JP5271551B2 - Steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compensate for the inertia of a reaction motor in a steering device without being equipped with a torque sensor. <P>SOLUTION: The steering device includes a steering wheel 2 operated by a driver, wheels 10 mechanically separated from the steering wheel 2, a steering motor 11 to steer the wheels 10, the reaction motor 5 linked to the steering wheel 2 to impart a reaction force, a steering motor control means to control the steering motor 11 according to an operation input to the steering wheel 2, and a reaction motor control means to control the reaction motor 5, wherein the reaction motor control means compensates for the inertia based on a current flowing to the reaction motor 5. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a steering device in which an operator operated by a driver and a steered wheel are mechanically separated or can be connected from a mechanically separated state.

  In a so-called steer-by-wire type steering device in which the operator operated by the driver and the steered wheel are mechanically separated, the steered wheel is rotated according to the operation input to the steering wheel (operator) by the driver. A steering motor for steering and a reaction force motor for applying an appropriate reaction force when the driver operates the steering wheel are provided, and both motors are controlled independently.

  The reaction force control method is based on a deviation between a target value (for example, a target turning angle) set based on an operation input to the steering wheel and an actual control amount (for example, an actual turning angle) corresponding thereto. It is known to control the command current (duty ratio) to the reaction force motor (see, for example, Patent Document 1).

  By the way, if the rotational inertia of the reaction force motor cannot be ignored, at the moment when the driver starts operating the steering wheel, it is difficult to move the steering wheel immediately due to the influence of the inertia of the reaction force motor, and the steering wheel is operated. Even when trying to stop the steering wheel while the vehicle is running, an event occurs that it is difficult to stop the steering wheel immediately due to the inertia of the reaction force motor. When such an event occurs, the driver may feel uncomfortable with the operation feel.

Therefore, during the reaction force control, an instruction current to the reaction force motor is calculated in order to compensate for the rotation inertia of the reaction force motor. This rotational inertia compensation is performed based on the output of the torque sensor by installing a torque sensor between the steering wheel and the reaction force motor.
Japanese Patent No. 3897293

  However, if a torque sensor is provided to compensate for the rotational inertia of the reaction force motor, there is a problem that the steering system is increased in size and the mounting property on the vehicle is impaired. There is also a problem that the installation of the torque sensor causes an increase in cost.

  Accordingly, the present invention provides a steering device that can perform inertia compensation of a reaction force motor without providing a torque sensor.

The steering device according to the present invention employs the following means in order to solve the above problems.
According to the first aspect of the present invention, an operator operated by a driver (for example, a steering wheel 2 in an embodiment to be described later) and the operator are mechanically separated or connectable from a mechanically separated state. A steered wheel (for example, a wheel 10 in an embodiment to be described later), a steered motor for steering the steered wheel (for example, a steered motor 11 in an embodiment to be described later), and the operation element. A reaction force motor for applying a reaction force to the operation element (for example, a reaction force motor 5 in an embodiment described later), a turning motor control means for controlling the turning motor in response to an operation input to the operation element, Reaction force motor control means for controlling the reaction force motor (for example, reaction force motor control unit 21 in an embodiment described later), and the reaction force motor control means is based on a current flowing through the reaction force motor. Performs inertia compensation Te, wherein performs feedback control such that the current flowing through the reaction motor coincides with the target current of the reaction force motor, the target current of the reaction force motor, virtual torsion bar current, damping current and A steering device characterized in that the virtual torsion bar current is calculated based on an angular deviation between a steering angle of the operating element and a turning angle of the steered wheel. For example, a steering device 1) in an embodiment described later.
With such a configuration, inertia compensation can be performed based on the current flowing through the reaction force motor, so that a torque sensor for use in inertia compensation of the reaction force motor becomes unnecessary.

  According to the first aspect of the present invention, since inertia compensation can be performed based on the current flowing through the reaction force motor, a torque sensor used to compensate for the rotation inertia of the reaction force motor becomes unnecessary. The number of points can be reduced, the system can be simplified, and the cost can be reduced. Moreover, the mounting property to a vehicle improves.

