Steering equipment

Abstract

A steering device is provided. The steering device (10) includes: a mechanism that rotates a rotating wheel (16); a first motor that generates a driving force supplied to the mechanism; and a control device (50). The control device includes: a first calculation circuit (62) that calculates a first limit value to which the current to be supplied to the first motor is limited in a specific case; a determination circuit (85) that determines whether the rotating wheel is in contact with an obstacle; a second calculation circuit (91) that calculates a second limit value to which the current to be supplied to the first motor is limited when the determination circuit determines that the rotating wheel is in contact with the obstacle; and a third calculation circuit (93) that calculates a threshold value to be used by the determination circuit based on the smaller limit value of the first limit value and the second limit value.

Description

Technical Field

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

[0002] There is a so-called steer-by-wire type steering device in which dynamic power transmission between a steering wheel and a rotating wheel is cut off. The steering device includes: a reaction motor as a generation source of a steering reaction force supplied to a steering shaft; and a rotating motor as a generation source of a rotating force for rotating the rotating wheel. When the vehicle is running, a control device of the steering device generates a steering reaction force by controlling the power supply of the reaction motor, and rotates the rotating wheel by controlling the power supply of the rotating motor.

[0003] The steering device may enter a situation where it is difficult to rotate the rotating wheel to the steering increase side, for example, due to a situation where the rotating wheel abuts against a curb during stationary steering. At this time, the control device of the steering device attempts to make the rotation angle of the rotating wheel follow the steering angle of the steering wheel. As a result, an excessive current is supplied to the rotating motor, so that the rotating motor or a drive circuit for the rotating motor may overheat.

[0004] Thus, for example, the control device in Japanese Patent Application Publication No. 2006-111099 determines that the rotating wheel is in contact with an obstacle when a prescribed determination condition is satisfied. For example, the determination condition includes the following condition: the actual current value supplied to the rotating motor is continuously equal to or greater than the current threshold value for a predetermined time. When determining that the rotating wheel is in contact with the obstacle, the control device performs control prescribed for suppressing overheating of the rotating motor. Summary of the invention

[0005] Some control devices have not only a function of suppressing overheating of the rotating motor due to contact of the rotating wheel with an obstacle, but also a function of suppressing overheating of the rotating motor caused by the temperature of the rotating wheel, for example. The control device monitors the temperature of the rotating motor, and when the temperature approaches the temperature of the overheating state, the control device limits the amount of current to be supplied to the rotating motor. The situation in which the control device limits the amount of current to be supplied to the rotating motor in this way may be a situation in which the power supply voltage has been reduced, or a situation in which the pull-in current has been increased.

[0006] Therefore, for example, when the turning wheel contacts an obstacle at the time of stationary steering for starting of the vehicle, the amount of current to be supplied to the steering motor can be limited before the current value of the turning motor reaches the current threshold value. In this case, since the current value of the turning motor does not reach the current threshold value, there is a problem that the contact of the turning wheel with the obstacle cannot be properly detected.

[0007] The present invention provides a steering device that can appropriately detect contact of a rotating wheel with an obstacle.

[0008] One aspect of the present invention is a steering device. The steering device includes a mechanism, a first motor and a control device. The mechanism is configured to rotate the rotating wheel of the vehicle. The first motor is configured to generate a driving force provided to the mechanism. The control device is configured to control the first motor according to the steering state. The control device includes a first calculation circuit, a determination circuit, a second calculation circuit, and a third calculation circuit. The first calculation circuit is configured to calculate a first limit value to which the current to be supplied to the first motor is limited under certain circumstances. The determination circuit is configured to determine whether the rotating wheel is in contact with an obstacle based on a comparison between the value of the current to be supplied to the first motor and a threshold value. The second calculation circuit is configured to calculate a second limit value to which the current to be supplied to the first motor is limited when the determination circuit determines that the rotating wheel is in contact with the obstacle. The third calculation circuit is configured to calculate a threshold value to be used by the determination circuit based on the smaller limit value of the first limit value and the second limit value.

[0009] With this configuration, in the case where the rotating wheel is in contact with an obstacle, the amount of current to be supplied to the motor is limited to a limiting value that is one of the first limiting value and the second limiting value and has a smaller absolute value. Thus, the temperature rise of the motor is suppressed. In addition, in the case where the rotating wheel is in contact with an obstacle, the threshold value to be used by the determination circuit is calculated based on the limiting value that is one of the first limiting value and the second limiting value and has a smaller absolute value. Therefore, even when the current value of the motor is limited, it is possible to suppress the threshold value from being set to a value larger than the current value of the motor. Therefore, it is possible to appropriately determine that the rotating wheel is in contact with the obstacle based on the comparison between the current value of the motor and the threshold value.

[0010] In the above-mentioned steering device, the third calculation circuit may be configured to calculate the threshold value having a value equal to a smaller limit value of the first limit value and the second limit value.

[0011] With this configuration, even when the current value of the motor is limited, the threshold value can be suppressed from being set to a value larger than the current value of the motor. In the above-mentioned steering device, the second calculation circuit can be configured to, when the determination circuit determines that the rotating wheel is in contact with the obstacle, reduce the second limit value from a maximum limit value to a minimum limit value, the maximum limit value being set based on a maximum current value that the first motor can apply without overheating, and the minimum limit value being set based on a minimum current value that the first motor can apply without overheating.

[0012] With this configuration, when the rotating wheel comes into contact with an obstacle, the second limit value is reduced from the maximum limit value to the minimum limit value. Therefore, the electric current of the motor can be limited to at least the minimum limit value as the second limit value.

[0013] In the above-mentioned steering device, the second calculation circuit may be configured to immediately restore the second limit value from the minimum limit value to the maximum limit value when the determination circuit cancels the determination that the turning wheel is in contact with the obstacle.

[0014] With this configuration, the period of time during which the rotation performance is reduced due to the limitation of the current of the motor for protecting the motor from overheating can be reduced to a minimum period. The steering device may also include a second motor. The mechanism may include a steering shaft and a rotating shaft, the steering shaft being configured to rotate together with the operation of the steering wheel, and the rotating shaft being arranged so that the dynamic power transmission between the steering wheel and the rotating shaft is isolated. The second motor may be a reaction motor configured to generate a steering reaction force based on a first command value calculated according to a steering state. The steering reaction force may be a torque provided to the steering shaft and in a direction opposite to the steering direction. The first motor may be a rotating motor configured to generate a rotational force based on a second command value calculated according to a steering state. The rotational force may be a torque provided to the rotating shaft and causing the rotating wheel to rotate.

[0015] In this case, the control device may include a limiting axial force calculation circuit, which is configured to, when the determination circuit determines that the rotating wheel is in contact with an obstacle, calculate the limiting axial force as the axial force of the rotating shaft as a control for notifying the driver that the rotating wheel is in contact with the obstacle, and the axial force of the rotating shaft is reflected in a first instruction value for the reaction motor to virtually limit the operation of the steering wheel.

[0016] With this configuration, in the case where the rotating wheel contacts an obstacle, the limiting axial force for virtually limiting the operation of the steering wheel is reflected in the first command value for the reaction motor. Thus, the driver has a contact feeling as a steering reaction force. Based on the feeling of the driver's hand through the steering wheel, the driver can recognize the situation where the rotating wheel contacts the obstacle. In addition, the driver's operation of the steering wheel can be virtually limited.

[0017] In the above-mentioned steering device, the control device may include: an ideal axial force calculation circuit, which is configured to calculate an ideal axial force, which is an idealized axial force of a rotating shaft based on a target rotation angle of a rotating body that rotates together with the rotating action of a rotating wheel; an estimated axial force calculation circuit, which is configured to calculate the axial force of the rotating shaft as an estimated axial force based on a current value of a rotating motor that reflects a vehicle behavior, a road surface condition, or a steering state; and a distribution calculation circuit, which is configured to calculate a mixed axial force as the axial force of the rotating shaft by mixing the estimated axial force with the ideal axial force based on the vehicle behavior, the road surface condition, or the steering state, and the axial force of the rotating shaft is reflected in a first instruction value for the reaction motor.

[0018] In this case, the allocation calculation circuit can be configured to, when the determination circuit determines that the rotating wheel is in contact with the obstacle, switch the axial force of the rotating shaft from the mixed axial force to the estimated axial force as a control for notifying the driver that the rotating wheel is in contact with the obstacle, and the axial force of the rotating shaft is reflected in the first instruction value for the reaction motor.

