JP5396861B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus that uses a motor to apply a steering assist force to a steering mechanism of a vehicle such as an automobile to assist a steering operator, and in particular, includes two drive systems, one of which is a drive system. Thus, for example, the present invention relates to an electric power steering apparatus capable of continuing steering assist even when a failure occurs in a motor drive circuit.

  2. Description of the Related Art In vehicles such as automobiles, an electric power steering device that applies a steering assist force (steering assist force) to a steering wheel by a rotational torque of a motor when a steering person steers is widely used.

  Here, a general electric power steering apparatus will be described with reference to the drawings.

FIG. 10 is a diagram showing a schematic configuration of a conventional electric power steering apparatus.
As shown in FIG. 10, the shaft 82 directly connected to the steering handle 81 that is steered by the driver is coupled to the tie rod 83 of the wheel 84 via the speed reducer 9 and the rack and pinion mechanism 85.

FIG. 11 is a diagram illustrating a configuration of a speed reducer of a conventional electric power steering apparatus.
As shown in FIG. 11, the motor 8 that applies the steering assist force to the steering handle 81 is coupled coaxially with the worm 91 of the speed reducer 9, and the worm wheel 92 that meshes with the worm 91 is coupled with the shaft 82. Yes. As a result, the motor 8 is mechanically coupled to the steering mechanism and can apply a steering assist force to the steering mechanism.

As shown in FIG. 10, a control device (hereinafter also referred to as ECU) 6 is connected to the motor 8 as a control unit of the motor 8, and the steering detected by the torque sensor 7 attached to the shaft 82 in the ECU 6. A current command value, which is an assist command, is calculated based on the steering torque signal of the handle 81, and a current controlled based on the current command value is supplied to the motor 8.
In this way, assist control is realized and steering assist of the steering person is performed.

Next, a schematic configuration of a conventional ECU will be described.
FIG. 12 is a block diagram showing a schematic configuration of a conventional ECU.
The ECU 6 is mainly composed of a CPU system, and controls the motor 8 by executing a program stored in an internal memory. More specifically, the ECU 6 includes an MCU 61, a driver circuit 62, a motor drive circuit 63, a current detection circuit 64, a motor angle detector 65, and the like.

  Then, by executing a program stored in the internal memory of the MCU 61, the program is supplied to the motor 8 based on the steering torque signal detected by the torque sensor 7 and the motor angle detected by the motor angle detector 65. A current control value is generated, and a PWM (pulse width modulation) signal having a duty ratio determined based on the current control value and the motor current detected by the current detection circuit 64 is supplied to the driver circuit 62.

  Based on the PWM signal supplied from the MCU 61, the driver circuit 62 has six power MOSFETs (field effect transistors, hereinafter also referred to as FETs) Q61 to Q66 constituting the H bridge circuit of the motor drive circuit 63. A pulse voltage to be supplied is generated.

  The motor drive circuit 63 repeatedly turns on and off the FETs of the upper and lower arms connected in series by the pulse voltage supplied from the driver circuit 62, and supplies the current that flows at this time to the motor 8 to drive the motor 8 to rotate. Let

  Further, in the conventional electric power steering apparatus configured as described above, a rack end mechanism is provided with respect to the rack and pinion mechanism 85 in order to prevent the steering wheel 81 from turning beyond a certain level. When the steering handle 81 is steered left and right from the neutral position to a predetermined rack end and the turning angle of the steering handle 81 reaches the maximum, the steering handle 81 cannot be turned in the same direction any more. For this reason, when the steering handle 81 is steered close to the rack end and a large steering torque is applied to the steering handle 81 by the steering person, a large steering assist force is applied from the motor 8 to the steering mechanism. At the rack end of the rack and pinion mechanism 85, for example, an end stopper collides with another member, and a large impact force is applied to the entire steering mechanism via the rack and pinion mechanism 85, and an impact sound is generated. Thus, the steering feeling of the steering wheel is deteriorated, and in some cases, the torque transmission system (mechanical system) such as the speed reducer 9 or the rack and pinion mechanism 85 is damaged or deformed.

  In order to avoid this, conventionally, when the rack and pinion mechanism 85 approaches the rack end (hereinafter also referred to as “during rack end”), the motor drive circuit 63 supplies the motor 8 to the rack 8. The current to be applied is limited, thereby reducing the impact force applied to the steering mechanism.

  By the way, the electric power steering device configured as described above is widely used not only in light cars and small cars, but also in automobiles with a large vehicle weight such as SUV (Sport Utility Vehicle) in recent years. Yes. These large automobiles require a larger steering assist force than light and small automobiles due to their large vehicle weight, and use high-power motors. For this reason, for example, if a failure occurs in the above-described motor drive circuit 63 or the like during driving of the vehicle, the motor 8 is stopped and the steering assist force is no longer applied to the steering handle 81. This increases the torque required for the steering wheel, which impairs the steering feeling of the steering wheel.

  In order to solve such a problem, conventionally, two sets of motor drive circuits are provided in the ECU to form a two-system drive system. During normal operation, one motor drive circuit drives the motor, and one motor drive circuit It is known that when a failure occurs, the steering assist is continued by switching to the other motor drive circuit and driving the motor (see, for example, Patent Document 1).

  When a brushless motor is used as the motor 8, in order to drive and control the motor 8, a rotation angle detection device such as a resolver is generally attached to the motor 8, and the rotation angle detection device fails. In this case, the steering assist force is lost, and the torque required for the steering of the steering wheel increases, which may cause the steering wheel to deteriorate or feel uneasy.

  Therefore, it is proposed that the motor is controlled by the rotation angle of the motor estimated by the motor rotation angle estimation means based on the steering torque or the calculation value calculated by the steering torque when the rotation angle detection device is abnormal. (For example, refer to Patent Document 2). Further, there has been proposed an apparatus in which the rotational angular velocity of the motor and the relative rudder angle of the steered wheel are obtained from the back electromotive force of the motor and the rotational angle detection device is not required (for example, see Patent Document 3).

Japanese Patent No. 3696384 JP 2007-118823 A Japanese Patent Publication No. 7-25313

  However, in the above-described conventional example, in order to prevent interference between the two sets of motor drive circuits, between each motor drive circuit and the power source, each motor drive circuit and each phase drive coil of the motor are connected. It was necessary to provide an open / close switch in the middle of all connection lines to be connected.

  In addition, in an electric power steering device applied to a large vehicle, since a large steering assist force is required, the output of the motor inevitably increases. Therefore, the open / close switch must be capable of opening and closing a large current. I had to. This has been a factor in increasing the size and cost of the electric power steering apparatus.

  Furthermore, when switching the motor drive circuit, a time lag due to the open / close switch occurs, which causes a problem that the feeling of steering remains uncomfortable. To eliminate this time lag, it is sufficient to eliminate the open / close switch and always operate the two sets of motor drive circuits in parallel. In this case, it is necessary to detect which of the two sets of motor drive circuits has failed. Was difficult.

  Since the failed motor drive circuit cannot be separated, the failed motor drive circuit adversely affects the non-failed motor drive circuit and the motor cannot be driven normally. Continuous realization was difficult.

  In addition, regarding the mitigation of the impact force applied to the steering mechanism when the rack and pinion mechanism approaches the rack end, the above-described conventional method can be applied to a small vehicle such as a passenger car with a light vehicle weight. In automobiles with a heavy vehicle weight, it is inevitable to increase the output of the electric power steering device to generate a large steering assist force as described above. Therefore, it is sufficient to limit the current supplied to the motor at the rack end. Effects may not be obtained.

