Steering system

Abstract

The present invention relates to a steering system. The present invention provides a steer-by-wire type steering system with high practicality. A steering system includes a steering actuator (14), and the steering actuator (14) has a steering motor (50) configured as a dual system including a main system (50a) and a sub-system (50b). The wheels are steered by the force generated by the steering motor. During normal power supply in which power is supplied from a main power source (70) to the main system and the sub-system, the sub-system operates in coordination with the main system. During standby in which power is supplied from a backup power source (72) to the main system, while restricting the power supply to the main system, the main system operates, or the main system does not operate and the sub-system is independently controlled. During standby, the force for steering the wheels can be ensured, and the power supply from the backup power source can be maintained for a relatively long time.

Description

Technical Field

[0001] The present invention relates to a steer-by-wire type steering system mounted on a vehicle. Background Art

[0002] In a steer-by-wire type steering system, from the viewpoint of fail-safe, for example, as described in the following patent documents, a backup power source is provided, or the system is made redundant (doubled).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2020-138554

[0006] Patent Document 2: International Publication WO2017 / 115411 Pamphlet Summary of the Invention

[0007] In the case of adopting a backup power source, by taking into account the case where the capacity of the backup power source is relatively small, the practicality of the steering system can be improved. Further, in the case of making the steering system redundant, by taking into account the connection scheme of the backup power source in the redundant system and the like, the practicality of the steer-by-wire type steering system can also be improved. The present invention has been completed in view of such actual circumstances, and an object thereof is to provide a steer-by-wire type steering system with high practicality.

[0008] To solve the above problems, the first steering system of the present invention is a steer-by-wire type steering system, comprising: a main power supply and a backup power supply; a steering actuator having a steering motor configured as a dual system of a main system and a sub-system, and steering the wheels by the force generated by the steering motor; and a controller for controlling the operation of the main system and the sub-system of the steering motor in order to control the steering actuator based on a steering request, wherein the steering system is configured to selectively supply power from the main power supply and the backup power supply to the main system of the steering motor, and supply power to the sub-system of the steering motor only from the main power supply, and the controller is configured to: during normal power supply in which power is supplied from the main power supply to the main system and the sub-system of the steering motor, cause the sub-system of the steering motor to operate in matching with the main system of the steering motor; during backup in which power is supplied from the backup power supply to the main system of the steering motor, operate the main system of the steering motor while restricting the power supply to the main system of the steering motor, or independently control the sub-system of the steering motor without operating the main system of the steering motor. In addition, the second steering system of the present invention is a steer-by-wire type steering system, comprising: a main power supply and a backup power supply; a steering actuator having a steering motor, and steering the wheels by the force generated by the steering motor; and a controller for controlling the operation of the steering motor in order to control the steering actuator based on a steering request, wherein the controller is configured to: when the power supply to the steering motor is switched from the main power supply to the backup power supply, restrict the current supplied to the steering motor.

[0009] Advantages of the Invention

[0010] The backup power supply is, for example, for emergency use, and thus a power supply with a relatively small capacity (charge capacity) is adopted. Therefore, in the first steering system of the present invention in which the steering actuator is redundant, the backup power supply is configured to supply current only to the main system of the steering motor (hereinafter sometimes referred to as "steering main system") instead of the main power supply. On the other hand, in view of the small capacity of the backup power supply, in the first steering system of the present invention, it is configured to: during backup, impose a restriction on the power supply to the steering main system, or, for example, when current can be supplied from the main power supply to the sub-system of the steering motor (hereinafter sometimes referred to as "steering sub-system"), stop the operation of the steering main system without supplying power.

[0011] In addition, in the first steering system of the present invention, during normal power supply, that is, when current is supplied from the main power source to both the main steering system and the sub-steering system, considering the smooth operation of the steering device, the operation of the sub-steering system is matched with that of the main steering system. In other words, so-called "coordinated control" is performed. If coordinated control is performed during standby, the sub-steering system will also be restricted in current supply or its operation will stop, just like the main steering system. Therefore, in the first steering system of the present invention, during standby, the sub-steering system does not operate through coordinated control, but operates independently, that is, the sub-steering system operates in the same manner as during normal power supply, thereby ensuring the force for steering the wheels (hereinafter sometimes referred to as "steering force").

[0012] Moreover, in the second steering system of the present invention, it is set that when the power supply to the steering motor is switched from the main power source to the standby power source, the current supplied to the steering motor is restricted. Therefore, even with a standby power source with a relatively small capacity, this steering system can operate for a relatively long time.

[0013] Solution of the invention

[0014] In the first steering system of the present invention, during standby, the main steering system can be operated while restricting power supply (hereinafter sometimes referred to as "power supply restricted operation"), or the main steering system can be made not to operate (hereinafter sometimes referred to as "non-operation"), which can be arbitrarily set or selected according to the design of the vehicle, the situation of the vehicle, the power supply situation from the main power source to the sub-steering system, etc. In most situations, that is, generally speaking, when the main steering system performs power supply restricted operation, a larger steering force can be generated by the steering device compared with the non-operation situation. On the other hand, as will be described later, during high-speed operation of the steering motor during power supply restricted operation, etc., the main steering system operates in a so-called regeneration area and may become a resistance to the steering action of the wheels. Considering this situation, during standby, when the power supply from the main power source to the sub-steering system is appropriately carried out, the main steering system can be set to non-operation.