Embodiments of a steering apparatus according to the present invention will be described below with reference to the drawings of FIGS.
<Example 1>
First, the steering device according to the first embodiment will be described.
As shown in FIG. 1, a steering device 1 is installed on a steering shaft 3 to detect a steering wheel (operator) 2 operated by a driver and a steering angle (operation input amount) of the steering wheel 2. A steering angle sensor (operation input amount detecting means) 4, a reaction force motor 5 for applying a reaction force to the steering wheel 2, a reduction gear 6 installed between the steering shaft 3 and the reaction force motor 5, and left and right wheels A rack shaft 9 connected to the (steered wheel) 10 via a knuckle arm 7 or the like, a steering motor 11 that steers the wheel 10 by moving the rack shaft 9 in the axial direction, and the axial position of the rack shaft 9 A turning angle sensor (steering angle detection means) 12 for detecting the turning angle of the wheel 10 and an electronic control unit (ECU) 20 for controlling the reaction force motor 5 and the turning motor 11 are provided. The reduction gear 6 includes a worm gear 6a provided on the output shaft of the reaction motor 5 and a worm wheel gear 6b provided on the steering shaft 3 and meshing with the worm gear 6a.
The steering device 1 is a so-called steer-by-wire steering device in which a steering wheel 2 and a wheel 10 that is a steered wheel are mechanically separated.

  The steering angle sensor 4 outputs an electrical signal corresponding to the detected steering angle, and the turning angle sensor 12 outputs an electrical signal corresponding to the detected turning angle to the ECU 20. In addition, vehicle speed information, yaw rate information, lateral acceleration (lateral G) information, and the like are input to the ECU 20 as vehicle information 13.

The ECU 20 controls a steered motor 11 (steered motor control means) that controls the steered motor 11 in response to an operation input to the steering wheel 2, and a reaction force motor control that controls the reaction force motor as shown in FIG. Part (reaction force motor control means) 21.
The content of the steered motor control unit is the same as that of the prior art and is a well-known technology, and thus detailed description thereof is omitted. For example, the steering direction of the steering wheel 2 detected by the steering angle sensor 4 is included. A target turning angle for the wheel 10 is set according to the steering angle, and further, for this target turning angle, steering for stabilizing vehicle behavior against vehicle motion disturbance based on the yaw rate information of the vehicle information 13 and the like. Angle correction is performed, and the supply current to the steered motor 11 is controlled so that the actual steered angle of the wheel 10 detected by the steered angle sensor 12 coincides with the corrected target steered angle.

Next, the reaction force motor control unit 21 which is a characteristic part of the present invention will be described in detail with reference to FIG.
The reaction force motor control unit 21 supplies a reaction force motor target current calculation unit 22 for calculating the target current of the reaction force motor 5 and the reaction force motor 5 so that the actual current flowing through the reaction force motor 5 matches the target current. And a current feedback controller 27 for controlling the duty ratio of the supply current.

  The reaction force motor target current calculation unit 22 includes a virtual torsion bar current calculation unit 23, a damping current calculation unit 24, and an inertia compensation current calculation unit 25, and the virtual force calculated by each calculation unit 23, 24, 25. The torsion bar current Itb, the damping current Idmp, and the inertia compensation current Iina are added together and output to the adder / subtractor 26 as the target current Ir of the reaction force motor 5 (Ir = Itb + Idmp + Iina).

The virtual torsion bar current calculation unit 23 is based on the angular deviation between the steering angle θh of the steering wheel 2 detected by the steering angle sensor 4 and the turning angle θp of the wheel 10 detected by the turning angle sensor 12. The virtual torsion bar current Itb is calculated from the equation (1). In addition,
ktb is a virtual torsion bar coefficient.
Itb = ktb · (θh−θp) (1)

The damping current calculation unit 24 calculates the damping current Idmp from the equation (2) based on the differential value of the steering angle θh of the steering wheel 2 detected by the steering angle sensor 4, that is, the steering angular velocity dθh / dt. Note that kdmp is a damper coefficient.
Idmp = kdmp · (dθh / dt) (2)

The inertia compensation current calculation unit 25 calculates an inertia compensation current Iina in order to correct the rotation inertia of the reaction force motor 5.
Conventionally, in order to correct the rotational inertia of the reaction force motor 5, the inertia compensation current Iina is calculated by the equation (3) using the signal value (torque value τ) of the torque sensor provided on the steering shaft. In the first embodiment, the current value (actual current) i of the reaction force motor 5 is substituted, and the inertia compensation current Iina is calculated by the equation (4).
Note that kina ₁ , kina ₂ , Kina ₁ , and Kina ₂ are inertia correction coefficients, and τ is a load torque of the reaction force motor 5.
Iina = (kina ₁ · τ) + {(kina ₂ · (dτ / dt)} (3)
Iina = (Kina ₁ · i) + {(Kina ₂ · (di / dt)} (4)

The mechanism by which the function of inertia correction can be achieved by using Expression (4) instead of Expression (3) will be described in detail later.
If inertia correction can be performed by the energizing current value i of the reaction force motor as in the equation (4), the torque sensor value used in the conventional technique becomes unnecessary, so that the torque sensor can be eliminated.

