Steering control device

Abstract

To provide a steering control device which prevents rattle sound due to generation of pulse noise even when a gradient change is large at a map break point between an estimated load torque and a target steering torque.SOLUTION: A servo controller 400 calculates a base assist command Tb* as a basic instruction value of an assist torque so that a steering torque Ts follows a target steering torque Ts*. An estimated load torque calculation part 20 calculates an estimated load torque Tx. A target steering torque calculation part 30 calculates the target steering torque Ts* using a map 33 specifying a relation between the estimated load torque Tx and the target steering torque Ts*. An estimated load torque calculation part 30 calculates the estimated load torque Tx on the basis of the steering torque Ts or the target steering torque Ts*, and an assist instruction Tbx* for estimated load calculation corresponding to a calculation result of only proportional integration control calculation out of control calculation in the servo controller 400.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a steering control device. [Background technology]

[0002] Conventionally, in a steering device that controls the assist torque output by a motor, a technology is known in which a target steering torque is calculated based on an estimated load torque, and a base assist command is calculated by a servo controller so that the steering torque follows the target steering torque.

[0003] For example, in the steering control device disclosed in Patent Document 1, a target generating unit generates a target steering torque (Ts * ) and base assist command (Tb * ) to calculate an estimated load torque (road surface reaction force in Patent Document 1). The torque converter of the target generation unit calculates the target steering torque using a map that specifies the value of the target steering torque with respect to the estimated load torque.

[0004] Moreover, in the steering control device disclosed in Patent Document 2, a servo controller (assist controller in Patent Document 2) generates a base assist command by PID control so that the steering torque follows a target steering torque. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6314752 [Patent Document 2] Patent No. 6252027 Summary of the Invention [Problem to be solved by the invention]

[0006] The target steering torque is calculated by an interpolation calculation using a map. When the estimated load torque, which is the map input, changes during steering, the output change relative to the input change is constant within the interpolation section, but when passing through the bending point of the map, the gradient changes, causing a sudden change in the time rate of change of the output.

[0007] For example, when a map is adapted to obtain a steering feel or a desired behavior, the gradient change at the map break point may be large, especially in the small signal region where the estimated load torque is close to 0. If the gradient change at the map break point is large, the differential calculation output of the servo controller changes when passing through that point, and as a result, the base assist command changes. Then, pulse noise is generated in the process of calculating the target steering torque for the next calculation cycle using the fed-back base assist command, which may vibrate the motor and cause a rattle noise.

[0008] The present invention was created in consideration of these points, and its purpose is to provide a steering control device that prevents rattle noise caused by the generation of pulse noise even if there is a large change in gradient at the map break point between the estimated load torque and the target steering torque. [Means for solving the problem]

[0009] The present invention provides a steering control device that controls an assist torque output by a motor (80) connected to a steering system mechanism (100) that generates a steering torque (Ts), and includes a servo controller (400, 40B), an estimated load torque calculation unit (20), and a target steering torque calculation unit (30).

[0010] The servo controller calculates the steering torque based on the target steering torque (Ts * ) to make the assist torque follow the base assist command (Tb * ) is calculated.

[0011] The estimated load torque calculation unit calculates an estimated load torque (Tx), which is a load torque that acts on a steering shaft (95) of a steering system mechanism and changes according to steering. The target steering torque calculation unit calculates a target steering torque (Ts * ) is calculated.

[0012] The estimated load torque calculation unit calculates the steering torque or the target steering torque and the estimated load calculation assist command (Tbx * ) and calculate the estimated load torque based on this.

