JP2009131069A - Motor control unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor control unit capable of estimating a current flowing into a switching device based on the value of current flowing into a battery, and performing excessive current prevention control, based on an estimated value. <P>SOLUTION: This motor control unit (1) controls a current flowing into a brushless motor (M) from the battery (BT) by means of PWM control, based on the duty ratio. This unit includes current detecting devices (7, 11) that detect the battery current value; an estimation method determining device (19) that selects the first estimating method, when the battery current value is larger than a predetermined first determination value; and the duty ratio is larger than a predetermined second determination value, and selects the second estimating method in the other cases, and an estimation motor current value calculating device (20) that calculates the estimated motor current value, based on the battery current value and the duty ratio, when the first estimating method is selected, and uses the battery current value as the estimation motor current value when the second estimating method is selected. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a motor control device that prevents an overcurrent from flowing through a switching circuit of a brushless motor that is PWM-controlled, and more specifically, a motor coil (switching element) based on a current value flowing through a battery and a duty ratio. The present invention relates to a motor control device that estimates the value of a current flowing through the capacitor, determines whether the current value is an overcurrent, and performs overcurrent protection of a switching element.

  The current flowing through the motor coil of the brushless motor is controlled by an inverter circuit. The inverter circuit is composed of a plurality of switching elements, and each switching element is turned on / off to control the current flowing in each phase of the motor coil. However, since the switching element is damaged when an overcurrent flows, the current flowing through each switching element (the current flowing through the motor coil of each phase) is constantly monitored, and the switching element is put into a state where there is a possibility that the overcurrent may flow. It is necessary to limit or cut off the current flowing through.

As means for monitoring the current flowing through each switching element, there is one in which a current detection means is connected to the switching element of each phase to detect the current of each phase (for example, Patent Document 1).
JP 2002-34264 A

  However, the conventional current detection device has a problem that current detection means must be arranged for each phase, and the required number of wirings and circuits increases, and the configuration of the device becomes complicated.

  The present invention has been made in view of such problems, omitting the structure for connecting the current detection means to the switching elements of each phase, and switching elements (motor coils) from the battery current value flowing through the battery. It is an object of the present invention to provide a motor control device that estimates the current flowing through the control element and performs overcurrent prevention control of the switching element based on the estimated current value.

  In order to solve the above problems, a first invention of the present invention is a motor control device (1) for controlling a current flowing from a battery (BT) to a brushless motor (M) by PWM control based on a duty ratio. Current detecting means (7, 11) for detecting a current flowing through the battery as a battery current value; and a first current value when the battery current value is greater than a predetermined first determination value and the duty ratio is greater than a predetermined second determination value. An estimation method determining means (19) for selecting one estimation method, and selecting the second estimation method when the battery current value is equal to or less than the first determination value or the duty ratio is equal to or less than the second determination value; When the second estimation method is selected, the estimated motor current value as the current flowing in the motor coil is calculated based on the battery current value and the duty ratio. And having the estimated motor current value calculating means for re current value and the estimated motor current value (20).

  A second invention is characterized in that, in the first invention, when the estimated motor current value is larger than a predetermined third determination value, the invention has a duty ratio limiting means (16) for limiting the settable range of the duty ratio. To do.

  With this configuration, the current value flowing through the switching circuit can be accurately calculated as an estimated value without directly measuring the current flowing through the switching circuit. Since it is determined whether the current flowing through the switching element is an overcurrent based on the estimated value, the switching element can be reliably protected. Moreover, since the structure which connects an electric current detection means for every phase can be abbreviate | omitted, a number of parts and manufacturing cost can be reduced.

  Hereinafter, an embodiment of a motor control device according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram illustrating a schematic configuration of a motor control device according to the embodiment. In the embodiment, an example in which the motor control device according to the present invention is applied to a three-phase brushless motor mounted as a drive motor of an electric vehicle will be described.

  As shown in FIG. 1, the motor control device 1 is connected to an inverter circuit 2 provided between a motor M of an electric vehicle and an in-vehicle battery BT. The motor M is an outer rotor type brushless motor, and a stator 4 around which a three-phase (U, V, W phase) armature coil 3 is wound and a magnet (illustrated) that is provided to face the stator 4. And a bottomed cylindrical rotor 5 having an inner peripheral wall on the inner peripheral wall. The motor M constitutes an in-wheel motor, for example, with the rotor 5 fixed to the drive wheel of the vehicle. The motor M is provided with a motor rotation angle sensor 6 that detects the rotation angle of the rotor 5. The rotation angle sensor 6 may be, for example, a sensor configured with a magnet and a hall element.