[0015] It should be noted that during standby, when proper power supply is not provided from the main power source to the steering subsystem, it is ideal not to operate the steering subsystem. At this time, regardless of whether the main steering system is set to power supply limit operation or non-operation when proper power supply is provided from the main power source to the steering subsystem, it is necessary to ensure the steering force. In view of this situation, it is ideal to make the main steering system perform power supply limit operation. Conversely, during standby, the main steering system is set to perform power supply limit operation when proper power supply is not provided from the main power source to the steering subsystem. On this premise, it can either perform power supply limit operation when proper power supply is provided from the main power source to the steering subsystem or be set to non-operation when proper power supply is provided from the main power source to the steering subsystem. In addition, as described above, it is also possible to switch between the power supply limit operation and non-operation of the main steering system according to whether it becomes a resistance to the steering action of the wheels.

[0016] Regarding the coordinated control of the main steering system and the steering subsystem, for example, it is ideal that when the configurations of the main steering system and the steering subsystem are the same, the operations of the two systems are controlled in such a way that the main steering system and the steering subsystem generate the same force during normal power supply.

[0017] In addition, the controller can be configured to have a dual system of the main system and the subsystem corresponding to the main system and the subsystem of the steering motor. The main system of the controller (hereinafter, sometimes referred to as the "control main system") and the subsystem of the controller (hereinafter, sometimes referred to as the "control subsystem") can be configured to have the same functions. Specifically, as long as they are respectively configured to be able to determine the current supplied to the corresponding main steering system and steering subsystem based on the steering request, and be able to supply power to the corresponding main steering system and steering subsystem based on the determined current. In the case of such a configuration, specifically, it can also be that during normal power supply, for coordinated control, based on the supply current to the main steering system determined by the control main system, the control subsystem supplies current to the steering subsystem. During standby, without relying on the supply current to the main steering system determined by the control main system, the control subsystem supplies current to the steering subsystem based on the supply current to the steering subsystem determined by itself.

[0018] Regarding the specific structure of the power supply, for example, it can also be configured that the main power supply includes a battery, while the standby power supply is a capacitor. In addition, the standby power supply can also be configured, for example, to receive power from the main power supply and charge during normal power supply, and supply power to the main steering system based on the charged electrical energy during standby. Description of the Drawings

[0019] Figure 1 It is a diagram schematically showing the overall configuration of the steering system of the embodiment.

[0020] Figure 2 It is a schematic diagram of the power supply in the steering system of the embodiment.

[0021] Figure 3 It is a flowchart of the basic steering program and the subordinate steering program executed in the steering system of the embodiment.

[0022] Figure 4 It is a graph showing the characteristics of the steering motor.

[0023] Figure 5 It is a graph for comparing the characteristics of the steering motor during normal power supply and standby.

[0024] Figure 6 It is a flowchart of the operation switching program executed in the steering system of the embodiment.

[0025] Figure 7 It is a flowchart of the reaction force applying program executed in the steering system of the embodiment.

[0026] Explanation of reference numerals:

[0027] 10: Wheel; 12, 12a, 12b: Operating device; 14: Steering device; 14a: Main steering system; 14b: Subordinate steering system; 20: Steering wheel [operating member]; 26: Reaction force motor; 28: Reaction force applying mechanism; 30: Motor rotation angle sensor; 42: Steering actuator; 50: Steering motor; 50a: Main steering system; 50b: Subordinate steering system; 54, 54a, 54b: Motor rotation angle sensor; 60: Operating electronic control unit (Operating ECU) [controller]; 62: Steering electronic control unit (Steering ECU) [controller]; 62a: Control main system; 62b: Control subordinate system; 68: Integrated electronic control unit (Integrated ECU) [controller]; 70: Main power supply unit [main power supply]; 72: Backup power supply unit [backup power supply]; 74: DC-DC converter; 76: Battery; 78: Capacitor. Detailed Description of the Invention

[0028] Hereinafter, as a specific embodiment, the steering system as an embodiment of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that, in addition to the following embodiments, the present invention can also be implemented in various forms represented by the solutions described in the items of [Solutions of the Invention], with various changes and improvements implemented based on the knowledge of those skilled in the art.

[0029] [Embodiment]

[0030] [A] Configuration of the Steering System

[0031] As Figure 1As schematically shown, the steering system of the embodiment mounted on the vehicle is a system for steering two wheels (front wheels) 10, each of which is a steerable wheel, and is a steer-by-wire type steering system having an operating device 12 and a steering device 14 that are mechanically independent of each other.

[0032] The operating device 12 is configured to include: a) a steering wheel 20 as an operating member for the driver to perform a steering operation (steering wheel operation); b) a steering shaft 22, at the top of which the steering wheel 20 is mounted; c) a steering column 24, which holds the steering shaft 22 rotatably and is supported by an instrument panel reinforcement (not shown); and d) a reaction force imparting mechanism 28, which uses an electric motor, i.e., a reaction force motor 26 supported by the steering column 24 as a power source, and imparts a reaction force (strictly speaking, a reaction force torque, but the term "operation reaction force" is used hereinafter) to the steering operation via the steering shaft 22. CT The reaction force applying mechanism 28 is applied to the steering wheel 20. The reaction force applying mechanism 28 is a general structure including a speed reducer and the like, and therefore the description of the specific structure of the reaction force applying mechanism 28 is omitted.

[0033] The reaction force motor 26 is a three-phase brushless DC motor, and magnets are attached to the outer periphery of the rotating shaft, and coils are arranged on the outer shell in a manner opposite to these magnets. The reaction force motor 26 is a dual-system motor in which two sets of coils are arranged for one magnet. Hereinafter, each of the dual systems is sometimes referred to as a reaction force motor 26a and a reaction force motor 26b. Each of the reaction force motors 26a and 26b independently has a motor rotation angle sensor 30a, 30b (hereinafter sometimes collectively referred to as a "motor rotation angle sensor 30") for detecting a rotation angle (which can be considered as a "relative angle" or "phase") ω within one rotation in order to switch the energized phase in the power supply to itself. Therefore, the present operating device 12 can be considered as a dual-system device as a redundant system (hereinafter sometimes referred to as an "operating device 12a" or "operating device 12b").