[0019] With this configuration, in a case where the rotating wheel is not in contact with an obstacle, a mixed axial force obtained by mixing an ideal axial force based on a target rotation angle of the rotating body and an estimated axial force based on a current value of a rotating motor according to vehicle behavior, etc. is reflected in a first command value for the reaction motor. Therefore, the reaction motor generates a driving force corresponding to the mixed axial force. On the other hand, in a case where the rotating wheel is in contact with an obstacle, only the estimated axial force is reflected in the first command value for the reaction motor. The estimated axial force reflects the vehicle behavior, road surface condition, or steering condition, and therefore, the motor generates a driving force corresponding to the axial force acting on the rotating shaft due to the contact of the rotating wheel with the obstacle. Therefore, the driver has a sense of contact as a steering reaction force through the steering wheel, and can recognize the situation where the rotating wheel is in contact with an obstacle.

[0020] With the steering device of the present invention, contact of the rotating wheel with an obstacle can be appropriately detected. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, wherein like reference numerals represent like elements, and in which:

[0022] Figure 1 is a configuration diagram of a steer-by-wire type steering device equipped with the steering device of the first embodiment;

[0023] Figure 2 is a control block diagram of the control device in the first embodiment;

[0024] Figure 3 is a control block diagram of a target steering angle calculation circuit in a first embodiment;

[0025] Figure 4 is a control block diagram of a vehicle model in the first embodiment;

[0026] Figure 5 is a control block diagram of a limit value calculation circuit in the first embodiment;

[0027] Figure 6 The figure above is a graph showing the relationship between the count value calculated in the limit value calculation circuit and the limit value in the first embodiment, Figure 6The figure below is a graph showing an exemplary timing when the value of the flag set by the determination circuit switches from "0" to "1" in the first embodiment;

[0028] Figure 7 is a graph showing the relationship between the limit current value for protection from overheating and the current threshold value for curb contact determination in the first embodiment; and

[0029] Figure 8 This is a control block diagram of the vehicle model in the second embodiment. DETAILED DESCRIPTION

[0030] First embodiment

[0031] A first embodiment in which the steering apparatus is applied to a steer-by-wire type steering apparatus will be described below.

[0032] like Figure 1 As shown, the steering device 10 of the vehicle includes a steering shaft 12 coupled to a steering wheel 11. The steering device 10 includes a Figure 1 The steering shaft 12 and the rotating shaft 14 extend in the left and right directions. The left rotating wheel 16 and the right rotating wheel 16 are respectively coupled to both ends of the rotating shaft 14 through the tie rod 15. The rotation angle θw of the rotating wheel 16 changes by the linear motion of the rotating shaft 14. The steering shaft 12 and the rotating shaft 14 constitute a steering mechanism.

[0033] Configuration for generating steering reaction forces: Reaction unit

[0034] The steering device 10 includes a reaction motor 31 (an example of a second motor), a speed reducer 32, a rotation angle sensor 33, and a torque sensor 34 as a configuration for generating a steering reaction force. Incidentally, the steering reaction force refers to a force (torque) acting in a direction opposite to the direction of the driver's operation of the steering wheel 11. By providing the steering reaction force to the steering wheel 11, a moderate feeling can be generated in the driver's hand.

[0035] The reaction motor 31 is a generation source of the steering reaction force. For example, a brushless motor having three phases (U, V, and W) is used as the reaction motor 31. The reaction motor 31 (more precisely, the rotating shaft of the reaction motor 31) is coupled to the steering shaft 12 through a speed reducer 32. The torque of the reaction motor 31 is provided to the steering shaft 12 as the steering reaction force.

[0036] The rotation angle sensor 33 is provided on the reaction motor 31. The rotation angle sensor 33 detects the rotation angle θa of the reaction motor 31. The rotation angle θa of the reaction motor 31 is used for calculation of the steering angle θs. The reaction motor 31 and the steering shaft 12 are interlocked with each other through the speed reducer 32. Therefore, the rotation angle θa of the reaction motor 31 has a correlation with the rotation angle of the steering shaft 12 and the steering angle θs which is the rotation angle of the steering wheel 11. Therefore, the steering angle θs can be estimated based on the rotation angle θa of the reaction motor 31.

[0037] The torque sensor 34 detects the steering torque Th applied to the steering shaft 12 by the rotation operation of the steering wheel 11. The torque sensor 34 is provided at a portion of the steering shaft 12 that is closer to the steering wheel 11 than the speed reducer 32.

[0038] Configuration for generating rotational forces: Rotational units

[0039] The steering apparatus 10 includes a turning motor 41 (an example of a first motor), a speed reducer 42 , and a rotation angle sensor 43 as a configuration for generating a turning force as a dynamic force for turning the turning wheel 16 .

[0040] The rotary motor 41 is a source of generating a rotational force. For example, a brushless motor having three phases is used as the rotary motor 41. The rotary motor 41 (more precisely, the rotating shaft of the rotary motor 41) is coupled to the pinion shaft 44 through the reducer 42. The pinion 44a of the pinion shaft 44 meshes with the rack 14b of the rotary shaft 14. The torque of the rotary motor 41 is provided to the rotary shaft 14 as a rotational force through the pinion shaft 44. In response to the rotation of the rotary motor 41, the rotary shaft 14 moves along the vehicle width direction (the left-right direction in the figure).

[0041] The rotation angle sensor 43 is arranged on the rotating motor 41. The rotation angle sensor 43 detects the rotation angle θb of the rotating motor 41. Incidentally, the steering device 10 includes a pinion shaft 13. The pinion shaft 13 is arranged to pass through the rotating shaft 14. The pinion 13a of the pinion shaft 13 is meshed with the rack 14a of the rotating shaft 14. The reason for providing the pinion shaft 13 is that the pinion shaft 13 supports the rotating shaft 14 in a housing (not shown) together with the pinion shaft 44. That is, by a supporting mechanism (not shown) provided in the steering device 10, the rotating shaft 14 is supported so that the rotating shaft 14 can move in the axial direction of the rotating shaft 14 and is pressed toward the pinion shafts 13, 44. Thus, the rotating shaft 14 is supported in the housing. However, the steering device 10 may be provided with another supporting mechanism that supports the rotating shaft 14 in the housing without using the pinion shaft 13.

[0042] Controls

[0043] The steering device 10 includes a control device 50. The control device 50 controls the reaction motor 31 and the rotation motor 41 based on the detection results of various sensors. In addition to the rotation angle sensor 33, the torque sensor 34, and the rotation angle sensor 43 described above, there is also a vehicle speed sensor 501 as a sensor. The vehicle speed sensor 501 provided in the vehicle detects the vehicle speed V as the running speed of the vehicle.

[0044] The control device 50 performs reaction force control by driving control of the reaction motor 31 to generate a steering reaction force corresponding to the steering torque Th. The control device 50 calculates a target steering reaction force based on the steering torque Th and the vehicle speed V, and calculates a target steering angle of the steering wheel 11 based on the calculated target steering reaction force, the steering torque Th and the vehicle speed V. The control device 50 calculates a steering angle correction amount by feedback control of the steering angle θs performed in such a manner that the actual steering angle θs follows the target steering angle, and calculates a steering reaction force command value by adding the calculated steering angle correction amount and the target steering reaction force. The control device 50 supplies a current required for generating a steering reaction force corresponding to the steering reaction force command value to the reaction motor 31.

[0045] The control device 50 performs rotation control according to the steering state through the drive control of the steering motor 41 to rotate the rotating wheel 16. The control device 50 calculates the pinion angle θp, which is the actual rotation angle of the pinion shaft 44, based on the rotation angle θb of the rotating motor 41 detected by the rotation angle sensor 43. The pinion angle θp is a value reflecting the rotation angle θw of the rotating wheel 16. The control device 50 calculates the target pinion angle using the target steering angle described above. Then, the control device 50 evaluates the deviation between the target pinion angle and the actual pinion angle θp, and controls the power supply to the rotating motor 41 so that the deviation is eliminated.

[0046] Detailed configuration of the control device

[0047] Next, the control device 50 will be described in detail. Figure 2 As shown, the control device 50 includes a reaction force control circuit 50a that performs reaction force control and a rotation control circuit 50b that performs rotation control.

[0048] Reaction force control circuit

[0049] The reaction force control circuit 50 a includes a target steering reaction force calculation circuit 51 , a target steering angle calculation circuit 52 , a steering angle calculation circuit 53 , a steering angle feedback control circuit 54 , an adder 55 and an energization control circuit 56 .

[0050] The target steering reaction force calculation circuit 51 calculates the target steering reaction force T1* based on the steering torque Th and the vehicle speed V. The target steering reaction force calculation circuit 51 calculates the target steering reaction force T1* so that as the absolute value of the steering torque Th is larger and the vehicle speed V is lower, the value (absolute value) of the target steering reaction force T1* is larger.

