Steering system control device

Abstract

The difference between the steering force required for right-hand steering and the steering force required for left-hand steering is efficiently reduced. [Solution] The steering device control unit comprises an assist torque calculation unit 30 that calculates an assist torque Ta, which is an input value for operating the second electric motor 28; a first correction value calculation unit 32 that calculates and learns correction values ​​for correcting the assist torque Ta, such as a right steering correction gain MG_R and a left steering correction gain MG_L, and uses the right steering correction gain MG_R, etc., to suppress the left-right difference in steering force applied to a pair of left and right steering wheels; and a calculation permission determination unit 31 that determines whether or not to allow the calculation of the right steering correction gain MG_R, etc., based on the vehicle speed V, steering torque T, steering angle A, and steering speed Vs.

Description

Technical Field

[0006] , , ,

[0005] , ,

[0001] The present invention relates to a control device for a steering apparatus.

Background Art

[0002] In the control device for a steering apparatus described in Patent Document 1, when the steering wheel is steered to the right, a correction value for right steering is added to the assist torque, which is a command signal for operating the electric motor. On the other hand, when the steering wheel is steered to the left, a correction value for left steering is added to the assist torque. In this way, the difference between the steering force when the steering wheel is steered to the right and the steering force when the steering wheel is steered to the left is suppressed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the control device for a steering apparatus of Patent Document 1, after the correction value for right steering and the correction value for left steering are simply calculated, these correction values are merely added to the assist torque, and thus no consideration is given to efficiently reducing the difference between the steering force when the steering wheel is steered to the right and the steering force when the steering wheel is steered to the left.

[0005] The present invention has been made paying attention to such problems, and one object thereof is to provide a control device for a steering apparatus capable of efficiently reducing the difference between the steering force when steering to the right and the steering force when steering to the left.

Means for Solving the Problems

[0007] According to the present invention, the difference between the steering force when steering to the right and the steering force when steering to the left can be efficiently reduced. [Brief explanation of the drawing]

[0008] [Figure 1] This is a side view of the steering device of the first embodiment. [Figure 2] Figure 1 is a cross-sectional view of the hydraulic cylinder device. [Figure 3] This is a functional block diagram of the control device for the steering system of the first embodiment. [Figure 4] This is an explanatory diagram schematically showing the calculation permission determination unit and the first correction value calculation unit of the first embodiment. [Figure 5] This is a functional block diagram of the calculation permission determination unit. [Figure 6] This is a functional block diagram of the first correction value calculation unit. [Figure 7] This is a functional block diagram of the first correction value calculation unit of the second embodiment. [Figure 8] This is an explanatory diagram schematically showing the calculation permission determination unit and the third correction value calculation unit of the third embodiment. [Figure 9] This is a functional block diagram of the third correction value calculation unit of the third embodiment. [Figure 10] This is the reference torque map for the fourth embodiment. [Figure 11] This is a functional block diagram of the control device for the steering system according to the fifth embodiment. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the control device for the steering system of the present invention will be described with reference to the drawings.

[0010] Figure 1 is a side view of the steering device of the first embodiment. Figure 2 is a cross-sectional view of the hydraulic cylinder device 9 of Figure 1.

[0011] The steering system is a so-called integral-type electric steering system, configured to steer the front and rear pairs of steering wheels (not shown) of the two-axle front vehicle. The steering system mainly consists of a steering shaft 1 linked to a steering wheel (not shown), a sector gear (not shown) that is used to steer the front and rear pairs of steering wheels of the two-axle front vehicle via a ball screw mechanism (not shown), a first electric motor (not shown) that provides steering assist force to the steering shaft 1, and a reduction gear (not shown) that reduces the rotation of the first electric motor. The sector gear is connected to each steering wheel via a pitman arm 2 and a link mechanism 3 connected to the pitman arm 2.

[0012] The linkage mechanism 3 comprises a first drag link 4, a first link lever 5, a second drag link 6, a link rod 7, a second link lever 8, a hydraulic cylinder device 9, and a third drag link 10.

[0013] One end of the first drag link 4 is rotatably supported on the pitman arm 2 via the first joint 11, while the other end of the first drag link 4 is rotatably supported on the first link lever 5 via the second joint 12.

[0014] One end of the second drag link 6 is rotatably supported at one end of the first link lever 5 via the third joint 13. On the other hand, the other end of the second drag link 6 is linked to an axis on the front side of the front two axes (not shown).

[0015] One end of the link rod 7 is rotatably supported at the first link lever 5 via the fourth joint 14. On the other hand, the other end of the link rod 7 is rotatably supported at the second link lever 8 via the fifth joint 15.

[0016] The hydraulic cylinder device 9 has a piston rod 16. One end portion 16a of this piston rod 16 is rotatably supported at the second link lever 8 via the sixth joint 17. Further, the hydraulic cylinder device 9 is fixed to a fixed portion 18 provided on the vehicle.

[0017] One end of the third drag link 10 is rotatably connected at one end of the second link lever 8 via the seventh joint 19. On the other hand, the other end of the third drag link 10 is linked to an axis on the rear side of the front two axes (not shown).

[0018] As shown in FIG. 2, the hydraulic cylinder device 9 is mainly composed of a cylinder 20, a piston rod 16, a piston 21, a first lid member 22, and a second lid member 23.

