JP2010195222A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device in which when an abnormality occurs in a storage part that stores a program for performing a steering assistance control, a control mode can be selected based on the area in which the abnormality occurs. <P>SOLUTION: An electronic control device of the electric power steering device includes a storage part that stores a program and data necessary for the execution of a steering assistance control operation for controlling the electric motor, a storage abnormality detection part that detects an abnormality of the storage part, and an abnormal time control part that performs, when the storage abnormality detection part detects an abnormality, an abnormality control operation based on the area in which the abnormality is detected. The storage part includes a program storage area for storing the program and a data storage area for storing the data. When the storage abnormality detection part detects an abnormality, the abnormal time control part selects the mode of abnormality control based on whether the abnormality is detected in the program storage area or the data storage area. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus that controls an electric motor that applies a steering assist force to a steering system, and in particular, detects an abnormality in a storage unit that stores a steering assist control program, and performs control according to the detected abnormality. The present invention relates to an electric power steering apparatus in which a mode is selected.

  In this type of electric power steering device, the ROM area is composed of a plurality of cells composed of a predetermined number of byte data, and includes a normal control period for controlling the controlled object and a diagnostic period for performing fault diagnosis of the control computer. The control means that performs control in the machine cycle and the addition of data that is partly placed in a plurality of cells for each diagnosis period, and the current diagnosis is performed on the addition value of the data of some cells obtained in the previous diagnosis period Computation means for comparing the sum of the added values with the specified value when the data of all the cells in the ROM area are obtained by adding the data of some other cells to the period of use, and There is known a control computer that performs failure detection based on a comparison between a sum of addition values by means and a prescribed value (see, for example, Patent Document 1).

  In addition, the storage area of the microcomputer RAM provided in the engine control ECU of the automobile is divided into three blocks, a high block, a medium block, and a low block, and the data to be stored in the RAM is also an abnormality of the automobile. It is classified into three types of groups according to the degree of impact on safety, and the blocks are stored in the high block, medium block, and low block in order from the group with the largest impact level. , A memory diagnosis device and a control device that perform fail-safe processing when a diagnosis is detected at a higher frequency (that is, high> medium> low) in a block in which the data having a greater influence is stored Is known (see, for example, Patent Document 2).

2004-133635 gazette No. 2003-323353

  As described above, in the conventional examples described in Patent Documents 1 and 2, when a memory failure is detected in the initial memory diagnosis performed before the start of the assist control from the start of the microcomputer, or during the assist control. When a memory failure is detected by the continuous memory diagnosis that is performed, as a fail-safe process, the assist control is stopped, the power to the motor is cut off, or the microcomputer is reset, and the system reaches a serious failure mode. It is preventing.

  However, with the expansion of the adoption of electric power steering devices for medium-sized and large vehicles, a large steering force is required when steering the steering mechanism, and assist control is stopped when the ROM fails or the motor is switched to the motor. If the generation of steering assist force is stopped by shutting off the power to the vehicle or resetting the microcomputer, the driver will be overburdened, and there is an unsolved problem that it is not necessarily a good measure. is there.

  Accordingly, the present invention has been made paying attention to the unsolved problems of the above-described conventional example, and when an abnormality occurs in a storage unit such as a program for performing steering assist control, a control mode according to the abnormality occurrence region It is an object of the present invention to provide an electric power steering device capable of selecting the above.

  In order to achieve the above object, an electric power steering apparatus according to claim 1 of the present invention is an electric power steering apparatus including an electronic control unit that controls an electric motor that generates a steering assist force with respect to a steering mechanism. The electronic control device includes a storage unit that stores a program and data necessary for executing a steering assist control process for controlling the electric motor, and a storage abnormality detection unit that detects abnormality of the storage unit. An abnormality control unit that performs an abnormality control process according to an abnormality detection area when an abnormality is detected by the storage abnormality detection unit, and the storage unit stores a program storage area for storing the program and the data. A data storage area for storing, and the abnormality control unit is an abnormality in the program storage area when an abnormality is detected by the storage abnormality detection means It is characterized by selecting the abnormality control modes depending on whether the abnormality of the data storage area.

  With such a configuration, by configuring the storage unit that stores the program and data necessary for the steering assist control process in the storage unit with the program storage area that stores the program and the data storage area that stores the data, It is possible to select the abnormality control mode according to the degree of influence of the abnormality of the storage unit on the steering assist control, determine whether to stop and continue the steering assist control, and increase the chance of continuing the steering assist control process. it can.

