JP5140122B2 - Control device for electric power steering - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device for controlling an electric power steering, which consumes low current and secures high safety. <P>SOLUTION: When a main power is off, the device for controlling an electric power steering uses a circuit 200 backed up by a battery to intermittently excite a resolver 61 of a brushless motor 6, measures the number of rotation and calculates a steering angle. The circuit switches a cycle of the intermittent excitation of the resolver 61 according to the electromotive voltage of the brushless motor to reduce the consumption current. A duplex rotation speed detection circuit is formed to increase the reliability of a detection value. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to an electric power steering control device that assists the steering force of an automobile with a brushless motor. In particular, the rotational angle and the rotational speed of a brushless motor are detected by a resolver, and the automobile's steering force is detected from the rotational speed and the rotational angle. The present invention relates to a technique for calculating a steering angle of a steering shaft and transmitting it to an external device such as a brake control device.

  Conventionally, the steering angle of an automobile is detected by a steering angle sensor mounted in a steering wheel, and the detected steering angle information is transmitted to related devices such as a brake control device by communication. On the other hand, since the electric power steering assists the steering force of the automobile with the electric motor via a gear provided on the steering shaft, the steering angle can be obtained by dividing the rotation angle of the electric motor by the gear reduction ratio. When a brushless motor is used for this electric motor, the brushless motor is provided with a rotation sensor such as a resolver. Therefore, the steering angle information can be obtained only by conversion from the rotation angle of the electric motor without adding a new sensor. Compared to a rudder angle sensor mounted in a conventional steering wheel, the cost of an automobile can be greatly reduced.

By the way, in electric power steering, the steering shaft may be rotated by some external force even when the main power is turned off and the assist function is cut off. Therefore, when obtaining the steering angle from the rotation angle of the motor It is necessary to monitor the rotation state of the motor with a circuit backed up by a battery even while the main power supply is turned off.
In this case, reduction of the battery current consumption during the backup period is extremely important from the viewpoint of battery life. In order to reduce the current consumption of the battery, there has been conventionally known a method of intermittently exciting the exciting coil of the resolver. For example, in Patent Document 1, a normal continuous operation is performed while the main power source is on. A method in which the resolver is excited with a sine wave and the resolver is intermittently excited with a pulse wave in a battery-backed circuit while the main power is turned off, and the output of the detection coil is sampled and held in synchronization with this excitation. Thus, a method for reducing the current consumption of the battery has been proposed.

Patent No. 3248201

  In the present invention, the conventional intermittent excitation technology of a resolver is applied to an electric power steering apparatus of an automobile. However, backup by a battery increases the current consumption of the battery while the main power is turned off. Thus, the startability of the engine after leaving the automobile for a long period is impaired. Further, when the steering angle is used for brake control, for example, if there is an error in the steering angle information, the brake may malfunction and the safety of the automobile may be reduced.

  The present invention has been made in consideration of the usage environment unique to these automobiles and the high safety required for automobiles, and solves the problems inherent to these automobiles, achieves low current consumption and is high. An object of the present invention is to provide an electric power steering control device that ensures safety.

  The electric power steering control device according to the present invention is an electric power steering device that assists the steering force of an automobile with a brushless motor. The rotation speed and the rotation angle of the brushless motor are different from each other by 90 degrees in phase with the excitation coil of the brushless motor. It is detected by a resolver consisting of two detection coils, and the steering angle of the steering shaft connected to the brushless motor through a gear is calculated from the detected rotation speed and rotation angle, and this steering angle is calculated with respect to external peripheral devices. When the main power of the electric power steering device is turned off and the main circuit is shut off and the assist function is stopped, the excitation coil is intermittently excited by the backup circuit backed up by the battery of the automobile. Measure the rotation speed of the brushless motor and turn on the main power to configure the main circuit When the CPU receives the rotation speed measured by the backup circuit after the PU starts operating via serial communication, the CPU continues to measure the rotation speed thereafter, and when the main power is turned off next time, the CPU measures the rotation speed. After the value is received by the backup circuit via serial communication, the rotation speed measurement by the intermittent excitation of the backup circuit is continued, and the intermittent period of this intermittent excitation is less than the predetermined value according to the terminal voltage of the brushless motor. In this case, the intermittent cycle is set long, and when the terminal voltage is equal to or higher than a predetermined value, the intermittent cycle is set short.

  According to the present invention, the resolver is intermittently excited by the backup circuit backed up by the battery, and the intermittent period is switched according to the terminal voltage of the motor, so that low current consumption can be realized. In addition, since various types of monitoring by the backup circuit itself and various diagnoses to the backup circuit by the CPU of the main circuit are performed, it is possible to provide an electric power steering control device that ensures high safety.

