JP2016084003A - Vehicle steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicle steering device which can suppress that a vehicle becomes instable at abrupt steering.SOLUTION: A target turning angle setting part 81 sets a target turning angle θton the basis of a turning angle θh which is calculated by a rotation angle calculation part in a reaction control part. An LPF 82 performs low-pass filter processing for attenuating a high-frequency component to the target turning angle θt. An angle deviation calculation part 83 calculates deviation between the target turning angle θtafter the low-pass filter processing by the LPF 82 and a turning angle θt which is detected by a turning angle sensor 48. A PI control part 84 performs PI calculation with respect to the angle deviation which is calculated by the angle deviation calculation part 83.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a vehicle steering apparatus in which a steering member operated for steering is not mechanically coupled to a steering mechanism, and the steering mechanism is driven by a steering motor.

The steering wheel as a steering member is not mechanically coupled to the steering mechanism, the steering wheel operating angle is detected by a rotation angle sensor, and the driving force of the steering motor controlled according to the sensor output is controlled by the steering mechanism. There has been proposed a steer-by-wire system that is adapted to transmit to the network.
In a cargo handling vehicle such as a forklift that employs a steer-by-wire system, the range of rotation amount of the steering wheel is larger than that of a general vehicle. For example, in a cargo handling vehicle, the steering wheel may be rotated one or more times when turning. For this reason, in a cargo handling vehicle, the burden of the driver | operator at the time of vehicle turning is large. Therefore, a cargo handling vehicle using a joystick or a lever as a steering member has been proposed (see Patent Documents 1 and 2).

Japanese Patent Laid-Open No. 10-252100 JP 2005-143887 A

  When a joystick or a lever is used as a steering member, the steering stroke is shorter than when a steering wheel is used as an operation member. For example, in a cargo handling vehicle, the steering stroke of the steering wheel is about ± 810 [deg] from the neutral position (here, the rotation angle is regarded as the stroke), but the steering stroke of the joystick or lever is from the neutral position. It is about ± 45 [deg] to ± 90 [deg]. Therefore, when a joystick or a lever is used as a steering member, the operation sensitivity becomes high, so that the vehicle may become unstable when the steering member is suddenly steered. Even when the steering wheel is used as the steering member, the same problem occurs when the steering stroke is set short.

  An object of the present invention is to provide a vehicle steering apparatus that can prevent the vehicle from becoming unstable during sudden steering.

  In order to achieve the above object, the invention according to claim 1 is directed to a steering mechanism (40) for changing the steering angle of the steering members (36, 23) and the steered wheels (5) operated for steering. ) Is a vehicle steering device (6) in which the steering mechanism is driven by the steering motor (41), and a rotation angle detecting means (6) for detecting the rotation angle of the steering member. 34), target turning angle setting means (81) for setting a target turning angle based on the rotation angle detected by the rotation angle detection means, and target turning calculated by the target turning angle setting means. A low-pass filter (82) that performs low-pass filter processing on the steering angle, and steering control means (83, 84) that controls the steering motor based on the target turning angle after the low-pass filter processing by the low-pass filter. For vehicles including A rudder equipment. In addition, although the alphanumeric characters in parentheses represent corresponding components in the embodiments described later, of course, the scope of the present invention is not limited to the embodiments. The same applies hereinafter.

  In this configuration, the target turning angle is set by the target turning angle setting means. A low-pass filter process is performed on the target turning angle by the low-pass filter. The steered motor is controlled based on the target steered angle after the low pass filter process by the low pass filter. Since the high-frequency component of the target turning angle is removed by the low-pass filter process, sudden fluctuations in the target turning angle during sudden steering are suppressed. As a result, it is possible to prevent the vehicle from becoming unstable during sudden steering.

The invention according to claim 2 is a vehicle speed detecting means (15) for detecting a vehicle speed, and a cutoff for controlling the cutoff frequency (fc) of the low-pass filter based on the vehicle speed detected by the vehicle speed detecting means. The vehicle steering apparatus according to claim 1, further comprising frequency control means (92).
In this configuration, since the cutoff frequency of the low-pass filter is controlled based on the vehicle speed, it is possible to effectively prevent the vehicle from becoming unstable during sudden steering.

  The invention described in claim 3 is a cargo handling device (3) provided on the vehicle body (2), a load detection means (14) for detecting a loading load which is a weight of a load loaded on the cargo handling device, The vehicle steering apparatus according to claim 1, further comprising a cutoff frequency control means (92) for controlling a cutoff frequency (fc) of the low-pass filter based on a loaded load detected by the load detection means. It is.

In this configuration, since the cut-off frequency of the low-pass filter is controlled based on the loaded load, it is possible to effectively suppress the vehicle from becoming unstable during sudden steering.
The invention described in claim 4 is a cargo handling device (3) provided on the vehicle body (2), a load detection means (14) for detecting a loaded load which is the weight of the cargo loaded on the cargo handling device, Based on the vehicle speed detection means (15) for detecting the vehicle speed, the vehicle speed detected by the vehicle speed detection means and the loaded load detected by the load detection means, the cut-off frequency (fc) of the low-pass filter is determined. The vehicle steering apparatus according to claim 1, further comprising a cutoff frequency control means for controlling.

