JP4506534B2 - In-vehicle motor controller - Google Patents

Description

  The present invention relates to an in-vehicle motor control device for performing variable speed control of a motor mounted on a vehicle.

  When performing variable speed control of a motor, it is common to use a motor control device including an inverter circuit. As an example of this type of motor control device, a PWM signal is generated by comparing a target voltage signal VS for commanding a target rotational speed with a triangular wave signal VT as a carrier signal, as shown in FIG. The thing of the structure which performs switching control of an inverter circuit with a PWM signal is known (for example, refer patent document 1).

Further, in the conventional motor control device, it is also common to feedback control the motor rotation speed. Specifically, a sensor (for example, a Hall IC) that detects the actual rotational speed of the motor, a signal conversion means that generates a feedback voltage signal at a level corresponding to the actual rotational speed of the motor based on the sensor output, and feedback A gain control amplifier that generates a differential voltage signal obtained by amplifying a deviation between the voltage signal for use and the target voltage signal VS with a predetermined gain, and the differential voltage signal is used for comparison with the triangular wave signal VT. Has been done. According to this configuration, when a difference occurs between the target rotational speed of the motor and the actual rotational speed, the pulse duty ratio of the PWM signal is changed in a direction to reduce the difference, whereby the motor torque is adjusted and the actual rotational speed is adjusted. Feedback control is performed so that the number becomes the target rotational speed.
JP 2001-2111679 A

  In the conventional motor control device provided with the feedback means as described above, the expansion of the control error between the target rotational speed and the actual rotational speed of the motor is suppressed under a situation where the target rotational speed gradually changes. It is possible to perform stable feedback control in a state. On the other hand, when the target rotational speed falls rapidly, the deviation between the feedback voltage signal and the target voltage signal VS corresponding to the target rotational speed becomes a transiently expanded state, so that the actual rotation of the motor During the period until the number drops below a certain value, the level of the differential voltage signal output from the gain control amplifier becomes smaller than the level of the triangular wave signal VT to be compared, and the pulse duty ratio of the PWM signal becomes 0%. turn into. In other words, since no motor torque is generated during such a period, the motor is rotated by inertia, and the time until the actual rotational speed reaches the target rotational speed is unnecessarily prolonged. There arises a problem that accuracy related to feedback control of the motor rotation speed is deteriorated.

  In order to deal with such a situation, it is conceivable to incorporate a microcomputer for controlling the rotational speed of the motor in the motor control device. However, in such a configuration in which a microcomputer that is inevitably expensive is incorporated, a new problem arises in that an increase in cost is unavoidable. In addition, since the operating environment temperature of the microcomputer itself is limited, if it is configured to be installed in a harsh temperature environment, such as an in-vehicle motor control device, the operation reliability due to an increase in the ambient temperature. The problem of incurring a decrease in performance also occurs.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an on-vehicle motor control device that can realize improvement in control accuracy and operation reliability of motor rotation speed with a configuration that suppresses an increase in cost. Is to provide.

  According to the means of the present invention, the difference voltage signal obtained by amplifying the deviation between the rotational speed signal of the voltage level corresponding to the actual rotational speed of the motor and the target voltage signal for instructing the target rotational speed of the motor is obtained from the amplifier circuit. Is output. Therefore, the voltage level of the differential voltage signal increases as the difference between the actual rotational speed of the motor and the target rotational speed increases. The comparison circuit generates a PWM signal by comparing the difference voltage signal with a carrier signal having a predetermined frequency and supplies the PWM signal to the control circuit. The control circuit supplies the given PWM signal to the inverter circuit with a predetermined value. By supplying at the timing, the motor is rotated in a predetermined direction.

  When the target rotational speed is suddenly reduced from such a state, the difference between the target rotational speed and the actual rotational speed of the motor transiently expands, and the voltage of the differential voltage signal output from the amplifier circuit The level will drop temporarily. Thereby, when the voltage level of the difference voltage signal becomes less than the lower limit voltage of the carrier signal, the pulse duty ratio of the PWM signal output from the comparison circuit becomes 0%. At this time, the voltage detection circuit outputs a switching command signal, and the signal generation circuit generates a correction voltage difference signal having a level higher than the lower limit voltage of the carrier signal. Therefore, in the second comparison circuit, a second PWM signal having an effective pulse width is generated by comparing the correction voltage difference signal and the carrier signal.