[0013] As a result, in the present invention, even if the gradient change at the map break point is large, especially in the small signal region, a steep pulse is not superimposed on the base assist command. Therefore, steering vibration such as rattle noise can be prevented, and smooth operation with low vibration can be obtained. This increases the degree of freedom in adaptation. In addition, the low-pass filter of the estimated load torque calculation section can be changed from a secondary filter to a primary filter, simplifying the calculation process. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram of an electric power steering system. [Diagram 2] 1 is a schematic configuration diagram of an ECU (steering control device) according to a first embodiment. [Diagram 3] FIG. 13 is an enlarged view of a small signal region of the estimated load torque-target steering torque map. [Figure 4] 1A to 1C are diagrams for explaining the principle of occurrence of a problem phenomenon in map calculation. [Diagram 5] A time chart supplementing Figure 4. [Figure 6] FIG. 2 is a block diagram of a servo controller according to the first embodiment. [Figure 7] 4 is a time chart showing the behavior of an actual vehicle in a comparative example (normal PID control). [Figure 8] 4 is a time chart showing the behavior of an actual vehicle according to the present embodiment; [Figure 9] FIG. 11 is a schematic configuration diagram of an ECU (steering control device) according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, multiple embodiments of the steering control device of the present invention will be described with reference to the drawings. An ECU as a "steering control device" is applied to an electric power steering system or a steer-by-wire system of a vehicle, and calculates an output command for a motor. In the following embodiments, an example in which the steering control device is mainly applied to an electric power steering system is shown. In the electric power steering system, the steering control device outputs an assist torque command to a steering assist motor. The following first and second embodiments are collectively referred to as "the present embodiment."

[0016] [Electric power steering system configuration] The configuration of the electric power steering system will be described with reference to FIG. 1. The assist torque Ta and the base assist command Tb * For symbols, see Fig. 2. The electric power steering system 1 is a system that assists the driver in operating a steering wheel 91 by using the driving torque of a motor 80. The steering wheel 91 is fixed to one end of a steering shaft 92, and an intermediate shaft 93 is provided on the other end of the steering shaft 92. The steering shaft 92 and the intermediate shaft 93 are connected by a torsion bar of a torque sensor 94, and these form a steering shaft 95. The torque sensor 94 detects the steering torque Ts based on the torsion angle of the torsion bar.

[0017] A gear box 96 including a pinion gear 961 and a rack 962 is provided on the end of the intermediate shaft 93 opposite to the torque sensor 94. When the driver turns the steering wheel 91, the pinion gear 961 rotates together with the intermediate shaft 93, and the rack 962 moves left and right in accordance with the rotation of the pinion gear 961. Tie rods 97 provided on both ends of the rack 962 are connected to tires 99 via knuckle arms 98. The tie rods 97 reciprocate left and right, pulling and pushing the knuckle arms 98, thereby changing the orientation of the tires 99.

[0018] The motor 80 is, for example, a three-phase AC brushless motor, and outputs an assist torque Ta that assists the steering force of the steering wheel 91 in response to a drive voltage Vd output from the ECU 10. In the case of a three-phase AC motor, the drive voltage Vd means the voltage of each of the U-phase, V-phase, and W-phase. The rotation of the motor 80 is transmitted to an intermediate shaft 93 via a reduction mechanism 85 constituted by a worm gear 86, a worm wheel 87, and the like. In addition, the rotation of the intermediate shaft 93 caused by the steering of the steering wheel 91 or a reaction force from the road surface is transmitted to the motor 80 via the reduction mechanism 85.

[0019] 1 is a column assist type in which the rotation of the motor 80 is transmitted to the steering shaft 95, but the ECU 10 of this embodiment is similarly applicable to a rack assist type electric power steering system. In other embodiments, a polyphase AC motor other than a three-phase motor or a brushed DC motor may be used as the steering assist motor.

[0020] Here, the entire mechanism through which the steering force of the steering wheel 91 is transmitted from the steering wheel 91 to the tires 99 is referred to as the "steering system mechanism 100." The ECU 10 controls the assist torque Ta output by the motor 80 connected to the steering system mechanism 100, thereby controlling the steering torque Ts generated by the steering system mechanism 100. The ECU 10 also acquires the vehicle speed V detected by a vehicle speed sensor 11 provided at a predetermined location on the vehicle.

[0021] The ECU 10 operates on power from an on-board battery (not shown) and generates a base assist command Tb, which is a basic command value of the assist torque, based on the steering torque Ts detected by the torque sensor 94 and the vehicle speed V detected by the vehicle speed sensor 11. * In this embodiment, the base assist command Tb * No correction torque is added to the base assist command Tb * is output as it is as a command value for the assist torque Ta.

[0022] Base assist command Tb * The drive voltage Vd calculated based on this is applied to the motor 80, causing the motor 80 to output the assist torque Ta, and causing the steering mechanism 100 to generate a steering torque Ts. Note that the various calculation processes in the ECU 10 may be software processes in which a CPU executes a program pre-stored in a physical memory device such as a ROM, or may be hardware processes in which a dedicated electronic circuit is used.