It is a whole block diagram showing an electric power steering device. It is a timing chart figure which shows the principle of steering angle calculation. It is a block diagram which shows the structure of the control apparatus (ECU) of electric power steering. It is a timing chart figure which shows the connection of the backup circuit and main circuit of a control apparatus (ECU). It is a timing chart figure which shows the waveform of intermittent excitation and normal excitation. It is a chart figure which shows the principle of rotation speed measurement. It is a block diagram which shows the circuit structure of the control apparatus which concerns on Embodiment 1 of this invention. It is a timing chart figure which shows the generation method of the intermittent excitation pulse by this invention. It is a block diagram of the high rotation detector which detects the high rotation state of the motor used for this invention. It is a timing chart figure which shows the operation | movement of the low voltage detection circuit used for this invention. It is a schematic diagram which shows operation | movement of the I / F circuit which connects the resolver and comparator which are used for this invention.

Embodiment 1 FIG.
Hereinafter, an electric power steering control apparatus according to Embodiment 1 of the present invention will be described with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected and demonstrated about the part which is the same or it corresponds.
FIG. 1 is an overall block diagram schematically showing an electric power steering apparatus according to the present invention, which assists a steering force with a brushless motor.

  In FIG. 1, when the handle 1 is operated, the torsion bar 3 inserted into the steering shaft 2 is twisted by the applied rotational torque. The torque sensor 4 detects the torque applied from the twist angle and transmits it to the controller (ECU) 5. The controller 5 is connected to the brushless motor 6 and processes a resolver signal provided in the brushless motor 6 to obtain a rotation angle of the brushless motor 6, and a current proportional to the detected torque according to the rotation angle. The brushless motor 6 is energized. The brushless motor 6 generates torque proportional to the energized current and applies assist force to the steering shaft 2 via the reduction gear 7. A gear is attached to the tip of the steering shaft 2, and the inclination angle of both wheels is changed by moving the axle 8 connected to both wheels of the automobile.

  As shown in FIG. 1, the steering shaft 2 and the brushless motor 6 are connected by a reduction gear 7, so that the rotation angle of the steering shaft 2 can be obtained by dividing the rotation angle of the brushless motor 6 by the reduction ratio of the reduction gear 7. It is done. The controller 5 calculates the rotation angle (steering angle) of the steering shaft 2 from the rotation angle and the rotation speed obtained by processing the resolver signal, and transmits the rotation angle (steering angle) to the external peripheral device 10 such as a brake control device via the communication line 9. To do.

Next, the rotation angle obtained from the resolver provided in the brushless motor 6 and the relationship between the rotation speed and the steering angle will be described with reference to FIG.
FIG. 2 is a chart in the case where the brushless motor continues to rotate normally. (A) shows the rotation angle of the brushless motor 6 from 0 degrees to 360 degrees, and (B) shows the rotation angle (A). The number of rotations counted up every 360 degrees is represented, and (C) represents the rotation angle (steering angle) of the steering shaft 2. From FIG. 2, the steering angle (C) of the steering shaft 2 can be obtained by multiplying the rotation speed (B) by 360 degrees and adding the rotation angle (A) and dividing this by the reduction ratio of the reduction gear 7. I understand.

Next, the configuration of the controller 5 will be described with reference to FIG.
The controller 5 includes a main circuit 100 that operates while the automobile KEY switch 12 is on, and a backup circuit 200 that is always backed up and operated by the battery 11 of the automobile. A resolver 61 provided in the brushless motor 6 is connected to both the main circuit 100 and the backup circuit 200, and both circuits are connected by serial communication.

Hereinafter, the operation when the KEY switch 12 is turned on will be described with reference to FIG.
In FIG. 4, the KEY switch 12 is turned off in the section T <b> 1, and the rotational speed (B) of the resolver 61 is measured by the backup circuit 200. Next, when the KEY switch 12 is turned on in the section T2, the main circuit 100 is activated, and the rotation speed (B) measured by the backup circuit 200 is received by the main circuit 100 via serial communication. The main circuit 100 processes the signal of the resolver 61 to obtain the rotation angle (A), and the rotation angle (A) calculated by itself by multiplying the rotation number (B) received from the backup circuit 200 by 360 degrees according to the calculation method described above. ) And then divided by the reduction ratio of the reduction gear 7 to obtain the steering angle (C) of the steering shaft. In this manner, while the KEY switch 12 is turned off, the steering angle (C) of the steering shaft can be obtained by detecting only the rotational speed of the resolver 61.

