Steering control device

Abstract

To provide a steering control device capable of further appropriately detecting that a steering wheel is in contact with an obstacle.SOLUTION: A steering control device calculates a steering torque command value which is a command value to a torque generated by a steering motor by executing feedback control of making a target angle of a shaft rotating interlocking with a steering operation of a vehicle steering wheel follow an actual angle. The steering control device includes: a proportional control section which calculates a torque command value of a value proportional to a deviation by executing proportional calculation for a deviation of an actual angle to the target angle of the shaft; a differential control section which calculates a torque command value proportional to a differential value of the deviation by executing differential calculation for the deviation; an adder for calculating the steering torque command value by adding a first torque command value and a second torque command; and a determination section 102 for determining whether or not the steering wheel is in contact with an obstacle on the basis of a torque command value Tp1 calculated by the proportional control section.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a steering control device. [Background technology]

[0002] Conventionally, there has been a so-called steer-by-wire steering device in which power transmission between the steering wheel and the steered wheels is separated. The steering device has a reaction motor, which is a source of generating a steering reaction force applied to the steering shaft, and a steering motor, which is a source of generating a steering force that steers the steered wheels. When the vehicle is traveling, a control device of the steering device generates a steering reaction force by controlling the power supply to the reaction motor, and steers the steered wheels by controlling the power supply to the steering motor.

[0003] In a steering system, it is possible that a situation may arise in which it becomes difficult to steer the steered wheels toward the further turning side, such as when the steered wheels hit an obstacle such as a curb while the vehicle is stationary. In such a situation, the steering system control device attempts to make the turning angle of the steered wheels follow the steering angle of the steering wheel. As a result, an excessive current is supplied to the steering motor, which may cause the steering motor or its drive circuit to overheat.

[0004] Therefore, for example, the control device in Patent Document 1 determines that the steered wheels are in contact with an obstacle when predetermined determination conditions are met. The determination conditions include, for example, whether the value of the current supplied to the steering motor remains equal to or greater than a current threshold for a predetermined period of time. When it is determined that the steered wheels are in contact with an obstacle, the control device executes predetermined control to prevent the steering motor from overheating and to notify the driver that the steered wheels are in contact with an obstacle. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-138606 Summary of the Invention [Problem to be solved by the invention]

[0006] In order for the steering device control device to properly execute the above-mentioned predetermined control, it is required to more properly detect that the steered wheels are in contact with an obstacle. [Means for solving the problem]

[0007] A steering control device that can solve the above problem calculates a target angle of a shaft that rotates in conjunction with the steering operation of the steered wheels in accordance with the steering state of the steering wheel, in order to control power supply to a steering motor that generates a steering force for turning the steered wheels of a vehicle whose power transmission is decoupled from the steering wheel, and calculates a steering torque command value that is a command value for the torque generated by the steered motor by executing feedback control that causes the actual angle to track the target angle. The steering control device has a proportional control unit that calculates a first torque command value proportional to a deviation of the actual angle of the shaft from the target angle by performing a proportional operation on the deviation, a differential control unit that calculates a second torque command value proportional to a differential value of the deviation by performing a differential operation on the deviation, an adder that calculates the turning torque command value by adding the first torque command value and the second torque command value, and a determination unit that determines whether the steered wheels are hitting an obstacle based on the first torque command value.

[0008] The steering motor is supplied with a current corresponding to a steering torque command value that reflects both the first torque command value and the second torque command value. It is conceivable to determine whether the steered wheels are hitting an obstacle based on the value of the current supplied to the steering motor. This is because the more the driver tries to turn the steered wheels when they are hitting an obstacle, the greater the deviation between the target angle of the shaft, based on the steering state of the steering wheel, and the actual angle. In this case, however, there is a risk that the contact of the steered wheels with the obstacle will not be properly detected. This is because the differential control unit is sensitive to changes in the deviation between the target angle of the shaft and the actual angle, and therefore the value of the current supplied to the steering motor will fluctuate in response to slight fluctuations in the target angle.

[0009] In this regard, with the above configuration, the determination unit determines whether the steered wheels are hitting an obstacle based on the first torque command value calculated by the proportional control unit. Because the first torque command value is not affected by the operation of the differential control unit, it is possible to more appropriately determine whether the steered wheels are hitting an obstacle compared to determining whether the steered wheels are hitting an obstacle based on the value of the current supplied to the steering motor.

[0010] In the above steering control device, the determination unit may determine whether the steered wheels are hitting an obstacle based on a current command value obtained by converting the first torque command value into a current value of the steering motor.

[0011] With this configuration, the current command value obtained by converting the first torque command value into a current value for the steering motor is not affected by the operation of the differential control unit, so it is possible to more accurately determine whether the steered wheels are hitting an obstacle compared to determining whether the steered wheels are hitting an obstacle based on the value of the current supplied to the steering motor.

[0012] In the above steering control device, the determination unit may acquire the first torque command value by performing a proportional calculation on the deviation itself. With this configuration, the first torque command value calculated by the determination unit itself is not affected by the operation of the differential control unit, making it possible to more accurately determine whether the steered wheels are hitting an obstacle compared to determining whether the steered wheels are hitting an obstacle based on the value of the current supplied to the steering motor.

[0013] In the above steering control device, the determination unit may determine whether the steered wheels are hitting an obstacle by comparing the absolute value of the current command value with a current threshold value.

[0014] According to this configuration, it is possible to simply compare the absolute value of the current command value with the current threshold value, and therefore it is possible to easily determine whether the steered wheels are hitting an obstacle. In the above steering control device, the judgment unit may be configured to judge that the steered wheels are hitting an obstacle when a state in which the absolute value of the current command value is equal to or greater than the current threshold value continues for a time threshold value or longer.

[0015] With this configuration, if the absolute value of the current command value momentarily reaches a value equal to or greater than the current threshold value, it is possible to suppress the erroneous determination that the steered wheels are hitting an obstacle, thereby making it possible to more accurately determine whether the steered wheels are hitting an obstacle.