[0023] [ECU configuration] (First embodiment) The configuration of the ECU 10 of the first embodiment will be described with reference to Fig. 2. The ECU 10 includes an estimated load torque calculation unit 20, a target steering torque calculation unit 30, a deviation calculator 39, a servo controller 400, and a current feedback ("FB" in the figure) unit 70.

[0024] The estimated load torque calculation unit 20 calculates the target steering torque Ts * and estimated load calculation assist command Tbx * In other words, in the configuration of FIG. 3 of Patent Document 1, the base assist command Tb * Instead of the estimated load calculation assist command Tbx *The estimated load torque Tx is a load torque that acts on the steering shaft 95 of the steering system mechanism 100 and changes in response to steering. The positive and negative values ​​of the estimated load torque Tx and the steering torque Ts are defined according to the rotation direction of the steering shaft 95 such that the torque in one rotation direction is positive and the torque in the opposite direction is negative.

[0025] The estimated load torque calculation unit 20 includes an adder 21 and a low-pass filter ("LPF" in the figure) 22. The adder 21 receives an estimated load calculation assist command Tbx fed back from the servo controller 400. * and the target steering torque Ts fed back from the target steering torque calculation unit 30. * Add the above. Estimated load calculation assist command Tbx * corresponds to the calculation result of only the proportional-integral control calculation among the control calculations in the servo controller 400, that is, the calculation result that does not include the differential control calculation. * This will be described in detail later with reference to FIG.

[0026] The low-pass filter 22 extracts a predetermined frequency component, for example a band of 10 Hz or less, from the added torque. The estimated load torque calculation unit 20 outputs the frequency component extracted by the low-pass filter 22 as the estimated load torque Tx.

[0027] The target steering torque calculation unit 30 calculates the estimated load torque Tx and the target steering torque Ts * Using the map 33 in which the relationship between the target steering torque Ts * The target steering torque calculation unit 30 includes a sign determination unit ("sgn" in the figure) 31, an absolute value determination unit ("|u|" in the figure) 32, a map 33, and a multiplier 34. The sign determination unit 31 determines whether the estimated load torque Tx is positive or negative, i.e., the sign according to the rotation direction of the steering shaft 95. The absolute value determination unit 32 calculates the input u, i.e., the absolute value of the estimated load torque Tx.

[0028] The map 33 is shown as a map in the positive region of the estimated load torque Tx, that is, as a map of the absolute value. In the negative region of the estimated load torque Tx, the map is symmetrical with respect to the origin with respect to the positive region. * has a positive correlation with the estimated load torque Tx, and increases logarithmically as the estimated load torque Tx increases.

[0029] Specifically, the map 33 is a graph showing the target steering torque Ts for a specific value of the estimated load torque Tx for each vehicle speed V. * The target steering torque Ts for any estimated load torque Tx is expressed by a broken line connecting multiple points indicating the value of * is obtained by an interpolation calculation of the map 33. The higher the vehicle speed V, the lower the target steering torque Ts for the same estimated load torque Tx. * The range of the estimated load torque Tx, which is the horizontal axis of the map 33, is about 0 to 30 [Nm], and the range of the target steering torque Ts * The range is approximately 0 to 6 [Nm].

[0030] FIG. 3 shows an enlarged view of the small signal region where the estimated load torque Tx is close to 0 in the map 33 in FIG. 2. This map 33 is adapted in the small signal region to obtain a steering feel and a desired behavior. As a result of the adaptation, at the turning point of the estimated load torque Tx of 0.3 [Nm], the target steering torque Ts * The rate of change of the target steering torque Ts is increasing, and the bend is large. At other bends, the second-order differential value is negative, whereas at this bend, the second-order differential value is positive. Also, at the bend where the estimated load torque Tx is 1 [Nm], the target steering torque Ts * The rate of change of the curve suddenly decreases, and the curve is large. The influence of the large curve at the break point will be described later with reference to Figs. 4 and 5.

[0031] Returning to FIG. 2, the target steering torque Ts calculated based on the absolute value of the estimated load torque Tx is * The absolute value of the target steering torque Ts outputted from the target steering torque calculation unit 30 is multiplied by a sign corresponding to the sign of the estimated load torque Tx in a multiplier 34. *is input to the deviation calculator 39 and is also fed back to the estimated load torque calculation section 20.