  During the period when the switching command signal is output from the voltage detection circuit as described above, the switching circuit gives the second PWM signal from the second comparison circuit to the control circuit instead of the PWM signal from the comparison circuit. In response to this, the control circuit controls the motor to generate reverse torque when the inverter circuit is driven by the second PWM signal. As a result of such control, braking is applied to the motor and its actual rotational speed rapidly decreases, so that the actual rotational speed of the motor quickly decreases to the target rotational speed.

  When the difference between the target rotational speed and the actual rotational speed of the motor is reduced to a predetermined value or more, the voltage level of the differential voltage signal output from the amplifier circuit returns to the carrier voltage lower than the lower limit voltage. For this reason, the voltage detection circuit stops outputting the switching command signal, and accordingly, the switching circuit returns to the state in which the PWM signal having the effective pulse width from the comparison circuit is supplied to the control circuit. Based on the PWM signal, the motor returns to a steady state where the rotational speed control of the motor is performed.

  As a result of the control described above, the control accuracy of the motor rotation speed is improved, and it is not necessary to incorporate a microcomputer to control the motor rotation speed as in the conventional configuration. It is possible to improve the operational reliability in a temperature environment and to suppress an increase in cost.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows a basic configuration of an in-vehicle motor control device according to this embodiment. In FIG. 1, a motor 1 to be controlled is constituted by a three-phase brushless DC motor (permanent magnet synchronous motor), for example, a drive source of an electric control device for controlling the opening / closing timing of a valve cam for a vehicle engine. It is provided as.

  A PWM control type inverter circuit 2 provided to drive the motor 1 at a variable speed has six N-channel type power MOSFETs Q1 to Q6 connected in a three-phase bridge between a power supply terminal + V and a ground terminal. The U, V, W phase coils of the motor 1 are fed by a 120 ° energizing rectangular wave drive system. Each MOSFET Q1 to Q6 is connected or integrally provided with a free-wheeling diode (not shown) having the polarity shown in the figure. A π-type LC filter circuit 3 is connected between the power supply terminal + V and the ground terminal.

  The three Hall ICs 1u, 1v, and 1w provided for detecting the rotational position (rotor position) of the motor 1 output position detection signals Su, Sv, and Sw having phases different from each other by 120 °. The position detection signals Su, Sv, Sw are applied to the control circuit 4 having the function of the rotation speed detection circuit in the present invention.

  The control circuit 4 recognizes the rotation direction of the motor 1 based on the input position detection signals Su, Sv, Sw, and outputs a rotation speed signal VN having a voltage level proportional to the actual rotation speed of the motor. ing. Further, the control circuit 4 determines the energization timing of the MOSFETs Q1, Q3, Q5 constituting the upper arm of the inverter circuit 2 based on the recognition result of the rotation direction of the motor 1 and the input timing of each position detection signal Su, Sv, Sw. A gate control signal group for each U, V, and W phase to be determined, and a gate control signal group for each U, V, and W phase that determines the energization timing of the MOSFETs Q2, Q4, and Q6 constituting the lower arm are set in a predetermined pattern (motor 1 is a pattern for rotating forwardly or a pattern for rotating backwardly). In this case, although shown in a simplified manner in FIG. 1, the gate terminals of the upper arm MOSFETs Q1, Q3, and Q5 are directly supplied with the gate control signals for the MOSFETs Q2, Q4 of the lower arm. The gate terminals of Q6 are supplied with respective gate control signals for them via an AND circuit 5 (actually, three are provided for each phase) constituting a part of the control circuit 4. It has become.

  Further, the control circuit 4 includes a rotation direction switching terminal T. With the low level signal being input to the rotation direction switching terminal T, the output pattern of the gate control signal for each of the U, V, and W phases is set. The motor 1 is set to the normal rotation pattern (in order of U phase → V phase → W phase), and a high level signal (corresponding to the switching command signal in the present invention) is input to the rotation direction switching terminal T. In this state, the output pattern of the gate control signal for each of the U, V, and W phases is set to the reverse rotation pattern of the motor 1 (in order of W phase → V phase → U phase).