[0016] In the above steering control device, the judgment unit may be configured to judge that the steered wheels are hitting an obstacle when a state in which the absolute value of the current command value is equal to or greater than the current threshold value and the angular velocity obtained by differentiating the actual angle of the shaft is equal to or less than the angular velocity threshold value continues for a time threshold value or more.

[0017] The steering control device may further include an integral control unit that calculates a third torque command value that is proportional to the integral value of the deviation by performing an integral operation on the deviation. In this case, the adder calculates the turning torque command value by adding the first torque command value, the second torque command value, and the third torque command value.

[0018] With this configuration, the integral control unit accumulates past deviations through time integration and operates to continuously eliminate deviations. This reduces the steady-state deviation between the target angle and the actual angle that occurs due to the proportional calculation of the proportional control unit. This improves the ability of the actual angle to track the target angle of the shaft.

[0019] The above steering control device may further include a reaction force control unit that controls power supply to a reaction force motor that generates a steering reaction force applied to the steering wheel, based on a reaction torque command value calculated in accordance with the steering state of the steering wheel. The reaction force control unit may include a basic axial force calculation unit that calculates a basic axial force that is a basic axial force acting on a steering shaft that steers the turnable wheels, a limiting axial force calculation unit that calculates a limiting axial force for virtually limiting the operation of the steering wheel when the determination unit determines that the turnable wheels are hitting an obstacle, and a final axial force that is a final axial force to be reflected in the reaction torque command value, based on the basic axial force and the limiting axial force.

[0020] With this configuration, when the determination unit determines that the steered wheels are hitting an obstacle, the limit axial force calculation unit calculates a limit axial force for virtually limiting the operation of the steering wheel. This limit axial force is reflected in the final axial force and, ultimately, in the reaction torque command value, so that a steering reaction force for virtually limiting the operation of the steering wheel is applied to the steering wheel. Therefore, the driver can recognize that the steered wheels are hitting an obstacle through a feel via the steering wheel. [Effects of the Invention]

[0021] According to the steering control device of the present invention, it is possible to more appropriately detect that the steered wheels are in contact with an obstacle. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a configuration diagram of a steer-by-wire steering device in which an embodiment of a steering control device is mounted. [Figure 2] FIG. 1 is a block diagram of an embodiment of a steering control device. [Figure 3] FIG. 2 is a block diagram of a pinion angle feedback control unit according to an embodiment. [Figure 4] FIG. 2 is a block diagram of a reaction torque command value calculation unit according to the embodiment. [Figure 5] FIG. 2 is a block diagram of an axial force calculation unit according to an embodiment. [Figure 6] FIG. 4 is a block diagram of a second limit axial force calculation unit in one embodiment. [Figure 7] 10 is a graph showing the relationship between deviation and second limiting axial force in one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0023] An embodiment of a steering control device will be described below. <Overall structure> As shown in Fig. 1, the control target of the steering control device 1 is a steer-by-wire steering device 2. The steering device 2 has a steering mechanism 3 and a turning mechanism 4. The steering mechanism 3 is a mechanical part that is steered by a driver via a steering wheel 5. The turning mechanism 4 is a mechanical part that steers steerable wheels 6 of the vehicle in response to the steering of the steering wheel 5.

[0024] The steering mechanism 3 has a steering shaft 11, a reaction motor 12, and a reducer 13. The steering wheel 5 is connected to the steering shaft 11 so as to be rotatable integrally therewith. The reaction motor 12 is a source of a steering reaction force applied to the steering shaft 11. The steering reaction force is a force in the opposite direction to the steering direction of the steering wheel 5. The reaction motor 12 is, for example, a three-phase brushless motor. The reducer 13 decelerates the rotation of the reaction motor 12 and transmits the decelerated rotation to the steering shaft 11.

[0025] The steering mechanism 4 has a pinion shaft 21, a steered shaft 22, and a housing 23. The housing 23 rotatably supports the pinion shaft 21. The housing 23 also accommodates the steered shaft 22 so that it can reciprocate. The pinion shaft 21 is arranged to intersect with the steered shaft 22. Pinion teeth 21a of the pinion shaft 21 mesh with rack teeth 22a of the steered shaft 22. Tie rods 25 are connected to both ends of the steered shaft 22 via rack ends 24 made up of ball joints. The ends of the tie rods 25 are connected to knuckles (not shown) to which the steered wheels 6 are assembled.

[0026] The steering mechanism 4 comprises a steering motor 31, a transmission mechanism 32, and a conversion mechanism 33. The steering motor 31 is a source of the steering force applied to the steering shaft 22. The steering force is a force for steering the steered wheels 6. The steering motor 31 is, for example, a three-phase brushless motor. The transmission mechanism 32 is, for example, a belt transmission mechanism. The transmission mechanism 32 transmits the rotation of the steering motor 31 to the conversion mechanism 33. The conversion mechanism 33 is, for example, a ball screw mechanism. The conversion mechanism 33 converts the rotation transmitted via the transmission mechanism 32 into axial movement of the steering shaft 22.

[0027] The steered shaft 22 moves in the axial direction, and the steered angle θ of the steered wheels 6 wThe pinion teeth 21a of the pinion shaft 21 are engaged with the rack teeth 22a of the steered shaft 22, and therefore rotate in conjunction with the movement of the steered shaft 22. The pinion shaft 21 is a shaft that rotates in conjunction with the steering operation of the steered wheels 6.

[0028] The steering control device 1 controls the operation of the reaction force motor 12 and the steering motor 31. The steering control device 1 has a processing circuit including any one of the following three components A1, A2, A3.

[0029] A1. One or more processors that operate according to a computer program, which is software. The processor includes a CPU (central processing unit) and memory. A2. One or more dedicated hardware circuits, such as an application specific integrated circuit (ASIC), that perform at least some of the processing. The ASIC includes a CPU and memory.