[0019] The cylinder 20 has a cylindrical shape. One end in the longitudinal direction is closed by the first lid member 22, and on the other hand, the other end in the longitudinal direction is closed by the second lid member 23.

[0020] The piston rod 16 is generally formed in a cylindrical shape and has a first shaft portion 16c and a second shaft portion 16d that is formed integrally with one end of the first shaft portion 16c and has a smaller diameter than the first shaft portion 16c. At the other end of the first shaft portion 16c, a supported portion 16e having a hole portion 24 into which the above-described sixth joint 17 is inserted is integrally formed.

[0021] The piston 21 is cylindrical and has a through hole 21a into which the second shaft portion 16d of the piston rod 16 is inserted. With the second shaft portion 16d of the piston rod 16 inserted into the through hole 21a, the piston 21 is fixed to the piston rod 16 by screwing a nut 25 onto a male threaded portion provided on the second shaft portion 16d. The piston 21 divides the space inside the cylinder 20 into a first cylinder chamber P1 located on the second lid member 23 side and a second cylinder chamber P2 located on the first lid member 22 side. The first cylinder chamber P1 and the second cylinder chamber P2 are connected to a hydraulic pump (not shown) via a first supply unit 26 and a second supply unit 27 provided on the cylinder 20, respectively. This hydraulic pump is capable of supplying hydraulic pressure to the hydraulic cylinder device 9 and is configured to switch the hydraulic pressure in two directions according to the rotation direction of a second electric motor 28 (see Figure 3), which is not shown. The second electric motor 28 corresponds to the "electric motor" in the claims.

[0022] Furthermore, the piston 21 has a first pressure-receiving surface 21c that receives the hydraulic pressure of the oil supplied to the first cylinder chamber P1, and a second pressure-receiving surface 21d that receives the hydraulic pressure of the oil supplied to the second cylinder chamber P2. Compared to the area of ​​the second pressure-receiving surface 21d, the area of ​​the first pressure-receiving surface 21c is narrowed by the radial cross-sectional integral of the second shaft portion 16d of the piston rod 16, so the area of ​​the first pressure-receiving surface 21c is narrower than the area of ​​the second pressure-receiving surface 21d.

[0023] The first lid member 22 has a mounting hole 22a for attachment to the fixing part 18 (see Figure 1).

[0024] The second cover member 23 has a through hole 23a in which the first shaft portion 16c of the piston rod 16 is slidably positioned.

[0025] The second electric motor 28 is configured as a three-phase brushless motor and is driven and controlled by a motor control unit 29 (see Figure 3), which is part of an ECU controller (control device) not shown. The second electric motor 28 drives the hydraulic pump described above and supplies oil into the first cylinder chamber P1 and the second cylinder chamber P2 of the hydraulic cylinder device 9, thereby moving the piston rod 16 and driving the second link lever 8. In this way, the second electric motor 28 provides steering assist force to the steering force input from the steering wheel, more specifically, the steering force transmitted from the steering shaft 1 side to the second link lever 8 via the pitman arm 2, the first drag link 4, the first link lever 5, and the link rod 7.

[0026] The motor control unit 29 receives information on the required assist torque (the assist torque required to drive the hydraulic cylinder device 9) calculated based on the steering torque and steering direction acquired by a torque sensor (not shown). The motor control unit 29 then drives and controls the electric motor according to the assist torque based on the steering torque and steering direction.

[0027] In this hydraulic cylinder device 9, when the driver steers the steering wheel to the left, the second electric motor 28 rotates to the left, causing oil to flow from the hydraulic pump into the first cylinder chamber P1 via the first supply unit 26. The increase in hydraulic pressure in the first cylinder chamber P1 pushes the piston 21 towards the first cover member 22, and consequently, the piston rod 16 also moves towards the first cover member 22. As a result, the second link lever 8 is pulled toward the pitman arm 2, causing the steering wheel on the rear axle of the two front axles to be steered to the left via the third drag link 10.

[0028] Furthermore, when the driver steers the steering wheel to the right, the second electric motor 28 rotates to the right, causing oil to flow into the second cylinder chamber P2 via the second supply unit 27. The increase in hydraulic pressure in the second cylinder chamber P2 pushes the piston 21 toward the second cover member 23, and consequently, the piston rod 16 also moves toward the second cover member 23. As a result, the second link lever 8 is pushed away from the pitman arm 2, causing the steering wheel on the rear axle of the two front axles to be steered to the right via the third drag link 10.

[0029] Figure 3 is a functional block diagram of the control device for the steering device according to the first embodiment. Figure 4 is an explanatory diagram schematically showing the calculation permission determination unit 31 and the first correction value calculation unit 32 of the first embodiment. Figure 5 is a functional block diagram of the calculation permission determination unit 31. Figure 6 is a functional block diagram of the first correction value calculation unit 32.

[0030] As shown in Figure 3, the control device includes an assist torque calculation unit 30, a calculation permission determination unit 31, a first correction value calculation unit 32, and a first multiplication unit 33.

[0031] The assist torque calculation unit 30 calculates the assist torque Ta, which is a basic command signal (command input value) for operating the second electric motor 28, based on the steering torque T detected by a torque sensor (not shown) provided on the steering device. The steering torque T is output as a value that is positive when steering to the right, for example, and negative when steering to the left.