In this configuration, since the cut-off frequency of the low-pass filter is controlled based on the loaded load and the vehicle speed, it is possible to effectively suppress the vehicle from becoming unstable during sudden steering.
The invention according to claim 5 is configured such that the cutoff frequency control means controls the cutoff frequency of the low-pass filter in consideration of forward or reverse. 4. The vehicle steering device according to claim 4.

In this configuration, since the cut-off frequency of the low-pass filter is controlled in consideration of whether the vehicle is moving forward or backward, it is possible to more effectively suppress the vehicle from becoming unstable during sudden steering.
A sixth aspect of the present invention is the vehicle steering apparatus according to any one of the first to fifth aspects, wherein the steering member is a steering lever disposed on a side of the driver's seat.

FIG. 1 is a side view schematically showing a schematic configuration of a forklift as a cargo handling vehicle to which a vehicle steering apparatus according to an embodiment of the present invention is applied. FIG. 2 is an enlarged plan view showing the driver's seat and its peripheral part. FIG. 3 is an enlarged side view showing the driver's seat and the periphery thereof. FIG. 4 is an illustrative view for explaining the configuration of the vehicle steering apparatus. FIG. 5 is a block diagram showing an electrical configuration of the ECU. FIG. 6 is a block diagram illustrating a configuration of the reaction force control unit. FIG. 7 is an illustrative view showing a configuration of a reaction force motor. FIG. 8 is a graph showing a setting example of the target reaction force torque T ^* with respect to the steering angle θh. FIG. 9 is a block diagram illustrating a configuration of the steering control unit. FIG. 10 is a graph showing an example of setting the target turning angle θt ^{* with} respect to the steering angle θh. FIG. 11 is a flowchart showing the operation of the cutoff frequency setting unit. FIG. 12 is a plan view showing a modification of the steering member. FIG. 13 is a side view showing the steering member of FIG. FIG. 14 is a partially cutaway enlarged cross-sectional view showing the steering member support structure of FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a side view schematically showing a schematic configuration of a forklift as a cargo handling vehicle to which a vehicle steering apparatus according to an embodiment of the present invention is applied.
The forklift 1 includes a vehicle body 2, a cargo handling device 3 provided at the front of the vehicle body 2, a front wheel 4 as a drive wheel that supports the vehicle body 2, a rear wheel 5 as a steered wheel that supports the vehicle body 2, The vehicle steering device 6 for turning the wheel 5 is included. The forklift 1 includes a driver's cab 8 including a driver's seat 7 provided in the upper part of the vehicle body 2. The upper part of the cab 8 is covered with a head guard 9.

  Although not shown in FIG. 1, the forklift 1 further includes, for example, a vehicle drive source including an engine and a hydraulic pump as a hydraulic source. The power of the drive source is transmitted to a transmission that performs forward / reverse switching and shift operation through a torque converter, and further transmitted to left and right front wheels (drive wheels) 4 through a differential. The transmission includes a forward clutch and a reverse clutch. The forward clutch and the reverse clutch are connected to a shift lever (not shown). Forward / backward switching can be performed by operating the shift lever. An accelerator pedal (not shown) for adjusting the power supplied to the driving source is provided on the floor of the cab 8.

The shift lever is provided with a shift lever sensor 16 (see FIG. 4) for detecting the shift position of the shift lever. The shift lever sensor 16 outputs a signal Si indicating the shift position (forward, reverse).
As is well known, the cargo handling device 3 includes a fork (baggage placing portion) 11 supported so as to be able to move up and down and tiltable with respect to the vehicle body 2, a lifting cylinder 12 for lifting and lowering the fork 11, A tilt cylinder 13 for tilting the fork 11 is included. The cargo handling device 3 is provided with a load sensor 14 for measuring a load weight We that is the weight of the cargo loaded on the cargo handling device 3.

FIG. 2 is an enlarged plan view showing the driver's seat and its peripheral part. FIG. 3 is an enlarged side view showing the driver's seat and the periphery thereof.
The driver seat 7 includes a driver seat 21 and a backrest 22. On one side of the driver seat 7 (left side in this embodiment), a steering lever 36 is disposed as a steering member that is operated for steering. Specifically, the motor attachment member 26 is attached to the vehicle body 2 on the left side of the front end portion of the driver seat 21. A reaction force motor 28 is attached upward to the motor attachment member 26. The base end of the steering lever 36 is fixed to the output shaft 28 a of the reaction force motor 28. The steering lever 36 is supported by the reaction force motor 28 so as to be rotatable in the left-right direction with the posture in which the tip extends forward as a neutral position. In this embodiment, the reaction force motor 28 is a three-phase brushless motor. The reaction force motor 28 is provided to apply a reaction force torque (operation reaction force) to the steering lever 36. The reaction motor 28 incorporates a rotation angle sensor 34 (see FIG. 4) for detecting the rotation angle of the output shaft 28a (rotor).