  The adder / subtractor 26 includes a target current Ir output from the reaction force motor target current calculation unit 22 and an energization current (actual current) flowing through the reaction force motor 5 detected by a current sensor 32 provided in the reaction force motor drive circuit 31. ) Calculate the current deviation Δi from i and output it to the current feedback controller 27.

  Based on the input current deviation Δi, the current feedback controller 27 controls the duty ratio of the supply current to the reaction force motor 5 so that the actual current i flowing through the reaction force motor 5 matches the target current Ir.

Next, a mechanism by which the function of inertia correction can be achieved by using Expression (4) instead of Expression (3) will be described.
First, the equation of motion of the system from the steering wheel 2 to the worm wheel gear 6b is expressed by equation (5).
{Jh · (d ² θh / dt ² )} + {Ch · (dθh / dt)} = τd− (n · τm) (5)
In addition, each code | symbol is as follows.
θh: Steering angle of steering wheel 2 Jh: Rotational inertia coefficient Ch: Viscous resistance coefficient τd: Input torque τm input by driver to steering wheel 2: Load torque of reaction force motor 5: Reduction ratio of reduction gear 6

Further, the equation of motion of the system from the worm gear 6a to the reaction force motor 5 is expressed by equation (6).
{Jm · (d ² θm / dt ² )} + {Cm · (dθm / dt)} = (kt · i) + τm (6)
In addition, each code | symbol is as follows.
θm: rotation angle of reaction force motor 5 Jm: rotational inertia coefficient Cm: viscous resistance coefficient kt: torque constant τm: load torque i of reaction force motor 5: energization current (actual current) of reaction force motor 5

If the load torque τm of the reaction force motor 5 is eliminated from the equations (5) and (6), the equation (7) is obtained.
τd = (− n · kt · i) + n · {Jm · (d ² θm / dt ² ) + Cm · (dθm / dt)} + {Jh · (d ² θh / dt ² ) + Ch · (dθh / dt) } Expression (7)

Further, since the relationship θm = n · θh is established, the following equation (8) is obtained from the equation (7).
τd = (− n · kt · i) + {(n ² · Jm + Jh) · (d ² θh / dt ² )} + {(n ² · Cm + Ch) · (dθh / dt)} (8)

By the way, the target current Ir of the reaction force motor 5 is represented by Expression (9).
Ir = Itb + Idmp + Iina
= {Ktb · (θh−θp)} + {kdmp · (dθh / dt)} + Iina (9)

Therefore, the differential operation value is expressed by equation (10).
dIr / dt = {ktb · (d (θh−θp) / dt)} + {kdmp · (d ² θh / dt ² ) + (dIina / dt)} (10)

Here, the actual value is controlled to follow the target value by the action of the current feedback controller 27 of the reaction force motor, and when Ir≈i, the first-order differential value is dIr / dt≈di / Since it is dt, the differential value of the current value i of the reaction motor includes approximately the dθh / dt component and the d ² θh / dt ² component as shown in the equation (11). You can think about it.
di / dt≈ {ktb · (d (θh−θp) / dt)} + {kdmp · (d ² θh / dt ² )} + (dIina / dt) (11)
Therefore, the inertia compensation current Iina in the equation (4) including the term di / dt may include a component proportional to the inertia component of the reaction force motor 5 and the steering wheel 2 system.

On the other hand, from the equation (8), it can be seen that the driver's steering torque τd includes an inertia component (proportional to d ² θh / dt ² ). This means that inertia such as the reaction force motor 5 influences the steering operation of the steering wheel 2.

If the inertia compensation current Iina of the equation (4) is used as one component of the target current Ir to the reaction force motor 5, for the reason described above with respect to the equation (11), the component having the same phase relationship as the mechanical rotational inertia ( d ² θh / dt ² ) is included in the target current Ir, which indicates that the inertia of the actual reaction force motor 5 and steering wheel 2 system can be corrected.

