JP2008284889A - Control device of electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device of an electric power steering device capable of reducing an impact and abnormal sound caused by collision with an rack end when sudden turning-increase steering is executed right before the rack end. <P>SOLUTION: The steering angle acceleration α, steering angle θ, angle speed ω, vehicle speed V, steering torque T of a steering device is inputted in a control device. steering angle acceleration gain g4, and multiplies steering angle gain g1, angle speed gain g2, vehicle speed gain g3 to output gain g5. A determination control part 41 determines whether or not carrying out assist control to the steering torque T on the basis of the steering angle θ, the steering angle gain g1, the angle speed gain g2, the vehicle speed gain g3, the steering angle acceleration gain g4, a lower limit gain gL1 outputted from a steering torque lower limit gain setting part 38 and a determination result DS of a turning-increase/turning-back determination part in addition to the vehicle speed V. Switches 43, 44 are switched to output one of the gain g5, fixed gain "1" and lower limit gain gL1 as a gain G1 and to reduce the steering torque T, thereby reducing an impact and abnormal sound when sudden turning-increase steering is executed near the rack end at low speed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an electric power steering device, and more particularly to a control device for an electric power steering device that reduces an impact when a rack constituting a steering mechanism collides with a rack end.

  An electric power steering device for a vehicle is a device intended to reduce a driver's steering load, and detects a steering torque generated in the steering device, and a current command according to a value of the detected steering torque. The value is calculated, the motor is controlled based on the calculated current command value, and assist torque for assisting the steering torque is generated.

  FIG. 7 is a diagram illustrating an example of the overall configuration of the electric power steering apparatus. A column shaft 102 of the steering wheel 101 is connected to a steering wheel tie rod 106 via a reduction gear 103, universal joints 104A and 104B, and a pinion rack mechanism 105. The column shaft 102 is provided with a torque sensor 110 that detects the steering torque of the steering wheel 101, and a motor 120 that supplies a steering assist force is connected to the column shaft 102 via a reduction gear 103.

  Electric power is supplied from the battery 104 via the ignition key 111 to the control device 130 that controls the electric power steering device. The control device 130 receives the ignition key ON signal, the detected steering torque T, and the vehicle speed V detected by the vehicle speed sensor 112. Based on the steering torque T and the vehicle speed V, a preset assist table is set. Alternatively, the current command value I is calculated from a predetermined arithmetic expression, and the motor is driven by controlling the motor current based on the calculated current command value I.

  In the above-described general electric power steering device, the steering angle of the steered wheel (hereinafter referred to as the rudder angle) is limited due to the structural limitations of the steering device, and the pinion rack that steers the steered wheel The mechanism is provided with a rack end mechanism for preventing movement exceeding a rack movement limit (rack end). In the following description, the rack movement limit and the rack end mechanism provided at the rack movement limit may be simply referred to as a rack end.

  For this reason, when a larger steering torque is applied to the steering wheel when the rack position that moves according to the steering angle of the steering wheel is near the rack end, the motor is driven by a large current command value in response to the large steering torque. As a result, a large steering assist force is applied to the steering apparatus, and the rack may collide violently with the rack end to generate a large impact sound, or the rack end components may be damaged or deformed.

  In response to this problem, when the detected steering angle reaches the vicinity of the angle corresponding to the rack end (the steering angle of the steering wheel when the rack is at the rack end, hereinafter referred to as the rack end angle), the current command A configuration has been proposed in which the value is limited to decrease as the rudder angle increases, the current command value is set to zero when the rudder angle reaches the rack end angle, and the rack is prevented from colliding violently with the rack end. (See Patent Document 1).

  However, in the above configuration, when the steering wheel is turned in the opposite direction in the vicinity of the rack end angle, the current command value Iref is limited until the steering angle becomes a predetermined angle or less. There is a disadvantage that the steering assist force cannot be supplied to the steering mechanism and the steering operation becomes heavy.

  As a countermeasure to this problem, when the detected rudder angle reaches near the rack end angle, the current command value is limited so as to decrease as the rudder angle increases, but in a direction to return the steering wheel to the neutral position. A configuration has been proposed in which the restriction of the current command value is canceled when a steering torque that is greater than or equal to a predetermined value is detected (see Patent Document 2).

  However, when the steering angle reaches the vicinity of the rack end angle, the steering torque changes greatly before and after that, and an appropriate current command value cannot be set.

  As a countermeasure to this problem, a current command value reduction unit is provided after the current command value calculation unit, and when the steering angle reaches the vicinity of the rack end angle, the reduction value of the current command value is reduced, and the motor rotation speed is reduced. A configuration has been proposed in which the reduction value of the current command value is reduced when the value is large (see Patent Document 3).

  FIG. 8 is a block diagram illustrating the function of the control device 130 disclosed in Patent Document 3. A steering torque T from a torque sensor (not shown) is gain-adjusted by a gain adjustment unit 141 and input to the current command value calculation unit 131. A vehicle speed V from a vehicle speed sensor (not shown) is also input to the current command value calculation unit 131. The

  The gain adjustment unit 141 constitutes an amplification unit that multiplies the steering torque T input by the gain K1 output from the hitting noise countermeasure unit 140, which will be described later, and adjusts the gain of the input steering torque T. .

  The hitting noise countermeasure unit 140 is a signal for adjusting a gain by detecting a state immediately before the rack collides in order to mitigate an impact generated when the rack collides with the rack end and suppress an impact sound. In addition to the steering torque T and the vehicle speed V, the steering angle θ output from the steering angle sensor that detects the steering angle of the steering wheel, and the angular velocity ω that is output from the angular velocity sensor that detects the steering angular velocity are input. The The hitting noise countermeasure unit 140 will be described in detail later.

