Motor control device

Abstract

This motor control device comprises: a first control unit that calculates a first torque command value by performing, on a target steering angle, control for bringing an actual steering angle or an estimated actual steering angle value closer to the target steering angle; an inertia correction unit that calculates a second torque command value by performing, on the first torque command value, processing for causing an apparent second inertia seen by the first control unit to be a target apparent inertia greater than an actual second inertia; and a second control unit that controls an electric motor on the basis of the second torque command value.

Description

Motor control device Related applications

[0001] This application corresponds to Japanese Patent Application No. 2024-198391, filed with the Japan Patent Office on November 13, 2024, and the full disclosure of this application is incorporated herein by reference.

[0002] This disclosure relates to a control device for an electric motor used for steering angle control.

[0003] Patent Document 1 below discloses a power steering system that includes an electric power steering system and a hydraulic power steering system. In this power steering system, the auxiliary steering torque provided by the electric power steering system and the auxiliary steering torque provided by the hydraulic power steering system are shared according to the vehicle speed.

[0004] Patent Document 2 discloses a motor control device comprising: an assist torque command value setting unit that generates an assist torque command value; a manual steering command value generation unit that generates a manual steering command value; an integrated angle command value calculation unit that calculates an integrated angle command value by adding the manual steering command value to the automatic steering command value; and a switching unit that switches between a first control that controls the electric motor based only on the assist torque command value and a second control that controls the electric motor based on the integrated angle command value, based on a switching signal.

[0005] Japanese Patent Publication No. 2006-213094, International Publication No. 2023 / 286169

[0006] A power steering system is known in which a torsion bar for an electric power steering device is present in the power transmission path between the steering wheel and the steering wheels. In such a power steering system, the inertia of one inertial system located on the opposite side of the steering wheels from the torsion bar and connected to the torsion bar is called the first inertia J １ The inertia of one inertia that is connected to the first inertia via the torsion bar and rotates relative to the motor shaft of the electric motor is defined as the second inertia J. ２ This is how it is defined.

[0007] One example of this type of power steering system is the column-type electric power steering system shown in Figure 9.

[0008] The column-type electric power steering system 401 comprises a steering wheel 402, a steering mechanism 404 that steers the steering wheels 403 in conjunction with the rotation of the steering wheel 402, and a steering assist mechanism 405. The steering wheel 402 and the steering mechanism 404 are mechanically connected via a steering shaft 406 and an intermediate shaft 407.

[0009] The steering shaft 406 includes an input shaft 408 connected to the steering wheel 402 and an output shaft 409 connected to an intermediate shaft 407. The input shaft 408 and the output shaft 409 are connected to each other so as to be rotatable relative to each other via a torsion bar 410. A torque sensor 412 is located near the torsion bar 410.

[0010] The steering mechanism 404 consists of a rack and pinion mechanism including a pinion shaft 413 and a rack shaft 414. Steering wheels 403 are connected to each end of the rack shaft 414 via tie rods 415 and knuckle arms (not shown). The pinion shaft 413 is connected to an intermediate shaft 407. The pinion shaft 413 rotates in conjunction with the steering of the steering wheel 402. A pinion 416 is connected to the tip of the pinion shaft 413.

[0011] A rack 417 that meshes with a pinion 416 is formed in the axial middle portion of the rack shaft 414. The rotation of the pinion shaft 413 is converted into axial movement of the rack shaft 414 by the pinion 416 and the rack 417. By moving the rack shaft 414 in the axial direction, the steering wheel 403 can be steered.

[0012] The steering assist mechanism 405 includes an electric motor 418 for generating steering assist force and a reduction gear 419 for amplifying the output torque of the electric motor 418 and transmitting it to the steering mechanism 404. The reduction gear 419 consists of a worm gear mechanism including a worm gear 420 and a worm wheel 421 that meshes with the worm gear 420.

[0013] The reduction ratio N of the speed reducer 419 is defined as the ratio (θwg / θww) of the worm gear angle θwg, which is the rotation angle of the worm gear 420, to the worm wheel angle θww, which is the rotation angle of the worm wheel 421. The worm gear 420 is rotationally driven by the electric motor 418. Also, the worm wheel 421 is integrally and rotatably connected to the output shaft 409.

[0014] In the column type electric power steering system 401 of FIG. 9, the first inertia J １ is represented by the following equation (1).

[0015] J １ = inertia of the input shaft 408 + inertia of the steering wheel 402... (1) However, when the inertia of the input shaft 408 is small compared to the inertia of the steering wheel 402, the inertia of the steering wheel 402 may be regarded as the first inertia J １

[0016] The second inertia J ２ is represented by the following equation (2).

[0017] J ２ = J ｃｏｌｕｍｎ&ｒａｃｋ + J ｍｏｔｏｒ · N ２ ... (2) J ｃｏｌｕｍｎ&ｒａｃｋ : inertia of the portion between the torsion bar 410 and the tie rod 415 J ｍｏｔｏｒ · N ２ : inertia obtained by converting the inertia of the motor shaft into the rotational direction inertia of the output shaft 409 (equivalent inertia of the motor shaft output shaft) J ｍｏｔｏｒ : inertia of the motor shaft N: reduction ratio of the speed reducer 419 (ratio of the rotational speed of the motor shaft to the rotational speed of the output shaft 409)

[0018] J ｃｏｌｕｍｎ&ｒａｃｋ is represented by the following equation (3).

[0019] J ｃｏｌｕｍｎ&ｒａｃｋ= [Inertia of output shaft 409] + [Inertia obtained by converting the inertia of intermediate shaft 407 into rotational inertia of output shaft 409 (equivalent output shaft inertia of intermediate shaft 407)] + [Inertia obtained by converting the inertia of pinion shaft 413 into rotational inertia of output shaft 409 (equivalent output shaft inertia of pinion shaft)] + [Inertia obtained by converting the mass of rack shaft 414 into rotational inertia of pinion shaft and then converting the obtained inertia into rotational inertia of output shaft 409 (equivalent output shaft inertia of rack shaft)] ... (3)

[0020] However, [equivalent output axis inertia of the pinion axis + equivalent output axis inertia of the rack axis] is equal to [inertia of the output axis 409 + equivalent output axis inertia of the intermediate axis 407 + J]. ｍｏｔｏｒ ・N ２ If it is smaller than [the inertia of the output shaft 409 + the equivalent output shaft inertia of the intermediate shaft 407 + J] ｍｏｔｏｒ ・N ２ ] to the second inertia J ２ It can be considered as such.

[0021] In some column-type electric power steering systems, there is no reduction gear between the electric motor 418 and the output shaft 409, or there is a reduction gear between the electric motor 418 and the output shaft 409, but the reduction ratio of the reduction gear is small, resulting in the first inertia J １ Compared to the second inertia J ２ There are electric power steering systems with extremely small motors. In such electric power steering systems, there is a problem in that control becomes difficult when the control system for the electric motor is implemented by software.

[0022] Specifically, the resonant frequency of the output shaft 409 as seen from the electric motor 418 is expressed by the following equation (4).

[0023] ω ｒ = K { (1 / J ２ ) + (1 / J) １ )} １／２ …(4) K: Spring constant of the torsion bar J ２ :Second inertia J １ :1st inertia

[0024] Torque applied to the output shaft is the output shaft steering angle θ ｐ The time it takes for the signal to be transmitted is the time constant τ ｒ Therefore, the time constant τｒ This can be expressed by the following equation (5).

[0025] τ ｒ = 1 / ω ｒ =1 / [K{(1 / J ２ ) + (1 / J) １ )}] １／２ …(5)

[0026] time constant τ ｒ This is the second inertia J ２ is the first inertia J １ When it is extremely small relative to, the second inertia J ２ This becomes dominant, and the second inertia J ２ The smaller the time constant τ, the smaller it is. ｒ It becomes smaller. For example, 1 / J ２ Compared to 1 / J １ J ２ When τ is small, ｒ ≒(J ２ / K) １／２ This is the result.