[0032] As shown in Figures 4 and 5, the calculation permission determination unit 31 generates a calculation permission signal EN that permits the calculation of the correction value in the first correction value calculation unit 32 based on the vehicle speed V, steering angle A, steering speed Vs, and steering torque T. The vehicle speed V is detected by a vehicle speed sensor (not shown) installed on the vehicle. The steering angle A is detected by a steering angle sensor (not shown) installed on the steering device. The steering angle A is output as a value that is positive when steering to the right, for example, and negative when steering to the left. The steering speed Vs is obtained by dividing the steering angle A obtained from the steering angle sensor by the time required for steering. As shown in Figure 5, the calculation permission determination unit 31 has a vehicle speed determination unit 34, a steering angle determination unit 35, a steering speed determination unit 36, and a steering depth determination unit 37.

[0033] The vehicle speed determination unit 34 outputs a true determination result to the first logical AND unit 38 when the vehicle speed V is within a predetermined vehicle speed range. More specifically, as shown in Figure 5, the vehicle speed determination unit 34 outputs a true determination result to the first logical AND unit 38 when the vehicle speed upper limit comparison unit 39 determines that the vehicle speed V is less than a predetermined vehicle speed upper limit, and the vehicle speed lower limit comparison unit 40 determines that the vehicle speed V is greater than a predetermined vehicle speed lower limit. Here, the range between the predetermined vehicle speed upper limit and the predetermined vehicle speed lower limit is set to a specific range that assumes, for example, that the steering torque T when steering to the right and the steering torque T when steering to the left will be the same, assuming that there is no influence from the left-right difference in the components connecting the third drag link 10 to the left and right steering wheels.

[0034] The steering angle determination unit 35 outputs a true determination result to the second logical AND unit 41 when the steering angle A is within a predetermined steering angle range, based on the steering angle A. More specifically, as shown in Figure 5, the steering angle determination unit 35 outputs a true determination result to the second logical AND unit 41 when the steering angle upper limit comparison unit 42 determines that the steering angle A is less than a predetermined steering angle upper limit, and the steering angle lower limit comparison unit 43 determines that the steering angle A is greater than a predetermined steering angle lower limit. Here, similar to the range between a predetermined vehicle speed upper limit and a predetermined vehicle speed lower limit, the range between a predetermined steering angle upper limit and a predetermined steering angle lower limit is set to a specific range that assumes, for example, that the steering torque T when steering to the right and the steering torque T when steering to the left would be the same if there were no influence from the left-right difference in the components connecting the third drag link 10 to the left and right steering wheels.

[0035] The steering speed determination unit 36 ​​outputs a true determination result to the third logical AND unit 44 when the steering speed Vs is within a predetermined steering speed range. More specifically, as shown in Figure 5, the steering speed determination unit 36 ​​outputs a true determination result to the third logical AND unit 44 when the steering speed upper limit comparison unit 45 determines that the steering speed Vs is less than a predetermined steering speed upper limit, and the steering speed lower limit comparison unit 46 determines that the steering speed Vs is greater than a predetermined steering speed lower limit. Here, similar to the range between a predetermined vehicle speed upper limit and a predetermined vehicle speed lower limit, and the range between a predetermined steering angle upper limit and a predetermined steering angle lower limit, the range between a predetermined steering speed upper limit and a predetermined steering speed lower limit is set to a specific range that assumes, for example, that the steering torque T when steering to the right and the steering torque T when steering to the left would be the same if there were no influence from the left-right difference in the components connecting the third drag link 10 to the left and right steering wheels.

[0036] The steering wheel engagement determination unit 37 determines whether or not there is steering wheel engagement based on the steering angle A and steering torque T, and outputs the true determination result to the fourth logical AND unit 47 if there is engagement. More specifically, as shown in Figure 5, in the steering wheel engagement determination unit 37, the steering angle A is multiplied by the steering torque T in the second multiplication unit 48, and the first comparison unit 49 determines whether or not this multiplication result is greater than 0, that is, whether or not the signs of the steering torque T and steering angle A match. For example, if the steering torque T is a positive value and the steering angle A is a positive value, the first comparison unit 49 determines that the multiplication result of the steering torque T and steering angle A is greater than 0 (a positive value), and thus outputs the true determination result to the fourth logical AND unit 47. Furthermore, for example, if the steering torque T is a positive value and the steering angle A is a negative value, the first comparison unit 49 determines that the product of the steering angle A and the steering torque T is less than 0 (a negative value), and thus outputs a false determination result to the fourth logical AND unit 47.

[0037] When a true determination result is output in all of the vehicle speed determination unit 34, steering angle determination unit 35, steering speed determination unit 36, and steering depth determination unit 37, the fourth logical AND unit 47 of the calculation permission determination unit 31 outputs a calculation permission signal EN that permits the calculation of correction gains, in this embodiment, the correction gain MG_R for right steering and the correction gain MG_L for left steering.

[0038] As shown in Figure 6, the first correction value calculation unit 32 includes a steering torque averaging processing unit 50 and a first correction value calculation unit 51.

[0039] The steering torque averaging processing unit 50 includes a second comparison unit 52, a fifth logical AND unit 53, a first NOT gate 54, a sixth logical AND unit 55, a right steering averaging processing unit 56, a left steering averaging processing unit 57, a right steering averaging processing completion determination unit 58, and a left steering averaging processing completion determination unit 59.