  The compensator 150 calculates compensation information that enhances the stability of the steering system, and adds information based on the self-aligning torque (SAT) of the steering system, information based on the inertia of the motor, information based on the convergence, etc. As compensation information, it is output to the adder 132.

  The current command value calculation unit 131 calculates a current command value Iref based on the input steering torque T and vehicle speed V, and outputs it to the adder 132. The adder 132 adds the input current command value Iref and the compensation information output from the compensation unit 150. The current command value Iref to which the compensation information is added is limited in maximum current by the current limiter 133, and the current command value Irefm in which the maximum current is limited is output to the subtractor 134.

  In the subtractor 134, a difference (Irefm−im) between the current command value Irefm and the fed back motor current im is calculated, and the deviation is processed by the PI control unit 135 that improves the steering characteristics, and the current control value Eref is output. Is done. The PWM control unit 136 determines the duty ratio for driving the motor based on the current control value Eref, and drives the motor 120 via the inverter circuit 137.

  FIG. 9 is a block diagram illustrating the configuration of the hitting noise countermeasure unit 140. The hitting noise countermeasure unit 140 multiplies a steering angle sensitivity gain k1, an angular velocity sensitivity gain k2, and a vehicle speed sensitivity gain k3 described below, and outputs a gain K1 that reduces the steering torque T input based on the multiplication result. It is.

The steering angle θ of the steering wheel is input to the absolute value circuit 401 to be converted into the steering angle absolute value | θ |, input to the steering angle sensitive gain calculation unit 402, and is steered from the stored steering angle sensitive gain table. The gain k1 corresponding to the angle absolute value | θ | is output to the multiplier 403, and the steering angle θ is also output to the determination control unit 410 described later. The steering angle θ is also input to the increase / return determination unit 420.

  The angular velocity ω of the steering wheel is input to the absolute value circuit 404, converted into an absolute angular velocity value | ω |, input to the angular velocity sensitive gain calculation unit 405, and the angular velocity absolute value | ω | from the stored angular velocity sensitive gain table. Is output to the multiplier 403 and also to the determination control unit 410 described later. The vehicle speed V, which is the vehicle speed, is input to the vehicle speed sensitive gain calculation unit 406, and a gain k3 corresponding to the vehicle speed is output from the stored vehicle speed sensitive gain table to the multiplier 407 and also to a determination control unit 410 described later. Is output.

  Here, referring to FIG. 10, the steering angle sensitive gain table stored in the steering angle sensitive gain calculating unit 402, the angular velocity sensitive gain table 405 stored in the angular velocity sensitive gain calculating unit 405, and the vehicle speed sensitive gain calculating unit. The characteristics of the vehicle speed sensitive gain table stored in 406 will be described.

  The steering angle sensitive gain table has characteristics as shown in FIG. That is, the gain k1 = 1 is maintained until the rudder angle absolute value | θ | reaches a predetermined value | θ1 |, and thereafter, the gain decreases by a linear function, and the gain k1 = 0 at | θ2 |.

  The angular velocity sensitive gain table has characteristics as shown in FIG. That is, the gain k2 = 1 is maintained until the angular velocity absolute value | ω | reaches a predetermined value | ω1 |, and thereafter, the gain k2 is decreased by a linear function, and the gain k2 = 0 is obtained at | ω2 |.

  The vehicle speed sensitive gain table has characteristics as shown in FIG. That is, the gain k3 = 1 at the vehicle speed 0, the linear speed decreases from the vehicle speed 0 to V1, the linear function increases from the vehicle speed V1 to V2, and the gain k3 = 1 is maintained thereafter.

  The steering angle absolute value | θ1 | is a limit value for decreasing the gain after the steering angle of the steering wheel approaches the rack end. The absolute angular velocity value | ω | is a limit value for decreasing the gain after the steering wheel is operated rapidly.

  The increase / return determination unit 420 determines the increase / return operation of the steering wheel using the steering torque T, the steering angle θ, and the angular velocity ω as inputs, and a signal DS indicating the determination result is a determination control described later. Is output to the unit 410.

  That is, when the sign of the steering angle θ and the sign of the angular velocity ω are the same sign, it is determined to be increased, and when the sign of the steering angle θ and the sign of the angular velocity ω are different signs, it is determined to switch back. Further, when the sign of the steering torque T and the sign of the steering torque change rate are the same and the absolute value of the steering torque change rate is equal to or greater than a predetermined value, it is determined that the steering torque T is increased. May be determined to be switch-back when the absolute value of the steering torque change rate is equal to or greater than a predetermined value. Further, when the sign of the steering torque T and the sign of the angular velocity ω are the same sign, it may be determined that the number is increased, and when the sign of the steering torque T and the sign of the angular speed ω are different signs, it may be determined that the switch is returned.

  The failure detection unit 421 detects an abnormality or failure of the steering angle sensor or other sensors, and outputs a failure signal AB to the determination control unit 410 when an abnormality or failure is detected.

  The multiplication result of the multiplier 403 is input to the contact point a11 of the switch 422, and the multiplication result of the multiplier 407 is input to the contact point b11 of the switch 422.

  The fixed gain “1” is supplied to the contact point a12 of the switch 423, and the output of the switch 422 is supplied to the contact point b12 of the switch 423. The switches 422 and 423 are switched by switching signals SW1 and SW2 output from the determination control unit 410, respectively. A gain K1a is output from the switch 423 and input to the change rate control unit 424. The change rate control unit 424 limits the change rate of the gain K1a so as not to exceed a predetermined change rate, and the limited gain K1a is output as the gain K1.