[0034] The operating device 12 has an operating angle sensor 32 that detects the operating angle δ of the steering wheel 20 as the steering wheel operation amount. By the way, when the posture of the steering wheel 20 in the straight-ahead state of the vehicle is regarded as the neutral posture, the rotation angles in the left and right directions from the neutral posture (which can be regarded as "absolute angles") are the operating angles δ of the steering wheel 20.

[0035] In addition, in the present steering system, similarly to a general so-called power steering system, a torsion bar 34 is assembled in the steering shaft 22, and operating torque sensors 36a, 36b (hereinafter sometimes collectively referred to as "operating torque sensors 36") are provided. The operating torque sensors 36a, 36b are used to detect the operating torque Tq as the operating force applied to the steering wheel 20 by the driver based on the twist amount of the torsion bar 34. O Two operating torque sensors 36 are provided to correspond to the dual systems of the operating device 12 .

[0036] Each of the wheels 10 is supported on the vehicle body in a steerable manner via a steering knuckle 40 which is a component of the suspension device. The steering device 14 steers each of the wheels 10 integrally by rotating the steering knuckle 40. The steering device 14 has a steering actuator 42 as a main component. The steering actuator 42 is configured to include: a) a steering rod (sometimes also called a "rack rod") 46, both ends of which are respectively connected to the left and right steering knuckles 40 via a connecting rod 44; b) a housing 48, which supports the steering rod 46 so that it can move to the left and right and is fixedly held on the vehicle body; and c) a rod moving mechanism 52, which uses a steering motor 50 which is an electric motor as a driving source, for moving the steering rod 46 to the left and right. The rod moving mechanism 52 is a mechanism with a ball screw mechanism composed of a ball groove and a nut as its main body, wherein the ball groove is screwed on the steering rod 46, and the nut is screwed with the ball groove via a bearing ball, and is rotated by the steering motor 50. The rod moving mechanism 52 is a general structure, and therefore, a detailed description of the rod moving mechanism 52 is omitted here.

[0037] It should be noted that the steering motor 50 is also a dual-system three-phase brushless DC motor like the reaction force motor 26, and each of the dual systems is sometimes referred to as a steering motor 50a and a steering motor 50b. Each of the steering motors 50a and 50b independently has a motor rotation angle sensor 54a, 54b (hereinafter sometimes collectively referred to as a "motor rotation angle sensor 54") for detecting a rotation angle (which can be considered as a "relative angle" or "phase") v within one rotation in order to switch the energized phase in the power supply to itself. Therefore, the present steering device 14 can be considered as a dual-system device as a redundant system (hereinafter sometimes referred to as a "steering device 14a" or a "steering device 14b"). Incidentally, the steering motors 50a and 50b also independently have a motor rotation angle sensor 54a, 54b for detecting the current I actually supplied to themselves. S Current sensors 56a and 56b (hereinafter sometimes collectively referred to as "current sensors 56") that perform detection.

[0038] Incidentally, the steering gear 14 is provided with a steering angle sensor 58 that detects the amount of movement to the left and right respectively from the neutral position of the steering lever 46 (the position in the straight-ahead state of the vehicle), thereby detecting the steering angle θ as the steering amount of the wheels 10.

[0039] Control of the operating device 12, specifically, control of the operating reaction force F CT is performed by operation electronic control units (hereinafter sometimes referred to as “operation ECUs”) 60a and 60b, which are respective controllers, namely operation controllers, corresponding to the dual systems of the operating device 12. Hereinafter, the operation ECUs 60a and 60b are sometimes collectively referred to as the operation ECU 60. Each operation ECU 60 is composed of a computer having a CPU (Central Processing Unit), a ROM (Read-Only Memory), a RAM (Random Access Memory), etc., and an inverter, which is a driver (drive circuit) for the reaction force motor 26.

[0040] Similarly, control of the steering gear 14, specifically, control of the steering angle θ, that is, control of the steering motor 50 of the steering gear 14, is performed by steering electronic control units (hereinafter sometimes referred to as “steering ECUs”) 62a and 62b, which are respective controllers, namely steering controllers, corresponding to the dual systems of the steering gear 14. Hereinafter, the steering ECUs 62a and 62b are sometimes collectively referred to as the steering ECU 62. Each steering ECU 62 is composed of a computer having a CPU, a ROM, a RAM, etc., and an inverter, which is a driver (drive circuit) for the steering motor 50.

[0041] The operation device 12a, the steering device 14a, the operation ECU 60a, and the steering ECU 62a form a system, and the operation device 12b, the steering device 14b, the operation ECU 60b, and the steering ECU 62b form another system. Thus, the steering system is configured as a dual-system steering system. Therefore, the operation device 12a and the steering device 14a are connected by a dedicated communication line 64a, and the operation device 12b and the steering device 14b are connected by a dedicated communication line 64b (hereinafter, the dedicated communication lines 64a and 64b are sometimes collectively referred to as the "dedicated communication line 64"). In addition, in order to enable communication between the operation devices 12 and the steering devices 14 of different systems, each operation device 12 and steering device 14 are connected to a CAN (Car Area Network or Controllable Area Network) 66, which is a general communication line.

[0042] In addition, as will be described in detail later, this steering system has a total electronic control unit (hereinafter, sometimes referred to as the "total ECU") 68 as a total controller for the two systems of this steering system. The total ECU 68 mainly consists of a computer, and the total ECU 68 is also connected to the CAN 66. It should be noted that it can also be considered that the two operation ECUs 60, the two steering ECUs 62, and the total ECU 68 constitute a controller of this steering system.

