JP3884369B2 - Steering control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a steering control device that controls a steering reaction force of a vehicle-mounted steer-by-wire system.
[0002]
[Prior art]
  For example, as a steering control device for controlling the steering reaction force of a conventional steer-by-wire system, a device described in the following Patent Document 1 or a device described in the following Patent Document 2 is generally used. Widely known.
  In these conventional apparatuses, a steering torque sensor for detecting a steering torque T accompanying a steering operation of a driver is provided, and a reaction force torque (steering reaction force T for giving an appropriate feel to the steering wheel) is provided._R) Is used to determine the output value.
[0003]
[Patent Document 1]
        JP 2001-334947 A (page 4-5, FIG. 1)
[Patent Document 2]
        JP-A-5-105100 (Page 2-4, Figure 1-3)
[0004]
[Problems to be solved by the invention]
  However, the conventional steer-by-wire system as described above has the following problems because it must be switched to the manual steering mechanism when the torque sensor fails.
(Problem 1)
  When switching to the manual steering mechanism when the torque sensor breaks down, the steering feeling suddenly increases, so the driver feels confused and uncomfortable.
[0005]
  The present invention has been made to solve the above-described problems, and its object is to enable a relatively smooth switching of the steering method or the control method of the steering control even when the torque sensor fails. Is to do.
[0006]
[Means for Solving the Problem, Action, and Effect of the Invention]
  In order to solve the above problems, the following means are effective.
  That is, the first means of the present invention is the steering reaction force T that the steering actuator should apply to the steering wheel._RThe steering mechanism that controls the steering wheel and the steering mechanism that controls the steering displacement amount x related to the actual steering angle of the steered wheels are mechanically separated. In a steer-by-wire system that is configured alternatively, the steering mechanism includes a steering torque sensor that detects a steering torque T applied by the driver to the steering wheel, and a road surface reaction.By forceA steering reaction force calculating means for calculating a steering reaction force F acting on the steering mechanism;Based on the steering torque T detected by the steering torque sensor and the turning reaction force F calculated by the turning reaction force calculation means, the steering reaction force T _R Steering reaction force calculation means for calculating the steering reaction force calculation MeansWhen an abnormality of the steering torque sensor is detected, the steering reaction force T_RAnd a steering torque related value separating means for stopping the input or use of the steering torque T detected by the steering torque sensor..
[0007]
  According to such a configuration, when an abnormality of the steering torque sensor is detected, the steering reaction force T_RIn this calculation, the input or use of the detected value of the steering torque T, which is treated as if the steering torque sensor was correctly detected, is stopped, so that an unreasonable steering reaction force on the steering wheel is extremely inappropriate. No fear of being granted.
  That is, according to the first means described above, the driver can continue the steering operation by continuing the steering control without necessarily switching to the manual steering mechanism. Can be solved.
[0008]
  However, the aboveConstitutionWhen using, the following problem is derived.
(Problem 2)
  If the detected value T of the steering torque applied to the steering wheel by the driver is assumed to be zero when the torque sensor breaks down, the steering feeling suddenly becomes light, and the driver feels confused and uncomfortable.
[0009]
  BookInventionFirstMeasures against this problem 2Added moreIs.
  That isThe steering reaction force calculation means isFirst gain changing means for changing the coefficient value of the steering reaction force F or the coefficient value of the related value of the steering reaction force F when an abnormality of the steering torque sensor is detected is provided.The
[0010]
  Even when the detected value T of the steering torque is assumed to be zero by such correction of the coefficient value (gain), a desired steering reaction force T to be output from the steering actuator is obtained._RCan be roughly corrected (adjusted). For this reason, the steering reaction force F (or its estimated value F)_hThe influence on the steering feeling of) is overwhelming or extremely dominant.
[0011]
  Also,SecondMeans aboveFirst meansInSteering reaction force calculation meansSteering wheel rotation speed ω_HBased on the inertia torque T related to the moment of inertia of the steering mechanism_KThe steering reaction force T_RInertia compensation means set as one of the terms constituting the inertia torque T when the steering torque sensor abnormality is detected_KCoefficient value or inertia torque T_KAnd a second gain changing means for changing the coefficient value of the related value.
[0012]
  According to such a configuration, a simulation related to the inertia of the steering mechanism or the steering mechanism that has been conventionally processed mainly using the steering torque T or the like during normal operation of the torque sensor (ie, output of inertia torque). For example, the rotational speed ω of the steering wheel_HIt becomes possible to carry out based on the above.
  As a result, it is possible to avoid the steering feeling from becoming extremely light, and thus it is possible to reduce the uncomfortable feeling of the problem.
[0013]
  Also,ThirdMeans aboveFirst or second meansInSteering reaction force calculation meansSteering wheel rotation speed ω_HFriction torque T related to the internal friction of the steering mechanism or the steering mechanism based on_DThe steering reaction force T_RAnd friction compensation means set as one of the terms constituting the friction torque T when the abnormality of the steering torque sensor is detected_DCoefficient value or friction torque T_DAnd a third gain changing means for changing the coefficient value of the related value.
[0014]
  According to such a configuration, a simulation related to the frictional force in the steering mechanism or the steering mechanism that has been conventionally processed mainly using the steering torque T or the like during normal operation of the torque sensor (ie, friction torque). Output), for example, the rotational speed of the steering wheel ω_HIt becomes possible to carry out based on the above.