[0027] When implementing an electric motor control system using software, the control period and sensing period are time constants τ. ｒ It is preferable that it be about one-tenth or less of the total. For example, J ２ =0.001[kgm ２ ], if K = 100 [Nm / rad], τ ｒ This results in a value of 3.2 [ms], and the preferred control and sensing periods are 0.32 [ms] or less. Therefore, control becomes difficult with the current microcontroller and sensor performance.

[0028] The purpose of this disclosure is to provide a motor control device that enables the control system of an electric motor to be implemented by software, even in a power steering system where the second inertia is extremely small compared to the first inertia.

[0029] One embodiment of the present disclosure provides a motor control device for an electric motor for an electric power steering device, in a power steering system in which a torsion bar for an electric power steering device is present in the power transmission path between a steering wheel and a steering wheel, the motor control device includes: a first control unit that calculates a first torque command value by performing control on the target steering angle to bring the actual steering angle or an estimated actual steering angle closer to the target steering angle; an inertia correction unit that calculates a second torque command value by performing processing on the first torque command value to make the apparent second inertia as seen from the first control unit greater than the actual second inertia, with the inertia of one inertia system located on the opposite side of the torsion bar from the steering wheel and connected to the torsion bar being the first inertia, and the inertia of one inertia connected to the first inertia via the torsion bar and rotating relative to the motor shaft of the electric motor being the second inertia; and a second control unit that controls the electric motor based on the second torque command value.

[0030] In this configuration, even in power steering systems where the second inertia is extremely small compared to the first inertia, the electric motor control system can be implemented using software.

[0031] Figure 1 is a schematic diagram showing the general configuration of a power steering system to which a motor control device according to one embodiment of the present disclosure is applied. Figure 2 is a block diagram showing the electrical configuration of the power steering system. Figure 3 is a block diagram for explaining the electrical configuration of the motor control ECU according to the present embodiment. Figure 4 is a block diagram for explaining the electrical configuration of a comparative example to the motor control ECU according to the present embodiment. Figure 5 is a block diagram for explaining the electrical configuration of the motor control ECU according to a first modified example. Figure 6 is a block diagram for explaining the electrical configuration of a comparative example to the motor control ECU according to a first modified example. Figure 7 is a block diagram for explaining the electrical configuration of the motor control ECU according to a second modified example. Figure 8 is a schematic diagram showing the general configuration of a dual-pinion type electric power steering system. Figure 9 is a schematic diagram showing the general configuration of a column type electric power steering system.

[0032] [Description of Embodiments of the Present Disclosure] One embodiment of the present disclosure provides a motor control device for an electric motor for an electric power steering device, in a power steering system in which a torsion bar for an electric power steering device is present in the power transmission path between a steering wheel and a steering wheel, the motor control device comprising: a first control unit that calculates a first torque command value by performing control on the target steering angle to bring the actual steering angle or an estimated actual steering angle closer to the target steering angle; an inertia correction unit that calculates a second torque command value by performing processing on the first torque command value to make the apparent second inertia as seen from the first control unit greater than the actual second inertia, with the inertia of one inertia system located on the opposite side of the torsion bar from the steering wheel and connected to the torsion bar being the first inertia, and the inertia of one inertia connected to the first inertia via the torsion bar and rotating relative to the motor shaft of the electric motor being the second inertia; and a second control unit that controls the electric motor based on the second torque command value.

[0033] In this configuration, even in power steering systems where the second inertia is extremely small compared to the first inertia, the electric motor control system can be implemented using software.

[0034] In one embodiment of the present disclosure, the inertia correction unit includes an angular acceleration calculation unit that calculates the actual rudder angular acceleration by taking the second derivative of the actual rudder angle, an inertia difference multiplication unit that multiplies the actual rudder angular acceleration by the difference between the target apparent inertia and the actual second inertia, and a subtraction unit that calculates the second torque command value by subtracting the multiplication result of the inertia difference multiplication unit from the first torque command value.

[0035] In one embodiment of this disclosure, the first inertia is J １ Therefore, the target apparent inertia is 0.7 × J １ That's all.

[0036] In one embodiment of this disclosure, the first inertia is J １ Therefore, the target apparent inertia is 0.7 × J １ The above is 1.3 × J １ The following applies:

[0037] In one embodiment of the present disclosure, the first control unit includes a feedback control unit for bringing the actual steering angle or the estimated actual steering angle closer to the target steering angle, a feedforward control unit for inertia compensation, and a torque addition unit for adding a feedback control torque calculated by the feedback control unit and a feedforward control torque calculated by the feedforward control unit, wherein the feedforward control unit calculates the feedforward control torque by multiplying the second derivative of the target steering angle by the target apparent inertia.

[0038] In one embodiment of the present disclosure, the first control unit further includes a disturbance torque estimation unit that estimates disturbance torques other than the motor torque of the electric motor acting on an object driven by the electric motor, and the first control unit further includes a disturbance compensation unit that subtracts the disturbance torque estimated by the disturbance torque estimation unit from the calculation result of the torque addition unit.

[0039] [Detailed Description of Embodiments of the Disclosure] Embodiments of the Disclosure will be described in detail below with reference to the accompanying drawings.

[0040] Figure 1 is a schematic diagram showing the general configuration of a power steering system to which a motor control device according to one embodiment of the present disclosure is applied. In Figure 1, the left side of the dashed line 29 is a side view of the vehicle as seen from the side, and the right side of the dashed line 29 is a top view of the vehicle as seen from above.

[0041] This power steering system 1 is a power steering system that combines the functions of an electric power steering device and a hydraulic power steering device. The power steering system 1 includes a steering wheel 2, a steering shaft 3, an intermediate shaft 4, a bevel gear section 5, a power transmission shaft 6, a ball screw type hydraulic power steering mechanism (hereinafter referred to as "hydraulic power steering mechanism 7"), a steering mechanism 8, an electric power steering mechanism 9, and the like.

[0042] The steering shaft 3 includes an input shaft 10 connected to the steering wheel 2 and an output shaft 11 connected to the intermediate shaft 4. The input shaft 10 and the output shaft 11 are connected to each other so as to be rotatable relative to each other via a torsion bar 12 (a torsion bar for an electric power steering system).

[0043] A torque sensor 13 is positioned near the torsion bar 12. The torque sensor 13 determines the torque applied to the steering wheel 2 based on the relative rotational displacement of the input shaft 10 and the output shaft 11 (hereinafter referred to as "torsion bar torque T"). ｔｂ This means that the torsion bar torque T detected by the torque sensor 13 is detected. ｔｂ For example, the torque for steering to the left is detected as a positive value, and the torque for steering to the right is detected as a negative value, and the larger the absolute value, the greater the torsion bar torque T. ｔｂ Assume that the size of will increase.

[0044] The intermediate shaft 4 is connected to the input shaft of the bevel gear section 5. The output shaft of the bevel gear section 5 is connected to the input shaft of the hydraulic power steering mechanism 7 via the power transmission shaft 6. The hydraulic power steering mechanism 7 includes a torsion bar (torsion bar for hydraulic power steering device) for detecting steering force and adjusting hydraulic flow rate, although this is not shown in the figure.

[0045] The steering mechanism 8 includes a pitman arm 14, a drag link 15, a knuckle arm 16, kingpin shafts 17 and 18, a tie rod arm 19, and a tie rod 20.

[0046] One end of the pitman arm 14 is connected to the sector shaft of the hydraulic power steering mechanism 7. The dashed line 21 in the figure represents the axle beam.

[0047] The electric power steering mechanism 9 includes an electric motor 22 and a reduction gear 23 for amplifying the output torque of the electric motor 22 and transmitting it to the output shaft 11. The reduction gear 23 consists of a worm gear mechanism including a worm gear 24 and a worm wheel 25 that meshes with the worm gear 24.

[0048] The reduction ratio N of the reduction gear 23 is defined as the ratio of the worm gear angle (the rotation angle of the worm gear) to the worm wheel angle (the rotation angle of the worm wheel). The rotor rotation angle θ of the electric motor 22 ｍ This is detected by the rotation angle sensor 26. In this embodiment, the reduction ratio N is relatively small. The reduction ratio N is, for example, 5 or less.