[0030] A3. A hardware circuit that combines configurations A1 and A2. The memory is a computer-readable medium that stores a program that describes processes or instructions for the computer. In this embodiment, the computer is a CPU. The memory includes RAM (random access memory) and ROM (read only memory). The CPU executes the program stored in the memory at a predetermined calculation cycle to perform various controls.

[0031] The steering control device 1 receives detection results from sensors mounted on the vehicle, including a vehicle speed sensor 41, a torque sensor 42, a rotation angle sensor 43, and a rotation angle sensor 44. The vehicle speed sensor 41 detects the vehicle speed V. The torque sensor 42 is provided on the steering wheel 5 side, with the connection part of the steering shaft 11 to the reducer 13 as a reference. The torque sensor 42 detects the steering torque Th applied to the steering shaft 11. The steering torque Th is calculated based on the amount of twist of a torsion bar 42a provided on the steering shaft 11. The rotation angle sensor 43 is provided on the reaction force motor 12. The rotation angle sensor 43 detects the rotation angle θ of the reaction force motor 12. a The rotation angle sensor 44 is provided on the steering motor 31. The rotation angle sensor 44 detects the rotation angle θ of the steering motor 31. b Detect.

[0032] Steering torque Th, rotation angle θ of reaction motor 12 a , and the rotation angle θ of the steering motor 31 b is, for example, a positive value when the steering wheel 5 is steered to the right, and is a negative value when the steering wheel 5 is steered to the left.

[0033] Steering control device 1 controls reaction force motor 12 and turning motor 31 based on the detection results of various sensors. Steering control device 1 controls the power supply to reaction force motor 12 so that reaction force motor 12 generates a steering reaction force corresponding to steering torque Th. Steering control device 1 controls the power supply to turning motor 31 so that steered wheels 6 are steered according to the steering state of steering wheel 5.

[0034] <Configuration of steering control device 1> Next, the configuration of the steering control device 1 will be described. As shown in FIG. 2, the steering control device 1 has a reaction force control section 50 that performs reaction force control, and a steering control section 60 that performs steering control.

[0035] The reaction force control unit 50 includes a steering angle calculation unit 51 , a reaction force torque command value calculation unit 52 , and an energization control unit 53 . The steering angle calculation unit 51 calculates the rotation angle θ of the reaction force motor 12 detected through the rotation angle sensor 43. aBased on this, the steering angle θ of the steering wheel 5 s Calculate the following.

[0036] The reaction torque command value calculation unit 52 calculates the reaction torque command value T based on the steering torque Th and the vehicle speed V. * Calculate the reaction torque command value T * is a target value of the steering reaction force to be generated by the reaction force motor 12. The steering reaction force is a torque in the direction opposite to the steering direction of the steering wheel 5. The larger the absolute value of the steering torque Th is and the slower the vehicle speed V is, the greater the reaction torque command value T * The absolute value of becomes larger.

[0037] The power supply control unit 53 determines the reaction torque command value T * Specifically, the power supply control unit 53 supplies the reaction force motor 12 with power according to the reaction force torque command value T * The current control unit 53 calculates a current command value for the reaction force motor 12 based on the current I generated in the power supply path through a current sensor 54 provided in the power supply path for the reaction force motor 12. a Detect the value of the current I a The value of is the value of the current supplied to the reaction motor 12. The current control unit 53 calculates the current command value and the current I a The deviation from the value of the reaction torque command value T is calculated, and the power supply to the reaction motor 12 is controlled so as to eliminate the deviation. * A torque corresponding to the

[0038] The steering control unit 60 has a pinion angle calculation unit 61 , a target pinion angle calculation unit 62 , a pinion angle feedback control unit 63 , and an energization control unit 64 . The pinion angle calculation unit 61 calculates the rotation angle θ of the steering motor 31 detected through the rotation angle sensor 43. b Based on this, the pinion angle θ p Calculate the pinion angle θ p is the rotation angle of pinion shaft 21. Steering motor 31 and pinion shaft 21 are linked via transmission mechanism 32, conversion mechanism 33, and steering shaft 22. Therefore, the rotation angle θ of steering motor 31b and pinion angle θ p By utilizing this correlation, the rotation angle θ of the steering motor 31 is b From pinion angle θ p The pinion shaft 21 is meshed with the steering shaft 22. Therefore, the pinion angle θ p There is also a correlation between the pinion angle θ and the amount of movement of the steering shaft 22. p is the steering angle θ of the steered wheels 6 w This is a value that reflects the

[0039] The target pinion angle calculation unit 62 calculates the steering angle θ calculated by the steering angle calculation unit 51. s Based on the target pinion angle θ p * The target pinion angle calculation unit 62 calculates the target pinion angle θ so as to realize a steering angle ratio set according to product specifications, etc. p * The steering angle ratio is calculated by the steering angle θ s steering angle θ w is the ratio of

[0040] The target pinion angle calculation unit 62 sets a steering angle ratio according to the vehicle running state, such as the vehicle speed V, and calculates the target pinion angle θ according to the set steering angle ratio. p * As the vehicle speed V decreases, the target pinion angle calculation unit 62 calculates the steering angle θ s steering angle θ w The target pinion angle θ p * As the vehicle speed V increases, the target pinion angle calculation unit 62 calculates the steering angle θ s steering angle θ w The target pinion angle θ p * The target pinion angle calculation unit 62 calculates the steering angle θ s The correction angle for the steering angle θ is calculated. sBy adding to the target pinion angle θ according to the steering angle ratio p * Calculate the following.

[0041] Depending on the product specifications, the target pinion angle calculation unit 62 may calculate the target pinion angle θ so that the steering angle ratio becomes "1:1" regardless of the running state of the vehicle. p * The following may be calculated.