Next, normal excitation by the main circuit 100 and intermittent excitation by the backup circuit 200 for the resolver 61 will be described with reference to FIGS.
FIG. 5 is a chart showing the excitation waveform of the resolver 61. The section (Ta) and the section (Tc) represent the sections in which the main circuit 100 is turned off, and the section (Tb) represents the state in which the main circuit 100 is turned on. Represents a section. In the sections (Ta) and (Tc) where the main circuit 100 is off, the backup circuit 200 is intermittently excited to reduce the current consumption of the battery 11, and the main circuit 100 is turned on. In a certain section (Tb), normal excitation by a continuous sine wave is performed.

  When the resolver 61 is excited, a detection waveform whose amplitude is modulated in accordance with the rotation angle of the resolver 61 is extracted from the detection coil. The two detection coils are 90 degrees out of phase with each other, and their amplitudes are sine and cosine with respect to the rotation angle of the resolver 61. When the detection voltage of the detection coil is expressed on the XY plane with the cosine as X and the sine as Y, a Lissajous circle shown in FIG. 6 is obtained. As shown in FIG. 6, it is possible to divide one revolution of the resolver angle into four regions every 90 degrees from the combination of positive and negative detection voltages. That is, the region where both the sine and cosine are positive gives the first quadrant, the region where the sine is positive and the cosine is negative gives the second quadrant, the region where both the sine and cosine are negative gives the third quadrant, The region where the sine is negative and the cosine is positive gives the fourth quadrant. In this way, one revolution of the resolver can be divided into four regions every 90 degrees by combining positive and negative detection voltages of the two detection coils.

  When the brushless motor 6 rotates in the forward direction, the quadrant changes in the order of the first, second, third, and fourth, and when the brushless motor 6 rotates in the reverse direction, the quadrant changes to the fourth and fourth. 3, transition from second to first. Therefore, the state of this quadrant is monitored every intermittent excitation period, the value of the rotation speed counter is incremented by 1 when transitioning from the fourth quadrant to the first quadrant, and the rotation speed counter when shifting from the first quadrant to the fourth quadrant. The number of revolutions can be measured by decrementing the value of −1.

Hereinafter, the block diagram of FIG. 7 showing the circuit configuration of the control device for the electric power steering according to the first embodiment of the present invention will be described.
The control device shown in FIG. 7 includes a main circuit 100 that operates while the KEY switch 12 of the automobile is on, and a backup circuit 200 that is always backed up and operated by the battery 11 of the automobile. The power source 101, the CPU 102, the inverter 104 that drives the brushless motor 6, the resolver 61 provided in the brushless motor 6, and the resolver interface (I / F) circuit 103 between the CPU 102 and the like. The main circuit 100 operates while the KEY switch 12 of the automobile is turned on, and drives the brushless motor 6 through the inverter 104 under the control of the CPU 102.

The backup circuit 200 is always backed up by the battery 11 of the automobile. First, a clock CK is generated by the oscillator 201. Next, the timing generator 202 generates an excitation pulse Pexc having a clock width as a pulse width every predetermined intermittent excitation period obtained by dividing the clock CK. Next, the excitation pulse Pexc is passed through the low-pass filter 203 to obtain an excitation waveform Vexc, and the excitation coil of the resolver 61 is excited via the buffer amplifier 204.
FIG. 8 shows the generation timing of the clock CK, the excitation pulse Pexc, and the excitation waveform Vexc.

  Next, the signals SIN and COS of the two detection coils of the resolver 61 are input to the comparator 206 through switch means such as the analog switch 205. The input of the comparator 206 is provided with an I / F circuit such as a pull-up / down circuit 207 for setting a simulated input as will be described later. Whether the detection signals SIN and COS of the detection coil are positive or negative is determined by the comparator 206, and the result is latched in the next stage latch (current) 208 at the end timing of the excitation pulse Pexc. With the above operation, the circuit power supplies of the buffer amplifier 204 and the comparator 206 are also turned on intermittently by the excitation pulse Pexc in order to reduce current consumption.

The latch comprises two stages connected in series, and two latches are provided corresponding to the two detection signals SIN and COS. At the end timing of the excitation pulse Pexc, the output of the latch (current) 208 is transferred to the next-stage latch (previous) 209 and the output of the comparator 206 is latched in the latch (current) 208. That is, the result of the previous intermittent excitation pulse Pexc of the output of the comparator 206 and the result of the current intermittent excitation pulse Pexc are latched. The outputs of these latches are decoded by the decoder 210 at the next stage to obtain an UP signal that increments the rotation number counter (A) 211 and a DOWN signal that decrements -1. That is, the UP signal is output when the previous quadrant is the fourth quadrant and the current quadrant is the first quadrant, and the DOWN signal is output when the previous quadrant is the first quadrant and the current quadrant. The rotation number counter (A) 211 is composed of an up / down counter, and is counted up by the UP signal output from the decoder 210 and counted down by the DOWN signal.
Then, after the CPU 102 constituting the main circuit 100 is activated, the value of the rotation speed counter (A) 211 is transmitted to the CPU 102 via the serial communication I / F circuit 218, and the CPU 102 determines the steering angle based on the value of the rotation speed counter. Is calculated.