  The inverter circuit 2 is a bridge circuit including, for example, six switching elements (FETs), and is connected to each phase coil of the armature coil 3 and the in-vehicle battery BT. The power supply line connecting the inverter circuit 2 and the in-vehicle battery BT includes a current detection sensor 7 as current detection means for detecting a current flowing from the in-vehicle battery BT to the inverter circuit 2 and a voltage detection for detecting the potential of the in-vehicle battery BT. A sensor 8 is provided.

  The motor control device 1 includes a target output value calculation circuit 10, a current detection circuit 11, a voltage detection circuit 12, a rotation angle detection circuit 13, an output duty determination circuit 14, a regeneration duty determination circuit 15, a motor current limit circuit 16, and a PWM signal generation. The electronic control unit (ECU) includes a circuit 17, an advance control circuit 18, an estimation method determination circuit 19, a current value estimation circuit 20, an inverter control circuit 21, and a memory 22. Each circuit may include a circuit configured using an IC and a circuit configured by CPU program control. Among these circuits, the estimation method determination circuit 19, the current value estimation circuit 20, and the memory 22 constitute a motor current estimation unit 30 that estimates a motor current flowing in each phase coil of the motor M. The motor control device 1 is an inverter circuit based on signals output from an accelerator pedal device 9 to which a driving operation input of an occupant of an electric vehicle is input, a motor rotation angle sensor 6, a current detection sensor 7, and a voltage detection sensor 8. 2 to control the motor M.

  The accelerator pedal device 9 includes a plate-like pedal 9a that is rotatably supported at a substantially central portion, and a rotation angle sensor that is provided on a rotation shaft of the pedal 9a and detects a rotation position of the pedal 9a. The rotation angle sensor is, for example, a potentiometer. In the initial position, the pedal 9a is attached obliquely so as to extend upward toward the vehicle body front side, and is elastically biased so as to maintain the initial position. The accelerator pedal device 9 outputs information on the rotation angle of the pedal 9a detected by the rotation angle sensor to the target output value calculation circuit 10 provided in the motor control device 1 as a driving operation signal.

  The current detection sensor 7 outputs a current detection signal for the current flowing from the in-vehicle battery BT to the inverter circuit 2 to a current detection circuit 11 provided in the motor control device 1. The voltage detection sensor 8 outputs a voltage detection signal for the potential of the in-vehicle battery BT to the voltage detection circuit 12 of the motor control device 1. The motor rotation angle sensor outputs the detected motor rotation angle signal to the rotation angle detection circuit 13 provided in the motor control device 1.

  The target output value calculation circuit 10 performs acceleration or deceleration control based on the value of the driving operation signal from the accelerator device 9. The target output value calculation circuit 10 responds to the rotation angle of the pedal 9a for a driving operation signal that is output when the upper side of the pedal 9a is displaced (rotated) from the initial position to the front side of the vehicle body. For the driving operation signal output when the lower side of the pedal 9a is displaced (rotated) from the initial position to the front side of the vehicle body, the rotation angle of the pedal is controlled. Deceleration control is performed so as to obtain deceleration corresponding to. The target output value calculation circuit 10 outputs an acceleration output signal corresponding to the rotation angle of the pedal 9a to the output duty determination circuit 14 when performing acceleration control, and according to the rotation angle of the pedal 9a when performing deceleration control. The reduced output signal is output to the regeneration duty determination circuit 15.

  Based on the current detection signal output from the current detection sensor 7, the current detection circuit 11 calculates the value of the current flowing from the in-vehicle battery BT to the inverter circuit 2 as the battery current value. Then, the current detection circuit 11 outputs the calculated battery current value to the output duty determination circuit 14, the regeneration duty determination circuit 15, the estimation method determination circuit 19, and the current value estimation circuit 20.

  Based on the voltage detection signal output from the voltage detection sensor 8, the voltage detection circuit 12 calculates the value of the potential of the in-vehicle battery BT as the battery potential value. Then, the voltage detection circuit 12 outputs the calculated battery potential value to the output duty determination circuit 14 and the regeneration duty determination circuit 15.

  The output duty determination circuit 14 includes an acceleration output signal from the target output value calculation circuit 10, a battery current value from the current detection circuit 11, a battery potential value from the voltage detection circuit 12, and a duty from a motor current limit circuit 16 described later. An output duty ratio in drive output control is determined based on the ratio limit signal, and is output to the PWM signal generation circuit 17, the advance angle control circuit 18, the estimation method determination circuit 19, and the current value estimation circuit 20 as an output duty ratio determination signal. .