The vehicle steering device 6 is a so-called steering / steering mechanism in which the mechanical connection between the steering lever 36 as a steering member and the steering mechanism for changing the steering angle of the rear wheel 5 as a steered wheel is broken. It is a by-wire system.
FIG. 4 is an illustrative view for explaining the configuration of the vehicle steering apparatus.
In this vehicle steering device 6, the rotational motion of the rotor of the steering motor 41 driven in accordance with the rotational operation of the steering lever 36 is converted into a linear motion of the steering shaft 44 (linear motion in the vehicle left-right direction), Steering is achieved by converting the linear motion of the steered shaft 44 into the steered motion of the rear wheel 5.

  The steered shaft 44 is attached to a housing 43 attached to the vehicle body 2 so as to be movable in the axial direction (left-right direction of the vehicle body). In this embodiment, the steered motor 41 is disposed coaxially with the steered shaft 44 and is built in the housing 43. In this embodiment, the steering motor 41 is constituted by a three-phase brushless motor. The turning motor 41 is provided with a rotation angle sensor 47 for detecting the rotation angle of the rotor of the turning motor 41.

  In the housing 43, a motion conversion mechanism 42 for converting the rotational force of the steering motor 41 into a linear motion in the axial direction of the steering shaft 44 is provided. The motion conversion mechanism 42 is, for example, a ball screw mechanism. The movement of the turning shaft 44 is transmitted to the rear wheel 5 via the tie rod 45 and the knuckle arm 46, and the toe angle (steering angle) of the rear wheel 5 changes. That is, the steering mechanism 40 is configured by the steering motor 41, the motion conversion mechanism 42, the steering shaft 44, the tie rod 45, and the knuckle arm 46.

  In this embodiment, when the steered motor 41 is rotated in the forward direction, the steered angle of the rear wheel 5 changes in the direction in which the vehicle is steered in the left direction (left steered direction). When the wheel is rotated in the reverse direction, the turning angle of the rear wheel 5 changes in the direction in which the vehicle is steered to the right (right turning direction). In the state where the steering motor 41 is not driven, the wheel alignment is set so that the rear wheel 5 can be returned to the straight steering position by the self-alignment torque.

  A steering angle sensor 48 for detecting the steering angle of the vehicle (the steering angle of the rear wheels 5) θt is attached to the housing 43. The turning angle sensor 48 is constituted by, for example, a potentiometer that detects an operation amount of the turning shaft 44 corresponding to the turning angle θt. In this embodiment, the turning angle sensor 48 detects the amount of change in the turning angle of the rear wheel 5 from the neutral position (straight forward turning position) of the rear wheel 5 as the turning angle θt. In this embodiment, the turning angle sensor 48 outputs a turning angle change amount from the neutral position of the rear wheel 5 to the left turning direction, for example, as a positive value, and the right turning direction from the neutral position of the rear wheel 5. The turning angle change amount to is output as, for example, a negative value.

  The load sensor 14, the shift lever sensor 16, the rotation angle sensor 34, the rotation angle sensor 47, and the turning angle sensor 48 are connected to the ECU 50. The ECU 50 is further connected with a vehicle speed sensor 15 for detecting the vehicle speed. The ECU 50 drives and controls the reaction force motor 28 based on the output signal of the rotation angle sensor 34. Further, the ECU 50 controls the turning motor 41 based on the output signals of the rotation angle sensor 34, the shift lever sensor 16, the load sensor 14, the vehicle speed sensor 15, the shift lever sensor 16, the rotation angle sensor 47, and the turning angle sensor 48. Drive control.

FIG. 5 is a block diagram showing an electrical configuration of the ECU 50.
The ECU 50 supplies power to the control unit 51, a reaction force motor drive circuit 52 that supplies power to the reaction force motor 28, a current detection unit 53 that detects a motor current flowing in the reaction force motor 28, and the turning motor 41. A steering motor drive circuit 54 to be supplied and a current detection unit 55 that detects a motor current flowing in the steering motor 41 are included. The control unit 51 includes a reaction force control unit 61 for controlling an operation reaction force (reaction torque) generated by the reaction force motor 28 and a turning angle for controlling the rotation angle (steering angle) of the turning motor 41. Rudder control unit 62.

FIG. 6 is a block diagram illustrating a configuration of the reaction force control unit 61.
In this embodiment, the reaction force motor 28 is a three-phase brushless motor, and as shown schematically in FIG. 7, the rotor 32 as a field and stator windings 33U of U phase, V phase and W phase, And a stator 33 including 33V and 33W. Three-phase fixed coordinates (UVW coordinate system) are defined with the U, V, and W axes in the direction of the stator windings 33U, 33V, and 33W of each phase. Also, a two-phase rotational coordinate system (dq coordinate system) in which the d axis (magnetic pole axis) is taken in the magnetic pole direction of the rotor 32 and the q axis (torque axis) is taken in the direction perpendicular to the d axis in the rotation plane of the rotor 32. The actual rotating coordinate system) is defined. In the dq coordinate system, since only the q-axis current contributes to the torque generation of the rotor 32, the d-axis current may be set to zero and the q-axis current may be controlled according to the desired torque. A rotation angle (rotor angle (electrical angle)) θe of the rotor 32 is a rotation angle of the d-axis with respect to the U-axis. The dq coordinate system is an actual rotating coordinate system according to the rotor angle θe. By using this rotor angle θe, coordinate conversion between the UVW coordinate system and the dq coordinate system can be performed.

