CONTROL DEVICE AND CONTROL METHOD FOR A WIRE-BOUND STEERING SYSTEM

Abstract

Control device (20, 30, 40, 50) for a wire-operated steering system comprising a first motor (12) designed to control the steering via a feedback actuator, and a second motor (13) designed to control a steering angle of a wheel via a road wheel actuator, and capable of bidirectionally controlling the first motor (12) and the second motor (13), wherein the control device (20, 30, 40, 50) for a wire-operated steering system comprises: a basic SAT section (21) designed to obtain a simulated feedback actuator torque based on an angle of the first motor (12) and a vehicle speed; and a rack force estimation section (22) designed to estimate a rack force as a reaction force based on a steering angle of the wheel and a road wheel actuator.wherein a first control mode for controlling a simulated feedback actuator torque of the first motor (12) and a second control mode for controlling the first motor (12) based on a reaction force estimated by the rack force estimation section (22) are included, wherein a switch between the first control mode and the second control mode is provided based on an output of the basic SAT section (21) and an output of the rack force estimation section (22), characterized by a subtraction section designed to subtract an estimated rack force, estimated by the rack force estimation section (22), from a simulated feedback actuator torque obtained by the basic SAT section (21); and a switch section designed to output an estimated rack force from the subtraction section.which is estimated by the rack force estimation section (22), or to select a simulated feedback actuator torque obtained by the basic SAT section (21), wherein a feedback actuator torque can be determined based on an output of the switch section.

Description

Technical field The present invention relates to a control device for a steering system, and in particular to a control device and a control method for a wired steering system. Technical background In a conventional steering system, a steering column and a steering wheel are connected to a machine. In this system, a reaction force generated in a tire due to its interaction with the road surface is transmitted via a mechanical linkage to the steering wheel and then to the driver. This reaction force is essential for the driver to safely control the vehicle under all road conditions. Examples of reaction force include self-aligning torque (SAT) and steering disturbance caused by an obstacle. Steer-by-wire (SBW) is a system that lacks a mechanical connection between the steering wheel and a rack, replacing this connection with communication and an actuator. Since a reaction force generated in a tire cannot be mechanically transmitted to the driver, it is necessary to simulate the behavior of a steering system that corresponds to that of a conventional system during manual driving. A feedback actuator (FBA), installed in the steering wheel, serves to transmit this simulated reaction force to the driver.A road wheel actuator (hereinafter referred to as RWA), which is an actuator connected to a rack, provides a force to a steering road wheel to move the rack left and right. The FBA and the RWA are controlled by an electronic control unit (ECU), which is an embedded computer. One technique known in connection with such a self-balancing brake (SBW) system is described in US 2020 / 0 023 894 A1. US 2020 / 0 023 894 A1 discloses that a steering wheel's feedback torque is calculated based on a deviation between a steering torque applied to a rack and a steering torque that is less than a minimum torque. Technical problem However, the current SBW and the technique described in US 2020 / 0023894A1 focus primarily on replicating a conventional steering system. A reaction force, including noise from the road surface, is always returned to the driver, and there is a risk of causing an unpleasant steering feel. JP 2014-058225 A describes a device according to the preamble of claim 1. EP 3569475A1 describes a steering control system in which counterforces are calculated and taken into account depending on several conditions. EP 3575184A1 describes a steering control system in which an axial force of a steering actuation shaft is determined and influenced. Summary of the invention The object of the invention is to provide a control device and a control method for a wired steering system that are capable of realizing both comfort and safety. Solution to the task The above problem is solved by the features of claim 1. A control device for a wired steering system has the features of claim 1. It has a first motor that controls the steering via a feedback actuator, and a second motor that controls a steering angle of a wheel via a road wheel actuator, and is capable of controlling the first motor and the second motor bidirectionally. The control device for a wired steering system comprises a basic SAT torque section that receives a simulated feedback actuator