  A gain control amplifier 6 (corresponding to an amplifier circuit) is a differential voltage obtained by amplifying a deviation between a target voltage signal VS for instructing a target rotational speed of the motor 1 and a rotational speed signal VN from the control circuit 4 with a predetermined gain. A signal Vo is generated. That is, when the gain of the gain control amplifier 6 is G, Vo = VS + G (VS−VN). The target voltage signal VS is given from, for example, an external vehicle ECU (not shown), and is a voltage level signal proportional to the target rotational speed of the motor 1.

  The first comparator 7 (corresponding to the comparison circuit) receives the differential voltage signal Vo from the gain control amplifier 6 at the non-inverting input terminal (+) and is a triangular wave output from an oscillation circuit (not shown) at the inverting input terminal (−). It is connected so as to receive the signal VT, and is configured to give a PWM signal generated based on the comparison to the signal selector switch 8 (corresponding to a switching circuit). As shown in FIG. 2, the triangular wave signal VT is a signal whose upper limit voltage VTU (upper peak value) is set to 4 V, for example, and lower limit voltage VTL (lower peak value) is set to 2.5 V, for example.

  The signal changeover switch 8 is actually configured using a semiconductor element, and the PWM signal from the first comparator 7 is supplied to one input terminal of the AND circuit 5 (the other input terminal is connected to the control circuit). 4 is inputted to one of the input terminals of the AND circuit 5 and the second PWM signal from the second comparator 9 (corresponding to the second comparison circuit) to be described later. It can be switched to any of the applied reverse rotation mode positions.

  Specifically, the signal changeover switch 8 switches to the normal rotation mode position in a state where a low level signal is output from the third comparator 10 (corresponding to a voltage detection circuit), and the high level signal (switching) from the third comparator 10. It is configured to switch to the reverse rotation mode position when the command signal is output.

  The third comparator 10 receives the difference voltage signal Vo from the gain control amplifier 6 at the inverting input terminal (−), and has a lower limit voltage VTL (= 2.5 V) of the triangular wave signal VT at the non-inverting input terminal (+). Is connected to a voltage signal generation circuit (for example, a peak hold circuit) (not shown). In this case, the third comparator 10 is provided with hysteresis, and as the providing means, for example, a two-level threshold is set, and the analog switch is switched based on the H / L state of the comparator output. A method of applying hysteresis according to the operation or a method of connecting a known feedback resistor is conceivable.

  Therefore, when Vo ≧ VTL (that is, when the differential voltage signal Vo is 2.5 V or more), a low level signal is output from the third comparator 10 and the signal selector switch 8 is set to the normal rotation mode position. When the voltage is switched and Vo <VTL (that is, when the differential voltage signal Vo is lower than 2.5V), a high level signal is output from the third comparator 10 and the signal selector switch 8 is switched to the reverse rotation mode position. It will be. However, in practice, a predetermined hysteresis voltage is involved in the output inversion operation of the third comparator 10 as described above. The output signal from the third comparator 10 is also supplied to the rotation direction switching terminal T of the control circuit 4.

  The loopback amplifier 11 (corresponding to the signal generation circuit) with the amplification factor set to “1” is provided to loop back the differential voltage signal Vo from the gain control amplifier 6 with reference to the lower limit voltage VTL of the triangular wave signal VT. Yes, the corrected differential voltage signal Vo2 output from now on is obtained by Vo2 = 5-Vo.

  The second comparator 9 is connected so that the non-inverting input terminal (+) receives the correction difference voltage signal Vo2 from the folding amplifier 11 and the inverting input terminal (−) so as to receive the triangular wave signal VT. The second PWM signal generated based on the above is provided to the signal changeover switch 8.