  Furthermore, when a large impact force repeatedly acts on the steering mechanism, it is necessary to use a material with excellent mechanical strength that can sufficiently withstand breakage or deformation, which increases manufacturing costs. is there.

  In addition, the electric power steering control device described in Patent Document 2 and the power steering device described in Patent Document 3 have only one motor that generates steering assist force, and have two completely independent drive systems. There was room for further improvement in order to realize a comfortable steering feeling.

The present invention has been made in view of the above-described circumstances, and an object thereof is an electric power steering apparatus configured by two drive systems, in which a failure has occurred in, for example, a motor drive circuit in the first system. There is also provided an electric power steering device that can continue steering assist without causing anxiety or discomfort to the steering person, that is, without impairing the steering feeling, and that can be realized at a small size and at low cost. There is.
Furthermore, an object of the present invention is to provide an electric power steering mechanism capable of preventing an impact force at the rack end of the rack and pinion mechanism from being applied to the steering mechanism by using the second system at normal times. There is.
In addition, an object of the present invention is to provide an electric power steering device capable of continuing steering assist with the first system drive system capable of advanced control when only the rotation angle detection device fails. .

The above-described object of the present invention is achieved by the following configuration.
(1) An electric power comprising: a motor mechanically coupled to the steering mechanism; and a control unit for controlling the motor based on at least a steering torque of the steering person in order to apply a steering assist force to the steering mechanism. In the steering device,
The motor includes a first motor and a second motor having a smaller output than the first motor, and the control unit controls the first motor. Means, and second control means for controlling the second motor,
The first control means includes the first system and the second system, and the first control means is configured so that the first motor applies a steering assist force to the steering mechanism in a normal state. The second control means controls the second motor so that the influence of inertia on the first motor by the second motor is compensated, while the second motor controls the second motor. When the occurrence of a failure is detected in one system, the first control means controls the first motor to stop, and the second motor complements the steering mechanism to assist steering. It said second control means so as to impart forces have line control of the second motor is switched,
A rack end determination unit;
The steering mechanism includes a rack and pinion mechanism,
The rack end determination means determines that the rack and pinion mechanism has approached the rack end, and
In normal times, the first control means controls the first motor so that the first motor applies a steering assist force to the steering mechanism, and the second control means The second control means controls the second motor so that the influence of inertia on the first motor by the second motor is compensated, and the rack end detection means approaches the rack end. when it is determined in the electric power steering apparatus characterized said first motor to said switch so as to brake the second row Ukoto the control of the motor.
(2 ) The second control means controls the second motor in a direction opposite to a rotation direction of the first motor and applies a brake to the first motor. ( 1 ) The electric power steering device.
( 3 ) The first control means also functions as the rack end determination means,
When it is determined that the rack and pinion mechanism has approached the rack end, the first control means informs the second control means that the rack and pinion mechanism has approached the rack end, and based on the notification result. The second control means controls the second motor so as to brake the first motor, while the first control means determines that the rack and pinion has moved away from the rack end. If it is determined, the second control means is informed that it has moved away from the rack end, and based on this notification result, the second control means starts from the control for braking the first motor, electric power of the above (1) or (2), characterized in that the influence of the inertia of the said second of said first motor by the motor is switched to control for is compensated Tearing device.
( 4 ) The second motor is mechanically coupled to the rotating shaft of the first motor,
A rotation angle detecting device attached to the first motor for detecting the rotation angle of the first motor, and a rotation angular velocity estimating means for estimating the rotation angular velocity of the second motor; Under normal circumstances, the first control means is based on the rotation angle of the first motor detected by the rotation angle detection device so that the first motor applies a steering assist force to the steering mechanism. The second control means controls the second motor so as to control the first motor and to compensate for the influence of inertia on the first motor by the second motor, On the other hand, when the occurrence of a failure is detected by the rotation angle detection device, the rotation angle velocity estimation means estimates the first rotation angle instead of the rotation angle of the first motor detected by the rotation angle detection device. Any one of an electric power steering described above of the first control means based on the rotational angular velocity estimation value of the motor and performing continuously controlling said first motor (1) to (3) apparatus.
(5) the rotational angular velocity estimation unit, was detected, on the basis of the motor current value and the motor voltage value of the second motor, the (4, characterized in that for estimating the rotational angular velocity of said second motor ) Electric power steering device.
( 6 ) When the occurrence of a failure is detected in the first system excluding the rotation angle detection device, the first control means performs control so that the first motor stops, and the second ( 4 ) or ( 5 ) above, wherein the second control means switches and controls the second motor so that the motor is supplemented to apply a steering assist force to the steering mechanism. Electric power steering device.
( 7 ) When the occurrence of a failure is detected by the rotation angle detection device, the first control unit notifies the second control unit of the occurrence of the failure,
The second control means informs the first control means of the estimated rotational angular velocity of the second motor estimated by the rotational angular velocity estimating means when the occurrence of the failure is notified; and The first control means replaces the rotation angle of the first motor detected by the rotation angle detection device with the rotation angular velocity estimation value of the second motor estimated by the rotation angular velocity estimation seed stage. The electric power steering device according to any one of (4) to (6) , wherein the control of the first motor is continuously performed based on the control.
( 8 ) The electric power steering device according to any one of (1) to ( 7 ), wherein the first motor is a brushless motor, and the second motor is a brush motor.
( 9 ) When the occurrence of a failure is detected in the first system, the first control unit notifies the second control unit of the occurrence of the failure, and the second control unit includes: When the occurrence of the failure is notified, the second motor is switched so as to complement and apply a steering assist force to the steering mechanism, and the second motor is controlled. The electric power steering device according to any one of 1) to ( 3 ).
( 10 ) The electric power steering apparatus according to any one of (1) to ( 9 ), wherein the first control unit and the second control unit are configured by a microcomputer.
( 11 ) The electric power steering apparatus according to any one of (1) to ( 10 ), wherein the second control means is a microcomputer having a lower performance than the first control means.