  By the way, in the present invention, in order to ensure the redundancy of the apparatus and improve the reliability, two series of rotation speed counters are provided. Further, in the second-sequence rotation speed counter (B) 212, the UP signal and DOWN are exchanged, and the values of the first-sequence rotation counter (A) 211 and the second-sequence rotation counter (B) 212 are changed. The increase and decrease are reversed. Therefore, as long as the operations of both counters are normal, the sum of the values of both counters is always the midpoint value of the steering angle. After startup, the CPU 102 of the main circuit 100 reads the values of the two rotation speed counters 211 and 212 via the serial communication I / F circuit 218, and if the sum of the two coincides with the midpoint of the steering angle, it is normal. If it does not match, it is determined as abnormal.

  Furthermore, the present invention also has a region transition monitoring function described with reference to FIG. As described above, when the brushless motor 6 rotates, the quadrant of the region is normally changed to the adjacent quadrants sequentially. When this transition is caused by any cause, for example, when the transition is made by jumping over the adjacent quadrants from the first quadrant to the third quadrant, the transition state is abnormal, the abnormality signal ERR1 is output from the decoder 210, and the abnormality detection counter 213 The value of is incremented to +1. After the CPU 102 of the main circuit 100 is started, the CPU 102 reads the count value of the abnormality detection counter 213 via the serial communication I / F circuit 218. If the count value is equal to or greater than a predetermined value, the operation of the backup circuit 200 is abnormal. A signal to that effect is transmitted to the external peripheral device 10.

Further, the present invention switches the intermittent excitation period according to the rotation state of the brushless motor 6 to suppress the increase in the current consumption of the battery 11 and to follow the high speed rotation of the brushless motor 6. 214.
The high rotation detector 214 determines whether the rotational speed is high or low based on the electromotive voltages Vu, Vv, and Vw of the three-phase terminals of the brushless motor 6. That is, when the brushless motor 6 is rotated by some external force, the electromotive voltage is high if the rotational speed is high, and the electromotive voltage is low if the rotational speed is low. Therefore, it is determined from this electromotive voltage whether the rotational speed of the brushless motor 6 is high or low. it can.

  As shown in FIG. 9, the high speed detector 214 rectifies the terminal voltages Vu, Vv, Vw by a circuit network 214a composed of a diode, a resistor and a capacitor, and whether the rectified voltage is equal to or higher than a predetermined value. Is determined by the voltage comparator 214b. The timing generator 202 at the next stage receives this determination result, and if the terminal voltage is less than or equal to a predetermined value, the division ratio is set large to set the intermittent excitation period longer, and the terminal voltage is greater than or equal to the predetermined value. In this case, the frequency division ratio is set small and the intermittent excitation cycle is set short. As described above, an increase in current consumption of the battery 11 can be suppressed by switching the intermittent excitation cycle according to the rotation state of the brushless motor 6.

Furthermore, the present invention provides a predetermined value for calculating the steering angle when a low voltage at which the backup circuit 200 becomes inoperable is detected, such as when the battery 11 is disconnected or when the output voltage of the battery 11 is abnormally lowered. A circuit for performing initialization processing is also provided.
That is, the backup circuit 200 includes a constant voltage power source 215 that obtains a predetermined constant voltage from the voltage of the battery 11 as its own circuit power source. The low voltage detector 216 monitors the output voltage Vcc of the constant voltage power source 215 and resets the built-in flip-flop BFF when the output voltage Vcc falls below the voltage VL at which the backup circuit 200 operates normally.

  Next, when the power supply 101 of the main circuit 100 is turned on and the CPU 102 is activated, the CPU 102 reads the state of the flip-flop BFF via the serial communication I / F circuit 108. If so, the flip-flop BFF is set via the serial communication I / F circuit 108 after performing a predetermined initialization process on the rotation speed detection value. Thereafter, when the CPU 102 is turned off and restarted, normal processing is performed if the flip-flop BFF remains set, and initialization processing is performed if the flip-flop BFF is reset. FIG. 10 is a timing chart showing detection and processing operations in the low voltage detector 216 when the voltage of the battery 11 is abnormally lowered. As described above, a drop in the power supply voltage is monitored, it is detected that the battery 11 is disconnected, and an appropriate initialization process is performed.