  As a result, it is possible to avoid the steering feeling from becoming extremely light, and thus it is possible to reduce the uncomfortable feeling of the problem.
[0015]
  Also,4thMeans above1st to 3rdWhen the steering reaction force calculation means of any one of the means detects an abnormality in the steering reaction force phase correction means for correcting the phase of the steering reaction force F and the steering torque sensor, the steering reaction force F is detected. And a phase correction amount changing means for changing the correction amount for the phase.
[0016]
  If the steering torque T cannot be detected, a feedback loop related to the steering torque cannot be formed, and therefore the steering reaction force T_RThe responsiveness when generating and outputting is deteriorated. In order to reduce this influence, a measure for increasing (or not reducing) the responsiveness of the open control system related to the steering reaction force F is effective.
  According to the fifth means, the phase of the steering reaction force F can be advanced (or not delayed) by changing the correction amount for the phase of the steering reaction force F. It is possible to reduce the deterioration of responsiveness to the steering operation of the mechanism.
[0017]
  Also,5thMeans above1st to 4thThe steering reaction force calculation means of any one of the means is provided with a steering reaction force sensor for measuring the steering reaction force F.
  According to such a configuration, since the turning reaction force can be directly measured from the turning reaction force sensor, the turning reaction force F can be obtained with higher accuracy and reliability.
  Further, according to such a configuration, it is not necessary to estimate the turning reaction force F by an advanced or complicated estimation process using a known observer or the like. Processing program development man-hours can be reduced.
  Further, according to the above configuration, the CPU overhead when using the control device can be reduced as compared with the case where the observer is configured by a program.
[0018]
  Also,6thMeans above1st to 4thIn the turning reaction force calculation means of any one means, the measured value I of the turning current flowing in the turning actuator of the turning mechanism_a, Command value I_nOr related value u_rA steering reaction force estimation means for estimating the steering reaction force F is provided.
[0019]
  Where the related value u_rMay be arbitrary as long as it is a control amount for the steering actuator. For example, a command voltage in the drive circuit of the steering motor, a duty value in PWM control, or the like may be used. Of course, the value of the current (steering current) flowing in the steering motor, the command value thereof, or the like may be used.
[0020]
  According to the above configuration, since the steering reaction force F is estimated, the steering control device can be configured without necessarily having the steering reaction force sensor. An advantageous control device can be constructed.
  In addition, according to the above configuration, there is no need to examine in detail the connection specifications (standards), measurement accuracy, price, heat resistance, vibration resistance, durability, size, shape, weight, etc. of the steering reaction force sensor. Moreover, there is no fear that these conditions become a design bottleneck.
[0021]
  Also,7thMeans above6thIn the turning reaction force estimation means of the means, “measured value I of the turning current flowing in the turning actuator of the turning mechanism”_a, Command value I_nOr related value u_r"," Steering displacement amount x, its command value x_nOr a related value related thereto ”is to provide a disturbance observer for estimating the turning reaction force F described above.
[0022]
  According to such a configuration, the above-described steering reaction force F can be estimated with relatively high accuracy. Therefore, both the estimation accuracy of the steering reaction force F and the component costs of the device are relatively reasonable. A well-balanced control device can be configured.
  By the above means of the present invention, the above-mentioned problem can be effectively or rationally solved.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, the present invention will be described based on specific examples. However, the present invention is not limited to the following examples.
[First embodiment]
  FIG. 1 is a system configuration diagram of a steering control device 100 according to the present embodiment. This steering control device 100 electrically controls a steering mechanism having a steering wheel (handle) 1 operated by a driver, a steering mechanism that steers the steered wheels 16, and interlock control between these steering mechanisms and the steering mechanism. It consists of a control device (computer) 8 or the like that performs automatically.
[0024]
  The steering mechanism includes a steering actuator (reaction force motor 5) that generates a steering reaction force. The reaction force motor drive circuit 6 has a control amount (T_R) To drive the reaction force motor 5. An output shaft of the reaction force motor 5 is connected to a steering shaft (steering shaft) 2 via a speed reducer, and the steering shaft 2 is connected to a steering handle 1.
[0025]
  The steering shaft 2 is provided with a steering angle sensor 3 that detects a steering angle θ that is a rotation angle of the shaft, and a steering torque sensor 4 that detects a steering torque T applied to the steering shaft 2. However, instead of the steering angle sensor 3, a reaction force motor angle sensor that detects the rotation angle of the reaction force motor may be provided, and the steering angle θ may be estimated from the rotation angle of the reaction force motor. In this case, the rotation angle of the reaction force motor may be converted into the steering angle θ based only on the reduction ratio, or the steering angle θ may be corrected in consideration of the torsional rigidity of the steering shaft.
[0026]
  On the other hand, the steering mechanism includes a steering actuator (steering motor 11) that steers the steering shaft 13. The steered motor drive circuit 9 has a control amount (u_r) To drive the steered motor 11. The converter (speed reducer 12) that converts the rotational motion of the steered motor 11 into a linear motion can be constituted by, for example, a ball screw mechanism or the like. Both ends of the steered shaft 13 are connected to the steered wheels 16 via tie rods 14 and knuckle arms 15.
