JP4989093B2 - Electric power steering apparatus and calculation characteristic setting method used therefor. - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the interactive influence of an inertia compensate signal, a damper compensate signal, and a base signal. <P>SOLUTION: A computing characteristic setting method is for an electric power steering device equipped with a base signal computation part 220 to compute the base signal D<SB>T</SB>and a damper compensate signal computation part 225 to compute the damper compensate signal in accordance with the rotating speed of a motor or the steering speed and structured so that the motor is driven with the target signal IM determined by compensating the base signal with the damper compensate signal and the inertia compensate signal so as to give a steering assist force, wherein further an inertia compensate signal computation part 210 is provided to compute the inertia compensate signal on the basis at least of the steering torque, including a step at which the characteristic in computing with the inertia compensate signal computation part is set independently of the base signal computation part and the damper compensate signal computation part. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to an electric power steering apparatus that controls a motor by a target signal determined according to a damper compensation signal, an inertia compensation signal, and a base signal, and a calculation characteristic setting method used therefor.

In the electric power steering apparatus, the electric motor generates an auxiliary torque corresponding to the magnitude of the steering torque, and transmits the auxiliary torque to the steering system to reduce the steering force that the driver steers. A technique is disclosed in which a base current (assist torque) determined by steering torque and vehicle speed is compensated by inertia (inertia) and damping (viscosity) of a steering system, and the motor is controlled using the compensated current as a target current ( (See Patent Documents 1 and 2).
Note that only the torque sensor output is input to the inertia compensation current value determining means of Patent Document 2, and no vehicle speed signal is input.
JP 2002-59855 A (FIG. 2) Japanese Patent Laid-Open No. 2000-177615 (FIG. 2)

  The characteristics of damping, inertia, and base current described in Patent Document 1 are calculated using an inertia table having a base table, a damper table, and a substantially differential characteristic. Here, a method for setting each table, which is a function of the steering torque, the vehicle speed, and the motor rotation speed, will be considered. The base table lowers the gain as the vehicle speed increases, increases the dead zone, increases the manual steering area to provide the driver with road surface information, and provides a solid steering torque response as the vehicle speed increases. In addition, it is necessary to improve the response delay of the steering due to the inertia (or viscosity) of the electric motor by using the inertia table and to provide a clean steering feeling.

  In addition, the inertia table effectively gives a differential characteristic based on the steering torque, thereby increasing or decreasing the assist of the motor in accordance with the change in the steering torque, that is, the rotational acceleration (steering rotational acceleration) of the motor, and the steering damper. It is necessary to improve the vehicle characteristics by improving the convergence while improving the response of the steering wheel in cooperation with the effect. According to this, when the gain of the inertia table is set to be large, the occurrence of response delay is improved, and a clean steering feeling is obtained. However, since the assist by the electric motor will increase, the feeling of steering torque response will decrease and it will become unreliable steering feeling, or the steering damper effect will decrease, so the response feeling of the steering wheel will decrease and it will not depend There may be a feeling of steering, the steering damper effect is reduced, the convergence of the steering wheel is reduced, and the vehicle characteristics are deteriorated.

  That is, if one of the characteristics of the base current, damping, and inertia is changed, the other two need to be changed as appropriate. As described above, since the characteristics of the base current (base signal), damping (damper compensation signal), and inertia (inertia compensation signal) interfere with each other, it is necessary to adjust the degree of interference by empirically predicting and estimating. is there. In addition, there is a problem that it takes too much development man-hours because it involves the work of balancing the lightness of the steering torque with the inertia and damping of the motor while considering the road surface condition during actual driving.

  Therefore, an object of the present invention is to provide a calculation characteristic setting method and an electric power steering apparatus that can reduce the influence between an inertia compensation signal, a damper compensation signal, and a base signal.