  According to a second aspect of the present invention, there is provided the electric power steering apparatus according to the second aspect, wherein the abnormality control unit stops the steering assist control by the electronic control unit when the abnormality of the storage unit is the program area. And when the data storage area is abnormal, a correction process for reducing and correcting the steering assist command value in the steering assist control process is performed.

  With such a configuration, when the abnormality of the main storage unit is in the program storage area, the steering assist control process is stopped, and when it is in the data storage area, the steering assist command value in the steering assist control process is decreased and corrected. Steering assist control can be continued.

  According to the present invention, the storage unit that stores the program and data necessary for the steering assist control process is configured by the program storage area that stores the program and the data storage area that stores the data. Is the program storage area or the data storage area, and by selecting the abnormal control mode according to the abnormal storage area, the opportunity to continue the steering assist control process can be increased. An effect is obtained.

It is a schematic block diagram which shows the structure of the electric power steering apparatus by this invention. It is a block diagram which shows the specific structure of a controller. It is explanatory drawing which shows the structure of the storage area of ROM. It is a flowchart which shows a steering assistance control process. It is a flowchart which shows an example of a memory | storage abnormality detection process sequence.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an electric power steering apparatus showing an embodiment of the present invention.
In FIG. 1, reference numeral 1 denotes a steering wheel. A steering force applied to the steering wheel 1 from a driver is transmitted to a steering shaft 2 having an input shaft 2a and an output shaft 2b. The steering shaft 2 has one end of the input shaft 2 a connected to the steering wheel 1 and the other end connected to one end of the output shaft 2 b via the torque sensor 3.

  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 to steer a steered wheel (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. Has been converted.

A reduction gear 10 that transmits auxiliary steering force to the output shaft 2b is connected to the output shaft 2b of the steering shaft 2, and an output shaft of an electric motor 12 that generates auxiliary steering force is connected to the reduction gear 10. ing.
The torque sensor 3 detects the steering torque applied to the steering wheel 1 and transmitted to the input shaft 2a. For example, the torsion bar (not shown) in which the steering torque is interposed between the input shaft 2a and the output shaft 2b is used. The torsional angular displacement is converted into an angular displacement and detected by, for example, a non-contact magnetic sensor.

  The detected torque value T output from the torque sensor 3 is input to the controller 13. In addition to the torque detection value T, the controller 13 also receives a vehicle speed detection value V detected by the vehicle speed sensor 14 and a motor current detection value Imd flowing through the electric motor 12, and the inputted torque detection value T and vehicle speed detection value V are inputted. A steering assist command value Iref that generates the corresponding steering assist force in the electric motor 12 is calculated, and the drive current supplied to the electric motor 12 is feedback-controlled based on the calculated steering assist command value Iref and the motor current detection value Imd.

  As shown in FIG. 2, the controller 13 controls the drive current supplied to the electric motor 12 based on the microcomputer 15 that executes control processing of the electric motor 12 and the motor drive current Imt output from the microcomputer 15. A motor drive circuit 17 and a motor current detection circuit 18 that detects a motor current that is an output current of the electric motor 12 are provided.

A torque detection value T detected by the torque sensor 3 and a motor current detection value Imd detected by the motor current detection circuit 18 are converted into digital values by the A / D converters 21 and 22 and input to the microcomputer 15. .
The microcomputer 15 includes an input interface circuit 15a to which the torque detection value T, the vehicle speed detection value V, and the motor current detection value Imd are input, and the electric motor based on the torque detection value T, the vehicle speed detection value V, and the motor current detection value Imd. 12 stores the central processing unit 15b that executes steering assist control processing for controlling steering 12 to generate steering assisting force according to the steering torque, and programs and data necessary for the steering assist control processing that is executed by the central processing unit 15b. ROM 15c as a storage unit, RAM 15d for storing detection data such as torque detection value T and motor current detection value Imd, data required in the process of steering control processing executed by central processing unit 15b, and processing results, and output Interface circuit 15e.

  As shown in FIG. 3, the ROM 15c includes programs such as a steering control processing program serving as a main program for causing the central processing unit 15b to execute steering control processing, and a storage abnormality detection program for detecting abnormality in the storage area of the ROM 15c. A program storage area 21 for storing data and a data storage area 22 for storing data that does not change parameters necessary for the steering assist control process are provided.