  FIG. 11 is a flowchart for explaining the control operation of the determination control unit 410. It is determined whether or not the gain k1 read from the gain table 402 or the gain k2 read from the gain table 405 is “1” (step S1). When the specified condition is satisfied, the switching signal SW2 is output and the switch 423 is output. Is switched to the output side (step S2). As a result, the output gain K1a of the switch 423 becomes “1”, and the gain K1 input to the gain adjustment unit 141 (see FIG. 8) via the rate of change control unit 424 becomes “1”. Is not done.

  If the specified condition is not satisfied as a result of the determination in step S1, the switching signal SW1 is output to switch the contact point a11 of the switch 422 to the output side, and the switching signal SW2 is output to switch the contact point b12 of the switch 423 to the output side. (Steps S3 and S4). As a result, the integrated value (k1 × k2) of the gains k1 and k2 is output through the switches 422 and 423, and is input to the gain adjusting unit 141 (see FIG. 8) through the change rate control unit 424 (= k1 ×). Based on k2), assist limitation for the steering torque T is performed.

  Thereafter, the determination control unit 410 determines whether or not the gain k1 or k2 satisfies the gain “1” or {(steering angle θ × angular velocity ω) ≦ 0} (step S5), and the specified condition is satisfied. Outputs a switching signal SW2 to switch the contact point a12 of the switch 423 to the output side (step S6). As a result, the output gain K1a of the switch 423 becomes “1”, and the gain K1 input to the gain adjustment unit 141 (see FIG. 8) via the rate of change control unit 424 becomes “1”. Is not done.

  Since the determination of {(steering angle θ × angular velocity ω) ≦ 0} is a switchback determination, the switchback determination can also be made based on the determination signal DS output from the switchover / switchback determination unit 420.

  If the specified condition is not satisfied in the determination in step S5, the switching signal SW1 is output to switch the contact b11 of the switch 422 to the output side, and the switching signal SW2 is output to switch the contact b12 of the switch 423 to the output side ( Steps S7 and S8). As a result, the integrated value (k1 × k2 × k3) of the gains k1, k2 and k3 is output through the switches 422 and 423, and is input to the gain adjusting unit 141 (see FIG. 8) through the change rate control unit 424. Based on (= k1 * k2 * k3), assist limitation for the steering torque T is performed.

  Further, the determination control unit 410 determines whether or not the failure signal AB is input from the failure detection unit 421 (step S9). When the failure signal AB is input, the determination control unit 410 outputs the switching signal SW2 and contacts the switch 423. a12 is switched to the output side (step S10). As a result, the output gain K1a of the switch 423 is “1”, and the gain K1 input to the gain adjustment unit 141 (see FIG. 8) via the change rate control unit 424 is “1”. Not done. That is, when an abnormality or failure of the steering angle sensor or other sensors is detected, the assist limitation for the steering torque T is stopped.

According to the control operation of the determination control unit 410 described above, when the steering angle θ of the steering wheel is in the vicinity of the rack end and the angular velocity ω is equal to or larger than the predetermined set value ω1, or at the time of switchback steering, the gain with respect to the steering torque T Reduce K1 to reduce the amount of assist, increase steering wheel steering to reduce angular velocity ω, reduce impact when the rack collides with the rack end, and suppress impact noise (hitting noise) Can do.
Japanese Patent Publication No. 6-4417 JP 2004-175196 A JP 2006-248252 A

  However, in the conventional configuration described above, when the steering is suddenly increased slightly before the rack reaches the rack end, the impact of the rack colliding with the rack end and the generation of abnormal noise are avoided. It turned out that the effect cannot be expected.

  12 is a diagram for explaining changes in the steering angle and steering torque of the steering wheel with respect to time, and FIG. 12 (a) is a diagram for explaining the steering angle of the steering wheel when additional steering is performed. 12 (b) is a diagram for explaining a change in the steering angle with respect to time, and FIG. 12 (c) is a diagram for explaining a change in steering torque with respect to time.

  As shown in FIG. 12 (a), when the steering wheel SW is steered from the front of the rack end (steering angle θs) to the rack end (steering angle θe) and steered, the tire is only twisted. Since it does not move, the frictional force between the tire and the road surface is not applied, so that a large steering torque T is not required and the rack collides with the rack end (FIGS. 12B and 12C). reference). For this reason, as shown in FIG. 12C, if the current command value is reduced and the steering torque T is limited to about Tlim, the movement of the rack shaft colliding with the rack end can be effectively suppressed. Further, it has been found that unless the steering torque T is further limited to about Tlima, the movement of the rack shaft colliding with the rack end cannot be effectively suppressed.

  The present invention solves the above-mentioned problems, and the invention according to claim 1 is a method for calculating a current command value that defines a motor current to be supplied to a motor that applies a steering assist force to a steering mechanism based on a steering torque and a vehicle speed. In an electric power steering apparatus comprising: a command value calculation unit; and a control unit that controls a motor based on the calculated current command value, a steering angular acceleration output unit that outputs a steering angular acceleration of a steering wheel, and a steering A rack that includes a steering angle output unit that outputs a steering angle of a wheel and a vehicle speed output unit that outputs a traveling speed of the vehicle, and the control unit forms a steering mechanism from the steering angle output from the steering angle output unit. From the steering angular acceleration output from the steering angular acceleration output means. When Lumpur is determined to have been abruptly steered to the steer direction is a control device for an electric power steering apparatus characterized by inhibiting the steering assist force applied from the motor to the steering mechanism.