Referring to FIG. 6, reaction force control unit 61 includes target reaction force torque setting unit 71, current command value generation unit 72, current deviation calculation unit 73, PI (proportional integration) control unit 74, dq / A UVW converter 75, a PWM (Pulse Width Modulation) controller 76, a UVW / dq converter 77, and a rotation angle calculator 78 are included.
The rotation angle calculation unit 78 calculates the rotation angle of the rotor of the reaction force motor 28 based on the output signal of the rotation angle sensor 34. More specifically, the rotation angle calculator 78 calculates a rotor angle θe that is an electrical angle of the rotor and a steering angle θh that is an absolute rotation angle of the rotor. The steering angle θh is the amount of rotation (rotation angle) in both the forward and reverse directions of the rotor from a predetermined reference position (neutral position) of the rotor (output shaft 28a) of the reaction force motor 28. The rotation angle calculator 78 calculates the rotation amount from the neutral position to the left steering direction as a positive steering angle θh, for example, and calculates the rotation amount from the neutral position to the right steering direction, for example, a negative steering angle θh. Calculate as The rotation angle range of the rotor of the reaction force motor 28 is defined within a range of ± α [deg] from the neutral position by a stopper (not shown). For example, α is set to a value within the range of 45 [deg] to 90 [deg]. In this embodiment, α is set to 60 [deg].

The target reaction force torque setting unit 71 sets the target reaction force torque T ^* based on the steering angle θh calculated by the rotation angle calculation unit 78. An example of setting the target reaction force torque T ^* with respect to the steering angle θh is shown in FIG. The target reaction force torque T ^* is a positive value when a reaction force to the left steering is to be generated from the reaction motor 28, and is a negative value when a reaction force to the right steering is to be generated from the reaction motor 28. Is done. The target reaction force torque T ^* takes a positive value for a positive value of the steering angle θh, and takes a negative value for a negative value of the steering angle θh.

When the steering angle θh is in the range of θh1 (θh1> 0) [deg] to 60 [deg], the target reaction force torque T ^* is set to a predetermined value T1 ^* (T1 ^* > 0). When the steering angle θh is in the range of −60 [deg] to −θh1 [deg], the target reaction force torque T ^* is set to −T1 ^* . When the steering angle θh is in the range of −θh1 [deg] to θh1 [deg], the target reaction force torque T ^* is set to increase from −T1 ^* to T1 ^{* as} the steering angle θh increases.

In addition, when the stopper for prescribing the rotation angle range of the rotor (output shaft 28a) of the reaction force motor 28 is not provided, the absolute value of the steering angle θh should not be larger than 60 [deg]. The target reaction force torque T ^* may be set as follows. That is, when the steering angle θh is 60 [deg] or more, the target reaction force torque T ^* is set to an upper limit value larger than T1 ^* , and when the steering angle θh is 60 [deg] or less, the target The reaction force torque T ^* is set to a lower limit value smaller than -T1 ^* .

Based on the target reaction force torque T ^* set by the target reaction force torque setting unit 71, the current command value generation unit 72 generates a current value to be passed through the coordinate axes of the dq coordinate system as a current command value. Specifically, the current command value generation unit 72 is referred to as a d-axis current command value i _d ^* and a q-axis current command value i _q ^* (hereinafter collectively referred to as “two-phase current command value i _dq ^* ”). ) Is generated. More specifically, the current command value generation unit 72 sets the q-axis current command value i _q ^* as a motor current value corresponding to the target reaction force torque T ^* set by the target reaction force torque setting unit 71. The d-axis current command value i _d ^{* is set} to zero. The two-phase current command value i _dq ^* generated by the current command value generation unit 72 is given to the current deviation calculation unit 73.

The current detection unit 53 uses the U-phase current i _U , the V-phase current i _V and the W-phase current i _W of the reaction force motor 28 (hereinafter, collectively referred to as “three-phase detection current i _UVW ”). To detect. The three-phase detection current i _UVW detected by the current detection unit 53 is given to the UVW / dq conversion unit 77.
The UVW / dq conversion unit 77 converts the three-phase detection current i _UVW in the UVW coordinate system detected by the current detection unit 53 into the two-phase detection currents i _d and i _q (hereinafter referred to as “two-phase detection” in the dq coordinate system). Current i _dq "). These are given to the current deviation calculation unit 73. For the coordinate conversion in the UVW / dq conversion unit 77, the rotor angle θe calculated by the rotation angle calculation unit 78 is used.

The current deviation calculation unit 73 calculates a deviation between the two-phase current command value i _dq ^* generated by the current command value generation unit 72 and the two-phase detection current i _dq given from the UVW / dq conversion unit 77. More specifically, the current deviation calculation unit 73 calculates the deviation of the d-axis detection current i _d with respect to the d-axis current command value i _d ^* and the deviation of the q-axis detection current i _q with respect to the q-axis current command value i _q ^* . To do. These deviations are given to the PI control unit 74.

