JP2024124231A - Steering gear - Google Patents

Abstract

To detect a relief mode for securing temporary steering.SOLUTION: A steering device 100 comprises a steering mechanism 150, a hydraulic mechanism 140, a first electric motor 111 that applies first torque to a steering shaft body 119, and a control device 130 that controls the first electric motor 111. The control device 130 comprises: a rotation angle obtaining part 131 that obtains a rotation angle at which the steering shaft body 119 is rotated; a torque obtaining part 132 that obtains second torque that is inputted to the steering shaft body 119; a hydraulic state obtaining part 133 that obtains state information showing a state of the hydraulic mechanism 140; a turning-defect detecting part 134 that detects turning defect of a turning wheel 220 on the basis of the first torque, the second torque and the rotation angle; and a discriminating part 135 that when the turning defect is detected, discriminates whether or not a mode is a relief mode in which the turning wheel 220 can be turned by increasing output of the first electric motor 111, using the state information.SELECTED DRAWING: Figure 2

Description

The present invention relates to a steering device equipped with an electric actuator and a hydraulic actuator.

Conventionally, steering devices equipped with electric actuators and hydraulic actuators have been used in large vehicles. For example, the steering device described in Patent Document 1 distributes the steering assist torque provided by the electric actuator and the steering assist torque provided by the hydraulic actuator according to the vehicle speed.

JP 2006-213094 A

The inventor has discovered that in a steering device equipped with electric and hydraulic actuators, depending on the failure condition of the hydraulic actuator, it may be possible to provide steering assistance by using an electric actuator.

The present invention was made based on the inventor's findings, and aims to provide a steering device that can isolate failure modes of a hydraulic actuator while allowing steering to continue using an electric actuator.

In order to achieve the above object, a steering device according to the present invention includes a steering mechanism that rotates a steering shaft to steer the steered wheels, a hydraulic mechanism that applies an auxiliary driving force to the steering mechanism, a first electric motor that applies a first torque to the steering shaft, and a control device that controls the first electric motor. The control device includes a rotation angle acquisition unit that acquires a rotation angle at which the steering shaft is rotated, a torque acquisition unit that acquires a second torque input to the steering shaft, a hydraulic state acquisition unit that acquires state information indicating the state of the hydraulic mechanism, a steering failure detection unit that detects a steering failure of the steered wheels based on the first torque, the second torque, and the rotation angle, and a discrimination unit that, when the steering failure is detected, uses the state information to determine whether or not the device is in a rescue mode in which the steered wheels can be steered by increasing the output of the first electric motor.

According to the present invention, even if the steered wheels fail to turn properly in response to the input to the steering shaft, the output of the first electric motor can be increased to steer the wheels as a temporary measure, ensuring safety during vehicle travel.

FIG. 1 is a diagram illustrating a steering system including a steering device. FIG. 2 is a block diagram showing the functional configuration of the control device. FIG. 3 is a block diagram showing a functional configuration of a torque feedback control having a disturbance observer used for detecting a steering failure. FIG. 4 is a graph used to detect steering failure. FIG. 5 is a block diagram showing a functional configuration of a steering angle feedback control having a disturbance observer used for steering control. FIG. 6 is a diagram illustrating a schematic diagram of another example of a steering system.

Below, an embodiment of the steering device according to the present invention will be described with reference to the drawings. Note that the following embodiment is presented as an example to explain the present invention, and is not intended to limit the present invention. For example, the shapes, structures, materials, components, relative positional relationships, connection states, numerical values, mathematical expressions, the contents of each step in the method, and the order of each step shown in the following embodiment are merely examples, and may include contents not described below. In addition, while geometric expressions such as parallel and orthogonal may be used, these expressions do not indicate mathematical strictness, and include substantially acceptable errors, deviations, and the like. In addition, expressions such as simultaneous and identical also include substantially acceptable ranges.

The drawings are schematic diagrams in which emphasis, omissions, or proportions have been appropriately adjusted in order to explain the present invention, and may differ from the actual shapes, positional relationships, and proportions.

In addition, multiple inventions may be collectively described below as a single embodiment. Some of the content described below is also described as an optional component of the present invention.

Figure 1 is a schematic diagram of a steering system 200 equipped with a steering device. The steering system 200 is a system that steers steered wheels 220 according to a target steering angle and controls the traveling direction of a vehicle in which the steering system 200 is installed. The steering system 200 includes a steering device 100, an operation input means 210, and an automatic control device 250.

