JP5407106B2 - Motor drive control device and electric power steering device using the same - Google Patents

Description

  The present invention relates to a motor drive control device including an electric motor and a motor drive circuit that drives and controls the electric motor, and an electric power steering device using the motor drive control device.

As a conventional motor drive control device, for example, a relay contact that outputs and controls a drive current to a large current load from a DC power supply, a smoothing capacitor connected between the large current load connection side of the relay contact and the ground, Pre-charge control means comprising: pre-charge control means for closing the relay contact after charging the capacitor with a voltage divided by a voltage dividing resistor during a predetermined time before the relay contact is closed. Means for charging the capacitor after charging for the predetermined time and then shutting off the charging, so that the determination voltage of the capacitor is lower than a saturation voltage after the relay contact is turned on after reaching the precharge setting voltage. There has been proposed an automobile control device that does not affect the charging voltage for determining an abnormal state such as during relay welding (see, for example, Patent Document 1).
Japanese Patent No. 3750871 (first page, FIG. 2)

  However, in the conventional example described in Patent Document 1, when supplying an operating current from a DC power supply device to a load through a relay contact, a charge is previously charged to a smoothing capacitor that reduces a ripple component in the operating current. After that, the inrush current to the capacitor can be reduced by closing the relay contact and supplying the operating current to the load from the DC power supply device, but the charge voltage to the capacitor is the voltage of the DC power supply. Since the voltage is divided by the voltage dividing resistor, the charge voltage to the capacitor fluctuates according to the fluctuation of the voltage of the DC power supply, but the fluctuation width is suppressed to a small extent, so when the voltage of the DC power supply becomes high There is an unsolved problem that the generation of current cannot be suppressed.

  Therefore, the present invention has been made paying attention to the above-mentioned unsolved problems of the conventional example, and a motor drive control device capable of reliably suppressing the occurrence of an inrush current by maintaining a proper charge voltage to the capacitor. And it aims at providing the electric power steering device which uses this.

In order to achieve the above object, a motor drive control device according to claim 1 is a motor drive control device comprising an electric motor and a motor drive circuit that controls the drive of the electric motor based on electric power from a DC power supply. There,
A power supply relay circuit interposed between the DC power supply and the motor drive circuit, and a precharge circuit connected in parallel with the power supply relay circuit,
The precharge circuit includes a capacitor connected between a contact on the motor drive circuit side of the power relay circuit and the ground, a switching element connected in parallel with the power relay circuit and driven by a pulse width modulation signal, and the switching a series circuit of the precharge resistors set the precharge voltage to a small value that can be controlled by the pulse width modulated signal to said capacitor when driving element by said pulse width modulated signal, the precharge voltage for the previous SL capacitor And a precharge drive unit that outputs the pulse width modulation signal that approximates the power supply voltage of the DC power supply to the switching element .

The motor drive control device according to claim 2 is the invention according to claim 1, wherein the pre-charge driver, the frequency of the pulse width modulated signal to approximate the precharged voltage to the capacitor to the DC supply voltage and It is characterized in that at least one of the duty ratios is set in advance.
Furthermore, the motor drive control device according to claim 3 has a power supply voltage detection unit that detects a power supply voltage of the DC power supply in the invention according to claim 1, and the precharge drive unit is provided with the power supply voltage detection unit. The frequency of the pulse width modulation signal is controlled so as to suppress the inrush current in accordance with the power supply voltage detected in (1).

  Furthermore, the motor drive control device according to a fourth aspect is the invention according to any one of the first to third aspects, wherein the precharge driving unit outputs the power supply before outputting the pulse width modulation signal to the switching element. Precharge for diagnosing whether or not the contact welding of the relay circuit has occurred, and diagnosing whether the precharge voltage is normal by outputting the pulse width modulation signal to the switching element after the contact welding diagnosis It is configured to perform a voltage diagnosis and perform a relay open fault diagnosis for diagnosing whether a relay open fault has occurred after the contact of the power relay circuit is closed when the precharge voltage reaches a predetermined value. It is characterized by having.

  Still further, an electric power steering apparatus according to a fifth aspect of the present invention is the motor drive control apparatus according to any one of the first to fourth aspects, wherein the electric power steering apparatus generates a steering assist force for the steering system with an electric motor and controls the electric motor. The motor drive control device described in 1 is applied.

  According to the present invention, the switching element connected in series with the precharge resistor that charges the capacitor with the charge is driven by the pulse width modulation signal in the precharge driving unit, so that at least the frequency and duty ratio of the pulse width modulation signal are driven. By changing one of them, the precharge voltage charged to the capacitor can be adjusted arbitrarily, and the optimum precharge voltage can be set according to the power supply voltage fluctuation, and the inrush current can be reliably suppressed. An effect is obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention, in which 1 is a steering wheel, and a steering force applied to the steering wheel 1 from a driver is compared with an input shaft 2a. Is transmitted to a steering shaft 2 having an output shaft 2b. The steering shaft 2 has one end of the input shaft 2a connected to the steering wheel 1 and the other end connected to one end of the output shaft 2b via a steering torque sensor 3 as steering torque detecting means.

The steering force transmitted to the output shaft 2 b is transmitted to the lower shaft 5 via the universal joint 4 and further transmitted to the pinion shaft 7 via the universal joint 6.
The steering force transmitted to the pinion shaft 7 is transmitted to the tie rod 9 via the steering gear 8 and steers steered wheels (not shown). Here, the steering gear 8 is configured in a rack and pinion type having a pinion 8a connected to the pinion shaft 7 and a rack 8b meshing with the pinion 8a, and the rotational motion transmitted to the pinion 8a is linearly moved by the rack 8b. It has been converted to movement.

