JP2013075663A - Electric power-steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly functional electric power-steering device that improves safety by restricting an assist current command value to be smaller than a maximum current, is advantageous to a processing load in a simple configuration and prevents an erroneous determination of a failure of excessive output from being caused.SOLUTION: The electric power-steering device includes: a microcomputer; a CPU for carrying out control arithmetic processing based on a program or the like; a RAM for forming a memory area; an assist current arithmetic processing means for arithmetically processing the assist current command value of a motor; and a respective phase current command values generating means for generating respective phase current command values. The electric power-steering device vectorially controls the motor for providing an assistance based on the respective phase current command values. The electric power-steering device further includes: a failure diagnostic function for diagnosing a failure in regions of a ROM and the RAM at respective predetermined diagnostic cycles; and a failure determination unit for detecting the failure of excessive output from the respective phase current command values generating unit.

Description

  The present invention relates to an electric power steering apparatus that applies a steering assist force by a motor to a vehicle steering system based on at least an assist current command value calculated based on a steering torque, and particularly to an assist current command value. The present invention relates to an electric power steering apparatus having a limit value by a limiter to increase the safety by suppressing the influence of an abnormal output and having an abnormality detection function for excessive output at the calculation part of each phase current command value.

  2. Description of the Related Art Generally, an electric power steering apparatus that applies steering assist force (assist) to a steering apparatus of a vehicle by a rotational force of a motor is provided with a steering shaft by a transmission mechanism such as a gear or a belt via a reduction gear. Alternatively, a steering assist force is applied to the rack shaft. Such a conventional electric power steering apparatus performs feedback control of the motor current in order to accurately generate the steering assist torque. In feedback control, the motor applied voltage is adjusted so that the difference between the current command value and the detected motor current value is small. Generally, the adjustment of the motor applied voltage is a duty ratio of PWM (pulse width modulation) control. It is done by adjusting.

  A general configuration of such an electric power steering apparatus will be described with reference to FIG. A column shaft 2 of the handle 1 is connected to a tie rod 6 of a steered wheel via a reduction gear 3, universal joints 4A and 4B, and a pinion rack mechanism 5. The column shaft 2 is provided with a torque sensor 10 that detects the steering torque of the handle 1, and a motor 20 that assists the steering force of the handle 1 is connected to the column shaft 2 via the reduction gear 3. Electric power is supplied from the battery 14 to the control unit 30 that controls the power steering apparatus, and an ignition key signal is input via the ignition key 11. The control unit 30 calculates the assist current command value (steering assist command value) I of the assist command based on the steering torque T detected by the torque sensor 10 and the vehicle speed V detected by the vehicle speed sensor 12, and is calculated. Based on the assist current command value I, the current supplied to the motor 20 is controlled.

  The control unit 30 is mainly composed of a CPU (or MPU (Micro Processor Unit) or MCU (Micro Controller Unit)), a ROM or RAM memory, etc., and shows general functions executed by programs inside the CPU. 2 is as shown in FIG.

  The function and operation of the control unit 30 will be described with reference to FIG. 2. The steering torque T detected and input by the torque sensor 10 and the vehicle speed V from the vehicle speed sensor 12 (or CAN (Controller Area Network)) are based on the current command. Based on the steering torque T and the vehicle speed V, the assist current command value Iref1 is calculated by the current command value calculation unit 31. The calculated assist current command value Iref1 is phase-compensated by the phase compensation unit 32 for enhancing the stability of the steering system, and the phase-compensated assist current command value Iref2 is input to the addition unit 33. Further, the steering torque T is input to the feedforward differential compensation unit 35 for increasing the response speed, and the differentially compensated steering torque TA is input to the addition unit 33, which adds the assist current command value Iref2 and the steering. The torque TA is added, and the assist current command value Iref3, which is the result of the addition, is added to the subtractor 34 and input.

  The subtracting unit 34 obtains a deviation Iref4 (= Iref3-i) between the assist current command value Iref3 and the motor current i fed back, and the deviation Iref4 is PI-controlled by the PI control unit 36 and further input to the PWM control unit 37. Then, the duty is calculated, and the motor 20 is PWM driven via the inverter 38. The motor current value i of the motor 20 is detected by the motor current detecting means 21 and input to the subtracting unit 34 for feedback.

  Here, in the electric power steering apparatus, an axis (q axis) for controlling the torque, which is a coordinate axis of the rotor magnet of the motor (brushless motor) 20, and an axis (d axis) for controlling the strength of the magnetic field are set independently. Since each axis has a 90-degree phase relationship, vector control is performed to control the current corresponding to each axis using the vector. When vector control is performed on a multiphase motor (for example, a three-phase motor of A, B, and C) 20, an assist current command value Iref3 and a d-axis current command calculated based on the steering torque T and the vehicle speed V as shown in FIG. The value Id_ref is input to each phase current command value generation unit 300, and each phase current command value Irefp1 (Ia_ref, Ib_ref, Ic_ref) generated by each phase current command value generation unit 300 together with the rotation position signal θ of the motor 20 Is input to the subtracting unit 34, and the subtracting unit 34 obtains a deviation Irefp2 (= Iref1-i) between each phase current command value Irefp1 and the motor current i fed back for each phase, and the deviation Irefp2 of each phase is PI control is performed by the PI control unit 36 and further input to the PWM control unit 37 to calculate the duty, and the motor 20 is PWM driven via the inverter 38. The motor current value i of the motor 20 is detected for each phase by the motor current detecting means 21, and is input to the subtracting unit 34 and fed back for each phase.

