JP2008273473A - Electric power steering device - Google Patents

Abstract

An electric power steering apparatus capable of reducing a sense of incongruity when a steering wheel is turned back after a failure of a torque sensor is provided.
According to the configuration of the electric power steering apparatus 11 of the present invention, the amount of change θx of the twist amount of the steering shaft 32 exceeds a predetermined reference value K1 before and after the failure of the torque sensor 35. Whether or not the handle 33 is switched back can be determined on the basis of whether or not it has become larger. Then, when it is determined that the steering wheel 33 is switched back, the assist from the electric power steering apparatus 11 is forcibly set to 0 to the damping transient command value Ib given to the assist motor 19 as the assist command value Ix. It is possible to prevent the situation where the application of force is stopped and the assist force hinders the switching back operation. As a result, it is possible to reduce the uncomfortable feeling when switching back after the failure of the torque sensor 35 than before.
[Selection] Figure 2

Description

  The present invention relates to an electric power steering apparatus that drives a motor based on an assist command value determined according to a steering load torque and assists steering of a steering wheel.

Generally, this type of electric power steering apparatus switches to manual steering without assist force when a torque sensor fails. However, when switching to manual steering at the same time as the failure of the torque sensor, the steering load torque increases rapidly due to the disappearance of the assist force, which makes the driver feel uneasy. On the other hand, as a conventional electric power steering apparatus, a control system for normal time for determining the first assist command value according to the steering load torque, and the second control system according to the steering angle regardless of the steering load torque. An emergency control system for determining the assist command value, and switching from the control using the first assist command value to the control using the second assist command value simultaneously with the failure of the torque sensor, The thing of the structure which attenuate | damps a 2nd assist command value gradually and transfers to manual steering is known (for example, refer patent document 1).
JP-A-9-58505 (Claim 1, paragraphs [0004] and [0017])

  By the way, in the electric power steering apparatus described above, the second assist command value is determined based on the steering angle. For example, when the steering wheel is turned back to the right side after being turned to the left side from the neutral point, the steering wheel is Until the vehicle is turned to the right after exceeding the neutral point, the assist torque according to the second assist command value acts in a direction that hinders the steering wheel turning back operation, which may cause the driver to feel uncomfortable.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electric power steering apparatus capable of reducing a sense of incongruity when the steering wheel is turned back after a failure of a torque sensor.

  The electric power steering device (11) according to the first aspect of the present invention, which has been made to achieve the above object, includes a motor (19) based on an assist command value (Ix) determined according to the driving situation of the vehicle (10). ) To output an assist force for assisting the steering of the handle (33) to detect the steering load torque (T1) for the steering of the handle (33). Torque command (35) and normal command value determining means (S3) for determining a normal command value (Ia) as an assist command value (Ix) based on the steering load torque (T1) detected by the torque sensor (35). 100) and when the torque sensor (35) fails, it gradually decreases from the normal command value (Ia) immediately before the failure to 0 over a predetermined decay time (t2). Attenuating transient command value generating means (SS8, 102) for generating a damping transient command value (Ib) to be used as an assist command value (Ix), and a switching back determining means (S6, S6) for determining whether the handle (33) is switched back or not. 103) and forcibly ending means for forcibly setting the damping transient command value (Ib) to 0 when it is determined that the steering wheel (33) is switched back before the damping transient command value (Ib) reaches 0. (S10, 101), and the switchback determination means (S6, 103) is configured such that the amount of change (θx) in the torsional amount of the flexible member (10, 32) that is torsionally deformed when the vehicle (10) turns is torque It is characterized in that when the sensor (35) becomes larger than a predetermined reference value (K1) before and after the failure of the sensor (35), it is determined that the handle (33) is switched back. .

  In the present invention, “the normal command value (Ia) becomes 0” means “the normal command value (Ia) becomes a numerical value for eliminating the assist force”. Accordingly, even if the specific numerical value of the “normal command value (Ia)” is not the specific numerical value “0” because it includes an offset value, for example, the “normal command value (Ia)” Can be said to be “normal command value (Ia) is 0” in the present invention. The same applies to the “damping transient command value (Ib)”.

  According to a second aspect of the present invention, in the electric power steering device (11) according to the first aspect, the steering angle (θ1) of the handle (33) is detected by being attached to the steering shaft (32) rotating together with the handle (33). And a motor rotation position sensor (25) for detecting the output rotation angle (θ2) of the motor (19), and the switchback discrimination means (S6, 103) includes a steering angle sensor (34) and the amount of change (θx) in the twist amount of the steering shaft (32) as the flexible member (32) is detected based on the detection results of the motor rotational position sensor (25).