[0049] When the steering wheel 2 rotates, this rotational torque is transmitted to the steering shaft 3, intermediate shaft 4, bevel gear section 5, power transmission shaft 6, and ball screw type hydraulic power steering mechanism 7, causing the pitman arm 14 to swing. This swinging of the pitman arm 14 causes the drag link 15 to move in the front-rear direction, the knuckle arm 16 to swing, and the steering wheels 27 and 28 to turn.

[0050] When the electric motor 22 rotates, this rotational torque is transmitted to the output shaft 11, causing the steering wheels 27 and 28 to be steered via the same power transmission path as described above. In other words, by rotating the output shaft 11 with the electric motor 22, steering of the steering wheels 27 and 28 becomes possible.

[0051] The torque applied to the output shaft 11 (an example of what the electric motor 22 drives) includes the motor torque supplied by the electric motor 22 and disturbance torques other than the motor torque. Disturbance torque T ｌｃ Torsion bar torque T ｔｂ And, road surface reaction torque (road surface load torque) T ｒｌ And the friction torque T generated in the reduction gear 23. ｆ This includes, etc. Torsion bar torque T ｔｂ This is the torque applied from the steering wheel 2 to the output shaft by the force applied to the steering wheel 2 by the driver, the force generated by the steering wheel inertia, etc. Road surface reaction torque T ｌｓ This is the torque applied to the output shaft 11 from the steering wheels 27 and 28 due to the self-aligning torque generated in the tires, the forces generated by the suspension and tire-wheel alignment, etc.

[0052] In the power steering system 1 shown in Figure 1, a torsion bar 12 for an electric power steering device is present in the power transmission path between the steering wheel 2 and the steering wheels 27 and 28. In such a power steering system 1, the inertia of one inertial system located on the opposite side of the torsion bar 12 from the steering wheels 27 and 28 and connected to the torsion bar 12 is the first inertia J １ It is defined as follows. Also, the first inertia J is transmitted via the torsion bar 12. １ The inertia of one inertia that is connected and rotates relative to the motor shaft of the electric motor 22 is the second inertia J. ２ It is defined as follows.

[0053] In the power steering system 1 shown in Figure 1, the first inertia J １ This can be expressed by the following equation (6).

[0054] J １ = Inertia of input shaft 10 + Inertia of steering wheel 2 ... (6) However, if the inertia of input shaft 10 is smaller than the inertia of steering wheel 2, the inertia of steering wheel 2 may be considered as the first inertia. In this embodiment, the inertia of steering wheel 2 is considered as the first inertia.

[0055] In the power steering system 1 shown in Figure 1, the second inertia J ２ This can be expressed by the following equation (7).

[0056] J ２ = J ｃｏｌｕｍｎ +J ｍｏｔｏｒ ・N ２ …(7) J ｃｏｌｕｍｎ : Inertia of the portion between the torsion bar 12 and the rotary valve J ｍｏｔｏｒ ・N ２ : Inertia obtained by converting the inertia of the motor shaft into the rotational inertia of the output shaft 11 (equivalent inertia of the output shaft of the motor shaft) J ｍｏｔｏｒ : Inertia of the motor shaft N: Reduction ratio of the reducer 23 (ratio of the rotational speed of the motor shaft to the rotational speed of the output shaft 11)

[0057] J ｃｏｌｕｍｎ This can be expressed by the following equation (8).

[0058] J ｃｏｌｕｍｎ= [Inertia of output shaft 11] + [Inertia obtained by converting the inertia of intermediate shaft 4 into the inertia in the rotational direction of output shaft 11 (equivalent inertia of output shaft of intermediate shaft 4)] + [Inertia obtained by converting the inertia of bevel gear portion 5 into the inertia in the rotational direction of output shaft 11 (equivalent inertia of output shaft of bevel gear portion 5)] + [Inertia obtained by converting the inertia of power transmission shaft 6 into the inertia in the rotational direction of output shaft 11 (equivalent inertia of output shaft of power transmission shaft 6)]…(8)

[0059] However, when [equivalent inertia of output shaft of bevel gear portion 5 + equivalent inertia of output shaft of power transmission shaft 6] is smaller than [inertia of output shaft 11 + equivalent inertia of output shaft of intermediate shaft 4 + J ｍｏｔｏｒ ·N ２ , [inertia of output shaft 11 + equivalent inertia of output shaft of intermediate shaft 4 + J ｍｏｔｏｒ ·N ２ may be regarded as the second inertia J ２ . In this embodiment, [inertia of output shaft 11 + equivalent inertia of output shaft of intermediate shaft 4 + J ｍｏｔｏｒ ·N ２ is regarded as the second inertia J ２ .

[0060] FIG. 2 is a block diagram showing the electrical configuration of the power steering system 1.

[0061] [[ID=2**5]] The vehicle is provided with an automatic steering ECU 101 and a motor control ECU 102. The motor control ECU 102 is an example of the "motor control device" in the present disclosure.

[0062] The automatic steering ECU 101 outputs a mode signal S ｍｏｄｅ indicating whether the steering mode is the automatic steering mode or the manual steering mode. Further, the automatic steering ECU 101 generates an automatic steering command value θ ＡＤ for automatic steering in the automatic steering mode. In the following, the configuration and its operation applied when the steering mode is the automatic steering mode will be described.

[0063] In this embodiment, the automatic steering control is, for example, control for driving the vehicle along a target travel line (target trajectory). The automatic steering command value θ ＡＤ is a target value of the steering angle for automatically driving the vehicle along the target travel line.

[0064] In this embodiment, the automatic steering command value θ ＡＤ is represented by the amount of rotation (rotation angle) from the neutral position of the output shaft 11. The amount of rotation from the neutral position in the left steering direction is represented as a positive value, and the amount of rotation from the neutral position in the right steering direction is represented as a negative value.

[0065] Note that the automatic steering control (driving support control) may be, for example, lane centering assist (LCA) control that assists steering so that the vehicle travels in the center of the driving lane, lane keeping assist (LKA) control that assists steering so that the vehicle maintains within the driving lane, or the like.

[0066] When the steering mode is the automatic steering mode, the motor control ECU 102 drives and controls the electric motor 22 using at least the automatic steering command value θ ＡＤ , the output signal of the rotation angle sensor 26, and the torsion bar torque T ｔｂ detected by the torque sensor 13. ＡＤ and the output signal of the rotation angle sensor 26.

[0067] When the steering mode is the manual mode, the motor control ECU 102 calculates an assist torque command value based on, for example, the torsion bar torque T ｔｂ detected by the torque sensor 13, and controls the electric motor 22 based on the calculated assist torque command value.

[0068] FIG. 3 is a block diagram for explaining the electrical configuration of the motor control ECU 102 according to the present embodiment. FIG. 4 is a block diagram for explaining the electrical configuration of a comparative example (hereinafter referred to as "first comparative example") with respect to the motor control ECU 102 according to the present embodiment.

[0069] First, referring to FIG. 4, the motor control ECU 102X according to the first comparative example will be described.

[0070] The motor control ECU 102X according to the first comparative example includes a microcomputer 50X, a drive circuit (inverter circuit) 41 that is controlled by the microcomputer 50X and supplies power to the electric motor 22, and a current flowing through the electric motor 22 (hereinafter referred to as "motor current Iｍ It includes a current detection circuit 42 for detecting the following:

[0071] The microcomputer 50X is equipped with a CPU and memory (ROM, RAM, non-volatile memory, etc.), and functions as multiple function processing units by executing a predetermined program. These multiple function processing units include a low-pass filter (LPF) 51, a feedback control unit 52, a first reduction ratio division unit 53, a torque control unit 54, a rotation angle calculation unit 55, and a second reduction ratio division unit 56.