[0027]
  The steered shaft 13 detects a steered displacement amount sensor 10 that detects the steered displacement amount x of the shaft and a steered reaction force F that is applied to the steered shaft 13 from the outside (the steered wheel 16 side) (not shown). Although a steering reaction force sensor may be provided, in the present embodiment, a configuration example in which the latter steering reaction force sensor is replaced with a disturbance observer will be illustrated in detail.
[0028]
  Further, instead of the turning displacement sensor 10, a turning motor angle sensor for detecting the turning angle of the turning motor may be provided, and the turning displacement amount x may be estimated from the turning angle of the turning motor. In this case, it may be converted only by the reduction ratio, or may be corrected in consideration of the axial rigidity of the steered shaft 13.
[0029]
  The detection results (steering angle θ, steering torque T, steering displacement amount x, vehicle speed V) of the steering angle sensor 3, steering torque sensor 4, steering displacement sensor 10, and vehicle speed sensor 7 are input to the control device 8. Based on these detection results, control signals (control force T of reaction force motor T) are sent to each drive circuit (6, 9) so that reaction force motor 5 and steered motor 11 output a predetermined drive force._R, Steering motor control amount u_r) Is output.
[0030]
  FIG. 2 is a control block diagram illustrating a logical main configuration related to the steering reaction force generation method of the control device 8 of the steering control device 100.
  Control signal to reaction force motor drive circuit 6 (control amount T of reaction force motor_R) Is calculated by the control amount calculator 85 of the reaction force motor.
[0031]
  On the other hand, a control signal to the steered motor drive circuit 9 (control amount u of steered motor u_r) Is calculated by the position controller 82. This position controller 82 is a target value x of the steering displacement amount calculated by the target value calculator 81._nBased on the steering displacement amount x detected by the steering displacement amount sensor 10, the control amount u of the above-described steering motor is obtained by well-known PD control (proportional / integral control)._rIs calculated. Of course, based on other known control theories such as PID control (proportional / integral / derivative control), for example, the control amount u of the above-described steering motor_rMay be calculated.
[0032]
  The turning reaction force estimator 88 includes a turning displacement amount x and a turning motor control amount u._rEstimated value F of steering reaction force F based on_hIs calculated.
  The steered reaction force estimator 88 can be replaced with a steered reaction force sensor that directly detects the steered reaction force F. In the following first embodiment, the steered reaction force estimator 88 is used. As for the steering control device (100) having 88, "I. Operation at normal time" centering on the description of the main part and "II. Operation at abnormal time" which develops detailed description directly related to the characteristic part of the present invention. It will be described in two parts.
[0033]
I. Normal operation
  Hereinafter, the normal operation of the control device 8 (the normal operation of the steering torque sensor 4) will be described.
  FIG. 3 is a flowchart illustrating an outline of a control procedure executed by the control device 8 of the steering control device 100. This control procedure is means for implementing the steering control of FIG.
[0034]
  In the control procedure of FIG. 3, first, the system is initialized in step 510. This initialization is centered on processes such as initialization of control variables. These specific contents will be illustrated fragmentarily later.
[0035]
  In step 520, detection results (steering angle θ, steering torque T, steering displacement x, vehicle speed V) of the steering angle sensor 3, steering torque sensor 4, steering displacement sensor 10, and vehicle speed sensor 7 are input.
  In step 530, a subroutine (FIG. 4) for performing the steering motor control is called and executed. This subroutine is a subroutine that embodies the target value calculator 81 and the position controller 82 of FIG.
[0036]
  In step 540, the steering reaction force is obtained. This steering reaction force may be obtained from a signal directly detected by the steering reaction force sensor. In this embodiment, the steering reaction force estimator 88 and the steering displacement amount x and the steering reaction force are detected. Control amount u of motor_rEstimated value F of steering reaction force F based on_hThe procedure for calculating the value will be illustrated in detail.
  In step 550, a subroutine (FIG. 8) for performing reaction force motor control is called and executed. This subroutine is a subroutine that embodies the control amount calculator 85 of the reaction force motor of FIG.
[0037]
  In step 560, in order to execute the processing after step 520 periodically (one example: 0.5 ms cycle), a timer interrupt reservation setting process or the like is performed, and a transition to a timer interrupt wait state is made.
  Next, the subroutine (FIG. 4) for performing the steering motor control called as a subroutine in step 530 will be described in detail.
[0038]
1. Steering axis control procedure
  FIG. 4 is a flowchart illustrating a control procedure executed by the steered motor control unit (that is, the target value calculator 81 and the position controller 82) implemented by the control device 8 of FIGS. 1 and 2. .
[0039]
  Target value x of steering displacement x from steering angle θ_nIs determined by equation (1). Transmission ratio G_rAlthough a constant may be used, for example, maps (a) and (b) as shown in FIG._r= G_r1× g_r2It may be determined in a format such as For example, according to such setting according to the vehicle speed, a desired steering gear ratio variable means can be realized.
[0040]
[Expression 1]
  x_n= G_rθ (1)
  For example, in this way, the calculation processing (step 620 and step 640) of the target value calculator 81 can be executed.
[0041]
  Deviation (x_n-X) and its time derivative d (x_n-X) Control amount u of the steered motor 11 based on / dt_rIs determined by equation (2), and the steering displacement x is the target value x_nDrive control is performed so as to follow. Gain factor G_px, G_dxIs a constant.