  The program storage area 21 is divided into a plurality of blocks BP1 to BPn composed of predetermined bits, and a control program divided for each control system is stored in each of the blocks BP1 to BPm. For example, an arithmetic processing program for the current command value arithmetic system is stored in the block BP1, a current feedback processing program is stored in the block BP2, a torque control arithmetic program is stored in the block BP3, and a memory abnormality detection program is stored in the block BP4. ing.

In addition, the data storage area 22 is also divided into a plurality of blocks BD1 to BDn composed of predetermined bits, and data divided for each control system is stored in each block BD1 to BDn. For example, data such as current control parameters are stored in the block BD1, and data such as current feedback parameters are stored in the block BD2.
Each block BP1 to BPm in the program storage area 21 and each block BD1 to BDn in the data storage area 22 are set to a predetermined bit position, for example, a set sum value SUMPs1 for checksum as an error identification code at the last bit position of the block. SUMPsm and SUMDs1 to SUMDsn are stored.

The central processing unit 15b performs a steering assist control process by executing a steering assist control program stored in the ROM, and performs a memory abnormality detection process by executing a memory abnormality detection program.
In the steering assist control process, as shown in FIG. 4, first, in step S1, it is determined whether or not a memory abnormality flag Fm set in a memory abnormality detection process described later is “1”, and Fm = “ When it is “1”, the process proceeds to step S2, the motor current command value Imt is set to “0”, the motor current command value Imt is output to the motor drive circuit 17, and then the process returns to step S1.

  If the determination result in step S1 is that the memory abnormality flag Fm is other than “1”, the process proceeds to step S3 to determine whether or not the memory abnormality flag Fm is “0”, and Fm = “0”. When it is, the process proceeds to step S4, the gain K is set to “1”, and then the process proceeds to step S6. When Fm = “2”, the process proceeds to step S5 and the gain K is set to 0.5. Then, the process proceeds to step S6.

  In step S6, the torque detection value T detected by the torque sensor 3 is read, and then the process proceeds to step S7, where the vehicle speed detection value V is read, and then, the process proceeds to step S8, based on the torque detection value T and the vehicle speed detection value V. The steering assist current command value Iref is calculated with reference to a steering assist command value calculation map (not shown), and the process proceeds to step S9.

  In this step S9, a corrected auxiliary current command value Iref ′ is calculated by multiplying the calculated steering auxiliary current command value Iref by the correction gain K, and then the process proceeds to step S10, where the motor current detected by the motor current detection circuit 18 is detected. The detected value Imd is read, then the process proceeds to step S11, the motor current detected value Imd is subtracted from the corrected steering assist current command value Iref ′ to calculate the current deviation ΔI, and then the process proceeds to step S12.

  In this step S12, PI control processing is performed based on the calculated current deviation ΔI to calculate the motor drive current Imt, and then the process proceeds to step S13 to output the motor drive current Imt to the motor drive circuit 17. The process returns to step S1.

  Further, the memory abnormality detection process is executed as a timer interrupt process for every predetermined time (for example, 10 msec) with respect to the main program. As shown in FIG. 5, first, the process proceeds to step S21, and the program storage area 21 of the ROM 15c The variable i for the blocks BP1 to BPm is set to 1, then the process proceeds to step S22 to calculate the addition value SUMPi of the block BPi, and then the process proceeds to step S23, where the calculated addition value SUMPi is stored in the program storage area. It is determined whether or not it matches the set addition value SUMPsi stored in the block BPi of 21.

  When the determination result indicates that the addition value SUMPi matches the stored set addition value SUMPsi, the storage content of the block BPi is determined to be normal, and the process proceeds to step S24, where all the blocks BP1 to BPm are stored. It is determined whether or not the variable i has reached m as to whether or not the abnormality detection has ended. If i <m, the process proceeds to step S25, the variable i is incremented, and then the process proceeds to step S22. When i = m, the process proceeds to step S27 described later.

  If the result of determination in step S23 is that the calculated addition value SUMPi does not coincide with the set addition value SUMPsi, it is determined that the stored content is abnormal, the process proceeds to step S26, and the memory abnormality flag Fm is stored in the program. The area 21 is set to “1” indicating that it is abnormal, and the timer interrupt process is terminated.

  In step S27, the variable j for the blocks BD1 to BDn in the data storage area 22 of the ROM 15c is set to 1, and then the process proceeds to step S28 to calculate the added value SUMDj of the block BDj, and then to step S29. Then, it is determined whether or not the calculated addition value SUMDj matches the set addition value SUMDsj stored in the block BDj of the data storage area 22.