[0043] It should be noted that in this steering system, the operation device 12a, the steering device 14a, the operation ECU 60a, and the steering ECU 62a form the main system, and the operation device 12b, the steering device 14b, the operation ECU 60b, and the steering ECU 62b form the sub-system. The steering device 14a and the steering motor 50a can be respectively regarded as the main steering system 14a and the main steering system 50a, and the steering device 14b and the steering motor 50b can be respectively regarded as the sub-steering system 14b and the sub-steering system 50b. Similarly, the operation device 12a and the reaction force motor 26a can be respectively regarded as the main operation system 12a and the main reaction force system 26a, and the operation device 12b and the reaction force motor 26b can be respectively regarded as the sub-operation system 12b and the sub-reaction force system 26b. In addition, the operation ECU 60a and the steering ECU 62a can be respectively regarded as the main control system 60a and the main control system 62a, and the operation ECU 60b and the steering ECU 62b can be respectively regarded as the sub-control system 60b and the sub-control system 62b.

[0044] [B] Power Supply in the Steering System

[0045] As Figure 2As schematically shown, the steering system of the embodiment includes a main power supply unit (hereinafter sometimes simply referred to as the "main power supply") 70 as the main power source and a backup power supply unit (hereinafter sometimes simply referred to as the "backup power supply") 72 as the backup power source to supply power to the operating device 12 and the steering device 14. The main power supply 70 has a DC-DC converter 74 and a storage battery 76. The backup power supply 72 has a capacitor 78. It should be noted that the ground wires from the operating device 12 and the steering device 14 are omitted in the figure.

[0046] The vehicle equipped with this steering system is a hybrid vehicle, and power is supplied from the drive system power supply 80 to the DC-DC converter 74. The DC-DC converter 74 converts the voltage applied from the drive system power supply 80 into the drive voltage of this steering system. The storage battery 76 is connected in parallel with the DC-DC converter 74 to store the electric energy of the voltage transformed by the DC-DC converter 74. Incidentally, when the vehicle equipped with this steering system is not a hybrid vehicle or an electric vehicle, for example, when power is supplied from an alternator instead of from the drive system power supply 80, the main power supply 70 may be configured to include an alternator.

[0047] Power is supplied from the main power supply 70 to the reaction force motor 26b constituting the operation subsystem 12b and the steering motor 50b constituting the steering subsystem 14b via the operation ECU 60b and the steering ECU 62b, specifically, via the converters of the operation ECU 60b and the steering ECU 62b. On the other hand, power is supplied from the backup power supply 72 to the reaction force motor 26a constituting the operation main system 12a and the steering motor 50a constituting the steering main system 14a via the operation ECU 60a and the steering ECU 62a, specifically, via the converters of the operation ECU 60a and the steering ECU 62a.

[0048] The backup power supply 72 is powered from the main power supply 70, and the capacitor 78 is charged through this power supply. The backup power supply 72 performs this charging and allows the power supply from the main power supply 70 to pass through, thereby realizing the power supply from the main power supply 70 to the reaction force motor 26a and the steering motor 50a. Therefore, during normal power supply for normal operation, power is supplied from the main power supply 70 to the reaction force motor 26a and the steering motor 50a constituting the operation main system 12a and the steering main system 14a. In addition, power is also supplied from the main power supply 70 to the reaction force motor 26b and the steering motor 50b constituting the operation subsystem 12b and the steering subsystem 14b. Hereinafter, the power supply from the main power supply 70 through the backup power supply 72 will be simply referred to as the power supply from the main power supply 70.

[0049] On the other hand, for example, consider a case where the connection between the main power source 70 and the backup power source 72 is disconnected at the location shown by the hollow arrow in the figure. In this case, power supply to the reaction force motor 26a and the steering motor 50a achieved through the main power source 70 cannot be performed, and the backup power source 72 supplies power to the reaction force motor 26a and the steering motor 50a based on the electric energy stored in the capacitor 78. That is to say, the backup power source 72 has the function of switching the power supply source. Specifically, the backup power source 72 is configured to supply power from the capacitor 78 when it does not receive power from the main power source 70 at an appropriate voltage. It should be noted that the power supply from the capacitor 78 is referred to as the power supply from the backup power source 72.

[0050] That is to say, in this steering system, power is supplied only from the main power source 70 to the reaction force motor 26b constituting the operation subsystem 12b and the steering motor 50b constituting the steering subsystem 14b. In contrast, power can be selectively supplied from the main power source 70 and the backup power source 72 to the reaction force motor 26a and the steering motor 50a constituting the operation main system 12a and the steering main system 14a. Also, during standby, the power supply source for the reaction force motor 26a and the steering motor 50a is switched from the main power source 70 to the backup power source 72, and power is supplied to the reaction force motor 26a and the steering motor 50a from the backup power source 72.

[0051] The main power source 70 includes a storage battery 76, while the backup power source 72 only has a capacitor 78. Therefore, the capacity (charge capacity) of the backup power source 72 is quite small compared to the capacity of the storage battery 76. Considering this, in this steering system, the backup power source 72 is configured to supply power only to one of the dual systems of the operation device 12 and the steering device 14 respectively. Specifically, it supplies power only to the operation main system 12a and the steering main system 14a.

[0052] [C] Control of the Steering System

[0053] Hereinafter, regarding the control of this steering system, the steering control as the control of the steering device 14 and the reaction force control as the control of the reaction force imparting mechanism 28 of the operation device 12 will be described in sequence.

[0054] (a) Steering Control

[0055] The steering control is used to steer the wheels 10 according to a steering request, that is, the operating angle δ of the steering wheel 20 in the case of manual driving. The steering control is executed by the steering ECU 62. Specifically, the steering control is set to two types: independent steering control (sometimes only called "independent control") and coordinated steering control (sometimes only called "coordinated control"). Among them, the independent steering control is a control independently performed by the steering ECU 62a and the steering ECU 62b, which are controllers of a dual system, and the coordinated steering control is a control coordinately performed by the steering ECU 62a and the steering ECU 62b. Hereinafter, the independent steering control and the coordinated steering control will be described respectively, and then the steering control during standby and the process of control switching will be described.