As is obvious from the above discussion, in the case where the influence of the inertia of the reaction force motor 5 becomes a problem in the operation of the steering wheel 2 by the driver, the energizing current value (actual current) i of the reaction force motor 5 is Inertia compensation is made approximately by the correction using the equation (4) used, and as a result, the same effect as the method using the conventional torque sensor value can be obtained.
Therefore, since the torque sensor can be eliminated, the number of components of the steering device 1 can be reduced, the system can be simplified, and the cost can be reduced. In addition, the simplification of the system improves the mountability of the steering device 1 on the vehicle.

Note that Kina ₁ and Kina ₂ in the equation (4) are set so that the inertia compensation current Iina in the equation (3) can be approximated by performing an experiment.

<Example 2>
Next, a second embodiment of the present invention will be described with reference to FIG.
In the first embodiment described above, the torque sensor value in the equation (3) is substituted with the current value (actual current) i of the reaction force motor as in the equation (4). 2, an approximate value of the torque sensor is derived from the energization current value i of the reaction force motor 5 and the steering angle θh of the steering wheel 2, thereby adopting a method of substituting the torque sensor value.

First, as shown in the equation (8), the steering torque τd of the driver's steering wheel 2 includes the energization current i of the reaction force motor 5, the steering speed dθh / dt of the steering wheel 2, and the steering acceleration d ² θh of the steering wheel 2. / Dt ² .

Next, generally, the steering torque τd of the driver's steering wheel 2 is equal to the torque sensor value τ.
τd≈τ (12)

Therefore, from the equations (8) and (12), the torque sensor value τ can be approximated as in the equation (13).
τ≈ (−n · kt · i) + {(n ² · Jm + Jh) · (d ² θh / dt ² )} + {(n ² · Cm + Ch) · (dθh / dt)} (13)

  The constants n, kt, Jm, Jh, Cm, and Ch appearing on the right side of the expression (13) can be known in advance by a technique such as a design value or a prior measurement test. The energizing current i of the reaction motor 5 can be acquired from the current sensor 32, and the steering angle θh of the steering wheel 2 can be acquired from the steering angle sensor 4. Therefore, the approximate value of the torque sensor value τ can be obtained by using Expression (13).

  If the torque τ of the equation (13) obtained approximately is used in place of the actual torque sensor value τ in the equation (3), the inertia compensation current Iina for inertia correction is calculated. Since the actual measured value τ of the torque sensor and the value τ obtained by the equation (13) should be substantially equal, the inertia correction effect of the reaction force motor 5 system can be expected.

  Also in the second embodiment, since the inertia compensation current Iina is approximately calculated based on the energization current (actual current) i of the reaction force motor 5, a torque sensor for inertia compensation of the reaction force motor 5 becomes unnecessary. . As a result, the number of parts of the steering device 1 can be reduced, the system can be simplified, and the cost can be reduced. In addition, the simplification of the system improves the mountability of the steering device 1 on the vehicle.

[Other Examples]
The present invention is not limited to the embodiment described above.
For example, in the above-described embodiment, a steer-by-wire type steering device in which the steering wheel and the steered wheel are mechanically completely separated from each other is targeted, but by a connection / disconnection means such as a clutch, It is possible to select the connection state between the steering wheel and the steered wheel. Normally, the steering wheel and the steered wheel are mechanically separated from each other. If necessary, the steering wheel and steered wheel are mechanically separated. The present invention can also be applied to a steering device that is used in a connected manner.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the steering device of Example 1 which concerns on this invention. FIG. 3 is a block diagram of the steering apparatus according to the first embodiment. It is a block diagram of the steering apparatus of Example 2 which concerns on this invention.

Explanation of symbols

1 Steering device 2 Steering wheel (operator)
5 reaction force motor 10 wheels (steering wheels)
11 Steering motor 21 Reaction force motor control part (Reaction force motor control means)

Claims (1)

An operator operated by the driver;
A steered wheel that is mechanically separated from the operating element or that can be connected from a mechanically separated state;
A steering motor that steers the steered wheel;
A reaction force motor coupled to the operation element to apply a reaction force to the operation element;
Steered motor control means for controlling the steered motor in response to an operation input to the operator;
Reaction force motor control means for controlling the reaction force motor;
With
The reaction force motor control means performs inertia compensation based on a current flowing through the reaction force motor, and performs feedback control so that the current flowing through the reaction force motor matches a target current of the reaction force motor,
The target current of the reaction force motor is calculated by adding a virtual torsion bar current, a damping current and an inertia compensation current,
The virtual torsion bar current is calculated based on an angular deviation between a steering angle of the operating element and a turning angle of the steered wheel.

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