The PI control unit 74 performs a PI calculation on the current deviation calculated by the current deviation calculation unit 73, thereby performing a two-phase voltage command value v _dq ^* (d-axis voltage command value v _d ^*) to be applied to the reaction force motor 28 ^. And q-axis voltage command value v _q ^* ). The two-phase voltage command value v _dq ^* is given to the dq / UVW converter 75.
The dq / UVW conversion unit 75 converts the two-phase voltage command value v _dq ^* into a three-phase voltage command value v _UVW ^* . For this coordinate conversion, the rotor angle θe calculated by the rotation angle calculation unit 78 is used. The three-phase voltage command value v _UVW ^* includes a U-phase voltage command value v _U ^* , a V-phase voltage command value v _V ^*, and a W-phase voltage command value v _W ^* . The three-phase voltage command value v _UVW ^* is given to the PWM control unit 76.

The PWM control unit 76 includes a U-phase PWM control signal, a V-phase PWM control signal having a duty corresponding to the U-phase voltage command value v _U ^* , the V-phase voltage command value v _V ^*, and the W-phase voltage command value v _W ^* , respectively. A W-phase PWM control signal is generated and supplied to the reaction force motor drive circuit 52.
The reaction force motor drive circuit 52 includes a three-phase inverter circuit corresponding to the U phase, the V phase, and the W phase. The power elements constituting the inverter circuit are controlled by a PWM control signal supplied from the PWM control unit 76, so that a voltage corresponding to the three-phase voltage command value v _UVW ^* is applied to each phase of the stator winding of the reaction force motor 28. Applied to 33U, 33V, 33W.

The current deviation calculation unit 73 and the PI control unit 74 constitute a current feedback control unit. By the action of the current feedback control means, the motor current flowing through the reaction force motor 28 is controlled so as to approach the two-phase current command value i _dq ^* generated by the current command value generation unit 72. Thereby, a reaction force torque corresponding to the target reaction force torque T ^* is generated from the reaction force motor 28.

FIG. 9 is a block diagram illustrating a configuration of the steering control unit 62.
In this embodiment, the steered motor 41 is a three-phase brushless motor, similar to the reaction force motor 28. Although not shown, the steered motor 41 includes a rotor as a field and a stator including U-phase, V-phase, and W-phase stator windings.
The turning control unit 62 includes a target turning angle calculation unit 81, a low-pass filter (LPF) 82, an angle deviation calculation unit 83, a PI (proportional integration) control unit 84, a current command value generation unit 85, a current Deviation calculation unit 86, PI (proportional integration) control unit 87, dq / UVW conversion unit 88, PWM control unit 89, UVW / dq conversion unit 90, rotation angle calculation unit 91, and cutoff frequency setting unit 92.

The rotation angle calculation unit 91 calculates the rotor angle φe, which is the electrical angle of the rotor of the steered motor 41, based on the output signal of the rotation angle sensor 47.
The target turning angle setting unit 81 sets the target turning angle θt ^* based on the steering angle θh calculated by the rotation angle calculation unit 78 in the reaction force control unit 61. An example of setting the target turning angle θt ^{* with} respect to the steering angle θh is shown by a solid line L1 in FIG. The target turning angle θt ^* takes a positive value when the steering angle θh is a positive value, and takes a negative value when the steering angle θh is a negative value. The target turning angle θt ^* is set such that the absolute value of the steering angle θt ^* increases as the absolute value of the steering angle θh increases. However, when the absolute value of the steering angle θh is equal to or smaller than the predetermined value θh2 (θh2> 0), the target turning angle θt ^{* with} respect to the steering angle θh is compared to when the absolute value of the steering angle θh is larger than the predetermined value θh2 ^. The rate of change is small. As shown by a two-dot chain line L2 in FIG. 11, the target turning angle θt ^* is set according to the characteristic that the rate of change of the target turning angle θt ^{* with} respect to the steering angle θh is constant over the entire range of the steering angle θh. May be. The target turning angle θt ^* set by the target turning angle setting unit 81 is given to the LPF 82.

The LPF 82 performs a low pass filter process for attenuating a high frequency component with respect to the target turning angle θt ^* . Thus, the target steered angle [theta] t ^* short period of time greater varying component in the (high-frequency component of the target steered angle [theta] t ^*) is removed, a sudden change of the target steered angle [theta] t ^* is suppressed. The smaller the cut-off frequency fc of the LPF 82, the higher the fluctuation suppressing effect.
The cutoff frequency fc of the LPF 82 is set by the cutoff frequency setting unit 92. The cutoff frequency setting unit 92 is based on the vehicle speed Sp detected by the vehicle speed sensor 15, the loaded load We detected by the load sensor 14, and the shift position Si detected by the shift lever sensor 16, and the cutoff frequency fc of the LPF 82. Set.

  The greater the vehicle speed Sp, the more likely the vehicle becomes unstable during sudden steering. Therefore, the cut-off frequency setting unit 92 sets the cut-off frequency fc so that the cut-off frequency fc decreases as the vehicle speed Sp increases. Further, the larger the loading weight Sp, the more likely the vehicle becomes unstable during sudden steering. Therefore, the cut-off frequency setting unit 92 sets the cut-off frequency fc so that the cut-off frequency fc decreases as the loading weight Sp increases.