[0040] The second comparison unit 52 determines, based on the steering torque T, whether the steering torque T is the steering torque T when steering to the right (1:R) or the steering torque T when steering to the left (0:L). If it is determined that the steering torque T is the steering torque T when steering to the right, this determination result is output to the fifth logical AND unit 53 as the true determination result.

[0041] The fifth logical AND unit 53 outputs a right steering average processing permission signal ENav_R to the right steering average processing unit 56 and the right steering average processing completion determination unit 58 when a true determination result and an operation permission signal EN are input. This right steering average processing permission signal ENav_R is a signal that permits the right steering average processing unit 56 to perform average processing (average processing_R) and the right steering average processing completion determination unit 58 to perform determination (average processing completion determination_R).

[0042] Furthermore, if the second comparison unit 52 determines that the steering torque T is the steering torque T when steering to the left, this determination result is output to the sixth logical AND unit 55 via the first NOT gate 54 as a false determination result.

[0043] The sixth logical AND unit 55 outputs a left steering average processing permission signal ENav_L to the left steering average processing unit 57 and the left steering average processing completion determination unit 59 when a false judgment result and an operation permission signal EN are input. This left steering average processing permission signal ENav_L is a signal that permits the execution of average processing (average processing_L) in the left steering average processing unit 57 and the execution of determination (average processing completion determination_L) in the left steering average processing completion determination unit 59.

[0044] The right steering average processing unit 56 calculates the average value of the steering torque T during right steering, Tav_R, by averaging the steering torque T (averaging_R) when the right steering average processing permission signal ENav_R is input from the fifth logical AND unit 53. In this embodiment, the calculation of the average value of the steering torque T during right steering is performed by a general averaging process that sequentially calculates the average value. Alternatively, the calculation of the average value of the steering torque Tav_R during right steering may be performed by a moving average process instead of the general averaging process described above. Alternatively, the calculation of the average value of the steering torque Tav_R during right steering may be performed by an averaging process using a low-pass filter instead of the general averaging process described above.

[0045] The left steering average processing unit 57 calculates the average value of the steering torque T during left steering, Tav_L, by averaging the steering torque T during left steering (averaging_L) when the left steering average processing permission signal ENav_L is input from the sixth logical AND unit 55. In this embodiment, the calculation of the average value of the steering torque T during left steering is performed by a general averaging process that sequentially calculates the average value. Alternatively, the calculation of the average value of the steering torque Tav_L during left steering may be performed by a moving average process instead of the general averaging process described above. Alternatively, the calculation of the average value of the steering torque Tav_L during left steering may be performed by an averaging process using a low-pass filter instead of the general averaging process described above.

[0046] The right steering average processing completion determination unit 58 measures the cumulative time spent performing the average processing of the steering torque T during right steering when the right steering average processing permission signal ENav_R is input from the fifth logical AND unit 53. When this cumulative time is longer than a predetermined time, it turns on the right steering average processing completion flag F_R, which indicates the completion of the average processing of the steering torque T during right steering.

[0047] The left steering average processing completion determination unit 59 measures the cumulative time spent performing the average processing of the steering torque T during left steering when the left steering average processing permission signal ENav_L is input from the sixth logical AND unit 55. When this cumulative time is longer than a predetermined time, it turns on the left steering average processing completion flag F_L, which indicates the completion of the average processing of the steering torque T during left steering.

[0048] The first correction value calculation unit 51 includes a first absolute value generation unit 60, a second absolute value generation unit 61, a third comparison unit 62, a first determination unit 63, a second determination unit 64, a seventh logical AND unit 65, a first addition unit 66, a first gradually increasing value storage unit 67, a left steering correction value correction unit 68, and a first learning speed adjustment unit 69. The first correction value calculation unit 51 performs learning control for the gradual increase of the right steering correction gain MG_R in the first addition unit 66, and the gradual decrease of the left steering correction gain MG_L in the left steering correction value correction unit 68.

[0049] The first absolute value generation unit 60 generates the absolute value of the average steering torque Tav_R during right steering, based on the average steering torque Tav_R obtained by the average processing unit 56 for right steering.

[0050] The second absolute value generation unit 61 generates the absolute value of the average steering torque Tav_L during left steering, based on the average steering torque Tav_L obtained by the left steering averaging processing unit 57.

[0051] Here, for example, if there is a difference between the left and right components connecting the third drag link 10 to the left and right steering wheels, a difference in steering assist force will exist between right and left steering. Also, as mentioned above, since the area of ​​the first pressure-receiving surface 21c of the piston 21 is smaller than the area of ​​the second pressure-receiving surface 21d, a difference in steering assist force transmitted to the second link lever 8 via the piston rod 16 will exist between right and left steering. In addition to this, manufacturing tolerances and maintenance methods of the hydraulic cylinder device 9 can also cause a difference in steering assist force between right and left steering. Furthermore, the road surface conditions on which the vehicle travels, for example when the vehicle is traveling on a banked road, can cause a difference in steering assist force between right and left steering, and may also change. Thus, a difference in steering assist force occurs between right-hand and left-hand steering, and this difference can change while the vehicle is in motion. Therefore, the absolute values ​​of the average steering torque Tav_R when steering to the right and the absolute values ​​of the average steering torque Tav_L when steering to the left can constantly fluctuate while the vehicle is in motion.