[0042] The pinion angle feedback control unit 63 receives the target pinion angle θ calculated by the target pinion angle calculation unit 62. p * , and the pinion angle θ calculated by the pinion angle calculation unit 61 p The pinion angle feedback control unit 63 receives the pinion angle θ p is the target pinion angle θ p * The pinion angle θ p Through the feedback control of the steering torque command value T p * Calculate the steering torque command value T p * is the target value of the steering force.

[0043] The power supply control unit 64 controls the steering torque command value T p * Specifically, the power supply control unit 64 supplies the steering motor 31 with electric power according to the steering torque command value T p * The current control unit 64 calculates a current command value for the steering motor 31 based on the current I generated in the power supply path through a current sensor 65 provided in the power supply path for the steering motor 31. b Detect the value of the current I b The value of is the value of the current supplied to the steering motor 31. The current control unit 64 calculates the current command value and the current I b The deviation from the value of the steering torque command value T is calculated and the power supply to the steering motor 31 is controlled so as to eliminate the deviation. p * A torque corresponding to the

[0044] <Configuration of pinion angle feedback control unit 63> Next, the configuration of the pinion angle feedback control unit 63 will be described. As shown in FIG. 3, the pinion angle feedback control unit 63 has a subtractor 71, a proportional control unit 72, an integral control unit 73, a differential control unit 74, and an adder 75.

[0045] The subtractor 71 subtracts the target pinion angle θ calculated by the target pinion angle calculation unit 62. p * and the pinion angle θ calculated by the pinion angle calculation unit 61. p The subtractor 71 takes in the target pinion angle θ p * and pinion angle θ p The deviation Δθ is the difference between p Calculate the following.

[0046] The proportional control section 72 calculates the deviation Δθ calculated by the subtractor 71. p By performing a proportional operation on the deviation Δθ p Torque command value T proportional to p1 The proportional control section 72 calculates the deviation Δθ p By multiplying by the proportional gain, the torque command value T p1 The proportional gain is a constant that is tuned to achieve the desired control characteristics.

[0047] The integral control unit 73 calculates the deviation Δθ calculated by the subtractor 71. p By performing an integral operation on p The torque command value T is proportional to the integral value of p2 The integral control unit 73 calculates the deviation Δθ p is integrated over time, and the integral value is multiplied by the integral gain to obtain the torque command value T p2 The integral gain is a constant that is tuned to achieve the desired control characteristics.

[0048] The differential control unit 74 calculates the deviation Δθ calculated by the subtractor 71. p By performing a differential operation on p The torque command value T is proportional to the differential value of p3 The differential control section 74 calculates the deviation Δθ p is differentiated with respect to time, and the differential value is multiplied by the differential gain to obtain the torque command value T p3 The differential gain is a constant that is tuned to achieve the desired control characteristics.

[0049] The adder 75 calculates the torque command values ​​T p1 ,T p2 ,T p3 By adding p * Calculate the following. <Configuration of reaction torque command value calculation unit 52> Next, the configuration of the reaction torque command value calculation unit 52 will be described.

[0050] As shown in FIG. 4, the reaction torque command value calculation unit 52 includes an assist torque command value calculation unit 81, an axial force calculation unit 82, and a subtractor 83. The assist torque command value calculation unit 81 calculates the steering torque T h , and the vehicle speed V detected by the vehicle speed sensor 41. The assist torque command value calculation unit 81 calculates the steering torque T h and vehicle speed V, an assist torque command value T1 is calculated. The assist torque command value T1 corresponds to the target value of the assist torque when the steering device 2 is an electric power steering device. The assist torque is a force for assisting the steering of the steering wheel 5. The assist torque command value T1 is a torque in the same direction as the steering direction of the steering wheel 5. The steering torque T h The larger the absolute value of the assist torque command value T1 is and the slower the vehicle speed V is, the larger the absolute value of the assist torque command value T1 is.

[0051] The axial force calculation unit 82 calculates the pinion angle θ calculated by the pinion angle calculation unit 61.p , the current I of the steering motor 31 detected through the current sensor 65 b , the vehicle speed V detected by the vehicle speed sensor 41, and the steering angle θ calculated by the steering angle calculation unit 51. s The axial force calculation unit 82 takes in the pinion angle θ p , the current I of the steering motor 31 b value, vehicle speed V, and steering angle θ s Based on this, the axial force acting on the steered shaft 22 is calculated. The axial force calculation unit 82 converts the calculated axial force into a torque applied to the steering shaft 11, thereby calculating the axial force torque T2.

[0052] The subtractor 83 takes in the assist torque command value T1 calculated by the assist torque command value calculation unit 81 and the axial force torque T2 calculated by the axial force calculation unit 82. The subtractor 83 subtracts the axial force torque T2 from the assist torque command value T1 to obtain the reaction torque command value T * Calculate the following.

[0053] <Configuration of axial force calculation unit 82> Next, the configuration of the axial force calculation unit 82 will be described. As shown in FIG. 5, the axial force calculation unit 82 has a basic axial force calculation unit 90, a first limit axial force calculation unit 91, a second limit axial force calculation unit 92, a selection processing unit 93, an adder 94, and a converter 95.

[0054] The basic axial force calculation unit 90 calculates the basic axial force F0. The basic axial force F0 is a basic axial force acting on the steered shaft 22. The basic axial force F0 is one of the following three axial forces (B1, B2, B3).

[0055] B1. Angular axial force The angular axial force is, for example, the pinion angle θ p The basic axial force calculation unit 90 calculates the axial force according to the pinion angle θ p The angular axial force is calculated based on the pinion angle θ p The larger the absolute value of the angular axial force, and the slower the vehicle speed V, the larger the absolute value of the angular axial force.p The angular axial force increases linearly with the increase in the absolute value of the pinion angle θ p The angular axial force is an axial force that does not reflect the road surface condition or the force acting on the steered shaft 22 via the steered wheels 6.