[0056] i) Independent steering control

[0057] In the independent steering control, the steering ECU 62a that constitutes the control main system controls the steering main system 14a, and the steering ECU 62b that constitutes the control sub-system controls the steering sub-system 14b. That is to say, the steering ECU 62a and the steering ECU 62b perform the same control in parallel. Hereinafter, the steering controls of the steering ECU 62a and the steering ECU 62b will be summarized as the control of one system for description. It should be noted that in the following description of the independent steering control, when it is not necessary to distinguish between the main system and the sub-system, the suffixes a and b of the reference numerals of the components are not used.

[0058] The motor rotation angle ω of the reaction force motor 26 and the operating angle δ of the steering wheel 20 are in a relationship of a specified gear ratio. At the start of the vehicle, the motor rotation angle ω is calibrated based on the operating angle δ detected by the operating angle sensor 32. The operation ECU 60 obtains the operating angle δ of the steering wheel 20 based on the motor rotation angle ω detected by the motor rotation angle sensor 30 of the reaction force motor 26. In the independent steering control, the steering ECU 62 receives the information of the operating angle δ from the operation ECU 60 of this system. The steering ECU 62 multiplies the operating angle δ obtained by reception by the set steering gear ratio R according to the following formula G , thereby determining the target steering angle θ that is the target of the steering angle θ of the wheels 10 * .

[0059] θ * = R G ×δ

[0060] The steering angle θ of the wheels 10 and the motor rotation angle ν of the steering motor 50 are in a relationship of a specified gear ratio. The motor rotation angle ν is used instead of the steering angle θ to control the steering angle θ of the wheels 10. Therefore, the steering ECU 62 is based on the determined target steering angle θ *To determine the target motor rotation angle ν that is the target of the motor rotation angle ν of the steering motor 50 * . Incidentally, at the start of the vehicle, calibration of the motor rotation angle ν is performed based on the steering angle θ detected via the steering angle sensor 58.

[0061] The steering ECU 62 detects the actual motor rotation angle ν of the steering motor 50 via the motor rotation angle sensor 54, and determines the motor rotation angle deviation Δν that is the deviation of the motor rotation angle ν from the target motor rotation angle ν according to the following formula. *

[0062] Δν = ν * −ν

[0063] If the torque generated by the steering motor 50 is called the steering torque Tq S , then the steering ECU 62 determines the steering torque Tq that should be generated according to the feedback control rule based on the motor rotation angle deviation Δν, that is, according to the following formula. S . Incidentally, the first term, the second term, and the third term of the following formula are the proportional term, the integral term, and the differential term, respectively. G P , G I , G D are the proportional term gain, the integral term gain, and the differential term gain, respectively.

[0064] Tq S = G P ×Δν + G I ×∫Δνdt + G D ×dΔν / dt

[0065] If the current supplied to the steering motor 50 is called the steering current I S , then the steering torque Tq S and the steering current I S are roughly in a proportional relationship. According to this relationship, the steering ECU 62 determines the steering current I that should be supplied to the steering motor 50 based on the determined steering torque Tq S , and supplies the steering current I S to the steering motor 50. It should be noted that, as will be described in detail later, in order to utilize the value of the steering current I S in the control of the reaction force applying mechanism 28 of the operating device 12 and the coordinated steering control, the steering ECU 62 transmits information about the steering current I S . S

[0066] The steering ECU 62a and the steering ECU 62b repeatedly execute at short time intervals (for example, several msec to several tens of msec) in Figure 3The above-described independent steering control is performed by the basic steering program represented by the flowchart. Hereinafter, the processing according to this program will be briefly described. It should be noted that hereinafter, the processing of the steering ECU62a and the steering ECU62b according to the basic steering program is sometimes referred to as "basic steering processing".

[0067] In the basic steering processing, first, in S1, the operation angle δ of the steering wheel 20 is obtained from the operation ECU60, and in S2, the target steering angle θ is determined. * Then, in S3, the target motor rotation angle ν is determined. * And in S4, the actual motor rotation angle ν is detected. In the next S5, the motor rotation angle deviation Δν is determined, and in S6, the steering torque Tq is determined based on this motor rotation angle deviation Δν. S Then, in S7, based on the steering torque Tq S the steering current I as the supply current to the steering motor 50 is determined. S In S8, this steering current I S is supplied to the steering motor 50. The steering current I is transmitted in S9. S information.

[0068] ii) Coordinated steering control

[0069] The independent steering control is as described above, but in normal power supply where power can be supplied from the main power supply 70 to the steering main system 14a and the steering subsystem 14b, in this steering system, coordinated steering control is executed. The coordinated steering control is control that takes into account the smooth operation of the steering device 14, specifically the steering actuator 42, and generates the same force between the steering main system 14a and the steering subsystem 14b. In other words, the coordinated steering control is control that makes the steering motor 50b constituting the steering subsystem 14b work in matching with the steering motor 50a constituting the steering main system 14a.

[0070] In the independent steering control described above, the steering ECU62a constituting the control main system transmits information about the steering current I supplied to the steering motor 50a by itself S to the steering ECU62b constituting the control subsystem. The steering ECU62b does not determine the steering current I supplied to the steering motor 50b by itself S , but supplies the steering current I based on the received information S to the steering motor 50b.

[0071] On the other hand, the steering ECU62b repeatedly executes at short time intervals (for example, several msec to several tens of msec) in Figure 3The basic steering program is replaced by a subordinate steering program represented by a flowchart. In the processing according to this program, in S11, the steering ECU 62b obtains the steering current I that it should supply by receiving from the steering ECU 62a. S . Then, in S12, this steering current I S is supplied to the steering motor 50b. In S13, information on the steering current I S is sent. It should be noted that the processing of the steering ECU 62b according to this subordinate steering program is sometimes referred to as "subordinate steering processing".