[0052] The third comparison unit 62 determines whether the absolute value of the average steering torque Tav_R when steering to the right is greater than the absolute value of the average steering torque Tav_L when steering to the left. If the absolute value of the average steering torque Tav_R when steering to the right is greater than the absolute value of the average steering torque Tav_L when steering to the left, the third comparison unit 62 outputs a true determination result to the first determination unit 63. If the absolute value of the average steering torque Tav_R when steering to the right is less than or equal to the absolute value of the average steering torque Tav_L when steering to the left, it outputs a false determination result to the first determination unit 63.

[0053] The first determination unit 63 outputs the true or false determination result input from the third comparison unit 62 to the second determination unit 64.

[0054] The seventh logical AND unit 65 outputs a gradual increase permission signal to the second determination unit 64 when it determines that the right steering average processing completion flag F_R, the left steering average processing completion flag F_L, and the calculation permission signal EN are all on.

[0055] The first adder 66 gradually increases the right steering correction gain MG_R when it receives a true determination result from the second determination unit 64 and a gradual increase permission signal from the seventh logical AND unit 65. This gradual increase is performed by adding the gradual increase value stored in the first gradual increase value storage unit 67 to the previous value of the right steering correction gain MG_R. The previous value of the right steering correction gain MG_R is the right steering correction gain calculated immediately before the current calculation of the right steering correction gain MG_R. Note that if any one of the right steering average processing completion flag F_R, left steering average processing completion flag F_L, or calculation permission signal EN is off in the seventh logical AND unit 65, the gradual increase processing of the right steering correction gain MG_R is not performed, and the previous value of the right steering correction gain MG_R is used.

[0056] Furthermore, as the right steering correction gain MG_R increases, the left steering correction value correction unit 68 gradually decreases the left steering correction gain MG_L. The increasing value of the right steering correction gain MG_R is set to be equal to the decreasing value of the left steering correction gain MG_L. For example, if the right steering correction gain MG_R after the increase becomes 1.1 times that of before the increase, the left steering correction gain MG_L after the decrease becomes 0.9 times that of before the decrease.

[0057] The first learning speed adjustment unit 69 slows down the gradual increase process of the right steering correction gain MG_R in the first addition unit 66 and the gradual decrease process of the left steering correction gain MG_L in the left steering correction value correction unit 68 when a false judgment result is input to the first judgment unit 63. In other words, the first learning speed adjustment unit 69 slows down the learning speed of the right steering correction gain MG_R and the left steering correction gain MG_L so that the right steering correction gain MG_R and the left steering correction gain MG_L do not change immediately when a false judgment result is input to the first judgment unit 63.

[0058] As described above, in the first embodiment, the first correction value calculation unit 32 calculates and learns correction values ​​for correcting the assist torque Ta, namely the correction gain MG_R for right steering and the correction gain MG_L for left steering. In other words, the first correction value calculation unit 32 corrects the assist torque Ta using the correction gain MG_R for right steering and the correction gain MG_L for left steering, and the result of this correction is learned and controlled during vehicle operation. Therefore, compared to the case where the correction gain MG_R for right steering and the correction gain MG_L for left steering are simply calculated during vehicle operation, the difference between the steering force during right steering and the steering force during left steering can be efficiently reduced by flexibly responding to the changes in steering assist force during right steering and left steering that may change during vehicle operation.

[0059] Furthermore, in this embodiment, when a true determination result is output in all of the vehicle speed determination unit 34, steering angle determination unit 35, steering speed determination unit 36, and steering depth determination unit 37, the fourth logical AND unit 47 of the calculation permission determination unit 31 outputs a calculation permission signal EN that permits the calculation of the right steering correction gain MG_R and the left steering correction gain MG_L. As described above, for example, in the vehicle speed determination unit 34, the range between a predetermined upper vehicle speed limit and a predetermined lower vehicle speed limit is set to a specific range that assumes, for example, that the steering torque T when steering to the right and the steering torque T when steering to the left will be the same if there is no influence from the left-right difference in the components connecting the third drag link 10 to the left and right steering wheels. Similarly, ranges are set for the steering angle determination unit 35 and the steering speed determination unit 36. In this way, by pre-defining the range for making a correct judgment before processing in the first correction value calculation unit 32, the correction gain MG_R for right steering and the correction gain MG_L for left steering can be efficiently calculated only within the specific range where the difference between the steering force when steering to the right and the steering force when steering to the left should be considered.

[0060] Furthermore, in this embodiment, the first adder 66 gradually increases the right steering correction gain MG_R when the third comparison unit 62 determines that the absolute value of the average steering torque Tav_R during right steering is greater than the absolute value of the average steering torque Tav_L during left steering. Accordingly, the left steering correction value correction unit 68 gradually decreases the left steering correction gain MG_L. Therefore, once the amount of increase of the right steering correction gain MG_R is determined, the amount of decrease of the left steering correction gain MG_L is uniquely determined, eliminating the need to calculate the right steering correction gain MG_R and the left steering correction gain MG_L separately.

[0061] Figure 7 is a functional block diagram of the first correction value calculation unit 32 of the second embodiment.

[0062] The first correction value calculation unit 32 of the second embodiment has a second correction value calculation unit 70 which is different from the first correction value calculation unit 51 of the first embodiment. The second correction value calculation unit 70 of the second embodiment is configured by adding a fourth comparison unit 71 and a subtraction unit 72 to the first correction value calculation unit 51 of the first embodiment.