  The steering angular acceleration output means estimates the steering angular acceleration based on the steering angular speed detected by the steering angular acceleration detecting means for detecting the steering angular acceleration of the steering wheel or the steering angular speed detecting means for detecting the steering angular speed. Steering angular acceleration estimation means.

  The control unit limits the steering torque or current command value input based on information selected from steering angular acceleration, steering angular velocity, steering angle, and vehicle speed to a predetermined value or less, and performs steering from the motor. It is assumed that the steering assist force applied to the mechanism is suppressed.

  The controller does not suppress the steering assist force applied from the motor to the steering mechanism when it is determined that the steering wheel is steered in the return direction based on the steering angle code and the steering angular velocity code. To do.

  In addition, when it is determined that the steering wheel is steered in the return direction based on the steering torque code, the steering torque change rate code, and the absolute value of the steering torque change rate, the control unit changes from the motor to the steering mechanism. It is assumed that the steering assist force applied is not suppressed.

  Further, when it is determined that the steering wheel is steered in the return direction based on the steering torque code and the steering angular velocity code, the control unit does not suppress the steering assist force applied from the motor to the steering mechanism. To do.

  The control unit determines that the rack constituting the steering mechanism has approached the rack end based on the steering angular acceleration and the vehicle speed, and if the vehicle speed is equal to or less than a preset limit value, In order not to suppress the steering assist force applied to the steering mechanism, the input steering torque or current command value is not set below a predetermined lower limit value.

  The control device for the electric power steering apparatus according to the present invention determines that the rack constituting the steering mechanism has approached the rack end from the steering angle output from the steering angle output means, and is output from the steering angular acceleration output means. When it is determined from the steering angular acceleration that the steering wheel is steered sharply in the direction to increase, the steering assist force applied from the motor to the steering mechanism is suppressed, so the steering wheel moves from the rack end toward the rack end. Even when the steering is sharply increased, the movement of the rack shaft colliding with the rack end can be effectively suppressed.

  Further, the control device for the electric power steering apparatus according to the present invention determines that the rack constituting the steering mechanism has approached the rack end based on the steering angular acceleration and the vehicle speed, and the vehicle speed is a preset limit value. In the following cases, the steering wheel or the current command value is not set below a predetermined lower limit value so as not to suppress the steering assist force applied from the motor to the steering mechanism. When the rack approaches the rack end, it is possible to avoid a shortage of steering assist force in front of the rack end.

  Hereinafter, a control device for an electric power steering device according to an embodiment of the present invention will be described. The overall configuration of the electric power steering apparatus is the same as the configuration described above with reference to FIG. 7, so the description thereof will be omitted here, and the configuration and function of the control device will be described.

  The control device for the electric power steering apparatus according to the embodiment of the present invention is the rack movement that occurs when the steering is suddenly increased from the front of the rack to the rack end as described in the problem of the invention. An impact / abnormal noise reduction unit and a gain adjustment unit are provided to effectively suppress movement that collides with the end.

  The control device includes a first embodiment for limiting the steering torque and a second embodiment for limiting the current command value. However, the arrangement order of the functional blocks is different between the first embodiment and the second embodiment. Therefore, the functional blocks of the first and second embodiments will be described with the same reference numerals.

[First embodiment]
FIG. 1 is a block diagram for explaining the function of a control device 10A which is a first embodiment of the control unit of the electric power steering apparatus according to the present invention. The impact / abnormal noise reduction unit and the gain adjustment unit described above are current command values. It arrange | positions in the front | former stage of a calculating part, and is comprised so that the input steering torque value may be reduced.

  A steering torque T detected by a torque sensor (not shown) is reduced by multiplying a gain G1 output from an impact / abnormal noise reduction unit 30 described later in the gain adjustment unit 20. The reduced steering torque T and the vehicle speed V detected by a vehicle speed sensor (not shown) are input to the current command value calculation unit 11 to calculate the current command value Iref.

  In the adder 12, compensation information output from the compensation unit 19 described later is added to the current command value Iref and output to the current limiting unit 13. The current limiter 13 limits the maximum current value of the current command value Iref to a preset maximum current value, and the limited current command value Irefm is output to the subtractor 14.

  In the subtractor 14, the difference (Irefm-im) between the current command value Irefm and the fed back motor current im is calculated, and the deviation is processed by the PI control unit 15 that improves the steering characteristics, and the current control value Eref is output. Is done. The PWM control unit 16 determines the duty ratio for driving the motor based on the current control value Eref, and drives the motor 18 via the inverter circuit 17. A motor current im flowing through the motor 18 is detected by a motor current detection circuit (not shown), and the detected motor current im is fed back to the subtractor 14.

  The compensator 19 calculates compensation information that enhances the stability of the steering system, and adds SAT information about the self-aligning torque of the steering system, inertia information about the inertia of the motor, convergence information about the convergence of the steering system, etc. Calculated as compensation information and output to the adder 12.

[Second Embodiment]
FIG. 2 is a block diagram for explaining the function of a control device 10B, which is a second embodiment of the control unit of the electric power steering apparatus according to the present invention. In the impact / abnormal noise reduction unit and the gain adjustment unit, the current command It arrange | positions in the back | latter stage of a value calculating part, and is comprised so that the calculated electric current command value may be reduced.