Next, the operation of the circuit configuration will be described with reference to FIGS.
That is, the gain control amplifier 6 outputs a difference voltage signal Vo corresponding to a deviation between the target voltage signal VS and the rotation speed signal VN related to the motor 1, and the difference voltage signal Vo is 2.5V (a triangular wave signal VT). In a state where the voltage is lower than the lower limit voltage (VTL), the signal selector switch 8 is switched to the normal rotation mode position by the low level signal output from the third comparator 10 and the output of the first comparator 7 is applied to the AND circuit 5. The Further, in this state, as shown in FIG. 3A, the correction difference voltage signal Vo2 from the folding amplifier 11 is less than 2.5 V, so that the first comparator 7 generates a PWM signal having an effective pulse width. Although generated, the second comparator 9 generates a second PWM signal having a pulse duty ratio of 0%. Further, in this case, since the low level signal output from the third comparator 10 is applied to the rotation direction switching terminal T of the control circuit 4, the control circuit 4 is provided with gates for U, V, and W phases. The output pattern of the control signal is set to the pattern for forward rotation of the motor 1.

  Accordingly, the MOSFETs Q1, Q3, Q5 constituting the upper arm of the inverter circuit 2 are turned on / off by the gate control signal of the normal rotation pattern output from the control circuit 4, and the MOSFETs Q2, Q4, Q6 is turned on and off by the logical product signal of the gate control signal of the positive rotation pattern output from the control circuit 4 and the PWM signal from the first comparator 7, and the motor 1 responds to the target voltage signal VS. Is rotated forward in a feedback-controlled state so that the number of rotations corresponds to.

  When the target rotational speed is suddenly decreased from such a control state as shown in FIG. 4A, the deviation from the rotational speed signal VN is transient as the target voltage signal VS decreases rapidly. The voltage level of the differential voltage signal Vo output from the gain control amplifier 6 temporarily decreases to less than 2.5 V as shown in FIG. 4B.

  Then, since the high level signal is output from the third comparator 10 during the decrease period, the signal selector switch 8 is switched to the reverse rotation mode position, and the second PWM signal from the second comparator 9 is converted to the AND circuit 5. It becomes a state to give. Thus, in the state where the difference voltage signal Vo is less than 2.5V, the corrected difference voltage signal Vo2 from the folding amplifier 11 becomes 2.5V or more as shown in FIG. 7, a PWM signal having a pulse duty ratio of 0% is generated, but the second comparator 9 generates a second PWM signal having an effective pulse width. Further, in this case, since the high level signal is supplied from the third comparator 10 to the rotation direction switching terminal T of the control circuit 4, the control circuit 4 outputs gate control signals for the U, V, and W phases. The pattern is set to the reverse rotation pattern of the motor 1.

  Accordingly, the MOSFETs Q1, Q3, Q5 constituting the upper arm of the inverter circuit 2 are turned on / off by the gate control signal of the reverse rotation pattern output from the control circuit 4, and the MOSFETs Q2, Q4, Q6 is turned on and off by the logical product signal of the reverse rotation pattern gate control signal output from the control circuit 4 and the second PWM signal from the second comparator 9, and in response to this, the motor 1 has a reverse torque ( Braking torque) is generated, and the actual number of revolutions rapidly decreases.

  Thereafter, when the difference between the target rotational speed and the actual rotational speed of the motor 1 is reduced to a predetermined value or more, the voltage level of the differential voltage signal Vo output from the gain control amplifier 6 is equal to or higher than the lower limit voltage VTL of the triangular wave signal VT. To return to. For this reason, the output of the third comparator 10 is inverted to a low level signal, and in response to this, the signal changeover switch 8 sends the PWM signal having the effective pulse width from the first comparator 7 to the AND circuit 5. Since the state is returned to the applied state, the state returns to the steady state where the rotational speed control of the motor 1 is performed based on the PWM signal.

