JP4011424B2 - Steering control device - Google Patents

Description

BACKGROUND OF THE INVENTION
The present invention relates to an in-vehicle SBW system (steer-by-wire system), and more particularly to a steering reaction force generation method for improving the steering feeling associated with the steering operation of a vehicle.
[0001]
[Prior art]
As the steer-by-wire system, for example, what is described in, for example, an open patent publication "Japanese Patent Laid-Open No. 5-105100: Steering device for vehicle" is widely known.
In the steering mechanism of these conventional devices, regarding a method of generating a steering reaction force to be applied to a steering shaft connected to a steering wheel (hereinafter sometimes referred to as “steering wheel” or “steering steering wheel”). For example, the following features can be seen.
(Characteristic 1) Drive control of the steering shaft is executed based on the steering angle or the steering reaction force.
(Feature 2) A steering reaction force component linear with respect to the steering reaction force is generated.
(Characteristic 3) A turning reaction force sensor is used to detect a turning reaction force.
[0002]
[Problems to be solved by the invention]
The above prior art has the following problems.
(Problem 1) The steering motor that drives the steering shaft is controlled based on a control amount corresponding to the steering angle θ. On the other hand, when the steering wheel starts to be turned from the neutral position (θ = 0), the turning reaction force acting on the turning mechanism is generated only after the turning displacement occurs. However, since the steering shaft having the steering wheel is driven based on a control amount proportional to the detected steering reaction force, when the steering wheel is turned from the neutral position, the initial steering reaction force is Compared to the case of steering a hydraulic power steering device or the like, the steering operation becomes uncomfortable at this time.
[0003]
Such a problem of the response of the steering reaction force at the start of turning of the steering wheel is also caused by the relatively small mechanical inertia, viscosity, etc. of the separated steering mechanism. However, remodeling these from the viewpoint of mechanical structure is not necessarily a desirable measure because it causes derivation problems in the number of parts, manufacturing cost, vehicle weight, and the like.
[0004]
(Problem 2) When the driver weakens the steering torque, the steering handle may return rapidly toward the neutral point according to the turning reaction force, and vibration may occur around the neutral point.
[0005]
(Problem 3) Since the steering reaction force is converted with a linear function (one example: broken line in FIG. 1) and the drive control of the steering shaft is performed based on the converted value, the steering wheel is turned from the neutral position. In addition, the increase rate of the steering reaction force is inevitably small in a region where the steering angle is small, resulting in a steering feeling with a weak build-up feeling (feeling of certainty) near the neutral position.
[0006]
(Problem 4) Since the steering reaction force sensor tends to increase in size as the accuracy increases, there are many disadvantages in terms of securing installation space, weight, cost, and the like.
Further, when detecting the steering reaction force using the steering reaction force sensor, if the steering reaction force sensor has a large noise, the steering wheel may vibrate in accordance with the noise.
[0007]
The present invention has been made to solve the above-described problems, and an object of the present invention is to improve the steering feeling associated with the steering operation of a vehicle in an in-vehicle SBW system (steer-by-wire system). is there.
[0008]
[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 includes a steering mechanism having a steering actuator that applies a steering reaction force to the steering wheel,A control amount u determined based on the steering angle θ of the steering wheel detected by the steering angle sensor and the steering displacement amount x detected by the steering displacement amount sensor. _r ByIn a steer-by-wire system in which a steering mechanism having a steering actuator that drives a steering shaft is mechanically separated, and a coupling mechanism that couples both of these is replaced by an electrical interlocking mechanism., SuA steering torque sensor for detecting a steering torque T applied by the driver to the tearing wheel;The roadA steering reaction force sensor for detecting a steering reaction force F acting on the steering mechanism based on a surface reaction force and the like, and a time differential dF / d of the steering torque T, the steering reaction force F, and the steering reaction force F.tUse the control amount u of the steering actuator_hIs to decide.
[0009]
  In place of the time derivative dF / dt,A physical quantity representing the time fluctuation of the turning reaction force F per predetermined timeI.e.It is a real time variable that is approximately proportional to the time change rate of the turning reaction forceLikeUse any physical quantityAlsoit can.