The operation input means 210 is a device that outputs a target steering angle intended by the driver when the driver operates an operating member 211 such as a steering wheel. In the present embodiment, as shown in FIG. 1, the operation input means 210 includes an operating member 211, an operating shaft 212, a target steering angle detection means 213, and a torque detection device 214. Note that the operation input means 210 may also include a reaction force device or the like.

The operating shaft 212 is a rod-shaped member that is mechanically connected to the operating member 211 and rotates in response to the operation of the operating member 211. In this embodiment, the operating shaft 212 is connected to a reaction means (not shown), and a reaction force is applied to the driver operating the operating member 211 to give the driver a steering sensation according to the driving state.

The manner of connection between the operating shaft 212 and the steering mechanism 150 is not particularly limited. In the present embodiment, the steering shaft 119 and the operating shaft 212 are mechanically connected, and the second torque is applied to the steering mechanism 150 when the driver operates the operating member 211. During automatic driving, the mechanical connection between the operating shaft 212 and the steering shaft 119 may be separated using a clutch or the like.

The target rudder angle detection means 213 is a device that detects the rotation angle of the operating member 211 and outputs it as a target rudder angle. In this embodiment, the target rudder angle detection means 213 detects the rotation of the operating shaft body 212 as the rotation of the operating member 211. The type of the target rudder angle detection means 213 is not particularly limited, but examples include a resolver and a rotary encoder.

The torque detection device 214 detects the second torque input from the operating shaft 212 to the steering shaft 119. The type of the torque detection device 214 is not limited, but in this embodiment, the torque detection device 214 detects the second torque based on the amount of twist of a torsion bar disposed between the operating shaft 212 and the steering shaft 119.

The automatic control device 250 is one of the ECUs (Electronic Control Units) for automatically driving the vehicle equipped with the steering system 200. In this embodiment, the automatic control device 250 acquires information on obstacles outside the vehicle, white lines on the road, traffic lights, etc. from sensors such as a camera 251 and a laser rider 252, and sequentially generates a target steering angle corresponding to automatic driving based on the acquired information and outputs it to the control device 130 of the steering device 100. Note that the control device 130 may acquire an estimated value of the second torque from the automatic control device 250.

The steering device 100 is a device that steers the steered wheels 220 based on a target steering angle to steer the vehicle, and includes a steering mechanism 150, a drive unit 110, a hydraulic mechanism 140, and a control device 130.

The steering mechanism 150 is a mechanism for steering the steered wheels 220. Although there is no particular limitation to the steering mechanism 150, in this embodiment, a rack and pinion is used. Specifically, the steering mechanism 150 includes a pinion shaft 151, a rack shaft 152, and a tie rod 153.

The pinion shaft 151 is a rod-shaped member equipped with a pinion that meshes with a rack provided on the rack shaft 152. The pinion shaft 151 is connected to the steering device 100, and rotates when torque is applied from the drive device 110, moving the rack shaft 152 in the axial direction of the rack shaft 152.

The rack shaft 152 is a member that has a rack on part of its outer periphery that meshes with the pinion shaft 151, converts the rotation of the pinion shaft 151 into the axial movement of the rack shaft 152, and turns the steered wheels 220 via the tie rod 153. A hydraulic mechanism 140 is connected to the rack shaft 152, and an assist force is applied to steer the steered wheels 220 by hydraulic pressure. The rack shaft 152 is housed in a rack housing attached to the vehicle body, and the movement of the rack shaft 152 is guided by the rack housing.

The drive device 110 is connected to the steering mechanism 150 via a steering shaft 119 and applies a first torque to the steering mechanism 150. The configuration of the drive device 110 is not particularly limited, but in this embodiment, the drive device 110 includes a first electric motor 111 and a reduction gear 112, and the output shaft (not shown) of the first electric motor 111 is connected to the steering shaft 119 via the reduction gear 112. The first torque, which is the torque applied by the drive device 110 to the steering mechanism 150, is significantly smaller than the assist force applied by the hydraulic mechanism 140 to the steering mechanism 150 in a normal state. For example, most of the force that steers the steered wheels 220 is a hydraulic steering force, and the first torque is transmitted to the steering mechanism 150 as a control force for controlling the steering angle and steering direction of the steered wheels 220.