  Each phase current command value generation unit 300 sets the assist current command value Iref3 as a q-axis current command value, and the q-axis current command value and a separately input d-axis current command value Id_ref according to the rotational position signal θ. Then, each phase current command value Irefp1 (Ia_ref, Ib_ref, Ic_ref) is generated by performing the two-phase / three-phase conversion.

  Next, an example in which the control unit 30 is configured by a microcomputer (MCU) will be described with reference to FIG. In addition to the CPU 40 that is the control arithmetic processing means for performing the feedback control, feedforward control, proportional calculation, and the like described above, the microcomputer temporarily stores the ROM 41 that stores the control program, parameters, and the like, the calculation results from the CPU 40, and the like. RAM 42 is provided as a main storage device. The CPU 40 performs arithmetic processing based on the input signal from the input means 43 and the program and parameters read from the ROM 41, and the arithmetic processing result of the CPU 40 is output to the output means 44 via the RAM 42 of the main storage device. It is comprised so that.

  The ROM 41 is a nonvolatile storage device, and is a read-only memory that stores data that does not need to be rewritten. That is, in the case of the control unit 30 described above, a torque control system (current command value calculation unit 31, phase compensation unit 32, differential compensation unit 35, etc.), current control system (subtraction unit 34, PI control unit 38, PWM control unit). 37, the inverter 38, etc.), the assist control system (motor current detecting means 21, etc.), etc., the control control program for performing the control calculation process, the parameters used for the calculation control program, etc., and the data that does not change are stored in the ROM 41 Has been. However, there is a possibility that an abnormality occurs in the data stored in the ROM 41 or the RAM 42 due to external electrical interference or aging deterioration. Therefore, it is necessary to reliably detect the abnormality in the data in the ROM 41 and the RAM 42.

  In such an electric power steering apparatus, a brushless DC motor is used in addition to a DC motor as the motor 20 as a drive source. The current supplied to such a motor is calculated by the CPU 40 as described above, programs and constants used for the calculation are stored in the ROM 41, and variables and the like are stored in the RAM 42. If an abnormality occurs in the ROM 41 or the RAM 42, the calculation result also becomes abnormal, and an abnormal current flows through the motor 20. Therefore, abnormality diagnosis (including failure diagnosis) of the ROM 41 and the RAM 42 is performed. However, it takes time to diagnose the entire area of the ROM 41 and the RAM 42, and an abnormal current may flow through the motor 20 until the abnormality is detected.

  A method for solving this problem is disclosed in Japanese Patent Laid-Open No. 6-270823 (Patent Document 1). The method of Patent Document 1 stops driving the motor when the steering torque and the motor drive direction do not match, and monitors the CPU assist control calculation from outside the CPU to increase the safety when the calculation is abnormal. Is. However, in the method disclosed in Patent Document 1, there is a case where control is performed such that the steering torque and the motor driving direction do not match even when the assist control is normal, and simply the steering torque does not match the motor driving direction. When driving is stopped at this point, there is a problem that it is erroneously detected as abnormal although it is in a normal state.

  In Japanese Patent Laid-Open No. 2004-133635 (Patent Document 2), an abnormality is detected by adding ROM values in a diagnosis area and comparing the addition result with a specified value. In Patent Document 2, the ROM area is divided in order to shorten the abnormality detection time. However, this is not a division method for reducing the influence at the time of abnormality. May affect behavior.

JP-A-6-270823 JP 2004-133635 A Japanese Patent No. 3336401

  There is ROM / RAM abnormality diagnosis as a safety function of the arithmetic control section of the assist control of the electric power steering device, and when the abnormal current up to the maximum current is assumed, it is necessary to shift the system to a safe state within several tens of ms. (Fault tolerant time), but more time is required for the ROM / RAM abnormality diagnosis (fault detection time). Reducing the fault detection time corresponds to reducing the abnormal diagnosis area or using a high-speed microcomputer, and is actually difficult. Therefore, the present invention aims to increase the fault tolerant time.

  Further, it takes time to perform abnormality diagnosis of the ROM and RAM over the entire area, and there is a possibility that the necessary abnormality detection time may be exceeded, especially for abnormality detection that is excessively assisted. For this reason, in the electric power steering apparatus disclosed in Japanese Patent No. 3336401 (Patent Document 3), the current target value calculated from the steering torque detection value, the control signal, or the value of the dimension of the steering torque from the actual current value. The control system abnormality is detected by comparing the reverse calculation value with the steering torque detection value.

  However, in modern steering control, there are many additional functions such as inertia compensation and compensation functions for improving vehicle characteristics, so that the reverse calculation processing up to the steering torque detection value becomes complicated, increasing the capacity and increasing the processing load. In addition to concerns, there is a problem that misdiagnosis is likely to occur due to the influence of calculation delay and the like because the range of abnormality diagnosis is large.