[0010]
If the steering shaft is driven on the basis of the steering reaction force and its time derivative in accordance with the first means of the present invention described above, the differential value dF / dt of the steering reaction force is obtained as can be seen from FIG. Since the steering reaction force can be steeply raised with the start-up, the steering reaction force according to the turning reaction force can be quickly applied.
[0011]
Further, in the vicinity of the neutral point, the steering reaction force F is approximately proportional to the steering displacement amount x, so the differential value dF / dt of the steering reaction force is the differential value dx / dt (≡v) of the steering displacement amount. Is approximately proportional to Therefore, if the differential value dF / dt is used, a term (−av; a> 0) substantially proportional to the turning speed v can be generated. This term can also be used as a term expressing the viscous resistance of the steering mechanism. Therefore, when such a term (-av) is included in the term for generating the steering reaction force, for example, when the steering torque is suddenly weakened after turning, the steering handle quickly returns toward the neutral point. Since this acts as a term to suppress this (damper action term), vibration of the steering shaft can be suppressed by this term.
[0012]
By these actions, road surface information appearing in the steering reaction force can be transmitted to the driver without a sense of incongruity, and a robust and smooth steering feeling with a build-up feeling (feeling of certainty) can be generated. .
[0013]
  The second means of the present invention includes a steering mechanism having a steering actuator that applies a steering reaction force to the steering wheel,A control amount u determined based on the steering angle θ of the steering wheel detected by the steering angle sensor and the steering displacement amount x detected by the steering displacement amount sensor. _r ByIn a steer-by-wire system in which a steering mechanism having a steering actuator that drives a steering shaft is mechanically separated, and a coupling mechanism that couples both of these is replaced by an electrical interlocking mechanism., SuA steering torque sensor for detecting a steering torque T applied by the driver to the tearing wheel;The roadA steering reaction force sensor for detecting a steering reaction force F acting on the steering mechanism based on a surface reaction force and the like, and a steering reaction force F as an independent variable z, Y = f_pf(Z) = − f_pf(−z) and a monotonically decreasing function in which the rate of increase of the dependent variable Y (dY / dz or） Y / ∂z) is wide in a predetermined domain {z | 0 ≦ z <ε} near the origin The function f_pf(Z), a steep riser for calculating the value of the dependent variable Y is provided, and the control amount u of the steering actuator is determined using the steering torque T and the dependent variable Y._hIs to decide.
[0014]
However, the monotonic decreasing function in the broad sense here means a predetermined domain {x | x₁≦ x ≦ x₂}, "X₁≦ ∀a <∀b ≦ x₂⇒ "f (x₁) ≧ f (a) ≧ f (b) ≧ f (x₂) And f (x₁)> F (x₂)] ”. When there is a point where the dependent variable Y cannot be differentiated or partially differentiated by z, the rate of change in the vicinity of the point, the average rate of change in the vicinity of the point, and the like are appropriately substituted.
[0015]
For example, the steering reaction force is converted by using a function shown by the solid line in FIG. 1 and the steering shaft is driven based on the converted value. The rate of increase in the steering reaction force increases as the area increases.
Therefore, a steering feeling with a good build-up feeling can also be obtained by such a steering reaction force generating means.
[0016]
  The third means includes a steering mechanism having a steering actuator for applying a steering reaction force to the steering wheel,A control amount u determined based on the steering angle θ of the steering wheel detected by the steering angle sensor and the steering displacement amount x detected by the steering displacement amount sensor. _r ByIn a steer-by-wire system in which a steering mechanism having a steering actuator that drives a steering shaft is mechanically separated, and a coupling mechanism that couples both of these is replaced by an electrical interlocking mechanism., SuA steering torque sensor for detecting a steering torque T applied by the driver to the tearing wheel;The roadEstimated value F of steering reaction force acting on the steering mechanism based on surface reaction force, etc._h, The control amount u of the steering actuator_rAnd a steering reaction force estimating means for calculating using the steering displacement amount x, a steering torque T, and an estimated value F_hIs used to control the steering actuator control amount u._hIs to decide.
[0017]
In this way, by using the estimated value of the steering reaction force, the steering reaction force sensor becomes unnecessary. Further, vibration due to the noise of the steering reaction force sensor does not occur.