According to the configuration of (1) above, the motor connected to the steering mechanism and the control means for controlling the motor are respectively provided as two systems as first and second, and in normal times, the first output is provided. Control is performed so that a steering assist force is applied to the steering mechanism by a large system motor and control means, and inertia compensation control of the second system motor is performed by a small system motor and control means with a small second output. When a failure of the motor drive circuit or the like is detected in the first system, for example, the first system motor is stopped and the steering mechanism is steered by the second system motor and control means. Since the control is continued by supplementing so that the auxiliary force is applied, even if a failure occurs in the first system, for example, the first motor drive circuit or the like, the driver feels uneasy and uncomfortable. Without giving, and since the structure can be simplified in the second system, it is possible to realize a small size and low cost.
Further , according to the configuration of ( 1 ), the motor coupled to the steering mechanism including the rack and pinion mechanism and the control means for controlling the motor are divided into two systems as first and second, respectively. In normal operation, the steering mechanism is controlled so that a steering assist force is applied to the steering mechanism by the motor and the control means having a large first output, and the second motor and the control means having a small second output. Inertia compensation control of the motor of the first system is performed, and when the occurrence of a failure such as a motor drive circuit is detected in the first system, the motor of the first system is stopped and the second system is stopped. Since the motor and the control means complement the steering mechanism so that the steering assist force is applied to the control mechanism and continue the control, the first system, for example, the first motor drive circuit or the like fails. Even if that occurred, there is no possible to give the anxiety and discomfort to the steering person. In addition, since the rack-and-pinion mechanism is equipped with rack end determination means for determining that the rack end has approached the rack end, when the rack end determination means determines that the rack end determination means has approached the rack end, Since the second control means controls the second motor so as to brake the first motor, a large impact force is not applied to the steering mechanism. For this reason, a steering feeling of a steering person can be improved, without transmitting an impact to a steering person. Since the output of the second system can be reduced, the structure of the second system can be simplified, and the second system is redundant so that the impact force at the rack end is not applied to the steering mechanism. Since it is a system, it is not necessary to provide a mechanism for that purpose, and the electric power steering apparatus can be realized in a small size and at low cost.
According to the configuration of ( 2 ), when the rack end determination means determines that the rack end is approaching, the second motor is controlled in the direction opposite to the rotation direction of the first motor. It is possible to apply a large impact force to the steering mechanism.
According to the above configuration ( 3 ), the brake is applied to the first motor when the rack end is approached in the normal state, and the brake is released when the brake is moved away from the rack end. Since the inertia compensation control is performed, it is possible to improve the steering feeling of the steering person without giving a large impact force to the steering mechanism, and the first control means also functions as a rack end determination means. Therefore, the electric power steering device can be realized in a small size and at a low cost.
According to the configuration of ( 4 ) above, the motor connected to the steering mechanism and the control means for controlling the motor are provided as two systems, the first and second, respectively. The control of the motor and control means of this system is performed so that the steering assist force is applied to the steering mechanism, and the inertia compensation control of the motor of the second system is performed by the motor and control means of the second system with a small output. When the occurrence of a failure is detected by the rotation angle detection device, instead of the rotation angle of the motor of the first system detected by the rotation angle detection device, the rotation angle velocity estimation means estimates the second system. Since the steering assist force is continuously applied to the steering mechanism by the motor and control means of the first system based on the estimated rotational angular velocity of the motor, the rotational angle detection is performed. Even when a fault occurs in the device, the output is increased steering assist force to a steering mechanism imparted by the first system can have a high degree of control, thereby making it possible to continue steering without uneasy and uncomfortable feeling in the steering person.
According to the configuration of ( 5 ) above, the rotational angular velocity of the second motor can be estimated only by detecting the motor current value flowing through the second motor and the applied motor current value. Therefore, it is not necessary to separately prepare a special device for estimating the manufacturing cost.
According to the configuration of ( 6 ) above, when the occurrence of a failure such as a motor drive circuit is detected in the first system excluding the rotation angle detection device, for example, the first system motor is stopped, Since the second system motor and the control means complement the steering mechanism so that the steering assist force is applied and the control is continued, a failure has occurred in the first system, such as the first motor drive circuit. Even in this case, the driver is not disturbed and uncomfortable, and the structure of the second system can be simplified, so that it can be realized in a small size and at a low cost.
According to the configuration of ( 7 ) above, the failure of the rotation angle detection device is directly notified from the control means of the first system to the control means of the second system, and based on this notification, the first system The control means notifies the rotational speed estimation value of the second system motor to the control means of the first system, and the control means of the first system controls the motor of the first system based on the rotational speed estimation value. Therefore, the steering assist can be continued more quickly.
According to the configuration of ( 8 ) above, since the brush motor is used for the second system motor, the configuration of the second system can be further simplified. When a failure occurs, the control can be continued without making the driver feel uneasy and uncomfortable, but it can be realized at a smaller size and at a lower cost.
According to the configuration of ( 9 ), the first system control means directly notifies the second system control means that a failure has occurred in the first system, for example, the motor drive circuit. Since the control is continued by complementing the motor and the control means of the second system based on this notification, the steering assist can be continued more quickly.
According to the above configuration ( 10 ), by configuring the control means of both systems with a microcomputer, the circuit configuration of the control unit can be simplified, the control unit can be reduced in size and cost, and Steering assist can be realized with high accuracy.
According to the configuration of ( 11 ) above, since the output of the second system can be reduced and the second system can be configured to complement steering assist, the control means of the first system A microcomputer with low performance can be employed. For this reason, further miniaturization and cost reduction can be achieved.

According to the present invention, in an electric power steering apparatus constituted by two drive systems, even if a failure occurs in, for example, a motor drive circuit or the like in the first system, anxiety or discomfort is given to the steering wheel. In other words, the steering assist can be continued without impairing the steering feeling, and an electric power steering apparatus that can be realized at a small size and at a low cost can be provided.
Further, according to the present invention, it is possible to prevent the steering mechanism from being given an impact force at the rack end of the rack and pinion mechanism by using the second system in normal times.
In addition, according to the present invention, when only the rotation angle detection device fails, the steering assist can be continued with the drive system of the first system capable of advanced control.

It is the schematic shown with the vehicle structure relevant to the structure about the structure of the electric power steering apparatus of 1st Embodiment which concerns on this invention. It is the schematic which shows the structure of the reduction gear of the electric power steering apparatus which concerns on 2nd Embodiment of this invention. 1 is a block diagram showing a schematic configuration of an ECU of an electric power steering device according to a first embodiment of the present invention. It is a block diagram which shows the function structure of main MCU of the electric power steering apparatus which concerns on 1st Embodiment of this invention. It is a block diagram which shows the function structure of the sub MCU of the electric power steering apparatus which concerns on 1st Embodiment of this invention. It is a flowchart for demonstrating the operation | movement procedure when the main driver circuit of the electric power steering apparatus which concerns on 1st Embodiment of this invention fails. It is a flowchart for demonstrating the operation | movement procedure at the time of the rack end of the electric power steering apparatus which concerns on 1st Embodiment of this invention. It is a block diagram which shows the function structure of main MCU of the electric power steering apparatus which concerns on 2nd Embodiment of this invention. It is a flowchart for demonstrating the operation | movement procedure when a failure generate | occur | produces in the rotation angle detection apparatus of the electric power steering apparatus which concerns on 2nd Embodiment of this invention. It is a figure which shows schematic structure of the conventional electric power steering apparatus. It is the schematic which shows the structure of the reduction gear of the conventional electric power steering apparatus. It is the schematic which shows schematic structure of ECU of the conventional electric power steering apparatus.

  Hereinafter, preferred embodiments of an electric power steering apparatus according to the present invention will be described with reference to the drawings.

(First embodiment)
First, an electric power steering apparatus according to a first embodiment of the present invention will be described.
FIG. 1 is a schematic diagram showing the configuration of the electric power steering apparatus according to the first embodiment of the present invention together with the vehicle configuration related to the configuration.

As shown in FIG. 1, the electric power steering apparatus according to this embodiment includes a shaft 42 having one end fixed to a steering handle 41 that is steered by a steering wheel, and is connected to the other end of the shaft 42 and is connected via a tie rod 43. In order to reduce the burden of the steering wheel 41 operation by the steering wheel 41, the rack and pinion mechanism 45 for turning the wheel 44, the torque sensor 2 for detecting the steering torque applied to the shaft 42 by the operation of the steering wheel 41, A three-phase brushless motor (hereinafter also simply referred to as a brushless motor) 31 and a brush motor 32 that are mechanically coupled to a steering mechanism, and a rotational torque (steering assist force) generated by the brushless motor 31 and the brush motor 32 are used as a shaft 42. The speed reducer 5 for transmitting to the vehicle and, for example, a wheel 44 for detecting the speed of the vehicle. A control unit that receives power from a vehicle speed sensor (not shown) and a battery power supply (not shown) and controls driving of the brushless motor 31 and the brush motor 32 based on sensor signals from the torque sensor 2 and the vehicle speed sensor. And a control device (ECU) 1.
The sensor signal is not limited to the sensor signals of the torque sensor 2 and the vehicle speed sensor, and various sensor signals can be included as appropriate. However, if at least a sensor signal from the torque sensor 2 is input, the brushless motor 31 and The drive control of the brush motor 32 is possible.