torque based on an angle of the first motor and a vehicle speed, and a rack force estimation section that estimates a rack force as a reaction force based on a steering angle of the wheel and a road wheel actuator.A first control mode for controlling a simulated feedback actuator torque of the first motor and a second control mode for controlling the first motor based on a reaction force estimated by the rack force estimation section are included, and the first control mode and the second control mode are switched based on an output of the basic SAT section and an output of the rack force estimation section. Claim 1 specifies further features. A control method for a wired steering system has the features of claim 6. A control method is for a wired steering system comprising a first motor that controls the steering via a feedback actuator and a second motor that controls a steering angle of a wheel via a road wheel actuator and is capable of controlling the first motor and the second motor bidirectionally.The control method for a wired steering system comprises obtaining a simulated feedback actuator torque by a basic SAT section based on a first motor angle and a vehicle speed, estimating a rack force as a reaction force based on a wheel steering angle and a road wheel actuator by a rack force estimation section, and switching, based on an output of the basic SAT section and an output of the rack force estimation section, between a first control mode for controlling a simulated feedback actuator torque of the first motor and a second control mode for controlling the first motor based on a reaction force estimated by the rack force estimation section. Claim 6 specifies further features. Advantageous further training is the subject of the sub-claims. Advantageous effects of the invention According to the present invention, it is possible to provide a control device and a control method for a wired steering system that are capable of realizing both comfort and safety. Specifically, a basic SAT is calculated in a simulated feedback mode to provide comfortable steering and filter out any unnecessary noise from the road surface. A bilateral control mode (bilateral control component: BLC, hereinafter referred to as BLC) provides tactile feedback from the road to warn the driver when necessary (e.g., if a RWA cannot steer further due to the presence of an obstacle, a strong reaction force is generated at a FBA). An object, a configuration and an advantageous effect that differ from those described above are explained in more detail in the following description of an embodiment. Brief description of the drawings [Fig. 1] Fig. 1 is a schematic overall configuration diagram of an SBW system to which a control device according to the present invention is applied. [Fig. 2] Fig. 2 is a block diagram of a control device of a first embodiment according to an embodiment of the present invention. [Fig. 3] Fig. 3 is a flow diagram of an SBW system to which the control device according to the first embodiment is applied. [Fig. 4] Fig. 4 is a timing diagram showing an ON / OFF time of a BLC. [Fig. 5] Fig. 5 is a diagram illustrating a relationship between a reaction force observer and a friction model. [Fig. 6] Fig. 6 is a block diagram of the control device of a second embodiment according to another embodiment of the present invention. [Fig. 7] Fig. 7 is a block diagram of the control device of a third embodiment according to another embodiment of the present invention.[ Fig. 8 ] Fig. 8 is a block diagram of the control device of a fourth embodiment according to another embodiment of the present invention. Description of the embodiments First, an SBW system is described to which a control device for a wired steering system according to the present invention is applied. Fig. 1 is a schematic overall configuration diagram of an SBW system to which the control device according to the present invention is applied. As shown in Fig. 1, the SBW system comprises a steering wheel 11 (which may be referred to below as the steering system), an FBA motor (first motor) 12, an RWA motor (second motor) 13, a ball screw 14, and a rack 15. The steering wheel 11 is a handwheel that can be held by the driver, and the driver can input a steering command (steering torque) to control an angle of a rack. In an SBW system, a mechanical linkage is removed (there is no mechanical connection), whereas in a conventional steering system, a mechanical linkage exists between a steering wheel and a rack. A simulated reaction force is a force acting on the driver via the steering wheel 11 to reproduce a feeling of resistance when steering a conventional steering system. The rack 15 is a mechanical linkage section for steering a road wheel. An external axial force is a force introduced into the rack 15 from an external environment. The FBA (first motor) 12 is a motor attached to the steering wheel 11 whose function is to exert a simulated reaction force on the driver.The RWA motor (second motor) 