A steering assist mechanism 10 for transmitting a steering assist force to the output shaft 2b is connected to the output shaft 2b of the steering shaft 2. The steering assist mechanism 10 includes a reduction gear 11 connected to the output shaft 2 b and an electric motor 13 that is a DC motor that generates a steering assist force connected to the reduction gear 11.
The steering torque sensor 3 detects the steering torque applied to the steering wheel 1 and transmitted to the input shaft 2a. For example, the steering torque sensor 3 is a torsion bar (not shown) in which the steering torque is interposed between the input shaft 2a and the output shaft 2b. It is configured to convert to a torsional angular displacement, detect this torsional angular displacement with a magnetic signal, and convert it into an electrical signal.

The detected torque value T output from the steering torque sensor 3 is input to the control device 14. The control device 14 is supplied with power from a battery 15 as a DC power source via an ignition switch 16 and also receives a vehicle speed detection value Vs detected by a vehicle speed sensor 17 in addition to the torque detection value T. A steering assist current command value I _M ^* for causing the electric motor 13 to generate a steering assist force corresponding to the detected torque detection value T and the vehicle speed detection value Vs is calculated, and the calculated steering assist current command value I _M ^* and the motor drive current are calculated. The drive current supplied to the electric motor 13 is feedback-controlled by Im.

  As shown in FIG. 2, the control device 14 performs a predetermined calculation based on the torque detection value T and the vehicle speed detection value Vs and outputs a motor drive signal Ir and a motor rotation direction signal Ds (hereinafter, referred to as a “micro control unit”). (Referred to as MCU) 101, a motor drive circuit 110 that drives the electric motor 13 based on the motor drive signal Ir and the motor rotation direction signal Ds output from the MCU 101, and a power source connected to the battery 15 to the motor drive circuit 110 The motor angular velocity ω is estimated based on the power supply relay circuit 120 that controls supply, the motor current detection circuit 130 that detects the motor drive current Im, the motor terminal voltage Vm, and the motor drive current Im detected by the motor current detection circuit 130. And a motor angular velocity estimation circuit 140 for performing the operation.

  Further, the control device 14 is connected in parallel with the power relay circuit 120 and supplies a precharge voltage Vp to the motor drive circuit 110 side at the relay contact 121 of the power relay circuit 120, and the ignition switch 16 at the time of startup. And a contact voltage detection circuit 170 for detecting a contact voltage Vc on the motor drive circuit 110 side at the relay contact 121 of the power supply relay circuit 120. And.

  Here, as shown in FIG. 2, the motor drive circuit 110 includes four NPN transistors Q1 to Q4 to which the battery voltage Vb of the battery 15 is input via the relay contact 121 of the power supply relay circuit 120. An H bridge circuit 111 that supplies a motor drive current Im for forward / reverse drive to the electric motor 13 and a gate drive circuit 112 that drives and controls the transistors Q1 to Q4 of the H bridge circuit 111 are provided.

Here, the gate drive circuit 112 receives a motor current command value Ir and a motor rotation direction signal Ds output from the MCU 101, which will be described later, and drives the diagonal transistors Q1 and Q3 or Q2 and Q4 based on them. The electric motor 13 is driven to rotate according to the steering torque detection value T.
The power relay circuit 120 includes a normally open relay contact 121 connected to the battery 15, a relay coil 122 that opens and closes the relay contact 121, and a surge absorbing diode 123 connected in parallel with the relay coil 122. One end of the relay coil 122 is connected to the battery 15 via an NPN transistor 124 as a switching element, and the other end is grounded.

  Further, the precharge circuit 150 includes an electrolytic capacitor 151 interposed between a relay contact on the motor drive circuit 110 side of the power supply relay circuit 120 and the ground, a connection point between the electrolytic capacitor 151 and the relay contact 121, and a battery. It is composed of an NPN transistor 152 as a switching element connected to the relay contact on the 15th side, a series circuit 155 including a backflow prevention diode 153 and a precharge resistor 154.

Then, the transistor 124 of the power supply relay circuit 120 and the transistor 152 of the precharge circuit 150 are driven and controlled by a relay drive signal SR and a pulse width modulation signal SP formed by a precharge drive process executed by the MCU 101 described later.
The MCU 101 includes a watch dog timer (WDT) 102 that monitors its own program runaway. Further, the MCU 101 generates a motor drive signal Ir based on the steering torque detection value T, the vehicle speed detection value Vs, and the current detection value Im, and the motor drive signal Ir is input to the motor drive circuit 110.

  As shown in FIG. 2, the MCU 101 includes a ROM (read only memory) 103 for storing a steering assist control processing program, an abnormality detection processing program, and the like, and detection data such as a torque detection value T and a motor drive current Im. In addition, a RAM (Random Access Memory) 104 that stores data and processing results required during the steering assist control process and the precharge drive process executed by the MCU 101 is incorporated.

Further, the MCU 101 executes the steering assist control process and the precharge drive process described above when the ignition switch 16 is turned on and the battery voltage Vb is supplied from the battery 15.
As shown in FIG. 3, in the steering assist control process, first, in step S1, a precharge end flag FP indicating whether or not the precharge drive process is completed in the precharge drive process described later represents the end of the precharge drive. It is determined whether or not it is set to “1”, and when the precharge end flag FP is reset to “0”, it waits until it is set to “1”, and the precharge end flag FP is set to “1”. When "" is set, the process proceeds to step S2.