[0072] The rotation angle calculation unit 55 calculates the rotor rotation angle θ of the electric motor 22 based on the output signal of the rotation angle sensor 26. ｍ The second reduction ratio division unit 56 calculates the rotor rotation angle θ calculated by the rotation angle calculation unit 55. ｍ By dividing by the reduction ratio N, the rotor rotation angle θ is obtained. ｍ The rotation angle (actual steering angle) of the output shaft 11 is θ ｐ Convert to [the appropriate value].

[0073] The low-pass filter 51 controls the automatic steering command value θ. ＡＤ A low-pass filter is applied to this value. The automatic steering command value θ after low-pass filtering is then processed. ｃｍｄ This is provided to the feedback control unit 52.

[0074] The feedback control unit 52 controls the automatic steering command value θ. ｃｍｄ Actual steering angle θ ｐ Angle feedback processing is performed to bring the values ​​closer together. Specifically, the feedback control unit 52 includes an angle deviation calculation unit 57 and a PID control unit 58. The angle deviation calculation unit 57 receives the automatic steering command value θ from the low-pass filter 51. ｃｍｄ The actual steering angle θ is calculated by the second reduction ratio division unit 56. ｐ The deviation (θ) ｃｍｄ -θ ｐ ) and the angular deviation θ ｄｉｆｆ It is calculated as follows.

[0075] The PID control unit 58 controls the angular deviation θ ｄｉｆｆBy performing PID (proportional-integral-derivative) calculations on this, the output shaft torque command value T, which is the torque command value for the output shaft 11, is obtained. ｐ，ｃｍｄ Perform the calculation.

[0076] The first reduction ratio division unit 53 calculates the output shaft torque command value T ｐ，ｃｍｄ By dividing by the reduction ratio N, the motor torque command value T, which is the torque command value for the electric motor 22, is obtained. ｍ，ｃｍｄ The motor torque command value T is calculated. ｍ，ｃｍｄ This is supplied to the torque control unit 54.

[0077] The torque control unit 54 controls the motor torque of the electric motor 22 when it reaches the motor torque command value T. ｍ，ｃｍｄ The drive circuit 41 is driven to approach this value. As the torque control unit 54, for example, the torque control unit (55) shown in Figures 2 and 8 of International Publication No. 2023 / 286169 (Patent Document 2) can be used. In that case, the torque control unit 54 receives the motor torque command value T ｍ，ｃｍｄ The current command value is calculated by dividing by the torque coefficient of the electric motor 22. Then, the torque control unit 54 calculates the motor current I detected by the current detection circuit 42. ｍ Current feedback control is performed to bring the current value closer to the commanded current value.

[0078] In the first comparative example, the time constant τ ｒ This is represented by formula (5) above.

[0079] Next, with reference to Figure 3, the motor control ECU 102 according to this embodiment will be described. In Figure 3, the parts corresponding to the parts in Figure 4 are denoted by the same reference numerals as in Figure 4.

[0080] In this embodiment, the motor control ECU 102 differs from the first comparative example in that an inertia correction unit 59 is added as a function processing unit of the microcomputer 50. The inertia correction unit 59 corrects the apparent second inertia as seen from the feedback control unit 52 (PID control unit 58) to the actual second inertia J ２ It is designed to be larger than that.

[0081] As the apparent inertia as seen from the feedback control unit 52 is increased, it is preferable that the proportional gain Kp, integral gain Ki, and differential gain Kd used in the PID control unit 58 be set to larger values ​​than those of the first comparative example.

[0082] In the motor control ECU 102 according to this embodiment, the automatic steering command value θ ＡＤ Alternatively, the automatic steering command value θ after low-pass filtering. ｃｍｄ This is an example of the "target steering angle" in this disclosure. The feedback control unit 52 is an example of the "first control unit" in this disclosure. The torque control unit 54 is an example of the "second control unit" in this disclosure. The actual steering angle θ calculated by the second reduction ratio division unit 56 ｐ This is an example of the "actual rudder angle" as defined in this disclosure.

[0083] In the motor control ECU 102 according to this embodiment, the output shaft torque command value output from the feedback control unit (first control unit) 52 is called the "first output shaft torque command value T ｐ１，ｃｍｄ "That's what we'll decide."

[0084] The inertia correction unit 59 consists of an angular acceleration calculation unit 60, an inertia difference multiplication unit 61, and a subtraction unit 62. The angular acceleration calculation unit 60 calculates the actual steering angle θ. ｐ By taking the second derivative of this, we obtain the actual steering angular acceleration d ２ θ ｐ / dt ２ Perform the calculation.

[0085] In this embodiment, the target value of apparent inertia as seen from the feedback control unit 52 is the target apparent inertia J. ｉｄｅａｌ Let's go with that. Target apparent inertia J ｉｄｅａｌ This is the actual second inertia J ２ It is set to a value greater than this. Target apparent inertia J ｉｄｅａｌ This is the first inertia J １ It is preferable that it be greater than 0.7 times. Target apparent inertia J ｉｄｅａｌ This is the first inertia J １ It is preferable that it is greater than 0.7 times and less than 1.3 times.

[0086] The inertia difference multiplication unit 61 calculates the actual steering angle acceleration d ２ θｐ / dt ２ To the target apparent inertia J ｉｄｅａｌ and the actual second inertia J ２ The difference with (J ｉｄｅａｌ -J ２ Multiply by ).

[0087] The subtraction unit 62 calculates the first output shaft torque command value T. ｐ１，ｃｍｄ From the multiplication result of the inertia difference multiplication unit 61 (J ｉｄｅａｌ -J ２ )d ２ θ ｐ / dt ２ By subtracting this, the second output shaft torque command value T is obtained. ｐ２，ｃｍｄ Perform the calculation.

[0088] First output shaft torque command value T ｐ１，ｃｍｄ This is an example of the "first torque command value" in this disclosure, and the second output shaft torque command value T ｐ２，ｃｍｄ This is an example of the "second torque command value" in this disclosure.

[0089] Second output shaft torque command value T ｐ２，ｃｍｄ This is expressed by the following equation (9).

[0090] T ｐ２，ｃｍｄ = T ｐ１，ｃｍｄ - (J ｉｄｅａｌ -J ２ )d ２ θ ｐ / dt ２ …(9)

[0091] In the motor control ECU 102 according to this embodiment, T ｐ２，ｃｍｄ = J ２ d ２ θ ｐ / dt ２ Therefore, equation (10) holds true.

[0092] T ｐ１，ｃｍｄ - (J ｉｄｅａｌ -J ２ )d ２ θ ｐ / dt ２ = J ２ d ２ θ ｐ / dt ２ ... (10)

[0093] When this is transformed, Tｐ１，ｃｍｄ This can be expressed by the following equation (11).

[0094] T ｐ１，ｃｍｄ = J ２ d ２ θ ｐ / dt ２ + (J ｉｄｅａｌ -J ２ )d ２ θ ｐ / dt ２ = J ｉｄｅａｌ d ２ θ ｐ / dt ２ …(11)

[0095] In other words, the apparent inertia as seen from the feedback control unit 52 is J ｉｄｅａｌ This results in the apparent inertia as seen from the feedback control unit 52 being replaced by the actual second inertia J. ２ It can be made larger than that.

[0096] Apparent time constant τ ｉｄｅａｌ This can be expressed by the following equation (12).

[0097] τ ｉｄｅａｌ =1 / [K{(1 / J ｉｄｅａｌ ) + (1 / J) １ )}] １／２ ... (12)

[0098] This results in the apparent time constant τ ｉｄｅａｌ The time constant τ of the first comparative example ｒ This makes it possible to make it larger. As a result, the control period and sensing period can be achieved even with the current microcontroller and sensor performance. This makes the second inertia J ２ is the first inertia J １ Even in extremely small power steering systems, it becomes possible to implement the control system for the electric motor 22 using software.

[0099] Figure 5 is a block diagram illustrating the electrical configuration of the motor control ECU 102A according to the first modified example. Figure 6 is a block diagram illustrating the electrical configuration of a comparative example (hereinafter referred to as the "second comparative example") to the motor control ECU 102A according to the first modified example.