[0032] The deviation calculator 39 calculates the target steering torque Ts * and the steering torque Ts, which is the steering torque deviation ΔT (=Ts * The steering torque deviation ΔT is input to the servo controller 400. The servo controller 400 calculates the steering torque Ts as a target steering torque Ts * The base assist command Tb * A detailed configuration of the servo controller 400 of this embodiment will be described later with reference to FIG.

[0033] The current feedback unit 70 outputs the base assist command Tb * A drive voltage Vd is applied to the motor 80 so that an assist torque corresponding to the current is applied to the steering shaft 95, which is closer to the tire 99 than the torque sensor 94. The current feedback control technology is well known in the field of motor control, and therefore a detailed description thereof will be omitted.

[0034] Next, the principle of occurrence of the problem phenomenon in the map calculation of the target steering torque calculation unit 30 will be described with reference to Fig. 4 and Fig. 5. * As shown by the dashed arrow, the estimated load torque Tx increases monotonically and the operating point on the map moves from point A to point B. Here, the base assist command Tb * is fed back to the estimated load torque calculation unit 20.

[0035] If the estimated load torque Tx increases linearly, the target steering torque Ts * , and the differential of the target steering torque D(Ts * ) changes as shown in the time waveform in FIG. 5. In this case, the differential D(Ts * ), that is, the gradient change of the map is a step change rather than a pulse change. However, the base assist command Tb *When a closed loop is formed in which the load torque is fed back to the estimated load torque calculation unit 20, the following phenomenon occurs.

[0036] When the estimated load torque Tx changes from time n to the next time (n+1) in FIG. 4, the signal that has passed through the servo controller 400 mainly undergoes a relatively large step change in the differential control component. At this time, when the estimated load torque Tx increases, the steering torque deviation ΔT increases and the steering torque deviation differential D(ΔT) becomes positive. Also, since the differential gain Kd in the PID control equation is negative as described later, the base assist command Tb * is on the decline.

[0037] Then, at the next time (n+2), the reduced base assist command Tb * The estimated load torque Tx calculated based on the estimated load torque Tx is reduced. * is smaller than the previous value at time (n+1). Therefore, the differential D(Ts * The derivative of Tb changes the step change in the previous direction, resulting in a pulse. This is the base assist command Tb * This appears as pulse noise.

[0038] In this way, when the gradient change at the map breakpoint is large, especially in the small signal region, the base assist command Tb * The motor 80 may be vibrated by pulse noise appearing in the map, which may cause rattle noise. Here, it is possible that the noise vibration may be eliminated by adapting the map so that the map has a high score and changes smoothly. However, it is necessary to repeat adaptation and noise vibration evaluation through trial and error, which imposes restrictions on the adaptation. Therefore, in this embodiment, the estimated load torque Tx and the target steering torque Ts * To prevent rattle noise caused by pulse noise even if the gradient change at the map break point is large.

[0039] The configuration of a servo controller 400 according to a first embodiment for solving this problem is shown in Fig. 6. The servo controller 400 includes a proportional-integral control calculation unit 420, a differential control calculation unit 50, a final adder 58, and a final limit calculation unit 59. Fig. 6 shows a configuration in which the servo control calculation is equivalently converted into a discrete equation. The servo controller 400 according to the first embodiment calculates an estimated load calculation assist command Tbx by a proportional-integral control calculation. * The calculation result by the differential control calculation and the estimated load calculation assist command Tbx * Adding this, the base assist command Tb * In other words, the estimated load calculation assist command Tbx * and base assist command Tb * Both are calculated at the same time.

[0040] The proportional and integral control calculation unit 420 includes a proportional control calculation unit 430, an integral control calculation unit 440, an adder 48, and an accumulation calculation unit 490. The proportional control calculation unit 430 and the integral control calculation unit 440 perform proportional and integral control calculations based on the steering torque deviation ΔT, similar to the configuration of the assist controller disclosed in FIG. 4 of Patent Document 2.

[0041] The delay element 45 extracts the previous value of the steering torque deviation ΔT. In the proportional control calculation unit 430, the steering torque deviation ΔT from which the previous value has been subtracted in the subtractor 463 is multiplied by a proportional gain Kp in the gain multiplier 473. In the integral control calculation unit 440, the steering torque deviation ΔT from which the previous value has been added in the adder 464 is multiplied by an integral gain Ki in the gain multiplier 474.