In this step S2, the steering torque detection value T detected by the steering torque sensor 3 is read, then the process proceeds to step S3, the vehicle speed detection value Vs detected by the vehicle speed sensor 17 is read, then the process proceeds to step S4, and the steering is performed. Based on the detected torque value T and the detected vehicle speed value Vs, a steering assist current command value I _M ^* that is a motor current command value is calculated with reference to a steering assist current command value calculation map shown in FIG.

Here, as shown in FIG. 4, the steering assist current command value calculation map takes the steering torque detection value T on the horizontal axis, the steering assist current command value I _M ^* on the vertical axis, and the vehicle speed detection value Vs as a parameter. The horizontal axis represents the steering torque detection value T, the vertical axis represents the steering assist current command value I _M ^* , and the parabolic curve with the vehicle speed detection value Vs as a parameter. The steering assist current command value I _M ^* is maintained at “0” while the steering torque detection value T is between “0” and the set value Ts1 in the vicinity thereof, and the steering torque detection value T is When the set value Ts1 is exceeded, initially, the steering assist current command value I _M ^* increases relatively slowly with respect to the increase in the steering torque detection value T. However, when the steering torque detection value T further increases, set to the steering assist current command value I _M ^* is increased sharply It is, are set so that the inclination becomes smaller with the increase of the characteristic curve vehicle speed detection value Vs.

Next, the processing proceeds to step S5, reads the motor angular velocity omega estimated by the motor angular speed estimating circuit 140, and then proceeds to step S6, by multiplying the inertia gain K _i to the motor angular velocity omega, is the motor inertia acceleration The inertia compensation value I _i (= K _i · ω) for inertia compensation control for eliminating the torque from the steering torque Tr and obtaining a steering sensation without inertia is calculated, and the steering assist current command value I _M ^* is calculated. The friction compensation value I _f (= K _f · I _M ^* for friction compensation control is used to eliminate the influence of the friction of the power transmission unit and the electric motor on the steering force by multiplying the absolute value by the friction coefficient gain K _f ^. ) Is calculated. Here, the sign of the friction compensation value _If is determined on the basis of the sign of the steering torque T and the steering direction signal for determining whether the steering is increased / returned based on the steering torque T.

Then, the processing proceeds to step S7, to ensure stability of the steering torque T by the differential operation processing to assist characteristic dead band, and calculates the center response improving command value I _r to compensate the static friction, the process proceeds to step S8 The calculated inertia compensation value I _i , friction compensation value _If and center response improvement command value I _r are added to the steering assist current command value I _M ^* to obtain the steering assist current compensation value I _M ^* ′ (= I _M ^* + I _i + I _f + I _r ) is calculated, and then the process proceeds to step S9, where the steering assist current compensation value I _M ^* ′ is differentiated to calculate a differential value Id for feedforward control.

Next, the process proceeds to step S10, where the motor drive current Im is read from the motor current detection circuit 130, and then the process proceeds to step S11, where the current deviation is obtained by subtracting the motor drive current Im from the steering assist current compensation value I _M ^* '. ΔI is calculated, and then the process proceeds to step S12 where the current deviation ΔI is proportionally calculated to calculate a proportional value ΔIp for proportional compensation control, and then the process proceeds to step S13, where the current deviation ΔI is integrated and calculated. Then, the integral value ΔIi for integral compensation control is calculated, and then the process proceeds to step S14, and the motor drive current Ir (= Id + ΔIp + ΔIi) is calculated by adding the differential value Id, the proportional value ΔIp, and the integral value ΔIi. The process proceeds to step S15.

In step S15, the motor drive direction Ir calculated in step S14 and the motor rotation direction signal Ds determined based on the sign of the steering torque detection value T are output to the motor drive circuit 110, and then the process returns to step S1.
Further, as shown in FIG. 5, in the precharge driving process, first, in step S21, it is determined whether or not a predetermined time t1 has elapsed from the start of the process. The process waits until the predetermined time t1 elapses. When the predetermined time t1 has elapsed, the process proceeds to step S22, and the comparison can be made so that the precharge resistor 154 can have the necessary minimum resistance value R _MIN for the transistor 152 of the precharge circuit 150. The output of a pulse width modulation signal SP having a predetermined low frequency is started.

Next, the process proceeds to step S23, where it is determined whether or not the predetermined time t2 has elapsed since the start of the output of the pulse width modulation signal SP. When the predetermined time t2 has not elapsed, the process waits until this elapses. When the predetermined time t2 has elapsed, the process proceeds to step S24, and the high level relay drive signal SR is output to the switching element 124 of the power supply relay circuit 120, and then the process proceeds to step S25.

In step S25, the output of the pulse width modulation signal SP to the precharge circuit 150 is stopped, and then the process proceeds to step S26 where the precharge end flag FP that has been reset to “0” by the initialization process is set to “1”. Then, the precharge driving process is terminated.
The precharge drive process in FIG. 5 corresponds to the precharge drive unit.
Next, the operation of the first embodiment will be described.

  Now, it is assumed that the vehicle is stopped and the ignition switch 16 is off. In this state, the battery voltage Vb of the battery 15 is supplied to the power supply circuit 160, but since the ignition switch 16 is in the OFF state, the supply of power into the control device 14 is stopped, and the MCU 101 operates. It has stopped. For this reason, the transistor 124 of the power supply relay circuit 120 is turned off, the relay coil 122 is in a non-energized state, the relay contact 121 is opened, and the transistor 152 of the precharge circuit 150 is also turned off. Thus, the supply of the precharge voltage Vp to the motor drive circuit 110 side at the relay contact 121 of the power supply relay circuit 120 is stopped.