  According to a third aspect of the present invention, in the electric power steering apparatus (11) according to the first or second aspect, the steering angle (θ1) of the steering wheel (33) is attached to the steering shaft (32) rotating together with the steering wheel (33). The steering angle sensor (34) for detecting the lateral G and the lateral G sensor for detecting the lateral G (G1) applied to the vehicle (10), and the switchback discriminating means (S6, 103) is a torque sensor (35). The amount of change (θy) in the steering angle (θ1) becomes larger than a predetermined first reference value (K2) and the amount of change (Gy) in the lateral G (G1). Is smaller than the predetermined second reference value (K3), the amount of change in the amount of twist of the entire vehicle (10) as the flexible member (10) is when the torque sensor (35) fails. Estimated to be larger than the reference value before and after Having the features the time.

  According to a fourth aspect of the present invention, in the electric power steering apparatus (11) according to any one of the first to third aspects, the steering angle of the handle (33) is attached to the steering shaft (32) rotating together with the handle (33). A steering angle sensor (34) for detecting (θ1) and a rotation speed sensor (36L, 36R) capable of detecting the rotation speed (NL, NR) of the left and right wheels (50) provided in the vehicle (10). The switch-back determination means (S6, 103) indicates that the change amount (θy) of the steering angle (θ1) exceeds a predetermined first reference value (K2) before and after the failure of the torque sensor (35). On the condition that the change amount (Wy) of the rotational speed difference (W1) between the left and right wheels (50) is smaller than a predetermined third reference value (K4). 10) The total amount of twist of the vehicle (10) as Amount change has a characteristic where the estimate that has become larger than the reference value before and after the time of failure of the torque sensor (35).

  According to a fifth aspect of the present invention, in the electric power steering apparatus (11) according to any one of the first to fourth aspects, the steering angle of the steering wheel (33) is attached to the steering shaft (32) rotating together with the steering wheel (33). The steering angle sensor (34) for detecting (θ1) and the yaw rate detector for detecting the yaw rate (R1) of the vehicle (10) are provided, and the switchback discriminating means (S6, 103) is provided by the torque sensor (35). Before and after the failure, the change amount (θy) of the steering angle (θ1) exceeds the predetermined first reference value (K2), and the change amount (Ry) of the yaw rate is determined in advance. On the condition that it is smaller than the third reference value, the amount of change in the twist amount of the entire vehicle (10) as the flexible member (10) exceeds the reference value before and after the failure of the torque sensor (35). It is estimated that Having the features the time.

[Invention of Claim 1]
In a state where the steering wheel is turned and the vehicle is turning, the steering system parts connecting the steering wheel and the wheels (steered wheels) are twisted and deformed, and the entire vehicle is also twisted and deformed. Further, when the steering wheel is turned back, the amount of twisting of the steering system parts and the entire vehicle is reduced. In the electric power steering apparatus according to the first aspect, the amount of change in the amount of twist of the flexible member that twists and deforms when the vehicle turns, such as the above-described steering system parts and the vehicle as a whole, is changed before and after the failure of the torque sensor. Whether or not the steering wheel is turned back can be determined based on whether or not the value exceeds a predetermined reference value. Then, when it is determined that the steering wheel has been turned back, the damping transient command value is forcibly set to 0 to prevent the assist force from interfering with the turning back operation. The uncomfortable feeling at the time of going can be reduced conventionally.

[Invention of claim 2]
According to the configuration of the second aspect, the change amount of the twist amount of the steering shaft as the flexible member is detected based on the detection results of the steering angle sensor and the motor rotation position sensor, and the change amount of the twist amount of the steering shaft is detected. Whether or not the steering wheel is turned back can be determined depending on whether or not the torque sensor exceeds a predetermined reference value before and after the failure of the torque sensor.

[Invention of claim 3]
According to the configuration of the third aspect, before and after the failure of the torque sensor, the change amount of the steering angle becomes larger than the predetermined first reference value, and the change amount of the lateral G is determined in advance. Assuming that the amount of change in the torsion amount of the entire vehicle as the flexible member exceeds the reference value before and after the failure of the torque sensor on the condition that it is smaller than the second reference value, the steering wheel It is possible to determine whether or not to switch back.

[Invention of claim 4]
According to the configuration of the fourth aspect, before and after the failure of the torque sensor, the amount of change in the steering angle becomes larger than a predetermined first reference value, and the change in the rotational speed difference between the left and right wheels is increased. On the condition that the amount is smaller than a predetermined third reference value, the amount of change in the torsion amount of the entire vehicle as the flexible member becomes larger than the reference value before and after the failure of the torque sensor. It can be estimated that the steering wheel has been switched back.