  The regeneration duty determination circuit 15 determines the regeneration duty ratio in the regeneration control based on the deceleration output signal from the target output value calculation circuit 10, the battery current value from the current detection circuit 11, and the battery potential value from the voltage detection circuit 12. Then, the regeneration duty ratio determination signal is output to the PWM signal generation circuit 17.

  When the PWM signal generation circuit 17 receives the output duty ratio determination signal from the output duty determination circuit 14, the PWM signal generation circuit 17 performs pulse width modulation in the known PWM control for the brushless motor and sets the duty ratio based on the output duty ratio determination signal. A PWM signal for drive control as a corresponding control signal is determined, and this drive control PWM signal is output to the inverter control circuit 21. On the other hand, when the PWM signal generation circuit 17 receives the regeneration duty ratio determination signal from the regeneration duty determination circuit 15, the PWM signal generation circuit 17 similarly determines a PWM signal for regeneration control based on the regeneration duty ratio determination signal. The regeneration control PWM signal is output to the inverter control circuit 21.

  The advance angle control circuit 18 determines an advance angle in known advance angle control for the brushless motor based on the output duty ratio determination signal from the output duty determination circuit 14, and outputs the advance angle signal to the inverter control circuit 21.

  The inverter control circuit 21 controls the inverter circuit 2 based on the PWM signal from the PWM signal generation circuit 17, the advance angle signal from the advance angle control circuit 18, and the rotation position and rotation speed signals output from the rotation angle detection circuit. To do.

  Based on the battery current value output from the current detection circuit 11 and the output duty ratio determination signal output from the output duty determination circuit, the estimation method determination circuit 19 serving as the estimation method determination means of the motor current estimation unit 30 Determine how to estimate the motor current. The estimation method determination circuit 19 receives the first determination value and the second determination value stored in the memory 22 from the memory 22, compares the battery current value with the first determination value, and outputs the output duty ratio determination signal. The duty ratio is compared with the second determination value. When the battery current is larger than the estimated permission current value and the output duty ratio is larger than the estimated permission duty ratio, the estimation method determination circuit 19 selects the first estimation method and uses the first estimation method selection signal as the current value estimation. When the battery current is output to the circuit 20 and the battery current is equal to or less than the estimated permission current value or the output duty ratio is equal to or less than the estimated permission duty ratio, the second estimation method is selected and the second estimation method selection signal is sent to the current value estimation circuit. 20 is output.

When the current value estimation circuit 20 receives the first estimation method selection signal, the current value estimation circuit 20 calculates the motor current value from the following equation 1 based on the battery current value and the output duty ratio of the output duty ratio determination signal.
I _M = I _B / (D + α) (Formula 1)
Here, I _M is an estimated motor current value (A), I _B is a battery current value (A), D is an output duty ratio, and α is a circuit error. The circuit error (α) is stored in advance in the memory 22 and is output from the memory 22 to the current value estimation circuit 20. The current value estimation circuit 20 outputs the calculated motor current value (I _M ) to the motor current limit circuit 16.

On the other hand, when the current value estimation circuit 20 receives the second estimation method selection signal, the battery current value (I _B ) is set as the estimated motor current value (I _M ), and the motor current value (I _M ) is set as the current value estimation circuit 20. Output to the motor current limiting circuit 16.

Motor current limiting circuit 16, the motor current value (I _M), compared with the third determination value as the overcurrent judging value, the motor current value (I _M) is the motor current is greater than the third determination value It is assumed that (I _M ) is abnormal (overcurrent) and the output duty ratio limit signal is output. If the motor current value (I _M ) is equal to or smaller than the third determination value, the motor current (I _M ) is determined to be normal. The ratio determination permission signal is output to the output duty determination circuit 14.

  When the output duty determination circuit 14 receives the duty limit signal from the motor current limit circuit 16, the output duty set circuit 14 sets the settable value of the output duty to a predetermined value (for example, 0% or 50%) or less. On the other hand, when the output duty determination circuit 14 receives the duty determination permission signal from the motor current limit circuit 16, it is within the range of 0 to 100% based on the acceleration output signal, the battery current value, and the battery potential value. To determine the output duty ratio. If the output duty ratio is limited in advance within a predetermined range, the output duty ratio is set to a value within the range.

  Next, the control point of the overcurrent prevention control of the motor M by the motor control device 1 according to the embodiment will be described. FIG. 2 is a flowchart showing main control of the motor control device according to the embodiment. FIG. 3 is a flowchart showing the estimated motor current value calculation control of the motor control device according to the embodiment. FIG. 4 is a flowchart showing an overcurrent limiting process of the motor control device according to the embodiment.

