Steering system

Abstract

To provide a steer-by-wire type steering system that is highly practical.SOLUTION: An operation reaction force applied to a steering wheel 20 is determined by adding a turning load dependence component, which is a component depending on a load IS for turning a wheel 10 and an operating force dependence reduction component for reduction in accordance with a detected operating force Tq. In addition, when the operating force cannot be detected, the operating force dependence reduction component is set to 0, and thus the turning load dependence component is limited. An operation feeling similar to a so-called power steering system can be provided to a driver. Even when an operating force by the driver cannot be detected, adverse effects due to a loss of the operating force dependence reduction component is mitigated and reduced, and thus a good operation feeling is maintained.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Recently, there has been active development of so-called steer-by-wire steering systems (hereinafter sometimes referred to as "steer-by-wire systems"), which are systems that steer the wheels in response to the operation of an operating member by a steering device equipped with a drive source, without relying on the operating force applied to the operating member by the driver. Since the operating member and the wheels are not mechanically connected in a steer-by-wire system, it is desirable to deal with the failure appropriately when a failure occurs in any part. For example, the steer-by-wire system described in the following patent document deals with the failure by adopting a redundant system. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-28312 A Summary of the Invention [Problem to be solved by the invention]

[0004] There is still room for improvement in dealing with failures in steer-by-wire systems, and improvements can improve the practicality of steer-by-wire systems. The present invention has been made in view of such circumstances, and an object of the present invention is to provide a steer-by-wire system that is highly practical. [Means for solving the problem]

[0005] In order to solve the above problems, the steering system of the present invention comprises: an operating member that is operated by an operating force of a driver; an operating device that holds the operating member in an operable manner and applies an operating reaction force that is a reaction force against the operation of the operating member; A steering device having a drive source for steering the wheels; a controller that controls the steering device to realize steering of the wheels in response to the operation of the operating member, and controls the operating device to control an operation reaction force; A steer-by-wire type steering system comprising: The operation device and the steering device are each provided in two systems, so that the steering system has two systems, the controller controls each of the two systems, and each of the two systems has a sensor that detects the operation force, The controller: For each of the two systems of the steering system, The operation reaction force is The corresponding system of the two systems of the steering device A steering load dependent component that is a component dependent on a load on the steering of the wheels; The sensors in the two corresponding systems and an operating force dependent reduction component for reducing the detected operating force; and When one of the two sensors fails, the operation of the one of the two systems of the steering system to which the failed sensor belongs is stopped, and only the operation of the other system is permitted; when both of the two sensors fail, The operation force dependent reduction component is set to 0, and the steering load dependent component is limited. While allowing both of the steering systems to operate, The present invention is configured to:

[0006] In the steer-by-wire system of the present invention, the operation reaction force applied by the operation device includes a steering load dependent component and an operation force dependent reduction component, as described above. In a steering system that is not a steer-by-wire system, the steered wheels and a steering operation member such as a steering wheel are mechanically connected, and the load of steering the wheels is transmitted to the driver. The steering load dependent component is a component that imitates that load. Also, in a so-called power steering system, the operation force of the driver is assisted by some kind of power to steer the wheels, so the operation reaction force is reduced by the amount of that assist. The operation force dependent reduction component is a component that imitates that assist. In other words, in this steering system, the operation feeling that the driver receives during steering operation is similar to the operation feeling of power steering. Note that the operation reaction force in this steering system may include other components in addition to the turning load dependent component and the operation force dependent reduction component.

[0007] The above-mentioned assist in the power steering system is generally performed, for example, by detecting the operation force of the driver based on the amount of twist of a torsion bar constituting a steering shaft, and based on the detected operation force, with a magnitude corresponding to the operation force. The operation force-dependent reduction component in this steering system may also be determined based on the operation force of the driver. However, when the operation force cannot be detected due to, for example, a failure of a sensor for detecting the operation force, the operation force-dependent reduction component cannot be generated, and the operation reaction force becomes too large. In other words, the driver feels that the steering operation has become heavy.