  In this embodiment, since the rear wheel 5 is a steered wheel, the vehicle is more likely to become unstable during forward rapid steering than during backward rapid steering. Therefore, in this embodiment, the cut-off frequency setting unit 92 sets the cut-off frequency fc so that the cut-off frequency fc at the time of forward movement becomes smaller than that at the time of reverse movement. Details of the operation of the cut-off frequency setting unit 92 will be described later.

The angle deviation calculation unit 83 calculates a deviation between the target turning angle θt ^* after the low pass filter processing by the LPF 82 and the turning angle θt detected by the turning angle sensor 48. The PI control unit 84 performs PI calculation for the angle deviation calculated by the angle deviation calculation unit 83.
Based on the calculation result of the PI control unit 84, the current command value generation unit 85 generates a current value to be passed through the coordinate axes of the dq coordinate system as a current command value. Specifically, the current command value generation unit 85 refers to a d-axis current command value I _d ^* and a q-axis current command value I _q ^* (hereinafter referred to as “two-phase current command value I _dq ^* ”). ) Is generated. More specifically, current command value generation unit 85 generates q-axis current command value I _q ^* based on the calculation result of PI control unit 84, while setting d-axis current command value I _d ^* to zero. . The two-phase current command value I _dq ^* generated by the current command value generation unit 85 is given to the current deviation calculation unit 86.

The current detection unit 55 uses the U-phase current I _U , the V-phase current I _V, and the W-phase current I _W (hereinafter collectively referred to as “three-phase detection current I _UVW ”) of the steering motor 41. To detect. The three-phase detection current I _UVW detected by the current detection unit 55 is given to the UVW / dq conversion unit 90.
The UVW / dq conversion unit 90 converts the three-phase detection current I _UVW (U-phase current I _U , V-phase current I _V and W-phase current I _W ) in the UVW coordinate system detected by the current detection unit 55 into the dq coordinate system. _Are converted into two-phase detection currents I _d and I _q (hereinafter collectively referred to as “two-phase detection current I _dq ”). These are given to the current deviation calculator 86. For the coordinate conversion in the UVW / dq converter 90, the rotor angle φe calculated by the rotation angle calculator 91 is used.

The current deviation calculation unit 86 calculates the deviation between the two-phase current command value I _dq ^* generated by the current command value generation unit 85 and the two-phase detection current I _dq given from the UVW / dq conversion unit 90. More specifically, the current deviation calculation unit 86 calculates the deviation of the d-axis detection current I _d with respect to the d-axis current command value I _d ^* and the deviation of the q-axis detection current I _q with respect to the q-axis current command value I _q ^* . To do. These deviations are given to the PI control unit 87.

The PI control unit 87 performs a PI calculation on the current deviation calculated by the current deviation calculation unit 86, thereby performing a two-phase voltage command value V _dq ^* (d-axis voltage command value V _d ^*) to be applied to the steered motor 41 ^. And q-axis voltage command value V _q ^* ). The two-phase voltage command value V _dq ^* is given to the dq / UVW converter 88.
The dq / UVW conversion unit 88 converts the two-phase voltage command value V _dq ^* into a three-phase voltage command value V _UVW ^* . For this coordinate conversion, the rotor angle φe calculated by the rotation angle calculation unit 91 is used. The three-phase voltage command value V _UVW ^* includes a U-phase voltage command value V _U ^* , a V-phase voltage command value V _V ^*, and a W-phase voltage command value V _W ^* . The three-phase voltage command value V _UVW ^* is given to the PWM control unit 89.

The PWM control unit 89 includes a U-phase PWM command signal, a V-phase PWM control signal having a duty corresponding to the U-phase voltage command value V _U ^* , the V-phase voltage command value V _V ^*, and the W-phase voltage command value V _W ^* , respectively. A W-phase PWM control signal is generated and supplied to the steered motor drive circuit 54.
The steered motor drive circuit 54 includes a three-phase inverter circuit corresponding to the U phase, the V phase, and the W phase. The power elements constituting the inverter circuit are controlled by a PWM control signal supplied from the PWM control unit 89, so that a voltage corresponding to the three-phase voltage command value V _UVW ^* is applied to the stator windings of each phase of the steered motor 41. To be applied.

The angle deviation calculation unit 83 and the PI control unit 84 constitute angle feedback control means. By the operation of this angle feedback control means, the turning angle θt of the rear wheel 5 is controlled so as to approach the target turning angle θt ^* after the low pass filter processing by the LPF 82. Further, the current deviation calculation unit 86 and the PI control unit 87 constitute a current feedback control unit. By the function of the current feedback control means, the motor current flowing through the steered motor 41 is controlled so as to approach the two-phase current command value I _dq ^* generated by the current command value generation unit 85.

FIG. 11 is a flowchart showing the operation of the cut-off frequency setting unit 92. The process of FIG. 11 is repeatedly executed at every predetermined calculation cycle.
The cut-off frequency setting unit 92 acquires the vehicle speed Sp [km / h] detected by the vehicle speed sensor 15 and the loaded load We [t] detected by the load sensor 14 (step S1). Next, the cut-off frequency setting unit 92 calculates the first gain G1 and the second gain G2 based on the following equations (1) and (2), respectively (step S2).