  Therefore, since the battery voltage Vb is not supplied to the motor drive circuit 110 and the steering assist control process and the precharge drive process are not executed by the MCU 101, the transistors Q1 to Q4 of the H bridge circuit 111 of the motor drive circuit 110 are all in the off state. Thus, the supply of DC power to the electric motor 13 is stopped and the electric motor 13 is in a rotation stop state, and the generation of the steering assist force by the electric motor 13 is stopped. In this state, the steering wheel 1 is rotated only by the steering force transmitted from the driver.

When the ignition switch 16 is turned on in the steering assist stop state, the control power is supplied from the power supply circuit 160 into the control device 14 accordingly, and the MCU 101 is activated.
Therefore, the MCU 101 starts executing the steering assist control process of FIG. 3 and the precharge drive process of FIG. 5, but the precharge end flag FP is reset to “0” by the initialization process. In step S1, the timer interrupt process is terminated as it is, and the motor drive signal Ir and the rotation direction signal Ds are not output to the motor drive circuit 110, and the motor drive circuit 110 maintains the stopped state.

  On the other hand, in the precharge driving process, as shown in FIG. 6, when the ignition switch 16 is turned on at time T1, as shown in FIG. 6A, the precharge is performed at time T2 when a predetermined time t1 has elapsed from time T1. The output of a relatively low frequency pulse width modulation signal SP that minimizes the resistance value R of the precharge resistor 154 to the NTN transistor 152 of the charge circuit 150 is started.

  When this pulse width modulation signal SP is supplied to the gate of the NTN transistor 152 of the precharge circuit 150, the NTN transistor 152 is repeatedly turned on and off, so that the electrolytic capacitor 151 is charged based on the battery voltage Vb. The For this reason, the motor drive circuit side contact voltage Vc of the power supply relay circuit 120 gradually increases with a time constant determined by the capacities of the precharge resistor 154 and the electrolytic capacitor 151 as shown in FIG. Increase to a precharge voltage Vp lower than the battery voltage Vb determined by the frequency of the pulse width modulation signal SP and the resistance value R of the precharge resistor 154. When the precharge voltage Vp is reached at time T3, the precharge voltage Vp is maintained thereafter. To do.

Thereafter, a high level relay drive signal SR is output to the NTN transistor 124 of the power supply relay circuit 120 at a time T4 when a predetermined time t2 has elapsed from the time T2, and the relay coil 122 is energized from the battery 15, The relay coil 122 is energized and the relay contact 121 is closed as shown in FIG.
For this reason, when the battery voltage Vb is supplied to the motor drive circuit 110 via the relay contact 121 of the power supply relay circuit 120, the motor drive circuit 110 becomes operable. At this time, since the potential difference between the battery voltage Vb on the battery 15 side of the relay contact 121 and the precharge voltage Vp on the motor drive circuit 110 side is small, the inrush current flowing to the electrolytic capacitor 151 through the relay contact 121 is a small value. Therefore, contact welding of the relay contact 121 can be reliably prevented.

  In addition, since the frequency of the pulse width modulation signal SP supplied to the transistor 152 of the precharge circuit 150 is set to a value that decreases the resistance value R of the precharge resistor 154, the time constant when charging the electrolytic capacitor 151 is set. And the precharge voltage Vp can be increased, and the potential difference between both ends of the relay contact 121 of the power supply relay circuit 120 can be reduced to ensure the inrush current through the relay contact 121 of the power supply relay circuit 120. Can be suppressed.

  Incidentally, when the frequency of the pulse width modulation signal SP output to the transistor 152 of the precharge circuit 150 in the precharge driving process shown in FIG. 5 is low, the power supply relay circuit 120 is a contact on the motor drive circuit 110 side in the relay contact 121. The voltage change when the relay contact 121 at the voltage Vc changes from the open state to the closed state is a state where the precharge voltage Vp by the precharge circuit 150 is relatively low (for example, 4 V) as shown in FIG. To a battery voltage Vb (for example, 12V), the potential difference between the two is relatively large, so that the inrush current in the precharge circuit using the conventional voltage dividing resistor shown in FIG. A small but relatively large inrush current of about 44 A occurs. Here, in the precharge circuit using the voltage dividing resistor of the conventional example, as shown in FIG. 7C, the precharge voltage Vp changes from a considerably low state (for example, 2V) to the battery voltage Vb (for example, 12V). As a result, a considerably large inrush current of about 56 A is generated, and when the battery voltage Vb becomes high, the increase in the precharge voltage Vp is small. is there.

  However, in this embodiment, since the frequency of the pulse width modulation signal SP can be adjusted, the voltage change when the relay contact 121 changes from the open state to the closed state as shown in FIG. 7B. The precharge voltage Vp by the precharge circuit 150 is changed from a relatively high state (for example, 8V) to the battery voltage Vb (for example, 12V), and since the potential difference between the two is small, the inrush current is suppressed to about 15A. Thus, contact welding of the relay contact 121 can be reliably prevented.

On the other hand, immediately after time T4, the output of the pulse width modulation signal SP to the transistor 152 of the precharge circuit 150 is stopped and the precharge end flag FP is set to “1”.
As described above, when the precharge end flag FP is set to “1”, the steering assist control process shown in FIG. 3 shifts from step S1 to step S2, and the steering torque T is read from the steering torque sensor 3. Next, the vehicle speed detection value V is read from the vehicle speed sensor 17 (step S3), and the steering auxiliary current command value I _M is referred to based on the steering torque T and the vehicle speed detection value V with reference to the steering auxiliary current command value calculation map shown in FIG. ^* Is calculated (step S4).