[0063] The subtraction unit 72 subtracts the absolute value of the average steering torque value when steering to the left, obtained by the second absolute value generation unit 61, from the absolute value of the average steering torque value when steering to the right, Tav_R, obtained by the first absolute value generation unit 60.

[0064] The fourth comparison unit 71 determines whether the difference between the subtraction result from the subtraction unit 72, that is, the absolute value of the average steering torque value Tav_R when steering to the right and the average steering torque value Tav_L when steering to the left, is greater than a predetermined dead zone width. If the subtraction result is greater than the predetermined dead zone width, the fourth comparison unit 71 outputs the true determination result to the seventh logical AND unit 65. The seventh logical AND unit 65 outputs a gradual increase permission signal to the second determination unit 64 when it receives the true determination result from the fourth comparison unit 71, the average processing completion flag F_R for steering to the right and the average processing completion flag F_L for steering to the left are on, and the calculation permission signal EN is input.

[0065] Furthermore, if the subtraction result is less than or equal to a predetermined dead zone, the fourth comparison unit 71 performs dead zone processing. For example, in normal processing, if the subtraction result in the subtraction unit 72 is 0.1 Nm, then the gradual increase of the right steering correction gain MG_R and the gradual decrease of the left steering correction gain MG_L are performed. In the dead zone processing, the above gradual increase and decrease processing are not performed until the result exceeds 0.3 Nm.

[0066] As described above, in the second embodiment, the fourth comparison unit 71 determines whether the difference between the subtraction result in the subtraction unit 72, that is, the absolute value of the average steering torque Tav_R when steering to the right and the absolute value of the average steering torque Tav_L when steering to the left, is greater than a predetermined dead zone. Therefore, if the subtraction result is less than or equal to the predetermined dead zone, the fourth comparison unit 71 performs dead zone processing, thereby reducing the load on the gradual increase processing of the correction gain MG_R for steering to the right and the gradual decrease processing of the correction gain MG_L for steering to the left.

[0067] Figure 8 is a schematic diagram showing the calculation permission determination unit 31 and the third correction value calculation unit 73 of the third embodiment. Figure 9 is a functional block diagram of the third correction value calculation unit 73 of the third embodiment.

[0068] In the third embodiment, the first correction value calculation unit 32 of the first embodiment is abolished, and a third correction value calculation unit 73 is newly provided. In the third embodiment, instead of determining whether the absolute value of the average steering torque Tav_R when steering to the right is greater than the absolute value of the average steering torque Tav_L when steering to the left, as in the first embodiment, it is determined whether the absolute value of the steering torque T is greater than a predetermined reference torque Ts.

[0069] As shown in Figure 9, the third correction value calculation unit 73 includes a third absolute value generation unit 74, a fifth comparison unit 75, a third determination unit 76, a fourth determination unit 77, a sixth comparison unit 78, an eighth logical AND unit 79, a ninth logical AND unit 80, a second NOT gate 81, a fifth determination unit 82, a second addition unit 83, a second gradually increasing value storage unit 84, a third addition unit 85, a third gradually increasing value storage unit 86, and a second learning speed adjustment unit 87.

[0070] The third absolute value generation unit 74 generates the absolute value of the steering torque T based on the steering torque T.

[0071] The fifth comparison unit 75 determines whether the absolute value of the steering torque T generated by the third absolute value generation unit 74 is greater than or equal to a predetermined reference torque Ts. If the absolute value of the steering torque T is greater than or equal to the predetermined reference torque Ts, the fifth comparison unit 75 outputs a true determination result to the third determination unit 76. If the absolute value of the steering torque T is less than the predetermined reference torque Ts, it outputs a false determination result to the third determination unit 76.

[0072] The third determination unit 76 outputs the true or false determination result input from the fifth comparison unit 75 to the fourth determination unit 77.

[0073] The sixth comparison unit 78 determines, based on the steering torque T, whether the steering torque T is the steering torque T when steering to the right (1:R) or the steering torque T when steering to the left (0:L). If it is determined that the steering torque T is the steering torque T when steering to the right, this determination result is output to the eighth logical AND unit 79 as the true determination result.

[0074] Furthermore, if the sixth comparison unit 78 determines that the steering torque T is the steering torque T when steering to the left, this determination result is output to the ninth logical AND unit 80 via the second NOT gate 81 as a false determination result.

[0075] The eighth logical AND unit 79 outputs a gradual increase permission processing signal to the fourth determination unit 77 when it receives a true determination result from the sixth comparison unit 78 and an operation permission signal EN.

[0076] The ninth logical AND unit 80 outputs a gradual increase processing permission signal to the fifth determination unit 82 when it receives a false determination result from the sixth comparison unit 78 and an operation permission signal EN.

[0077] The fifth determination unit 82 outputs the true determination result to the second adder unit 83 when it receives the true determination result from the third determination unit 76 and the gradual increase permission processing signal from the eighth logical AND unit 79.

[0078] The second adder 83 gradually increases the right steering correction gain MG_R when it determines that a true determination result and a gradual increase permission processing signal have been input to the fourth determination unit 77. This gradual increase is performed by adding the gradual increase value stored in the second gradual increase value storage unit 84 to the previous value of the right steering correction gain MG_R. When the right steering correction gain MG_R is gradually increased, the left steering correction gain MG_L is gradually decreased. The gradual increase of the right steering correction gain MG_R and the gradual decrease of the left steering correction gain MG_L are performed so that the steering torque T during right steering after the gradual increase and the steering torque T during left steering after the gradual decrease match a predetermined reference torque Ts.