[0008] Therefore, in this steering system, when the steering force cannot be detected, the steering force-dependent decrease component is set to 0, while limiting the turning load-dependent component. That is, in order to alleviate and reduce the adverse effect caused by the absence of the steering force decrease component, in other words, to maintain a good steering feel, the turning load-dependent component is reduced. Specifically, for example, when the steering load is multiplied by a gain to determine the steering load-dependent component, the gain may be reduced, or, for example, a guard may be provided so that the turning load-dependent component does not become larger than a certain level. Note that the turning load-dependent component and the steering force-dependent decrease component have opposite positive and negative signs, so that "adding the turning load-dependent component and the steering force-dependent decrease component" can be considered as "subtracting the steering force-dependent decrease component from the turning load-dependent component" when the signs of the components do not matter.

[0009] The steering system of the present invention is preferably applied to a steer-by-wire system configured as a two-system system, for example, in which the steering device has two steering motors as drive sources and the operation device has two reaction motors as force sources for the operation reaction force. In such a two-system system, if a failure occurs in one of the two systems, the wheels can be steered by operating the other system. In such a system, the detected operation force is not used for steering the wheels as a rule. Therefore, even when the operation force cannot be detected, it is possible to maintain the operation of the two systems and make the operation reaction force appropriate by limiting the steering load-dependent component while setting the operation force-dependent reduction component to zero. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing a schematic diagram of an overall configuration of a steering system according to an embodiment of the present invention; [Diagram 2] This is a map used for determining a steering load dependent component which is a component of a reaction force against a steering operation. [Diagram 3] 4 is a flowchart of an operation program executed in the steering system of the embodiment. [Figure 4] 4 is a flowchart of a steering program executed in the steering system of the embodiment. [Diagram 5] 4 is a flowchart of a malfunction handling program executed in the steering system of the embodiment. [Figure 6] 13 is a flowchart of an operation reaction force determination process subroutine that constitutes the operation program. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, as a mode for carrying out the present invention, a steering system according to an embodiment of the present invention will be described in detail with reference to the drawings. In addition to the following embodiment, the present invention can be carried out in various forms with various modifications and improvements based on the knowledge of those skilled in the art. EXAMPLES

[0012] [A] Steering system configuration The steering system of the embodiment mounted on a vehicle is a system for steering two wheels (front wheels) 10, each of which is a steerable wheel, as shown diagrammatically in FIG. 1, and is a steer-by-wire type steering system equipped with an operating device 12 and a steering device 14 which are mechanically independent of each other.

[0013] The operation device 12 comprises: a) a steering wheel 20 as an operation member that is steered by the driver; b) a steering shaft 22 to the tip of which the steering wheel 20 is attached; c) a steering column 24 that rotatably holds the steering shaft 22 and is supported by an instrument panel reinforcement (not shown); and d) a reaction motor 26 that is an electric motor supported by the steering column 24, and generates a reaction force F (strictly speaking, a reaction torque, but hereinafter the commonly used term "operation reaction force") against the steering operation using a force source of the reaction motor 26. CT to the steering wheel 20 via the steering shaft 22. Since the reaction force imparting mechanism 28 has a general structure including a reducer and the like, a description of the specific structure of the reaction force imparting mechanism 28 will be omitted.

[0014] The reaction 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 in the housing to face the magnets. The reaction motor is a two-system motor in which two sets of coils are arranged for one magnet. Hereinafter, each of the two systems may be referred to as the reaction motor 26a and the reaction motor 26b. Each of the reaction motors 26a and 26b has its own motor rotation angle sensor 30a, 30b (hereinafter, sometimes collectively referred to as the "motor rotation angle sensor 30") for detecting the rotation angle (which can be considered as the "relative angle" or "phase") ω within one rotation in order to switch the energized phase in the power supply to the reaction motor 26a, 26b. Therefore, the present operating device 12 can be considered as a two-system device (hereinafter, sometimes referred to as the "operating device 12a" and the "operating device 12b") that is a redundant system.

[0015] The operation device 12 has an operation angle sensor 32 that detects the operation angle δ of the steering wheel 20 as the steering operation amount. When the steering wheel 20 is in a neutral position while the vehicle is traveling straight ahead, the rotation angles (which can be considered as "absolute angles") in both the left and right directions from the neutral position are the operation angle δ of the steering wheel 20.

[0016] In addition, in this steering system, as in a general so-called power steering system, a torsion bar 34 is incorporated in the steering shaft 22, and operation torque sensors 36a, 36b (hereinafter sometimes collectively referred to as "operation torque sensors 36") are provided for detecting operation torque Tq as an operation force applied to the steering wheel 20 by the driver based on the amount of twist of the torsion bar 34. Two operation torque sensors 36 are provided to correspond to the two systems of the operation device 12.