[Expression 2]
  u_r= G_px(X_n-X) + G_dx・ D (x_n-X) / dt (2)
  For example, in this way, the calculation process (steps 660 and 680) of the position controller 82 can be executed.
[0042]
  Hereinafter, the estimated value F of the steering reaction force is calculated by a calculation method related to the disturbance observer._hThe procedure for calculating the value (step 540 in FIG. 3) is specifically illustrated with reference to FIGS.
[0043]
2. Steering reaction force estimation procedure
  The equation of motion of the turning mechanism is described by equation (3). Here, M is an effective mass in the steering displacement direction of the steering mechanism determined from the rack shaft mass, the inertia of the motor, and the like.
[Equation 3]
  M ・ d²x / dt²= U_r-F-F≡d (3)
[0044]
  However, said f is the frictional force which arises inside steering mechanisms, such as the steering motor 11 and a converter (speed reducer 12). The frictional force f may be obtained as a function y of x and v, for example. The function y may be obtained as a mathematical expression related to x, v, etc., or may be obtained from a map (table data) that approximates the function y and a predetermined interpolation process.
[Expression 4]
  f = y (x, v) (4)
  However, the lower case variable v is the turning speed of the turning shaft 13 defined by the following equation (5).
[Equation 5]
  v = dx / dt (5)
[0045]
  Here, if the force d in Expression (3) is regarded as a disturbance in the disturbance observer, a disturbance observer expressed in the form of Expression (a) in FIG. 7 can be configured. However, hereinafter, the matrix G is an observer gain (a constant matrix of 3 rows and 2 columns), and F_h, X_h, V_h, D_hRepresent the estimated values of F, x, v, and d, respectively.
[0046]
  The state quantity of the observer at time k is x₀(k) (column vector of 3 rows and 1 column). At this time, if the observer gain G is determined by the pole placement method and the sampling time is discretized at an appropriate time interval (for example, about 0.5 ms), the above state quantity x₀(k) can be calculated sequentially in the form of equation (b) in FIG. Therefore, the estimated value d of the above force d_hCan be sequentially calculated in the form of equation (c) in FIG.
  Here, k is a time parameter (integer variable) representing the sampling time, matrices A and C are constant matrices of 3 rows and 3 columns, respectively, and matrices B and D are constant matrices of 3 rows and 2 columns, respectively. Also, the state quantity x₀Initial value x of (k)₀(0) may be a 0 vector. Also, the initial value v (0) of the steering speed v may be zero.
[0047]
  Therefore, the estimated value d of the above force d_hUsing the estimated value F of the steering reaction force F_hCan be sequentially obtained by the following equation (6).
[Formula 6]
  F_h(k) = u_r(k) -f (k) -d_h(k) ... (6)
[0048]
  For example, in this way, instead of the detected value F of the turning reaction force sensor, the estimated value F of the turning reaction force_hIs used to control the reaction amount T of the reaction force motor._RSince the steering reaction force sensor becomes unnecessary, the cost can be reduced. Further, since vibration due to noise of the turning reaction force sensor does not occur, a smooth steering feeling can be obtained.
[0049]
  Based on these theories, the turning reaction force estimator 88 (that is, step 540 in FIG. 3) according to the present invention in FIG. 2 can be configured.
  FIG. 6 is a flowchart illustrating a control procedure executed by the turning reaction force estimator 88 embodied by the control device 8.
[0050]
  In this control procedure, first, in step 910, the value of the moving speed v (k) of the steered shaft is obtained by the above equation (5).
  Next, in step 920, d is calculated according to equation (c) in FIG._hFind the value of (k).
  In step 930, F is calculated according to the above equation (6)._hFind the value of (k).
  In step 940, this F_hIs substituted into a variable F representing the steering reaction force. As a result, the value of the steering reaction force F can be referred to in the control amount calculator 85 of the reaction force motor.
[0051]
  In step 950 and step 960, preparation for calculation processing in the next control cycle is made. That is, in step 950, according to the equation (b) in FIG.₀The value of (k + 1) is calculated and stored in a predetermined storage area.
  In step 960, the time parameter k is updated.
[0052]
  Note that the processing in step 960 may be executed in step 560 described above. K = 0, x₀It is assumed that initialization processing of various used variables such as (0) = 0 and v (0) = 0 is executed in step 510 described above.
[0053]
  Next, the reaction motor control called as a subroutine in step 550 of FIG. 3 will be described in detail.
[0054]
3. Steering shaft (reaction force motor) control procedure
  Based on the steering torque T and its time derivative dT / dt, and the turning reaction force F and its time derivative dF / dt, the control amount T of the reaction force motor 5 is controlled._RMay be determined according to the following equation (7), but in this embodiment, the control amount T of the reaction force motor 5 is calculated by the following equation (8)._RAn example of determining Where the gain coefficient G_pt, G_dt, G_pf, G_dfIs an appropriate constant, and the above-mentioned estimated value F is included in the steering reaction force F in the third and fourth terms on the right side of each of the equations (7) and (8)._hShall be substituted.