[0051] The target steering angle calculation circuit 52 calculates the target steering angle θ* of the steering wheel 11 using the target steering reaction force T1*, the steering torque Th, and the vehicle speed V. When the sum of the target steering reaction force T1* and the steering torque Th is referred to as the input torque, the target steering angle calculation circuit 52 has an ideal model for determining an idealized steering angle based on the input torque. In the ideal model, a steering angle corresponding to an ideal turning angle according to the input torque is modeled in advance through experiments or the like, on the premise that the steering device in which the steering wheel 11 and the rotating wheel 16 are mechanically coupled. The target steering angle calculation circuit 52 estimates the input torque by adding the target steering reaction force T1* and the steering torque Th, and calculates the target steering angle θ* according to the input torque based on the ideal model.

[0052] The steering angle calculation circuit 53 calculates the actual steering angle θs of the steering wheel 11 based on the rotation angle θa of the reaction motor 31 detected by the rotation angle sensor 33. The steering angle feedback control circuit 54 calculates the steering angle correction amount T2* by feedback control of the steering angle θs so that the actual steering angle θs follows the target steering angle θ*. The adder 55 calculates the steering reaction force command value T* by adding the steering angle correction amount T2* to the target steering reaction force T1*.

[0053] The power-on control circuit 56 supplies power corresponding to the steering reaction force command value T* to the reaction motor 31. Specifically, the power-on control circuit 56 calculates the current command value for the reaction motor 31 based on the steering reaction force command value T*. In addition, the power-on control circuit 56 detects the actual current value Ia generated in the power supply path to the reaction motor 31 through a current sensor 57 provided on the power supply path. The current value Ia is the actual value of the current supplied to the reaction motor 31. Then, the power-on control circuit 56 evaluates the deviation between the current command value and the actual current value Ia, and controls the power supply for the reaction motor 31 so that the deviation is eliminated (feedback control of the current value Ia). As a result, the reaction motor 31 generates a torque corresponding to the steering reaction force command value T*. A moderate feeling corresponding to the road surface reaction force can be produced in the driver's hands.

[0054] Rotation control circuit

[0055] like Figure 2 As shown, the rotation control circuit 50 b includes a pinion angle calculation circuit 61 , a limit control circuit 62 , a pinion angle feedback control circuit 63 and an energization control circuit 64 .

[0056] The pinion angle calculation circuit 61 calculates the pinion angle θp, which is the actual rotation angle of the pinion shaft 44, based on the rotation angle θb of the rotating motor 41 detected by the rotation angle sensor 43. As described above, the rotating motor 41 and the pinion shaft 44 are interlocked with each other through the reducer 42. Therefore, there is a correlation between the rotation angle θb of the rotating motor 41 and the pinion angle θp. By using this correlation, the pinion angle θp can be evaluated based on the rotation angle θb of the rotating motor 41. In addition, as described above, the pinion shaft 44 is meshed with the rotating shaft 14. Therefore, there is a correlation between the pinion angle θp and the movement amount of the rotating shaft 14. That is, the pinion angle θp is a value that reflects the rotation angle θw of the rotating wheel 16.

[0057] The limit control circuit 62 calculates the limit value Ilim1 to which the amount of current to be supplied to the rotary motor 41 is limited, for example, based on the heating state of the rotary motor 41. The limit value Ilim1 is set as the upper limit of the amount of current to be supplied to the rotary motor 41 from the perspective of protecting the rotary motor 41 from overheating. The limit control circuit 62 calculates the limit value Ilim1 based on the comparison result between the temperature Tm (estimated temperature) of the rotary motor 41 detected by the temperature sensor 62a provided near the power supply path to the rotary motor 41 and the temperature threshold value. When the temperature Tm of the rotary motor 41 does not exceed the temperature threshold value, the limit control circuit 62 sets a large absolute value such that the current to be supplied to the rotary motor 41 by the energization control circuit 64 is not limited, based on the maximum current value that the rotary motor 41 can apply without overheating. On the other hand, when the temperature Tm of the rotary motor 41 exceeds the temperature threshold value, the limit control circuit 62 calculates the limit value Ilim1 having an absolute value smaller than the maximum current value that the rotary motor 41 can apply without overheating. The limit control circuit 62 calculates the limit value Ilim1 to have a smaller absolute value as the temperature Tm of the rotary electric motor 41 is higher.

[0058] The pinion angle feedback control circuit 63 acquires the target steering angle θ* calculated by the target steering angle calculation circuit 52 as the target pinion angle θp*. In addition, the pinion angle feedback control circuit 63 acquires the actual pinion angle θp calculated by the pinion angle calculation circuit 61. The pinion angle feedback control circuit 63 calculates the pinion angle command value Tp* by feedback control (PID control) of the pinion angle θp for causing the actual pinion angle θp to follow the target pinion angle θp* (which is equal to the target steering angle θ* in the embodiment).

[0059] The power-on control circuit 64 supplies power corresponding to the pinion angle command value Tp* to the rotating motor 41. Specifically, the power-on control circuit 64 calculates the current command value for the rotating motor 41 based on the pinion angle command value Tp*. In addition, the power-on control circuit 64 detects the actual current value Ib generated in the power supply path to the rotating motor 41 through a current sensor 64a provided on the power supply path. The current value Ib is the actual current value supplied to the rotating motor 41. Then, the power-on control circuit 64 evaluates the deviation between the current command value and the actual current value Ib, and controls the power supply to the rotating motor 41 so that the deviation is eliminated (feedback of the current value Ib). As a result, the rotating motor 41 rotates by an angle corresponding to the pinion angle command value Tp*.

[0060] Target steering angle calculation circuit

[0061] Next, the target steering angle calculation circuit 52 will be described in detail. As described above, the target steering angle calculation circuit 52 calculates the target steering angle θ* based on the input torque which is the sum of the target steering reaction force T1* and the steering torque Th based on the ideal model. The ideal model is a model using the following expression (1) expressing the input torque Tin* which is the torque to be applied to the steering shaft 12.

[0062] Tin*=Jθ*″+Cθ*′+Kθ* (1)

[0063] Among them, "J" is the moment of inertia of the steering wheel 11 and the steering shaft 12, "C" is the viscosity coefficient (friction coefficient) corresponding to the friction between the rotating shaft 14 and the housing, etc., and "K" is the spring coefficient when each of the steering wheel 11 and the steering shaft 12 is regarded as a spring.

[0064] As can be seen from expression (1), the input torque Tin* is obtained by adding a value obtained by multiplying a second-order time differential value θ*" of the target steering angle θ* by the moment of inertia J, a value obtained by multiplying a first-order time differential value θ*' of the target steering angle θ* by the viscosity coefficient C, and a value obtained by multiplying the target steering angle θ* by the spring coefficient K. The target steering angle calculation circuit 52 calculates the target steering angle θ* based on an ideal model based on expression (1).

[0065] like Figure 3 As shown, the ideal model based on expression (1) is divided into a steering model 71 and a vehicle model 72. The steering model 71 is coordinated based on the characteristics of the constituent elements of the steering device 10, such as the characteristics of the steering shaft 12 and the reaction motor 31. The steering model 71 includes an adder 73, a subtractor 74, an inertia model 75, a first integrator 76, a second integrator 77, and a viscosity model 78.

[0066] The adder 73 calculates the input torque Tin* by adding the target steering reaction force T1* and the steering torque Th. The subtractor 74 calculates the final input torque Tin* by subtracting each of a viscosity component Tvi* and a spring component Tsp* to be described later from the input torque Tin* calculated by the adder 73 .

[0067] The inertia model 75 serves as an inertia control calculation circuit corresponding to the inertia term of the expression (1). The inertia model 75 calculates the steering angular acceleration α* by multiplying the final input torque Tin* calculated by the subtractor 74 by the inverse of the inertia moment J.

[0068] The first integrator 76 calculates the steering angular velocity ω* by integrating the steering angular acceleration α* calculated by the inertial model 75. The second integrator 77 calculates the target steering angle θ* by further integrating the steering angular velocity ω* calculated by the first integrator 76. The target steering angle θ* is an idealized rotation angle of the steering wheel 11 (steering shaft 12) based on the steering model 71.

[0069] The viscosity model 78 serves as a viscosity control calculation circuit corresponding to the viscosity term of Expression (1). The viscosity model 78 calculates the viscosity component Tvi* of the input torque Tin* by multiplying the steering angular velocity ω* calculated by the first integrator 76 by the viscosity coefficient C.

[0070] The vehicle model 72 is coordinated based on the characteristics of the vehicle equipped with the steering device 10. For example, the characteristics of the vehicle that affect the steering characteristics are determined by the specifications of the suspension and wheel alignment, the grip (friction) of the turning wheel 16, etc. The vehicle model 72 is used as a spring characteristic control calculation circuit corresponding to the spring term of the expression (1). The vehicle model 72 calculates the spring component Tsp* (torque) of the input torque Tin* by multiplying the target steering angle θ* calculated by the second integrator 77 by the spring modulus K.