[0079] The third adder 85 gradually increases the left steering correction gain MG_L when it determines that a true determination result and a gradual increase permission processing signal have been input to the fifth determination unit 82. This gradual increase is performed by adding the gradual increase value stored in the third gradual increase value storage unit 86 to the previous value of the left steering correction gain MG_L. When the left steering correction gain MG_L is gradually increased, the right steering correction gain MG_R is gradually decreased. The gradual increase of the left steering correction gain MG_L and the gradual decrease of the right steering correction gain MG_R are performed so that the steering torque T during left steering after the gradual increase and the steering torque T during right steering after the gradual decrease match a predetermined reference torque Ts.

[0080] The second learning speed adjustment unit 87 slows down the gradual decrease process of the right steering correction gain MG_R in the second adder 83 and the gradual increase process of the left steering correction gain MG_L in the third adder 85 when a false judgment result is input to the third judgment unit 76. In other words, when a false judgment result is input to the third judgment unit 76, the second learning speed adjustment unit 87 slows down the learning speed of the gradual decrease of the right steering correction gain MG_R and the gradual increase of the left steering correction gain MG_L so that the right steering correction gain MG_R and the left steering correction gain MG_L do not change immediately.

[0081] As described above, in the third embodiment, the absolute value of the steering torque T is compared with a predetermined reference torque Ts. For example, if the steering torque T when steering to the right is also biased to one side (for example, the side where steering becomes heavier) than the steering torque T when steering to the left due to manufacturing errors in the steering device, there is no point in comparing the steering torque T when steering to the right with the steering torque T when steering to the left. Therefore, by comparing the absolute value of the steering torque T with a predetermined reference torque Ts as in this embodiment, the calculation of the correction gain MG_R for right steering and the correction gain MG_L for left steering can be performed even when there is a bias to one side in both the steering torque T when steering to the right and the steering torque T when steering to the left as described above.

[0082] Figure 10 shows the reference torque map 88 of the fourth embodiment.

[0083] In the fourth embodiment, unlike the third embodiment, the third correction value calculation unit 73 receives a reference torque Tt based on the vehicle speed V and steering angle A, rather than a predetermined reference torque Ts. The reference torque Tt is obtained by referring to a reference torque map 88 that shows the reference torque Tt for the vehicle speed V and steering angle A. The reference torque map 88 is configured such that, for example, the horizontal axis shows the steering angle A, the vertical axis shows the reference torque Tt, and further has three reference torques Tt1, Tt2, and Tt3 corresponding to three different vehicle speeds.

[0084] As described above, in the fourth embodiment, the third correction value calculation unit 73 receives a reference torque Tt based on the vehicle speed V and steering angle A. Therefore, since the reference torque Tt is obtained based on the vehicle speed V and steering angle A over the entire range, the time during which the calculation permission signal EN is applied can be extended compared to the case where the calculation permission signal EN is generated based on a specific range of vehicle speed V and steering angle A.

[0085] Figure 11 is a functional block diagram of the control device for the steering system according to the fifth embodiment.

[0086] In the fifth embodiment, the first correction value calculation unit 32 of the first embodiment is configured to calculate a correction torque instead of a correction gain as the correction value. Accordingly, in the fifth embodiment, the first multiplication unit 33 of the first embodiment is replaced by a fourth addition unit 89. The fourth addition unit 89 adds the correction torque calculated by the first correction value calculation unit 32, which in this embodiment is the correction torque MT_R for right steering and the correction torque MT_L for left steering, to the assist torque Ta calculated by the assist torque calculation unit 30.

[0087] This fifth embodiment, as with the first embodiment, can efficiently reduce the difference between the steering force when turning right and the steering force when turning left.

[0088] In the embodiments described above, an example was disclosed in which a hydraulic cylinder device 9 provides steering assist force to the steering wheel that is linked to the rear of the two front axles of a front-two-axle vehicle when the second electric motor 28 is driven. However, the present invention can also be applied to a general integral type steering device used in a vehicle with one front and one rear axle, which has a power cylinder and is capable of providing steering assist force to the steering shaft by an electric motor. [Explanation of symbols]

[0089] 28...Second electric motor, 30...Assist torque calculation unit, 31...Calculation permission determination unit, 32...First correction value calculation unit, MG_R...Correction gain for right steering, MG_L...Correction gain for left steering, 33...First multiplication unit, 34...Vehicle speed determination unit, 35...Steering angle determination unit, 36...Steering speed determination unit, 37...Cut depth determination unit, EN...Calculation permission signal, 50...Steering torque averaging processing unit, 51... ...First correction value calculation unit, 56...Average processing unit for right steering, 57...Average processing unit for left steering, 62...Third comparison unit, 66...First addition unit, 70...Second correction value calculation unit, 71...Fourth comparison unit, 72...Subtraction unit, 73...Third correction value calculation unit, Ts...Reference torque, Tt...Reference torque, 88...Reference torque map, MT_R...Corrected torque for right steering, MT_L...Corrected torque for left steering

Claims

1. A steering control device comprising an electric motor that provides steering assist force to the steering force input from the steering wheel, and a control device that drives and controls the electric motor, wherein a pair of left and right steering wheels are steered by the drive of a link accompanying the operation of the electric motor, An assist torque calculation unit that calculates the assist torque, which is an input value for operating the electric motor, A correction value calculation unit calculates and learns a correction value to correct the assist torque, and this correction value is used to suppress the left-right difference in steering force applied to the left and right pair of steering wheels, A calculation permission determination unit determines whether or not to allow the calculation of the correction value based on vehicle speed, steering torque, steering angle, and steering speed, A control device for a steering system, characterized by comprising the following features.