[Invention of claim 5]
According to the configuration of claim 5, before and after the failure of the torque sensor, the change amount of the steering angle becomes larger than a predetermined first reference value, and the change amount of the yaw rate is determined in advance. Assuming that the amount of change in the torsion amount of the entire vehicle as the flexible member exceeds the reference value before and after the failure of the torque sensor on the condition that it is smaller than the fourth reference value, the steering wheel It is possible to determine whether or not to switch back.

[First Embodiment]
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. An electric power steering device 11 according to the present invention is mounted on the vehicle 10 shown in FIG. The electric power steering apparatus 11 includes an assist motor 19 connected to a shaft 16 between steered wheels that is passed between both steered wheels 50 and 50 (wheels). The inter-steering wheel shaft 16 is inserted into the cylindrical housing 18, and both ends thereof are connected to the steered wheels 50 and 50 via tie rods 17 and 17. The cylindrical housing 18 is fixed to the vehicle main body 10H.

  The assist motor 19 includes a stator 20 that is fitted and fixed to the inner surface of the cylindrical housing 18 and a cylindrical rotor 21 that is loosely fitted inside the stator 20, and the inner side of the rotor 21 is between the steered wheels. The shaft 16 penetrates. Then, the ball nut 22 fixed to the inner surface of the rotor 21 and the ball screw portion 23 formed on the outer surface of the inter-steering wheel shaft 16 are screwed together. When the rotor 21 rotates, the ball screw portion 23 moves linearly and turns the steered wheel. 50 and 50 are steered.

  A rack 30 is formed on one end of the inter-steering wheel shaft 16, and a pinion 31 provided at the lower end of the steering shaft 32 is engaged with the rack 30. A handle 33 is attached to an upper end portion of the steering shaft 32, a torque sensor 35 is attached to an intermediate portion of the steering shaft 32, and a steering angle sensor 34 is attached between the torque sensor 35 and the handle 33. ing. The steering angle sensor 34 detects the steering angle θ1 of the handle 33, and the torque sensor 35 detects the steering load torque T1. Further, in the vicinity of the left and right steered wheels 50, 50, rotational speed sensors 36L, 36R capable of separately detecting the rotational speeds of the steered wheels 50, 50 are provided.

  The assist motor 19 is provided with a motor rotation position sensor 25 that can detect the output rotation angle θ2 of the assist motor 19 in order to control the position of the assist motor 19.

  The steering control device 41 included in the electric power steering device 11 executes the steering control program PG1 shown in FIG. 2, for example, to determine the assist command value Ix at a predetermined cycle, and the motor drive circuit shown in FIG. The assist command value Ix is given to 42. Then, the motor drive circuit 42 drives the motor drive current corresponding to the assist command value Ix to flow through the assist motor 19, and as a result, an assist force for assisting the steering of the handle 33 is output from the electric power steering device 11. The

  Specifically, as shown in FIG. 2, when the steering control program PG1 is executed, the steering control device 41 detects each of the rotational speed sensors 36L and 36R, the torque sensor 35, the steering angle sensor 34, and the motor rotational position sensor 25. The results (right front wheel rotation speed NR, left front wheel rotation speed NL, steering load torque T1, steering angle θ1, motor rotation angle θ2) are acquired (S1). Then, it is determined whether or not the torque sensor 35 has failed (S2).

  When the detection result of the torque sensor 35 exceeds a preset upper limit value or when the detection result of the torque sensor 35 is 0 despite the change in the steering angle θ1, the torque sensor 35 It is judged that it has fallen. Further, the execution of the steering control program PG1 constitutes the control system shown in FIG. 7, and the execution of step S2 constitutes the torque sensor failure determination unit 109 and the switch 108 in the control system shown in FIG.

  If the torque sensor 35 has not failed, normal command value determination processing (S3) corresponding to the “normal command value determination means” of the present invention is executed. In this process (S3), as shown in FIG. 3, first, a basic current command value I11 is determined from the steering load torque T1 (S31). Specifically, a basic current command value I11 corresponding to the steering load torque T1 is determined using a preset torque-current command value map mp1 (see FIG. 6). The torque-current command value map mp1 is set so that the basic current command value I11 increases as the steering load torque T1 increases.

  Next, the steering angle θ1 is time-differentiated to obtain the steering angular velocity ω, and the additional current command value I12 corresponding to the steering angular velocity ω is determined (S32). Specifically, the additional current command value I12 corresponding to the steering angular velocity ω is determined using a preset steering angular velocity-current command value map mp2 (see FIG. 6). The steering angular velocity-current command value map mp2 is set so that the additional current command value I12 increases as the steering angular velocity ω increases.