[0071] By using the target steering angle calculation circuit 52 configured in this way, the relationship between the input torque Tin* and the target steering angle θ* can be directly coordinated by adjusting the inertia moment J and viscosity coefficient C of the steering model 71 and the spring modulus K of the vehicle model 72, thereby achieving the desired steering characteristics.

[0072] In addition, the target steering angle θ* calculated according to the input torque Tin* based on the steering model 71 and the vehicle model 72 is used as the target pinion angle θp*. Then, feedback control is performed so that the actual pinion angle θp is consistent with the target pinion angle θp*. As described above, there is a correlation between the pinion angle θp and the rotation angle θw of the rotating wheel 16. Therefore, the rotation action of the rotating wheel 16 corresponding to the input torque Tin* is also determined by the steering model 71 and the vehicle model 72. That is, the steering feel of the vehicle is determined by the steering model 71 and the vehicle model 72. Therefore, the desired steering feel can be achieved by adjusting the steering model 71 and the vehicle model 72.

[0073] However, in the control device 50 configured in this way, the steering reaction force (the feeling in the hand obtained by steering) depends only on the target steering angle θ*. That is, the steering reaction force does not change due to the vehicle behavior or the road surface condition (slippery road surface, etc.). Therefore, it is difficult for the driver to grasp the vehicle behavior or road surface condition based on the steering reaction force. Therefore, in the present embodiment, from the perspective of solving this concern, the vehicle model 72 is configured as follows.

[0074] Vehicle Model

[0075] like Figure 4 As shown, the vehicle model 72 includes an ideal axial force calculation circuit 81, an estimated axial force calculation circuit 82, an axial force distribution calculation circuit 83, a virtual rack end axial force calculation circuit 84, a determination circuit 85, a limiting axial force calculation circuit 86, a maximum value selection circuit 87 and a conversion circuit 88.

[0076] The ideal axial force calculation circuit 81 calculates the ideal axial force F1 based on the target pinion angle θp*, which is an ideal value of the axial force acting on the rotating shaft 14 by the rotating wheel 16. The ideal axial force calculation circuit 81 calculates the ideal axial force F1 using an ideal axial force diagram stored in the storage device of the control device 50. The ideal axial force diagram is the following diagram, in which the horizontal axis represents the target pinion angle θp*, the vertical axis represents the ideal axial force F1, and the relationship between the target pinion angle θp* and the ideal axial force F1 is specified based on the vehicle speed V. The ideal axial force diagram has the following characteristics. That is, as the absolute value of the target pinion angle θp* is larger and the vehicle speed V is lower, the absolute value of the ideal axial force F1 is set to a larger value. The absolute value of the ideal axial force F1 increases linearly with the increase in the absolute value of the target pinion angle θp*. The ideal axial force F1 is set so as to have the same sign as the sign (positive or negative) of the target pinion angle θp*.

[0077] The estimated axial force calculation circuit 82 calculates the estimated axial force F2 (road surface reaction force) acting on the rotating shaft 14 based on the current value Ib of the rotating motor 41. Here, the disturbance corresponding to the road surface state (frictional resistance of the road surface) acts on the rotating wheel 16, thereby causing a difference between the target pinion angle θp* and the actual pinion angle θp, so that the current value Ib of the rotating motor 41 changes. That is, the current value Ib of the rotating motor 41 reflects the actual road surface reaction force acting on the rotating wheel 16. Therefore, the axial force reflecting the influence of the road surface state can be calculated based on the current value Ib of the rotating motor 41. The estimated axial force F2 is evaluated by multiplying the current value Ib of the rotating motor 41 by a gain that is a coefficient depending on the vehicle speed V.

[0078] The axial force distribution calculation circuit 83 calculates the mixed axial force F3 by adding the values ​​obtained by multiplying the ideal axial force F1 and the estimated axial force F2 by the individually set distribution ratio (gain). The distribution ratio is set according to various state quantities reflecting the vehicle behavior, road surface state or steering state. The distribution ratio can be set only based on the vehicle speed V, which is one of the state quantities of the vehicle. In this case, for example, as the vehicle speed V is higher, the distribution ratio of the ideal axial force F1 is set to a higher value, and the distribution ratio of the estimated axial force F2 is set to a lower value. In addition, as the vehicle speed V is lower, the distribution ratio of the ideal axial force F1 is set to a lower value, and the distribution ratio of the estimated axial force F2 is set to a higher value.

[0079] The virtual rack end axial force calculation circuit 84 calculates a virtual rack end axial force F4 for virtually limiting the operating range of the steering wheel 11 based on a target pinion angle θp* (target steering angle θ*) as a virtual rack end angle. The virtual rack end axial force F4 is calculated so that when the operating position of the steering wheel 11 approaches the limiting position of the operating range of the steering wheel 11 or when the rotating shaft 14 approaches the limiting position of the physically movable range of the rotating shaft 14, the torque (steering reaction torque) generated by the reaction motor 31 in the direction opposite to the steering direction increases rapidly. The limiting position of the operating range of the steering wheel 11 is determined by, for example, the length of a spiral cable provided in the steering wheel 11. The limiting position of the physically movable range of the rotating shaft 14 is a position where the moving range of the rotating shaft 14 is physically limited due to a so-called "end contact" by which the end (rack end) of the rotating shaft 14 abuts against a housing not shown.

[0080] The virtual rack end axial force calculation circuit 84 calculates the virtual rack end axial force F4 using a virtual rack end diagram stored in the storage device of the control device 50. The virtual rack end diagram is a diagram in which the horizontal axis represents the target pinion angle θp* and the vertical axis represents the virtual rack end axial force F4, and specifies the relationship between the target pinion angle θp* and the virtual rack end axial force F4. The virtual rack end diagram has the following characteristics. That is, before the absolute value of the target pinion angle θp* reaches the end determination threshold based on "0", the virtual rack end axial force F4 remains at "0", which is a neutral angle corresponding to the steering neutral position or the rotation neutral position. After the absolute value of the target pinion angle θp* reaches the end determination threshold, the virtual rack end axial force F4 is generated, and the virtual rack end axial force F4 increases rapidly, so that the absolute value of the virtual rack end axial force F4 increases.

[0081] Incidentally, the virtual rack end axial force F4 is set to have the same sign (positive or negative) as the sign of the target pinion angle θp*. In addition, the end determination threshold is set based on the value of the steering angle θs close to when the steering wheel 11 reaches the limit position of the operating range or the value of the pinion angle θp close to when the rotating shaft 14 reaches the limit position of the movable range.

[0082] The determination circuit 85 determines whether the rotating wheel 16 is in contact with an obstacle such as a curb. The determination circuit 85 determines that the rotating wheel 16 is in contact with an obstacle such as a curb when all of the following three determination conditions (A1), (A2), and (A3) are satisfied.

[0083] |Δθp(=|θp*-θp|)|>θth (A1)

[0084] |Ib|>Ith (A2)

[0085] |ωp|<ωth (A3)

[0086] In the determination condition (A1), "θp*" is the target pinion angle, and "θp" is the actual pinion angle. In addition, "Δθp" is an angle deviation, and is obtained by subtracting the actual pinion angle θp from the target pinion angle θp*. In addition, "θth" is an angle deviation threshold. The angle deviation threshold is set from the following angle. That is, in the case where the rotating wheel 16 is in contact with an obstacle, it is difficult to rotate the rotating wheel 16 to the side where the rotating wheel 16 is in contact with the obstacle. When the steering wheel 11 is turned to the side where the rotating wheel 16 is in contact with the obstacle in this state, the target steering angle θ* and further the target pinion angle θp* increase in response to the steering, but the turning angle θw and further the pinion angle θp remain at a constant value. Therefore, when the rotating wheel 16 attempts to rotate further in the case where the rotating wheel 16 is in contact with the obstacle, the deviation between the target steering angle θ* and the target pinion angle θp* increases. Therefore, it can be said that as the absolute value of the angle deviation Δθp is larger, there is a higher possibility that the rotating wheel 16 is in contact with the obstacle. Therefore, the angle deviation Δθp is a value indicating the degree of possibility that the turning wheel 16 contacts the obstacle. From this perspective, the angle deviation threshold θth is set by experiments or simulations in consideration of deviations caused by noise of the rotation angle sensor 43 .

