encoder described above are detected by a plurality of detection units. When detecting, the values detected by the respective detection units may be switched while being gradually changed as described in the first embodiment.

In the first embodiment, a case has been described in which the current flowing in each phase of the induction motor 101 is amplified and then converted into a digital value to detect each with low resolution and high resolution. However, in another embodiment, for example, when detecting the number of rotations of the induction motor 101, a first known method based on the width of a pulse generated by a rotary encoder or the like, and a rotary encoder per unit time are used. The number of rotations may be obtained by the second conventionally known method based on the number of edges of the pulse generated by the above method. In this case, when the rotational speed is relatively low, the rotational speed obtained by the above-described first conventional well-known method is used, and when the rotational speed is relatively high, the rotational speed obtained by the above-described second conventional well-known technique. To use. And when switching the rotation speed calculated | required by the mutual method, you may switch, changing gradually, as demonstrated in 1st Embodiment. That is, the same type of detection amount detected by different methods may be switched while being gradually changed as described in the first embodiment.

In addition, the induction motor 101 according to the first embodiment may be an electric motor for generating a driving force for running the host vehicle, or an electric motor for controlling the driving force of the rear wheels of the host vehicle. May be.

In the first embodiment of the present invention, as described above, when the low-resolution detection value L and the high-resolution detection value H are switched, the torque greatly changes, for example, for driving the host vehicle. In the case of reducing the vibration generated when controlling the induction motor 101 used for generating the driving force, a higher reduction effect can be achieved. More specifically, an induction motor 101 having an allowable maximum current of 200 A (ampere) to 1000 A (ampere) or a maximum power consumption (wattage) of 20 kW (kilowatt) to 200 kW (kilowatt) is used. Thus, a remarkably high reduction effect can be achieved. Further, the induction motor that operates at the above-described maximum allowable current or maximum power consumption is typically mounted on a passenger car (a normal passenger car or a small passenger car) among moving objects such as automobiles.

Although the present invention has been described in detail above, the above description is merely an example of the present invention in all respects, and is not intended to limit the scope thereof. It goes without saying that various improvements and modifications can be made without departing from the scope of the present invention.

The present invention can reduce a large change in torque generated when controlling an electric motor, and can be used for, for example, a current switching device for controlling an induction motor mounted on a moving body such as an automobile.

DESCRIPTION OF SYMBOLS 1 Current switching device 101 Induction motor 102 1st phase current detection part 103 2nd phase current detection part 104 3rd phase current detection part 105 Rotational speed detection part 106 Control part 107 Drive part 201 Low resolution detection part 202 High resolution Detection unit 301 Amplification unit 302 AD converter 401 Amplification unit 402 AD converter 403 Correction unit

Claims

First current detection means for detecting current flowing in each phase of the induction motor as a first current;
Second current detection means for detecting the current as a second current with higher resolution than the first current detection means;
Control means for controlling the torque of the induction motor to be a target value based on at least one of the first current and the second current;
And a switching means for switching the current when the control means controls the induction motor between the first current and the second current while gradually changing from one current to the other current. , Current switching device.
The switching means changes the current when the control means controls the induction motor by gradually changing between the first current and the second current, and switches the first current and the second current. The current switching device according to claim 1, wherein the current is gradually changed by weighted averaging.
A rotation speed detecting means for detecting the rotation speed of the rotor of the induction motor;
The control means has the rotation speed detected by the rotation speed detection means less than a predetermined first threshold value, and the target value is less than a predetermined second threshold value. The current switching device according to claim 1, wherein the induction motor is controlled based on the second current.
A rotation speed detecting means for detecting the rotation speed of the rotor of the induction motor;
The control means, when the rotational speed detected by the rotational speed detection means is not less than a predetermined first threshold, or when the target value is not less than a predetermined second threshold, The current switching device according to claim 1, wherein the induction motor is controlled based on the first current.
The current switching device according to claim 2, wherein the induction motor generates a driving force for driving the vehicle.
The induction motor is mounted on a passenger car,
2. The current switching device according to claim 1, wherein the control means controls a torque of the induction motor having an allowable maximum current of 200 amperes to 1000 amperes.
The induction motor is mounted on a passenger car,
The current switching device according to claim 1, wherein the control means controls the torque of the induction motor having a maximum power consumption of 20 kilowatts to 200 kilowatts.
A first current detection step of detecting a current flowing in each phase of the induction motor as a first current;
A second current detection step for detecting the current as a second current with a higher resolution than when the current is detected in the first current detection step;
A control step of controlling the torque of the induction motor to be a target value based on at least one of the first current and the second current;
A switching step of switching the current when the control means controls the induction motor between the first current and the second current while gradually changing from one current to the other current. , Switching method.