In this embodiment, the drive device 110 is equipped with a rotation angle detection means 113. The rotation angle detection means 113 is a device that detects the rotation angle of the output shaft of the first electric motor 111 and outputs it as a detected rotation angle. The type of the rotation angle detection means 113 is not particularly limited, but in this embodiment, the rotation angle detection means 113 is equipped with a main gear that rotates together with the output shaft of the first electric motor 111 and two driven gears of different diameters that mesh with the main gear, and is capable of detecting not only the rotation angle of the output shaft but also the rotation direction by detecting the rotation of the permanent magnets provided on each of the driven gears using a hall element or the like. The rotation angle detection means 113 may be equipped with a resolver, a rotary encoder, or the like.

The hydraulic mechanism 140 adjusts the hydraulic pressure according to the rotation angle of the pinion shaft 151, etc., and applies the axial force of the rack shaft 152 to the rack shaft 152 as an assist force. Although not limited to any particular type, in this embodiment, the hydraulic mechanism 140 includes a power cylinder 141, a rotary valve 142, an oil pump 143, and a reservoir tank 144.

The power cylinder 141 has a cylinder 146 separated into two spaces by a piston 145, and the piston 145 moves in the axial direction of the rack shaft 152 by adjusting the hydraulic pressure of the oil filled in each of the two spaces. The piston 145 is connected to the rack shaft 152, and a force in the moving direction is applied from the piston 145 to the rack shaft 152.

The rotary valve 142 is a device that adjusts the oil pressure supplied to each of the two spaces separated by the piston 145. The structure of the rotary valve 142 is not particularly limited, but in this embodiment, it is equipped with a torsion bar (not shown) that is interposed in the steering shaft 119 between the pinion shaft 151 and the steering device 100. The rotary valve 142 adjusts the amount of oil pumped from the oil pump 143 to be supplied to one of the two spaces separated by the piston 145 in response to the relative movement between the inner valve and the outer valve caused by the twisting of the torsion bar, and adjusts the amount of excess oil in the other space that is returned to the reservoir tank 144, thereby controlling the operation of the piston 145. In this embodiment, the oil pump 143 is driven by a second electric motor 147.

Figure 2 is a block diagram showing the functional configuration of the control device 130. The control device 130 is a device that controls the first electric motor 111 of the drive device 110 so that the rotation angle of the output shaft corresponds to the target steering angle under normal conditions (when no defect occurs in the hydraulic mechanism 140). The control device 130 also constantly monitors the state of the hydraulic mechanism 140 and detects the occurrence of an abnormality. The control device 130 is equipped with a processor and includes a rotation angle acquisition unit 131, a torque acquisition unit 132, a hydraulic state acquisition unit 133, a steering failure detection unit 134, and a discrimination unit 135 as processing units that are realized by having the processor execute a program. In the case of this embodiment, the control device 130 includes a drive control unit 136.

The rotation angle acquisition unit 131 acquires the rotation angle of the input shaft that rotates the steering shaft 119. There are no particular limitations on where the rotation angle is acquired from. In this embodiment, the operating shaft 212 functions as the input shaft, and the rotation angle acquisition unit 131 acquires the rotation angle from the rotation angle detection means 113.

The torque acquisition unit 132 acquires the first torque and the second torque. The first torque is the torque applied to the steering shaft 119 by the first electric motor 111 of the drive device 110. The second torque is the torque input to the steering shaft 119, and in this embodiment, the torque input from the operation input means 210 to the steering shaft 119 via the operation shaft 212. The source from which the torque information is acquired is not particularly limited. In this embodiment, the torque acquisition unit 132 acquires the second torque from a torque detection device 214 provided on the operation input means 210 side of the steering shaft 119. In addition, the torque acquisition unit 132 acquires the torque information based on the amount of twist of a torsion bar attached to the rotary valve 142 of the hydraulic mechanism 140.

The hydraulic state acquisition unit 133 acquires state information indicating the state of the hydraulic mechanism 140. The state information indicating the state of the hydraulic mechanism 140 is, for example, the amount of oil, the oil pressure, the oil temperature, etc. of the hydraulic mechanism 140. In the present embodiment, the state information includes the rotation speed of the second electric motor 147 that drives the oil pump 143. The source from which the state information is acquired is not limited, but in the present embodiment, the oil amount is acquired from a level gauge 161 provided in the reservoir tank 144, the oil pressure is acquired from a hydraulic sensor 162 provided in the reservoir tank 144, and the oil temperature is acquired from an oil temperature sensor 163 provided in the reservoir tank 144. In addition, the rotation speed of the second electric motor 147 is acquired from a rotation sensor (not shown) provided in the second electric motor 147, an instruction value for driving the second electric motor 147, etc.