13 is a motor used to steer the rack 15 according to a command received from an FBA. The ball screw 14 is a connecting section that converts a rotational movement of an RWA into a linear movement of the rack 15. The following describes, with reference to the drawings, an embodiment of a control device for a wired steering system according to the present invention, which is applied to the SBW system described above. First embodiment Fig. 2 is a block diagram of a control device of a first embodiment according to an embodiment of the present invention. As shown in Fig. 2, a control device 20 for a wired steering system comprises a block of a basic SAT 21, a block for rack force estimation 22, a block of amplification K 23, a block of dead zone 24 and a block for maximum element selection 25.Here, the control device 20 for a wired steering system is installed on an ECU, and a block of the basic SAT 21, a block for rack force estimation 22, a block of gain K 23, a block of dead zone 24, and a block for maximum element selection 25 are implemented, for example, by a processor, such as a CPU (not shown), a read-only memory (ROM) that stores various programs, a random access memory (RAM) that temporarily supports data of a computation process, and a storage device, such as an external storage device. A processor, such as a CPU, reads and executes various programs stored in a ROM and stores a computation result, which is an execution result, in a RAM or an external storage device.It should be noted that the control device 20 for a wired steering system is not limited to being installed on an ECU and can be configured to be installed on a different electronic control system. An FBA angle is an angle of the steering wheel 11 or of a motor attached to the steering wheel 11 (the FBA motor (first motor) 12). Vehicle speed is the speed at which a vehicle is moving relative to the ground. A base SAT block 21 receives an FBA angle and a vehicle speed and outputs an FBA torque to a maximum element selection block 25, simulating a torque transmitted to a steering wheel by a self-aligning torque (SAT) generated by a rotating road wheel (wheel). An RWA angle is an angle of the rack 15, a road wheel, or the RWA motor (secondary motor) 13 attached to a road wheel. An RWA torque is a torque generated by the RWA motor (secondary motor) 13, which is attached to a road wheel or to the rack 15. A rack force estimation block 22 is an algorithm for estimating the direction and magnitude of a force in the rack 15, receives an input of an RWA angle and an RWA torque, and outputs an estimated rack force to a reinforcement block K 23. A gain block K 23 is a gain for converting an estimated rack force, input from a rack force estimation block 22, into a torque converted to an FBA axis, and for comparing the torque with a base SAT block 21. A dead zone block 24 is a function whose task is to remove noise in an estimated rack force input from a rack force estimation block 22 and to produce a zero output in a certain range. A Maximum Element Selection Block 25 is a function that outputs a maximum element of the input, which is either a reference torque obtained by converting a simulated SAT input from a Base-SAT Block 21 into an FBA torque, or a converted estimated rack force. An FBA torque output by a Maximum Element Selection Block 25 is a torque applied to an FBA and the steering wheel 11. Fig. 3 is a flow diagram of an SBW system in which the control device 20 is used for a wired steering system according to the present embodiment. When a vehicle's ignition is switched on, a process shown in Fig. 3 begins. In step S101, an SBW system is activated. For example, the current FBA angle and RWA angle are checked and compared. In step S102, the SBW is activated, an angle (steering angle) of the steering wheel 11 (see Fig. 1) is detected and converted into a command to a RWA as a steering angle command. In other words: An FBA angle, which is an angle of the steering wheel 11 or of a motor attached to the steering wheel 11 (the FBA motor (first motor) 12), is detected (FBA steering angle data is received), and an angle command is issued from an FBA to an RWA. In step S103, a smoke and heat exhaust ventilation (SHEV) torque is calculated that is required to follow the angle command of the FBA. In step S104, the torque calculated in step S103 is generated in the RWA, and a driving state of the vehicle and the RWA is received. This means that the driving state of the vehicle and the RWA are monitored. In step S105, a rack force estimation block 22 (see Fig. 2), which forms the control device 20 for a wire-linked steering system, estimates an external axial force applied to the rack 15 (see Fig. 1) and converts the estimated rack force into an FBA torque. In step S106, a base SAT block 21 (see Fig. 2) also calculates an FBA torque (reference torque) that simulates a reaction torque by SAT using the FBA angle and a vehicle speed. In step S107, the converted estimated rack force is compared to