  A steering torque T detected by a torque sensor (not shown) and a vehicle speed V detected by a vehicle speed sensor (not shown) are input to a current command value calculation unit 11 to calculate a current command value Iref. The calculated current command value Iref is reduced in the gain adjustment unit 20 by multiplying by a gain G1 output from an impact / abnormal noise reduction unit 30 described later.

  In the adder 12, compensation information output from the compensation unit 19 described later is added to the reduced current command value Iref and output to the current limiting unit 13. The current limiter 13 limits the maximum current value of the current command value Iref to a preset maximum current value, and the limited maximum current value Irefm is output to the subtractor 14.

  In the subtractor 14, the difference (Irefm-im) between the current command value Irefm and the fed back motor current im is calculated, and the deviation is processed by the PI control unit 15 that improves the steering characteristics, and the current control value Eref is output. Is done. The PWM control unit 16 determines the duty ratio for driving the motor based on the current control value Eref, and drives the motor 18 via the inverter circuit 17. A motor current im flowing through the motor 18 is detected by a motor current detection circuit (not shown), and the detected motor current im is fed back to the subtractor 14.

  The compensator 19 calculates compensation information that enhances the stability of the steering system, and adds SAT information about the self-aligning torque of the steering system, inertia information about the inertia of the motor, convergence information about the convergence of the steering system, etc. Calculated as compensation information and output to the adder 12.

[Configuration of impact / abnormal noise reduction unit]
FIG. 3 is a block diagram illustrating the configuration of the impact / abnormal noise reduction unit 30, and includes a configuration common to the control device 10 </ b> A of the first embodiment and the control device 10 </ b> B of the second embodiment. The impact / noise reduction unit 30 multiplies a steering angular acceleration gain g4, a steering angular gain g1, an angular velocity gain g2, and a vehicle speed gain g3 described below, and reduces the input steering torque value based on the multiplication result. Alternatively, a gain G1 for reducing the calculated current command value is output.

  The impact / noise reduction unit 30 includes a steering angular acceleration (hereinafter referred to as steering angle acceleration) α output from the steering angular acceleration output means, a steering angle (hereinafter referred to as steering angle) θ output from the steering angle output means, and steering. The steering angular velocity (hereinafter referred to as angular velocity) ω outputted from the angular velocity output means, the vehicle speed V outputted from the vehicle speed output means, and the steering torque T outputted from the steering torque output means are inputted.

  The steering angular acceleration output means is a steering angular acceleration estimation means for estimating and calculating a steering angular acceleration based on a steering angular speed detected by a steering angular acceleration detection means (not shown) for detecting steering angular acceleration or a steering angular speed detection means (not shown). Means.

  The steering angular speed output means includes steering angular speed detection means (not shown) for detecting the steering angular speed, or steering angular speed estimation means for estimating and calculating the steering angular speed based on the steering angle detected by the steering angle detection means (not shown). The steering angle output means includes a steering angle detection means (not shown) that detects the steering angle, or a steering angle estimation means that estimates and calculates the steering angle based on the steering angular velocity detected by the steering angular velocity output means.

  In addition, the vehicle speed output means can use the vehicle speed sensor that detects the vehicle speed described in the background art, and the steering torque output means can use the torque sensor that detects the steering torque.

  The steering angle acceleration sensitive gain calculation unit 32 receives the absolute value | α | of the steering angle acceleration α and the absolute value | θ | of the steering angle θ processed by the absolute value circuit 31, and stores the stored steering angular acceleration. The steering angular acceleration gain g4 corresponding to the steering angular acceleration absolute value | α | is output based on the sensitive gain table.

  The steering angle sensitive gain calculator 34 receives the absolute value | θ | of the steering angle θ processed by the absolute value circuit 33, and based on the stored steering angle sensitive gain table, the steering angle absolute value | θ | A steering angle gain g1 corresponding to is output.

  The absolute value | ω | of the angular velocity ω processed by the absolute value circuit 35 is input to the angular velocity sensitive gain calculation unit 36, and the angular velocity corresponding to the angular velocity absolute value | ω | based on the stored angular velocity sensitive gain table. The gain g2 is output.

  A vehicle speed V is input to the vehicle speed sensitive gain calculation unit 37, and a vehicle speed gain g3 corresponding to the vehicle speed V is output based on the stored vehicle speed sensitive gain table.

  The steering torque lower limit gain setting unit 38 receives the vehicle speed V and the steering angle gain g1, and prevents the steering torque from being excessively reduced in order to prevent the assist torque from becoming insufficient before the rack end. Is output. The steering torque lower limit gain gL1 is a value sensitive to the vehicle speed V. The function of the steering torque lower limit gain setting unit 38 will be described in detail later.

  Referring to FIG. 4, a steering angle acceleration sensitive gain table stored in steering angle acceleration sensitive gain calculating unit 32, a steering angle sensitive gain table stored in steering angle sensitive gain calculating unit 34, and a steering angular velocity sensitive gain calculation. The characteristics of the steering angular velocity sensitive gain table stored in the unit 36 and the vehicle speed sensitive gain table stored in the vehicle speed sensitive gain calculating unit 37 will be described.

  FIG. 4A shows the characteristics of the steering angular acceleration sensitive gain table stored in the steering angular acceleration sensitive gain calculation unit 32. When the steering angular acceleration absolute value | α | is up to | α1 |, the gain g4 = 1, the gain g4 is gradually decreased by a linear function from | α1 | to | α2 |, and the gain g4 = 0 is set at | α2 |. That is, in a region where the steering angle acceleration is fast (such as | α | is large), such as sudden steering near the rack end, the rack collides violently with the rack end and generates a large impact and noise. In a region where the gain g4 is set low and the steering angular acceleration is low (| α | is small), even if the rack collides with the rack end, the impact and noise are not large, so the gain g4 = 1 is set.