[0072] iii) Steering control during standby

[0073] As described above, the standby power supply 72 is configured to include a capacitor 78 and has a considerably lower capacity compared to the main power supply 70. Therefore, when the steering main system 14a operates by receiving power supply from the standby power supply 72 instead of the main power supply 70, in this steering main system 14a, a limit is set for the steering current I S supplied to the steering motor 50a.

[0074] Without restricting the steering current I S , the steering motors 50a and 50b have a rotational speed - torque characteristic (N - T characteristic) as schematically shown by the solid line in the Figure 4 graph. In these steering motors 50a and 50b, there is an output peak. Therefore, the steering torque Tq S remains constant as Tq S1 until the motor rotational speed (strictly speaking, the number of revolutions per unit time, i.e., "rotational speed", hereinafter sometimes only referred to as "speed") N reaches N1. Then, as the speed N exceeds N1 and becomes higher, the steering torque Tq S linearly decreases and becomes 0 when the speed N reaches N2. S

[0075] Regarding the limitation of the steering current I S in this steering system, the detailed description is omitted, but the limitation of the steering current I S in this steering system is carried out by making the duty ratio in the PWM (pulse width modulation) operation of the converter of the steering ECU 62 lower than that during normal power supply and setting protection for the supplied maximum current. Therefore, the rotational speed - torque characteristic is as shown by the dash - dot line in the Figure 4 graph. Specifically, the steering torque Tq S remains as Tq S1 ’ (< Tq S1Becomes constant until the rotational speed N reaches N1’, and becomes higher as the rotational speed N exceeds N1’. The steering torque Tq S Decreases linearly, and the steering torque Tq S Becomes 0 when the rotational speed N reaches N2’ (< N2). Through such a limitation, even a small-capacity backup power supply 72 can supply power to the steering motor 50a for a relatively long time.

[0076] If the processing of the steering ECU 62a with the above-mentioned limitation on the steering current I S Is called “limiting steering processing” and is described with reference to the basic steering program represented by the flowchart in Figure 3 Then, in this limiting steering processing, as shown in parentheses, after the determination of the steering current I S At S7, before the current supply to the steering motor 50a at S8, at S7’, the above-mentioned current limitation is performed. At S8, based on the steering current I S After the limitation, current is supplied to the steering motor 50a.

[0077] It can be considered that the overall characteristics of the steering motor 50 are obtained by adding the characteristics of the steering motor 50a and the steering motor 50b respectively. If the rotational speed-torque characteristics of the steering motor 50a and the steering motor 50b without limiting the steering current I Figure 5 Are shown by the curve diagram of (a) in S , and the rotational speed-torque characteristics of the steering motor 50a with the steering current I Figure 5 Limited are shown by the curve diagram of (b) in S , then during normal power supply, the overall characteristics of the steering motor 50 become as shown in the curve diagram of (c) in Figure 5 . In contrast, if coordinated steering control is performed while limiting the steering current I S To the steering motor 50a, the rotational speed-torque characteristics of the steering motor 50b become the same as those of the steering motor 50a with the steering current I S Limited, as shown in the curve diagram of (d) in Figure 5 , the overall characteristics of the steering motor 50 will be quite low. In short, sufficient steering torque Tq S Cannot be obtained.

[0078] Therefore, in this steering system, during standby, independent steering control is adopted, and the main steering system 14a operates through limiting steering processing. That is to say, the main steering system 14a performs power supply limiting operation, and the sub-steering system 14b operates through basic steering processing. Through the operation of such a main steering system 14a and sub-steering system 14b, as shown in Figure 5As shown in the graph of (e), the overall characteristics of the steering motor 50 can maintain relatively high characteristics. It should be noted that the mode in which the main steering system 14a operates through the restricted steering process and the sub-steering system 14b operates through the basic steering process is called the "restricted operation mode".

[0079] Here, if we explain in more detail, the characteristics of the steering motor 50a achieved through the restricted steering process are as described above, becoming Figure 4 the characteristics of the single dotted line, but in the restricted operation mode, strictly speaking, as shown by the dotted line, when the rotational speed N of the steering motor 50 exceeds N2', it becomes the operation in the regeneration area. In the operation in this area, the torque generated by the steering motor 50a becomes the torque opposite to the steering torque Tq S generated by the steering motor 50b, becoming the torque that cancels the steering torque Tq S generated by the steering motor 50b. This may lead to a decline in the overall characteristics of the steering motor 50 in the restricted operation mode.

[0080] Worried about the decline in the overall characteristics of the steering motor 50 in the restricted operation mode, in addition to the restricted operation mode, this steering system also sets a "non-operation mode", that is, a mode in which the main steering system 14a does not operate and the sub-steering system 14b operates through the basic steering process. According to this non-operation mode, only the sub-steering system 14b generates the steering torque, so the overall characteristics of the steering motor 50 become Figure 5 as shown in the graph of (a). Even such overall characteristics can obtain characteristics higher than those in the case of performing coordinated steering control while performing power supply restriction work on the main steering system 14a during standby, that is, higher than the characteristics Figure 5 shown in the graph of (d).

[0081] Furthermore, the above-mentioned regeneration area is the area where the rotational speed N of the steering motor 50 exceeds N2'. Therefore, in this steering system, when the rotational speed N of the steering motor 50 becomes N2' or less, the steering device 14 operates in the restricted operation mode, and when the rotational speed N of the steering motor 50 exceeds N2', the steering device 14 operates in the non-operation mode, that is, a "switching mode" that also prepares to switch the operation mode according to the rotational speed N is provided.