a reference torque generated by a block of the base SAT 21, and it is determined whether a BLC should be switched on or off. Here, the BLC is assumed to be, for example, a case where a master is an FBA and a slave is a RWA. A steering angle (FBA angle), which is an angle of the steering wheel 11 received by an FBA on the master side, is transmitted as an angle command to an RWA on the slave side. If the RWA on the slave side operates according to the received angle command and a road wheel (wheel) comes into contact with an obstacle, the RWA on the slave side returns a detected force (tactile force) to the FBA on the master side. The FBA on the master side transmits a tactile force to a driver via the steering wheel 11.The bidirectional control carried out in this way between a master and a slave is a bilateral control component (BLC). Step S108 determines whether the BLC is switched on or off. In step S109, if the BLC is switched on, a converted estimated reaction force is output to the FBA, and tactile feedback from the road surface is transmitted to the driver via the steering wheel 11. Otherwise, in step S110, if the BLC is switched off, a reference torque generated by the FBA is calculated in a block of the base SAT 21. The calculated reference torque is then generated by the FBA, and a smooth and comfortable steering response force is provided to the driver. Step S111 checks whether the vehicle's ignition is still switched on. This means it checks whether the processing described above, from step S102 to step S110, will continue. If the vehicle's ignition is still switched on, the processing returns to step S102 and the processing described above, from step S102 to step S110, is executed. If, however, the vehicle's ignition is switched off, the processing is terminated. Fig. 4 is a time graph illustrating an ON / OFF time history of a BLC. In Fig. 4, G101 is an example of a time series comparing the output (reference torque) from a block of the Base-SAT 21 (see Fig. 2) with an estimated rack force output from a Rack Force Estimator block 22 (see Fig. 2). The horizontal axis represents time, the vertical axis represents force, a solid line represents the output (reference torque) from a block of the Base-SAT 21, and a dashed line represents an estimated rack force output from a Rack Force Estimator block 22. G102 is a time series indicating a switching time of a BLC when a time series for comparing the output (reference torque) from a block of the base SAT 21 with an estimated rack force output from a rack force estimation block 22 is G101.A maximum element selection block 25 (see Fig. 2), shown in Fig. 2, compares the output (reference torque) from a base SAT block 21 with an estimated rack force output by a rack force estimation block 22, and outputs one of them, which is a maximum value, as the FBA torque, and if the estimated rack force exceeds the output (reference torque) from a base SAT block 21, a BLC is turned on. Figure 5 is a diagram illustrating the relationship between a reaction force observer and a friction model. In Figure 5, a reaction force observer (RFOB) uses an algorithm to estimate a rack force without using a force sensor. A pinion angle is an angle of the steering wheel 11 or a converted RWA angle of the steering wheel 11. A pinion velocity is a ratio of the steering wheel angle to the rotation. A friction force is a resistive force generated by an object in contact with the rack during movement within an RWA. An RWA setpoint model is a model that counts backwards a force acting on the rack 15 (see Figure 1) using a pinion angle. An RWA friction model is a model within a setpoint model for calculating a friction force, improving the estimation accuracy of a rack force. As described above, according to the present embodiment it is possible to provide a control device for a wired steering system that achieves both comfort and safety. Second embodiment Fig. 6 is a block diagram of a control device of a second embodiment according to another embodiment of the present invention. The present embodiment differs from the first embodiment in that the control device 30 for a wired steering system comprises, instead of a dead zone block 24 and a maximum element selection block 25, a deviation calculation block 31, a relay block 22, a delay block 23, a switch block 34, and a transition smoothing block 35. The same components as in the first embodiment are designated by the same reference numerals, and any description that overlaps with the first embodiment is omitted. As shown in Fig. 6, the control device 30 for a wired steering system according to the present embodiment comprises a block of the basic SAT 21, a block for rack force estimation 22, a block of amplification K 23, a block for deviation calculation 31, a block of relay 22, a block of delay 23, a block of switch 34 and a block for transition smoothing 35.Here, the control device 30 for a wired steering system is installed on an ECU, and a block of the base SAT 21, a