  In the main control shown in FIG. 2, first, an estimated motor current value is calculated in step ST1. The calculation of the estimated motor current value is performed by the motor current estimation unit 30 according to the estimated motor current value calculation control shown in FIG. Details of the estimated motor current value calculation control will be described later.

  Step ST2 is performed by the motor current limiting circuit 16 according to the overcurrent limiting process control of FIG. Details of the overcurrent limiting process control will be described later. When the motor current limit circuit 16 determines that the current flowing through the switching element of the inverter circuit 2 is an overcurrent by the overcurrent limit process control, the motor current limit circuit 16 determines that the duty ratio limit signal is not an overcurrent. The duty ratio determination permission signal is output to the output duty determination circuit 14.

  Step ST3 is performed by the output duty determination circuit 14. When the output duty determining circuit 14 receives the duty ratio limiting signal from the motor current limiting circuit 16, the output duty determining circuit 14 sets an upper limit value of a settable range of the output duty ratio, and sets the acceleration output signal, the battery current value, and the battery potential value. Based on this, the output duty ratio is determined. The upper limit value of the settable range is set to 0% to 50%, for example. On the other hand, when the output duty determination circuit 14 receives the duty ratio determination permission signal from the motor current limit circuit 16, the output duty determination circuit 14 falls within an arbitrary settable range based on the acceleration output signal, the battery current value, and the battery potential value. To determine the output duty ratio. Thus, the main control is finished.

  In the estimated motor current value calculation control shown in FIG. 3, first, in step ST4, the estimation method determination circuit 19 acquires the output duty ratio determination signal, the battery current value, the first determination value, and the second determination value, The output duty ratio is compared with the first determination value, and the battery current value is compared with the second determination value. When the output duty ratio is larger than the first determination value and the battery current value is larger than the second determination value (Yes), the estimation method determination circuit 19 outputs a first estimation method selection signal to the current value estimation circuit 20. Then, the process proceeds to step ST5. In other cases, that is, when the output duty ratio is equal to or less than the first determination value or the battery current value is equal to or less than the second determination value (No), the estimation method determination circuit 19 sends the second estimation method to the current value estimation circuit 20. A selection signal is output and it progresses to step ST6.

In step ST5, the current value estimation circuit 20 receives the first estimation method selection signal and, based on the duty ratio determination signal, the battery current value, and the value of α, calculates the estimated motor current value (I _M ) according to Equation 1. calculate. Then, the current value estimating circuit 20 outputs the calculated estimated motor current value (I _M ) to the motor current limiting circuit 16.

In step ST6, the current value estimation circuit 20 receives the second estimation method selection signal and sets the battery current value (I _B ) as the estimated motor current value. Then, the current value estimating circuit 20 outputs the calculated estimated motor current value (I _M ) to the motor current limiting circuit 16. Thus, the estimated motor current value calculation control ends.

The overcurrent limiting process control shown in FIG. 4 is performed by the motor current limiting circuit 16. First, in step ST7, the estimated motor current value (I _M ) is compared with the third determination value as the overcurrent determination value, and the estimated motor current value (I _M ) is larger than the third determination value (Yes). In step ST8, the error counter is increased, and when the estimated motor current value (I _M ) is equal to or smaller than the third determination value (No), the process proceeds to step ST9 and the error counter is decreased. In step ST9, the error counter may be set to zero. After performing the process of step ST8 or step ST9, the process proceeds to step ST10.

In step ST10, it is determined whether or not the error counter is greater than a predetermined value. That is, it is determined whether or not a period in which the estimated motor current value (I _M ) is greater than the third determination value continues for a predetermined time or more. If the determination is Yes, the process proceeds to step ST11 and the output duty ratio limit signal is output to the output duty determination circuit 14 assuming that the motor current is abnormal. If the determination is No, the process proceeds to step ST12 and the motor current is normal. The duty ratio determination permission signal is output to the output duty determination circuit 14 as follows. By doing so, erroneous detection due to instantaneous noise can be prevented. The output duty determination circuit 14 controls the output duty ratio based on the output duty ratio limit signal or the duty ratio determination permission signal. This is the end of the overcurrent limiting process control.

  The effect of embodiment is demonstrated. With the above configuration, the motor current can be accurately estimated based on the current flowing through the in-vehicle battery BT, and the switching element is controlled by controlling the current flowing through the switching element based on the estimated motor current value. It is possible to prevent an overcurrent from flowing through.