Next, the operation of the I / F circuit such as the pull-up / down circuit 207 for setting the input of the comparator 206 will be described with reference to FIG. Although FIG. 11 shows one detection coil of the resolver 61, the same applies to the other detection coil.
In FIG. 11, the + end of the detection coil of the resolver 61 is connected to the + input of the comparator 206, and the − end of the detection coil is connected to the − input of the comparator 206. Each input is connected to a pull-up resistor connected to the power source by the switch elements S1 and S2 of the pull-up / down circuit 207 and a pull-down resistor connected to the ground by the switch elements S3 and S4. In FIG. 11, the switch element is schematically represented by using a mechanical switch symbol, but an electronic switch is actually used.

The switch elements S1 to S4 are turned on / off by a command signal transmitted from the CPU 102 via the serial communication I / F circuit 218 after the CPU 102 is activated. As will be described later, these switch elements S1 to S4 are set on and off based on commands from the CPU 102 according to the operation of the circuit at that time.
In a normal operation for detecting the positive and negative of the detection signals SIN and COS of the resolver 61, as shown in FIG. 11A, each input of the comparator 206 is switched on when the switch elements S1 and S2 are turned on. Both are connected in a pull-up manner so that a bias voltage is equally applied to both inputs.

Next, a description will be given of a case where the connection monitoring circuit 217 is used to diagnose a failure in the connection state of the resolver signal by setting a simulated input to an I / F circuit such as the pull-up / down circuit 207 that is an input circuit of the comparator 206. To do.
The simulated input is based on a command signal transmitted from the CPU 102 via the serial communication I / F circuit 218 to control on / off of the switch elements S1 to S4 of the pull-up / down circuit 207 and to apply a predetermined voltage to the input of the comparator 206. In addition, the pull-up / down circuit 207 also functions as a simulated input setting circuit.

In the intermittent excitation state, a non-excitation period occurs between the current excitation and the next excitation, and during this period, a test pulse simulation input is added to the pull-up / down circuit 207 to perform diagnosis.
First, when detecting disconnection or ground fault of the resolver 61, as shown in FIG. 11B, the switch elements S1 and S4 are turned on by this test pulse, and the + side of the detection coil is pulled up. Pull down the-side. Since the + side is pulled up, an increase in voltage can be detected on the − side in normal conditions. However, when a disconnection occurs in the wiring from the backup circuit 200 to the detection coil of the resolver 61, or to the ground. Since the + side voltage is not transmitted to the-side when an entanglement has occurred, the connection monitoring circuit 217 monitors this-side voltage and determines that it is abnormal if this voltage is below a predetermined value. Then, the disconnection / ground fault detection pulse ERR2 is output and the abnormality detection counter 213 is incremented to +1.

Next, when detecting the power supply fault of the resolver 61, only the switch element S4 is turned on as shown in FIG. 12C at another timing different from the above test pulse, and the + side Open the resistor and pull down the-side to monitor the-side voltage. In the normal state, no voltage is generated on the negative side. However, when a power supply fault occurs in the detection coil wiring of the resolver 61, this is transmitted and a voltage is generated on the negative side. If this voltage is monitored and it is equal to or greater than a predetermined value, a power fault detection pulse ERR2 is output and the abnormality detection counter 213 is incremented to +1. After the CPU 102 constituting the main circuit 100 is activated, the value of the abnormality detection counter 213 is transmitted to the CPU 102 via the serial communication I / F circuit 218, and the CPU 102 sends a signal indicating that the peripheral device 10 is abnormal. To send.
The test pulse generated here does not need to be synchronized with the generation of the intermittent excitation pulse, and the current consumption of the battery is reduced by setting the generation interval longer than the generation interval of the excitation pulse.

Next, processing after the power supply 101 of the main circuit 100 is turned on and the CPU 102 is activated will be described.
The backup circuit 200 continues the rotation speed measurement by intermittent excitation even after the CPU 102 is activated, and transmits a synchronization signal SYNC synchronized with the intermittent excitation to the CPU 102. The CPU 102 receives the synchronization signal SYNC and measures the period. If the period is within a predetermined range, the CPU 102 determines that the period is normal and performs normal processing. If the period is out of the predetermined range, the operation of the backup circuit 200 is abnormal. And a signal indicating that the detected steering angle is abnormal is transmitted to the peripheral device 10.