  The present invention has been made under the circumstances as described above, and an object of the present invention is that the steering torque and the assist current command value are set on the premise that the direction of the steering torque and the assist current command value coincide with each other in normal steering. When the direction is reversed, it is determined that an abnormality has occurred in the assist control calculation, and at that time, the assist current command value is limited to be smaller than the maximum current, thereby improving safety, and for each phase current command value generating means. An object of the present invention is to provide a highly functional electric power steering apparatus that is advantageous in terms of processing load with a simple configuration and that does not cause erroneous determination of excessive output abnormality.

  The present invention relates to a microcomputer, a CPU that performs control calculation processing based on a program, parameters, and the like stored in a ROM in the microcomputer, a RAM that forms a storage area, and a vehicle steering system based on at least a steering torque. Assist current calculation means for calculating an assist current command value for a motor that applies a steering assist force to the motor, and each phase current command value is generated based on the assist current command value, the d-axis current command value, and the rotational position signal of the motor And an electric power steering apparatus that assists by performing vector control of the motor based on each phase current command value. The object of the present invention is to An abnormality diagnosis function for diagnosing a region at each predetermined diagnosis cycle, the assist current command value, and the d-axis current command And it is accomplished by including an abnormality determination unit for detecting an abnormality in the output plethora of the phase current command value generating unit based on the phase current command value.

  Further, the object of the present invention is that the ROM and RAM areas are divided into a plurality of areas and divided according to functions, or the abnormality determination unit should output each phase current command value generation means. Is determined as an abnormality determination threshold 1 for excessive output, and when the output current energy equivalent calculated by each phase current command value exceeds the determination threshold 1, it is determined as abnormal. Alternatively, the abnormality determination unit sets the maximum value of the current energy equivalent amount that should be output by each phase current command value generation means as the determination threshold 2 for the excessive output abnormality, and is calculated with the current command values for each phase. When the output current energy equivalent exceeds the determination threshold 2, it is determined that there is an abnormality, or the current energy equivalent is The sum of the squares of the current command values for each phase, or the abnormality determination unit, the square value of the assist current command value, the square value of the d-axis current command value, the assist current command value, and the d-axis The sum of values obtained by multiplying the absolute values of the multiplication values of the current command values by the respective gains is set as the output excess abnormality determination threshold 3, and the output current energy equivalent calculated by the phase current command values is the determination threshold. When a value exceeding 3 is determined to be abnormal, or a limiter is inserted in the calculation path of the assist current command value, the assist current command value whose upper and lower limit values are limited by the limiter is the current of each phase. This is achieved more effectively by being input to the command value generating means.

  According to the electric power steering apparatus of the present invention, the limiter is provided to limit the output when the steering torque and the motor driving direction do not coincide with each other, so that the motor driving during normal operation is not hindered. In particular, the limiter sets the limit value in response to the magnitude of the steering torque, so that the steering feeling does not feel uncomfortable. Since the output current at the time of abnormality is reduced by the limiter, it is possible to secure a diagnosis time until the abnormality is detected.

  Further, according to the electric power steering apparatus of the present invention, the sum of squares of each phase current command value corresponding to the output current energy of each phase current command value generating means and the input value of each phase current command value generating means. An abnormality determination unit that calculates the maximum value of output energy as the determination threshold and determines that an abnormality occurs when the sum of squares of each phase current command value exceeds the determination threshold is provided. It is advantageous to realize a highly functional electric power steering apparatus that does not cause erroneous determination of excessive output abnormality.

It is a block diagram which shows the structural example of a general electric power steering apparatus. It is a block diagram which shows the function structural example of a general control unit. It is a block diagram which shows the function structural example of the vector control type control unit of a multiphase motor. It is a block diagram which shows the control unit of a general microcomputer structure. It is a block diagram which shows the microcomputer structural example of the control unit of the electric power steering apparatus which concerns on this invention. It is a block diagram which shows the function structural example (1st Embodiment) of the electric power steering apparatus which concerns on this invention. It is a characteristic view which shows an example of the limit value of the limiter used for this invention. It is a schematic diagram for demonstrating SAT. It is a figure which shows the example of the restriction | limiting characteristic of an electric current command value. It is a characteristic view which shows the other example of the limit value of the limiter used for this invention. It is a block diagram which shows the other function structural example (2nd Embodiment) of the electric power steering apparatus which concerns on this invention. It is a block diagram which shows the function structural example (3rd Embodiment) of the electric power steering apparatus which concerns on this invention. It is a commutation pattern figure for demonstrating operation | movement of a rectangular wave control system. It is a characteristic view for demonstrating the operation example of a pseudo | simulation rectangular wave drive control system. It is a characteristic view for demonstrating the operation example of a pseudo | simulation rectangular wave drive control system. It is a characteristic view for demonstrating the operation example of a pseudo | simulation rectangular wave drive control system. It is a block diagram which shows the function structural example (4th Embodiment) of the electric power steering apparatus which concerns on this invention.