FIG. 2 is a diagram showing a schematic configuration of the speed reducer of the electric power steering apparatus according to the first embodiment of the present invention.
As shown in FIG. 2, the speed reducer 5 includes a worm 51 connected concentrically with the shafts of the brushless motor 31 and the brush motor 32, and a worm wheel 52 connected to the shaft 42 and meshing with the worm 51. The rotation of the brushless motor 31 and the brush motor 32 is decelerated and the torque generated by the brushless motor 31 and the brush motor 32 is transmitted to the shaft 42.
Note that the brushless motor 31 and the brush motor 32 are mechanically coupled with each other along the rotation shaft and are disposed so as to face each other via the worm 51.

FIG. 3 is a block diagram showing a schematic configuration of the ECU in the electric power steering apparatus according to the first embodiment of the present invention.
As shown in FIG. 3, the ECU 1 is mainly composed of a CPU system, and includes a main MCU 11, a sub MCU 12, a main driver circuit 13, a sub driver circuit 14, a motor main drive circuit 15, and a motor sub drive circuit 16. And a main current detection circuit 17, a sub current detection circuit 18, and a motor angle detector 19, and is constituted by two drive systems, a main system and a sub system.

  A steering torque signal detected by the torque sensor 2 and a vehicle speed signal detected by the vehicle speed sensor are input to the main MCU 11 and the sub MCU 12, respectively, and a brushless motor is input to the motor main drive circuit 15 and the motor sub drive circuit 16, respectively. 31 and the brush motor 32 are connected as an electrical load. And the battery power supply 21 is connected via power supply relays S11 and S21. Further, the brushless motor 31 is provided with a rotation angle sensor 20 composed of a resolver or the like for detecting the motor rotation angle of the brushless motor 31, and the motor rotation angle signal detected by the rotation angle sensor 20 is detected as a motor angle. It is sent to vessel 19. That is, the motor angle detector 19 and the rotation angle sensor 20 constitute a rotation angle detection device for detecting the rotation angle of the brushless motor 31.

  The main MCU 11 is a computer system composed of a microcomputer, a RAM, a ROM, and the like. A steering torque signal detected by the torque sensor 2 and a vehicle speed sensor are detected by executing a program stored in the ROM. For controlling the brushless motor 31 so that the brushless motor 31 can generate an appropriate steering assist force, for example, under normal conditions, based on the vehicle speed signal and the motor rotation angle signal sent from the motor angle detector 19. A current control value is generated, and a PWM (pulse width modulation) signal having a duty ratio determined from the current control value is output to the main driver circuit 13.

Further, the main MCU 11 transmits sensor signals such as a steering torque signal and a vehicle speed signal necessary for assist control in the sub system to the sub MCU 12 via a communication line such as serial communication, and detects the main current. By monitoring the state of the circuit 17, the motor rotation angle signal, and the main driver circuit 13, the occurrence of the failure of the motor main drive circuit 15 is continuously monitored (that is, the failure detection process), and the occurrence of the failure is detected when the failure occurs. The sub MCU 12 is notified. Further, the main MCU 11 determines whether the rack and pinion mechanism 45 has approached or moved away from the rack end, that is, at the rack end, based on the motor rotation angle signal input by the motor angle detector 19. The determination result and the motor rotation angle signal of the brushless motor 31 are combined and transmitted to the sub MCU 12.
In the present embodiment, the occurrence of a failure in the motor main drive circuit 15 is monitored as a failure in the main system. However, the present invention is not limited to this. For example, various failure detection sensors are installed, and the brushless motor 31 and the main current detection are detected. The occurrence of a failure in at least any part of the main system such as the circuit 17 may be detected. At this time, it is desirable to install it around a site where failure is likely to occur empirically.

  The sub MCU 12 is a microcomputer system composed of a microcomputer having lower performance than the main MCU 11, a RAM, a ROM, and the like. By executing a program stored in the ROM, for example, a failure of the motor main drive circuit 15 occurs. Is detected, the current for controlling the brush motor 32 so that the brush motor 32 can generate an appropriate steering assist force based on the steering torque signal and the vehicle speed signal input via the main MCU 11. A control value is generated, and a PWM signal having a duty ratio determined from the current control value is output to the sub driver circuit 14.

  The main driver circuit 13 and the sub driver circuit 14 drive the gates of the FETs constituting the motor main drive circuit 15 and the motor sub drive circuit 16 based on the PWM signals output from the main MCU 11 and the sub MCU 12, respectively. Generate a pulse voltage.

  The motor main drive circuit 15 is an inverter composed of six field effect transistors (hereinafter referred to as FETs) Q11 to Q16 that are bridged in order to flow a drive current to the brushless motor 31, and the FETs Q11 to Q16 are It is turned ON / OFF by the pulse voltage of the PWM signal sent from the main driver circuit 13.

  The motor sub-drive circuit 16 is composed of four FETs Q21 to Q24 that are turned on / off by the pulse voltage of the PWM signal sent from the sub-driver circuit 14 and configured to bridge the drive current to the brush motor 32. ing.

  The main current detection circuit 17 detects a motor current for feedback control of the brushless motor 31.

  The motor relays S12 and S13 are controlled by the main MCU 11, and connect or disconnect the two phases of the motor main drive circuit 15 and the drive coil of the brushless motor 31. The motor relay S22 is controlled by the sub MCU 12, and connects or disconnects one phase of the motor sub drive circuit 16 and the drive coil of the brush motor 32. Furthermore, the power supply relay S11 connects or blocks power supply from the battery power supply 21 to the motor main drive circuit 15.

FIG. 4 is a block diagram showing a functional configuration for performing assist control of the main MCU 11, and shows a control program executed by the main MCU 11 for each block.
As shown in FIG. 4, the function of the main MCU 11 includes a torque system for performing control using a steering torque signal and a vehicle speed signal, a current control system for performing control related to driving of the brushless motor 31, and a brushless And a compensation system for compensating the output torque of the motor 31.

  The torque system includes an assist amount calculation unit 111, a phase compensator 112, and a differentiation controller 113. The current control system includes a subtractor 116, a current controller 117, a duty calculator 118, and a motor. The main drive circuit 15 and the main current detection circuit 17 are included, and the compensation system includes a convergence controller 119, an inertia compensator 120, and a SAT estimation compensator 121.

  As shown in FIG. 3, the steering torque signal detected by the torque sensor 2 is input to the assist amount calculation unit 111, the differential controller 113, and the SAT estimation compensator 121.

The assist amount calculation unit 111 calculates an assist amount to be supplied to the brushless motor 31 based on the steering torque signal and the vehicle speed signal, and outputs the calculation result to the phase compensator 112.
Since the steering torque has a characteristic that becomes maximum when the vehicle is stopped and becomes smaller as the vehicle speed increases, the assist amount calculation unit 111 determines that the characteristic corresponds to the steering torque signal and the brushless motor according to a predetermined vehicle speed sensitivity map table. By changing the relationship between the amount of assistance supplied to the vehicle 31 and the assist amount according to the vehicle speed signal, the steering feeling is improved and the behavior of the vehicle is stabilized.