  Next, an average value of the right front wheel rotational speed NR and the left front wheel rotational speed NL is obtained as the vehicle speed V (S33). Then, the gain G1 corresponding to the vehicle speed V is determined (S34). Specifically, a gain G1 corresponding to the vehicle speed V is determined using a preset vehicle speed-gain map mp3 (see FIG. 6). The vehicle speed-gain map mp3 is set so that the gain G1 decreases as the vehicle speed V increases.

  Then, using the basic current command value I11, the additional current command value I12, and the gain G1, the normal current command value Ia (corresponding to the “normal command value” of the present invention) is calculated from the following equation (1) ( S35).

  Ia = G1 (I11-I12) (1)

  The normal command value determination unit 100 of the control system shown in the block diagrams of FIGS. 6 and 7 is configured by executing the normal command value determination process (S3) described above.

  As shown in FIG. 2, in the steering control program PG1, when the normal command value determination process (S3) is exited, a data buffer process (S4) is performed. Here, the steering angle register θs and the motor rotation position register θm are set in a storage area of a memory (not shown) provided in the steering control device 41, and whenever the data buffer process (S4) is performed, The steering angle θ1, which is the latest detection value of the steering angle sensor 34, is stored (stored) in the steering angle register θs, and the motor rotation angle θ2, which is the latest detection value of the motor rotation position sensor 25, is stored in the motor rotation position register θm. Stored (stored).

  Next, the value of the normal current command value Ia determined by the normal command value determination process (S3) is set to the assist command value Ix (S5), and the normal current command value Ia as the assist command value Ix is set to the motor drive circuit 42. (S11) and exit from the steering control program PG1.

  If the torque sensor 35 has failed in step S2, the switchback determination process (S6) corresponding to the “switchback determination means” of the present invention is executed. When the torque sensor 35 fails, a timer (not shown) is started, and a failure elapsed time t1 that is an elapsed time from the time of failure of the torque sensor 35 is measured.

  In the switchback determination process (S6), the change amount θx of the twist amount of the steering shaft 32 before and after the failure of the torque sensor 35 is calculated using the following equation (2) (S20 in FIG. 4).

    θx = (θs−r · θm) − (θ1−r · θ2) (2)

  Here, the motor rotation position sensor 25 is provided to control the position of the assist motor 19 as described above. In the present embodiment, the motor rotation position sensor 25 calculates the twist amount of the steering shaft 32. I also use it. Specifically, when the reduction ratio of the ball screw mechanism including the ball nut 22 and the ball screw portion 23 is “r”, the output rotation angle θ2 detected by the motor rotation position sensor 25 is multiplied by the reduction ratio r. The rotation angle (= r · θ2) at the lower end of the steering shaft 32 can be obtained. From the difference between the steering angle θ1 detected by the steering angle sensor 34 at the upper end of the steering shaft 32 and the rotation angle (= r · θ2) of the lower end of the steering shaft 32 detected by the motor rotation position sensor 25, The twist amount (= θ1−r · θ2) of the steering shaft 32 can be obtained. Similarly, the value of the steering angle register θs that stores the detection value of the steering angle sensor 34 immediately before the failure and the value of the motor rotation position register θm that stores the detection value of the motor rotation position sensor 25 are used. In addition, the twist amount (= θs−r · θm) of the steering shaft 32 immediately before the failure can be obtained. Then, as in the above equation (2), the twist amount of the steering shaft 32 after the failure (= θ1-r · θ2) from the twist amount of the steering shaft 32 immediately before the failure (= θs−r · θm). The difference obtained by subtracting can be obtained as the change amount θx of the twist amount of the steering shaft 32 before and after the failure.

  In addition, by changing the above equation (2) to the following equation (3), the amount of change θx of the twist amount of the steering shaft 32 is the amount of rotation of the upper end portion of the steering shaft 32 before and after the failure. It can also be obtained as a difference between (= θs−θ1) and the rotation amount at the lower end (= r · (θm−θ2)).

    θx = (θs−θ1) −r · (θm−θ2) (3)

  Further, a steering angle sensor 34 is provided in the middle of the steering shaft 32 of the present embodiment, and a torsion bar (not shown) built in the steering angle sensor 34 forms a part of the steering shaft 32. When the steering shaft 32 receives the load torque, the entire steering shaft 32 is twisted to the extent that the increase / decrease in the load torque is reflected in the change amount θx.

  As shown in FIG. 4, in the switchback determination process (S6), it is determined whether or not the flag F1 is “1” after the calculation (S20) of the change amount θx of the twist amount of the steering shaft 32 (S21). Here, the flag F1 is set to “0” in the initial state, and if the flag F1 remains “0” (S21: NO), the process exits from this process (S6). On the other hand, when the flag F1 is “1” (S21: YES), it is determined whether or not the change amount θx of the twist amount of the steering shaft 32 is larger than a preset reference value K1. .