  FIG. 4B shows the characteristics of the steering angle sensitive gain table stored in the steering angle sensitive gain calculator 34. The gain g1 = 1 is maintained until the steering angle absolute value | θ | Then, the gain g1 is decreased by a linear function from | θ1 | to | θ2 | where the steering angle is directed toward the rack end, and the gain g1 = 0 is set at the rack end | θ2 |.

  FIG. 4C shows the characteristics of the angular velocity sensitive gain table stored in the steering angular velocity sensitive gain calculator 36. The gain g2 = 1 is maintained until the angular velocity absolute value | ω | From | ω1 | to | ω2 |, the gain g2 is gradually decreased by a linear function, and the gain g2 = 0 is set at | ω2 |. That is, in a region where the angular velocity is high (such as | ω | is large) such as sudden steering near the rack end, the rack violently collides with the rack end and generates a large impact and noise. In order to avoid this, the gain g2 Is set low, and in the region where the angular velocity is low (| ω | is small), even if the rack collides with the rack end, the impact and noise are not large, so the gain g2 = 1.

  FIG. 4 (d) shows the characteristics of the vehicle speed sensitive gain table stored in the vehicle speed sensitive gain calculation unit 37. The gain g3 decreases with a linear function until the vehicle speed V is V1, and from the vehicle speed V1 to V2. Increases by a linear function and recovers to gain g3 = 1, and after the vehicle speed V2, gain g3 = 1 is maintained. That is, when the vehicle speed V is zero (stopped), the gain g3 = 1 is set, and when the vehicle speed V is from zero to the low vehicle speed V1, the rack thrust is large and the gain g3 is decreased. However, the rack thrust is low from the low vehicle speed V1 to the vehicle speed V2. Since it increases, the gain g3 is gradually set higher, and g3 = 1 is set at the vehicle speed V2. At a vehicle speed of V2 or higher, it is unlikely that the rack will collide with the rack end, so the gain g3 is not limited. A vehicle speed V2 that does not limit the gain g3 is set as a threshold (vehicle speed threshold) of the vehicle speed sensitive gain.

  The steering torque lower limit gain setting unit 38 and the steering torque lower limit gain gL output from the steering torque lower limit gain setting unit 38 will be described. The steering torque lower limit gain setting unit 38 limits the steering torque excessively by the operation of the impact / abnormal noise reduction unit 30 and the gain adjustment unit 20 (see FIGS. 1 and 2) when the rack of the steering mechanism approaches the rack end. Thus, the assist torque is prevented from being insufficient before the rack end.

  The vehicle speed V and the steering angle gain g1 are input to the steering torque lower limit gain setting unit 38, and based on the steering angle gain g1, it is determined whether or not it is near the rack end. If it is before the rack end, a steering torque lower limit gain gL (see FIG. 3) corresponding to the vehicle speed V at that time is output.

  FIG. 5 is a diagram for explaining the steering torque lower limit gain gL output from the steering torque lower limit gain setting unit 38 that limits the steering torque (or current control value). The horizontal axis represents the vehicle speed V, and the vertical axis represents the steering torque lower limit gain. gL, line (a) is the steering torque lower limit gain gL at normal time (when the rack is not near the rack end) shown for reference, and line (b) is the steering torque when the rack is near the rack end. The lower limit gain gL1 is shown, and is set to a value smaller than the gain gL at normal time (when the rack is not near the rack end). When the current control value is limited, the steering torque lower limit gain is read as the current control value lower limit gain.

  First, the normal time (when the rack is not near the rack end) will be described. Since the rack thrust is large when the vehicle speed is stopped, the steering torque (or current control value) is not limited. Since the rack thrust is small when the vehicle speed V is in the low speed running state, the steering torque (or current control value) is limited to the lower limit gain gL. When the vehicle speed V is in a high-speed running state, it is unlikely that the rack will collide with the rack end (no rapid steering is performed in high-speed running), so the steering torque (or current control value) is not limited.

  Next, the limitation on the steering torque value (or current control value) when the rack is near the rack end will be described. Since the rack thrust is large when the vehicle speed indicates a stop state, the steering torque (or current control value) is not limited.

  Since the rack thrust is small when the vehicle speed V indicates a low-speed traveling state, the rack may collide with the rack end violently. Therefore, the steering torque (or current control value) is set according to the vehicle speed V in order to prevent violent collision. Limit the gain. The steering torque lower limit value setting unit 38 outputs a steering torque lower limit gain gL1.

  When the vehicle speed V is in a high-speed running state (vehicle speed V = V2 or more), it is unlikely that the rack will collide with the rack end (the steering is not steeper in high-speed running), so the steering torque (or current control value) is Do not limit.

  The increase / return determination unit 39 determines the increase / return operation of the steering wheel, and determines the increase / return operation based on the steering angle θ, the angular velocity ω, and the steering torque T. A signal DS indicating the determination result is output to a determination control unit 41 described later.

  That is, when the sign of the steering angle θ and the sign of the angular velocity ω are the same sign, it is determined to be increased, and when the sign of the steering angle θ and the sign of the angular velocity ω are different signs, it is determined to switch back. Further, when the sign of the steering torque T and the sign of the steering torque change rate are the same and the absolute value of the steering torque change rate is equal to or greater than a predetermined value, it is determined that the steering torque T is increased. May be determined to be switch-back when the absolute value of the steering torque change rate is equal to or greater than a predetermined value. Further, when the sign of the steering torque T and the sign of the angular velocity ω are the same sign, it may be determined that the number is increased, and when the sign of the steering torque T and the sign of the angular speed ω are different signs, it may be determined that the switch is returned.