Therefore, when the estimated value of the turning reaction force is used, the cost can be reduced and a smoother steering feeling can be obtained.
[0018]
Further, the first to third means of the present invention can be arbitrarily combined, and between them, “when turning reaction force estimating means is provided, turning reaction force There is no special contradiction requirement other than "no need to install a sensor".
Therefore, by combining these individual means arbitrarily, it is possible to simultaneously obtain the actions and effects of the first to third means according to the combination.
[0019]
That is, the fourth means of the present invention has the steering reaction force F as an independent variable z in the above first means, and Y = f_pf(Z) = − f_pf(−z) and a monotonically decreasing function in which the rate of increase (dY / dz or ∂Y / ∂z) of the dependent variable Y is broad in a predetermined domain {z | 0 ≦ z <ε} near the origin The function f_pf(Z) includes a steep riser for calculating the value of the dependent variable Y, and a predetermined coefficient multiple G of the turning reaction force F_pfUsing the dependent variable Y instead of F, the control amount u of the steering actuator u_hIs to decide.
[0020]
The fifth means is the steering torque T, estimated value F in the third means._h, And estimated value F_hTime derivative of dF_h/ Dt, the control amount u of the steering actuator_hIs to decide.
[0021]
The sixth means is the estimated value F in the third means._hAs the independent variable z, Y = f_pf(Z) = − f_pf(−z) and a monotonically decreasing function in which the rate of increase (dY / dz or ∂Y / ∂z) of the dependent variable Y is broad in a predetermined domain {z | 0 ≦ z <ε} near the origin The function f_pf(Z), a steep rise means for calculating the value of the dependent variable Y is provided, and the control amount u of the steering actuator is determined using the steering torque T and the dependent variable Y._hIs to decide.
[0022]
Further, the seventh means is the steering means T, the dependent variable Y, and the estimated value F in the sixth means._hTime derivative of dF_h/ Dt, the control amount u of the steering actuator_hIs to decide.
Also by various combinations found in any one of the fourth to seventh means as described above, the actions and effects of the first to third means can be obtained simultaneously according to the combination. .
[0023]
Further, an eighth means of the present invention provides the control amount u of the steering actuator in any one of the first to seventh means._hOr the control amount u of the steering actuator u_rIs provided with a steering gear ratio variable means for changing the speed according to the vehicle speed V.
As means for realizing such means, for example, various gain coefficient adjusting means exemplified in FIG. 7, FIG. 11 or FIG.
[0024]
By these steering gear ratio variable means, for example, an effect that the ratio of the turning angle (steering displacement amount x) to the steering angle θ can be arbitrarily changed according to the vehicle speed V is obtained. By these actions, it is possible to obtain an effect such as being able to generate a steering feeling that is excellent in straight running performance, relatively robust and stable when traveling at a high speed.
That is, according to such means, the steering feeling can be optimized or optimized according to the vehicle speed V.
[0025]
In addition, according to such tuning, the steering feeling can be adjusted arbitrarily according to the characteristics of various types of vehicles such as luxury type vehicles, sports type vehicles, and small and medium size vehicles, and the expected preferences of customer groups. Therefore, the above-described means has high industrial utility value as a means for giving a great added value to the vehicle.
[0026]
  Furthermore, a ninth means of the present invention is the steering torque T in any one of the first to eighth means.OrSteering angleθIt has as an independent variable λ (−a ≦ λ ≦ a), satisfies “λ> 0 → F (λ) ≦ 0” and “F (−λ) = − F (λ)”, and is substantially sine of one cycle. Neutral compensation torque T represented by a function F (λ) having a wave shape, a substantially sawtooth shape, or a substantially N-shape._C, The control amount u of the steering actuator_hIs included as one of the terms that generate
[0027]
Such a technique is also found in, for example, a known prior art described in an open patent publication “Japanese Patent Laid-Open No. 2002-087300: Electric Power Steering Device”. Especially in a vehicle adopting an SBW system having relatively small inertia, viscosity, etc., such a technique is appropriately combined with any one of the above-described means of the present invention to generate a further sense of steering stability. Is desirable.