  If the change amount θx of the twist amount of the steering shaft 32 is larger than the reference value K1 (S22: YES), it is determined that the steering wheel 33 has been switched back and the flag F1 is set to “1”. (S23), the process exits (S6). On the other hand, when the change amount θx of the twist amount of the steering shaft 32 is not larger than the reference value K1 (S22: NO), the flag F1 is maintained at “0”, assuming that the steering wheel 33 has not been turned back. This process (S6) is exited.

  Note that the switchback determination unit 103 in the block diagram of FIG. 7 is configured by executing the switchback determination process (S6).

  As shown in FIG. 2, when the switchback determination process (S6) is exited, it is determined whether the determination result is “with switchback (F1 = 1)” or “without switchback” (S7). When the determination result is “no switching back” (S7: NO), a damping transient command value determination process (S8) corresponding to the “damping transient command value generating means” of the present invention is executed. In this process (S8), as shown in FIG. 5, the above-described failure elapsed time t1 is acquired (S71), and it is determined whether or not the failure elapsed time t1 exceeds a preset decay time t2. (S72). Here, when the failure elapsed time t1 exceeds the decay time t2 (S72: YES), the process exits (S8).

  When the failure elapsed time t1 does not exceed the decay time t2 (S72: NO), the normal current command value Ia determined in the normal command value determination process (S3) is acquired (S73).

  Next, the transient coefficient k1 is determined based on the failure elapsed time t1 (S74). Specifically, the transient coefficient k1 corresponding to the failure elapsed time t1 is determined using the failure elapsed time-transient coefficient map mp71 shown in FIG. Here, in the failure elapsed time-transient coefficient map mp71, when the failure elapsed time t1 is "0", the transient coefficient k1 is "1", and when the failure elapsed time t1 is the decay time t2, the transient The coefficient k1 becomes “0”. Further, as the failure elapsed time t1 advances and approaches the decay time t2, the transient coefficient k1 gradually decreases and approaches “0”.

  As shown in FIG. 5, after the transient coefficient k1 is determined, the product of the transient coefficient k1 and the normal current command value Ia is calculated as the attenuated transient command value Ib according to the present invention (S75). Exit from the value determination process (S8).

  Here, FIG. 8B shows a graph in which the failure elapsed time t1 is represented by the X axis (horizontal axis) and the attenuation transient command value Ib is represented by the Y axis (vertical axis). Here, since the attenuation transient command value Ib is the product of the transient coefficient k1 and the normal current command value Ia as described above, the attenuation transient command value Ib is also the failure elapsed time t1 as with the transient coefficient k1. As it progresses, it gradually decreases and approaches “0”.

  Note that, by executing the above-described attenuation transient command value determination process (S8), the attenuation transient command value determination unit 102 in the control system shown in the block diagram of FIG. 7 is configured.

  As shown in FIG. 2, after exiting the damping transient command value determination process (S8), the value of the damping transient command value Ib is set to the assist command value Ix (S9), and the damping transient command value Ib as the assist command value Ix is set. Is applied to the motor drive circuit 42 (S11), and the process exits the steering control program PG1.

  Further, when the determination result by the above-described switchback determination process (S6) is “with switchback (F1 = 1)” (S7: YES), the assist command value Ix is set to “0” (S10), The assist command value Ix (= 0) is given to the motor drive circuit 42 (S11), and the process leaves the steering control program PG1.

  Note that the execution of step S7 described above configures the switch 107 in the block diagram of FIG. 7, and the execution of step S10 configures the assist stop unit 101 in the block diagram. And in this embodiment, these step S10 and the assist stop part 101 are equivalent to the "forced termination means" which concerns on this invention.

  This completes the description of the configuration of the present embodiment. With the above-described configuration, the electric power steering apparatus 11 of the present embodiment normally outputs an assist force according to the normal command value Ia determined based on the steering load torque T1. At this time, the road surface resistance with respect to the steering of the steering wheel 33 is reflected in the steering load torque T1, and the assist force is controlled using the normal command value Ia based on the steering load torque T1, so the steering load torque T1 received by the driver is Stabilize. Further, since the normal current command value Ia is multiplied by a gain G1 that decreases as the vehicle speed V increases, the normal current command value Ia decreases and the handle 33 becomes heavy during high speed traveling, and the normal current command value during low speed traveling. The value Ia increases and the handle 33 becomes lighter. As a result, the sudden handle is prevented during high-speed travel, and garage entry or the like during low-speed travel is facilitated.