block for rack force estimation 22, a block of gain K 23, a block for deviation calculation 31, a block of relay 22, a block of delay 23, a block of switch 34, and a block for transition smoothing 35 are implemented, for example, by a processor such as a CPU (not shown), a ROM that stores various programs, a RAM that temporarily supports data in a computation process, and a storage device such as an external storage device. A processor, such as a CPU, reads and executes various programs stored in a ROM and stores a computation result, which is an execution result, in a RAM or an external storage device.It should be noted that the control device 30 for a wired steering system is not limited to being installed on an ECU and can be configured for installation on another electronic control system. Furthermore, a deviation calculation block 31, a relay block 22, a delay block 23, and a switch block 34 can be implemented in hardware. A deviation calculation block 31 is a subtraction block for comparing or extracting a difference between the output of a block of the basic SAT 21 and the output of a rack force estimation block 22. A block of relay 22 is a mechanism for preventing "hunting" to avoid unnecessary switching between a block of the base SAT 21 and a block for rack force estimation 22. A block of delay 23 has the function of continuing to select a BLC mode even when no external force is applied to the rack 15 (see Fig. 1). A block of switch 34 has the function of selecting an output from a block of base SAT 21 (a reference torque generated by an FBA), an output from a block for rack force estimation 22 (a value obtained by converting an estimated rack force into a torque for an FBA), and an output (a signal) from a block of delay 23, and outputting the selected output to a block for transition smoothing 35.A transition smoothing block 35 has the function of reducing a sharp change in value (a steep change in value) when an FBA torque is switched from a rack force estimation block 22 to a base SAT block 21, and avoiding confusion of a driver. According to the present embodiment, in addition to the effect of the first embodiment, it is possible to make the transition from a BLC mode to a basic SAT mode smoother. Third embodiment Fig. 7 is a block diagram of a control device of a third embodiment according to another embodiment of the present invention. The present embodiment differs from the first embodiment in that a control device 40 for a wired steering system does not include a dead zone 24 block. The same components as in the first embodiment are designated with the same reference numerals, and any description that overlaps with the first embodiment is omitted. As shown in Fig. 7, the control device 30 for a wired steering system according to the present embodiment comprises a base SAT block 21, a rack force estimation block 22, a gain K block 23, and a maximum element selection block 25. Here, the control device 40 for a wired steering system is installed on an ECU, and a base SAT block 21, a rack force estimation block 22, a gain K block 23, and a maximum element selection block 25 are implemented, for example, by a processor such as a CPU (not shown), a ROM that stores various programs, a RAM that temporarily supports data from a computation process, and a storage device such as an external storage device.A processor, such as a CPU, reads and executes various programs stored in a ROM and stores the result of the calculation, which is an execution result, in a RAM or external storage device. It should be noted that the control device 40 for a wired steering system is not limited to being installed on an ECU and can be configured to be installed on another electronic control system. The present embodiment is more effective than the first embodiment and can simplify the configuration of the control device 40 for a wired steering system. Fourth embodiment Fig. 8 is a block diagram of a control device of a fourth embodiment according to another embodiment of the present invention. The present embodiment differs from the first embodiment in that a control device 50 for a wired steering system comprises a block of a switch 34a, and the switch 34a block inputs and selects and outputs any one of the following: the setting of a manual control of a feedback mode, the output from a block for maximum element selection 25, and the output from a block for rack force estimation 22 (a value obtained by converting an estimated rack force into a torque for a FBA). The same components as in the first embodiment are designated with the same reference numerals, and any description that overlaps with the first embodiment is omitted. As shown in Fig. 8, the control device 50 for a wired steering system according to the present embodiment comprises a base SAT block 21, a rack force estimation block 22, a gain K block 23, a dead zone block 24, a maximum element selection block 25, and a switch block 34a. Here, the control device 20 for a wired steering system is