  The assist current command value of the current supplied to the motor of the electric power steering device is calculated by a CPU (including MPU and MCU) of the microcomputer, the programs and constants used for the calculation are stored in the ROM, and variables are stored in the RAM. Therefore, if an abnormality occurs in the ROM or RAM, the calculation result also becomes abnormal, and an abnormal current flows through the motor. Therefore, abnormality diagnosis (including failure diagnosis) of the ROM and RAM is performed. The abnormality diagnosis is also performed in the initial diagnosis before the start of the assist control and the constant diagnosis during the execution of the assist control. However, it takes time to diagnose the entire area of the ROM and RAM, and an abnormal current may flow through the motor before the abnormality is detected. Therefore, in the present invention, the limiter for suppressing the influence of the abnormal output. Is inserted into the assist current command value calculation path. Since the influence of the abnormal output is reduced by the limiter, it is possible to secure a diagnosis time until the abnormality is detected. In the present invention, when the reverse assist state = assist current command value is opposite to the steering torque and the steering torque is large, the limit is limited as abnormal, and the limit value of the limiter is when the direction of the steering torque and the assist current command value is opposite. In addition, the characteristic decreases as the absolute value of the steering torque increases. The abnormality diagnosis of the ROM and the RAM and the limit processing when the steering torque is large in the reverse assist state in the limiter are always independently functioning.

  Further, when the phase current command value generating means at the subsequent stage of the limiter is in an abnormal state in which the output is excessive with respect to the input, there is a possibility that excessive assist is provided. However, in the present invention, abnormality detection is performed by comparing the sum of squares, which is the energy amount of the output value, with the energy amount of the input value, so that the configuration is simple, the processing load is small, and the output energy amount is excessive. It is possible to detect over-assist due to becoming in a short time. In addition, the diagnosis function focuses on the part that becomes over-assist based on the abnormality, and is individually diagnosed and has a simple configuration, which is advantageous for processing load and is less likely to cause erroneous determination. .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 5 is a block diagram showing an example of the microcomputer configuration (control device) of the electric power steering apparatus according to the present invention in correspondence with FIG. 4, and the ROM 41 of the present invention has a diagnostic processing program 41A for executing abnormality diagnosis. And the areas of the ROM 41 and the RAM 42 are divided for each function (for example, torque control system, current control system, compensation system). Therefore, it is possible to perform abnormality diagnosis for each function, and it is easy to specify an abnormality occurrence site. Each area of the ROM 41 and the RAM 42 has a respective diagnosis cycle, the ROM 41 performs a sum check, and the RAM 42 performs a known diagnosis method for diagnosing a write value and a read value (for example, Patent Documents 1 and 2, JP 2008-230529 A). An abnormal diagnosis is made using a gazette or the like.

  FIG. 6 is a block diagram showing a functional configuration example of the electric power steering apparatus according to the present invention in correspondence with FIG. 2, and the assist current command value Iref3 output from the adder 33 is expressed by a predetermined arithmetic expression or lookup. A limiter 60 is provided for limiting with a limit value calculated by a table or the like. The limiter 60 is input with a steering torque T, and an upper and lower limit value calculation unit 65 is provided so that the limit value is set in response to the steering torque T. Further, a rotation sensor 22 such as a resolver is attached to the motor 20, and a compensation signal CM is generated based on the rotation position signal θ, the steering torque T, the assist current command value Iref3, etc. from the rotation sensor 22, and the compensation signal A compensation unit 70 for adding the CM to the addition unit 33 is provided.

  The limit value of the limiter 40 has, for example, the characteristics shown in FIG. 7, and assists with the upper limit value + L2 and the lower limit value −L2 in the first quadrant and the third quadrant where the directions of the steering torque T and the assist current command value Iref3 coincide. The current command value Iref3 is limited, and the limit value is set to 0 in the second quadrant and the fourth quadrant where the directions of the steering torque T and the assist current command value Iref3 are different. That is, the assist current command value Iref3 in the same direction as the steering torque T is limited by the maximum value, and the assist current command value Iref3 in the opposite direction is limited by a value smaller than the maximum value. In this example, the limit value is set to 0 when the steering torque T is + T1 or more and when the steering torque T is -T1 or less, but the limit value 0 can be set at any torque value. Limit values + L1 and -L1 at the steering torque T = 0 can also be set to arbitrary magnitudes.

In the present invention, a compensation unit 70 forming a compensation system is provided, and a configuration example thereof will be described. The rotational position signal θ from the rotation sensor 22 is input to the angular velocity calculation unit 71, and the calculated (for example, differentiated) angular velocity ω is input to the angular acceleration calculation unit 72, and the convergence control unit 73 and the SAT (self-aligning). Torque) is input to the estimation unit 75. The angular acceleration ω ^* calculated (for example, differentiated) by the angular acceleration calculation unit 72 is input to the inertia compensation unit 74 and the SAT estimation unit 75. The SAT value SATa estimated by the SAT estimator 75 and the inertia compensation value INa from the inertia compensator 74 are added by the adder 77, and further added by the adder 76 to the convergence control value Ga from the convergence controller 73. The added value of the adding unit 76 is added to the adding unit 33 as a compensation signal CM.

  The convergence control unit 73 is for braking the operation of the steering wheel to improve the yaw convergence of the vehicle, and the inertia compensation unit 74 steers torque that accelerates or decelerates the motor inertia. This eliminates the torque T and makes the steering feel without inertia. The SAT compensation stabilizes the vehicle behavior, and the estimation is performed as follows.