[0082] Regarding which of the restricted operation mode, non-operation mode, and switching mode to adopt, it can be set at the vehicle manufacturing factory, sales dealership, etc. according to the type of the vehicle, etc. In addition, it can also be set to be arbitrarily set by the driver of the vehicle.

[0083] It should be noted that it is also envisaged that in the event of a failure of the main power supply 70 or the like, the steering sub-system 14b is not properly powered during standby. If such a situation is referred to as a "sub-system improper power supply situation", in this steering system, in the event of such a sub-system improper power supply situation, the steering sub-system 14b is not operated, and the steering main system 14a performs a power supply restriction operation. Specifically, regardless of which of the above-mentioned restriction operation mode, non-operation mode, and switching mode is adopted, in the event of a sub-system improper power supply situation, the steering main system 14a operates while restricting the power supply to the steering main system 14a. Therefore, for example, even in the event of a sub-system improper power supply situation, as the overall characteristics of the steering motor 50, although the characteristics are relatively low, the characteristics shown in the graph of (b) of Figure 5 are ensured.

[0084] iv) Flow of switching the operations of the steering main system and the steering sub-system

[0085] The switching of the operations of the steering main system 14a and the steering sub-system 14b is performed by the overall ECU 68. That is, the overall ECU 68 gives instructions on the operations that the steering main system 14a and the steering sub-system 14b should perform respectively during each of normal power supply and standby. In order to perform the above-mentioned operation switching, the overall ECU 68 repeatedly executes the operation switching program represented by the flow chart at short time intervals (for example, several msec to several tens of msec). Hereinafter, the processing according to this program will be described. Figure 6 In the processing according to the operation switching program, first, in S21, the power supply status of the standby power supply 72 is obtained from the standby power supply 72, that is, information on whether it is a state where power can be supplied from the main power supply 70 to the steering main system 14a is obtained. Although the detailed description is omitted, the standby power supply 72 is also connected to the CAN 66, and this information is obtained via the CAN 66. Then in S22, it is determined whether it is standby based on the obtained information.

[0086] In the case where it is determined that it is not standby, that is, in the case of normal power supply, in S23, in order to execute coordinated steering control, an instruction to execute the basic steering process is given to the steering ECU 62a as the control main system, and an instruction to execute the subordinate steering process is given to the steering ECU 62b as the control sub-system.

[0087]

[0088] ​When it is determined to be in the standby state, in S24, information on the voltage in the power supply from the main power supply 70 to the steering subsystem 14b is acquired. Incidentally, although detailed description is omitted, the steering ECU 62b has a voltage sensor for detecting the voltage of the power it receives, and the overall ECU 68 receives the above information from the steering ECU 62b via the CAN 66. Based on this information, in S25, it is determined whether the steering subsystem 14b can be supplied with power from the main power supply 70 at an appropriate voltage, that is, it is determined whether it is a state where the subsystem cannot be supplied with power appropriately. In the case of a state where the subsystem cannot be supplied with power appropriately, in S26, an instruction indicating the intention to perform a steering restriction process is sent to the steering ECU 62a that controls the main system, and an instruction indicating the intention not to operate the steering subsystem 14b is sent to the steering ECU 62b that controls the subsystem.

[0089] On the other hand, when it is determined in S25 that the steering main system 14b can be supplied with power from the main power supply 70 at an appropriate voltage, in S27, it is determined whether the operation mode flag FM is "1". The operation mode flag FM is a flag indicating which of the above-mentioned restricted operation mode, non-operation mode, and switching mode is adopted, and is as follows: it is set to "1" when the non-operation mode is adopted, set to "2" when the restricted operation mode is adopted, and set to "3" when the switching mode is adopted.

[0090] When the operation mode flag FM is "1", it is recognized as the non-operation mode. In S28, an instruction indicating the intention not to operate the steering main system 14a is sent to the steering ECU 62a that controls the main system, and an instruction indicating the intention to execute the basic steering process is sent to the steering ECU 62b that controls the subsystem. When it is determined in S27 that the operation mode flag FM is not "1", in S29, it is determined whether the operation mode flag FM is "2". When the operation mode flag FM is "2", it is recognized as the restricted operation mode. In S30, an instruction indicating the intention to execute the restricted steering process is sent to the steering ECU 62a that controls the main system, and an instruction indicating the intention to execute the basic steering process is sent to the steering ECU 62b that controls the subsystem.

[0091] When it is determined in S29 that the operation mode flag FM is not "2", that is, when the operation mode flag FM is "3", it is recognized as the switching mode. In S31, the motor speed N of the steering motor 50 is acquired. Incidentally, although detailed description is omitted, for the operating system in the steering main system 14a and the steering subsystem 14b, the speed N is determined based on the motor rotation angle ν detected by the motor rotation angle sensor 54, and information on the determined speed N is sent from the operating system in the steering main system 14a and the steering subsystem 14b.

[0092] Next, in S32, it is determined whether the rotational speed N exceeds the above-mentioned N2'. When the rotational speed N exceeds the above-mentioned N2', it is determined that the steering motor 50a becomes a working state in the regeneration area through the restricted steering process. In order to make the steering device 14 work in the non-operating mode, in S28, an instruction indicating not to make the main steering system 14a work is sent to the steering ECU 62a as the main control system, and an instruction indicating to execute the basic steering process is sent to the steering ECU 62b as the sub-control system. On the other hand, when it is determined that the rotational speed N is equal to or less than N2', in order to make the steering device 14 work in the restricted operating mode, in S30, an instruction indicating to execute the restricted steering process is sent to the steering ECU 62a as the main control system, and an instruction indicating to execute the basic steering process is sent to the steering ECU 62b as the sub-control system.