[0087] In determining condition (A2), "Ib" is the current value Ib of the rotating motor 41, and "Ith" is the current threshold value. The current threshold value Ith is set from the following perspective. That is, when the rotating wheel 16 attempts to rotate further when the rotating wheel 16 is in contact with an obstacle, the absolute value of the current value Ib of the rotating motor 41 increases. Therefore, it can be said that as the absolute value of the current value Ib of the rotating motor 41 increases, there is a higher possibility that the rotating wheel 16 is in contact with the obstacle. Therefore, the current value Ib of the rotating motor 41 is also a value that represents the degree of possibility of the situation where the rotating wheel 16 is in contact with the obstacle. From this perspective, the current threshold value Ith is set through experiments or simulations.

[0088] In determining condition (A3), "ωp" is the pinion angular velocity, and is obtained by differentiating the target pinion angle θp* or the pinion angle θp. In addition, "ωth" is the angular velocity threshold. The angular velocity threshold ωth is set from the following perspective. That is, in the case where the rotating wheel 16 is in contact with an obstacle, it is difficult to rotate the rotating wheel 16. Therefore, it can be said that as the absolute value of the rotation speed of the rotating wheel 16 and further the absolute value of the pinion angular velocity ωp are smaller, there is a higher possibility that the rotating wheel 16 is in contact with the obstacle. Therefore, the pinion angular velocity ωp is also a value that represents the degree of possibility of the situation where the rotating wheel 16 is in contact with the obstacle. From this perspective, the angular velocity threshold ωth is set by experiment or simulation, taking into account the deviation caused by the noise of the rotation angle sensor 43, etc.

[0089] The determination circuit 85 sets the value of the flag Fo based on the determination result of whether the rotating wheel 16 is in contact with the obstacle. When it is determined that the rotating wheel 16 is not in contact with the obstacle, that is, when at least one of the three determination conditions (A1) to (A3) is not satisfied, the determination circuit 85 sets the value of the flag Fo to "0". When it is determined that the rotating wheel 16 is in contact with the obstacle, that is, when all of the three determination conditions (A1) to (A3) are satisfied, the determination circuit 85 sets the value of the flag Fo to "1".

[0090] In the case where the rotating wheel 16 contacts an obstacle, the limiting axial force calculation circuit 86 calculates the limiting axial force F5 to limit further turning to the side in contact with the obstacle. The limiting axial force calculation circuit 86 identifies whether it is necessary to calculate the limiting axial force F5 based on the determination result of the determination circuit 85, that is, the value of the flag Fo. When the value of the flag Fo is "0", the limiting axial force calculation circuit 86 does not calculate the limiting axial force F5. When the value of the flag Fo is "1", the limiting axial force calculation circuit 86 calculates the limiting axial force F5.

[0091] The limiting axial force calculation circuit 86 calculates the limiting axial force F5 based on the steering angle θs calculated by the steering angle calculation circuit 53 and the pinion angle θp calculated by the pinion angle calculation circuit 61. When calculating the limiting axial force F5, the limiting axial force calculation circuit 86 calculates the difference (angle deviation) between the steering angle θs and the pinion angle θp by subtracting the pinion angle θp from the steering angle θs. The limiting axial force calculation circuit 86 calculates the limiting axial force F5 using a limiting axial force diagram stored in a storage device of the control device 50. The limiting axial force diagram is a diagram in which the horizontal axis represents the absolute value of the difference between the steering angle θs and the pinion angle θp, the vertical axis represents the limiting axial force F5, and specifies the relationship between the difference between the steering angle θs and the pinion angle θp and the limiting axial force F5.

[0092] For example, the limiting axial force diagram has the following characteristics. That is, in the case where the absolute value of the difference between the steering angle θs and the pinion angle θp is within the range from "0" to the difference threshold, the limiting axial force F5 increases slowly as the absolute value of the difference between the steering angle θs and the pinion angle θp increases. After the absolute value of the difference between the steering angle θs and the pinion angle θp reaches the difference threshold, the limiting axial force F5 increases rapidly as the absolute value of the difference between the steering angle θs and the pinion angle θp increases.

[0093] Incidentally, the difference threshold is a value that enables determination that the turning wheel 16 is in contact with an obstacle, and is set by experiment or simulation. After the absolute value of the difference between the steering angle θs and the pinion angle θp reaches the difference threshold, the limiting axial force F5 is set from the perspective of generating a steering reaction force that makes it difficult for the driver to turn the steering wheel 11.

[0094] In addition to the difference between the steering angle θs and the pinion angle θp, the limiting axial force calculation circuit 86 can also calculate the limiting axial force F5 by considering the current value Ib and the pinion angular velocity ωp of the rotating motor 41. That is, the limiting axial force calculation circuit 86 comprehensively considers the degree of possibility of the situation where the rotating wheel 16 contacts the obstacle based on the difference between the steering angle θs and the pinion angle θp, the current value Ib and the pinion angular velocity ωp of the rotating motor 41, and calculates the limiting axial force F5 according to the degree of possibility.

[0095] In addition, the limiting axial force calculation circuit 86 can calculate the limiting axial force F5 based on the difference between the target steering angle θ* and the pinion angle θp or the target pinion angle θp* instead of based on the difference between the steering angle θs and the pinion angle θp. The difference between the target steering angle θ* and the pinion angle θp or the target pinion angle θp* is also a value indicating the degree of possibility of the situation where the rotating wheel 16 contacts the obstacle. In addition, the limiting axial force calculation circuit 86 can calculate the limiting axial force F5 based on the difference between the target steering angle θ* and the rotation angle obtained by multiplying the pinion angle θp and a predetermined conversion factor instead of based on the difference between the steering angle θs and the pinion angle θp.

[0096] The maximum value selection circuit 87 obtains the mixed axial force F3 calculated by the axial force distribution calculation circuit 83, the virtual rack end axial force F4 calculated by the virtual rack end axial force calculation circuit 84, and the limited axial force F5 calculated by the limited axial force calculation circuit 86. The maximum value selection circuit 87 selects the axial force with the maximum absolute value from the obtained mixed axial force F3, virtual rack end axial force F4, and limited axial force F5, and sets the selected mixed axial force F3, virtual rack end axial force F4, or limited axial force F5 as the final axial force Fsp of the spring component Tsp* used to calculate the input torque Tin*.

[0097] The conversion circuit 88 calculates (converts) the spring component Tsp* of the input torque Tin* based on the final axial force Fsp set by the maximum value selection circuit 87. In the case where the mixed axial force F3 is set to the final axial force Fsp by the maximum value selection circuit 87, the spring component Tsp* based on the final axial force Fsp is reflected in the input torque Tin*, so that the steering reaction force corresponding to the vehicle behavior or the road surface state can be provided to the steering wheel 11. The driver feels the steering reaction force as a feeling in the driver's hand through the steering wheel 11, so that the vehicle behavior or the road surface state can be grasped.

[0098] In the case where the virtual rack end axial force F4 is set to the final axial force Fsp by the maximum value selection circuit 87, the spring component Tsp* based on the final axial force Fsp is reflected in the input torque Tin*, so that the steering reaction force increases rapidly. Therefore, it is difficult for the driver to operate the steering wheel 11 in the direction of increasing the absolute value of the steering angle θs. Therefore, the driver has a contact feeling (feeling in the driver's hand) as the steering reaction force, so that it can be recognized that the steering wheel 11 has reached the limit position of the virtual operating range.

[0099] When the limiting axial force F5 is set to the final axial force Fsp by the maximum value selection circuit 87, the spring component Tsp* based on the final axial force Fsp is reflected in the input torque Tin*, so that the steering reaction force increases rapidly. Therefore, it is difficult for the driver to operate the steering wheel 11 to the side that contacts the obstacle. Therefore, the driver has a contact feeling as the steering reaction force, so that the driver can recognize that the turning wheel 16 contacts the obstacle such as the curb.

[0100] In this way, by controlling the reaction motor 31 and the turning motor 41 by the control device 50, the vehicle behavior, the road surface state, the steering state of the steering wheel 11, or the turning state of the turning wheel 16 can be notified to the driver by using the steering reaction force through the steering wheel 11. However, in the control of the control device 50, there are the following problems.

[0101] That is, the control device 50 adopts the current value Ib of the rotating motor 41 as one of the determination conditions of whether the rotating wheel 16 is in contact with an obstacle such as a curb. In addition, the control device 50 has a current limiting function that limits the amount of current to be supplied to the rotating motor 41 according to the heating state of the rotating motor 41. There is a concern that this current limiting function will interfere with the determination of whether the rotating motor 16 is in contact with an obstacle.