FIG. 8 shows the state of torque generated from the road surface to the steering. When the driver steers the steering wheel 1, the steering torque T is generated, and the motor 20 generates the assist torque Tm according to the steering torque T. . As a result, the wheels are steered and SAT is generated as a reaction force. Further, at that time, torque serving as steering steering resistance is generated by the inertia J and friction (static friction) Fr of the motor 20. Considering the balance of these forces, the following equation of motion is obtained.
(Equation 1)
J ・ ω ^* + Fr ・ sign (ω) + SAT = Tm + T

Here, when the above equation 1 is Laplace transformed with the initial value 0 and SAT is solved, the following equation 2 is obtained.
(Equation 2)
SAT (s) = Tm (s) + T (s) −J ・ ω ^* (s) −Fr ・ sign (ω (s))

As can be seen from the above formula 2, the motor rotation angular velocity ω, the rotation angular acceleration ω ^* , the assist current command value (steering assist force), and the steering torque are obtained in advance by using the inertia J and static friction Fr of the motor 20 as constants. SAT can be estimated from T. For this reason, the steering torque T, the angular velocity ω, the angular acceleration ω ^* , and the assist current command value Iref2 are input to the SAT estimation unit 75, respectively.

  Note that as a compensation element constituting the compensation unit 70, a loss torque compensation unit for performing assist corresponding to the loss torque in the rotation direction of the motor 20, a resonance frequency of a resonance system including an inertia element and a spring element included in the detected torque. A robust stabilization compensator or the like for removing the peak value and compensating for the phase shift of the resonance frequency that hinders the stability and responsiveness of the control system may be further provided.

  The operation of such a control device will be described. The operation is executed according to the arithmetic control program stored in the ROM 41 by the cooperation of the CPU 40, the ROM 41, and the RAM 42.

  The steering torque T from the torque sensor is input to the current command value calculation unit 31 and also input to the differential compensation unit 35, the limiter 60, and the SAT estimation unit 75, and the assist current command value Iref2 from the phase compensation unit 32 is added to the addition unit. 33 and the SAT estimation unit 75. The assist current command value Iref3 obtained by adding the compensation signal CM or the like by the adding unit 33 is input to the limiter 60, and the assist current command value Iref3 is limited according to the relationship with the steering torque T shown in FIG. That is, in the first quadrant in which the directions of the steering torque T and the assist current command value Iref3 coincide (both are positive), the upper limit value + L2 is used, and the third quadrant in which the directions of the steering torque T and the assist current command value Iref3 coincide ( In both cases, the value is limited by the lower limit value −L2, and the assist current command value Irefa limited by the upper limit value + L2 and the lower limit value −L2 is output and input to the adder 34. Further, the limit value is set to 0 in the second quadrant and the fourth quadrant in which the directions of the steering torque T and the assist current command value Iref3 are different. At this time, in the range + T1 to −T1 where the steering torque T is small, the limit value is not 0 but changes linearly (or non-linearly). The compensation unit 70 calculates a motor current value necessary for adjusting the behavior of the vehicle and the steering wheel behavior, and the compensation signal CM may not match the direction of the steering torque T. I try not to put it on. A restriction is applied when the direction of the assist current command value Iref3 does not match in a region where the steering torque T is large. This is because the compensation signal CM from the compensation unit 70 is adjusted so as not to hinder the steering by the driver, and therefore the calculated value inconsistent with the direction of the assist current command value Iref3 can be regarded as abnormal in the region where the steering torque T is large. It is.

  The assist current command value Irefa limited by the limit value of the limiter 60 is output with the characteristics shown in FIG. 9, and the motor 20 is current-controlled as described above based on the assist current command value Irefa whose upper and lower limits are limited. . The rotational position signal θ of the motor 20 is input to the compensation unit 70, and is added to the SAT estimated value SATa from the SAT estimation unit 75, the inertia compensation signal INa from the inertia compensation unit 74, and the convergence control signal Ga from the convergence control unit 73. Based on this, the compensation signal CM is calculated and added to the adder 33.

Similar to the torque control system of the current command value calculation unit 31, the phase compensation unit 32, and the differential compensation unit 35, if an abnormality occurs in the ROM / RAM or the like by the abnormality diagnosis function, for example, a variable ( When an abnormality occurs in a RAM failure or gain (ROM failure), the system may fall into a mode in which the maximum current of the system flows. Therefore, it is necessary to detect the abnormality in a sufficiently short time. The path from the adder 33 to the inverter 38 and the compensation unit 70 are a current control system, and an abnormal output due to an abnormality in the torque control system and compensation system (compensation unit 70) region is caused by a limiter 60 inserted in the current control system. Therefore, the diagnosis time for each of the divided areas of the ROM 41 and the RAM 42 can be set as follows.
(Equation 3)
Current control system diagnosis time ≤ Torque system diagnosis time ≤ Compensation system diagnosis time

Since the diagnosis time can be set to the relationship shown in the above equation 3, the diagnosis time until the vehicle behavior is affected by the limiter 60 inserted in the current control system can be sufficiently secured, and a comfortable steering fee can be ensured. Abnormal output can be reliably limited without interfering with the ring.