[Expression 7]
  T_R= G_ptT + G_dt・ DT / dt-G_pfFG_dfDF / dt (7)
[Equation 8]
  T_R= G_ptT + G_dtDT / dt-f_pf(F) -G_dfDF / dt (8)
[0055]
  The third term and the fourth term of each of the above formulas (7) and (8) are control amounts acting in the direction opposite to the direction in which the steering torque is applied. A steering reaction force corresponding to a turning reaction force such as self-aligning torque is generated by the third term. Further, when the steering reaction force is quickly generated with respect to the turning reaction force by the fourth term, vibration caused by the turning reaction force is suppressed. Therefore, the steering reaction force (road surface information) can be transmitted to the driver without a sense of incongruity, and a smooth steering feeling can be obtained.
[0056]
  On the other hand, the first term and the second term are control amounts for rotating the steering shaft in the direction in which the steering torque is applied. The first term suppresses the steering reaction force due to the friction of the speed reducer, and the second term suppresses the vibration due to the cogging of the reaction force motor. Therefore, the steering reaction force according to the steering reaction force can be accurately applied.
[0057]
  Based on these theories, the control amount calculator 85 according to the present invention shown in FIG. 2 (that is, reaction force motor control called as a subroutine at step 550 in FIG. 3) can be configured.
  FIG. 8 is a flowchart illustrating a control procedure executed by the reaction amount motor control amount calculator 85 embodied by the control device 8.
  First, in step 810, as a preparation for executing the calculation of equation (8), values of the steering torque T and the time derivative of the turning reaction force F are obtained.
  Next, in step 830, the gain coefficient G of equation (8)_dfTo decide.
[0058]
  FIG. 9 shows the gain coefficient G_pf, G_dfIt is a graph which illustrates the data map used for calculation of. Gain factor G_pf, G_dfMay be changed based on the maps (a) and (b) as shown in FIG. For example, the gain coefficient G increases as the vehicle speed V increases._pf, G_dfSince the steering reaction force increases as the vehicle speed V increases, the steering feeling is further improved.
[0059]
  In this way, the gain coefficient G depends on the vehicle speed V._pf, G_dfThe means for optimizing is also an example for realizing a desired steering gear ratio variable means. The gain coefficient G_pfIf the value is increased, the stability of the control system deteriorates and vibration is likely to occur._dfSince the vibration can be suppressed by increasing the value, smooth steering feeling can be obtained even with such a setting.
[0060]
  Next, in step 850, the third term of equation (8) is determined. Here, the above function f_pf(F) may be a function depending on the vehicle speed V as shown in FIG. FIG. 10 shows a function f that can be used as the third term of the above equation (8)._pfIt is a graph which illustrates the setting form of (F, V).
[0061]
  By increasing the rate of increase of the steering reaction force in the region where the steering reaction force is smaller, the steering reaction force rises sharply when the steering wheel is turned from the neutral position, so that a steering feeling with a good build-up feeling can be obtained. Further, the function f depending on the vehicle speed V as illustrated in FIG._pfBy using (F, V), it is possible to optimize the third term of the equation (8) according to the vehicle speed V. For example, such a means is also an example for realizing a desired steering gear ratio variable means. According to such a setting, the steering reaction force increases as the vehicle speed V increases, and the steering feeling is further improved.
[0062]
  By these procedures, each term of equation (8) can be obtained. In step 870, the calculation process of equation (8) is executed. In step 890, the control amount T calculated in step 870 is calculated._RIs output to the reaction force motor drive circuit 6.
  With the above control procedure, it is possible or easy to generate a desired steering feeling at a low production cost in the steering control device 100 of the first embodiment.
[0063]
II. Abnormal operation
  Hereinafter, the operation of the steering control device 100 of the first embodiment when the steering torque sensor 4 is abnormal will be described.
  FIG. 11 is a control block diagram illustrating a more detailed logical configuration related to the control amount calculator 85 (FIG. 2) of the reaction force motor of this embodiment. In the control amount calculator 85 of the reaction force motor of this embodiment, as already explained using the equation (8) and FIGS. 8, 9, and 10, the control amount T_R(Output torque or drive current of the reaction force motor 5) is calculated and output to the reaction force motor drive circuit 6.
[0064]
  These operations are the same as when the steering torque sensor 4 is abnormal as in the normal state described above, and the operations shown in FIG. 11 and the operations shown by the control amount calculator 85 in FIG. 2 are the same. .
  That is, in the steering torque related value calculation unit 851 in FIG. 11, the steering torque related value T according to the following equation (9)._tIs calculated. Further, in the steering reaction force related value calculation unit 852, the steering reaction force related value T is calculated according to the following equation (10)._fIs calculated.
[Equation 9]
  T_t= G_ptT + G_dtDT / dt (9)
[Expression 10]
  T_f= F_pf(F, V) + G_dfDF / dt (10)
  Then, steering torque related value T_tAnd steering reaction force related value T_fIs processed according to the following equation (11).
## EQU11 ##
  T_R= A₁T_t+ A₂T_f  (Initial value: a₁= 1, a₂= -1) (11)
[0065]
  However, when the steering torque sensor 4 is abnormal, the gain value is the normal value (a₁= 1, a₂= -1). That is, this gain (coefficient a₁, A₂The means for dynamically switching the value in the case of abnormality is one of the most significant features of the present invention.
[0066]
  FIG. 12 is a flowchart (a) for explaining the processing relating to the reaction amount motor control amount calculator 85 (FIG. 11) of the first embodiment when a torque sensor abnormality is detected, and a variable criterion table (b) representing gain setting criteria. ).