[0102] For example, in the case where the rotating wheel 16 comes into contact with an obstacle such as a curbstone at the time of stationary steering for starting of the vehicle, the amount of current to be supplied to the rotating motor 41 increases rapidly, and thus the temperature of the rotating motor 41 also rises rapidly. Therefore, before the current value Ib of the rotating motor 41 reaches the current threshold value Ith, the temperature of the rotating motor 41 can be close to the temperature in the overheated state, so that the amount of current to be supplied to the rotating motor 41 can be limited. Therefore, there is a concern that even if the rotating wheel 16 actually comes into contact with the obstacle, it cannot be determined that the rotating wheel 16 comes into contact with the obstacle. In this case, a steering reaction force for notifying the driver of the situation where the rotating wheel 16 comes into contact with the obstacle is not generated.

[0103] Therefore, the present embodiment adopts the following configuration as the vehicle model 72 to appropriately notify the driver of the situation that the turning wheel 16 is in contact with the obstacle by using the steering reaction force through the steering wheel 11 .

[0104] like Figure 4 As shown, the vehicle model includes a limit value calculation circuit 91, a minimum value selection circuit 92, and a threshold value calculation circuit 93. The limit value calculation circuit 91 calculates a limit value Ilim2 to which the amount of current to be supplied to the steering motor 41 is limited based on the determination result of the determination circuit 85 as to whether the rotating wheel 16 is in contact with an obstacle, that is, based on the value of the flag Fo. Details are shown below.

[0105] like Figure 5 As shown, the limit value calculation circuit 91 includes an adder 94, a holding circuit 95, and a calculation circuit 96. The adder 94 acquires the value (1 or 0) of the flag Fo set by the determination circuit 85, and calculates the count value Nf by adding the acquired value of the flag Fo to a value Nh held in the holding circuit 95 described later.

[0106] The holding circuit 95 acquires the count value Nf calculated by the adder 94, and holds the acquired count value Nf. Whenever the value of the flag Fo is acquired in the adder 94 at a prescribed sampling cycle, that is, whenever the count value Nf is calculated by the adder 94, the value Nh held in the holding circuit 95 is updated. That is, the value Nh held in the holding circuit 95 is the last time value before the count value Nf which is the current time value calculated by the adder 94, that is, the count value Nf in the previous calculation cycle. In addition, when the value of the flag Fo is switched from "1" to "0", the holding circuit 95 resets the value Nh held in the holding circuit 95 to "0". In the case where the count value Nf acquired from the adder 94 is the same as the last value, the holding circuit 95 recognizes that the value of the flag Fo is "0". In addition, the holding circuit 95 can recognize that the value of the flag Fo is "0" by acquiring the value of the flag Fo.

[0107] The calculation circuit 96 calculates the limit value Ilim2 to which the amount of current to be supplied to the rotary motor 41 is limited, based on the count value Nf calculated by the adder 94. Details are shown below.

[0108] like Figure 6 As shown in the graph of FIG. 1 , at time t1, it is determined that the rotating wheel 16 is in contact with the obstacle, so that the value of the flag Fo is set to "1". Thereafter, as the count value Nf increases, the calculation circuit 96 gradually reduces the limit value Ilim2 from the maximum limit value Imax to the minimum limit value Imin. When the value of the flag Fo is maintained at "1" after time t1, the calculation circuit 96 reduces the limit value Ilim2 by the set value ΔIc at the sampling period Δt.

[0109] Incidentally, the maximum limit value Imax is set based on the maximum current value that can be applied to the rotary motor 41 without overheating. The absolute value of the maximum limit value Imax is set to a large value so that the current to be supplied to the rotary motor 41 by the power-on control circuit 64 is not limited. The minimum limit value Imin is set based on the minimum current value that can be applied to the rotary motor 41 without overheating. The absolute value of the minimum limit value Imin is set to an absolute value as small as possible so that the current to be supplied to the rotary motor 41 by the power-on control circuit 64 is limited to a degree that minimizes the heat generation of the rotary motor 41 within an achievable range.

[0110] The calculation circuit 96 may switch the limit value Ilim2 from the maximum limit value Imax to the minimum limit value Imin immediately after the value of the flag Fo is switched from "0" to "1".

[0111] like Figure 4 As shown, the minimum value selection circuit 92 acquires the limit value Ilim1 calculated by the limit control circuit 62 and the limit value Ilim2 calculated by the limit value calculation circuit 91. The minimum value selection circuit 92 selects the limit value having the smaller absolute value from the acquired limit values ​​Ilim1 and Ilim2, and sets the selected limit value Ilim1 or limit value Ilim2 as the final limit value Ilim3 for calculating the current threshold value Ith, which is the criterion for determining whether the rotating wheel 16 is in contact with an obstacle.

[0112] Incidentally, the limit value Ilim2 is also supplied to the power-on control circuit 64 of the rotation control circuit 50b. The power-on control circuit 64 selects the limit value with the smaller absolute value from the limit values ​​Ilim1, Ilim2, and uses the selected limit value Ilim1 or limit value Ilim2 to limit the amount of current to be supplied to the rotation motor 41. That is, the power-on control circuit 64 compares the absolute value of the current to be supplied to the rotation motor 41 with the limit value Ilim1 or the limit value Ilim2 with the smaller absolute value among the absolute values ​​of the limit values ​​Ilim1, Ilim2. When the absolute value of the current to be supplied to the rotation motor 41 is greater than the limit value which is one of the limit values ​​Ilim1, Ilim2 and has the smaller absolute value, the power-on control circuit 64 limits the absolute value of the current to be supplied to the rotation motor 41 to the limit value which is one of the limit values ​​Ilim1, Ilim2 and has the smaller absolute value. When the absolute value of the current to be supplied to the rotary motor 41 is equal to or less than the limit value Ilim1, Ilim2 which is one of the limit values ​​having a smaller absolute value, the energization control circuit 64 supplies the rotary motor 14 with the original current calculated by feedback control of the current value Ib unchanged.

[0113] The threshold value calculation circuit 93 changes the current threshold value Ith, which is a criterion for determining whether the rotating wheel 16 is in contact with an obstacle, depending on the limit value Ilim3 set by the minimum value selection circuit 92. The details are shown below.

[0114] like Figure 7 As shown in the curve graph of , the threshold calculation circuit 93 calculates the current threshold Ith using the threshold map Mth. The threshold map Mth is a graph in which the horizontal axis represents the limit value Ilim3 and the vertical axis represents the current threshold Ith, and specifies the relationship between the limit value Ilim3 and the current threshold Ith. The threshold map Mth has the following characteristics. That is, Figure 7 As shown by the characteristic line L1 in the curve diagram, the current threshold Ith increases linearly with the increase of the limit value Ilim3. The current threshold Ith is set to the same value as the limit value Ilim3 through a one-to-one correspondence. The current threshold Ith changes along a straight line with a slope of "1" as the limit value Ilim3 changes.

[0115] Operation of the First Embodiment

[0116] Next, the operation of the control device when the rotating wheel comes into contact with an obstacle will be described. For example, in the case where the rotating wheel 16 comes into contact with an obstacle such as a curbstone at the time of stationary turning for starting of the vehicle, the rotating wheel 16 cannot be turned, and thus the pinion angle θp of the pinion shaft 44 cannot follow the target pinion angle θp*. Therefore, the current value Ib of the rotating motor 41 increases according to the difference between the pinion angle θp and the target pinion angle θp*, and the temperature of the rotating motor 41 increases as the current value Ib increases.

[0117] When the temperature of the rotating motor 41 detected by the temperature sensor 62a exceeds the temperature threshold, the control device 50 calculates the limit value Ilim1 to which the current to be supplied to the rotating motor 41 is limited. In addition, when all of the above three determination conditions (A1), (A2), (A3) are satisfied, the control device 50 determines that the rotating wheel 16 is in contact with an obstacle such as a curb. At this time, the control device 50 calculates the limit value Ilim2 to which the current to be supplied to the rotating motor 41 is limited. As time passes, the limit value Ilim2 gradually decreases from the maximum limit value Imax to the minimum limit value Imin.

[0118] Then, the control device 50 limits the amount of current to be supplied to the rotary motor 41 using the limit value which is one of the limit values ​​Ilim1, Ilim2 and has a smaller absolute value. Since the current value Ib of the rotary motor 41 is limited to at least the minimum limit value Imin, the rise in the temperature of the rotary motor 41 is suppressed. In addition, as the current value Ib of the rotary motor 41 decreases, the temperature of the rotary motor 41 gradually decreases and then reaches a temperature equal to or lower than the temperature threshold value. The rotary motor 41 is thereby protected from overheating.