  The multiplier 40 includes a steering angular acceleration gain g4 output from the steering angular acceleration sensitive gain calculator 32, a steering angle gain g1 output from the steering angle sensitive gain calculator 34, and an angular velocity output from the angular velocity sensitive gain calculator 36. The gain g2 and the vehicle speed gain g3 output from the vehicle speed sensitive gain calculation unit 37 are input, the gain g1, the gain g2, the gain g3, and the gain g4 are multiplied by each, and the gain g5 (g5 = g1 × g2) as a multiplication result is obtained. Xg3gx4) is output to the switch 43.

  The failure detection unit 42 detects an abnormality or failure of the steering angle sensor or other sensors, and outputs a failure signal AB to the determination control unit 41 described later when an abnormality or failure is detected.

  The determination control unit 41 determines whether or not to perform assist limitation on the steering torque T. The steering angle θ, the vehicle speed V, the steering torque lower limit gain gL1, the signal DS indicating the determination result of the increase / return operation, Steering angle gain g1 output from the steering angle sensitive gain calculator 34, Steering angular velocity gain g2 output from the angular velocity sensitive gain calculator 36, Vehicle speed gain g3 output from the vehicle speed sensitive gain calculator 37, From the failure detector 42 A switching signal SW1 (SW1a, SW1b) for switching the switches 43 and 44 based on a determination result as to whether or not to perform assist limitation, with a failure signal AB to be output and a gain G1a as an output of the switch 43 described later as inputs. SW2 (SW2a, SW2b) is output. The control operation of the determination control unit 41 will be described later in detail with reference to the flowchart of FIG.

  The fixed gain “1” is input to the contact point a11 of the switch 43, and the gain g5 that is the multiplication result of the multiplier 40 is input to the contact point b11 of the switch 43. When the contact a11 of the switch 43 is switched to the output side by the switching signal SW1a output from the determination control unit 41, the fixed gain “1” is output as the gain G1a, and the contact b11 of the switch 43 is output by the switching signal SW1b. Is switched to, the gain g5 is output as the gain G1a.

  The output gain G1a (= gain “1” or gain g5) of the switch 43 is input to the contact a12 of the switch 44, and the steering torque lower limit gain gL1 output from the steering torque lower limit value limiting circuit 38 is input to the contact b12 of the switch 44. Is entered. When the contact a12 of the switch 44 is switched to the output side by the switching signal SW2a output from the determination control unit 41, the gain G1a is output to the change rate control unit 45 as the gain G1b, and the switching signal output from the determination control unit 41 When the contact b12 of the switch 44 is switched to the output side by SW2b, the steering torque lower limit lower limit gain gL1 is output to the change rate control unit 45 as the gain G1b.

  The rate-of-change control unit 45 adjusts the rate of change of the assist torque so that the steering torque value or current command value does not suddenly fluctuate and give the driver a sense of incongruity. Specifically, the change rate control unit 45 has a gain G1b. The change rate is adjusted so as not to exceed a predetermined change rate set in advance. The input gain G1b is adjusted and output to the gain adjusting unit 20 (see FIGS. 1 and 2) as the gain G1.

  FIG. 6 is a flowchart for explaining the control operation of the determination control unit 41. It is determined whether or not the sign of the steering angle θ and the sign of the angular velocity ω are different signs (step P11). If the sign of the steering angle θ and the sign of the angular speed ω are different signs, it is determined that the switch is returned and the process proceeds to step P12. . In Step P12, the switch switching signal SW1a is output, the contact a11 of the switch 43 is switched to the output side, the fixed gain “1” is output as the gain G1a, and the process proceeds to Step P17.

  If the sign of the steering angle θ and the sign of the angular velocity ω are the same sign in the determination in step P11, it is determined that the gain is increased and it is determined whether or not the gain g1 is 1 (step P13). Move on to step P2.

  If the gain g1 is not 1 in the determination in step P13, it is determined whether or not the gain g2 is 1 (step P14). If the gain g2 is 1, the process proceeds to step P12.

  If the gain g2 is not 1 in the determination of step P14, it is determined whether or not the vehicle speed V is greater than a preset predetermined vehicle speed V1 (step P15), and the vehicle speed V is greater than a preset predetermined vehicle speed V1. In that case, the process proceeds to Step P12.

  If it is determined in step P15 that the vehicle speed V is not greater than the preset predetermined vehicle speed V1, the process proceeds to step P16, the switching signal SW1b is output, the contact b11 of the switch 43 is switched to the output side, and the gain g5 is changed to the gain G1a. And the process proceeds to Step P17.

  It is determined whether or not the gain G1a is larger than the steering torque lower limit gain gL1 (step P17). When the relationship of (G1a> gL1) is established, the switching signal SW2a is output and the contact a12 of the switch 44 is set to the output side. The gain G1a is output to the change rate control unit 45, and the process proceeds to Step P20.

  When the relationship of (G1a> gL1) is not established in the determination of step P17, the switching signal SW2b is output, the contact b12 of the switch 44 is switched to the output side, and the steering torque lower limit gain gL1 is output to the change rate control unit 45. The process proceeds to Step P20.