  If the determination result is that the added value SUMDj matches the stored set added value SUMDsj, it is determined that the stored contents of the block BDj are normal, and the process proceeds to step S30, where all the blocks BD1 to BDn are stored. It is determined whether or not the variable j has reached n as to whether or not the abnormality detection has ended. When j <n, the process proceeds to step S31, the variable j is incremented, and then the process proceeds to step S28. When j = n, the process proceeds to step S32, the memory abnormality flag Fm is set to “0” indicating that the ROM 15c is normal, and then the timer interruption process is terminated.

If the result of determination in step S29 is that the calculated addition value SUMDj does not coincide with the set addition value SUMDsj, it is determined that the stored content is abnormal, the process proceeds to step S33, and the memory abnormality flag Fm is stored as data. After the area 22 is set to “2” indicating that it is abnormal, the timer interrupt process is terminated.
Here, the processes in steps S1 to S5 and S9 in FIG. 4 described above correspond to the abnormality control unit, the processes in steps S6 to S13 correspond to the steering assist control unit, and the process in FIG. It corresponds.

Next, the operation of the above embodiment will be described.
Now, in the normal steering state, the memory abnormality detection process of FIG. 5 is executed by the central processing unit 15b of the microcomputer 15 of the controller 13 based on the memory abnormality detection program stored in the program area 21 and the data area 22 of the ROM 15c. The
At this time, a checksum is performed for each of the blocks BP1 to BPm and PD1 to BDn for the program storage area 21 and the data storage area 22 of the ROM 15c, and the addition values SUMP1 to SUMPm and SUMD1 to SUMDn for each block are calculated and calculated. By determining whether or not the added values SUMP1 to SUMPm and SUMD1 to SUMDn match the set added values SUMPs1 to SUMPsm and SUMDs1 to SUMDsn stored in the blocks BP1 to BPm and PD1 to BDn of the ROM 15c, the stored contents It is determined whether or not is abnormal.

Here, when the blocks BP1 to BPm and PD1 to BDn in the program storage area 21 and the data storage area 22 of the ROM 15c are normal, the process proceeds to step S21 in FIG. 5 and the memory abnormality flag Fm is set to “0”. Is done.
Therefore, when the steering assist control process of FIG. 4 is executed by the central processing unit 15b of the microcomputer 15 based on the steering assist control program stored in the ROM 15c and its parameters, the process proceeds to step S4. The gain K is set to “1”.

  Therefore, in the steering assist control process, the torque detection value T and the vehicle speed detection value V are read (steps S6 and S7), and the steering assist current command value is calculated based on the torque detection value T and the vehicle speed detection value V. A steering assist current command value Iref is calculated with reference to the map (step S8).

  Next, the corrected steering assist current command value Iref ′ is calculated. Since K = 1, the corrected steering assist current command value Iref ′ is the same value as the steering assist current command value Iref and no correction is performed. Then, the motor current detection value Imd is read (step S10), the motor current detection value Imd is subtracted from the steering assist current command value Iref to calculate the current deviation ΔI (step S11), and the calculated current deviation ΔI is used as the PI current. A control process is performed to calculate the motor current Imt (step S12), and the calculated motor current Imt is output to the motor drive circuit 17, so that the electric motor 12 generates a steering assist force according to the torque detection value T. To drive control.

Then, a steering assist force corresponding to the steering torque generated by the electric motor 12 is transmitted to the output shaft 2 b via the reduction gear 10.
At this time, in a so-called stationary state in which the steering wheel 1 is steered while the vehicle is stopped, a large steering with a small torque detection value T is caused by a large gradient of a characteristic line of a steering assist current command value calculation map (not shown). Since the auxiliary current command value Iref is calculated, a large steering assist force can be generated by the electric motor 12 to perform light steering.

On the other hand, when the vehicle starts and reaches a predetermined vehicle speed or more, the gradient of the characteristic line of the steering assist command value calculation map becomes small, so that a small steering assist command value Iref is calculated even with a large torque detection value T. The steering assist force generated at 12 is reduced, and the steering of the steering wheel 1 can be suppressed from becoming too light and optimal steering can be performed.
However, if an abnormality is detected in any one or more blocks in the program storage area 21 of the ROM 15c in the memory abnormality detection process of FIG. 5, the process proceeds to step S16 in FIG. 5 and the memory abnormality flag Fm is set. Set to “1”.

  For this reason, when the steering assist control process of FIG. 4 is executed, the process proceeds from step S1 to step S2, and the motor current command value Imt = 0 is output to the motor drive circuit 17, whereby the motor drive circuit 17 The output of the motor current Im is stopped, and the drive of the electric motor 12 is immediately stopped. That is, since an abnormality in the program area 21 of the ROM 15c is likely to cause a serious abnormality, the driving of the electric motor 12 is stopped and the steering assist control process is ended.