  FIG. 10 shows another characteristic example of the limiter 60. When the steering torque T and the assist current command value Iref3 are in the opposite directions, the assist current command value Iref3 is set to the maximum current as shown in the second and fourth quadrants. In the second quadrant of the steering torque T from 0 to + T11, the limit is limited to the maximum value -L11, and in the fourth quadrant of the steering torque T from 0 to -T11, the limit is limited to the maximum value + L11. And it includes portions A2 and B2 where the limit value decreases as the steering torque T increases. The torque control may use the second quadrant and the fourth quadrant even when it is normal, but it is limited to a region where the steering torque T is small, and the limit value is small so as not to limit normal steering as much as possible. The parts A2 and B2 are provided. The limit value is finally limited to 0 when the steering torque T is + T10 or more and −T10 or less. Limiting the state in which the torque control calculation is abnormal to prevent such a situation from occurring when the steering torque T and the assist current command value Iref3 are in opposite directions and the assist current command value Iref3 is large. Can do.

  The limit value may have a characteristic as shown in FIG. 9 depending on the calculation of the torque control. Further, the limit value may be set by the upper / lower limit value calculation unit 65 in response to not only the steering torque T but also the vehicle speed V.

  Further, when the limiter 60 of the present invention is applied to a vector control type electric power steering apparatus as shown in FIG. 3, the configuration shown in FIG. 11 (second embodiment) is obtained. Also in this example, the effect of the limiter 60 is the same as described above.

  Here, in the above-described embodiment, the limiter 60 is inserted in the torque control system, and the torque control calculation part is introduced by introducing the upper and lower limit values corresponding to the steering torque T into the assist current command value Iref3 that is the output of the torque control calculation. The influence of abnormal output is suppressed and diagnosis time is secured. However, the limiter 60 does not function as a matter of course with respect to an abnormality in a control element subsequent to the limiter 60. In particular, in the case of a control mode in which current feedback is performed for each phase with a multiphase brushless motor, the assist current The command value Iref3a is converted to two-phase / three-phase according to the rotational position signal θ of the motor, each phase current command value Irefp1 is calculated, and then feedback control is performed using a deviation from each phase current detection value i of the motor However, when each phase current command value generation unit 300 arranged at the subsequent stage of the limiter 60 is in an abnormal state in which the output is excessive with respect to the input, there is a problem that there is a possibility of excessive assist.

  In addition, in order to respond to the demand for steering response of electric power steering in recent years, many systems adopting field-weakening control are adopted, but when the d-axis current command value Id_ref is input, the assist current command value Iref3a Thus, each phase current command value Irefp1 becomes a value larger by the d-axis current command value Id_ref. Therefore, even if the limiter 60 described above is arranged at the subsequent stage of each phase current command value generation unit 300, the correlation between the steering torque T and each phase current command value Irefp1 does not become uniform, and the upper and lower limits by the limiter 60 Etc. cannot be performed effectively.

  Therefore, in the third embodiment of the present invention, an output is made based on each phase current command value Irefp1 (Ia_ref, Ib_ref, Ic_ref) which is an output of each phase current command value generation unit 300 as each phase current command value generation means. The sum of squares corresponding to the amount of current energy is calculated, and the maximum value of the output current energy amount is determined as a determination threshold Dt from the assist current command value Iref3 and the d-axis current command value Id_ref that are inputs of each phase current command value generation unit 300. An abnormality determination unit 80 is provided that calculates and outputs an abnormality signal AS when the sum of squares of each phase current command value Irefp1 exceeds the determination threshold Dt. Since the abnormality determination unit 80 can perform abnormality diagnosis with a simple configuration of the sum of squares, each phase current command value generation unit 300 becomes in an abnormal state, and an excessive output of output current energy serving as an excessive assist is detected in a short time without erroneous detection. Since it is possible to diagnose a relatively small functional part, it is easy to identify the cause of the abnormal part.

  FIG. 12 shows a configuration example (three-phase brushless motor) of the third embodiment, which will be described in detail below.

  As described above, the assist current command value Iref3a whose upper and lower limits are limited by the limiter 60 is input to each phase current command value generation unit 300 and also to the abnormality determination unit 80, and is determined based on the speed state of the motor 20 and the like. The d-axis current command value Id_ref is also input to each phase current command value generation unit 300 and to the abnormality determination unit 80. Each phase current command value Irefp1 of the three phases generated by each phase current command value generation unit 300 is input to the subtraction unit 34 and input to the abnormality determination unit 80, and the subtraction unit 34 detects the three-phase motor current detection value i. Current feedback control. When the abnormality determination unit 80 determines abnormality, an abnormality signal AS is output, and processing such as assist control prohibition is quickly executed.

  In the third embodiment, the output of each phase current command value generation unit 300 (each phase current command value Irefp1) becomes an excessive output with respect to the input (assist current command value Iref3a) due to an abnormality in the ROM / RAM, etc. This is a technique for detecting a continuing abnormal state, and an abnormality determination unit 80 for that purpose is provided at the subsequent stage of the limiter 60. The abnormality determination unit 80 calculates the maximum amount of output current energy from the sum of squares of each phase current command value Irefp1 as an output, that is, the output current energy amount, and the assist current command value Iref3a and d-axis current command value Id_ref as inputs. Is compared with the judgment threshold Dt calculated as follows, and when the sum of squares of each phase current command value Irefp1 exceeds the judgment threshold Dt, it is judged as abnormal. In other words, continuing the over-assist corresponds to the amount of current energy that is going to flow to the motor being excessive, so the over-assist is continued by comparing the current energy amount with the input and output. Abnormal conditions can be detected.