  The subroutine for executing the abnormal time processing of FIG. 12A is executed by being called asynchronously with the aforementioned program when the steering torque sensor 4 has an abnormality. Such a subroutine is most commonly registered as an interrupt processing routine. For example, this is the case when the steering torque sensor 4 can directly give an external interrupt to the control device when it is abnormal.
[0067]
  In addition, when there is a contradiction among the above-described physical variables F, x, θ, T, V, etc., the abnormal state of the steering torque sensor 4 indicates an unnatural relationship (conflict) between these variables. You may make it detect by analyzing by.
[0068]
  In the above subroutine (FIG. 12A), for example, according to the variable criterion table of FIG.₁, A₂) Is rewritten as the following equation (12).
[Expression 12]
  a₁= 0 (corresponds to the steering torque related value disconnection means),
  a₂= −1 / 2 (corresponding to the first gain changing means) (12)
[0069]
  For example, by continuing the steering control in this way, it becomes possible for the driver to continue the steering operation. It can be avoided.
  The coefficient a₂According to the first gain changing means that rewrites the desired steering reaction force T to be output from the steering actuator even when the detected value T of the steering torque is assumed to be zero as described above._RCan be roughly corrected (adjusted). For this reason, the estimated value F of the steering reaction force F_hThere is no possibility that the degree of influence on the steering feeling becomes overwhelming or extremely dominant.
[0070]
  As can be seen from equation (11), according to the first gain changing means, the gain (coefficient a) is added to both the first and second terms on the right side of equation (10).₂However, as another modification, for example, the second term on the right side of Equation (10) is not changed, and only the first term on the right side of Equation (10) is changed to the first gain changing means. You may make it halve by. In this way, if the range of influence of the first gain changing means is limited, the steering reaction force T_RTherefore, the response of the steering reaction force does not deteriorate.
[0071]
  In addition, the second term (G_dfDF / dt) can be interpreted not only as a phase compensation term but also as a damper term for a steering system. It is considered that the second term on the right side of (10) should be unchanged and only the first term on the right side of equation (10) should be halved.
  These techniques are also referred to as phase correction amount changing means and the like in the third embodiment described later.
[0072]
[Second Embodiment]
  In step 540 of the first embodiment, instead of directly measuring the turning reaction force F using the turning reaction force sensor, the control amount u of the turning motor u._rThe value of the steering reaction force F is estimated based on the steering displacement amount x. Of course, in a general steering control device (SBW system), a steering reaction force sensor is mounted and the steering reaction force F is estimated. The force F may be obtained directly from the steering reaction force sensor.
[0073]
  FIG. 13 is a logical system configuration diagram of the steering control device 200 of the second embodiment. This steering control device 200 is different from the steering control device 100 of the first embodiment described above in that it has a steering reaction force sensor 20.
  For example, in the case where the steering reaction force sensor 20 is provided in this way, there may be a problem in parts cost, noise countermeasures, etc. However, according to such a method, the above disturbance observers Development man-hours and CPU overhead during operation can be reduced or suppressed.
[0074]
  FIG. 14 is a control block diagram illustrating a logical main configuration related to the steering reaction force generation method of the control device 8 of the steering control device 200 of the second embodiment. Since the control device 200 employs the above-described configuration, a steering reaction force estimator is not provided, but the steering angle θ is input to the control amount calculator 85 ′ of the reaction force motor. This is very different from the first embodiment described above.
[0075]
  FIG. 15 is a control block diagram illustrating a more detailed logical configuration regarding the control amount calculator 85 ′ (FIG. 14) of the reaction force motor of the second embodiment. That is, according to this control method, the control amount T of the reaction force motor 5 is determined._RIs calculated according to the following equation (13).
[Formula 13]
  T_R= A₁T_t+ A₂T_f+ A_ThreeT_K+ A_FourT_D,
  T_K= G_Kτ_KK,
  T_D= G_Dτ_DD                                            ... (13)
[0076]
  Where T_t, T_fIs calculated according to the above equations (9) and (10). Each coefficient a₁, A₂, A_Three, A_FourAre initial values of 1, -1, 0, 0, respectively. The variable τ_KK, G_KIs the steering speed ω determined by the maps (a) and (b) of FIG._H(= Dθ / dt) or a function of the vehicle speed V. The variable τ_DD, G_DIs the steering speed ω determined by the maps (a) and (b) of FIG._HAlternatively, it is a function of the vehicle speed V.
[0077]
  That is, the inertia torque related value calculation unit 853 in FIG. 15 uses the maps (a) and (b) in FIG._K(= G_Kτ_KK) Is calculated. Further, the friction torque related value calculation unit 854 in FIG. 15 uses the maps (a) and (b) in FIG._D(= G_Dτ_DD) Is calculated.
[0078]
  FIG. 18 shows a flowchart (a) for explaining the processing when a torque sensor abnormality is detected and a variable criterion table representing gain setting criteria for the control amount calculator 85 ′ (FIG. 15) for the reaction force motor of the second embodiment. (B) is illustrated.
  In this subroutine (FIG. 18A), as in the first embodiment described above, each gain (coefficient a in FIG. 15) according to the variable criterion table of FIG.₁, A₂, A_Three, A_Four) Is rewritten as the following equation (14).