[0028]
In this case, the neutrality compensation torque T is appropriately adjusted within a range in which the road surface information appearing in the steering reaction force is not reduced._CHowever, it is desirable to arbitrarily adjust the steering feeling according to the characteristics of various types of vehicles, the expected customer group preferences, and the like.
By the above means of the present invention, the above-mentioned problem can be effectively or rationally solved.
[0029]
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.
〔Example〕
FIG. 3 is a system configuration diagram of the steering control device 100 of 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.
[0030]
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 (u_h) 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.
[0031]
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.
[0032]
On the other hand, the steering mechanism includes a steering actuator (steering motor 11) that steers the steered wheels 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.
[0033]
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.
[0034]
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.
[0035]
The 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 to the control device 8. Based on these detection results, the control signals (control force u of the reaction force motor u) are sent to the drive circuits (6, 9) so that the reaction force motor 5 and the turning motor 11 output a predetermined drive force._h, Steering motor control amount u_r) Is output.
[0036]
FIG. 4 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 u of reaction force motor_h) Is calculated by the control amount calculator 85 of the reaction force motor.
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._refBased on the steering displacement amount x detected by the steering displacement amount sensor 10, the control amount u of the steering motor by well-known PD control_rIs calculated.
[0037]
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. However, in the following embodiment, the steered reaction force estimator 88 is replaced with a steered reaction force estimator 88. The steering control device (100) having the above will be described in detail.
[0038]
FIG. 5 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.
In this control procedure, 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.
[0039]
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. 6) 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.
[0040]
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. 10) for performing reaction force motor control is called and executed. This subroutine is a subroutine that embodies the reaction amount motor control amount calculator 85 of FIG.
[0041]
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. 6) for performing the turning motor control called as a subroutine in step 530 will be described in detail.
[0042]
1. Steering axis control procedure
FIG. 6 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 FIG.
[0043]
Target value x of steering displacement x from steering angle θ_refIs determined by equation (1). Transmission ratio G_rA constant may be used, but according to the steering angle θ, the vehicle speed V, etc., for example, using the 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 a setting according to the vehicle speed, the steering gear ratio variable means of the present invention can be implemented.
[0044]
[Expression 1]
x_ref= 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.
[0045]
Deviation (x_ref-X) and its time derivative d (x_ref-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_refDrive control is performed so as to follow. Gain factor G_px, G_dxIs a constant.
[Expression 2]
u_r= G_px(X_ref-X) + G_dx・ D (x_ref-X) / dt (2)
For example, in this way, the calculation process (steps 660 and 680) of the position controller 82 can be executed.
[0046]
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. 5) is specifically illustrated with reference to FIGS.
[0047]
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. Further, f is a frictional force generated inside the turning mechanism such as the turning motor 11 and the converter (speed reducer 12). As this frictional force f, a value measured in advance may be used, or the frictional force f may be obtained as a function of the following x and v.
[Equation 3]
M ・ d²x / dt²= U_r-F-F≡d (3)
[0048]
Here, if the force d is regarded as a disturbance in the disturbance observer, a disturbance observer expressed in the form of equation (a) in FIG. 9 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_hRepresents respective estimated values of F, x, v, and d, respectively. The variable v (steering speed) is defined by the following equation (4).
[Expression 4]
v = dx / dt (4)
[0049]
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 calculated sequentially 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) can be a zero vector. Also, the initial value v (0) of the steering speed v may be zero.
[0050]
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 (5).
[Equation 5]
F_h(k) = u_r(k) −f (k) −d_h(k) ... (5)
[0051]
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 force motor control amount u._hSince 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.
[0052]
Incidentally, the detected value of the steering reaction force sensor and the estimated value F of the above equation (5)_hFf defined by the following equation (6) instead of_hBased on the control amount u of the reaction force motor_hMay be set.
[Formula 6]
Ff_h(k) ≡F_h(k) + f (k) = u_r(k) −d_h(k) ... (6)
This variable Ff_hHas a shape including the frictional force f._hBy using this, it is possible to apply a steering reaction force according to not only the steering reaction force F but also the friction force f. Thereby, when the steering wheel is turned from the neutral position, the steering reaction force rises more quickly as indicated by the broken line in FIG.