[0100] First, with reference to Figure 6, the motor control ECU 102Y related to the second comparative example will be described. In Figure 6, the parts corresponding to the parts in Figure 4 are denoted by the same reference numerals as in Figure 4.

[0101] The motor control ECU 102Y according to the second comparative example comprises a microcomputer 50Y, a drive circuit 41 controlled by the microcomputer 50, and a motor current I ｍ It is equipped with a current detection circuit 42 for detecting [something].

[0102] The microcomputer 50Y includes a low-pass filter (LPF) 51, a feedback control unit 71, a feedforward control unit 72, a torque addition unit 73, a disturbance observer (disturbance torque estimation unit) 74, a disturbance torque compensation unit 75, a first reduction ratio division unit 53, a torque control unit 54, a rotation angle calculation unit 55, and a second reduction ratio division unit 56.

[0103] The feedback control unit 71 controls the automatic steering command value θ ｃｍｄ Actual steering angle θ ｐ Estimated value of (steer angle estimate ^θ) ｐ Angle feedback processing is performed to bring the value closer to the specified value. Specifically, the feedback control unit 71 includes an angle deviation calculation unit 76 and a PD control unit 77. The angle deviation calculation unit 76 processes the automatic steering command value θ provided from the low-pass filter 51. ｃｍｄ And the steering angle estimate ^θ given by the disturbance observer 74. ｐ The deviation θ ｄｉｆｆ (=θ) ｃｍｄ -θ ｐ The angle deviation calculation unit 76 calculates the automatic steering command value θ. ｃｍｄ The actual steering angle θ is calculated by the second reduction ratio division unit 56. ｐ The deviation (θ) ｃｍｄ -θ ｐ ) and the angular deviation θ ｄｉｆｆ You may also perform the calculation as follows.

[0104] The PD control unit 77 receives the angle deviation θ calculated by the angle deviation calculation unit 76. ｄｉｆｆ By performing a PD calculation (proportional-derivative calculation) on it, the feedback control torque Tｆｂ The following is calculated: Feedback control torque T ｆｂ This is applied to the torque addition unit 73.

[0105] The input / output characteristics of the PD control unit 77 are expressed by the following equation (13).

[0106] T ｆｂ / θ ｄｉｆｆ = J ２ ω ｐｏｌｅ ２ +2J ２ ζ ｐｏｌｅ ω ｐｏｌｅ ・s …(13) ω ｐｏｌｅ : Target response frequency ζ for PD control ｐｏｌｅ : Target damping coefficient for PD control (usually 1)

[0107] J on the right side of equation (13) ２ ω ｐｏｌｅ ２ This is the proportional gain Kp, and 2J on the right side of equation (13). ２ ζ ｐｏｌｅ ω ｐｏｌｅ This is the differential gain Kd.

[0108] The feedforward control unit 72 controls the second inertia J ２ It is provided to compensate for the response delay caused by and improve the responsiveness of the control. The feedforward control unit 72 includes an angular acceleration calculation unit 78 and an inertia multiplication unit 79. The angular acceleration calculation unit 78 calculates the automatic steering command value θ ｃｍｄ By taking the second derivative of the target angular acceleration d, ２ θ ｃｍｄ / dt ２ Perform the calculation.

[0109] The inertia multiplication unit 79 calculates the target angular acceleration d calculated by the angular acceleration calculation unit 78. ２ θ ｃｍｄ / dt ２ second inertia J ２ By multiplying by this, the feedforward controlled torque T ｆｆ (=J ２ d ２ θ ｃｍｄ / dt ２ ) is calculated. Feedforward controlled torque T ｆｆThis is provided to the torque addition unit 73 as an inertia compensation value.

[0110] The torque addition unit 73 controls the feedback-controlled torque T ｆｂ Feedforward controlled torque T ｆｆ By adding this, the basic torque command value (T ｆｂ +T ｆｆ ) is calculated.

[0111] The disturbance torque compensation unit 75 controls the basic torque command value (T ｆｂ +T ｆｆ ) From this, the disturbance torque estimate ^T given by the disturbance observer 74 ｌｃ By subtracting this, the output shaft torque command value T ｐ，ｃｍｄ (=T ｆｂ +T ｆｆ -^T ｌｃ This calculates the output shaft torque command value T, which is compensated for disturbance torque. ｐ，ｃｍｄ You can obtain this.

[0112] The first reduction ratio division unit 53 calculates the output shaft torque command value T ｐ，ｃｍｄ By dividing this by the reduction ratio N of the reduction gear 23, the motor torque command value T, which is the torque command value for the electric motor 22, is obtained. ｍ，ｃｍｄ Perform the calculation.

[0113] The torque control unit 54 controls the motor torque of the electric motor 22 when it reaches the motor torque command value T. ｍ，ｃｍｄ The drive circuit 41 is driven to approach it.

[0114] The disturbance observer 74 is provided to estimate the nonlinear torque (disturbance torque: torque other than motor torque) that occurs as a disturbance on the output shaft 11 (an example of a drive target of the electric motor 22). The disturbance observer 74 estimates the output shaft torque command value T ｐ，ｃｍｄ (=N.T.) ｍ，ｃｍｄ ) and the actual steering angle θ calculated by the second reduction ratio division unit 56 ｐ Based on this, the disturbance torque (disturbance load) T ｌｃ and steering angle θ ｐ To estimate the disturbance torque T, ｌｃ and steering angle θ ｐ The estimated values ​​of each are ^T ｌｃ and ^θｐ It is represented as follows.

[0115] As the disturbance observer 74, for example, the disturbance torque estimation unit (64) shown in Figure 5 of International Publication No. 2023 / 286169 (Patent Document 2) can be used. However, in International Publication No. 2023 / 286169, the actual steering angle θ is used. ｐ This is represented by θ, where the steering angle θ ｐ The estimated value is represented by ^θ.

[0116] The transfer function of the disturbance observer 74 is expressed by the following equation (14).

[0117]

[0118] In equation (14), ω ｌｏ This is the target response frequency of the disturbance observer 74.

[0119] Next, with reference to Figure 5, a motor control ECU 102A according to the first modified example will be described. In Figure 5, parts corresponding to the parts in Figure 6 are denoted by the same reference numerals as in Figure 6.

[0120] The motor control ECU 102A according to the first modified example differs from the motor control ECU 102Y according to the second comparative example in the configuration of the microcomputer 50A.

[0121] The microcomputer 50A in Figure 5, compared to the microcomputer 50Y in Figure 6, measures the apparent inertia (apparent second inertia) as seen from the disturbance torque compensation unit 75 as the actual second inertia J. ２ The difference lies in the addition of an inertia correction unit 59A to make it even larger.

[0122] Furthermore, consequently, the proportional gain Kp and differential gain Kd used in the PD control unit 77A of the feedback control unit 71A, the inertia used in the inertia multiplication unit 79A of the feedforward control unit 72A, and the transfer function of the disturbance observer 74A differ from those of the second comparative example.

[0123] In the motor control ECU 102A according to the first modified example, the automatic steering command value θ ＡＤ Alternatively, the automatic steering command value θ after low-pass filtering. ｃｍｄThis is an example of the "target steering angle" in this disclosure. The configuration consisting of the feedback control unit 71A, the feedforward control unit 72A, the torque addition unit 73, and the disturbance torque compensation unit 75 is an example of the "first control unit" in this disclosure. The torque control unit 54 is an example of the "second control unit" in this disclosure. The steering angle estimate calculated by the disturbance observer 74 is an example of the "actual steering angle estimate" in this disclosure.

[0124] In the motor control ECU 102A according to the first modified example, the output shaft torque command value output from the disturbance torque compensation unit 75 is defined as "third output shaft torque command value T ｐ３，ｃｍｄ This will be the case. Also, the target value of apparent inertia as seen from the disturbance torque compensation unit 75 (first control unit) will be the target apparent inertia J. ｉｄｅａｌ Let's go with that. Target apparent inertia J ｉｄｅａｌ This is the first inertia J １ It is preferable that it be greater than 0.7 times. Target apparent inertia J ｉｄｅａｌ This is the first inertia J １ It is preferable that the value is greater than 0.1 times and less than 1.3.