[Expression 14]
  a₁= 0 (corresponds to the steering torque related value disconnection means),
  a₂= -1 / 2 (corresponding to the first gain changing means),
  a_Three= 1 (corresponding to the second gain changing means),
  a_Four= 1 (corresponding to the third gain changing means) (14)
[0079]
  According to the above configuration, a simulation related to the inertia of the steering mechanism or the steering mechanism that has been conventionally processed mainly using the steering torque T or the like during normal operation of the torque sensor (that is, the inertia torque) Output), or a simulation related to the frictional force inside the steering mechanism or the steering mechanism (ie, the output of the friction torque), etc._HAnd the vehicle speed V can be implemented. As a result, it is possible to avoid the steering feeling from becoming extremely light, and thus it is possible to reduce the uncomfortable feeling of the problem.
[0080]
  It should be noted that the calculation for a variable with a gain of 0 may be omitted. For example, in the above case, the inertia torque T_K(= G_Kτ_KK) And friction torque T_D(= G_Dτ_DD) Etc. need not be particularly calculated. For example, when the control amount calculator 85 ′ (FIG. 15) is configured by a program, it goes without saying that such omission can reduce the CPU overhead.
[0081]
[Third embodiment]
  In the third embodiment, the abnormality processing is performed in substantially the same manner as in the second embodiment, but in the third embodiment, the above-described equation (10) is transformed into the following equation (15). The point of use is greatly different. Here, the initial value of the gain λ is 1.
[Expression 15]
  T_f= F_pf(F, V) + λG_dfDF / dt (15)
[0082]
  FIG. 19 is a flowchart (a) for explaining the processing and a variable criterion table representing gain setting criteria when a torque sensor abnormality is detected with respect to the control amount calculator 85 ′ (FIG. 17) for the reaction force motor of the third embodiment. (B).
  In this subroutine (FIG. 19A), in the same manner as in the second embodiment, each gain (coefficient a₁, A₂, A_Three, A_Four, Λ) is rewritten as the following equation (16).
[Expression 16]
  a₁= 0 (corresponds to the steering torque related value disconnection means),
  a₂= -1 / 2 (corresponding to the first gain changing means),
  a_Three= 1 (corresponding to the second gain changing means),
  a_Four= 1 (corresponding to the third gain changing means),
  λ = 2 (corresponding to phase correction amount changing means) (16)
[0083]
  According to the above configuration, as mentioned at the end of the first embodiment, the steering reaction force T_RTherefore, the response of the steering reaction force does not deteriorate, and the feeling of viscosity at the time of steering does not deteriorate.
[0084]
  In the variable criterion table of FIG._Three, A_FourEach initial value (normal value) is set to 1/5, 3/10, etc., but for example, inertia torque, friction torque (damper torque), etc. Steering speed ω_HBased on the vehicle speed V and the like, and the steering reaction force T_RIn the terms constituting (for example, T in the above formula (13))_KAnd T_DEtc.) may be included as standard.
[0085]
  According to such settings, the steering speed ω_HIt is possible to generate and output inertia torque, friction torque (damper torque), etc. that also take account of the above, and the discomfort associated with the transition when changing (switching) as exemplified in the above equation (16) However, there is an effect that it can be alleviated even a little.
[Brief description of the drawings]
FIG. 1 is a logical system configuration diagram of a steering control device 100 according to a first embodiment of the present invention.
FIG. 2 is a control block diagram illustrating a logical main configuration related to a steering reaction force generation method of the control device 8 of the steering control device 100;
FIG. 3 is a flowchart illustrating an outline of a control procedure executed by the control device 8 of the steering control device 100.
FIG. 4 is a flowchart illustrating a control procedure executed by a steered motor control unit (target value calculator 81, position controller 82) embodied by a control device 8;
[Fig.5] Transmission ratio G_rThe graph which illustrates the data map used for calculation.
FIG. 6 is a flowchart illustrating a control procedure executed by a turning reaction force estimator 88 embodied by the control device 8;
7 is a formula table summarizing vector calculation formulas used by the steering reaction force estimator 88. FIG.
FIG. 8 is a flowchart illustrating a control procedure executed by a control amount calculator 85 of the reaction force motor embodied by the control device 8;
FIG. 9 Gain factor G_pf, G_dfThe graph which illustrates the data map used for calculation.
FIG. 10: Function f_pfThe graph which illustrates the setting form of (F, V).
FIG. 11 is a control block diagram illustrating a more detailed logical configuration related to a control amount calculator 85 (FIG. 2) of the reaction force motor according to the first embodiment;
FIG. 12 is a flowchart (a) illustrating a process and a variable criterion table (b) indicating a gain setting criterion when a torque sensor abnormality is detected with respect to the control amount calculator 85 (FIG. 11) of the reaction force motor of the first embodiment. ).
FIG. 13 is a logical system configuration diagram of a steering control device 200 according to a second embodiment.
14 is a control block diagram illustrating a logical main configuration related to a steering reaction force generation method of the control device 8 of the steering control device 200. FIG.
FIG. 15 is a control block diagram illustrating a more detailed logical configuration related to a control amount calculator 85 ′ (FIG. 16) of the reaction force motor according to the second embodiment;
FIG. 16 shows an inertia torque T of the second embodiment._KGraph related to calculation.