[0056] B2.Current axial force The current axial force is the current I of the steering motor 31. b The basic axial force calculation unit 90 calculates the axial force according to the value of the current I b The current axial force is calculated based on the value of the current I of the steering motor 31. b The value of the target pinion angle θ p * and the actual pinion angle θ p That is, the current I of the steering motor 31 changes depending on the difference between the b The value of the current I of the steering motor 31 reflects the actual road surface condition acting on the steering wheels 6. b Based on the value of the basic axial force, it is possible to calculate an axial force that reflects the influence of the road surface condition. The basic axial force calculation unit 90 calculates a gain, which is a coefficient corresponding to the vehicle speed V, by multiplying the current I of the steering motor 31. b The current axial force is calculated by multiplying the value of

[0057] B3.Mixed axial force The mixed axial force is an axial force in which the angular axial force and the current axial force are mixed at a predetermined ratio. The basic axial force calculation unit 90 sets the distribution ratios for the angular axial force and the current axial force individually according to various state variables that reflect the vehicle behavior, road surface condition, or steering state. The basic axial force calculation unit 90 calculates the mixed axial force by adding up the values ​​obtained by multiplying the angular axial force and the current axial force by the distribution ratios that are individually set.

[0058] First limit axial force calculation unit 91 calculates first limit axial force F1. First limit axial force F1 is a so-called end axial force for virtually limiting the operation range of steering wheel 5. First limit axial force F1 is calculated from the viewpoint of rapidly increasing the torque generated by reaction motor 12 in the direction opposite to the steering direction when the operation position of steering wheel 5 approaches the limit position of the operation range or when steered shaft 22 approaches the limit position of the physical movement range.

[0059] The limit position of the operation range of steering wheel 5 is determined, for example, by the length of a spiral cable attached to steering wheel 5. The limit position of the physical movement range of steered shaft 22 is a position where so-called end contact occurs, physically restricting the movement range of steered shaft 22. End contact occurs when rack end 24, which is the end of steered shaft 22, abuts against housing 23.

[0060] The first limiting axial force calculation unit 91 calculates the steering angle θ s Or pinion angle θ p The first limiting axial force F1 is calculated based on the steering angle θ s Or pinion angle θ p The absolute value of the first limiting axial force F1 increases rapidly and linearly after the virtual end angle is reached. The virtual end angle is, for example, the steering angle θ s or the pinion angle θ corresponding to the limit position of the imaginary movable range of the steering shaft 22. p The virtual end angle is set to a value close to the virtual end angle. The virtual end angle is stored in the storage device of the steering control device 1.

[0061] The first limit axial force calculation unit 91 may calculate the virtual end angle in accordance with the vehicle speed V. For example, the first limit axial force calculation unit 91 calculates a virtual end angle with a smaller absolute value as the vehicle speed V increases.

[0062] The second limit axial force calculation unit 92 calculates the second limit axial force F2. The second limit axial force F2 is a so-called curb axial force that is used to notify the driver, for example, when the vehicle starts from a stopped state, that the steered wheels 6 are hitting an obstacle such as a curb, through a steering reaction force. The second limit axial force F2 is calculated from the viewpoint of rapidly increasing the torque generated by the reaction motor 12 in the direction opposite to the steering direction in order to restrict further turning steering or turning back steering when the steered wheels 6 are hitting an obstacle. The second limit axial force calculation unit 92 calculates the second limit axial force F2 by, for example, calculating the current I of the turning motor 31. b When it is determined that the steered wheels 6 are hitting an obstacle, the second limiting axial force calculation unit 92 calculates the steering angle θ s Based on this, the second limiting axial force F2 is calculated.

[0063] The selection processing unit 93 receives the first limit axial force F1 calculated by the first limit axial force calculation unit 91 and the second limit axial force F2 calculated by the second limit axial force calculation unit 92. The selection processing unit 93 selects the axial force with the larger absolute value from the first limit axial force F1 and the second limit axial force F2. The selection processing unit 93 sets the selected first limit axial force F1 or second limit axial force F2 as the final limit axial force F3 used in calculating the axial force torque T2.

[0064] The adder 94 calculates the final axial force F4 by adding the basic axial force F0 calculated by the basic axial force calculation unit 90 and the final limiting axial force F3 set by the selection processing unit 93. The final axial force F4 is the final axial force used in calculating the axial force torque T2. The adder 94 is a final axial force calculation unit that calculates the final axial force F4.

[0065] The converter 95 converts the final axial force F4 calculated by the adder 94 into a torque for the steering shaft 11, thereby calculating the axial force torque T2. <Concerns about the steering control device 1> The steering control device 1 has the following concerns: That is, the differential control section 74 does not calculate the target pinion angle θ p* and pinion angle θ p The deviation Δθ is the difference between p The torque command value T is proportional to the rate of change (slope) of p3 That is, the differential control section 74 calculates the deviation Δθ p The differential control section 74 predicts the direction of change of the deviation Δθ and controls the steering motor 31. The existence of the differential control section 74 has advantages such as suppressing vibrational response and improving response speed. p Therefore, the target pinion angle θ p * Even with a slight change in b Therefore, as described above, the value of the current I of the steering motor 31 changes. b When determining whether the steered wheels 6 are in contact with an obstacle based on the value of (a), there is a risk that contact of the steered wheels 6 with an obstacle may not be properly detected due to the characteristic operation of the differential control unit 74. Therefore, in this embodiment, the following configuration is adopted as the second limit axial force calculation unit 92.

[0066] <Configuration of the second limit axial force calculation unit 92> As shown in FIG. 6, the second limit axial force calculation unit 92 has a converter 101, a determination unit 102, an angle deviation calculation unit 103, and an axial force calculation unit 104.