[0125] The input / output characteristics of the PD control unit 77A are expressed by the following equation (15).

[0126] T ｆｂ / θ ｄｉｆｆ = J ｉｄｅａｌ ω ｐｏｌｅ ２ +2J ｉｄｅａｌ ζ ｐｏｌｅ ω ｐｏｌｅ ・s …(15)

[0127] In other words, the second inertia J in equation (13) that represents the input / output characteristics of the PD control unit 77 in Figure 5 ２ Target apparent inertia J ｉｄｅａｌ It is replaced by . Therefore, the proportional gain Kp is J ｉｄｅａｌ ω ｐｏｌｅ ２ Therefore, the differential gain Kd is 2J. ｉｄｅａｌ ζ ｐｏｌｅ ω ｐｏｌｅ This is the result.

[0128] The inertia multiplication unit 79A of the feedforward control unit 72A calculates the target angular acceleration d calculated by the angular acceleration calculation unit 78. ２ θ ｃｍｄ / dt ２ second inertia J ２ Instead, target apparent inertia J ｉｄｅａｌ By multiplying by the feedforward control torque T, ｆｆ (=J ｉｄｅａｌ d ２ θ ｃｍｄ / dt ２ ) is calculated.

[0129] The transfer function of the disturbance observer 74A is expressed by the following equation (16).

[0130]

[0131] The second inertia J in equation (14) represents the transfer function of the disturbance observer 74 in Figure 5. ２ Target apparent inertia J ｉｄｅａｌ It has been replaced with.

[0132] Feedback control torque T output from PD control unit 77A ｆｄ And the feedforward controlled torque T output from the inertia multiplication unit 79A ｆｆ This is added by the torque addition unit 73. The basic torque command value (T) is the result of the addition by the torque addition unit 73. ｆｂ +T ｆｆ The torque is supplied to the disturbance torque compensation unit 75.

[0133] The disturbance torque compensation unit 75 controls the basic torque command value (T ｆｂ +T ｆｆ ) Estimated disturbance torque ^T ｌｃ By subtracting this, the third output shaft torque command value T ｐ３，ｃｍｄ Perform the calculation.

[0134] The inertia correction unit 59A consists of an angular acceleration calculation unit 60, an inertia difference multiplication unit 61, and a subtraction unit 62A. The angular acceleration calculation unit 60 is composed of the actual steering angle θ ｐ By taking the second derivative of this, we obtain the actual steering angular acceleration d ２ θ ｐ / dt ２ Perform the calculation.

[0135] The inertia difference multiplication unit 61 calculates the actual steering angle acceleration d ２ θ ｐ / dt ２ To the target apparent inertia J ｉｄｅａｌ and the actual second inertia J ２ The difference with (J ｉｄｅａｌ -J ２ Multiply by ).

[0136] The subtraction unit 62A calculates the third output shaft torque command value T ｐ３，ｃｍｄ From the multiplication result of the inertia difference multiplication unit 61 (J ｉｄｅａｌ -J ２ )d ２ θ ｃ / dt ２ By subtracting this, the fourth output shaft torque command value T is obtained. ｐ４，ｃｍｄ Perform the calculation.

[0137] Third output shaft torque command value T ｐ３，ｃｍｄ This is an example of the "first torque command value" in this disclosure, and the fourth output shaft torque command value T ｐ４，ｃｍｄ This is an example of the "second torque command value" in this disclosure.

[0138] The first reduction ratio division unit 53 calculates the fourth output shaft torque command value T. ｐ４，ｃｍｄ By dividing this by the reduction ratio N of the reduction gear 23, the motor torque command value T, which is the torque command value for the electric motor 22, is obtained. ｍ，ｃｍｄ Perform the calculation.

[0139] The torque control unit 54 controls the motor torque of the electric motor 22 when it reaches the motor torque command value T. ｍ，ｃｍｄ The drive circuit 41 is driven to approach it.

[0140] Fourth output shaft torque command value T ｐ４，ｃｍｄ This can be expressed by the following equation (17).

[0141] T ｐ４，ｃｍｄ = T ｐ３，ｃｍｄ - (J ｉｄｅａｌ -J ２ )d ２ θ ｐ / dt ２ ... (17)

[0142] In the motor control ECU 102A according to the first modified example, T ｐ４，ｃｍｄ = J ２ d２ θ ｐ / dt ２ Therefore, equation (18) holds true.

[0143] T ｐ３，ｃｍｄ - (J ｉｄｅａｌ -J ２ )d ２ θ ｐ / dt ２ = J ２ d ２ θ ｐ / dt ２ ... (18)

[0144] When this is transformed, T ｐ３，ｃｍｄ This can be expressed by the following equation (19).

[0145] T ｐ３，ｃｍｄ = J ２ d ２ θ ｐ / dt ２ + (J ｉｄｅａｌ -J ２ )d ２ θ ｐ / dt ２ = J ｉｄｅａｌ d ２ θ ｐ / dt ２ …(19)

[0146] In other words, when viewed from the disturbance torque compensation unit 75, the plant's inertia is equal to the target apparent inertia J. ｉｄｅａｌ This is the result.

[0147] In this first modified example, the apparent time constant τ ｉｄｅａｌ Since it is expressed by the above equation (12), the apparent time constant τ ｉｄｅａｌ This makes it possible to make the time constant larger than that of the second comparative example. As a result, the control period and sensing period can be achieved even with the current microcontroller and sensor performance. This makes the second inertia J ２ is the first inertia J １ Even in extremely small power steering systems, it becomes possible to implement the control system for the electric motor 22 using software.

[0148] Figure 7 is a block diagram illustrating the electrical configuration of the motor control ECU 102B according to the second modified example. In Figure 7, parts corresponding to each part in Figure 5 are indicated by the same reference numerals as in Figure 5.

[0149] The motor control ECU 102B according to the second modification differs from the motor control ECU 102A according to the first modification in the configuration of the microcomputer 50B. Specifically, the microcomputer 50B in Figure 7 differs from the microcomputer 50A in Figure 5 in that it has an assist torque command value setting unit 81, a manual steering command value calculation unit 82, and an angle addition unit 83 added.

[0150] The assist torque command value setting unit 81 sets the assist torque command value T, which is the target value of the assist torque required for manual operation. ａｓ The assist torque command value setting unit 81 sets the torsion bar torque T detected by the torque sensor 13. ｔｂ Based on this, the assist torque command value T ａｓ Set it.

[0151] As the assist torque command value setting unit 81, for example, the assist torque command value setting unit (51) shown in Figure 2 of International Publication No. 2023 / 286169 (Patent Document 2) can be used. In that case, the torsion bar torque T ｔｂ Assist torque command value T ａｓ As an example of the settings, the example shown in Figure 3 of International Publication No. 2023 / 286169 can be used. The assist torque command value setting unit 81 is the torsion bar torque T ｔｂ And the assist torque command value T takes into account the vehicle speed V. ａｓ The setting may also be configured. In addition, the assist torque command value setting unit 81 sets the torsion bar torque T ｔｂ By multiplying by a preset constant, the assist torque command value T is obtained. ａｓ You may perform the calculation.

[0152] The manual steering command value calculation unit 82 basically calculates the steering angle (more precisely, the rotation angle θ of the output shaft 11) corresponding to the steering wheel operation when the driver operates the steering wheel 2.ｐ ) to manual steering command value θ ＭＤ It is provided for calculation purposes. The manual steering command value calculation unit 82 calculates the torsion bar torque T detected by the torque sensor 13. ｔｂ The assist torque command value T set by the assist torque command value setting unit 81. ａｓ And, the virtual load spring stiffness coefficient k ｍｄ And the virtual load viscous damping coefficient c ｍｄ The manual steering command value θ is used with ＭＤ The following is calculated: virtual load spring stiffness coefficient k ｍｄ and virtual load viscous damping coefficient c ｍｄ This is pre-configured.