On the other hand, the motor angular velocity ω estimated by the motor angular velocity estimation circuit 140 is read (step S5), the inertia compensation value I _i for inertia compensation control is calculated based on the motor angular velocity ω, and the friction compensation value for friction compensation control is calculated. calculating the I _f (step S6), and further the steering torque T differential operation to calculate a center response improving command value I _r (step S7), and these inertia compensation value I _i, friction compensation value I _f and the center response The steering assist current compensation value I _M ^* ′ is calculated by adding the performance improvement compensation value I _r to the steering assist current command value I _M ^* (step S8).

The steering assist current compensation value I _M ^* ′ is differentiated to calculate a differential value Id for differential compensation control in the feedforward control (step S9), and then the motor drive current Im is read (step S10). Next, the motor current detection value Im is subtracted from the steering assist current compensation value I _M ^* ′ to calculate a current deviation ΔI (step S11), and the calculated current deviation ΔI is subjected to proportional calculation processing to obtain a proportional value for proportional compensation control. In addition to calculating ΔIp, integral calculation processing is performed to calculate an integral value ΔIi for integral compensation control (steps S12 and S13), and then the differential value Id, the proportional value ΔIp, and the integral value ΔIi are added to obtain the motor drive signal Ir. Is calculated (step S14).

  Then, by outputting the rotation direction signal Ds determined based on the calculated motor drive signal Ir and the sign of the steering torque T to the gate drive circuit 112 of the motor drive circuit 110, the drive current from the motor drive circuit 110 to the electric motor 13 is output. , The steering assist force corresponding to the steering torque applied to the steering wheel 1 is generated by the electric motor 13, and the steering assist force is transmitted to the output shaft 2 b via the reduction gear 11.

At this time, in a so-called stationary state in which the steering wheel 1 is steered while the vehicle is stopped, the characteristic curve of the steering assist current command value calculation map shown in FIG. Since the steering assist current command value I _M ^* is calculated, a large steering assist force can be generated by the electric motor 13 to perform light steering.
On the other hand, when the vehicle starts and exceeds the predetermined vehicle speed, the gradient of the characteristic line of the steering assist current command value calculation map shown in FIG. 4 becomes smaller, so that even if the steering torque T is large, a small steering assist current command value I _M ^* Therefore, the steering assist force generated by the electric motor 13 is reduced, and the steering of the steering wheel 1 can be suppressed from becoming too light and optimal steering can be performed.

In the above first embodiment, the pre-charge driving process, as well as reduce the time constant to reduce the resistance value of the pre-charge resistor, a pulse width modulated signal SP so as to increase the pre-charge voltage Although the case of setting the frequency has been described, the present invention is not limited to this, and the duty ratio of the pulse width modulation signal SP may be set, and both the frequency and the duty ratio of the pulse width modulation signal SP are set. You may make it do.

Next, a second embodiment of the present invention will be described with reference to FIGS.
In the second embodiment, the battery voltage Vb is detected, and the precharge voltage Vp is set based on the detected battery voltage Vb.
That is, in the second embodiment, as shown in FIG. 8, the precharge driving process executed by the MCU 101 is the battery voltage Vb before step S21 in the precharge driving process of FIG. 5 in the first embodiment described above. And a step of setting the frequency f of the pulse width modulation signal SP supplied to the transistor 152 of the precharge circuit 150 with reference to the frequency setting map shown in FIG. 9 based on the read battery voltage Vb. 32 is inserted.

Here, the frequency setting map of FIG. 9 is composed of a characteristic diagram with the battery voltage on the horizontal axis and the frequency on the vertical axis. When the battery voltage Vb is the reference voltage Vbn, the frequency f is the intermediate frequency f _M. Thus, the frequency f is set so as to increase or decrease from the intermediate frequency f _M as the battery voltage increases or decreases from the reference voltage Vbn.
Further, the same processing as in FIG. 5 is executed except that the pulse width modulation signal SP having the frequency f set in step S22 is output to the transistor 152 of the precharge circuit 150, and FIG. The corresponding step numbers are assigned the same step numbers, and detailed descriptions thereof are omitted.

The process of FIG. 8 corresponds to the precharge drive unit.
According to the second embodiment, the ignition switch 16 is switched from the OFF state to the ON state, and the battery voltage Vb is supplied to the power supply circuit 160, whereby the MCU 101 is operated by the operation voltage output from the power supply circuit 160. 8 is started, the precharge driving process of FIG. 8 is started, the battery voltage Vb at that time is read (step S31), and then the frequency setting map of FIG. 9 is read based on the read battery voltage Vb. The frequency of the pulse width modulation signal SP corresponding to the battery voltage Vb is set with reference.

That is, when the battery voltage Vb is normal value Vbn (e.g. 12V) is the frequency f of the pulse width modulated signal SP is set to the intermediate frequency f _M, if the battery voltage Vb is higher than the normal value Vbn is , the frequency f is set to an intermediate frequency f _M higher high frequency f _H, when the battery voltage Vb is lower than the normal value Vbn the contrary, the frequency f is set to an intermediate value f lower than the _M lower frequency f _L .

Therefore, when the battery voltage Vb is the normal value Vbn, the intermediate frequency f _M is set to be the same as that of the first embodiment described above, so that the relay contact 121 of the power relay circuit 120 is the same as in the first embodiment. The potential difference between the battery 15 side and the motor drive circuit 110 side can be lowered to reliably suppress the inrush current.
When the battery voltage Vb from this state is higher voltages Vbh than the normal value Vbn, by referring to the frequency setting map shown in FIG. 9 this battery voltage Vbh based, set at an intermediate frequency f _M higher high frequency f _H Is done.