Since the determination method of the abnormality determination differs in the calculation method of the determination threshold Dt depending on the drive control method of the system, as an example, the rectangular wave drive control system, the sine wave drive control system, and the pseudo rectangular wave drive control disclosed in Japanese Patent No. 3804686 The system will be described in detail below. In the following, in order to simplify the description, the assist current command value Iref3a output from the limiter 60 is simply expressed as “Iref”, and each phase current command value Irefp1 output from each phase current command value generation unit 300 is expressed as This will be described using the A-phase current command value Ia_ref, the B-phase current command value Ib_ref, and the C-phase current command value Ic_ref.
(1) Rectangular wave drive control system During rectangular wave control, the motor is generally driven by commutation control of patterns # 1 to # 6 as shown in FIG. phase current command value is the amount of energy Ia_ref, Ib_ref, 2 sum of squares of Ic_ref becomes 2 × Iref ^2. Therefore, when the calculation is normal, the following equation 4 is always satisfied (equation 4).
Ia_ref ² + Ib_ref ² + Ic_ref ² = 2 × Iref ²

Since the abnormal state desired to be detected by the abnormality detection unit 80 is an excessive output continuation state, when 2 × Iref ² is set as the determination threshold Dt and the following equation 5 is established, it is determined that there is an abnormality.
(Equation 5)
Ia_ref ² + Ib_ref ² + Ic_ref ² > 2 × Iref ² = Dt

(2) Sine-wave drive control system During sine-wave drive control, the assist current command value is generally set to the q-axis current command value Iq_ref, and the d-axis current command value Id_ref and the q-axis current command value Iq_ref are converted into 2/3 phases. Thus, the phase current command values Ia_ref, Ib_ref, and Ic_ref are calculated according to the following Equation 6 with θ as the motor electrical angle.
(Equation 6)
Ia_ref = Iq_ref × sinθ + Id_ref × cosθ
Ib_ref = Iq_ref × sin (θ−120 °) + Id_ref × cos (θ−120 °)
Ic_ref = Iq_ref × sin (θ−240 °) + Id_ref × cos (θ−240 °)
Iq_ref = Iref

From the above formula 6, the square sum of each phase current command value Ia_ref, Ib_ref, Ic_ref which is the current energy amount is expressed by the following formula 7.
(Equation 7)
Ia_ref ² + Ib_ref ² + Ic_ref ² = 3/2 × (Iq_ref ² + Id_ref ² )
= 3/2 × (Iref ² + Id_ref ² )

Based on this equation 7, “3/2 × (Iref ² + Id_ref ² )” is set as a determination threshold Dt, and when the following equation 8 is established, an abnormality is determined.
(Equation 8)
Ia_ref ² + Ib_ref ² + Ic_ref ² > 3/2 × (Iref ² + Id_ref ² ) = Dt


(3) Pseudo rectangular wave drive control system In the pseudo rectangular wave drive control system, each phase current command value Ia_ref, Ib_ref, Ic_ref is calculated according to the following equations 9 and 10. Here, Kt is a torque constant, ed (θ) is a q-axis induced voltage per 1 [rad / s], and eq (θ) is a d-axis induced voltage per 1 [rad / s].
(Equation 9)
Ia_ref = Iq_ref × sinθ + Id_ref × cosθ
Ib_ref = Iq_ref × sin (θ−120 °) + Id_ref × cos (θ−120 °)
Ic_ref = Iq_ref × sin (θ−240 °) + Id_ref × cos (θ−240 °)

上記数９及び数１０より、出力の電流エネルギー量である各相電流指令値Ia_ref、Ib_ref、Ic_refの２乗和は下記数１１となる。

From Equation 9 and Equation 10, the sum of squares of the phase current command values Ia_ref, Ib_ref, and Ic_ref, which are the current energy amounts of the output, is expressed by Equation 11 below.

ここで、判定スレッショルドＤｔとなる数１１の右辺が角度関数となっており、

Here, the right side of Equation 11 that becomes the determination threshold Dt is an angle function,

は図１４のように値が変化し、

Changes its value as shown in FIG.

は図１５のように値が変化し、

Changes its value as shown in FIG.

は図１６のように値が変化する。そのため、判定スレッショルドＤｔの算出が容易ではない。

The value changes as shown in FIG. For this reason, it is not easy to calculate the determination threshold Dt.

  Here, the abnormality determination unit 80 detects that the output is excessive, and the maximum value that can be taken in all angle regions may be set as the determination threshold Dt. For example, when the d-axis current command value Id_ref is 0, the second term and the third term on the right side related to the d-axis current command value Id_ref are 0, and the following formula 15 is satisfied.

また、アシスト電流指令値Irefが０であり、ｄ軸電流指令値Id_refが出力されていた場合、アシスト電流指令値Irefに関連する右辺第１項及び第３項は０となるため、下記数１６が成立する。

When the assist current command value Iref is 0 and the d-axis current command value Id_ref is output, the first term and the third term on the right side related to the assist current command value Iref are 0. Is established.