FIG. 17 shows a friction torque T according to the second embodiment._DGraph related to calculation of (damper torque).
FIG. 18 is a flowchart (a) illustrating a process and a variable criterion table representing a gain setting criterion when a torque sensor abnormality is detected with respect to the control amount calculator 85 ′ (FIG. 17) of the reaction force motor of the second embodiment. b).
FIG. 19 is a flowchart (a) illustrating a process and a variable criterion table representing a gain setting criterion when a torque sensor abnormality is detected with respect to the control amount calculator 85 ′ (FIG. 17) of the reaction force motor of the third embodiment. b).
[Explanation of symbols]
  100 ... Steering control device
      1… Steering wheel (handle)
      2… Steering shaft (steering shaft)
      3 ... Steering angle sensor
      4 ... Steering torque sensor
      5 ... Reaction force motor
      6 ... Reaction force motor drive circuit
      7 ... Vehicle speed sensor
      8 ... Control device (computer)
      9 ... Steering motor drive circuit
    10 ... Steering displacement sensor
    11 ... Steering motor
    12 ... Reducer
    13 ... Steering shaft
    81 ... Target value calculator
    82 ... Position controller
    85 ... Control amount calculator for reaction force motor
    851 ... Steering torque related value calculation unit
    852 ... Steering reaction force related value calculation section
    853 ... Inertia torque related value calculation section
    854 ... Friction torque related value calculation unit
    88… Steering reaction force estimator
    T: Steering torque
    F ... Steering reaction force
    V ... Vehicle speed
    θ… steering angle
    x ... Steering displacement
    x_n  … Target value of turning displacement
    u_r   ... Control amount of steering motor
    T_R   ... Control amount of reaction force motor
    T_K   … Inertia torque
    T_D   … Friction torque (damper torque)
    F_h   … Estimated steering reaction force
    f ... Frictional force generated in the steering mechanism
    G: Observer gain (3-by-2 constant matrix)
    k ... Time parameter indicating sampling time
  x₀(k) ... Observer state quantity at time k (state vector)
  A, C ... 3-by-3 constant matrix
  B, D ... 3-by-2 constant matrix

Claims (7)

A steering mechanism for steering actuator controls the steering reaction force T _R to be applied to the steering wheel, a steering mechanism for controlling the turning displacement x according to the actual steering angle of the steered wheels are mechanically separated In a steer-by-wire system in which the coupling mechanism that couples both of these is alternatively configured by an electrical interlocking mechanism,
The steering mechanism is
A steering torque sensor for detecting a steering torque T applied by a driver to the steering wheel;
A turning reaction force calculating means for calculating a turning reaction force F acting on the turning mechanism by a road surface reaction force ;
On the basis of the said turning reaction force F which is calculated by said detected by the steering torque sensor and the steering torque T the turning reaction force calculating means, and a steering reaction force calculation means for calculating a steering reaction force T _R Have
The steering reaction force calculating means includes
Wherein when the abnormality of the steering torque sensor is detected, the calculation of the steering reaction force T _R, the steering torque related value disconnecting means to stop the input or use of the steering torque T that the steering torque sensor detects,
And a first gain changing means for changing a coefficient value of the steering reaction force F or a coefficient value of a related value of the steering reaction force F when an abnormality of the steering torque sensor is detected. Steering control device. The steering reaction force calculating means includes
Based on the rotational speed omega _H of the steering wheel, the inertia torque T _K according to the moment of inertia of the steering mechanism, the inertia compensation means for setting as one term that constitutes the steering reaction force T _R,
When the steering torque sensor abnormality is detected, the coefficient value of the inertia torque T _K, or characterized by having a second gain changing means for changing the coefficient values of the associated value of the inertia torque T _K The steering control device according to claim 1 . The steering reaction force calculating means includes
Based on the rotational speed omega _H of the steering wheel, the friction torque T _D according to the internal friction of the steering mechanism or the steering mechanism, a friction compensation unit for setting as one term that constitutes the steering reaction force T _R ,
When the steering torque sensor abnormality is detected, the coefficient value of the friction torque T _D, or characterized by having a third gain changing means for changing the coefficient values of the relevant values of the friction torque T _D The steering control device according to claim 1 or 2 . The steering reaction force calculating means is:
A turning reaction force phase correcting means for correcting the phase of the turning reaction force F;
Wherein when the abnormality of the steering torque sensor is detected, any one of claims 1 to 3; and a phase correction amount changing means for changing the correction amount for the turning reaction force F of the phase The steering control device according to item 1. The steering control device according to any one of claims 1 to 4 , wherein the turning reaction force calculation means includes a turning reaction force sensor that measures the turning reaction force F. The turning reaction force calculating means, the measured value I _a of the turning current flowing in the steering actuator to the steering mechanism has the command value I _n, or on the basis of these related values, the turning reaction force F The steering control device according to any one of claims 1 to 4 , further comprising a steered reaction force estimating unit. The steering reaction force estimation means is
Measurements I _a of the turning current flowing in the steering actuator to the steering mechanism has the command value I _n, or with these related values,
Based on the steering displacement amount x, its command value x _n , or related values related thereto,
The steering control device according to claim 6 , further comprising a disturbance observer that estimates the steering reaction force F.

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