  The phase compensator 112 removes the peak value at the resonance frequency of the resonance system composed of the inertia element and the spring element included in the steering torque signal, and compensates for the phase shift of the resonance frequency that hinders the response and stability of the control system. Thus, in order to improve the transient characteristics or stabilize the control system, the assist amount is subjected to phase compensation, and the phase compensated assist amount is output to the subtractor 116 and the SAT estimation compensator 121. .

  The differential controller 113 corrects the assist amount according to the fluctuation of the steering torque signal, thereby improving the control responsiveness near the neutral point of the steering handle 41 and realizing smooth and smooth steering. . The output of the differentiation controller 113 is input to the adder 114.

  The motor angular velocity estimation unit 124 estimates the motor angular velocity based on the motor rotation angle signal of the brushless motor 31 detected by the rotation angle sensor 20, and the estimated value of the estimated motor angular velocity is the motor angular acceleration estimation unit 125, The data are input to the convergence controller 119 and the SAT estimation compensator 121, respectively.

  The motor angular acceleration estimation unit 125 estimates the motor angular acceleration by performing, for example, a differentiation process on the input estimated value of the motor angular velocity, and the estimated motor angular acceleration is calculated by the inertia compensator 120 and the SAT estimation compensation. To the device 121.

  The convergence controller 119 corrects the assist amount in a direction that hinders the rotation of the steering handle 41 shown in FIG. 1, and applies a brake to the swinging operation of the steering handle 41 when the estimated value of the motor angular velocity is input. The behavior of the steering handle 41 after steering is stabilized.

  The inertia compensator 120 receives the motor angular acceleration, and calculates an assist amount in accordance with a change in the inertial system applied to the steering handle 41, the rack and pinion mechanism 45, the speed reducer 5 and the like shown in FIG. to correct. Thereby, the fluctuation | variation of the output torque of the brushless motor 31 is suppressed, it becomes difficult to transmit the inertia of a drive mechanism to a steering person, and a steering feeling improves.

  The SAT estimation compensator 121 receives the steering torque signal, the phase compensated assist amount, the motor angular velocity, and the motor angular acceleration, and performs a predetermined calculation to estimate the SAT and determine the assist amount. to correct. Thereby, the return after the steering of the steering handle 41 can be improved.

  The adder 122 adds the output of the inertia compensator 120 and the output of the SAT estimation compensator 121 and outputs the result to the adder 123. The adder 123 adds the outputs of the adder 122 and the convergence controller 119 and outputs the result to the subtractor 114.

  The subtractor 114 adds the phase-compensated assist amount and the output of the differential controller 113, and subtracts the output of the adder 123. The result is composed of a 2-3 phase converter or the like, and a torque command value Is output to the current command value calculation unit 115 that calculates the current command value.

  The subtractor 116 subtracts the output of the main current detection circuit 17 from the current command value calculated by the current command value calculation unit 115 and outputs the result to the current controller 117.

  The current controller 117 calculates a voltage command value based on the output of the subtractor 116 and outputs the calculation result to the duty calculator 118. The duty calculator 118 calculates a duty ratio from this voltage command value. A voltage pulse based on the duty ratio is applied to the motor main drive circuit 15 via the main driver circuit 13, and as a result, a drive current is supplied from the motor main drive circuit 15 to the brushless motor 31. As a result, the brushless motor 31 rotates and a steering assist force is applied to the steering handle 41.

FIG. 5 is a block diagram showing a functional configuration for performing the assist control of the sub MCU 12, and shows a control program executed by the main MCU 11 for each block.
As shown in FIG. 5, the sub MCU 12 performs a control related to driving of the brush motor 32 and a torque system for performing control based on the steering torque signal and the vehicle speed signal input via the main MCU 11. Current control system, a compensation system for compensating the output torque of the brush motor 32, a brake system for braking the brushless motor 31 at the rack end of the brushless motor 31, and an input value when not at the rack end. Although it is set to 0, the change-over switch 212 that switches its input so that it becomes the output value of the brake system at the rack end and the output value of the change-over switch 212 in normal times are detected, but the occurrence of a failure in the motor main drive circuit 15 is detected And a changeover switch 210 for switching the input so that the torque system output value is obtained. That.

  The torque system includes an assist amount calculation unit 211, and the current control system includes a subtractor 216, a current controller 217, a duty calculator 218, a motor sub drive circuit 16, and a sub current detection circuit 18. The compensation system includes an inertia compensator 220, and the brake system includes a brake command value calculation unit 213.

The assist amount calculation unit 211 calculates an assist amount to be supplied to the brush motor 32 based on the steering torque signal and the vehicle speed signal, like the assist amount calculation unit 111 described above.
Since the steering torque has a characteristic that becomes maximum when the vehicle is stopped and becomes smaller as the vehicle speed increases, the assist amount calculation unit 211 determines that the characteristic is a steering torque signal and a brush motor according to a predetermined vehicle speed sensitivity map table. By changing the relationship with the assist amount supplied to the vehicle 32 according to the vehicle speed signal, the steering feeling is improved and the behavior of the vehicle is stabilized.

  The motor angular velocity estimation unit 224 estimates the motor angular velocity based on the motor current detected by the sub-current detection circuit 18 and the motor voltage applied to the brush motor 32, and the estimated value of the estimated motor angular velocity is Input to the motor angular acceleration estimation unit 225.

  The motor angular acceleration estimation unit 225 estimates the motor angular acceleration by performing, for example, a differentiation process on the input estimated value of the motor angular velocity, and outputs the estimated motor angular acceleration to the inertia compensator 220.

The inertia compensator 220 receives the motor angular acceleration output from the motor angular acceleration estimation unit 225, and at the time of assist control, that is, when the input value is selected as the output value of the assist amount calculation unit 211 by the changeover switch 210, The assist amount is corrected in accordance with the variation of the inertial system applied to the drive mechanism such as the steering handle 41, the rack and pinion mechanism 45, and the speed reducer 5 shown in FIG. Thereby, the fluctuation | variation of the output torque of the brush motor 32 is suppressed, it becomes difficult to transmit the inertia of a drive mechanism to a steering person, and a steering feeling improves.
Further, as shown in FIG. 5, when the input value is selected to be 0 by the changeover switches 210 and 212, only the inertia compensation control of the brush motor 32 is performed as a result by the function of the inertia compensator 220. That is, in normal times, the influence of the inertia of the brush motor 32 on the brushless motor 31 is compensated, and the assist control of the brushless motor 31 is not hindered.

  The adder 214 outputs the value output from the changeover switch 210 (that is, the output of the changeover switch in the normal state, the output value of the assist amount calculation unit 211 when the occurrence of the motor main drive circuit 15 is detected) and the inertia compensator 220. And the result is output to the current limiting unit 215 as a torque command value.

  The current limiter 215 receives the torque command value, calculates the current command value based on the torque command value, and protects the brush motor 32 from overpower, so that the calculated current command value is a predetermined value. When the value is exceeded, the value is limited as being excessive, and the result is output to the subtracter 216.

  The subtracter 216 subtracts the output of the sub current detection circuit 18 from the current command value output by the current limiting unit 215 and outputs the result to the current controller 217.