installed on an ECU, and a base SAT block 21, a rack force estimation block 22, a gain K block 23, a dead zone block 24, a maximum element selection block 25, and a switch block 34a are implemented, for example, by a processor such as a CPU (not shown), a ROM that stores various programs, a RAM that temporarily supports data from a computational process, and a storage device such as an external storage device.A processor, such as a CPU, reads and executes various programs stored in a ROM and stores the result of the calculation, which is an execution result, in a RAM or an external storage device. It should be noted that the control device 50 for a wired steering system is not limited to being installed on an ECU and can be configured to be installed on another electronic control system. Furthermore, the block of switch 34a can be implemented in hardware. The setting of a feedback mode with manual control, which can be entered into a block of switch 34a, which forms the control device 50 for a wired steering system according to the present embodiment, includes whether a driver selects the FBA torque feedback or whether an active BLC is selected, so that the feedback of the rack force estimation is carried out at all times. The control device 50 for a wired steering system according to the present embodiment is not limited to the configuration shown in Fig. 8. For example, instead of a dead zone block 24 and a maximum element selection block 25 shown in Fig. 8, a deviation calculation block 31, a relay block 22, a delay block 23, a switch block 34, and a transition smoothing block 35, as described in the second embodiment, may be included. Furthermore, the configuration may be designed such that a dead zone block 24 shown in Fig. 8 is not included. According to the present embodiment, in addition to the effects described above in the first to third embodiments, it is possible, even in a case where a driver feels that comfort is being compromised by the selection of an automatically performed BLC, to switch to a feedback mode with manual control in order to maintain comfort. It should be noted that a configuration referred to as a "block" in the first to fourth embodiments may also be referred to as a "section". In particular, for example, a "block of the base SAT 21" may be referred to as "base SAT section 21" and a "block for rack force estimation 22" may be referred to as "rack force estimation section 22", and the same applies to the other components. Furthermore, the present invention is not limited to the foregoing embodiment and comprises a multitude of variants. For example, the foregoing embodiment is described in detail for ease of understanding of the present invention, and the present invention is not necessarily limited to one that includes all of the described configurations. Moreover, a section of a configuration of a particular embodiment can be replaced by a configuration of another embodiment, and a configuration of a particular embodiment can also be added to a configuration of another embodiment. Reference symbol list 1 Wired steering system 11 Steering wheel 12 FBA motor (first motor) 13 RWA motor (second motor) 14 Ball screw 15 Rack 20, 30, 40, 50 Control device 21 Base SAT 22 Rack force estimation 23 Gain K 24 Dead zone 25 Maximum element selection 31 Deviation calculation 32 Relay 33 Delay 34, 34a Switch 35 Transition smoothing

Claims

Control device (20, 30, 40, 50) for a wire-operated steering system comprising a first motor (12) designed to control the steering via a feedback actuator, and a second motor (13) designed to control a steering angle of a wheel via a road wheel actuator, and capable of bidirectionally controlling the first motor (12) and the second motor (13), wherein the control device (20, 30, 40, 50) for a wire-operated steering system comprises: a basic SAT section (21) designed to obtain a simulated feedback actuator torque based on an angle of the first motor (12) and a vehicle speed; and a rack force estimation section (22) designed to estimate a rack force as a reaction force based on a steering angle of the wheel and a road wheel actuator.wherein a first control mode for controlling a simulated feedback actuator torque of the first motor (12) and a second control mode for controlling the first motor (12) based on a reaction force estimated by the rack force estimation section (22) are included, wherein a switch between the first control mode and the second control mode is provided based on an output of the basic SAT section (21) and an output of the rack force estimation section (22), characterized by a subtraction section designed to subtract an estimated rack force, estimated by the rack force estimation section (22), from a simulated feedback actuator torque obtained by the basic SAT section (21); and a switch section designed to output an estimated rack force from the subtraction section.which is estimated by the rack force estimation section (22), or to select a simulated feedback actuator torque