When the CPU 102 is activated, first, the measured values of the two series of rotation speed counters 211 and 212 by the backup circuit 200 are read via the serial communication I / F circuit 218 and transplanted to the own rotation speed measurement values. Next, a command signal is sent to the backup circuit 200 via the serial communication I / F circuit 218 to turn off the analog switch 205, thereby disconnecting the detection coil of the resolver 61 from the backup circuit 200. Thereby, the influence of the backup circuit 200 on the resolver signal processing by the normal excitation can be removed, and the failure diagnosis described below by the CPU 102 on the backup circuit side can be performed.
That is, the CPU 102 inputs a signal from the detection coil of the resolver 61 by normal excitation through the resolver I / F circuit 103 and processes the signal, thereby calculating the steering angle from the rotation angle and the rotation speed of the brushless motor 6. In parallel with this, the following failure diagnosis for the backup circuit 200 is performed.

  With the analog switch 205 turned off and the detection coil of the resolver 61 disconnected from the backup circuit 200, the connection between the pull-up resistor and pull-down resistor of the pull-up / down circuit 207, which is the input circuit of the comparator 206, is connected to the serial communication from the CPU 102. Various diagnoses for the backup circuit 200 to be described later are performed by turning on / off by a command signal via the I / F circuit 218.

First, as shown in FIG. 11B, when the switch elements S1 and S4 of the pull-up / down circuit 207 are turned on, the + input of the comparator 206 is pulled up and the-input is pulled down, it corresponds to the positive output of the detection coil. Is input to the comparator 206. Conversely, as shown in FIG. 11D, when the switch elements S2 and S3 of the pull-up / down circuit 207 are turned on, the + input of the comparator 206 is pulled down and the-input is pulled up, the negative output of the detection coil A considerable voltage is input to the comparator 206.
In this way, by sequentially applying voltages corresponding to the positive and negative of the detection voltages of the two detection coils to the input of the comparator 206, a signal corresponding to the rotation of the brushless motor 6 can be obtained at the output of the comparator 206.

  After the CPU 102 constituting the main circuit 100 is started, the CPU 102 sequentially changes the quadrant of the area determination by giving a simulated input that sequentially changes the quadrant of the area via the serial communication I / F circuit 218 to thereby change the rotation speed counter. (A) The values of 211 and the rotation number counter (B) 212 are increased or decreased. The CPU 102 receives the values of the rotation speed counters 211 and 212 via the serial communication I / F circuit 218, and backups if the received values of the rotation speed counters 211 and 212 coincide with the quadrant transition given from the CPU 102. After determining that the operation of the circuit 200 is normal, normal processing is performed. If they do not match, it is determined that the operation is abnormal, and a signal indicating that the detected steering angle is abnormal is transmitted to the peripheral device 10. To.

The abnormality detection counter 213 is also diagnosed in the same manner as the diagnosis for the rotation speed counters 211 and 212 described above.
In this case, the transition of the region is set so as to jump over the adjacent quadrants such as the first to third quadrants. After the CPU 102 constituting the main circuit 100 is activated, the CPU 102 gives a simulated input to the comparator 206 via the serial communication I / F circuit 218, thereby causing an abnormal transition in the transition of the quadrant of the area determination, and the abnormality detection counter 213. Increase or decrease the value of. Further, the CPU 102 receives the value of the abnormality detection counter 213 via the serial communication I / F circuit 218, and if the received value of the abnormality detection counter 213 matches the abnormal transition of the quadrant given from the CPU 102, the backup circuit 200. The normal processing is performed after determining that is normal, and if they do not match, it is determined as abnormal and a signal indicating that the detected steering angle is abnormal is transmitted to the peripheral device 10.

Next, diagnosis for the connection monitoring circuit 217 will be described.
As shown in FIG. 11B, when the switch elements S1 and S4 of the pull-up / down circuit 207 are turned on to pull up the + input resistance of the comparator 206 and pull down the −input resistance, the comparator 206 An output corresponding to when the wiring of the resolver 61 is disconnected or grounded is obtained.
After the CPU 102 constituting the main circuit 100 is started, the CPU 102 gives the above-described simulated input corresponding to the case where the connection of the detection coil of the resolver 61 is abnormal via the serial communication I / F circuit 218, thereby detecting the abnormality detection counter 213. Increase or decrease the value of. Further, the CPU 102 receives the value of the abnormality detection counter 213 via the serial communication I / F circuit 218, and if the received value of the abnormality detection counter 213 matches the simulated input given from the CPU 102, the backup circuit 200 is normal. After the determination, the normal processing is continued. If they do not match, it is determined that there is an abnormality and a signal indicating that the detected steering angle is abnormal is transmitted to the peripheral device 10.