[0067] The converter 101 converts the torque command value T p1 Torque command value T p1 is a command value for the torque generated by the steering motor 31. The converter 101 converts the torque command value T p1 is converted into the current value of the steering motor 31, the current command value I bp * The current command value I bp * is one component of the final current command value for the steering motor 31.

[0068] The determination unit 102 determines whether the steered wheels 6 are hitting an obstacle such as a curb. The determination unit 102 determines whether the steered wheels 6 are hitting an obstacle such as a curb. bp * The determination unit 102 determines that the steered wheels 6 have hit an obstacle when, for example, both of the following two determination conditions C1 and C2 are met.

[0069] C1.│I bp * │≧I th C2.T≧T th However, in the judgment condition C1, "I th " is the current threshold value. In the judgment condition C2, "T" is the elapsed time from the point when the judgment condition C1 is satisfied. "T th " is a time threshold value. The time threshold value is set to the time required to determine that the steered wheels 6 are in contact with an obstacle.

[0070] Current threshold I th is set based on the following viewpoint. That is, when the steered wheels 6 hit an obstacle, it is difficult to steer the steered wheels 6 toward the further turning side or the return side. In this state, when the steering wheel 5 is steered toward the further turning side or the return side, the target pinion angle θ p * increases, whereas the actual pinion angle θ p Therefore, when the steered wheels 6 are in contact with an obstacle, the more the steered wheels 6 are attempted to be steered, the more the target pinion angle θ p * and pinion angle θ p The deviation Δθ is the difference between p Therefore, the more the steered wheels 6 are tried to be steered while the steered wheels 6 are hitting an obstacle, the more the torque command value T p1 , and thus the current command value I bp * Therefore, the absolute value of the current command value I bp* The larger the absolute value of the current command value I, the higher the probability that the steered wheels 6 have hit an obstacle. bp * is a value indicating the degree of likelihood that the steered wheels 6 are hitting an obstacle. Based on this point of view, the current threshold I th is set by experiment or simulation.

[0071] The determination unit 102 sets the value of flag F according to the determination result of whether the steered wheels 6 have hit an obstacle. When it is determined that the steered wheels 6 have not hit an obstacle, that is, when the determination condition C1 is not satisfied, the determination unit 102 sets the value of flag F to "0." When it is determined that the steered wheels 6 have hit an obstacle, that is, when the determination condition C1 is satisfied, the determination unit 102 sets the value of flag F to "1."

[0072] The angle deviation calculation unit 103 calculates the value of the flag F set by the determination unit 102 and the steering angle θ calculated by the steering angle calculation unit 51. s Import. When the value of flag F is "1", the angle deviation calculation unit 103 calculates the steering angle θ at that time as shown in the following equation (D1). s is the reference angle θ s0 This is because the steering angle θ s is the start position of the second limiting axial force F2, and the steering angle θ at the time when it is determined that the steered wheels 6 are hitting an obstacle is s Steering angle θ based on s The intention is to generate a second limiting axial force F2 according to the amount of change in

[0073] θ s0 =θ s …(D1) When the value of the flag F is "0", the angle deviation calculation unit 103 calculates the steering angle θ s That is, when the value of the flag F is "0", the angle deviation calculation unit 103 does not hold the steering angle θ s is the reference angle θ s0Therefore, when the value of flag F is "0", the reference angle θ s0 is the steering angle θ at that time s is the same value as

[0074] The angle deviation calculation unit 103 calculates the angle deviation Δθ as shown in the following equation (D2). s Calculate the angle deviation Δθ s is the current steering angle θ s and the reference angle θ s0 This is the difference between Δθ s =θ s -θ s0 …(D2) When the value of flag F is "0", the angle deviation Δθ s The value of flag F is "0". This means that when the value of flag F is "0", theoretically, the reference angle θ s0 is the steering angle θ at that time s Because it has the same value as

[0075] When the value of flag F is "1", the angle deviation Δθ s is the reference angle θ s0 Steering angle θ based on s The value depends on the amount of change in The axial force calculation unit 104 calculates the angle deviation Δθ calculated by the angle deviation calculation unit 103. s The axial force calculation unit 104 takes in the angle deviation Δθ s The axial force calculation unit 104 calculates the second limit axial force F2 based on the above. The axial force calculation unit 104 calculates the second limit axial force F2 by using, for example, a limit axial force map. The limit axial force map is stored in a storage device of the steering control device 1.

[0076] As shown in the graph of FIG. 7, the limiting axial force map M1 has the angle deviation Δθ on the horizontal axis. s The limiting axial force map M1 has the following characteristics. That is, as shown by the characteristic line L1, the angle deviation Δθ s As the absolute value of the angle deviation Δθ increases, the absolute value of the second limiting axial force F2 becomes larger. sAs the absolute value of Δθ increases, the slope of the characteristic line L1 gradually increases. In other words, the characteristic line L1 is a curve with a positive, gradually increasing slope. The slope is determined by the angle deviation Δθ s is the rate of change in the absolute value of the second limiting axial force F2 relative to the absolute value of

[0077] The first limiting axial force F1 is s Or pinion angle θ p In contrast, the second limiting axial force F2 increases linearly and rapidly with the increase in the absolute value of the angle deviation Δθ s This is intended to reproduce the gradual increase in reaction force due to the elastic deformation of the tire when the steered wheels 6 hit an obstacle and then try to turn.

[0078] <Operation of the embodiment> This embodiment provides the following effects. When the operation position of the steering wheel 5 has not reached a position near the limit position of the operation range, or when the steered shaft 22 has not reached a position near the limit position of the physical movable range, the first limit axial force calculation unit 91 does not calculate the first limit axial force F1. Furthermore, when it is not determined that the steered wheels 6 are hitting an obstacle, the second limit axial force calculation unit 92 does not calculate the second limit axial force F2. In other words, the value of the first limit axial force F1 and the value of the second limit axial force F2 are both "0". Therefore, the basic axial force F0 calculated by the basic axial force calculation unit 90 becomes the final axial force F4. The axial force torque T2 obtained by converting the final axial force F4 into torque is the reaction torque command value T * By reflecting the steering reaction force according to the vehicle behavior or road surface condition to the steering wheel 5, the driver can grasp the vehicle behavior or road surface condition by feeling the steering reaction force via the steering wheel 5 as a response.