[0017] Each of the wheels 10 is supported on the vehicle body via a steering knuckle 40 so as to be steerable. The steering device 14 steers each of the wheels 10 as a unit 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 46 whose both ends are connected to the left and right steering knuckles 40 via link rods 44, b) a housing 48 that supports the steering rod 46 so as to be movable left and right and is fixedly held on the vehicle body, and c) a rod moving mechanism 52 that uses a steering motor 50, which is an electric motor, as a drive source to move the steering rod 46 left and right. The rod moving mechanism 52 is mainly composed of a ball screw mechanism that is composed of a ball groove screwed into the steering rod 46 and a nut that is screwed into the ball groove via a bearing ball and is rotated by the steering motor 50, and has a general structure, so a detailed description of the rod moving mechanism 52 will be omitted here.

[0018] Like reaction motor 26, steering motor 50 is a two-system three-phase brushless DC motor, and each of the two systems may be referred to as steering motor 50a and steering motor 50b. Each of steering motors 50a and 50b has its own motor rotation angle sensor 54a, 54b (hereinafter sometimes collectively referred to as "motor rotation angle sensor 52") for detecting the rotation angle (which may be considered as the "relative angle" or "phase") ν within one rotation in order to switch the energized phase in the power supply to itself. Therefore, steering device 14 can be considered as a two-system device (hereinafter sometimes referred to as "steering device 14a" and "steering device 14b") that are redundant systems. Incidentally, steering motors 50a and 50b each detect the current I actually supplied to itself. S The power supply 50 also has its own current sensors 56a and 56b (hereinafter, these may be collectively referred to as "current sensor 56") for detecting the current.

[0019] Incidentally, the steering device 14 has a steering angle sensor 58 for detecting the amount of movement of the steering rod 46 to the left and right from a neutral position (the position where the vehicle is located when traveling straight ahead) to detect the steering angle θ as the amount of steering of the wheels 10.

[0020] Control of the operation device 12, in detail, the operation reaction force F CT The control of the reaction force motor 26 of the operation device 12 is executed by operation electronic control units (hereinafter sometimes referred to as "operation ECUs") 60a, 60b as operation controllers that correspond to the two systems of the operation device 12. Hereinafter, the operation ECUs 60a, 60b may be collectively referred to as operation ECU 60. Each operation ECU 60 is composed of a computer having a CPU, ROM, RAM, etc., and an inverter that is a driver (drive circuit) of the reaction force motor 26.

[0021] Similarly, the control of steering device 14, more specifically, the control of steering angle θ, that is, the control of steering motor 50 of steering device 14, is executed by steering electronic control units (hereinafter sometimes referred to as “steering ECUs”) 62a, 62b as steering controllers that are respective controllers corresponding to the two systems of steering device 14. Hereinafter, steering ECUs 62a, 62b may be collectively referred to as steering ECU 62. Each steering ECU 62 is composed of a computer having a CPU, ROM, RAM, etc., and an inverter that is a driver (drive circuit) of steering motor 50.

[0022] The steering system is a two-system steering system, with the operation device 12a, the turning device 14a, the operation ECU 60a, and the turning ECU 62a constituting one system, and the operation device 12b, the turning device 14b, the operation ECU 60b, and the turning ECU 62b constituting another system. Therefore, the operation device 12a and the turning device 14a are connected by a dedicated communication line 64a, and the operation device 12b and the turning device 14b are connected by a dedicated communication line 64b (hereinafter, the dedicated communication lines 64a and 64b may be collectively referred to as "dedicated communication line 64"). In addition, in order to enable communication between the operation devices 12 and the turning devices 14 of the different systems, each operation device 12 and the turning device 14 is connected to a CAN (car area network or controllable area network) 66 as a common communication line.

[0023] As will be described in detail later, this steering system also has a master electronic control unit (hereinafter sometimes referred to as a "master ECU") 68 as a master controller for managing the two systems of the steering system. The master ECU 68 has a computer as its main component, and this master ECU 68 is also connected to the CAN 66. It can also be considered that the two operation ECUs 60, the two steering ECUs 62, and the master ECU 68 constitute one controller of this steering system.