As described above, according to the present invention, the resolver 61 of the brushless motor 6 is intermittently excited by the backup circuit 200 backed up by the battery 11 while the main power source of the power steering control device is turned off. For detecting the number of revolutions, the current consumption of the battery 11 can be reduced by detecting that the brushless motor 6 is rotated by the electromotive voltage detected at the terminal of the brushless motor 6 and switching the intermittent excitation cycle. it can.
Further, after the CPU 102 constituting the main circuit 100 of the control device is started, the influence of the backup circuit 200 on the main circuit 100 can be eliminated by disconnecting the backup circuit 200 by switch means such as the analog switch 206. .

Furthermore, by detecting and storing a low voltage at which the backup circuit 200 becomes inoperable, initialization processing can be performed when calculating the steering angle when battery removal is detected.
Further, the comparator 206 determines whether the signals of the two detection coils of the resolver 61 are positive or negative, detects an increase / decrease in the number of rotations from the transition state of the quadrant of the four regions composed of the positive / negative combinations of the two signals, and By detecting an abnormality and counting by the abnormality detection counter 213, an abnormality in the steering angle can be detected. Further, the connection monitoring circuit 217 detects the abnormality of the connection state of the resolver signal and counts it by the abnormality detection counter 213, whereby the abnormality of the connection state can be detected.

  Furthermore, the reliability of the detected value of the steering angle can be improved by using a double speed detection circuit. Further, the CPU 102 measures the period of the intermittent excitation pulse generated by the backup circuit 200, thereby detecting the failure of the intermittent excitation period generation circuit and eliminating the influence. Further, by providing a simulated input from the CPU 102 to the input of the comparator 206, it is possible to diagnose a failure in the connection monitoring circuit that monitors the connection state of the rotation speed counter, the abnormality detection counter, and the resolver signal of the backup circuit 200.

1: steering wheel, 2: steering shaft,
3: Torsion bar, 4: Torque sensor,
5: Controller (ECU) 6: Brushless motor,
61: Resolver, 7: Reduction gear,
8: Axle, 10: External peripheral equipment,
11: Battery, 12: KEY switch,
100: main circuit, 101: main power supply,
102: CPU, 103: Resolver I / F circuit,
104: Inverter 200: Backup circuit 201: Oscillator
202: Timing generator 203: Low-pass filter
204: Buffer amplifier, 205: Analog switch,
206: Comparator, 207: Pull-up / down circuit,
208: Latch, 209: Latch,
210: Decoder, 211: Revolution counter,
212: Revolution counter, 213: Abnormality detection counter,
214: High rotation detector, 215: Power supply,
216: Low voltage detector, 217: Connection monitoring circuit,
218: Serial communication I / F circuit.

Claims (10)