[0079] When the operation position of the steering wheel 5 approaches the limit position of the operation range, or when the steered shaft 22 approaches the limit position of the physical movable range, the first limit axial force calculation unit 91 calculates the steering angle θs Or pinion angle θ p Therefore, the value obtained by adding the first limit axial force F1 to the basic axial force F0 becomes the final axial force F4. The axial force torque T2 obtained by converting the final axial force F4 into torque is the reaction torque command value T * Therefore, the driver must turn the steering wheel at a constant angle of θ s It becomes difficult to operate the steering wheel 5 in a direction in which the absolute value of θ becomes larger. Therefore, by feeling a sense of resistance through the steering wheel 5, the driver can recognize that the steering wheel 5 has reached the limit position of the virtual operation range, or that the steered shaft 22 has approached the limit position of the physical movement range.

[0080] When further turning steering or turning back steering is performed under the condition that the steered wheels 6 are hitting an obstacle, the second limiting axial force calculation unit 92 calculates the angle deviation Δθ s The second limiting axial force F2 is calculated according to the angle deviation Δθ s is the steering angle θ at the time when it is determined that the steered wheels 6 are hitting an obstacle. s The reference angle θ s0 and the current steering angle θ s Therefore, the final axial force F4 is the sum of the basic axial force F0 and the second limit axial force F2. The axial force torque T2 obtained by converting the final axial force F4 into torque is the reaction torque command value T * The steering reaction force increases rapidly as a result of the steering wheel being reflected in the steering wheel 5. This makes it difficult for the driver to perform further steering or turning. Therefore, the driver can recognize that the steered wheels 6 have hit an obstacle by feeling a sense of hitting an obstacle as a response through the steering wheel 5.

[0081] The second limiting axial force F2 is smaller than the first limiting axial force F1 by the angle deviation Δθ sTherefore, the driver can feel a response through the steering wheel 5 that is closer to the actual situation in which the steered wheels 6 hit an obstacle and the driver tries to steer the steered wheels 6 further.

[0082] <Effects of the embodiment> This embodiment has the following advantages. (1) The differential control section 74 calculates the deviation Δθ p Therefore, the target pinion angle θ p * The torque command value T calculated by the differential control unit 74 is p3 , and thus the current I supplied to the steering motor 31 b Therefore, the value of the current I of the steering motor 31 changes. b When determining whether the steered wheels 6 are in contact with an obstacle based on the value of (a), there is a risk that the contact of the steered wheels 6 with an obstacle may not be detected appropriately.

[0083] In this regard, in the present embodiment, the second limit axial force calculation unit 92 calculates the torque command value T p1 Based on the current command value I bp * is calculated, and the calculated current command value I bp * Since the differential control section 74 is not affected by the characteristic operation of the differential control section 74, the current I b This makes it possible to more accurately determine whether the steered wheels 6 have hit an obstacle compared to when determining whether the steered wheels 6 have hit an obstacle based on the value of .

[0084] (2) The second limit axial force calculation unit 92 calculates the current command value I bp * and the current threshold I th By comparing the current command value I with the current command value I, it is determined whether the steered wheels 6 are hitting an obstacle. bp * and the current threshold I thSince it is only necessary to compare the detected value with the detected value, it is possible to easily determine whether the steered wheels 6 are hitting an obstacle.

[0085] (3) The second limit axial force calculation unit 92 calculates the current command value I bp * The absolute value of is the current threshold I th The state where this is equal to or greater than the time threshold T th If the above continues, it is determined that the steered wheels 6 are hitting an obstacle. bp * The absolute value of is the current threshold I th When the above value is reached, it is possible to suppress the erroneous determination that the steered wheels 6 have hit an obstacle, and therefore it is possible to more accurately determine whether the steered wheels 6 have hit an obstacle.

[0086] <Other embodiments> This embodiment may be modified as follows. The second limit axial force calculation unit 92 may determine whether the following determination condition C3 is met in addition to the two previous determination conditions C1 and C2. In this way, it is possible to more accurately determine whether the steered wheels 6 are hitting an obstacle.

[0087] C3.│ω p │≦ω th However, "ω p " is the pinion angular velocity. "ω th " is the angular velocity threshold. The pinion angular velocity is obtained as follows. That is, as shown by the two-dot chain line in Fig. 6, the second limit axial force calculation unit 92 has a differentiator 105. The differentiator 105 calculates the pinion angle θ calculated by the pinion angle calculation unit 61. p The pinion angular velocity is calculated by differentiating

[0088] Angular velocity threshold ω this set based on the following viewpoint: In other words, it is difficult to steer the steerable wheels 6 when the steerable wheels 6 are hitting an obstacle. For this reason, the steering speed of the steerable wheels 6, and therefore the pinion angular velocity ω p The smaller the absolute value of ω, the higher the probability that the steered wheels 6 have hit an obstacle. p is a value indicating the degree of likelihood that the steered wheels 6 are hitting an obstacle. th is set by experiment or simulation, taking into consideration tolerances due to noise from the rotation angle sensor 44 and the like.

[0089] The second limiting axial force calculation unit 92 may determine whether the steered wheels 6 are hitting an obstacle based only on the determination condition C1. The second limit axial force calculation unit 92 calculates the current command value I bp * and the current threshold I th Instead of comparing the torque command value T p1 The torque command value T may be compared with a torque threshold value to determine whether the steered wheels 6 are hitting an obstacle. p1 is not affected by the operation of the differential control section 74. Therefore, the current I supplied to the steering motor 31 b In this case, it is possible to more appropriately determine whether the steered wheels 6 are hitting an obstacle compared to when determining whether the steered wheels 6 are hitting an obstacle based on the value of . In this case, a configuration in which the converter 101 is omitted can be adopted as the second limit axial force calculation unit 92.