  Now, when the torque sensor 35 fails, the assist force cannot be controlled based on the steering load torque T1. Therefore, in the electric power steering apparatus 11 of the present embodiment, the assist force at the time of failure of the torque sensor 35 is gradually attenuated from the time of failure until the decay time t2 elapses.

  By the way, in a state where the handle 33 is turned and the vehicle 10 is turning, the steering shaft 32 is twisted and deformed. More specifically, a load torque from the handle 33 applied to the upper end portion of the steering shaft 32 and a load due to road resistance applied to the lower end portion of the steering shaft 32 and reduced by the assist force of the electric power steering device 11. Torsional deformation due to torque. When the handle 33 is cut back, the load torque applied to the steering shaft 32 on the handle 33 side is reversed, so that the twist amount of the steering shaft 32 changes drastically. That is, the change amount θx of the twist amount of the steering shaft 32 becomes relatively large.

In such a case, according to the configuration of the electric power steering apparatus 11 of the present embodiment, the amount of change θx of the twist amount of the steering shaft 32 has a predetermined reference value K1 before and after the failure of the torque sensor 35. Whether or not the handle 33 is switched back can be determined based on whether or not it has become larger. Then, when it is determined that the steering wheel 33 is switched back, the assist from the electric power steering apparatus 11 is forcibly set to 0 to the damping transient command value Ib given to the assist motor 19 as the assist command value Ix. It is possible to prevent the situation where the application of force is stopped and the assist force hinders the switching back operation. As a result, it is possible to reduce the uncomfortable feeling when switching back after the failure of the torque sensor 35 than before.
[Second Embodiment]

  The present embodiment differs from the first embodiment in the configuration of the steering control program PG1, particularly in the configuration of the switchback determination process (S6, see FIG. 9). Hereinafter, the configuration of the present embodiment will be described with reference to FIGS. 2 and 9.

  When the steering control program PG1 (see FIG. 2) of the present embodiment is executed, the detection results of the lateral G sensor (not shown) provided in the vehicle 10 are also taken together with the detection results of the torque sensor 35, the steering angle sensor 34, and the like. (S1). In the data buffer process (S4), the steering angle θ1 which is the latest detected value of the steering angle sensor 34 is stored (stored) in the steering angle register θs, and the latest detected value G1 of the lateral G sensor is Stored (stored) in the G register Gs.

  When the switchback determination process (S6) is executed, as shown in FIG. 9, the value of the steering angle register θs, which is the detected value of the steering angle sensor 34 immediately before the failure, and the current value of the steering angle sensor 34 are displayed. The steering angle change amount θy (= θs−θ1) before and after the failure is obtained from the detected steering angle θ1. Further, from the value of the lateral G register Gs, which is the detection value of the lateral G sensor immediately before the failure, and the current detection value G1 of the lateral G sensor, the change amount Gy of the lateral G before and after the failure is obtained. Desired.

  If the flag F1 for determining whether or not to switch back is not “1” (S21: NO), the steering angle change amount θy is larger than the first reference value K2 (S103: YES). Further, it is determined that the handle 33 has been turned back on condition that the lateral G change amount Gy is smaller than the second reference value K3 (S104: YES), and “1” is set to the flag F1 ( S23), this process (S6) is exited. In other cases (NO in any one of S103 and S104), the flag F1 is maintained at “0” and the process exits (S6).

  By the way, in a state in which the vehicle 10 is turning with the handle 33 turned off, the steering system parts such as the steering shaft 32 described above are twisted and deformed, and the entire vehicle 10 is also twisted and deformed. Further, when the handle 33 is cut back, the amount of twist of the entire vehicle 10 is also drastically reduced. In the present embodiment, the entire vehicle 10 is regarded as a flexible member, and one end of the flexible member is the steering shaft 32, and the other end is the vehicle main body 10H other than the steering shaft 32 (see FIG. 1). I think. Further, the rotation angle (that is, the steering angle) of the steering shaft 32 and the lateral G related to the vehicle main body 10H are used as physical quantities that change as the vehicle 10 turns. Of the physical quantity of the steering shaft 32 at one end of the vehicle 10 as a flexible member and the physical quantity of the vehicle body 10H at the other end, only the physical quantity of the steering shaft 32 is before and after the failure of the torque sensor 35. In the case of a large change, the entire vehicle 10 is estimated that the amount of change in twist exceeds the reference value.

  That is, in the present embodiment, the entire vehicle 10 is provided on the condition that the steering angle change amount θy is greater than the first reference value K2 and the lateral G change amount Gy is smaller than the second reference value K3. It is estimated that the amount of change in the torsion amount has increased beyond the reference value before and after the failure of the torque sensor 35, and it is determined whether or not the handle 33 is switched back. Also with this configuration, it is possible to determine whether or not the handle 33 is switched back. When the handle 33 is switched back, the damping transient command value Ib is forcibly set to 0, so that the torque sensor 35 A sense of incongruity when switching back after failure can be reduced.