[0024] [B] Steering system control (a) Normal control In the steering system of the embodiment, similar to a general steer-by-wire type steering system, the steering control of the wheels in response to the steering operation (hereinafter may be simply referred to as "steering control") and the control of the operation reaction force (hereinafter may be simply referred to as "reaction force control"). As explained above, this steering system is a two-system system, and under normal circumstances, that is, when no malfunction occurs in either system, each system executes the steering control and the reaction force control in parallel. Below, the basic reaction force control and the reaction force change process, which are the steering control and reaction force control executed in each system under normal circumstances, will be explained in order, and then the flow of these controls will be briefly explained.

[0025] i) Steering control The steering control is a control for realizing steering of the wheels 10 in response to a steering operation on the steering wheel 20. More specifically, it is a control for steering the wheels 10 to a steering angle θ in response to an operation angle δ of the steering wheel 20. The operation ECU 60 obtains the operation angle δ of the steering wheel 20 based on the motor rotation angle ω detected via the motor rotation angle sensor 30 of the reaction force motor 26. When the vehicle is started, the motor rotation angle ω is calibrated based on the operation angle δ detected by the operation angle sensor 30, and in the subsequent steering control, the operation angle δ of the steering wheel 20 is obtained by multiplying the motor rotation angle ω by a predetermined gear ratio.

[0026] The operation ECU 60 calculates the steering gear ratio R G By multiplying this by , the target steering angle θ of the wheel 10 is obtained. * Determine. θ * =R G ×δ The operation ECU 60 determines the target steering angle θ * The information regarding the above is transmitted to the steering ECU 62 of the same system via a dedicated communication line 64.

[0027] On the other hand, the steering ECU 62 transmits the target steering angle θ *The information on the target steering angle θ * Based on this, the target motor rotation angle ν * The steering angle θ of the wheels 10 and the motor rotation angle v of the steering motor 50 have a relationship that results in a specified gear ratio, and when the vehicle is started, the motor rotation angle v is calibrated based on the steering angle θ detected via the steering angle sensor 58. The subsequent steering control is performed using the motor rotation angle v instead of the steering angle θ.

[0028] The steering ECU 62 detects the actual motor rotation angle ν of the steering motor 50 via the motor rotation angle sensor 54, and calculates the target motor rotation angle ν * The motor rotation angle deviation Δν, which is the deviation of the motor rotation angle ν with respect to Δν=ν * -ν The steering ECU 62 then controls the current I supplied to the steering motor 50 in accordance with a feedback control rule based on the motor rotation angle deviation Δν, that is, in accordance with the following equation: S By the way, the first, second, and third terms in the following equation are proportional, integral, and differential terms, respectively, and G P ,G I ,G D are the proportional gain, integral gain, and differential gain, respectively. I S =G P ×Δν+G I ×∫Δνdt+G D ×dΔν / dt The steering ECU 62 outputs the determined current I S to the steering motor 50. Although detailed explanation is omitted, the steering ECU 62 detects the current I S is detected via a current sensor 56, and the supply current I S is controlled according to a feedback control technique.

[0029] ii) Reaction Force Control The reaction force control is a control for giving the driver a feeling of operation in response to the steering operation. In the reaction force control, the operation ECU 60 controls the operation reaction force F CT The steering load dependent component F S , the reduction component F A Based on this, it is determined according to the following formula: F CT =F S -F A

[0030] Steering load dependent component F S is a component related to the steering force required to steer the wheels 10, and the current I S Based on this, the current I S The larger the steering load on the wheel 10, the larger the steering load is recognized. S is determined to be a large value. Incidentally, the current I S The information relating to the above is sent from the steering ECU 62 via a dedicated communication line 64 to the operation ECU 60 of the same system.

[0031] On the other hand, the reduction component F A can be considered as a component for providing the driver with a so-called power steering system operation feeling. In a power steering system, an assist torque corresponding to the operation torque Tq is generally applied to the steering shaft 22. The operation force dependent reduction component F is calculated to simulate the assist torque. A is determined according to the following formula: F A =β×Tq By the way, β is the reduction component F A The operation ECU 60 detects the operation torque Tq via the operation torque sensor 36.

[0032] The reaction force F determined in the above manner CT Based on this, the operation ECU 60 controls the current IC is determined according to the following formula, and the determined current I C is supplied to the reaction motor 26. I C = α × F CT Incidentally, α is a current determination coefficient that is set.

[0033] iii) Modifications regarding steering control and reaction force control In this steering system, both systems perform the same steering control and the same reaction force control in parallel, but one of the two systems may be designated as the main system and the other as the auxiliary system, and the two systems may communicate via CAN 66 and work together to perform steering control and reaction force control.