[0090] The second limit axial force calculation unit 92 calculates the torque command value T p1 Instead, the deviation Δθ p In this case, the second limit axial force calculation unit 92 has a calculation unit equivalent to the proportional control unit 72. The calculation unit calculates the deviation Δθ p By multiplying by the proportional gain, the torque command value T p1The determination unit 102 calculates the torque command value T p1 Based on this, it is determined whether the steered wheels 6 are hitting an obstacle.

[0091] The pinion angle feedback control unit 63 may have a calculation unit that calculates a torque command value for damping. p The torque command value for damping is calculated by multiplying the difference Δθ by the gain for damping. p As the value of increases, the deviation Δθ p The slope, which is the rate of change of gain with respect to the deviation Δθ p The adder 75 calculates the torque command value T p1 and the torque command value T calculated by the integral control unit 73. p2 and the torque command value T calculated by the differential control unit 74. p3 and the torque command value for damping are added together to obtain the steering torque command value T p * Calculate the steering torque command value T p * The torque command value for damping is reflected in the deviation Δθ p The steering torque command value T p * can be stabilized.

[0092] The pinion angle feedback control unit 63 may have a configuration in which the integral control unit 73 is omitted. The pinion angle feedback control unit 63 executes PD control (proportional differential control).

[0093] The axial force calculation unit 82 may be configured without the first limit axial force calculation unit 91. In this case, for example, the steering mechanism 3 may be provided with a stopper mechanism that mechanically limits the operation range of the steering wheel 5.

[0094] The steering device 2 may have a clutch. In this case, the steering shaft 11 and the pinion shaft 21 are connected via the clutch. The clutch is, for example, an electromagnetic clutch that connects and disconnects power by turning on and off current to an exciting coil. The steering control device 1 executes an on / off control that switches the clutch on and off. When the clutch is disengaged, the power transmission between the steering wheel 5 and the steered wheels 6 is mechanically disconnected. When the clutch is engaged, the power transmission between the steering wheel 5 and the steered wheels 6 is mechanically connected.

[0095] The left and right steerable wheels 6 may be able to be steered independently of each other. In this case, the steering device 2 has two steering motors corresponding to the left and right steerable wheels 6. The steering control device 1 steers each steerable wheel 6 independently by controlling the steering motors corresponding to each steerable wheel 6. [Explanation of symbols]

[0096] 1...Steering control device 5...Steering wheel 6...Steering wheel 12...Reaction motor 21...Pinion shaft (shaft) 31...Steering motor 50...Reaction force control unit 72...Proportional control section 73...Integral control section 74...Differential control section 75...adder 90...Basic axial force calculation section 92...Second limit axial force calculation unit (limit axial force calculation unit) 94...Adder (final axial force calculation section) 102…Judgment section F0…Basic axial force F2: Second limiting axial force (limiting axial force) F4…Final axial force I b …Current value of steering motor I bp * …Current command value I th …Current threshold Tp * …Steering torque command value T p1 ...torque command value (first torque command value) T p2 ...Torque command value (third torque command value) T p3 ...Torque command value (second torque command value) T * …Reaction torque command value T th …time threshold θ p * …Target pinion angle (target angle) θ p …Pinion angle (actual angle) Δθ p …deviation ω…angular velocity ω th …Angular velocity threshold

Claims

1. 1. A steering control device that calculates a target angle of a shaft that rotates in conjunction with the steering operation of the steered wheels in accordance with a steering state of the steering wheel, in order to control power supply to the steering motor that generates a steering force for turning the steered wheels of a vehicle in which power transmission between the steering motor and the steering wheel is separated, and calculates a steering torque command value that is a command value for torque generated by the steering motor by executing feedback control that makes an actual angle follow the target angle, a proportional control unit that calculates a first torque command value proportional to a deviation of an actual angle of the shaft from a target angle by performing a proportional calculation on the deviation; a differential control unit that performs a differential operation on the deviation to calculate a second torque command value that is proportional to a differential value of the deviation; an adder that calculates the turning torque command value by adding the first torque command value and the second torque command value; a determination unit that determines whether the steered wheels are hitting an obstacle based on the first torque command value, the determination unit is configured to determine whether the steered wheels are hitting an obstacle by comparing an absolute value of a current command value obtained by converting the first torque command value into a current value of the steered motor with a current threshold value, The steering control device is configured to determine that the steered wheels are hitting an obstacle when a state in which the absolute value of the current command value is equal to or greater than the current threshold value and the angular velocity obtained by differentiating the actual angle of the shaft is equal to or less than the angular velocity threshold value continues for a time threshold value or more.

2. A steering control device as described in Claim 1, wherein the judgment unit obtains the first torque command value by performing a proportional calculation on the deviation itself.

3. an integral control unit that calculates a third torque command value proportional to an integral value of the deviation by performing an integral calculation on the deviation, 3. The steering control device according to claim 1, wherein the adder calculates the turning torque command value by adding the first torque command value, the second torque command value, and the third torque command value.

4. a reaction force control unit that controls power supply to a reaction force motor that generates a steering reaction force applied to the steering wheel based on a reaction force torque command value calculated in accordance with a steering state of the steering wheel, The reaction force control unit includes a basic axial force calculation unit that calculates a basic axial force that is a basic axial force acting on a steering shaft that steers the steering wheels; a limiting axial force calculation unit that calculates a limiting axial force for virtually limiting the operation of the steering wheel when the determination unit determines that the steered wheels are hitting an obstacle; A final axial force calculation unit that calculates a final axial force, which is a final axial force to be reflected in the reaction torque command value, based on the basic axial force and the limiting axial force. The steering control device according to any one of claims 1 to 3.

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