2. A control device for a steering device according to claim 1, A vehicle speed determination unit that outputs a true determination result when the vehicle speed is within a predetermined vehicle speed range, A steering angle determination unit that outputs a true determination result when the steering angle is within a predetermined steering angle range, A steering speed determination unit that outputs a true determination result when the steering speed is within a predetermined steering speed range, A cut-in determination unit that determines whether or not the steering wheel is cut based on the steering angle and the steering torque, and outputs a true determination result if the cut is present, Furthermore, A control device for a steering device, characterized in that when a true determination result is output in all of the vehicle speed determination unit, steering angle determination unit, steering speed determination unit and steering depth determination unit, the calculation permission determination unit outputs a calculation permission signal that permits the calculation of the correction value.

3. A control device for a steering device according to claim 1, The correction value is a correction gain calculated by the correction value calculation unit. The control device for a steering device is characterized in that the control device further comprises a multiplication unit that multiplies the assist torque by the correction gain.

4. A control device for a steering device according to claim 1, The correction value is the correction torque calculated by the correction value calculation unit. The control device for a steering device is characterized in that the control device further comprises an adder that adds the correction torque to the assist torque.

5. A control device for a steering device according to claim 3 or 4, The control device for a steering device is characterized in that the correction value calculation unit includes a steering torque averaging processing unit that averages the steering torque when steering to the right to generate a first steering torque average value and averages the steering torque when steering to the left to generate a second steering torque average value, and a correction value calculation unit that calculates the correction value based on the first steering torque average value and the second steering torque average value.

6. A control device for a steering device according to claim 5, The averaging of the steering torque during rightward steering is performed only when rightward steering is performed and a calculation permission signal that permits the calculation of the correction value is output. The steering control device is characterized in that the steering torque averaging processing unit measures the cumulative time spent performing the steering torque averaging process during right steering, and when the cumulative time is longer than a predetermined time, it turns on a right steering averaging processing completion flag indicating the completion of the steering torque averaging process during right steering.

7. A control device for a steering device according to claim 6, A control device for a steering device, characterized in that the averaging process of the steering torque when steering to the right and the averaging process of the steering torque when steering to the left are performed by sequential averaging, moving averaging, or averaging using a low-pass filter.

8. A control device for a steering device according to claim 5, The correction value comprises a first correction value for right steering and a second correction value for left steering. The control device for a steering device is characterized in that the correction value calculation unit compares the absolute value of the first average steering torque with the absolute value of the second average steering torque, and when the absolute value of the first average steering torque is greater than the absolute value of the second average steering torque, it gradually increases the first correction value and gradually decreases the second correction value.

9. A control device for a steering device according to claim 8, A steering device control device characterized in that the comparison between the absolute value of the first average steering torque and the absolute value of the second average steering torque is performed by providing a dead zone processing that compares the difference between the two with a predetermined dead zone.

10. A control device for a steering device according to claim 8, When a true determination result is output in all of the vehicle speed determination unit, steering angle determination unit, steering speed determination unit, and steering depth determination unit, the calculation permission determination unit outputs a calculation permission signal that permits the calculation of the correction value. The steering torque averaging processing unit measures the cumulative time spent performing the steering torque averaging process during right steering, and when this cumulative time is longer than a predetermined time, it turns on the right steering averaging processing completion flag to indicate the completion of the steering torque averaging process during right steering, and also measures the cumulative time spent performing the steering torque averaging process during left steering, and when this cumulative time is longer than a predetermined time, it turns on the left steering averaging processing completion flag to indicate the completion of the steering torque averaging process during left steering. A steering device control device characterized in that the gradual increase of the first correction value and the gradual decrease of the second correction value are performed only when the right steering average processing completion flag, the left steering average processing completion flag, and the calculation permission signal are all on.

11. A control device for a steering device according to claim 3 or 4, The control device for a steering device is characterized in that the correction value is determined by comparing the steering torque with a reference torque.

12. A control device for a steering device according to claim 11, The steering torque has steering torque when steering to the right and steering torque when steering to the left. The aforementioned reference torque is a predetermined reference torque. The steering device control unit is characterized in that it compares the steering torque when steering to the right and the steering torque when steering to the left with a predetermined reference torque, and if the correction value calculation unit is greater than the predetermined reference torque, it gradually increases the correction value, and if the correction value is less than the predetermined reference torque, it gradually decreases the correction value, thereby making the steering torque when steering to the right and the steering torque when steering to the left match the predetermined reference torque.

13. A control device for a steering device according to claim 11, A control device for a steering system, characterized in that the reference torque is calculated based on the vehicle speed and the steering angle.

14. A control device for a steering device according to claim 13, A steering device control device characterized in that the reference torque is determined by referring to a map showing the reference torque for the vehicle speed and the steering angle.

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