The steering failure detection unit 134 detects steering failure of the steered wheels 220 based on the dynamic relationship between the first torque, the second torque acquired by the torque acquisition unit 132, and the rotation angle acquired by the rotation angle acquisition unit 131. The method of detecting steering failure is not limited. For example, examples of the method of detecting steering failure include detection using a disturbance observer and detection using a graph (table) that maps the relationship between the combined value of the first torque and the second torque and the behavior of the rotation angle.

Specific examples of a method for detecting poor steering using a disturbance observer include the following. Using a two-degree-of-freedom model in which the operating shaft 212, the torsion bar provided on the torque detection device 214, the steering shaft 119, the torsion bar attached to the rotary valve 142, and (the ground) are connected in series, torque feedback control using a disturbance observer of the "first torque, second torque" model can be illustrated by the block diagram shown in Figure 3. In this case, when the absolute value of the estimated value of the input shaft disturbance is large, that is, when the actual movement of the input shaft is large compared to the behavior of the input shaft predicted by the normative model, it can be estimated that a poor steering state exists. Furthermore, when the estimated value of the input shaft disturbance > threshold, and the sign of the estimated value of the input shaft disturbance is in a direction that hinders the rotation of the input shaft, and the estimated value of the input shaft disturbance < the sum of the first torque and the second torque, it is estimated that a poor steering state exists.

As a specific example of a steering failure graph, as shown in FIG. 4, a graph in which the horizontal axis is the sum of the first torque and the second torque, and the vertical axis is the second time differential of the rotation angle, i.e., the rotation angle acceleration, can be exemplified. In this graph, if the first torque and the second torque acquired by the torque acquisition unit 132, and the value obtained by the rotation angle acquisition unit 131, which are twice differentiated by time, are included in the hatched trapezoidal area 261, it can be determined that a steering failure has occurred. Note that the diagonal line in the graph indicates a normal state 262. Also, the line overlapping the horizontal axis in the graph indicates a blocking state 263. Note that the blocking state refers to a state in which the estimated value of the input shaft disturbance approximately matches the sum of the first torque and the second torque.

When the steering failure detection unit 134 detects a steering failure, the discrimination unit 135 uses the state information acquired by the hydraulic state acquisition unit 133 to determine whether or not the vehicle is in a rescue mode in which the steering of the steered wheels 220 is possible by increasing the output of the first electric motor 111.

For example, when the discrimination unit 135 determines that the oil volume, oil pressure, and oil temperature acquired as the status information are normal, it discriminates that the first rescue mode is in effect because the steering failure is due to a malfunction of the hydraulic mechanism 140, regardless of the rotation speed of the second electric motor 147. The first rescue mode is a mode in which, for example, a hydraulic valve is stuck, and the steering mechanism 150 can be operated as a temporary rescue by increasing the first torque applied by the drive unit 110 to the steering shaft 119, thereby turning the steered wheels 220.

In addition, when the discrimination unit 135 determines that the amount of oil acquired as the status information is less than normal and is equal to or less than a predetermined oil amount threshold, and that the oil temperature state is normal, it discriminates that the second rescue mode is in effect, since the steering failure is due to a malfunction of the hydraulic mechanism 140, regardless of the hydraulic pressure and the rotation speed of the second electric motor 147. The second rescue mode is a mode in which, for example, an oil leak from the hydraulic mechanism 140 occurs, and the steering mechanism 150 can be operated as a temporary rescue by increasing the first torque applied by the drive unit 110 to the steering shaft 119, thereby turning the steered wheels 220.

In addition, when the discrimination unit 135 determines that the oil pressure acquired as the status information and the rotation speed of the second electric motor 147 are abnormal and that the oil temperature state is normal, it determines that the third rescue mode is in effect, assuming that the steering failure is due to a malfunction of the hydraulic mechanism 140 regardless of the amount of oil. The third rescue mode is a mode in which, for example, a malfunction of the oil pump 143 can be detected and the steering mechanism 150 can be operated as a temporary rescue by increasing the first torque applied by the drive unit 110 to the steering shaft 119, thereby turning the steered wheels 220.