残りの第3項は両指令値に関連する項であるため、上記のように容易に範囲を設定できない。よって、第３項がとり得る最大値にて判定スレッショルドＤｔを定義する。第３項がとり得る値の範囲は

Since the remaining third term is a term related to both command values, the range cannot be easily set as described above. Therefore, the determination threshold Dt is defined by the maximum value that the third term can take. The range of values that the third term can take is

が０を中心とした角度周期関数となることに注目すると、下記数１７のようになる。

Note that is an angular periodic function centered at 0, the following equation 17 is obtained.

これより、出力の電流エネルギー量である各相電流指令値Ia_ref、Ib_ref、Ic_refの２乗和に対し、制御系が正常である場合は必ず下記数１８が成立する。

As a result, when the control system is normal with respect to the square sum of the phase current command values Ia_ref, Ib_ref, and Ic_ref, which are current energy amounts of the output, the following equation 18 is always satisfied.

よって、下記数１９が成立した場合に異常と判定する。
（数１９）
Ia_ref^２＋Ib_ref^２＋Ic_ref^２> Gain(Iref)×Iref^２＋Gain(Id)×Id_ref^２
＋Gain(Iref_Id)×|Iref×Id_ref|＝Ｄｔ
ただし、Gain(Iref)、Gain(Id)及びGain(Iref_Id)は下記数２０である。

Therefore, it is determined that there is an abnormality when the following equation 19 is satisfied.
(Equation 19)
Ia_ref ² + Ib_ref ² + Ic_ref ² > Gain (Iref) × Iref ² + Gain (Id) × Id_ref ²
+ Gain (Iref_Id) × | Iref × Id_ref | = Dt
However, Gain (Iref), Gain (Id), and Gain (Iref_Id) are the following Expression 20.

なお、スケーリング誤差による誤判定を回避するため、判定スレッショルドＤｔに所定値を加算若しくは乗算しても良い。

In order to avoid erroneous determination due to a scaling error, a predetermined value may be added to or multiplied by the determination threshold Dt.

  In addition, the abnormality determination unit 80 of the present invention is not only arranged at the subsequent stage of the limiter 60, but also between the input and output of each phase current command value generation unit 300 of the vector control type control unit without the limiter 60 as shown in FIG. Even if they are arranged, it is possible to detect an excessive output abnormality.

  In the above description, the case of an ABC-phase three-phase motor has been described.

1 Handle 2 Column shaft 3 Reduction gear 10 Torque sensor 11 Ignition key 20 Motor 21 Motor current detection means 22 Rotation sensor 30 Control unit 31 Current command value calculation unit 32 Phase compensation unit 35 Differential compensation unit 36 PI control unit 37 PWM control unit 38 Inverter 40 CPU
41 ROM
41A Diagnosis processing program 42 RAM
60 Limiter 65 Upper / Lower Value Calculation Unit 70 Compensation Unit 71 Angular Velocity Calculation Unit 72 Angular Acceleration Calculation Unit 73 Convergence Control Unit 74 Inertia Compensation Unit 75 SAT Estimation Unit 80 Abnormality Determination Unit 300 Each Phase Current Command Value Generation Unit

Claims (7)

A microcomputer, a CPU that performs control calculation processing based on a program, parameters, and the like stored in a ROM in the microcomputer, a RAM that forms a storage area, and a steering assist force applied to the vehicle steering system based on at least steering torque Assist current calculation means for calculating the assist current command value of the motor for applying the motor, and each phase current for generating each phase current command value based on the assist current command value, the d-axis current command value, and the rotational position signal of the motor In an electric power steering device comprising command value generating means and assisting by performing vector control of the motor based on each phase current command value,
An abnormality diagnosis function for diagnosing the ROM and RAM areas at each predetermined diagnosis cycle;
An abnormality determination unit that detects an excessive output abnormality of each phase current command value generation unit based on the assist current command value, the d-axis current command value, and each phase current command value;
An electric power steering apparatus comprising: The electric power steering apparatus according to claim 1, wherein the ROM and RAM areas are divided into a plurality of areas and functions. The abnormality determination unit sets the current energy equivalent amount that should be output by each phase current command value generation means as the excess output abnormality determination threshold 1, and corresponds to the output current energy calculated by each phase current command value. The electric power steering apparatus according to claim 1 or 2, wherein an abnormality is determined when the amount exceeds the determination threshold 1. The abnormality determination unit uses the maximum value of the current energy equivalent amount that should be output by each phase current command value generating means as the excessive output abnormality determination threshold 2, and the output calculated by each phase current command value The electric power steering apparatus according to claim 1 or 2, wherein an abnormality is determined when a current energy equivalent exceeds the determination threshold (2). The electric power steering apparatus according to claim 3 or 4, wherein the current energy equivalent amount is a sum of squares of the respective phase current command values. The abnormality determining unit multiplies the absolute value of the square value of the assist current command value, the square value of the d-axis current command value, the multiplication value of the assist current command value and the d-axis current command value by a gain, respectively. The sum of the values is used as the output excess abnormality determination threshold 3, and when the output current energy equivalent calculated by each phase current command value exceeds the determination threshold 3, an abnormality is determined. The electric power steering device described in 1. 7. A limiter is inserted in the calculation path of the assist current command value, and an assist current command value whose upper and lower limit values are limited by the limiter is input to each phase current command value generation means. The electric power steering device according to any one of the above.

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