obtained by the basic SAT section (21), wherein a feedback actuator torque can be determined based on an output of the switch section. Control device (20, 30, 40, 50) for a wired steering system according to claim 1, further characterized by a section for selecting a maximum element designed to compare a simulated feedback actuator torque obtained by the base SAT section (21) with an estimated rack force estimated by the rack force estimation section (22) and to select and output a maximum output as feedback actuator torque. Control device (20, 30, 40, 50) for a wired steering system according to claim 2, further characterized by a dead zone section (24) designed to remove noise contained in an estimated rack force estimated by the rack force estimating section (22). Control device (20, 30, 40, 50) for a wired steering system according to claim 1, further characterized by a transition smoothing section (35) which is able to reduce a steep change in value which occurs when the feedback actuator torque is switched from an estimated rack force, which is estimated by the rack force estimation section (22), to a simulated feedback actuator torque, which is obtained by the base SAT section (21). Control device (20, 30, 40, 50) for a wired steering system according to claim 1, further characterized by a switch section configured to select an estimated rack force estimated by the rack force estimator section (22), a simulated feedback actuator torque obtained by the base SAT section (21), or the setting of a feedback mode with manual control, wherein the setting of a feedback mode with manual control is configured to use an estimated rack force estimated by the rack force estimator section (22) or a simulated feedback actuator torque obtained by the base SAT section (21) as the feedback actuator torque. Control method for a wired steering system with a first motor (12) controlling the steering via a feedback actuator and with a second motor (13) controlling a steering angle of a wheel via a road wheel actuator, and which is capable of controlling the first motor (12) and the second motor (13) bidirectionally, wherein the control method for the wired steering system comprises: obtaining a simulated feedback actuator torque based on an angle of the first motor (12) and a vehicle speed by means of a basic SAT section (21); estimating a rack force as a reaction force based on a steering angle of the wheel and a road wheel actuator by means of a rack force estimation section (22);and switching, based on the output of the basic SAT section (21) and the output of the rack force estimation section (22), between a first control mode for controlling a simulated feedback actuator torque of the first motor (12) and a second control mode for controlling the first motor (12) based on a reaction force estimated by the rack force estimation section, wherein the control method is characterized by subtracting an estimated rack force, estimated by the rack force estimation section, from a simulated feedback actuator torque obtained by the basic SAT section (21) by a subtraction section;Selecting an output of the subtraction section, an estimated rack force estimated by the rack force estimation section (22), or a simulated feedback actuator torque obtained by the basic SAT section (21), by means of a switch section; and determining a feedback actuator torque based on the output of the switch section. Control method for a wired steering system according to claim 6, further characterized by comparing a simulated feedback actuator torque obtained by the basic SAT section (21) with an estimated rack force estimated by the rack force estimation section (22), and selecting and outputting the maximum output as feedback actuator torque. Control method for a wired steering system according to claim 7, further characterized by removing noise contained in an estimated rack force estimated by the rack force estimation section (22) by means of a dead zone section. Control method for a wired steering system according to claim 6, further characterized in that a steep change in value is reduced by a transition smoothing section, which occurs when the feedback actuator torque is switched from an estimated rack force, which is estimated by the rack force estimation section (22), to a simulated feedback actuator torque, which is obtained by the base SAT section (21). Control method for a wired steering system according to claim 6, further characterized by the selection of an estimated rack force estimated by the rack force estimation section (22), a simulated feedback actuator torque obtained by the base SAT section (21), or the setting of a feedback mode with manual control by a switch section, wherein the setting of a feedback mode with manual control uses an estimated rack force estimated by the rack force estimation section (22) or a simulated feedback actuator torque obtained by the base SAT section (21) as a feedback actuator torque.

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