[0119] In addition, the control device 50 sets the limiting value which is one of the limiting values ​​Ilim1 and Ilim2 and has a smaller absolute value as the final limiting value Ilim3 for calculating the current threshold value Ith, and calculates the current threshold value Ith, which is a criterion for determining whether the rotating wheel 16 is in contact with the obstacle, based on the set limiting value Ilim3. In this embodiment, the current threshold value Ith having the same value as the limiting value Ilim3 is calculated. That is, the current threshold value Ith is not set to a value greater than the current value Ib of the rotating motor 41, and the current value Ib is limited to the limiting value (Ilim1 or Ilim2) having the smallest absolute value.

[0120] Therefore, even when the limit value Ilim1 for protection from overheating is calculated, the current value Ib of the rotating motor 41 reaches the current threshold value Ith. Therefore, the control device 50 can appropriately determine that the rotating wheel 16 is in contact with the obstacle. In addition, the control device 50 can appropriately generate a steering reaction force for notifying the driver of the situation that the rotating wheel 16 is in contact with the obstacle.

[0121] When the contact between the rotating wheel 16 and the obstacle is cancelled thereafter and at least one of the above three determination conditions (A1), (A2), (A3) is not satisfied, the limit value Ilim2 for protecting against the obstacle is immediately restored from the minimum limit value Imin to the maximum limit value Imax.

[0122] That is, when at least one of the above three determination conditions (A1), (A2), (A3) is not satisfied, the value of the flag Fo is switched from "1" to "0", and the value Nh held in the holding circuit 95 is reset to "0". As a result, the count value Nf of the adder 94 becomes "0". Figure 6 As shown in the upper graph of the upper figure of , when the count value Nf is "0", the calculation circuit 96 sets the maximum limit value Imax to the limit value Ilim2. As described above, the maximum limit value Imax has a large absolute value so that the current to be supplied to the rotating motor 41 by the power-on control circuit 64 is not limited. Therefore, when the contact of the rotating wheel 16 with the obstacle is cancelled, the current corresponding to the current command value calculated by the power-on control circuit 64 is supplied to the rotating motor 41.

[0123] In this way, when the contact between the rotating wheel 16 and the obstacle is cancelled, the limit value Ilim2 for protecting from the obstacle is immediately restored from the minimum limit value Imin to the maximum limit value Imax. Thus, the period of time during which the rotation performance is reduced due to the limitation of the current of the rotating motor 41 for protecting the rotating motor 41 from overheating can be reduced to the minimum period.

[0124] Effects of the First Embodiment

[0125] Therefore, the following effects can be obtained with the first embodiment.

[0126] (1) The control device 50 limits the amount of current to be supplied to the rotating motor 41 using a limiting value that is one of the limiting values ​​Ilim1 and Ilim2 and has a smaller absolute value. Since the current value Ib of the rotating motor 41 is limited to at least the minimum limiting value Imin, the rise in the temperature of the rotating motor 41 is suppressed. In addition, the control device 50 sets the limiting value that is one of the limiting values ​​Ilim1 and Ilim2 and has a smaller absolute value as the final limiting value Ilim3 for calculating the current threshold value Ith, and calculates the current threshold value Ith having the same value as the set limiting value Ilim3. Therefore, even in the case where the current value Ib of the rotating motor 41 is limited, the current threshold value Ith is not set to a value greater than the current value Ib of the rotating motor 41. Therefore, the control device 50 can appropriately determine that the rotating wheel 16 is in contact with the obstacle.

[0127] (2) After determining that the rotating wheel 16 is in contact with the obstacle, the calculation circuit 96 gradually decreases the limit value Ilim2 from the maximum limit value Imax to the minimum limit value Imin as the count value Nf increases. Therefore, a rapid change in the limit value Ilim2 is suppressed.

[0128] (3) The control device 50 sets the current threshold value Ith to the same value as the limit value Ilim3 using the threshold value map Mth. Therefore, the threshold value map Mth only needs the following characteristics: the current threshold value Ith passes through the origin and changes linearly with the change of the limit value Ilim3, as in Figure 7 As shown in the characteristic line L1 in the graph above. Therefore, the threshold map Mth can be easily constructed. In the construction of the threshold map Mth, complicated adjustments and the like are not required.

[0129] However, if Figure 7 As shown in the graph of , it is preferred that the current threshold value Ith is set so as not to overlap with the current range RI actually used, which is the range of the current value Ib of the rotating motor 41 that can be generated in the normal use state of the vehicle. Examples of the normal use state of the vehicle include a state in which the vehicle is gripping and driving on a dry road and a stationary steering state in which the steering wheel 11 is turned when the vehicle is in a stopped state. With this configuration, in the normal driving state of the vehicle, the control device 50 is suppressed from erroneously determining that the rotating wheel 16 is in contact with an obstacle. In addition, in the case where the rotating wheel 16 is in contact with the obstacle, the current value Ib of the rotating motor 41 reaches the current threshold value Ith before the current value Ib is limited to the limit value Ilim3. Therefore, the control device 50 can more appropriately and quickly determine that the rotating wheel 16 is in contact with the obstacle.

[0130] (4) When the contact between the rotating wheel 16 and the obstacle is cancelled, the limit value Ilim2 for protection from the obstacle is immediately restored from the minimum limit value Imin to the maximum limit value Imax. Therefore, the period of time during which the rotation performance is reduced due to the limitation of the current of the rotating motor 41 for protecting the rotating motor 41 from overheating can be reduced to the minimum period.

[0131] Second embodiment

[0132] Next, a second embodiment of the steering device will be described. This embodiment has substantially the same Figures 1 to 3 This embodiment is different from the first embodiment in that a configuration not including the limit axial force calculation circuit 86 is adopted as the vehicle model 72 .

[0133] like Figure 8 As shown, the target steering angle calculation circuit 52 includes an ideal axial force calculation circuit 81, an estimated axial force calculation circuit 82, an axial force distribution calculation circuit 83, a virtual rack end axial force calculation circuit 84, a determination circuit 85, a maximum value selection circuit 87, and a conversion circuit 88. In addition, the target steering angle calculation circuit 52 includes a limit value calculation circuit 91, a minimum value selection circuit 92, and a threshold value calculation circuit 93. When the determination circuit 85 determines that the rotating wheel 16 is in contact with an obstacle, that is, when the value of the flag Fo is "1", the axial force distribution calculation circuit 83 supplies the estimated axial force F2 instead of the mixed axial force F3 to the maximum value selection circuit 87 regardless of the vehicle behavior, road surface state, or steering state.

[0134] In the case where the rotating wheel 16 contacts the obstacle, the rotating action of the rotating wheel 16 is suppressed, so that the actual pinion angle θp cannot follow the target pinion angle θp*, causing a rapid increase in the current value Ib of the rotating motor 41. That is, the current value Ib of the rotating motor 41 and the estimated axial force F2 calculated based on the current value Ib of the rotating motor 41 reflect the situation that the rotating wheel 16 contacts the obstacle.

[0135] Therefore, when the maximum value selection circuit 87 sets the estimated axial force F2 to the final axial force Fsp, the spring component Tsp* based on the final axial force Fsp is reflected in the input torque Tin*, so that the steering reaction force increases rapidly. Therefore, the driver has a contact feeling as the steering reaction force, so that the situation in which the rotating wheel 16 contacts an obstacle such as a curb can be recognized. In addition, the same effects as those of (1) to (4) described above in the first embodiment can be obtained using the second embodiment.

[0136] Other Implementations

[0137] The first embodiment and the second embodiment can be implemented with the following modifications. In the first embodiment and the second embodiment, as Figure 7 As shown by the characteristic line L1 in the upper graph of , the current threshold value Ith is set to the same value as the limit value Ilim3. However, the current threshold value Ith may be set to a value smaller than the limit value Ilim3.

[0138] In the first embodiment and the second embodiment, each of the virtual rack end axial force F4 and the limiting axial force F5 is supplied to the maximum value selection circuit 87, but the following configuration may be adopted. That is, the maximum value selection circuit 87 is set as a first maximum value selection circuit, and the second maximum value selection circuit is set on the calculation path from the virtual rack end axial force calculation circuit 84 and the limiting axial force calculation circuit 86 to the maximum value selection circuit 87. The second maximum value selection circuit selects the axial force with the largest absolute value from the virtual rack end axial force F4 and the limiting axial force F5, and sets the selected virtual rack end axial force F4 or limiting axial force F5 as the axial force supplied to the first maximum value selection circuit 87.

[0139] In the first and second embodiments, a configuration including an adder instead of the maximum value selection circuit 87 may be adopted as the vehicle model 72. The adder adds the mixed axial force F3, the virtual rack end axial force F4, and the limit axial force F5 to calculate the final axial force Fsp of the spring component Tsp* used to calculate the input torque Tin*. This configuration can also reflect the mixed axial force F3, the virtual rack end axial force F4, and the limit axial force F5 in the steering reaction force.