The current controller 217 calculates a voltage command value based on the output of the subtractor 216, and the duty calculator 218 calculates a duty ratio based on this voltage command value. A voltage pulse based on the duty ratio is applied to the motor sub drive circuit 16 via the sub driver circuit 14, and a drive current is supplied from the motor sub drive circuit 16 to the brush motor 32.
As a result, the brush motor 32 is rotationally driven when the failure of the motor main drive circuit 15 occurs, and the assist control is complementarily performed, and the steering assist force is continuously applied to the steering handle 41.

The brake command calculation unit 213 receives a motor rotation angle signal of the brushless motor 31 via the main MCU 11, and the brake motor 32 operates in a direction opposite to the rotation direction of the brushless motor 31 to apply a brake. A command value is generated based on the motor rotation angle signal. For this reason, when the input is selected as the output of the brake command value calculation unit 213 by the changeover switch 212 at the time of the rack end in the normal time, the brake control is performed so that the brush motor 32 brakes the brushless motor 31, The impact force at the rack end is not applied to the steering mechanism.
When generating the brake command value, the magnitude of the brake may be determined based on the inertia of the brushless motor 31 and the motor rotation angular acceleration that can be calculated from the motor rotation angle signal.

Next, the operation of the electric power steering apparatus according to the first embodiment of the present invention configured as described above will be described.
FIG. 6 is a flowchart for explaining an operation procedure of the electric power steering apparatus of the present embodiment.

First, in normal times, the main MCU 11 of the ECU 1 is generated based on a steering torque signal detected by the torque sensor 2, a vehicle speed signal detected by the vehicle speed sensor, a motor rotation angle signal sent from the motor angle detector 19, and the like. The PWM signal is output to the main driver circuit 13. Then, the main MCU 11 drives the brushless motor 31 by the motor main drive circuit 15 via the main driver circuit 13 to perform assist control of the main system, and also monitors the occurrence of a failure in the motor main drive circuit 15 (subroutine) SR10).
At this time, as will be described later, when the sub MCU 12 is not at the rack end, the sub-MCU 12 sets the changeover switches 210 and 212 in FIG. 5 so that the brush motor 32 does not become a mechanical load for the assist control of the brushless motor 31. By operating in software, the input value is set to 0 and only inertia compensation control is executed. On the other hand, at the rack end, the sub MCU operates the changeover switches 210 and 212 in a software manner to input the output of the brake command value calculation unit, and brakes the brushless motor 31 using the brush motor 32.

  Next, in step S101, it is determined whether or not an abnormality of the motor main drive circuit 15 has been detected. If no abnormality is detected, the process returns to the subroutine SR10, and the main MCU 11 continues to perform the assist control of the main system and monitor the occurrence of a failure in the motor main drive circuit 15.

  On the other hand, if an abnormality of the motor main drive circuit 15 is detected in step S101, in the next step S102, the power relay S11 and the motor relays S12 and S13 are turned off, that is, electrically disconnected by the control of the main MCU 11. The operation of the motor main drive circuit 15 is stopped and the connection with the brushless motor 31 is disconnected. As a result, the brushless motor 31 does not rotate, and the brushless motor 31 stops.

  At this time, the occurrence of abnormality in the motor main drive circuit 15 is notified from the main MCU 11 to the sub MCU 12 via a communication line such as serial communication (step S103).

In the subsequent subroutine SR20, the sub MCU 12 switches the changeover switch 210 in FIG. 5 in a software manner to connect the torque-system assist amount calculation unit 211 and the adder 214.
As a result, a PWM signal generated based on the steering torque signal and the vehicle speed signal is output to the sub-driver circuit 14, and the brush motor 32 is driven by the motor sub-drive circuit 16 to perform assist control in a complementary manner. For this reason, even when abnormality of the motor main drive circuit 15 is detected, the assist control can be continuously performed.

Next, the operation of the electric power steering device at the time of a rack end in normal times will be described.
FIG. 7 is a flowchart for explaining an operation procedure at the rack end of the electric power steering apparatus of the present embodiment.

  First, the main MCU 11 of the ECU 1 determines whether or not it is at the rack end based on the motor rotation angle signal input by the motor angle detector 19 (subroutine SR30).

  In step S201, it is determined whether or not it is at the rack end. If it is determined that it is at the rack end, the main MCU 11 controls the motor main drive circuit 15 to supply to the brushless motor 31. Current to be limited (step S202).

  Next, the main MCU 11 notifies the sub MCU 12 that it is at the rack end via the communication line. (Step S203).

  Receiving this notification, the sub MCU 12 executes the subroutine SR40, switches the changeover switch 212 so that its input becomes the output of the brake command value calculation unit 213, and brakes so that the brush motor 32 brakes the brushless motor 31. Take control.

  By the process of step S202 and subroutine SR40, the brushless motor 31 is braked, and the impact force at the time of the rack end is not applied to the steering mechanism, and the steering feeling of the steering can be improved.

  On the other hand, if it is determined in step S201 that the main MCU 11 is not at the rack end, the current supplied to the brushless motor 31 is not limited (step S204). Then, in the next step S205, the sub MCU 12 It is notified through the communication line that it is not at the rack end.

  Receiving this notification, the sub MCU 12 executes the subroutine SR50, releases the brake control of the brush motor 32 by the changeover switch 212, switches the brush motor 32 to the inertia compensation control, and ends the processing at the time of a series of rack ends. .

  As described above, according to the present embodiment, the main MCU determines whether or not it is at the rack end in addition to the control of the brushless motor 31, and in normal times, the main MCU 11 is driven by the motor main drive circuit 15 by the brush main motor 15. The sub-MCU 12 performs inertia compensation control of the brush motor 32 by the motor sub-drive circuit 16 while driving the motor 31. When it is determined that the main MCU is at the rack end, the brake control of the brush motor 32 is performed. I do. When the occurrence of an abnormality in the motor main drive circuit 15 is detected, the motor main drive circuit 15 is stopped and the occurrence of the abnormality is notified to the sub MCU 12 so that the brush motor 32 is controlled from the inertia compensation control to the assist control. Switch to. As a result, when the motor main drive circuit 15 breaks down, the assist control can be continued, so that the steering person is not worried or uncomfortable, and the impact force at the end of the rack is not given to the steering mechanism. Therefore, the steering feeling of the steering person can be improved.

  Further, the brush motor 32 driven by the motor auxiliary drive circuit 16 is specialized as a complementary mechanism when a failure of the motor main drive circuit 15 occurs, so that a motor having a smaller output than the brushless motor 31 is used. Therefore, the electric power steering apparatus can be reduced in size and cost. Further, by using a motor with a small output, the configuration of the sub system such as the motor sub-drive circuit 16 can be simplified, a switching element with a small current can be used, and the ECU can be reduced in size and cost. Can be achieved.

(Second Embodiment)
Next, an electric power steering apparatus according to a second embodiment of the present invention will be described. The same parts as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.
In the case of this embodiment, the main MCU 11 monitors the waveform of the motor rotation angle signal output from the motor angle detector 19 as described in Japanese Patent Application Laid-Open No. 2007-118823. While monitoring the occurrence of a failure in the motor angle detector 19 or the rotation angle sensor 20 which is a rotation angle detector, the motor main drive is monitored by monitoring the states of the main current detection circuit 17, the motor rotation angle signal, and the main driver circuit 13. It also has a function of continuously monitoring the occurrence of a failure in the circuit 15 (that is, failure detection processing) and notifying the occurrence of the failure to the sub MCU 12 when the failure occurs. For example, when a failure of the motor angle detector 19 or the rotation angle sensor 20 is detected, the sub MCU 12 transmits the estimated rotation angular velocity value of the brush motor 32 to the main MCU 11 according to the command of the main MCU 11, while the motor When a failure of the main drive circuit 15 is detected, a current control value is generated based on the steering torque signal and the vehicle speed signal input via the main MCU 11, and the duty ratio determined from the current control value is determined. The PWM signal is output to the sub driver circuit 14 so that the brush motor 32 can generate an appropriate steering assist force.