Therefore, since the pulse width modulation signal SP having the high frequency f _H is supplied to the transistor 152 of the precharge circuit 150, the precharge voltage Vp obtained through the transistor 152 is indicated by a solid line L11 in FIG. Thus, it becomes higher according to the battery voltage Vb.
As a result, the potential difference between the battery contact 15 side and the motor drive circuit 110 side of the relay contact 121 of the power relay circuit 120 is reduced, and the relay coil 122 of the power relay circuit 120 is energized and the relay contact 121 is closed. In addition, the inrush current flowing through the relay contact 121 is greatly reduced, and this inrush current is a substantially constant value of about a dozen A regardless of the change in the battery voltage Vb as shown by the solid line L21 in FIG. 10B. Thus, welding of the relay contact 121 can be reliably prevented.

Similarly, when the battery voltage Vb becomes a voltage Vbl lower than the normal value Vbn, the low frequency f _L lower than the intermediate frequency f _M is set by referring to the frequency setting map shown in FIG. 9 based on the battery voltage Vbl. In addition, the potential difference between the battery contact 15 side and the motor drive circuit 110 side of the relay contact 121 of the power supply relay circuit 120 can be maintained in an optimum state that prevents an inrush current.

  Incidentally, in the conventional example in which a voltage dividing resistor is used in the precharge circuit, the precharge voltage Vp is changed with respect to the change of the battery voltage Vb as shown by a straight line L12 shown by a one-dot chain line in FIG. Therefore, the inrush current increases as the battery voltage Vb increases, as shown by the dashed line L22 in FIG. 10B, and there is a possibility that contact welding of the relay contact 121 occurs. is there.

However, in the second embodiment, the precharge voltage Vp increases as the battery voltage Vb increases, and the potential difference between the two can be maintained appropriately. Therefore, the inrush current can be reliably suppressed. .
Next, a third embodiment of the present invention will be described with reference to FIG.
In the third embodiment, contact welding diagnosis, precharge voltage diagnosis, and relay open failure diagnosis of the relay contact 121 of the power supply relay circuit 120 are performed during the precharge driving process.

  That is, in the third embodiment, as shown in FIG. 11, in the precharge driving process of FIG. 5 in the first embodiment described above, the determination result in step S21 has passed a predetermined time t1. When the process proceeds to step S40, it is determined whether or not a contact welding diagnosis flag FD1 to be described later is reset to “0”, and when this is reset to “0”, it is determined that it is normal. The process proceeds to step S22, and when it is set to “1”, it is determined that there is an abnormality, and the precharge driving process is terminated.

When the determination result in step S21 is that the predetermined time t1 has not elapsed, the process proceeds to step S41, and the contact voltage Vc on the motor drive circuit 110 side in the relay contact 121 of the power supply relay circuit 120 is read. .
Next, the process proceeds to step S42, and contact welding diagnosis is performed to determine whether or not the read contact voltage Vc is less than the welding determination threshold value Vcth. When Vc <Vcth, it is determined that no contact welding has occurred. Then, the process proceeds to step S43, the contact welding diagnosis flag FD1 is reset to “0”, and then the process returns to step S21. When Vc ≧ Vcth, it is determined that contact welding has occurred, and the process proceeds to step S44. After the contact welding diagnosis flag FD1 is set to “1”, the process returns to step S21.

When the determination result in step S23 is that the predetermined time t2 has not elapsed, the process proceeds to step S45, and the contact voltage Vc on the motor drive circuit 110 side in the relay contact 121 of the power supply relay circuit 120 is read. Next, the process proceeds to step S46, and it is determined whether or not the precharge circuit 150 is normal by determining whether or not the read contact voltage Vc is within the range of the minimum voltage threshold V _MIN and the maximum voltage threshold V _MAX. Diagnose.

If this determination result is V _MIN ≦ Vc ≦ V _MAX, it is determined that the precharge circuit 150 is normal, the process proceeds to step S47, and after the precharge voltage diagnosis flag FD2 is reset to “0”, the step is performed. Returning to S23, when Vc <V _MIN, it is determined that the precharge circuit 150 has failed, and the process proceeds to step S48, the precharge voltage diagnosis flag FD2 is set to “1”, and then the process proceeds to step S23. Return.

  Further, after step S26, step S49 is provided. In step S49, it is determined whether or not a predetermined time t3 has elapsed since the relay drive signal SR for closing the relay contact 121 is output, and the predetermined time t3 is set. When the predetermined time t3 has not elapsed, the process proceeds to step S50, and the contact voltage Vc on the motor drive circuit 110 side at the relay contact 121 of the power relay circuit 120 is read again. The process proceeds to step S51.

In step S51, the contact voltage Vc is subjected to relay open failure diagnosis equal to or larger than the allowable lower limit Vb _L of the battery voltage Vb, the contact voltage Vc is larger than the allowable lower limit Vb _L of the battery voltage Vb In some cases, it is determined that the relay contact 121 is closed and no relay open failure has occurred, the process proceeds to step S52, the relay open failure diagnosis flag FD3 is reset to "0", and then the process returns to step S49.

When the contact voltage Vc is less than the allowable lower limit value Vb _L of the battery voltage Vb, it is determined that the relay contact 121 is not closed and a relay open failure has occurred, and the process proceeds to step S53, where the relay open failure diagnosis flag FD3 Is set to “1”, and the process returns to step S49.
Although not shown, when the MCU 101 collects various diagnostic flags FD1 to FD3 and the contact welding diagnosis flag FD1 is set to “1”, an alarm display indicating the contact welding state is displayed to the driver. When the precharge voltage diagnosis flag FD2 is set to "1", a warning display indicating a failure of the precharge circuit 150 is displayed within the driver's visual recognition range, and the relay open failure diagnosis flag FD3 is When the threshold is set to “1”, a warning display process for displaying a warning display indicating an open failure of the relay contact 121 within the visual recognition range of the driver is executed.