[0140] In the first and second embodiments, the target steering reaction force calculation circuit 51 estimates the target steering reaction force T1* based on the steering torque Th and the vehicle speed V. However, the target steering reaction force calculation circuit 51 may estimate the target steering reaction force T1* based only on the steering torque Th.

[0141] In the first and second embodiments, the target steering angle calculation circuit 52 uses the input torque Tin* which is the sum of the target steering reaction force T1* and the steering torque Th to calculate the target steering angle θ* of the steering wheel 11. However, the target steering angle calculation circuit 52 may calculate the target steering angle θ* of the steering wheel 11 using only the steering torque Th or using only the target steering reaction force T1* as the input torque Tin*.

[0142] In the first and second embodiments, the ideal axial force calculation circuit 81 calculates the ideal axial force F1 based on the target pinion angle θp* and the vehicle speed V. However, it is not always necessary to consider the vehicle speed V when calculating the ideal axial force F1. In addition, the ideal axial force F1 may be evaluated using a target rotation angle obtained by multiplying the target pinion angle θp* by a predetermined conversion factor instead of using the target pinion angle θp*.

[0143] In the first embodiment and the second embodiment, the estimated axial force calculation circuit 82 calculates the estimated axial force F2 based on the current value Ib of the rotating motor 41. However, the estimated axial force calculation circuit 82 can estimate and calculate the axial force acting on the rotating shaft 14, for example, based on the lateral acceleration or yaw rate detected by a sensor equipped in the vehicle. For example, the estimated axial force can be evaluated by multiplying the lateral acceleration by a gain that is a coefficient corresponding to the vehicle speed V. Because the road surface state such as the frictional resistance of the road surface or the vehicle behavior is reflected in the lateral acceleration, the actual road surface state is reflected in the estimated axial force calculated based on the lateral acceleration. In addition, the estimated axial force can be evaluated by multiplying the yaw rate differential value obtained by differentiating the yaw rate by the vehicle speed gain that is a coefficient corresponding to the vehicle speed V. Since the road surface state such as the frictional resistance of the road surface or the vehicle behavior is also reflected in the yaw rate, the actual road surface is also reflected in the estimated axial force calculated based on the yaw rate.

[0144] In the first and second embodiments, the virtual rack end axial force calculation circuit 84 may calculate the virtual rack end axial force F4 using the steering angle θs and the pinion angle θp instead of using the target steering angle θ* and the target pinion angle θp*. In this case, in the calculation of the virtual rack end axial force F4, the virtual rack end axial force calculation circuit 84 uses the angle that is one of the steering angle θs and the pinion angle θp and has a larger absolute value as the virtual rack end angle θend.

[0145] In the first embodiment, a configuration not including the ideal axial force calculation circuit 81 and the axial force distribution calculation circuit 83 may be adopted as the vehicle model 72. In this case, the estimated axial force F2 calculated by the estimated axial force calculation circuit 82 is supplied to the maximum value selection circuit 87 unchanged.

[0146] In the first and second embodiments, a configuration that does not include the virtual rack end axial force calculation circuit 84 may be adopted as the vehicle model 72. In the first and second embodiments, three determination conditions (A1) to (A3) are set as determination conditions for whether the rotating wheel 16 is in contact with an obstacle. However, it is only necessary to set at least the determination condition (A2).

[0147] In the first embodiment and the second embodiment, the control device 50 calculates the steering reaction force command value T* by adding the steering angle correction amount T2* to the target steering reaction force T1*. However, the steering angle correction amount T2* may be used as the steering reaction force command value T*. In this case, a configuration that does not include the adder 55 may be adopted as the control device 50. The target steering reaction force T1* calculated by the target steering reaction force calculation circuit 51 is supplied only to the target steering angle calculation circuit 52. The steering angle correction amount T2* calculated as the steering reaction force command value T* by the steering angle feedback control circuit 54 is supplied to the power-on control circuit 56.

[0148] In the first and second embodiments, a clutch may be provided in the steering device 10. In this case, Figure 1 As shown by the double-dotted line in FIG, the steering shaft 12 and the pinion shaft 13 are coupled by a clutch 21. An electromagnetic clutch that connects and disconnects dynamic power by electrically connecting and disconnecting an excitation coil is used as the clutch 21. The control device 50 performs a connection and disconnection control to switch the clutch 21 between connection and disconnection. When the clutch 21 is disconnected, the dynamic power transmission between the steering wheel 11 and the rotating wheel 16 is mechanically disconnected. When the clutch 21 is connected, the dynamic power transmission between the steering wheel 11 and the rotating wheel 16 is mechanically connected.

Claims

1. A steering device (10), characterized in that include: a mechanism configured to rotate a rotating wheel (16) of the vehicle; a first motor configured to generate a driving force provided to the mechanism; as well as A control device (50) is configured to control the first motor according to a steering state, wherein: The control device (50) comprises: a first calculation circuit (62) configured to calculate a first limit value to which the current to be supplied to the first motor is limited based on a heating state of the first motor; a determination circuit (85) configured to determine whether the rotating wheel (16) is in contact with an obstacle based on a comparison between a value of a current to be supplied to the first motor and a threshold value, a second calculation circuit (91) configured to calculate a second limit value to which the current to be supplied to the first motor is limited when the determination circuit (85) determines that the rotating wheel (16) is in contact with the obstacle; and A third calculation circuit (93) is configured to calculate the threshold value to be used by the determination circuit (85) based on the smaller limit value of the first limit value and the second limit value, wherein the initial value of the threshold value is set by experiment or simulation.

2. The steering device (10) according to claim 1, characterized in that The third calculation circuit is configured to calculate the threshold value having a value equal to a smaller limit value of the first limit value and the second limit value.

3. The steering device (10) according to claim 1, characterized in that The second calculation circuit (91) is configured to, when the determination circuit (85) determines that the rotating wheel (16) is in contact with the obstacle, reduce the second limit value from a maximum limit value to a minimum limit value, the maximum limit value being set based on a maximum current value that the first motor can apply without overheating, and the minimum limit value being set based on a minimum current value that the first motor can apply without overheating.

4. The steering device (10) according to claim 3, characterized in that The second calculation circuit (91) is configured to immediately restore the second limit value from the minimum limit value to the maximum limit value when the determination circuit (85) cancels the determination that the rotating wheel (16) is in contact with the obstacle.

5. The steering device (10) according to any one of claims 1 to 4, further comprising a second electric motor, wherein: The mechanism comprises a steering shaft (12) and a rotating shaft (14), wherein the steering shaft (12) is configured to rotate together with the operation of a steering wheel (11), and the rotating shaft (14) is arranged so that dynamic power transmission between the steering wheel (11) and the rotating shaft (14) is isolated; The second motor is a reaction motor (31) configured to generate a steering reaction force based on a first command value calculated according to the steering state, the steering reaction force being a torque provided to the steering shaft (12) and in a direction opposite to the steering direction; as well as The first motor is a rotary motor (41) configured to generate a rotational force based on a second command value calculated according to the steering state, the rotational force being a torque provided to the rotary shaft (14) and rotating the rotary wheel (16).

6. The steering device (10) according to claim 5, wherein: The control device (50) includes a limiting axial force calculation circuit, which is configured to, when the determination circuit (85) determines that the rotating wheel (16) is in contact with the obstacle, calculate the limiting axial force as the axial force of the rotating shaft (14) as a control for notifying the driver that the rotating wheel (16) is in contact with the obstacle, and the axial force of the rotating shaft (14) is reflected in the first instruction value for the reaction motor (31) to virtually limit the operation of the steering wheel (11).

7. The steering device (10) according to claim 5, wherein: The control device (50) comprises: an ideal axial force calculation circuit (81) configured to calculate an ideal axial force, the ideal axial force being an idealized axial force of the rotating shaft (14) based on a target rotation angle of a rotating body that rotates together with the rotating action of the rotating wheel (16); an estimated axial force calculation circuit (82) configured to calculate the axial force of the rotating shaft (14) as an estimated axial force based on a current value of the rotating motor (41) reflecting a vehicle behavior or a road surface state; and a distribution calculation circuit (83) configured to calculate a mixed axial force as an axial force of the rotating shaft (14) by mixing the estimated axial force with the ideal axial force based on the vehicle behavior or the road surface state, the axial force of the rotating shaft (14) being reflected in the first command value for the reaction motor (31), The allocation calculation circuit (83) is configured to, when the determination circuit (85) determines that the rotating wheel (16) is in contact with the obstacle, switch the axial force of the rotating shaft (14) from the mixed axial force to the estimated axial force as a control for notifying the driver that the rotating wheel (16) is in contact with the obstacle, and the axial force of the rotating shaft (14) is reflected in the first instruction value for the reaction motor (31).

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