That is, if the difference voltage signal Vo from the gain control amplifier 6 temporarily decreases to less than 2.5 V as the target rotational speed is suddenly lowered, the difference voltage signal Vo, from the first comparator 7 The PWM signal pulse duty ratio, the correction differential voltage signal Vo2 from the loopback amplifier 11, the second PWM signal pulse duty ratio from the second comparator 9, and the drive duty ratio (on / off ratio) of the MOSFETs Q1 to Q6 in the inverter circuit 2 4 (b), (c), (d), (e), and (f), respectively, and change to show transient response characteristics as shown in FIG. 4 (a). As described above, after the actual rotational speed of the motor 1 is suddenly decreased, the motor 1 becomes stable at the target rotational speed.
According to the configuration of the present embodiment, as shown in FIG. 2, the relationship between the rotational speed of the motor 1 and the target voltage signal VS and the rotational speed signal VN is in a state where it extends to the reverse rotational region of the motor 1. Will be.

  In short, according to the configuration of the present embodiment, as a result of performing the control as described above, the control accuracy of the rotational speed of the motor 1 is improved, and the rotational speed control of the motor 1 is controlled as in the conventional configuration. Since it is not necessary to incorporate a microcomputer to perform the operation, it is possible to improve the operation reliability in a severe temperature environment and to suppress an increase in cost.

In addition, the present invention is not limited to the above-described embodiments, and for example, the following modifications or expansions are possible.
The control circuit 4, the gain control amplifier 6, the first comparator 7, the signal changeover switch 8, the second comparator 9, the third comparator 10, the folding amplifier 11, and the like can be configured as a monolithic IC circuit.

Electrical configuration diagram showing one embodiment of the present invention Characteristic diagram showing the relationship between motor speed, target voltage signal and speed signal Waveform diagram for explaining an example of generating a PWM signal Transient response characteristics FIG. 3 equivalent diagram for explaining the conventional configuration

Explanation of symbols

  1 is a motor, 2 is an inverter circuit, 4 is a control circuit (rotation speed detection circuit), 6 is a gain control amplifier (amplification circuit), 7 is a first comparator (comparison circuit), 8 is a signal selector switch (switching circuit), Reference numeral 9 denotes a second comparator (second comparison circuit), 10 denotes a third comparator (voltage detection circuit), and 11 denotes a folding amplifier (signal generation circuit).

Claims (4)

A PWM control type inverter circuit for driving a motor serving as a power source for a vehicle load, and a control circuit for determining a supply timing of a PWM signal to the inverter circuit;
A rotational speed detection circuit for generating a rotational speed signal at a voltage level corresponding to the actual rotational speed of the motor, and a difference obtained by amplifying a deviation between the rotational speed signal and a target voltage signal for commanding the target rotational speed of the motor An amplifier circuit for outputting a voltage signal;
In a vehicle-mounted motor control device comprising a comparison circuit that generates a PWM signal by comparing the difference voltage signal with a carrier signal having a predetermined frequency and supplies the PWM signal to the control circuit.
A voltage detection circuit that outputs a switching command signal when the voltage level of the difference voltage signal is less than the lower limit voltage of the carrier signal;
A signal generation circuit for generating a corrected difference voltage signal having a voltage level higher than the lower limit voltage of the carrier signal in a state where the voltage level of the difference voltage signal is less than the lower limit voltage of the carrier signal;
A second comparison circuit for generating a second PWM signal by comparing the corrected difference voltage signal and the carrier signal;
A switching circuit that switches to a state in which the control circuit is supplied with the second PWM signal from the second comparison circuit instead of the PWM signal from the comparison circuit when the switching command signal is output;
The control circuit controls the motor to generate reverse torque when the inverter circuit is driven by the second PWM signal during the period when the switching command signal is output. Control device. The motor is a three-phase motor;
The control circuit outputs the PWM signal in a normal rotation pattern when outputting the PWM signal, and outputs the second PWM signal in a reverse rotation pattern when outputting the second PWM signal. The in-vehicle motor control device according to claim 1, wherein the motor control device is output. The pattern for forward rotation is a pattern for outputting the PWM signal in the order of U phase → V phase → W phase,
The in-vehicle motor control device according to claim 2, wherein the reverse rotation pattern is a pattern for outputting the second PWM signal in the order of W phase → V phase → U phase. The in-vehicle motor control device according to any one of claims 1 to 3, wherein a hysteresis is given to the lower limit voltage of the carrier signal.

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