Next, the operation of the third embodiment will be described.
Now, by turning on the ignition switch 16, when the battery voltage Vb is supplied to the power supply circuit 160 and the MCU 101 starts executing various processes, first, the ignition switch 16 is turned on in the precharge driving process shown in FIG. The contact welding diagnosis process in steps S41 to S44 is executed until the predetermined time t1 elapses after the state is reached, and as shown in FIG. 12, the power relay circuit is activated until the predetermined time t1 elapses. When the contact voltage Vc on the motor drive circuit 110 side of the 120 relay contacts 121 is less than the welding determination threshold value Vcth and is substantially “0”, it is determined that no contact welding has occurred at the relay contact 121 and the contact welding diagnosis flag FD1. Is reset to “0”. In this case, no warning is displayed in the warning process executed by the MCU 101.

  However, if an overcurrent such as an inrush current flows through the relay contact 121 during the previous precharge drive process and steering assist control process and the relay contact 121 is welded and remains closed, the contact welding diagnosis process of steps S41 to S44. However, the contact voltage Vc is not substantially “0”, but is equal to or close to the battery voltage Vb, depending on the welding state, and is equal to or higher than the welding determination threshold value Vcth. Therefore, the process proceeds from step S42 to step S44. Then, the contact welding diagnosis flag FD1 is set to “1”.

For this reason, in the warning processing of the MCU 101, the warning display indicating the welding abnormality of the relay contact 121 is displayed within the visual recognition range of the driver, so that the driver can recognize that the welding of the relay contact 121 has occurred. .
On the other hand, as shown in FIG. 12, the precharge voltage diagnosis process in steps S45 to S48 is performed from the time T2 when the pulse width modulation signal SP is output to the transistor 152 of the precharge circuit 150 until the predetermined time t2 elapses. When the contact voltage Vc is read and the contact voltage Vc is approximately 0 V, the precharge circuit 150 is maintained in the off state or the precharge circuit 150 or the battery connection system is disconnected due to disconnection. It is determined that the precharge circuit 150 is not operating at all, and the precharge voltage diagnosis flag FD2 is set to “1”.

  Similarly, in the precharge voltage diagnosis process, when the contact voltage Vc is substantially the battery voltage Vb, the transistor 152 of the precharge circuit 150 is not inverted to the off state, and an abnormal state that maintains the on state has occurred, or the transistor It is determined that a power fault occurs between 152 and the electrolytic capacitor 151 and the precharge circuit 150 does not operate normally, and the precharge voltage diagnosis flag FD2 is set to “1”.

As described above, when the precharge voltage diagnosis flag FD2 is set to “1” in the precharge voltage diagnosis process, the warning display is performed within the driver's visual recognition range in the warning process of the MCU 101 also in this case. Can recognize the failure of the precharge circuit 150.
Further, when the precharge by the precharge circuit 150 is completed and a high level relay drive signal SR is output to the transistor 124 of the power supply relay circuit 120 to close the relay contact 121, the relay open of steps S49 to S53 is performed. Fault handling is performed.

At this time, when the relay contact 121 is normally closed, the contact voltage Vc becomes the battery voltage Vb, so that the contact voltage Vc does not drop below the allowable lower limit value. The flag FD3 is reset to “0”.
However, when the relay contact 121 is not closed, the supply of the battery voltage Vb through the relay contact 121 is cut off, so that the supply of the pulse width modulation signal SP to the transistor 152 of the precharge circuit 150 is continued. In the meantime, the contact voltage Vc maintains the precharge voltage Vp, but when the supply of the pulse width modulation signal SP to the transistor 152 is stopped, the motor drive circuit 110 drives the H bridge circuit 111 to perform electrolysis. As the electric charge charged in the capacitor 151 is discharged, the contact voltage Vc decreases to substantially “0” and becomes less than the allowable lower limit value Vb _L. For this reason, the relay open failure diagnosis flag FD3 is set to “1”, and warning display is performed within the driver's viewing range in the warning processing of the MCU 101. In this state, since the battery voltage Vb cannot be supplied to the motor drive circuit 110, the electric motor 13 cannot be driven, and the steering assist control is stopped.

  However, when this relay open failure occurs, the power supply to the motor drive circuit 110 is cut off through the power relay circuit 120, but the battery voltage Vb can be supplied to the motor drive circuit 110 through the precharge circuit 150. Therefore, by supplying a relatively low frequency pulse width modulation signal SP to the transistor 152 of the precharge circuit 150 when the relay open failure diagnosis flag FD3 is set to “1” in the precharge driving process. The minimum required drive power can be supplied to the motor drive circuit 110 via the precharge circuit 150, and the steering wheel 1 can be steered with less steering force than manual steering. Request to replace the control device 14 by forwarding to a factory etc. It can be.

  In the first to third embodiments, the case where the frequency f of the pulse width modulation signal SP supplied to the transistor 152 of the precharge circuit 150 is changed in the precharge driving process has been described. However, the present invention is not limited to this. Instead, the duty ratio may be changed with the frequency f of the pulse width modulation signal SP being constant, or both the frequency and the duty ratio may be changed.

In the first to third embodiments, the case where the PNP transistors 124 and 152 are applied as the switching elements of the power relay circuit 120 and the precharge circuit 150 has been described. However, the present invention is not limited to this. Any other switching element such as a PNP transistor, a field effect transistor, or a relay can be applied.
Furthermore, in the first to third embodiments, the case where the H bridge circuit 111 that drives the DC electric motor 13 is applied as the motor drive circuit 110 has been described. However, the present invention is not limited to this. When a multiphase brushless motor is applied as the motor 13, an inverter circuit is applied as the motor drive circuit 110, and in response to this, in the steering assist control processing of the MCU 101, each phase voltage command for the multiphase brushless motor is based on the steering torque. A value is generated, and a deviation between the voltage command value of each phase and the detected drive current value of the brushless motor is calculated, and current feedback processing may be performed.