[0053]
In addition, if Equation (6) is used instead of Equation (5), the frictional force f is previously obtained empirically at the time of program development, or a function having x and v as independent variables is used. Thus, the advantage that the frictional force f need not be dynamically calculated in real time is also obtained.
[0054]
Based on these theories, the turning reaction force estimator 88 (that is, step 540 in FIG. 5) according to the present invention in FIG. 4 can be configured.
FIG. 8 is a flowchart illustrating a control procedure executed by the turning reaction force estimator 88 embodied by the control device 8.
[0055]
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 (4).
Next, in step 920, d is calculated according to equation (c) in FIG._hFind the value of (k).
In step 930, Ff is calculated according to the above equation (6)._hFind the value of (k).
In step 940, this Ff_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.
[0056]
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.
[0057]
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 the above-described step 510.
[0058]
Next, the reaction force motor control called as a subroutine in step 550 of FIG. 5 will be described in detail.
[0059]
3. Steering shaft (reaction force motor) control procedure
Control amount u of reaction force motor 5_hCan be determined based on the steering torque T and its time derivative dT / dt, and the turning reaction force F and its time derivative dF / dt. For example, the control amount u of the reaction force motor 5_hMay be determined according to the following equation (7), but in this embodiment, the control amount u of the reaction force motor 5 is calculated by the following equation (8)._hAn 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 of the third and fourth terms on the right side of each of the equations (7) and (8)._hShall be substituted.
[Expression 7]
u_h= G_ptT + G_dt・ DT / dt-G_pfFG_dfDF / dt (7)
[Equation 8]
u_h= G_ptT + G_dtDT / dt-f_pf(F) -G_dfDF / dt (8)
[0060]
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.
[0061]
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.
[0062]
Based on these theories, the control amount calculator 85 according to the present invention in FIG. 4 (that is, the reaction force motor control called as a subroutine in step 550 in FIG. 5) can be configured.
FIG. 10 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.
[0063]
FIG. 11 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.
[0064]
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 the steering gear ratio variable means of the present invention. 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.
[0065]
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. 12 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).
[0066]
When the steering reaction force starts to be turned from the neutral position by increasing the rate of increase of the steering reaction force in the region where the steering reaction force is smaller (steep raising means), the steering reaction force is as shown in FIG. 1 or FIG. As a result, a good steering 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 the steering gear ratio variable means of the present invention. According to such a setting, the steering reaction force increases as the vehicle speed V increases, and the steering feeling is further improved.
[0067]
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 u calculated in step 870 is displayed._hIs output to the reaction force motor drive circuit 6.
[0068]
By the above control procedure, it is possible or easy to generate a desired steering feeling at a low production cost.
In step 540, instead of directly measuring the turning reaction force F using the turning reaction force sensor, the control amount u of the turning reaction force motor is determined._hThe value of the steering reaction force F is estimated based on the steering displacement amount x. Of course, in the steering control device (SBW system) having the steering reaction force sensor, the steering reaction force F is changed. You may make it obtain | require directly from a rudder reaction force sensor. In this case, parts cost, noise countermeasures, etc. may be a problem. However, according to such a method, it is possible to reduce the development man-hours and CPU overhead during operation of the disturbance observer. Can be suppressed.
[0069]
[Other variations]
In the above-described embodiment, the control amount u of the above equation (7) or (8)._hIs determined based on the steering torque T, the turning reaction force F, and the values of their respective time derivatives, but the control amount u of the reaction force motor 5 is determined._hA term depending on the steering angle θ may be added.
Hereinafter, such a θ-dependent term to be added to the right side of Expression (7) or Expression (8) will be exemplified.
[0070]
For example, such a θ-dependent term includes the following neutral sense compensation torque T_CEtc. can be considered. This neutral feeling compensation torque T_CCan be determined as shown in the following equation (9), for example. However, the steering angle θ is 0 at the neutral point.
[Equation 9]
T_C= G3 · G1 · F (Θ),
Θ = θ / (μ + G1) (9)
[0071]
FIG. 13 is a control block diagram illustrating the calculation procedure of the above equation (9).