[0042] The adder 48 outputs the target torque TM obtained by adding the proportional control and integral control components for each control period. Here, the proportional control amount alone is insufficient as an estimated load, and the integral control amount alone cannot be used because of a large delay with respect to the road surface reaction force. The accumulation processing unit 490 accumulates the target torque TM and outputs the current value Tbx of the assist command for calculating the estimated load. * nAccumulation processing is synonymous with integral processing, but the term "accumulation" is used here to distinguish it from integral control. Although there are differences depending on the calculation configuration of the proportional-integral control calculation unit, the point is that a proportional-integral controlled signal is output.

[0043] The accumulation processing unit 490 includes an adder 491, a delay element 492, and a limiting calculator 494. The adder 491 multiplies the current value of the torque TM to be processed by the previous value Tbx of the assist command for calculating the estimated load, which is input via the delay element 492. * n-1 The limiting calculator 494 limits the sum of the adder 491 to a limiting value that can be output as an assist torque. This addresses the wind-up problem, that is, the phenomenon in which, when a deviation continues to occur, a value larger than the allowable output is taken by integration, and then when the sign of the deviation reverses, the reduction in output is delayed.

[0044] The differential control calculation unit 50 includes a pseudo differential calculation unit 54 and a gain multiplier 57. The pseudo differential calculation unit 54 calculates the steering torque deviation differential D(ΔT) by pseudo differentiation. The pseudo differential "D" of the discrete value is expressed as (s / (τs+1)) in terms of a transfer function of the continuous system. 2 ) (where s is a Laplace operator, and τ is a time constant). In the gain multiplier 57, the steering torque deviation differential D(ΔT) is multiplied by a differential gain Kd.

[0045] The final adder 58 calculates the current value Tbx of the assist command for the estimated load calculation. * n The current value Kd·D(ΔT) of the output of the differential control calculation unit 50 n The final limit calculator 59 limits the sum of the final adder 58 in the same manner as the limit calculator 494. This limit is not related to windup, but corresponds to the limit during overheat protection and fail-safe.

[0046] The servo control formula is shown below. The steering torque deviation ΔT is expressed by formula (1). ΔT=Ts * -Ts···(1)

[0047] Base assist command Tb * is expressed by the formula (2). In the configuration of Fig. 6, the proportional gain Kp, the integral gain Ki, and the differential gain Kd are all set to negative values.

[0048]

number

[0049] In order to discretize equation (2), the bilinear transformation equation expressed by equation (3) is substituted into equation (2) and rearranged to obtain equations (4.1) and (4.2). In equation (3), ts indicates the calculation period. In Figure 6, (ts / 2)Ki is collectively written as "Ki".

[0050]

number

[0051] As described above, in this embodiment, the servo controller 400 outputs the estimated load calculation assist command Tbx, which does not include a differential control component, to the estimated load torque calculation unit 20. * Therefore, the target steering torque Ts * The step change due to the gradient change of the base assist command Tb * is fed back. Therefore, the step change is less likely to circulate in the closed loop and is less likely to appear as pulse noise. Therefore, vibration of the motor 80 is suppressed.

[0052] In addition, the base assist command Tb * When is fed back, the low-pass filter 22 of the estimated load torque calculation section 20 is a secondary filter for removing high frequency components of servo control, but since it does not contain a differential control component, a primary filter can be used, and the calculation process is simplified.

[0053] Next, referring to the time charts of Figures 7 and 8, the actual vehicle behavior when the steering wheel is turned left or right so that the steering torque Ts changes from positive to negative and from negative to positive in the comparative example and this embodiment will be described. In the comparative example, the base assist command Tb * is fed back. The discrete equation for normal PID control is shown in equation (5).

[0054]

number

[0055] 7 and 8 show, from top to bottom, the steering angular velocity ω, the steering torque Ts, and the target steering torque Ts * , steering torque deviation differential D(ΔT), and base assist command Tb * Furthermore, in this embodiment, the estimated load calculation assist command Tbx * Shows.

[0056] In the comparative example shown in FIG. 7, the target steering torque Ts * When the target steering torque Ts passes through the bending point of the map (Fig. 3) in the small signal region near 0, * At this time, the differential control component in the fourth term of equation (5) changes stepwise. The stepwise change is the base assist command Tb * This is also reflected in the

[0057] This base assist command Tb * When the load torque is fed back to the estimated load torque calculation unit 20, the target steering torque Ts * As a result, the target steering torque Ts * As shown in (*1) and (*2), the steering torque deviation differential D(ΔT) and the base assist command Tb * This results in a pulse-like vibration of the motor 80.