[Third Embodiment]
The present embodiment differs from the first embodiment in the configuration of the steering control program PG1, particularly in the configuration of the switchback determination process (S6, see FIG. 10). Hereinafter, the configuration of the present embodiment will be described with reference to FIGS. 2 and 10.

  In the present embodiment, in the data buffer process (S4) (see FIG. 2), the latest steering angle θ1 is stored (stored) in the steering angle register θs, and the rotational speed difference W1 between the left and right steered wheels 50, 50 is stored. (= NR-NL) is obtained, and the latest value of the rotational speed difference W1 is stored (stored) in the rotational speed difference register Ws.

  In the switchback determination process (S6), as shown in FIG. 10, the change amount θy (= θs−θ1) of the steering angle is obtained and the value of the rotational speed difference register Ws is obtained as in the second embodiment. Then, a change amount Wy (= Ws−W1) of the rotational speed difference between the left and right steered wheels 50, 50 before and after the failure is obtained from the current rotational speed difference W1 (S111). When the flag F1 for determining whether or not to switch back is not “1” (S21: NO), the steering angle change amount θy is larger than the first reference value K2 (S103: YES). In addition, it is determined that the handle 33 has been turned back on condition that the change amount Wy of the rotational speed difference is smaller than the third reference value K4 (S114: YES), and “1” is set to the flag F1. (S23), this process (S6) is exited. In other cases (NO in any of S103 and S114), the flag F1 is maintained at “0” and the process exits (S6).

Thus, in the present embodiment, the entire vehicle 10 is regarded as a flexible member, and one end portion of the flexible member is the steering shaft 32, and the other end portion is regarded as the steered wheels 50 and 50 (see FIG. 1). ing. Further, the rotation angle of the steering shaft 32 (that is, the steering angle) and the difference between the inner and outer wheels of the left and right steered wheels 50 and 50 are used as physical quantities that change as the vehicle 10 turns. Then, before and after the failure of the torque sensor 35, the change amount θy of the steering angle increases beyond the first reference value K2, and the change amount Wy of the rotational speed difference between the left and right steered wheels 50, 50 is On the condition that it is smaller than the third reference value K4, it is estimated that the amount of change in the torsion amount of the entire vehicle 10 exceeds the reference value before and after the failure of the torque sensor 35, and the steering wheel 33 is switched back. The presence or absence is determined.
[Fourth Embodiment]

  The present embodiment differs from the first embodiment in the configuration of the steering control program PG1, particularly in the configuration of the switchback determination process (S6, see FIG. 11). Hereinafter, the configuration of the present embodiment will be described with reference to FIGS. 2 and 11.

  When the steering control program PG1 (see FIG. 2) of the present embodiment is executed, the yaw rate R1 of the vehicle 10 is captured together with the detection results of the torque sensor 35, the steering angle sensor 34, and the like. In the data buffer process (S4), the latest steering angle θ1 is stored (stored) in the steering angle register θs, and the latest yaw rate R1 is stored (stored) in the yaw rate register Rs.

  When the switchback determination process (S6) is executed, as shown in FIG. 11, the change amount θy (= θs−θ1) of the steering angle before and after the failure occurs as in the second embodiment. In addition to being obtained, a change amount Ry (= Rs−R1) of the yaw rate before and after the failure is obtained (S121). When the flag F1 for determining whether or not to switch back is not “1” (S21: NO), the steering angle change amount θy is larger than the first reference value K2 (S103: YES), and Then, it is determined that the handle 33 has been turned back on condition that the change amount Ry of the yaw rate is smaller than the fourth reference value K5 (S124: YES), and “1” is set to the flag F1 (S23). This process (S6) is exited. In other cases (NO in any of S103 and S124), the flag F1 is maintained at “0” and the process exits (S6).

  Thus, in the present embodiment, the entire vehicle 10 is regarded as a flexible member, and one end portion of the flexible member is the steering shaft 32, and the other end portion is regarded as the vehicle body 10H (see FIG. 1). . Further, the rotation angle (that is, the steering angle) of the steering shaft 32 and the yaw rate are used as physical quantities that change as the vehicle 10 turns. Then, before and after the failure of the torque sensor 35, the change amount θy of the steering angle exceeds the first reference value K2, and the change amount Ry of the yaw rate is smaller than the fourth reference value K5. Thus, it is estimated that the amount of change in the amount of twist of the entire vehicle 10 has increased beyond the reference value before and after the failure of the torque sensor 35, and it is determined whether or not the steering wheel 33 is switched back.