G1 = A1-A2 * Sp (1)
G2 = B1-B2 * We (2)
In the formula (1), A1 and A2 are constants. In this embodiment, A1 is set to 3, for example, and A2 is set to 0.05, for example. In the formula (2), B1 and B2 are constants. In this embodiment, B1 is set to 1, for example, and B2 is set to 0.01, for example. Therefore, in this embodiment, the first gain G1 and the second gain G2 are expressed by the following equations (3) and (4), respectively.

G1 = 3-0.05 * Sp (3)
G2 = 1-0.01 * We (4)
Next, the cutoff frequency setting unit 92 determines whether or not the shift position is the forward position based on the shift position Si detected by the shift lever sensor 16 (step S3). When the shift position is the forward position (step S3: YES), the cutoff frequency setting unit 92 sets the third gain G3 to 1.0 (step S4). Then, the cutoff frequency setting unit 92 proceeds to step S6.

On the other hand, when it is determined in step S3 that the shift position is not the forward position (step S3: NO), the cutoff frequency setting unit 92 sets the third gain G3 to 1.1 (step S5). ). Then, the cutoff frequency setting unit 92 proceeds to step S6.
In step S6, the cut-off frequency setting unit 92 calculates the cut-off frequency fc based on the following equation (5) and sets it in the LPF 82. Then, the cutoff frequency setting unit 92 ends the processing in the current calculation cycle.

fc = G1 * G2 * G3 (5)
However, when fc is equal to or lower than a predetermined lower limit value β, fc is set to the lower limit value β. For example, the lower limit value β is set to 1.4 [Hz].
In the above-described embodiment, the LPF 82 performs the low-pass filter process for attenuating the high frequency component with respect to the target turning angle θt ^* . Then, the turning motor 41 is controlled so that the turning angle θt detected by the turning angle sensor 48 becomes equal to the target turning angle θt ^* after the low-pass filter process. The LPF 82, since the target steered angle [theta] t ^* of the high-frequency component (component varying greatly in a short period of time) is removed, a sudden change of the target steered angle [theta] t ^* is suppressed at the time of sudden steering. As a result, it is possible to prevent the vehicle from becoming unstable during sudden steering.

  In the above-described embodiment, the cut-off frequency fc of the LPF 82 is decreased as the vehicle speed Sp is increased. As a result, it is possible to effectively prevent the vehicle from becoming unstable even during sudden steering with a high vehicle speed Sp. In the above-described embodiment, the cutoff frequency fc of the LPF 82 is decreased as the loaded load We increases. As a result, it is possible to effectively prevent the vehicle from becoming unstable even during sudden steering in a state where the loaded load We is large.

  In the above-described embodiment, since the rear wheel 5 is a steered wheel, the vehicle is more likely to become unstable during forward sudden steering than during backward rapid steering. In the above-described embodiment, the cutoff frequency setting unit 92 sets the cutoff frequency fc so that the cutoff frequency fc at the time of forward movement becomes smaller than that at the time of backward movement. It is possible to effectively suppress the vehicle from becoming unstable.

  As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form. For example, in the above-described embodiment, the cutoff frequency setting unit 92 is based on the vehicle speed Sp detected by the vehicle speed sensor 15, the loaded load We detected by the load sensor 14, and the shift position Si detected by the shift lever sensor 16. The cut-off frequency fc of the LPF 82 is set.

  However, the cutoff frequency setting unit 92 may set the cutoff frequency fc of the LPF 82 based on the vehicle speed Sp detected by the vehicle speed sensor 15 and the loaded load We detected by the load sensor 14. Further, the cutoff frequency setting unit 92 may set the cutoff frequency fc of the LPF 82 based only on the vehicle speed Sp detected by the vehicle speed sensor 15. Further, the cut-off frequency setting unit 92 may set the cut-off frequency fc of the LPF 82 based only on the loaded load We detected by the load sensor 14.

In the above-described embodiment, the steering lever 36 is used as the steering member. However, a joystick, a steering wheel, or the like may be used as the steering member.
Moreover, as shown in FIGS. 12-14, you may use the armrest arrange | positioned at the side of a driver's seat as a steering member. Referring to FIGS. 12 and 13, armrests 23 and 24 are arranged on both sides of driver's seat 7. The armrests 23 and 24 extend substantially in the front-rear direction in a plan view, and are bent so that the central portion of the length projects outward. The right armrest 24 is fixed to the vehicle body 2.

  The left armrest 23 is attached to the vehicle body 2 so as to be rotatable about the rear end portion in plan view. A knob 25 for operating the movable armrest 23 is attached to the upper surface of the front end portion of the left armrest (hereinafter referred to as “movable armrest 23”). In addition to the function as an armrest, the movable armrest 23 also has a function as a steering member that is operated for steering.

  With reference to FIGS. 12 to 14, a motor attachment member 26 is attached to the vehicle body 2 at the left position of the backrest 22. The motor mounting member 26 has a cylindrical shape extending in the vertical direction and having flanges at both ends. A lower flange of the motor mounting member 26 is fixed to the vehicle body 2 by a plurality of bolts 27. A reaction force motor 28 is attached upward to the motor attachment member 26. The reaction force motor 28 is fixed to the upper flange of the motor mounting member 26 by a plurality of bolts 29. In this embodiment, the reaction force motor 28 is a three-phase brushless motor.