In the normal mode in which the hydraulic mechanism 140 is in a normal state, the drive control unit 136 controls the drive unit 110 by PID control or the like so that the steering angle of the actual steered wheels 220 coincides with the target steering angle based on the acquired target steering angle, and applies a first torque to the steering shaft 119. When the discrimination unit 135 discriminates the first rescue mode, the second rescue mode, or the third rescue mode, the drive control unit 136 controls the drive unit 110 so that the first torque is stronger than in the normal mode. For example, the drive control unit 136 generates in the drive unit 110 a torque equal to or comparable to the assist force applied by the hydraulic mechanism 140 to the rack shaft 152 of the steering mechanism 150 in the normal mode. As a result, even in a situation in which a malfunction occurs in the hydraulic mechanism 140 and an assist force cannot be applied to the rack shaft 152, the steered wheels 220 can be turned by the first torque (assist torque) applied by the drive control unit 136, and the vehicle can be temporarily steered to a safe position such as the shoulder of the road, and the vehicle can be safely stopped while maintaining curved driving.

As a specific example of control of the drive device 110, for example, in the case of manual driving, a control that increases the compensation amount for the second torque with respect to an assist map that shows the relationship between the second torque and the first torque can be exemplified. Such an increase in the compensation amount may be changed according to the vehicle speed.

In addition, for example, in the case of automatic steering, when the first electric motor 111 is controlled using an angle servo controller that uses PID, the PID gain for the deviation (steering angle deviation) between the command steering angle for automatic steering and the actual steering angle can be increased to compensate for tracking of the target steering angle in rescue mode.

For example, in the case of automatic steering, when the first electric motor 111 is controlled using an angle servo controller that uses a disturbance observer having a reference model as shown in FIG. 5, the PID gain of the controller that outputs a target torque for the steering angle deviation can be increased, and the inertia that the disturbance observer's reference model has as a parameter can be replaced with the inertia of the rescue mode, thereby compensating for tracking the target steering angle in the rescue mode. Note that the inertia of the rescue mode can be a value identified in advance by experiments, a design value, etc.

The steering device 100 according to the embodiment includes a steering mechanism 150 that rotates the steering shaft 119 to steer the steered wheels 220, a hydraulic mechanism 140 that applies an auxiliary driving force to the steering mechanism 150, a first electric motor 111 that applies a first torque to the steering shaft 119, and a control device 130 that controls the first electric motor 111. The control device 130 includes a rotation angle acquisition unit 131 that acquires the rotation angle of the input shaft that rotates the steering shaft 119, a torque acquisition unit 132 that acquires the second torque input to the steering shaft 119, a hydraulic state acquisition unit 133 that acquires state information indicating the state of the hydraulic mechanism 140, a steering failure detection unit 134 that detects steering failure of the steered wheels 220 based on the first torque, the second torque, and the rotation angle, and a discrimination unit 135 that uses the state information to determine whether or not a rescue mode is in which the steered wheels 220 can be steered by increasing the output of the first electric motor 111 when a steering failure is detected.

With this steering device 100, in the event of a steering failure in which the steered wheels 220 are unintentionally steered despite the second torque being input to the steering shaft 119, the vehicle can be stopped in a safe position by switching to a rescue mode in which steering is temporarily possible by increasing the output of the first electric motor 111 due to a failure of the hydraulic mechanism 140.

The hydraulic mechanism 140 also includes an oil pump 143 and a second electric motor 147 that drives the oil pump 143, and the hydraulic state acquisition unit 133 acquires the rotation speed of the second electric motor 147 as one piece of state information, and the discrimination unit 135 may use the rotation speed included in the state information to determine whether or not the rescue mode is in effect.

With this type of steering device 100, it is possible to further increase the number of states of the hydraulic mechanism 140 that are determined to be in the rescue mode when steering is poor.

The hydraulic state acquisition unit 133 may acquire the oil volume, oil pressure, and oil temperature of the hydraulic mechanism 140 as state information, and if the determination unit 135 determines that the oil volume, oil pressure, and oil temperature are normal, it may determine that the first rescue mode is due to a malfunction of the hydraulic mechanism 140.

The hydraulic state acquisition unit 133 may acquire the oil amount and oil temperature of the hydraulic mechanism 140 as state information, and when the determination unit 135 determines that the oil amount has decreased below normal and that the oil temperature state is normal, it may determine that the second rescue mode is due to an oil abnormality in the hydraulic mechanism 140.