  In the first to third embodiments, the switching element of the precharge circuit 150 is disposed on the battery 15 side. However, the present invention is not limited to this, and the precharge resistor 154 and the electrolytic circuit are not limited thereto. A precharge coil may be applied instead of the precharge resistor 154.

Furthermore, in the first to third embodiments, the case where the precharge driving unit is configured by software performed by the precharge process executed by the MCU 101 has been described. However, the present invention is not limited to this. The drive unit may be configured by hardware such as a timer, a triangular wave generation circuit, a set voltage generation circuit, and a voltage comparison circuit.
In the first to third embodiments, the case where both the steering assist control process and the precharge drive process are executed by the MCU 101 has been described. However, the present invention is not limited to this, and calculation processes other than the MCU are performed. A device may be applied, and the steering assist control process and the precharge drive process may be executed by separate processing units.

  Furthermore, in the first to third embodiments, the case where the present invention is applied to a so-called column-type electric power steering apparatus in which the steering assist mechanism 10 is provided in the column shaft portion has been described. However, the present invention is not limited to this. Instead, the present invention can also be applied to a so-called rack-type electric power steering device in which a steering assist mechanism is provided in the steering gear 8, and further, an in-vehicle device such as an electric brake device other than the electric power steering device, a power window device, etc. The present invention can be applied to drive devices using other electric motors.

It is a schematic structure figure showing one embodiment of the present invention. It is a block diagram which shows the specific structure of the control apparatus of FIG. It is a flowchart which shows an example of the steering assistance control processing procedure performed with MCU. It is a characteristic diagram which shows a steering auxiliary current command value calculation map. It is a flowchart which shows an example of the precharge drive processing procedure performed by MCU. It is a signal waveform diagram with which it uses for description of the operation | movement in 1st Embodiment. It is a wave form diagram which shows a contact voltage and inrush current when a frequency is changed. It is a flowchart which shows an example of the precharge drive processing procedure of MCU showing the 2nd Embodiment of this invention. It is a characteristic diagram which shows the frequency setting map which shows the relationship between a battery voltage and a frequency. It is a characteristic diagram with which it uses for description of the operation | movement in 2nd Embodiment. It is a flowchart which shows an example of the precharge drive processing procedure of MCU showing the 3rd Embodiment of this invention. It is a signal waveform diagram with which it uses for description of the operation | movement in 3rd Embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering wheel, 2 ... Steering shaft, 3 ... Steering torque sensor, 8 ... Steering gear, 10 ... Steering assist mechanism, 13 ... Electric motor, 14 ... Control device, 15 ... Battery, 16 ... Ignition switch, 17 ... Vehicle speed sensor , 101 ... MCU, 110 ... motor drive circuit, 111 ... H bridge circuit, 112 ... gate drive circuit, 120 ... power relay circuit, 121 ... relay contact, 122 ... relay coil, 124 ... transistor, 130 ... motor current detection circuit, DESCRIPTION OF SYMBOLS 140 ... Motor angular velocity estimation circuit, 150 ... Precharge circuit, 151 ... Electrolytic capacitor, 152 ... Transistor, 154 ... Precharge resistor, 155 ... Series circuit, 160 ... Power supply circuit, 170 ... Contact voltage detection circuit

Claims (5)

A motor drive control device comprising: an electric motor; and a motor drive circuit that drives and controls the electric motor based on electric power from a DC power source,
A power supply relay circuit interposed between the DC power supply and the motor drive circuit, and a precharge circuit connected in parallel with the power supply relay circuit,
The precharge circuit includes a capacitor connected between a contact on the motor drive circuit side of the power relay circuit and the ground, a switching element connected in parallel with the power relay circuit and driven by a pulse width modulation signal, and the switching a series circuit of the precharge resistors set the precharge voltage to a small value that can be controlled by the pulse width modulated signal to said capacitor when driving element by said pulse width modulated signal, the precharge voltage for the previous SL capacitor And a precharge drive unit that outputs the pulse width modulation signal that approximates the power supply voltage of the DC power supply to the switching element . The precharge driving unit, to claim 1, characterized in that is configured to preset at least one of the frequency and duty ratio of the pulse width modulation signal so as to approach the precharged voltage to the DC power supply voltage The motor drive control device described.   A power supply voltage detection unit configured to detect a power supply voltage of the DC power supply, wherein the precharge drive unit suppresses the frequency of the pulse width modulation signal and the inrush current according to the power supply voltage detected by the power supply voltage detection unit; The motor drive control device according to claim 1, wherein the motor drive control device is configured to be controlled as described above.   The precharge driving unit performs contact welding diagnosis for diagnosing whether or not contact welding of the power relay circuit has occurred before outputting the pulse width modulation signal to the switching element, and after the contact welding diagnosis, the pulse width A precharge voltage diagnosis is performed to output a modulation signal to the switching element to diagnose whether the precharge voltage is normal. When the precharge voltage reaches a predetermined value, the contact of the power relay circuit is closed. The motor drive control device according to any one of claims 1 to 3, wherein the motor drive control device is configured to perform relay open failure diagnosis for diagnosing whether or not a relay open failure has occurred.   The motor drive control device according to any one of claims 1 to 4 is applied as a motor drive control device that generates a steering assist force for a steering system with an electric motor and controls the drive of the electric motor. Electric power steering device.

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