[0034] Specifically, for example, the target steering angle θ * to the two steering ECUs 62, and each of the two steering ECUs 62 receives the target steering angle θ * Based on the above, the current I supplied to the steering motor 50 S Determine the current I S may be supplied to the corresponding steering motor 50. Also, for example, the supply current I S Based on the operation torque Tq detected by the operation ECU 60 included in the main system, the operation ECU 60 included in the main system determines the current I to be supplied to each of the reaction motors 26 of the two systems. C and determine the current I C may be supplied by the operation ECU 60 of each of the two systems to the reaction force motor 26 of each system.

[0035] (b) Dealing with Failures Since this steering system has two systems, basically, even if a failure occurs in one system, steering control and reaction force control can be executed by the other system. As explained above, this steering system has a supervisory ECU 68, and information on a failure is sent from each operation ECU 60 and each steering ECU 62 to the supervisory ECU 68, and the supervisory ECU 68 selects a method of dealing with the failure depending on the type of failure and issues instructions for dealing with the failure to each operation ECU 60 and each steering ECU 62.

[0036] i) Addressing basic deficiencies When a failure occurs in one of the two systems of the operating device 12 or one of the two systems of the steering device 14 that prevents it from operating, that is, when a failure occurs that prevents one of the two systems from operating, the steering control and reaction force control are executed by the one operating device 12 and one steering device 14 of the healthy system. The same applies when any of the sensors in one of the two systems fails.

[0037] To keep it simple, even if the steering control and reaction force control are performed using only one of the two systems, the adverse effects of the other not working can be covered to some extent. Specifically, even if the steering control is performed using only one of the two systems of steering devices 14, if the above-mentioned control method is followed, the motor rotation angle deviation Δν becomes large, and the current I supplied to the steering motor 50 becomes large. S By increasing the current I, a certain degree of steering force is guaranteed. Similarly, even if reaction force control is performed using only one of the two operating devices 12, the current I S As the operation reaction force F CT The steering load dependent component F S By increasing the force, a certain degree of reaction force is guaranteed.

[0038] In the steering system of this embodiment, basically, when a failure occurs in one of the two systems, the steering control and the reaction force control are performed by the other system. However, in the system in which the failure occurs, an operable part may be operated. Specifically, for example, when a failure occurs in one of the two operating devices 12, both of the two steering devices 14 may be operated by information from the other system. Conversely, for example, when a failure occurs in one of the two steering devices 14, both of the two operating devices 12 may be operated by information from the other system. Also, for example, when a sensor in one of the two systems fails, both of the two systems may be operated by information from a sensor of the same function in the other system.

[0039] ii) Addressing specific deficiencies For example, consider the case where a specific sensor fails, specifically, where a sensor not used for steering control fails in both of the two systems. Specifically, consider the case where both operation torque sensors 36a, 36b for detecting the operation torque Tq fail, making it impossible to detect the operation torque Tq at all. The torque sensors 36a, 36b are connected to the operation ECUs 60a, 60b, respectively, and the connectors for the connection are integrated, and the connection wires (lead wires) are often arranged in a bundled state. If the connector comes loose, the connection wires are broken, or the like, both of the two torque sensors 36a, 36b are deemed to have failed, resulting in a state where the operation torque Tq cannot be detected at all.

[0040] As described above, the operation torque Tq is not used for the steering control. Also, in the reaction force control, the above-mentioned operation force-dependent reduction component F A Therefore, in this steering system, when the operation torque Tq cannot be detected, the operation reaction force F is determined while both of the two systems are operated, that is, while both of the two systems of the operation device 12 and both of the two systems of the turning device 14 are operated. CT In determining the force-dependent reduction component F A is set to 0, and the reaction force F CIn order to reduce or prevent the steering load dependent component F S In other words, the supervisory ECU 68 is adapted to issue instructions to each of the two operation ECUs 60 and each of the two steering ECUs 62 to execute such operations and controls.