  The present invention is not limited to the above-described embodiment, and can be implemented with various modifications other than those described above without departing from the scope of the invention.

The conceptual diagram of the vehicle carrying the electric power steering device which concerns on one Embodiment of this invention. Steering control program flowchart Normal command value decision process flowchart Flowchart of switchback determination processing Flow chart of damping transient command value determination process Block diagram of normal command value determination unit Block diagram of a control system configured by executing a steering control program (A) Failure elapsed time-conceptual diagram of transient coefficient, (B) graph showing transition of damping transient command value Flowchart of switchback determination processing in the second embodiment Flowchart of switchback determination processing in the third embodiment Flowchart of switchback determination processing in the fourth embodiment

Explanation of symbols

10 Vehicle (flexible member)
10H Vehicle body 11 Electric power steering device 16 Steering shaft 19 Assist motor 25 Motor rotation position sensor 32 Steering shaft (flexible member)
33 Steering wheel 34 Steering angle sensor 35 Torque sensor 36L, 36R Rotational speed sensor 50 Steering wheel 100 Normal command value determination unit 101 Assist stop unit 102 Decay transient command value determination unit 103 Determination unit 107 Switch 108 Switch 109 Torque sensor failure determination unit Ia Normal current command value (normal command value)
Ib Decay transient command value Ix Assist command value K1 Reference value K2 First reference value K3 Second reference value K4 Third reference value K5 Fourth reference value PG1 Steering control program

Claims (5)

An electric power steering device that drives a motor based on an assist command value determined according to a driving situation of a vehicle and outputs an assist force for assisting steering of a steering wheel,
A torque sensor for detecting a steering load torque for steering the steering wheel;
Normal command value determining means for determining a normal command value as the assist command value based on the steering load torque detected by the torque sensor;
Attenuation that generates, as the assist command value, a damping transient command value that gradually decays from the normal command value immediately before the failure to zero over a predetermined decay time when the torque sensor fails. A transient command value generating means;
Switchback determining means for determining whether or not the handle is switched back;
Forcibly terminating means for forcibly setting the damping transient command value to 0 when it is determined that the steering wheel is turned back before the damping transient command value reaches 0,
The switch-back determining means is configured such that when the amount of change in the amount of twist of the flexible member that twists and deforms when the vehicle turns exceeds a predetermined reference value before and after the failure of the torque sensor. The electric power steering apparatus is configured to determine that the steering wheel is turned back. A steering angle sensor that is attached to a steering shaft that rotates together with the handle and detects a steering angle of the handle, and a motor rotation position sensor for detecting an output rotation angle of the motor,
The switchback determination means detects a change amount of a twist amount of the steering shaft as the flexible member based on detection results of the steering angle sensor and the motor rotational position sensor. The electric power steering apparatus as described. A steering angle sensor that is attached to a steering shaft that rotates with the handle and detects the steering angle of the handle;
A lateral G sensor for detecting the lateral G applied to the vehicle,
The switchback determining means has a change amount of the steering angle that exceeds a predetermined first reference value before and after the failure of the torque sensor, and a change amount of the lateral G is determined in advance. The amount of change in the torsion amount of the entire vehicle as the flexible member is larger than the reference value before and after the failure of the torque sensor, on condition that the second reference value is smaller than the second reference value. The electric power steering apparatus according to claim 1, wherein the electric power steering apparatus is estimated. A steering angle sensor that is attached to a steering shaft that rotates with the handle and detects the steering angle of the handle;
A rotational speed sensor capable of detecting rotational speeds of left and right wheels provided in the vehicle,
The switch-back determination means increases the amount of change in the steering angle before and after the failure of the torque sensor exceeding a predetermined first reference value, and detects the difference in rotational speed between the left and right wheels. On the condition that the amount of change is smaller than a predetermined third reference value, the amount of change in the torsion amount of the entire vehicle as the flexible member is the reference value before and after the failure of the torque sensor. The electric power steering apparatus according to any one of claims 1 to 3, wherein the electric power steering apparatus is estimated to be larger than a value. A steering angle sensor that is attached to a steering shaft that rotates with the handle and detects the steering angle of the handle;
A yaw rate detector for detecting the yaw rate of the vehicle,
The switchback determining means has a change amount of the steering angle that exceeds a predetermined first reference value before and after the failure of the torque sensor, and a change amount of the yaw rate is determined in advance. The amount of change in the torsion amount of the entire vehicle as the flexible member becomes larger than the reference value before and after the failure of the torque sensor, on condition that it is smaller than the fourth reference value. The electric power steering apparatus according to any one of claims 1 to 4, wherein the electric power steering apparatus is estimated.

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