  The reaction force motor 28 includes a case 30, a rotor 32 that is rotatably supported by the case 30 and disposed in the case 30, and a stator disposed around the rotor 32 in the case 30. 33. The upper end portion of the rotation shaft 31 extends through the case 30 and above the case 30. A flange 31 a is formed at the upper end of the rotating shaft 31. A serrated groove (serration (not shown)) is formed on the outer peripheral surface of the flange 31a. In the case 30, a rotation angle sensor 34 for detecting the rotation angle of the rotation shaft 31 (rotor 32) is disposed around the rotation shaft 31.

  On the lower surface of the rear end portion of the movable armrest 23, a flange insertion recess 23a that fits with the flange 31a is formed. A serration (not shown) that fits with the serration of the outer peripheral surface of the flange 31a is formed on the inner peripheral surface of the flange insertion recess 23a. A plurality of bolt head accommodation recesses 23 b are formed on the surface (upper surface) of the upper wall of the flange insertion recess 23 a of the movable armrest 23. The rear end portion of the movable armrest 23 is fixed to the flange 31a by a plurality of bolts 35 in a state where the flange insertion recess 23a is fitted to the flange 31a. The plurality of bolts 35 are screwed into the flange 31a through the wall between the bolt head receiving recess 23b and the flange insertion recess 23a in the movable armrest 23.

  That is, the rear end portion of the movable armrest 23 is rotatably supported on the vehicle body 2 via the reaction force motor 28. The reaction force motor 28 is provided to apply a reaction force torque (operation reaction force) to the movable armrest 23. The position of the movable armrest 23 indicated by a solid line in FIG. 12 is a neutral position, and the position of the movable armrest 23 indicated by a one-dot chain line in FIG. 12 is an operation limit position for left steering.

  In the above-described embodiment, the turning angle sensor 48 for detecting the turning angle θt is provided separately from the rotation angle sensor 47 for detecting the rotation angle of the rotor of the turning motor 41. However, the turning angle θt may be calculated based on the output of the rotation angle sensor 47 for detecting the rotation angle of the rotor of the turning motor 41. That is, based on the output of the rotation angle sensor 47, the absolute rotation angle representing the amount of rotation from the neutral position of the rotor of the steering motor 41 is calculated, and the turning angle θt of the steered wheels 5 is calculated from the obtained absolute rotation angle. You may make it calculate. In this case, the turning angle sensor 48 is unnecessary.

  In addition, various design changes can be made within the scope of matters described in the claims.

  DESCRIPTION OF SYMBOLS 1 ... Forklift, 2 ... Vehicle body, 5 ... Rear wheel (steered wheel), 6 ... Vehicle steering device, 7 ... Driving seat, 14 ... Load sensor, 15 ... Vehicle speed sensor, 16 ... Shift lever sensor, 23 ... Movable armrest, 36 ... steering lever, 40 ... steering mechanism, 41 ... steering motor, 47 ... rotation angle sensor, 48 ... steering angle sensor, 50 ... ECU, 51 ... control unit, reaction force control unit, 62 ... steering control unit , 81 ... Target turning angle setting section, 82 ... Low pass filter, 83 ... Angular deviation calculation section, 84 ... PI control section, 92 ... Cutoff frequency setting section

Claims (6)

A steering apparatus for a vehicle in which a steering member operated for steering and a steering mechanism for changing a steering angle of a steered wheel are not mechanically coupled, and the steering mechanism is driven by a steering motor. There,
Rotation angle detection means for detecting the rotation angle of the steering member;
Target turning angle setting means for setting a target turning angle based on the rotation angle detected by the rotation angle detection means;
A low-pass filter that performs low-pass filter processing on the target turning angle calculated by the target turning angle setting means;
A steering apparatus for a vehicle including steering control means for controlling the steering motor based on a target turning angle after the low-pass filter processing by the low-pass filter. Vehicle speed detection means for detecting the vehicle speed;
The vehicle steering apparatus according to claim 1, further comprising a cutoff frequency control unit that controls a cutoff frequency of the low-pass filter based on a vehicle speed detected by the vehicle speed detection unit. A cargo handling device provided on the vehicle body;
A load detection means for detecting a load that is the weight of the load loaded on the cargo handling device;
The vehicle steering apparatus according to claim 1, further comprising: a cutoff frequency control unit that controls a cutoff frequency of the low-pass filter based on the loaded load detected by the load detection unit. A cargo handling device provided on the vehicle body;
A load detection means for detecting a load that is the weight of the load loaded on the cargo handling device;
Vehicle speed detection means for detecting the vehicle speed;
The cut-off frequency control means for controlling a cut-off frequency of the low-pass filter based on a vehicle speed detected by the vehicle speed detection means and a loaded load detected by the load detection means. Vehicle steering system.   The cut-off frequency control means is configured to control the cut-off frequency of the low-pass filter in consideration of whether it is forward or reverse. Vehicle steering system.   The vehicle steering device according to any one of claims 1 to 5, wherein the steering member is a steering lever disposed on a side of a driver seat.

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