It is known that the motor current can be calculated by the following equation 2.
I _M = I _B / D (Formula 2)
Here, _{I M} is the estimated motor current value (A), _{I B} is the battery current value (A), D is the output duty ratio. Equation 1 used to estimate the motor current in this embodiment can bring the estimated motor current value (I _M ) closer to the actual motor current value than when Equation 2 is used.

FIG. 5 shows a timing chart by PWM control. The motor control device 1 tries to turn on and off the switching element of the inverter circuit 2 with the PWM waveform shown in FIG. 5A. The PWM waveform output from the inverter control circuit 21 of the motor control device 1 is shown in FIG. As shown in (b), error (E1) is included. 5B, the switching element is turned on / off including switching errors (E2, E3) as shown in FIG. 5C. Since the actual behavior of the switching element with respect to the output duty ratio includes errors (E1 to E3), in Equation 1, the estimated motor current value (I) is corrected by correcting the output duty ratio (D) with the error as a circuit error α. The accuracy of _M ) can be improved. The value of α is, for example, 0 to 2%. The value of α can be stored in advance in the memory 22 by measuring errors (E1 to E3) for the motor device.

However, when the battery current value (I _B ) or the output duty ratio (D) is small, it is confirmed that the estimated motor current value (I _M ) calculated from Equation 1 is smaller than the actual motor current value. ing. Therefore, only when the output duty ratio (D) is larger than the predetermined first determination value and the battery current value (I _B ) is larger than the predetermined second determination value, the estimated motor current value (I _M ) is calculated, and when the output duty ratio (D) is equal to or less than the first determination value or the battery current value (I _B ) is equal to or less than the second determination value, the battery current value (I _B ) and the output duty ratio ( D) the estimated motor current value from (I _M) without calculating the battery current value (I _B) by the the estimated motor current value (I _M), the actual motor current estimated motor current value (I _M) It can be close to the value.

The estimated motor current value (I _M ) calculated in this way is more accurate than the conventional estimation method, and the overcurrent determination is performed based on the estimated motor current value (I _M ). It is possible to prevent an overcurrent from flowing through the switching element of the circuit 2.

  In this embodiment, since it is not necessary to provide wiring with a current sensor for each phase of the armature coil, the configuration of the motor device can be simplified, and the manufacturing cost can be reduced.

  Although the description of the specific embodiment is finished as above, the present invention is not limited to the above embodiment and can be widely modified. The circuit configuration of the motor control device shown in the embodiment is an example, and can be changed as appropriate without departing from the spirit of the invention.

It is a block diagram which shows schematic structure of the motor control apparatus which concerns on embodiment. It is a flowchart which shows the main control of the motor control apparatus which concerns on embodiment. It is a flowchart which shows the motor electric current value estimation control of the motor control apparatus which concerns on embodiment. It is a flowchart which shows the overcurrent limiting process control of the motor control apparatus which concerns on embodiment. It is a graph which shows the timing chart by PWM control.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Motor control apparatus 2 Inverter circuit 3 Armature coil 4 Stator 5 Rotor 6 Motor rotation angle sensor 7 Current detection sensor 8 Voltage detection sensor 9 Accelerator pedal apparatus 10 Target output value calculation circuit 11 Current detection circuit 12 Voltage detection circuit 13 Rotation angle detection Circuit 14 Output Duty Determination Circuit 15 Regeneration Duty Determination Circuit 16 Motor Current Limiting Circuit 17 PWM Signal Generation Circuit 18 Advance Angle Control Circuit 19 Estimation Method Determination Circuit 20 Current Value Estimation Circuit 21 Inverter Control Circuit 22 Memory 30 Motor Current Estimation Unit BT Car Battery M motor

Claims (2)

A motor control device that controls a current flowing from a battery to a brushless motor by PWM control based on a duty ratio,
Current detection means for detecting a current flowing through the battery as a battery current value;
When the battery current value is larger than a predetermined first determination value and the duty ratio is larger than a predetermined second determination value, the first estimation method is selected, and the battery current value is equal to or lower than the first determination value, or Estimation method determining means for selecting the second estimation method when the duty ratio is equal to or less than the second determination value;
When the first estimation method is selected, an estimated motor current value as a current flowing in the motor coil is calculated based on the battery current value and the duty ratio, and when the second estimation method is selected, An estimated motor current value calculation unit that uses the battery current value as the estimated motor current value.   2. The motor control device according to claim 1, further comprising duty ratio limiting means for limiting a settable range of the duty ratio when the estimated motor current value is larger than a predetermined third determination value.

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