[0153] As the manual steering command value calculation unit 82, for example, a configuration similar to the manual steering command value generation unit (52) shown in Figure 2 of International Publication No. 2023 / 286169 (Patent Document 2) can be used. In that case, the manual steering command value calculation unit 82 solves the differential equation (20) below to obtain the manual steering command value θ ＭＤ Perform the calculation.

[0154] J ２ d ２ θ ＭＤ / dt ２ = T ｔｂ +T ａｓ -k ｍｄ θ ＭＤ -c ｍ (dθ ＭＤ / dt) ... (20)

[0155] The angle addition unit 83 adds the automatic steering command value θ. ＡＤ Manual steering command value θ ＭＤ By adding this, the integrated angle command value θ ｉｃｍｄａ Perform the calculation.

[0156] The low-pass filter 51 uses an integrated angle command value θ. ｉｃｍｄａ A low-pass filter is applied to this value. The integrated angle command value θ after low-pass filtering is then applied. ｉｃｍｄ This is supplied to the feedback control unit 71B and the feedforward control unit 72B.

[0157] Integrated angle command value θ ｉｃｍｄａAlternatively, the integrated angle command value θ after low-pass filtering. ｉｃｍｄ This is an example of a “target steering angle” in this disclosure.

[0158] The feedback control unit 71B includes an angle deviation calculation unit 76B and a PD control unit 77B. The angle deviation calculation unit 76B calculates the integrated angle command value θ ｉｃｍｄ and the steering angle estimate ^θ given by the disturbance observer 74A ｐ The deviation θ ｄｉｆｆ (=θ) ｉｃｍｄ -θ ｐ ) is calculated.

[0159] The PD control unit 77B processes the angular deviation θ calculated by the angular deviation calculation unit 76B. ｄｉｆｆ By performing a PD calculation (proportional-derivative calculation) on it, the feedback control torque T ｆｂ The following calculation is performed. The input / output characteristics of the PD control unit 77B are the same as those of the PD control unit 77A in the first modified example, and are represented by equation (15).

[0160] The feedforward control unit 72B includes an angular acceleration calculation unit 78B and an inertia multiplication unit 79B. The angular acceleration calculation unit 78B calculates the integrated angular command value θ. ｉｃｍｄ By taking the second derivative of the target angular acceleration d, ２ θ ｉｃｍｄ / dt ２ Perform the calculation.

[0161] The inertia multiplication unit 79B calculates the target angular acceleration d calculated by the angular acceleration calculation unit 78B. ２ θ ｉｃｍｄ / dt ２ To the target apparent inertia J ｉｄｅａｌ By multiplying by this, the feedforward controlled torque T ｆｆ (=J ｉｄｅａｌ d ２ θ ｉｃｍｄ / dt ２ ) is calculated. Feedforward controlled torque T ｆｆ This is provided to the torque addition unit 73 as an inertia compensation value.

[0162] The torque addition unit 73 controls the feedback-controlled torque T ｆｂ Feedforward controlled torque T ｆｆBy adding this, the basic torque command value (T ｆｂ +T ｆｆ ) is calculated.

[0163] The disturbance torque compensation unit 75 controls the basic torque command value (T ｆｂ +T ｆｆ ) From there, the disturbance torque^T given by the disturbance observer 74A. ｌｃ By subtracting this, the output shaft torque command value (T) is obtained, which is the torque command value for the output shaft 11. ｆｂ +T ｆｆ -^T ｌｃ The following calculation is performed. The transfer function of the disturbance observer 74A is the same as the transfer function of the disturbance observer 74A in the first modified example, and is expressed by equation (16).

[0164] The inertia correction unit 59A, like the inertia correction unit 59A of the first modified example, is composed of a second-order differential processing unit 60, an inertia difference multiplication unit 61, and a subtraction unit 62A. The second-order differential processing unit 60 is composed of the actual steering angle θ ｐ By taking the second derivative of this, we obtain the actual steering angular acceleration d ２ θ ｐ / dt ２ Perform the calculation.

[0165] The inertia difference multiplication unit 61 calculates the actual steering angle acceleration d ２ θ ｐ / dt ２ To the target apparent inertia J ｉｄｅａｌ and the actual second inertia J ２ The difference with (J ｉｄｅａｌ -J ２ Multiply by ). Target apparent inertia J ｉｄｅａｌ This is the target value of the apparent inertia as seen from the disturbance torque compensation unit 75, similar to the first modified example.

[0166] For the sake of explanation, the output of the disturbance torque compensation unit 75 is set to T, similar to the first modified example. ｐ３，ｃｍｄ This is expressed as follows, and the output of the inertia correction unit 59A is set to T in the same manner as in the first modified example. ｐ４，ｃｍｄ We will represent it as follows.

[0167] The first reduction ratio division unit 53 receives the output T of the inertia correction unit 59A. ｐ４，ｃｍｄ By dividing this by the reduction ratio N of the reduction gear 23, the motor torque command value T, which is the torque command value for the electric motor 22, is obtained.ｍ，ｃｍｄ The torque control unit 54 calculates the motor torque of the electric motor when it is equal to the motor torque command value T. ｍ , ｃｍｄ The drive circuit 41 is driven to approach it.

[0168] In this second modified example, the output T of the disturbance torque compensation unit 75 is also ｐ３，ｃｍｄ This is expressed by equation (19) above. In other words, when viewed from the disturbance torque compensation unit 75, the inertia of the plant is the target apparent inertia J ｉｄｅａｌ This is the result.

[0169] This results in the apparent time constant τ ｉｄｅａｌ Since it is represented by the above equation (12), the second inertia J ２ is the first inertia J １ Even in extremely small power steering systems, it becomes possible to implement the electric motor control system using software.

[0170] Furthermore, in the second modified example, the automatic steering command value θ ＡＤ Manual steering command value θ ＭＤ When added, the integrated angle command value θ ｉｃｍｄ The calculation is performed, and the integrated angle command value θ is calculated. ｉｃｍｄ Since the electric motor 22 is controlled based on this, coordinated control of automatic steering and manual steering becomes possible.

[0171] In the motor control ECU 102A according to the first modified example and the motor control ECU 102B according to the second modified example described above, a disturbance observer 74A and a disturbance torque compensation unit 75 are provided, but the disturbance observer 74A and the disturbance torque compensation unit 75 may not be provided. In this case, the angle deviation calculation unit 76 in Figure 5 calculates the output θ of the low-pass filter 51. ｃｍｄ From the actual steering angle θ ｐ By subtracting the angular deviation θ, ｄｉｆｆ The angle deviation calculation unit 76 in Figure 7 calculates the output θ of the low-pass filter 51. ｉｃｍｄ From the actual steering angle θ ｐ By subtracting the angular deviation θ, ｄｉｆｆ The calculation is performed. In this case, the target value of apparent inertia as seen from the torque addition unit 73 is the target apparent inertia J. ｉｄｅａｌ It will be set as follows.

[0172] Furthermore, in the motor control ECU 102A according to the first modified example and the motor control ECU 102B according to the second modified example, feedforward control units 72A and 72B are provided, but the feedforward control units 72A and 72B do not necessarily have to be provided. In this case, the basic torque command value is the feedback control torque T ｆｂ This is the result.

[0173] In the embodiments, first and second modifications described above, the electric motor 22 is connected to the output shaft 11 via a reduction gear 23, but the electric motor 22 may be connected to the output shaft 11 without a reduction gear. As a structure in which the electric motor 22 is connected to the output shaft 11 without a reduction gear, for example, a structure in which the rotor of the electric motor 22 is fixed to the output shaft 11 can be used.

[0174] In the embodiments, first and second modifications described above, the power steering system is provided with an electric power steering mechanism 9 and a hydraulic power steering mechanism 7. However, this disclosure can also be applied to steering systems that are provided with an electric power steering mechanism (electric power steering device) 9 but not a hydraulic power steering mechanism.