[0041] Steering load dependent component F S Specifically, each operation ECU 60 refers to one of the steering load dependent component limit maps shown in FIGS. 2(b), (c), and (d) instead of the normal steering load dependent component map shown in FIG. 2(a) to limit the steering load dependent component F S The map shown in FIG. 2(b) shows the steering load dependent component F S In other words, the current I supplied to the steering motor 50 increases. S The steering load dependent component F S By decreasing the gradient of the increase in (reducing the gain), the steering load dependent component F S The map shown in FIG. 2(c) is a map for limiting the steering load dependent component F S By setting an upper limit (guard) on the steering load dependent component F S The map shown in FIG. 2(d) is a map obtained by combining the maps shown in FIG. 2(b) and FIG. 2(c), that is, the steering load dependent component F S The gradient of the increase in the steering load dependent component F is reduced. S By setting an upper limit on the steering load dependent component F S It should be noted that although a detailed description will be omitted, which steering load dependent component limiting map is to be selected is determined in advance depending on the vehicle model, the running state of the vehicle, and the like.

[0042] Operational force dependent reduction component F A is set to 0, and the turning load dependent component F is calculated by referring to the turning load dependent component limit map instead of the normal turning load dependent component map as described above. SBy determining the reaction force F, even when the steering force cannot be detected, the operation of the two systems of the steering system is maintained and the reaction force F CT It is possible to make the above appropriate.

[0043] (c) Flow of Control The above steering control and reaction force control are performed by each operation ECU 60 repeatedly executing an operation program shown in the flowchart of Fig. 3, and each steering ECU 62 repeatedly executing a steering program shown in the flowchart of Fig. 4, at short time intervals (for example, several msec to several tens of msec). Furthermore, countermeasures against malfunctions are performed by the overall ECU 68 executing a malfunction countermeasure program shown in the flowchart of Fig. 5. Below, the flow of control will be briefly explained along these flowcharts.

[0044] In the process according to the operation program, first, in step 1 (hereinafter abbreviated as "S1"; the same applies to the other steps), the motor rotation angle ω of the reaction force motor 26 is detected via the motor rotation angle sensor 30, and in the following step S2, the operation angle δ of the steering wheel 20 is obtained based on the motor rotation angle ω. In the next step S3, the target steering angle θ, which is the steering angle θ at which the wheels 10 should be steered, is obtained based on the operation angle δ. * is determined, and in S4, the determined target steering angle θ * Information about the steering angle is transmitted to the steering ECU 62 of the same system.

[0045] In S5, the reaction force F CT This process is carried out by executing a subroutine for determining the operation reaction force, the flow chart of which is shown in FIG. 6. In the process according to the subroutine, first, in S51, the current I actually supplied to the steering motor 50 is determined. S Information regarding the above is received, and in S52, it is determined whether or not both of the operation torque sensors 36 are in a state in which it can be considered that they have failed, i.e., whether or not the operation torque Tq cannot be detected (hereinafter, sometimes referred to as an "operation torque non-detection state").

[0046] If it is determined in S52 that the steering torque is not non-detected, the above-mentioned normal steering load dependent component map of FIG. 2(a) is selected in S53, and the above-mentioned received current I is calculated with reference to the map in S54. S Based on the steering load dependent component F S Next, in S55, the operation torque Tq is detected via the operation torque sensor 36, and in S56, the operation force dependent reduction component F is calculated based on the operation torque Tq as described above. A is determined.

[0047] On the other hand, if it is determined in S52 that the operation torque is not detected, in S57, one of the steering load dependent component limiting maps of FIG. 2(b) to (c) is selected, and in S58, the received current I S Based on the steering load dependent component F S Then, in S59, the operating force-dependent reduction component F A is determined to be 0.

[0048] Steering load dependent component F S , the reduction component F A After the determination, in S60, the steering load dependent component F S and the reduction component F A and are added together to obtain the steering load dependent component F S From the operating force dependent reduction component F A is subtracted, and the reaction force F to be applied is CT is determined, and the process according to this subroutine ends.

[0049] Operation reaction force F CT After the determination process, in S6, the determined operation reaction force F CT Based on this, the current I supplied to the reaction motor 26 as described above is C is determined, and in S7, the reaction motor 26 is supplied with a current I C is supplied.

[0050] In the process according to the steering program, first, in S11, the target steering angle θ * In the next step S12, information on the target steering angle θ * Based on this, the target motor rotation angle ν * In the next step S13, the actual motor rotation angle ν is detected via the motor rotation angle sensor 54, and in step S14, the motor rotation angle deviation Δν is determined. Then, in step S15, as described above, the current I to be supplied to the steering motor 50 is determined according to the feedback control law based on the motor rotation angle deviation Δν. S is determined, and in S16, the current I S is supplied.