  In an electric power steering apparatus that assists the steering force of an automobile with a brushless motor, the rotational speed and rotation angle of the brushless motor are detected by a resolver comprising two detection coils that are 90 degrees out of phase with the excitation coil of the brushless motor. A steering angle of a steering shaft connected to the brushless motor via a gear is calculated from the detected rotation speed and rotation angle, and the steering angle is transmitted to an external peripheral device. The electric power steering apparatus While the main circuit is turned off and the main circuit is shut off and the assist function is stopped, the excitation coil is intermittently excited by a backup circuit whose power is backed up by a vehicle battery, and the rotational speed of the brushless motor is The CPU that configures the main circuit starts operating when the main power is turned on. After the CPU has received the rotational speed measured by the backup circuit via serial communication, the CPU continues to measure the rotational speed, and when the main power is turned off, the rotational speed measured value by the CPU is The rotation number measurement by the intermittent excitation of the backup circuit after the backup circuit is received via serial communication is continued, and the intermittent cycle of the intermittent excitation is determined according to the terminal voltage of the brushless motor. In the following cases, the intermittent cycle is set to be long, and when the terminal voltage is equal to or higher than a predetermined value, the intermittent cycle is set to be short.   2. The electric motor according to claim 1, wherein the switch circuit disconnects the backup circuit and the resolver while the rotational speed is being measured by the resolver signal processing by the CPU constituting the main circuit. Power steering control device.   The backup circuit monitors the battery voltage or the output voltage of its own power supply, and stores this when the voltage falls below a voltage necessary for the backup circuit to operate normally, and the CPU constituting the main circuit After the activation, the result is transmitted to the CPU via serial communication, and the CPU performs a predetermined initialization process when calculating the steering angle when the decrease in the voltage is detected. The control apparatus for the electric power steering according to claim 1.   The backup circuit outputs an excitation pulse having a predetermined width at a predetermined period, excites the excitation coil of the resolver by an excitation signal obtained by passing the excitation pulse through a low-pass filter, and each of the two detection coils of the resolver. Whether the voltage difference between both ends is judged by a comparator, the result is latched at the timing of the end of the excitation pulse, and one revolution of the resolver is rotated every 90 degrees from the positive / negative combination of two detection coils known from the output of the latch. The quadrant of this area is determined, and when the quadrant of this area transitions from the fourth quadrant to the first quadrant, the resolver has made one rotation in the positive direction, and the value of the rotation counter is incremented by one. When changing from the first quadrant to the fourth quadrant, the resolver makes one rotation in the reverse direction, and the value of the rotation counter is decremented by 1. Further, this region jumps over the adjacent quadrants. When a transition occurs, the value of the abnormality detection counter is incremented by 1, and the value of the rotation number counter and the abnormality detection counter is transmitted to the CPU via serial communication after the CPU constituting the main circuit is started. The CPU calculates a steering angle based on the value of the rotation number counter, and when the abnormality detection counter is equal to or larger than a predetermined value, a signal indicating that the steering angle detection is abnormal for peripheral devices. The apparatus for controlling an electric power steering according to claim 1, wherein:   The backup circuit applies a test pulse to the + end of the detection coil at a timing different from the intermittent excitation and monitors the voltage at the-end of the detection coil. If this voltage is not within the predetermined range, it is determined as abnormal. The value of the abnormality detection counter is incremented by one, and after the CPU constituting the main circuit is started, the value of the abnormality detection counter is transmitted to the CPU via serial communication. The CPU has a predetermined value of the abnormality detection counter. 2. A normal process is continued if the value is less than or equal to a value, and a signal indicating an abnormality is transmitted to a peripheral device if the value of the abnormality detection counter is greater than or equal to a predetermined value. The control apparatus of the electric power steering described in 1.   The backup circuit has two rotation speed counters. One of the two rotation speed counters operates with +1 and -1 counters, and the other rotation speed counter operates in reverse. The values of these two rotation speed counters are serially communicated. When the sum of the values of the two rotation speed counters is a predetermined value that represents the midpoint of the steering angle, the CPU that constitutes the main circuit that has received the signal determines that the rotation speed counter value is normal. Normal processing is continued, and when the sum of the values of the two rotation speed counters is different from a predetermined value representing the midpoint of the steering angle, it is determined as abnormal, and the steering angle is abnormal with respect to the peripheral device. 2. The electric power steering control device according to claim 1, wherein a signal to that effect is transmitted.   The backup circuit transmits a synchronization signal synchronized with the excitation pulse to the CPU after activation of the CPU constituting the main circuit. The CPU measures the period of the synchronization signal, and if this period is within a predetermined range. The normal processing is performed by determining as normal, and if it is not predetermined, it is determined as abnormal, and a signal indicating that the detected steering angle is abnormal is transmitted to the peripheral device. The control apparatus of the electric power steering of 1.   Provided with a simulated input setting circuit for setting a simulated input by applying a predetermined voltage to the comparator input of the backup circuit, and after starting the CPU constituting the main circuit, the CPU gives this simulated input via serial communication To sequentially change the quadrant of the region determination to increase or decrease the value of the rotation speed counter, receive the value of the rotation speed counter via serial communication, and the received rotation speed counter value is the quadrant given from the CPU. If it agrees with the transition of the backup circuit, the backup circuit is judged to be normal, and normal processing is performed thereafter. If it does not agree, it is judged abnormal and the steering angle detected for the peripheral device is abnormal. 2. The electric power steering control device according to claim 1, wherein a signal is transmitted.   Provided with a simulated input setting circuit for setting a simulated input by applying a predetermined voltage to the comparator input of the backup circuit, and after starting the CPU constituting the main circuit, the CPU gives this simulated input via serial communication Causes an abnormal transition in the quadrant transition of the region determination to increase or decrease the value of the abnormality detection counter, and further receives the value of the abnormality detection counter via serial communication, and the value of the received abnormality detection counter is If it matches the abnormal transition of the quadrant given by the CPU, the backup circuit is determined to be normal and normal processing is performed thereafter. If not, the steering angle is determined to be abnormal and detected for the peripheral device. 2. The electric power steering control device according to claim 1, wherein a signal indicating that the engine is abnormal is transmitted.   Provided with a simulated input setting circuit for setting a simulated input by applying a predetermined voltage to the comparator input of the backup circuit, and after starting the CPU constituting the main circuit, the CPU gives this simulated input via serial communication Gives a simulated input corresponding to when the connection of the detection coil of the resolver is abnormal to increase or decrease the value of the abnormality detection counter, and further receives the value of the abnormality detection counter via serial communication. If the counter value matches the simulated input given from the CPU, it is determined that the backup circuit is normal, and then normal processing is continued. 2. The electric power steering control device according to claim 1, wherein a signal indicating that the detected steering angle is abnormal is transmitted.

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