[0175] The motor control devices of this disclosure (for example, motor control ECUs 102, 102A, 102B) can also be applied to the control devices of the electric motor 418 of the column-type electric power steering system 401 described in the "Problems to be Solved by the Invention" section.

[0176] Furthermore, the motor control devices of this disclosure (for example, motor control ECUs 102, 102A, and 102B) can also be applied to the control devices of electric motors in a dual-pinion type power steering system as shown in Figure 8.

[0177] The dual-pinion power steering system 301 includes a steering wheel 302, a steering mechanism 304 that steers the steering wheels 303 in conjunction with the rotation of the steering wheel 2, and a steering assist mechanism 305.

[0178] The steering wheel 302 and the steering mechanism 304 are mechanically connected via the steering shaft 306 and the intermediate shaft 307.

[0179] The steering mechanism 304 consists of a rack and pinion mechanism including a first pinion shaft 308 and a rack shaft 309 as the steering shaft. Steering wheels 303 are connected to each end of the rack shaft 309 via tie rods 310 and knuckle arms (not shown).

[0180] The first pinion shaft 308 includes a pinion input shaft 311 connected to an intermediate shaft 307, an output shaft 313 to which the first pinion 314 is connected, and a torsion bar (torsion bar for electric power steering device) 312 connecting the pinion input shaft 311 and the pinion output shaft 313. A torque sensor 315 is provided around the first pinion shaft 308.

[0181] A first rack 316 that meshes with the first pinion 314 is formed on the first axial end side of the rack shaft 309.

[0182] The steering assist mechanism 305 includes an electric motor 317, a reduction gear 318, a second pinion shaft 319, a second pinion 320, and a second rack 321. The reduction gear 318 consists of a worm gear mechanism including a worm shaft (not shown) rotatably connected integrally to the output shaft of the electric motor 317, and a worm wheel (not shown) that meshes with the worm shaft and is rotatably connected integrally to the second pinion shaft 319. The second pinion 320 is connected to the tip of the second pinion shaft 319. The second rack 321 is formed on the second axial end side of the rack shaft 309. The second pinion 320 meshes with the second rack 321.

[0183] In the dual-pinion type power steering system 301 shown in Figure 8, the first inertia J １ This is expressed by the following equation (21).

[0184] J １= [Inertia obtained by converting the inertia of the steering wheel 302 into the rotational inertia of the pinion input shaft 311 (equivalent inertia of the steering wheel's pinion axis)] + [Inertia obtained by converting the inertia of the steering shaft 306 into the rotational inertia of the pinion input shaft 311 (equivalent inertia of the steering shaft's pinion axis)] + [Inertia obtained by converting the inertia of the intermediate shaft 307 into the rotational inertia of the pinion input shaft 311 (equivalent inertia of the intermediate shaft's pinion axis)] + [Inertia of the pinion input shaft 311] ... (21)

[0185] However, if the inertia of the pinion input shaft 311 is smaller than the equivalent inertia of the steering wheel's pinion axis + the equivalent inertia of the steering shaft's pinion axis + the equivalent inertia of the intermediate shaft's pinion axis, then the equivalent inertia of the steering wheel's pinion axis + the equivalent inertia of the steering shaft's pinion axis + the equivalent inertia of the intermediate shaft's pinion axis is set to the first inertia J. １ It can be considered as such.

[0186] In the dual-pinion type power steering system 301 shown in Figure 8, the second inertia J ２ This is expressed by the following equation (22).

[0187] J ２ = J ｐ +J ｍｏｔｏｒ ・N1 ２ +J ｒａｃｋ (22) J ｐ Inertia of pinion output shaft 313 J ｍｏｔｏｒ ・N1 ２ : Inertia obtained by converting the inertia of the motor shaft into the rotational inertia of the first pinion output shaft 313 (equivalent inertia of the motor shaft to the pinion shaft) J ｍｏｔｏｒ : Motor shaft inertia N1: Reduction ratio of pinion output shaft 313 as seen from the motor shaft (ratio of motor shaft rotation speed to rotation speed of first pinion output shaft 313) J ｒａｃｋ : The inertia obtained by converting the mass of the rack axis into the rotational inertia of the first pinion output shaft 313 (equivalent inertia of the rack axis to the pinion axis)

[0188] J ｐ ga [J ｍｏｔｏｒ ・N1 ２ +J ｒａｃｋ If it is smaller than [J ｍｏｔｏｒ ・N1２ +J ｒａｃｋ as the second inertia J ２ can also be regarded as such.

[0189] In addition, as disclosed in Japanese Patent Application Laid-Open No. 2000-86868, the motor control device of the present disclosure can also be applied to the motor of the rack parallel type power steering system in which the motor shaft of the electric motor 317 in FIG. 8 described above is connected to the rack shaft 309 via a plurality of gears and a ball screw mechanism. The first inertia J １ and the second inertia J ２ in such a rack parallel type power steering system are respectively the first inertia J １ and the second inertia J ２ in the dual pinion type power steering system 301 described above, and are the same.

[0190] In addition, the present disclosure can be variously designed within the scope of the matters described in the claims.

[0191] 1... Steering system, 2... Steering wheel, 9... Electric power steering mechanism, 10... Input shaft, 11... Output shaft, 12... Torsion bar, 22... Electric motor, 51... Low-pass filter (LPF), 52, 71, 71A, 71B... Feedback control unit, 54... Torque control unit, 72, 72A, 72B... Feedforward control unit, 74, 74A... Disturbance observer, 73... Torque addition unit, 75... Disturbance torque compensation unit, 59, 59A... Inertia correction unit, 60... Angular acceleration calculation unit, 61... Inertia difference multiplication unit, 62, 62A... Subtraction unit, 101... ECU for automatic control, 102, 102A, 102B... ECU for motor control

Claims

1. A motor control device for an electric power steering device in a power transmission path between a steering wheel and a steering wheel, wherein a torsion bar for an electric power steering device is present in the power transmission path between the steering wheel and the steering wheel, comprising: a first control unit that calculates a first torque command value by performing control on the target steering angle to bring the actual steering angle or an estimated actual steering angle closer to the target steering angle; an inertia correction unit that calculates a second torque command value by performing processing on the first torque command value to make the apparent second inertia as seen from the first control unit greater than the actual second inertia, with the inertia of one inertia system located on the opposite side of the torsion bar from the steering wheel and connected to the torsion bar being the first inertia, and the inertia of one inertia connected to the first inertia via the torsion bar and rotating relative to the motor shaft of the electric motor being the second inertia; and a second control unit that controls the electric motor based on the second torque command value.

2. The motor control device according to claim 1, wherein the inertia correction unit includes: an angular acceleration calculation unit that calculates the actual rudder angular acceleration by taking the second derivative of the actual rudder angle; an inertia difference multiplication unit that multiplies the actual rudder angular acceleration by the difference between the target apparent inertia and the actual second inertia; and a subtraction unit that calculates the second torque command value by subtracting the multiplication result of the inertia difference multiplication unit from the first torque command value.

3. The first inertia is J １ Therefore, the target apparent inertia is 0.7 × J １ The motor control device according to claim 1.

4. The first inertia is J １ Therefore, the target apparent inertia is 0.7 × J １ The above is 1.3 × J １ The motor control device according to claim 1, which is as follows:

5. The motor control device according to any one of claims 1 to 4, wherein the first control unit includes a feedback control unit for bringing the actual steering angle or the estimated actual steering angle closer to the target steering angle, a feedforward control unit for inertia compensation, and a torque addition unit for adding a feedback control torque calculated by the feedback control unit and a feedforward control torque calculated by the feedforward control unit, the feedforward control unit calculates the feedforward control torque by multiplying the second derivative of the target steering angle by the target apparent inertia.

6. The motor control device according to claim 5, further comprising a disturbance torque estimation unit that estimates disturbance torques other than the motor torque of the electric motor acting on an object driven by the electric motor, wherein the first control unit further comprises a disturbance compensation unit that subtracts the disturbance torque estimated by the disturbance torque estimation unit from the calculation result of the torque addition unit.

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