[0093] (b) Reaction force control

[0094] Reaction force control is a control for giving the driver a sense of operation for the steering wheel operation. In this steering system, when normally powered, the main operation system 12a and the sub-operation system 12b independently and in parallel apply the same operation reaction force F CT to the steering wheel 20. Hereinafter, the reaction force application processes performed by the operation ECU 60a constituting the main control system and the operation ECU 60b constituting the sub-control system in the reaction force control will be described together.

[0095] The operation ECU 60 determines the operation reaction force F S based on the steering load-dependent component F A as two components and the operation force-dependent reduction component F CT according to the following formula.

[0096] F CT = F S - F A

[0097] The steering load-dependent component F S is a component related to the steering force required to steer the wheels 10 (the steering torque Tq of the steering motor 50 S ), and is determined based on the steering current I S supplied to the steering motor 50. Although the detailed description is omitted, it is recognized that the larger the steering current I S , the greater the steering load of the wheels 10, and the steering load-dependent component F S is determined to be a larger value. Incidentally, the steering current I SThe relevant information is sent from the steering ECU 62 to the operation ECU 60 of the system via the dedicated communication line 64.

[0098] On the other hand, it can be considered that the operating force depends on the reduction component F A is the component for giving the driver the operating feeling in the so-called power steering system. In the power steering system, generally, an assist torque corresponding to the operating torque Tq O is applied to the steering shaft 22. Similar to imitating this assist torque, the operating force reduction component F is determined according to the following formula A .

[0099] F A = β × Tq O

[0100] Incidentally, β is the gain for determining the operating force reduction component F A , and the operation ECU 60 detects the operating torque Tq via the operating torque sensor 36 O .

[0101] Based on the operating reaction force F determined as above CT , the operation ECU 60 determines the reaction force current I as the current supplied to the reaction force motor 26 according to the following formula C , and supplies the determined reaction force current I C to the reaction force motor 26.

[0102] I C = α × F CT

[0103] Incidentally, α is the set current determination coefficient.

[0104] Each of the operation ECU 60a and the operation ECU 60b performs the above-described reaction force application process by repeatedly executing the reaction force application program represented by the flowchart in a short time interval (for example, several msec to several tens of msec) by the computers they each have. A brief description of the process according to this program is as follows. First, in S41, the steering current I is acquired Figure 7 , and in S42, the steering load-dependent component F is determined based on the steering current I S . In the next S43, the operating torque Tq is detected S , and in S44, the operating force reduction component F is determined based on the operating torque Tq S . Then in S45, based on the steering load-dependent component F O and the operating force reduction component F O and the operating force reduction component F A . Then in S45, based on the steering load-dependent component F S and the operating force reduction component F Ato determine the operating reaction force F CT , in S46, based on this operating reaction force F CT to determine the reaction force current I to be supplied to the reaction force motor 26 C . Then, in S47, based on this reaction force current I C supply current to the reaction force motor 26.

[0105] A brief description of the reaction force control during standby is as follows. Only power is supplied from the standby power supply 72 to the main operating system 12a. Therefore, as long as the voltage supplied to the operating subsystem 12b is appropriate, the above reaction force application process is only performed on the operating subsystem 12b. When the voltage supplied to the operating subsystem 12b is inappropriate, the above reaction force application process is only performed on the main operating system 12a.

Claims

1. A steering system, which is a steer-by-wire type steering system, includes: A main power supply and a backup power supply; A steering actuator having a steering motor with a dual system configured as a main system and a sub-system, and steering the wheels by the force generated by the steering motor; and A controller that controls the operations of the main system and the sub-system of the steering motor in order to control the steering actuator based on a steering request. Among them, The steering system is configured to selectively supply power from the main power supply and the backup power supply to the main system of the steering motor, and supply power to the sub-system of the steering motor only from the main power supply. The controller is configured to: during normal power supply when supplying power from the main power supply to the main system and the sub-system of the steering motor, cause the sub-system of the steering motor to operate in coordination with the main system of the steering motor; during backup when supplying power from the backup power supply to the main system of the steering motor, limit the power supply to the main system of the steering motor while causing the main system of the steering motor to operate, or independently control the sub-system of the steering motor without causing the main system of the steering motor to operate. The controller has a dual system of a main system and a sub-system corresponding to the main system and the sub-system of the steering motor. The controller is configured to: During normal power supply, supply power to the sub-system of the steering motor based on the supply current to the main system of the steering motor determined by the main system. During backup, supply power to the sub-system of the steering motor based on the supply current to the sub-system of the steering motor determined by itself, without relying on the supply current to the main system of the steering motor determined by the main system.

2. The steering system according to claim 1, wherein: The controller is configured to: During normal power supply, control the operations of the main system and the sub-system of the steering motor so that the main system and the sub-system of the steering motor generate the same force.

3. The steering system according to claim 1 or 2, wherein: The controller is configured to: During backup, when the main power supply does not supply power to the sub-system of the steering motor properly, limit the power supply to the main system of the steering motor while causing the main system of the steering motor to operate without causing the sub-system of the steering motor to operate.

4. The steering system according to claim 3, wherein: The controller is configured to: During backup, even when the main power supply supplies power to the sub-system of the steering motor properly, limit the power supply to the main system of the steering motor while causing the main system of the steering motor to operate.

5. The steering system according to claim 3, wherein: The controller is configured to: During backup, when the main power supply supplies power to the sub-system of the steering motor properly, not cause the main system of the steering motor to operate.

6. The steering system according to claim 1 or 2, wherein: The main power supply includes a battery, and on the other hand, the backup power supply is a capacitor.

7. The steering system according to claim 1 or 2, wherein: The backup power supply is configured to: When normally powered, it receives power from the main power supply and charges. When on standby, it supplies power to the main system of the steering motor according to the charged electrical energy.

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