Here, the gain G1 is given vehicle speed dependency as shown in the figure. The effective area limiting unit 262 gives the steering speed dependency to the gain G3 based on the steering speed ω estimated by the steering speed estimation unit 266. The denominator μ is an appropriate constant of about 0 <μ <4.
[0072]
The steering speed estimator 266 determines the rotational angle θ of the reaction force motor 5._MAnd the steering speed ω is estimated based on the rate of change of the steering torque T with respect to time. Further, the neutral position learning unit 261 has an angle θ that relatively represents the steering angle._HEtc. to neutral position θ₀Is a control block that empirically determines the difference (θ_H−θ₀), The absolute steering angle θ is calculated.
[0073]
Due to the operations of the effective region limiting unit 262 and the vehicle speed dependent gain G1 calculating unit 263 as described above, in a steering speed region where a particularly stable neutral feeling is expected during high speed traveling, that is, in a low speed steering region where ω≈0. Only, neutral compensation torque T desired_CIs output.
In addition, the vehicle speed dependency of “Θ = θ / (μ + G1)” in the above formula (9) can also be considered as an example of implementing the steering gear ratio varying means of the present invention.
[0074]
The steering angle dependence term generating means as described above can be found in the known prior art described in, for example, published patent publication “Japanese Patent Application Laid-Open No. 2002-087300: Electric Power Steering Device”. In a vehicle that employs an SBW system in which the mechanical inertia, viscosity, etc. of the steering mechanism is relatively small, such a steering reaction force generation method having the θ dependency should be appropriately combined with the above-described embodiments. Therefore, it is possible to generate a further steering stability according to the type of vehicle, the expected preference of the customer group, and the like, which can be expected as an additional tuning technique.
[0075]
In this case, the θ-dependent term (one example: the neutrality compensation torque T described above) is appropriately selected within a range in which the road surface information appearing in the steering reaction force is not reduced._C) In addition, the control amount u in the above equation (7) or (8)_hHowever, for example, the steering feeling can be adjusted by adding such means.
[Brief description of the drawings]
FIG. 1 is a graph illustrating the configuration of a steep start-up unit of the present invention.
FIG. 2 is a graph for explaining the operation and effect of the present invention.
FIG. 3 is a system configuration diagram of a steering control device 100 according to an embodiment of the present invention.
4 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.
FIG. 5 is a flowchart illustrating an outline of a control procedure executed by the control device 8 of the steering control device 100.
6 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.
FIG. 7: Transmission ratio G_rThe graph which illustrates the data map used for calculation.
FIG. 8 is a flowchart illustrating a control procedure executed by a turning reaction force estimator 88 embodied by the control device 8;
9 is a formula table summarizing vector calculation formulas used by the steering reaction force estimator 88. FIG.
FIG. 10 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. 11: Gain coefficient G_pf, G_dfThe graph which illustrates the data map used for calculation.
FIG. 12 shows a function f._pfThe graph which illustrates the setting form of (F, V).
FIG. 13 is a control block diagram illustrating a calculation procedure in another modified example.