On the other hand, when an abnormality is detected in one or more blocks in the data storage fishing season 22 of the ROM 15c in the memory abnormality detection processing field of FIG. 5, the process proceeds to step S23 in FIG. 2 ".
Therefore, when the steering assist control process of FIG. 4 is executed, the process proceeds from step S3 to step S5, the correction gain K is set to 0.5, and the steering assist current calculated in step S8. Since the corrected steering assist current command value Iref ′ is calculated by multiplying the command value Iref by the correction gain K = 0.5, the corrected steering assist current command value Iref ′ is limited to half the steering assist current command value Iref. However, the steering assist control process is continued.

  As described above, when a memory abnormality occurs in the data storage area 22, it is determined that the abnormality is minor, and the steering assist control process is continued with the corrected steering assist command value Iref ′ in which the steering assist command value Iref is limited. As a result, the steering assist force can be generated by the electric motor 12, and the steering assist force is about half that of the normal state. However, the steering assist force itself can be generated, and thus lighter by this amount. Steering can be continued.

  As described above, in the above embodiment, the ROM 15c as the storage unit is divided into the program storage area 21 and the data storage area 22, and the memory abnormality is detected for each of them. If it occurs, the steering assist control process is stopped. If an abnormality occurs in the data storage area 22, the steering assist control process can be continued with the steering assist force suppressed. For this reason, the chance of continuing the steering assist control can be increased as compared with the case where the steering assist control process is all stopped when the memory abnormality is detected as in the case of detecting the abnormality of the entire ROM 15c.

In the above embodiment, the case where the program storage area 21 and the data storage area 22 of the ROM 15c are each divided into a plurality of blocks has been described. However, the present invention is not limited to this, and any one of the storage areas May be composed of one block.
In the above-described embodiment, a case has been described in which correction is performed to halve the steering assist current command value Iref when the data storage area 22 has a memory abnormality. However, the present invention is not limited to this. The value of K can be set to an arbitrary value according to the specifications of the vehicle.

  In the above-described embodiment, the case where the motor current command value Imt is set to “0” when the program storage area 21 becomes abnormal in the memory has been described. The power supplied to the circuit 17 may be cut off by, for example, a relay, the motor current Im output from the motor drive circuit 17 to the electric motor 12 may be cut off by, for example, a relay, and the steering assist control process itself is stopped. You may make it do.

In the above embodiment, the case where the memory abnormality flag Fm is immediately set when a memory abnormality is detected has been described. However, the present invention is not limited to this. The abnormality flag Fm may be set.
Further, in the above-described embodiment, the case where the present invention is applied to a column assist type electric power steering apparatus has been described. However, the present invention is not limited to this, and the present invention is not limited to a pinion assist type or rack assist type electric power steering apparatus. The present invention can also be applied.

DESCRIPTION OF SYMBOLS 1 ... Steering wheel, 2 ... Steering shaft, 3 ... Torque sensor, 8 ... Steering gear, 12 ... Electric motor, 13 ... Controller, 14 ... Vehicle speed sensor, 15 ... Microcomputer, 15a ... Input interface circuit, 15b ... Central processing unit 15c ... ROM, 15d ... RAM, 15e ... output interface circuit, 17 ... motor drive circuit, 18 ... motor current detection circuit, 21 ... program storage area, 22 ... data storage area

Claims (2)

An electric power steering device including an electronic control device that controls an electric motor that generates a steering assist force for a steering mechanism,
The electronic control device includes a storage unit that stores a program and data necessary for executing a steering assist control process for controlling the electric motor, a storage abnormality detection unit that detects abnormality of the storage unit, and the storage An abnormality control unit that performs an abnormality control process according to the abnormality detection area when an abnormality is detected by the abnormality detection unit;
The storage unit has a program storage area for storing the program and a data storage area for storing the data,
The abnormality control unit selects an abnormality control mode according to whether the abnormality is in the program storage area or the data storage area when an abnormality is detected by the storage abnormality detection means. Electric power steering device.   The abnormal time control unit performs a control stop process for stopping steering assist control by the electronic control device when the abnormality of the storage unit is in the program area, and the steering assist control process when the abnormality of the data storage area is detected. The electric power steering apparatus according to claim 1, wherein a correction process for decreasing and correcting the steering assist command value is performed.

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