[0058] The effect of the excitation by the pulse current also affects the steering angular velocity ω converted from the motor rotation angle, and as shown in (*3), the waveform fluctuates. In addition, when focusing on the direction of the excitation, it is opposite to the direction in which the motor 80 is intended to rotate. Therefore, it acts in the opposite direction by passing through the gear backlash and play, which tends to cause rattle noise.

[0059] In this embodiment shown in FIG. 8, the target steering torque Ts * When the map passes the bending point, the target steering torque Ts * Even if the change in the estimated load calculation assist command Tbx * Since does not include a differential control component, the step change is small.

[0060] Therefore, the estimated load calculation assist command Tbx obtained by accumulating the formula (4.1) * The estimated load calculation assist command Tbx is free of pulse noise. * The target steering torque Ts is calculated based on the estimated load torque Tx. * The base assist command Tb is determined in the circulatory system where * As a result, in this embodiment, no rattle noise is generated, and smooth actuator operation with low noise is achieved.

[0061] Second embodiment With reference to Fig. 9, the configuration of the ECU 10x of the second embodiment will be described, mainly focusing on the differences from the first embodiment. The same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. In the ECU 10x of the second embodiment, instead of the servo controller 400 of the first embodiment, a servo controller 40B and a PI controller 40X are provided separately.

[0062] The servo controller 40B calculates a base assist command Tb *The servo controller 40B may have a configuration similar to that shown in FIG. 4 of Patent Document 2. The PI controller 40X calculates the estimated load calculation assist command Tbx by proportional-integral control calculation that does not include a differential control calculation. * Assist command for estimated load calculation Tbx * corresponds to the calculation result of only the proportional-integral control calculation among the control calculations in the servo controller 40B. The configuration of the PI controller 40X is similar to that of the proportional-integral control calculation unit 420 in Fig. 6. Even with such a separate configuration, the same effects as in the first embodiment can be obtained.

[0063] (Other embodiments) (a) The estimated load torque calculation unit 20 calculates the target steering torque Ts * Alternatively, the estimated load torque Tx may be calculated based on the steering torque Ts.

[0064] (b) Target steering torque Ts * is not limited to being calculated based on the estimated load torque Tx, but may be added with a steering torque according to other state quantities such as a steering angle and a steering angular velocity, or may be corrected according to other state quantities. For example, Japanese Patent No. 6387657 discloses a configuration example in which a steering angle reference correction torque is added to the estimated load torque.

[0065] The present invention is not limited to such an embodiment, and can be embodied in various forms without departing from the spirit of the present invention.

[0066] The controller and the method described in the present disclosure may be implemented by a special-purpose computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. Alternatively, the controller and the method described in the present disclosure may be implemented by a special-purpose computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the controller and the method described in the present disclosure may be implemented by one or more special-purpose computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. The computer program may also be stored in a computer-readable non-transitory tangible recording medium as instructions executed by a computer. [Explanation of symbols]

[0067] 10 ECU (steering control unit), 20: Estimated load torque calculation unit, 30 target steering torque calculation unit; 33 map; 400, 40B... Servo controller, 80 Motor, 95···Steering shaft, 100···Steering system mechanism.

Claims

1. A steering control device that controls an assist torque output by a motor (80) connected to a steering mechanism (100) that generates a steering torque (Ts), The steering torque is set to the target steering torque (Ts * ) so that the base assist command (Tb * ) a servo controller (400, 40B) for calculating an estimated load torque calculation unit (20) for calculating an estimated load torque (Tx) which is a load torque acting on a steering shaft (95) of the steering system mechanism and which varies in response to steering; The target steering torque (Ts * a target steering torque calculation unit (30) for calculating a target steering torque; Equipped with The estimated load torque calculation unit The steering torque or the target steering torque, and an estimated load calculation assist command (Tbx * ) and the estimated load torque is calculated based on the result.

2. The servo controller includes:

2. The steering control device according to claim 1, wherein the estimated load calculation assist command is calculated by a proportional-integral control calculation, and the base assist command is calculated by adding a calculation result of a differential control calculation and the estimated load calculation assist command.

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