  The presence / absence of the failure signal AB output from the failure detection unit 42 is determined (step P20). When the failure signal AB is output, the switching signal SW1a is output to switch the contact point a11 of the switch 43 to the output side (step S20). P21), further, outputs a switching signal SW2a to switch the contact point a12 of the switch 44 to the output side (step P22), outputs a fixed gain “1” to the change rate control unit 45, stops the assist limitation, and enters the main routine. Return.

  If it is determined in step P20 that the failure signal AB is not output, the process immediately returns to the main routine. Based on the gain G1 input to the gain unit 20 (see FIGS. 1 and 2) via the change rate control unit 45, assist limitation for the steering torque T is performed.

  The embodiment of the control device for the electric power steering apparatus according to the present invention has been described above. However, when the rack constituting the steering mechanism is in the vicinity of the rack end, the rack does not collide with the rack end violently even by sudden increase steering. The steering torque or current command value is limited so as to suppress the steering assist force applied from the motor to the steering mechanism. In addition to this, a lower limit value for limiting the steering torque or current command value is provided, so that the rack end It is possible to avoid a shortage of steering assist force in front.

  When the rack constituting the steering mechanism for a vehicle is near the rack end, the steering torque or current command value is limited so that the rack does not collide with the rack end violently even if the steering is suddenly increased and the steering mechanism is damaged. This is a control device for an electric power steering device configured to avoid the generation of abnormal noise.

The block diagram explaining the function of 1st Example of the control apparatus of an electric power steering device. The block diagram explaining the function of 2nd Example of the control apparatus of an electric power steering device. The block diagram explaining the structure of an impact and abnormal noise reduction part. The figure explaining the characteristic of a rudder angle acceleration sensitive gain table, a rudder angle sensitive gain table, an angular velocity sensitive gain table, and a vehicle speed sensitive gain table. The figure explaining the gain which restricts the steering torque value or current control value in a steering torque lower limit value setting part. The flowchart explaining the control operation | movement of a determination control part. The figure explaining an example of the whole structure of an electric power steering device. The block diagram explaining the function of the control apparatus of the conventional electric power steering apparatus. The block diagram explaining the structure of the hitting noise countermeasure part of the conventional control apparatus. The figure explaining the characteristic of the steering angle sensitive gain table of the conventional control apparatus, an angular velocity sensitive gain table, and a vehicle speed sensitive gain table. The flowchart explaining the control operation of the determination control part of the conventional control apparatus. The figure explaining the change of the steering angle and steering torque of a steering wheel with respect to time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10A, 10B Control apparatus 11 Current command value calculating part 12 Adder 13 Current limiting part 14 Subtractor 15 PI control part 16 PWM control part 17 Inverter circuit 18 Motor 19 Compensation part 20 Gain adjustment part 30 Impact / noise reduction part 31, 33, 35 Absolute value circuit 32 Steering angle acceleration sensitive gain computing unit 34 Steering angle sensitive gain computing unit 36 Angular velocity sensitive gain computing unit 37 Vehicle speed sensitive gain computing unit 38 Steering torque lower limit gain setting unit 39 Increase / return determination unit 40 Multiplication 41 Determination control unit 42 Failure detection unit 43, 44 Switch 45 Change rate control unit

Claims (7)

A current command value calculation unit that calculates a current command value that defines a motor current to be supplied to the motor that applies a steering assist force to the steering mechanism based on the steering torque and the vehicle speed; and a motor based on the calculated current command value In an electric power steering device comprising a control unit for controlling,
Steering angular acceleration output means for outputting steering angular acceleration of the steering wheel;
Steering angle output means for outputting the steering angle of the steering wheel;
Vehicle speed output means for outputting the traveling speed of the vehicle,
The controller determines from the steering angle output from the steering angle output means that the rack constituting the steering mechanism has approached the rack end, and steers from the steering angular acceleration output from the steering angular acceleration output means. A control device for an electric power steering device, characterized in that when it is determined that the wheel is steered suddenly in an increasing direction, a steering assist force applied from a motor to a steering mechanism is suppressed. The steering angular acceleration output means estimates a steering angular acceleration based on a steering angular speed detected by a steering angular acceleration detecting means for detecting a steering angular acceleration of a steering wheel or a steering angular speed detecting means for detecting a steering angular speed. 2. The control device for an electric power steering device according to claim 1, wherein the control device is acceleration estimation means. The control unit limits the steering torque or current command value input based on information selected from steering angular acceleration, steering angular velocity, steering angle, and vehicle speed to a predetermined value or less, and changes the motor to the steering mechanism. The control device for an electric power steering apparatus according to claim 1, wherein the applied steering assist force is suppressed. The controller does not suppress the steering assist force applied from the motor to the steering mechanism when it is determined that the steering wheel is steered in the return direction based on the steering angle code and the steering angular velocity code. The control device for an electric power steering device according to any one of claims 1 to 3. The controller is provided from the motor to the steering mechanism when it is determined that the steering wheel is steered in the return direction based on the steering torque code, the steering torque change rate code, and the absolute value of the steering torque change rate. 4. The control device for an electric power steering apparatus according to claim 1, wherein the steering assist force is not suppressed. The controller does not suppress the steering assist force applied from the motor to the steering mechanism when it is determined that the steering wheel is steered in the return direction based on the steering torque code and the steering angular velocity code. The control device for an electric power steering device according to any one of claims 1 to 3. Based on the steering angular acceleration and the vehicle speed, the control unit determines that the rack constituting the steering mechanism has approached the rack end, and if the vehicle speed is less than or equal to a preset limit value, the control unit The input steering torque or current command value is not set to be equal to or lower than a predetermined lower limit value so as not to suppress the steering assist force applied to the engine. Control device for electric power steering device.

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