  FIG. 8 is a block diagram showing a functional configuration of a main system for performing assist control of the main MCU 11, and shows a control program executed by the main MCU 11 for each block.

  The motor angular velocity estimation unit 124 of the present embodiment estimates the rotational angular velocity based on the rotational angle signal of the brushless motor 31 detected by the motor angle detector 19 and the rotational angle sensor 20, and estimates the estimated rotational angular velocity. Are input to the motor angular acceleration estimation unit 125, the convergence controller 119, and the SAT estimation compensator 121 via the changeover switch 126.

In the normal state (when the function of the rotation angle sensor 20 is normal), the changeover switch 126 indicates that the rotation angular velocity estimated by the motor angular velocity estimation unit 124 is the motor angular acceleration estimation unit 125 and the convergence controller 119. Are connected to the SAT estimation compensator 121 so as to be input respectively.
On the other hand, when an abnormality such as a failure is detected by the rotation angle sensor 20, the connection state is switched to a sub-system motor angular velocity estimation unit 224, which will be described later, and the rotation angular velocity estimation value of the brush motor 32 is converted into a motor angular acceleration estimation unit. 125, the convergence controller 119, and the SAT estimation compensator 121, respectively.

The motor angular acceleration estimation unit 125 estimates the rotational angular acceleration by performing, for example, a differentiation process on the input estimated value of the rotational angular velocity, and the estimated rotational angular acceleration is calculated by the inertia compensator 120 and the SAT. To the estimation compensator 121.
About another structure, it is the same as that of 1st Embodiment mentioned above.

Next, an operation when a failure occurs in at least one of the motor angle detector 19 and the rotation angle sensor 20 constituting the rotation angle detection device will be described.
FIG. 7 is a flowchart for explaining an operation procedure when a failure occurs in the rotation angle detection device of the electric power steering device according to the present embodiment. The operation when a failure occurs in the motor main drive circuit 15 is the same as the operation described in FIG.

  As shown in FIG. 7, the main MCU 11 monitors the waveform of the motor rotation angle signal output from the motor angle detector 19 as described in, for example, Japanese Patent Application Laid-Open No. 2007-118823, and the like. The occurrence of a failure in the motor angle detector 19 or the rotation angle sensor 20 is monitored (subroutine SR60).

  Next, in step S301, it is determined whether or not an abnormality of the motor angle detector 19 or the rotation angle sensor 20 has been detected. If no abnormality is detected (normally), the changeover switch 126 is connected to the motor angular velocity estimating unit 124 in step S302, and the rotational angular velocity estimated by the motor angular velocity estimating unit 124 is determined as the motor angular acceleration estimating unit 125. Are input to the convergence controller 119 and the SAT estimation compensator 121, respectively. That is, during normal times, the rotational angular velocity estimated by the motor angle estimation unit 124 of the main system is used as it is.

  On the other hand, if an abnormality in the motor angle detector 19 or the rotation angle sensor 20 is detected in step S301, the occurrence of the abnormality from the main MCU 11 to the sub MCU 12 in the next step S303 is a communication line such as serial communication. It is notified via. Accordingly, the sub MCU 12 rotates the brush motor 32 estimated by the motor angular velocity estimation unit 224 based on the motor current value detected by the sub current detection circuit 18 and the motor voltage value applied to the brush motor 32. The estimated angular velocity is transmitted to the main MCU 11.

  Next, in step S304, the main MCU 11 switches the changeover switch 126 in a software manner, and determines the rotational angular velocity estimation value estimated by the motor angular velocity estimation unit 224 as the motor angular acceleration estimation unit 125, the convergence controller 119, and the SAT. It inputs into the estimation compensator 121, respectively. That is, when an abnormality of the motor angle detector 19 or the rotation angle sensor 20 is detected, the motor angular acceleration estimation unit 125, the convergence controller 119, and the SAT estimation compensator 121 are connected to a regular motor of the main system. Instead of the rotational angular velocity estimated by the angular velocity estimating unit 124, the rotational angular velocity estimated value estimated by the sub-system motor angular velocity estimating unit 224 is input.

  Here, the rotational angular velocity estimation value of the motor angular velocity estimation unit 224 of the sub system is calculated for the inertia compensation control of the brush motor 32 in normal times, and when the motors 31 and 32 are geared types, etc. The scale, accuracy, and update cycle differ from the rotational angular velocity output from the motor angular velocity estimation unit 124 used in the brushless motor 31 due to the influence of a speed reducer or the like directly attached.

  Therefore, regarding the alternative use of the rotational angular velocity described above, the scale is arithmetically converted so as to match the rotational angular velocity estimated by the motor angular velocity estimation unit 124. In addition, in the accuracy and update cycle, the gain and responsiveness of the assist control in general are slightly lowered (to make it difficult to cut the steering wheel), thereby depending on the accuracy and update cycle difference between the motor angular velocity estimation unit 224 and the motor angular velocity estimation unit 124. The influence can be reduced, and by performing the processing in this way, the subsequent control can be performed in the same manner as in normal times.

  In step S305, the motor angular acceleration estimation unit 125 estimates the rotational angular acceleration by performing, for example, a differentiation process on the estimated rotational angular velocity value input from the motor angular velocity estimation unit 224. Similarly, the main MCU 11 is based on the steering torque signal detected by the torque sensor 2, the vehicle speed signal detected by the vehicle speed sensor, and the estimated rotational angular velocity value output from the motor angular velocity estimator 224 via the changeover switch 126. The generated PWM signal is output to the main driver circuit 13. Then, the main MCU 11 drives the brushless motor 31 by the motor main drive circuit 15 via the main driver circuit 13 and performs assist control of the main system.

At this time, when the sub MCU 12 is not at the rack end, the changeover switch 210 in FIG. 5 is operated by software so that the brush motor 32 does not become a mechanical load for the assist control of the brushless motor 31. The assist amount calculation unit 211 and the adder 214 are disconnected, and the input value is set to 0 by the changeover switch 212 to execute only the inertia compensation control. On the other hand, at the rack end, the sub MCU 12 performs the aforementioned brake control.
Thereby, even when an abnormality of the rotation angle sensor 20 is detected, the assist control can be continuously performed by the main system by substituting the estimated rotation angular velocity value from the motor angular velocity estimation unit 224.

  As described above, according to the present embodiment, during normal operation, the main MCU 11 drives the brushless motor 31 by the motor main drive circuit 15 to perform assist control, and the sub MCU 12 performs inertia compensation control of the brush motor 32 or Perform brake control. When the occurrence of an abnormality in the motor main drive circuit 15 is detected, the main MCU 11 stops the motor main drive circuit 15 and the brushless motor 31 and notifies the sub MCU 12 of the occurrence of the abnormality in the motor main drive circuit 15. . The sub MCU 12 receives the notification and switches the brush motor 32 from the inertia compensation control to the assist control based on the steering torque signal and the vehicle speed signal. Thereby, assist control can be continued even when a failure of the motor main drive circuit 15 occurs.