[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
88… Steering reaction force estimator
T: Steering torque
F ... Steering reaction force
V ... Vehicle speed
θ… steering angle
x ... Steering displacement
x_ref… Target value of turning displacement
u_r  ... Control amount of steering motor
u_h  ... Control amount of reaction force motor
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
A, C ... 3-by-3 constant matrix
B, D ... 3-by-2 constant matrix

Claims (9)

Based on a steering mechanism having a steering actuator that applies a steering reaction force to the steering wheel, a steering angle θ of the steering wheel detected by a steering angle sensor, and a steering displacement amount x detected by a steering displacement amount sensor. and a steering mechanism having a steering actuator that drives a steering shaft by the control amount u _r determined mechanically separated and alternatively configured with an electrical interlocking mechanism connecting mechanism for connecting the both In steer-by-wire systems,
And a steering torque sensor for detecting the steering torque T for the driver to grant before Symbol steering wheel,
A turning reaction force sensor for detecting a turning reaction force F acting on the turning mechanism based on a road surface reaction force and the like,
A steering control device, wherein a control amount u _h of the steering actuator is determined using the steering torque T, the steering reaction force F, and the time differential dF / dt of the steering reaction force F. Based on a steering mechanism having a steering actuator that applies a steering reaction force to the steering wheel, a steering angle θ of the steering wheel detected by a steering angle sensor, and a steering displacement amount x detected by a steering displacement amount sensor. and a steering mechanism having a steering actuator that drives a steering shaft by the control amount u _r determined mechanically separated and alternatively configured with an electrical interlocking mechanism connecting mechanism for connecting the both In steer-by-wire systems,
And a steering torque sensor for detecting the steering torque T for the driver to grant before Symbol steering wheel,
A turning reaction force sensor for detecting a turning reaction force F acting on the turning mechanism based on a road surface reaction force, and the like;
The steering reaction force F is set as an independent variable z, Y = f _pf (z) = − f _pf (−z) is satisfied, and in a predetermined domain {z | 0 ≦ z <ε} near the origin. A steep rise means for calculating the value of the dependent variable Y by a function f _pf (z) in which the increasing rate (dY / dz or ∂Y / ∂z) of the dependent variable Y is a monotonically decreasing function in a broad sense; ,
A steering control device, wherein a control amount u _h of the steering actuator is determined using the steering torque T and the dependent variable Y. Based on a steering mechanism having a steering actuator that applies a steering reaction force to the steering wheel, a steering angle θ of the steering wheel detected by a steering angle sensor, and a steering displacement amount x detected by a steering displacement amount sensor. and a steering mechanism having a steering actuator that drives a steering shaft by the control amount u _r determined mechanically separated and alternatively configured with an electrical interlocking mechanism connecting mechanism for connecting the both In steer-by-wire systems,
And a steering torque sensor for detecting the steering torque T for the driver to grant before Symbol steering wheel,
An estimate F _h of the turning reaction force acting on the steering mechanism on the basis of the road surface reaction force or the like, the control amount u _r of the turning actuator and the steering reaction force calculated by using the turning displacement amount x An estimation means,
A steering control device, wherein a control amount u _h of the steering actuator is determined using the steering torque T and the estimated value F _h . The steering reaction force F is set as an independent variable z, Y = f _pf (z) = − f _pf (−z) is satisfied, and in a predetermined domain {z | 0 ≦ z <ε} near the origin. A function of increasing the dependent variable Y (dY / dz or ∂Y / ∂z) by a function f _pf (z), which is a monotonically decreasing function in a broad sense, has a steep riser that calculates the value of the dependent variable Y;
2. The steering control device according to claim 1, wherein a control amount u _h of the steering actuator is determined using the dependent variable Y instead of the predetermined coefficient multiple G _pf F of the steering reaction force F. 3. The control amount u _h of the steering actuator is determined using the steering torque T, the estimated value F _h , and a time derivative dF _h / dt of the estimated value F _h . Steering control device. The estimated value F _h is an independent variable z, satisfies Y = f _pf (z) = − f _pf (−z), and is dependent on a predetermined domain {z | 0 ≦ z <ε} near the origin. A function of increasing the variable Y (dY / dz or ∂Y / ∂z) by a function f _pf (z), which is a monotonically decreasing function in a broad sense, has a steep riser that calculates the value of the dependent variable Y;
The steering torque T, and the dependent variable with Y, a steering control apparatus according to claim 3, characterized in that to determine the control amount u _h of the steering actuator. The steering amount according to claim 6, wherein a control amount u _h of the steering actuator is determined using the steering torque T, the dependent variable Y, and a time derivative dF _h / dt of the estimated value F _h. Control device. A control amount u _{h of} the steering actuator, or
Control amount u _{r of the} steering actuator
The steering control device according to any one of claims 1 to 7, further comprising a steering gear ratio varying unit that changes the vehicle speed according to the vehicle speed V. Having the steering torque T or the steering angle θ as an independent variable λ (−a ≦ λ ≦ a),
“Λ> 0 => F (λ) ≦ 0” and “F (−λ) = − F (λ)” are satisfied, and
A neutral sense compensation torque T _C represented by a function F (λ) having a substantially sinusoidal shape, a substantially sawtooth shape, or a substantially N-shape of one cycle is used to generate a control amount u _h of the steering actuator. The steering control device according to any one of claims 1 to 8, wherein the steering control device is included as one.

Images