The hydraulic state acquisition unit 133 may acquire the hydraulic pressure and oil temperature of the hydraulic mechanism 140 as state information, and when the discrimination unit 135 determines that the hydraulic pressure and rotation speed states are abnormal and that the oil temperature state is normal, it may discriminate that the third rescue mode is due to an abnormality in the second electric motor 147.

By further classifying the rescue modes in this way, it becomes possible to appropriately change the control that increases the torque generated by the first electric motor 111.

The present invention is not limited to the above-described embodiment. For example, the components described in this specification may be combined in any way, or some of the components may be removed to create another embodiment of the present invention. The present invention also includes modifications that are made to the above-described embodiment by those skilled in the art without departing from the spirit of the present invention, i.e., the meaning of the words in the claims.

For example, as shown in FIG. 6, the steering system 200 may be a so-called steer-by-wire system in which the operating shaft 212 and the steering mechanism 150 are not mechanically connected. In this case, at least one of the first torque and the second torque may be estimated from the control information of the first electric motor 111.

The present invention can be used in vehicles, particularly large vehicles, agricultural vehicles, construction vehicles, and the like, which require a large force to steer the steered wheels 220.

100... steering device, 110... drive device, 111... first electric motor, 112... reducer, 113... rotation angle detection means, 119... steering shaft body, 130... control device, 131... rotation angle acquisition unit, 132... torque acquisition unit, 133... hydraulic state acquisition unit, 134... steering failure detection unit, 135... discrimination unit, 136... drive control unit, 140... hydraulic mechanism, 141... power cylinder, 142... rotary valve, 143... oil pump, 144... reservoir tank, 145... piston, 146... cylinder, 147... second electric motor 150...Steering mechanism, 151...Pinion shaft, 152...Rack shaft, 153...Tie rod, 161...Level gauge, 162...Oil pressure sensor, 163...Oil temperature sensor, 200...Steering system, 210...Operation input means, 211...Operation member, 212...Operation shaft body, 213...Target steering angle detection means, 214...Torque detection device, 220...Steering wheel, 250...Automatic control device, 251...Camera, 252...Laser lidar, 261...Trapezoidal area, 262...Normal state, 263...Blocking state

Claims (5)

A steering mechanism that rotates a steering shaft to steer the steered wheels;
a hydraulic mechanism that applies an auxiliary driving force to the steering mechanism;
A first electric motor that applies a first torque to the steering shaft;
a control device for controlling the first electric motor,
The control device includes:
a rotation angle acquisition unit that acquires a rotation angle at which the steering shaft is rotated;
A torque acquisition unit that acquires a second torque input to the steering shaft;
a hydraulic state acquisition unit that acquires state information indicating a state of the hydraulic mechanism;
a turning failure detection unit that detects a turning failure of the steered wheels based on the first torque, the second torque, and the rotation angle;
a discrimination unit that, when the steering failure is detected, determines whether or not the steering is in a rescue mode in which the steered wheels can be steered by increasing the output of the first electric motor, using the status information. The hydraulic mechanism includes:
An oil pump,
a second electric motor that drives the oil pump,
The hydraulic state acquisition unit is
The rotation speed of the second electric motor is acquired as state information;
The discrimination unit is
The steering apparatus according to claim 1 , wherein it is determined whether or not the rescue mode is in effect based on the state information including the number of revolutions. The hydraulic state acquisition unit is
Acquiring the amount of oil, the oil pressure, and the oil temperature of the hydraulic mechanism as status information;
3. The steering device according to claim 1, wherein the determination unit determines that the first rescue mode is due to a malfunction of the hydraulic mechanism when the determination unit determines that the oil amount, the oil pressure, and the oil temperature are normal. The hydraulic state acquisition unit is
Acquiring the amount of oil and the oil temperature of the hydraulic mechanism as status information;
3. The steering device according to claim 1, wherein the discrimination unit discriminates that the second rescue mode is due to an oil abnormality in the hydraulic mechanism when the discrimination unit determines that the oil amount has decreased below normal and that the oil temperature state is normal. The hydraulic state acquisition unit is
Acquiring the oil pressure and the oil temperature of the hydraulic mechanism as status information;
3. The steering device according to claim 2, wherein the discrimination unit discriminates that the third rescue mode is due to an abnormality in the second electric motor when it determines that the oil pressure and the rotation speed are abnormal and that the oil temperature is normal.