  Further, when the occurrence of an abnormality in the motor angle detector 19 or the rotation angle sensor 20 is detected, the sub-system motor angular velocity estimation unit 224 estimates it instead of the rotation angular velocity estimated by the main system motor angular velocity estimation unit 124. Using the estimated rotational angular velocity, the main MCU 11 drives the brushless motor 31 by the motor main drive circuit 15 to perform assist control, and the sub MCU 12 performs inertia compensation control or brake control of the brush motor 32.

  By the way, many of the motor drive elements (for example, the above-mentioned FETs Q11 to Q16) of the electric power steering apparatus are mounted on the metal substrate, and the heat generated by the motor drive element is dissipated. It is attached to a metal case (see, for example, JP-A-2003-11829). Therefore, in general, when a plurality of motor drive circuits are provided, it is necessary to mount all motor drive elements such as FETs on a metal substrate, which increases the size of the metal substrate and the metal case for heat dissipation. Therefore, there was a dislike that the ECU 1 as a whole would be enlarged. However, according to the present embodiment, the brush motor 32 driven by the motor sub-drive circuit 16 is specialized as a complementary mechanism when a failure of the motor main drive circuit 15 occurs, so that the FET Q21 of the motor sub-drive circuit 16 is obtained. -Q24 can be used for low power, and the current consumption of the FETs Q21-Q24 can be reduced. Thereby, according to the present embodiment, heat radiation from the metal substrate to the metal case for heat radiation becomes unnecessary, and mounting on a normal, for example, insulating substrate is possible, thereby avoiding the enlargement of the entire ECU 1. it can.

This is the end of the description of specific embodiments. However, aspects of the present invention are not limited to these embodiments, and modifications, improvements, and the like can be made as appropriate.
For example, in the present embodiment, most of the processing is performed by software, but a part or all of the processing may be realized by hardware such as FPGA (Field Programmable Gate Array).

  In the present embodiment, a three-phase brushless motor has been described as a brushless motor. However, the present invention is not limited to this and can be applied to a two-phase or four-phase or more multiphase motor.

  Further, the present invention is applicable to all electric power steering apparatus control devices having an electric power steering apparatus type (column type, pinion type, rack type) and an electric motor.

1 ECU (control unit)
2 Torque sensor 15 Motor main drive circuit 16 Motor sub drive circuit 11 Main MCU (first control means, rack end determination means)
12 Sub MCU (second control means)
19 Motor angle detector (rotation angle detector)
20 Rotation angle sensor (Rotation angle detector)
31 Brushless motor (first motor)
32 Brush motor (second motor)
126 changeover switch 210 changeover switch 224 motor angular velocity estimation part (rotational angular velocity estimation means)

Claims (11)

In an electric power steering apparatus comprising: a motor mechanically coupled to a steering mechanism; and a control unit that controls the motor based on at least a steering torque of a steering person in order to apply a steering assist force to the steering mechanism. ,
The motor includes a first motor and a second motor having a smaller output than the first motor, and the control unit controls the first motor. Means, and second control means for controlling the second motor,
The first control means includes the first system and the second system, and the first control means is configured so that the first motor applies a steering assist force to the steering mechanism in a normal state. The second control means controls the second motor so that the influence of inertia on the first motor by the second motor is compensated, while the second motor controls the second motor. When the occurrence of a failure is detected in one system, the first control means controls the first motor to stop, and the second motor complements the steering mechanism to assist steering. It said second control means so as to impart forces have line control of the second motor is switched,
A rack end determination unit;
The steering mechanism includes a rack and pinion mechanism,
The rack end determination means determines that the rack and pinion mechanism has approached the rack end, and
In normal times, the first control means controls the first motor so that the first motor applies a steering assist force to the steering mechanism, and the second control means The second control means controls the second motor so that the influence of inertia on the first motor by the second motor is compensated, and the rack end detection means approaches the rack end. when it is determined in the electric power steering apparatus characterized said first motor to said switch so as to brake the second row Ukoto the control of the motor. Said second control means, wherein the first rotational direction of the motor by performing the control of the second motor in the reverse direction, to claim 1, characterized in that brakes the first motor The electric power steering apparatus as described. The first control means also functions as the rack end determination means,
When it is determined that the rack and pinion mechanism has approached the rack end, the first control means informs the second control means that the rack and pinion mechanism has approached the rack end, and based on the notification result. The second control means controls the second motor so as to brake the first motor, while the first control means determines that the rack and pinion has moved away from the rack end. If it is determined, the second control means is informed that it has moved away from the rack end, and based on this notification result, the second control means starts from the control for braking the first motor, electric Pawasute according to claim 1 or 2 effect of inertia to the second of said first motor by the motor and switches to the control for the compensation Alling device. The second motor is mechanically coupled to a rotating shaft of the first motor;
A rotation angle detecting device attached to the first motor for detecting the rotation angle of the first motor, and a rotation angular velocity estimating means for estimating the rotation angular velocity of the second motor; Under normal circumstances, the first control means is based on the rotation angle of the first motor detected by the rotation angle detection device so that the first motor applies a steering assist force to the steering mechanism. The second control means controls the second motor so as to control the first motor and to compensate for the influence of inertia on the first motor by the second motor, On the other hand, when the occurrence of a failure is detected by the rotation angle detection device, the rotation angle velocity estimation means estimates the first rotation angle instead of the rotation angle of the first motor detected by the rotation angle detection device. The electric power steering according to any one of claims 1 to 3 in which said first control means based on the rotational angular velocity estimation value of the motor and performing continuously controlling said first motor apparatus. The rotational angular velocity estimation unit, was detected, on the basis of the motor current value and the motor voltage value of the second motor, according to claim 4, characterized in that estimates the rotation angular speed of said second motor Electric power steering device. When the occurrence of a failure is detected in the first system excluding the rotation angle detection device, the first control means performs control so that the first motor stops, and the second motor The electric power steering apparatus according to claim 4 or 5 , wherein the second control means switches and controls the second motor so as to complement and apply a steering assist force to the steering mechanism. . When the occurrence of a failure is detected by the rotation angle detection device, the first control means informs the second control means of the occurrence of the failure,
The second control means informs the first control means of the estimated rotational angular velocity of the second motor estimated by the rotational angular velocity estimating means when the occurrence of the failure is notified; and The first control means replaces the rotation angle of the first motor detected by the rotation angle detection device with the rotation angular velocity estimation value of the second motor estimated by the rotation angular velocity estimation seed stage. The electric power steering apparatus according to any one of claims 4 to 6 , wherein the control of the first motor is continuously performed based on the control. The electric power steering apparatus according to any one of claims 1 to 7 , wherein the first motor is a brushless motor, and the second motor is a brush motor. The first control means informs the second control means of the occurrence of the failure when the occurrence of the failure is detected in the first system, and the second control means when evolution was broadcast, it claims 1-3, characterized in that to perform the switching by the control of the second motor as the second motor is complementary to impart a steering assist force to the steering mechanism The electric power steering device according to any one of the above. The electric power steering apparatus according to any one of claims 1 to 9 , wherein the first control unit and the second control unit are configured by a microcomputer. Said second control means, from said first control means, the electric power steering apparatus according to any one of claims 1-10, characterized in that the lower microcomputer-performance.

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