[0051] In S17, the current I actually supplied to the steering motor 50 is detected via the current sensor 56. S is detected, and in S18, the detected current I S The information about the above is transmitted to the operation ECU 60 of the same system.

[0052] In processing according to the failure handling program, first, in S21, it is determined whether the steering system is normal or not, and if it is normal, in S22, an instruction is given to each operation ECU 60 and each steering ECU 62 to execute normal control.

[0053] If the steering system is not normal, that is, if some kind of failure occurs, it is determined in S23 whether the failure is a failure of any of the sensors. If none of the sensors is failed, in S24, an instruction is given to the operation ECU 60 and steering ECU 62 of the system in which the failure occurs out of the two systems to stop the operation of that system, that is, an instruction is given not to execute the steering control and reaction force control in that system.

[0054] If it is determined in S23 that a malfunction has occurred in any of the sensors, then in S25 it is determined whether the sensor in which the malfunction has occurred is one used for steering control, specifically, whether the malfunction has occurred in the operation torque sensor 36. If the sensor in which the malfunction has occurred is not the operation torque sensor 36, then in S24 an instruction is given to the operation ECU 60 and steering ECU 62 of the system in which the malfunction has occurred out of the two systems to stop the operation of that system.

[0055] If the sensor in which the malfunction has occurred is the operation torque sensor 36, then in S26 it is determined whether it is possible to identify which of the two systems the malfunction has occurred in. If it is possible to identify that the malfunction is in one of the two systems, then in S24 an instruction is given to the operation ECU 60 and steering ECU 62 of the system in which the malfunction has occurred to stop the operation of that system.

[0056] On the other hand, in S26, if it cannot be determined which system of the operation torque sensor 36 is defective, it is determined that both of the operation torque sensors 36 of the two systems are defective, that is, the operation torque is not detected. In S27, the steering load dependent component F S In the determination of (a), it is determined that the steering load dependent component limit map is to be used. Then, in S28, an instruction to operate is given to both operation ECUs 60 and steering ECUs 62 of the two systems, and an instruction to the effect that the operation torque is in a non-detection state is given to both operation ECUs 60 of the two systems. [Explanation of symbols]

[0057] 10: Wheel 12a, 12b: Operation device 14a, 14b: Steering device 20: Steering wheel (operation member) 26a, 26b: Reaction motor 30a, 30b: Motor rotation angle sensor 34: Torsion bar 36a, 36b: Operation torque sensor 42: Steering actuator 46: Steering rod 50a, 50b: Steering motor 54a, 54b: Motor rotation angle sensor 56a, 56b: Current sensor 60a, 60b: Operation electronic control unit (operation ECU) (controller) 62a, 62b: Steering electronic control unit (steering ECU) (controller) 64a, 64b: Dedicated communication line 66: CAN 68: General electronic control unit (general ECU) (controller)

Claims

1. an operating member that is operated by an operating force of a driver; an operating device that holds the operating member in an operable manner and applies an operating reaction force that is a reaction force against the operation of the operating member; A steering device having a drive source for steering the wheels; a controller that controls the steering device to realize steering of the wheels in response to the operation of the operating member, and controls the operating device to control an operation reaction force; A steer-by-wire type steering system comprising: The operation device and the steering device are each provided in two systems, so that the steering system has two systems, the controller controls each of the two systems, and each of the two systems has a sensor that detects the operation force, The controller: For each of the two systems of the steering system, the operation reaction force is determined by adding a steering load dependent component, which is a component dependent on a load applied to the steering of the wheels of the corresponding system of the two systems of the steering device, and an operation force dependent reduction component for reducing the operation reaction force in accordance with the operation force detected by the sensor of the corresponding system of the two systems; and A steering system configured such that, when one of the two sensors fails, operation of the system to which the failed sensor belongs is stopped and operation of only the other system is permitted, and when both of the sensors in the two systems fail, the operating force dependent reduction component is set to zero and the steering load dependent component is limited while allowing operation of both of the two systems of the steering system.

2. A steering system as described in claim 1, wherein the operating force-dependent reduction component is a component that simulates the assist force in a so-called power steering system, and is determined to a larger value the greater the operating force.

3. The drive source of the steering device is an electric motor, 2. The steering system according to claim 1, wherein the steering load dependent component is determined based on a current supplied to the electric motor, and the greater the current, the greater the value of the steering load dependent component.

Images