In order to solve the above-described problem, a calculation characteristic setting method according to claim 1 includes a base signal calculation unit (220) that calculates a base signal (Dt) according to at least a torque detection signal Tdet detected by a steering torque sensor; A damper compensation signal calculation unit (225) that calculates a damper compensation signal according to the rotational speed or steering speed of the electric motor (11), and an inertia compensation signal calculation unit (210) that calculates an inertia compensation signal based on at least the steering torque Ts. The electric power steering device (100) for applying a steering assist force by driving the electric motor by a target signal (IM) determined by the damper compensation signal and the inertia compensation signal compensating the base signal. ) In which the evaluation function Ev is set based on the steering torque Ts. Evaluation of when setting the compensator H (S) used in the calculation by the inertia compensation signal computing part, the gain characteristics of the evaluation function Ev, when ignoring the viscosity of inertia coefficient and the steering system around the steering system A step (SP20) for setting the gain characteristic of the function Ev0 or less is provided. The parentheses are examples.

The base signal is calculated according to at least the torque detection signal Tdet detected by the steering torque sensor , and the damper compensation signal is calculated according to the rotation speed or steering speed of the motor. On the other hand, the inertia compensation signal is calculated according to only the steering torque. Therefore, the characteristics calculated by the inertia compensation signal calculation unit can be set independently from the base signal calculation unit and the damper compensation signal calculation unit. Thereby, the characteristic calculated by the base signal calculation part and the characteristic calculated by the damper compensation signal calculation part are easily set. The base signal is often calculated not only according to the steering torque, but the damper compensation signal is calculated not only according to the rotation speed or steering speed of the motor but also according to the vehicle speed.

  Further, the inertia characteristic of the inertia compensation signal calculation unit is obtained on a desk by, for example, evaluating the moment of inertia of the steering system using the ratio Ev of the reaction torque to the input torque as an evaluation function and applying H∞ control. Further, the inertia characteristics required by the H∞ control can be reduced by reducing the order of the compensator by focusing on the frequency band necessary for controlling the steering system, and can be controlled by an existing microcomputer.

According to the second aspect of the present invention, there is provided a base signal calculation unit for calculating a base signal in accordance with at least a torque detection signal Tdet detected by the steering torque sensor, and a damper compensation signal in accordance with the rotational speed or steering speed of the electric motor. And a damper compensation signal calculation unit for calculating an inertia compensation signal based on at least the steering torque Ts, and the damper compensation signal and the inertia compensation signal compensate the base signal. A calculation characteristic setting method in an electric power steering apparatus in which the electric motor is driven by a predetermined target signal to apply a steering assist force, and an evaluation function Ev based on a ratio of the torque detection signal Tdet to the steering torque Ts And a compensator used for calculation in the inertia compensation signal calculation unit (S) is characterized in that it comprises the steps that are set based on the evaluation function Ev.
The invention according to claim 3 is the calculation characteristic setting method according to claim 1 , wherein the evaluation function Ev is set based on a ratio of the torque detection signal Tdet to the steering torque Ts. Features.
According to a fourth aspect of the present invention, in the calculation characteristic setting method according to any one of the first to third aspects, the steering torque Ts is an inertia torque, a viscous torque, and a reaction torque. It is the sum of the torque detection signal Tdet .
According to a fifth aspect of the present invention, in the calculation characteristic setting method according to any one of the first to fourth aspects, the setting of the characteristic in the step is performed by mounting the electric power steering device on a vehicle. In other words, the electric power steering device is executed with the electric power steering device mounted on the vehicle, and the characteristic calculated by the base signal calculation unit and the characteristic calculated by the damper compensation signal calculation unit are set. These steps (SP40, SP50) are provided.

  Since the inertia compensation signal is calculated only in accordance with the steering torque and does not depend on the vehicle speed, it is possible to set a characteristic to be calculated by the inertia compensation signal calculation unit without mounting the electric power steering device on the vehicle. Since the setting can be made without having the characteristic calculated by the base signal calculation unit, complete inertia compensation is possible as manual steering.

According to a sixth aspect of the present invention, there is provided an electric power steering apparatus including a base signal calculation unit (220) for calculating a base signal according to at least the steering torque Ts , and a damper according to the rotational speed or the steering speed of the electric motor (11). An inertia compensation signal based on at least the steering torque Ts using a damper compensation signal calculation unit (225) for calculating a compensation signal and a calculation characteristic setting method according to any one of claims 1 to 5. An inertia compensation signal computation unit (215) for computing the motor, and the motor is driven by a target signal determined by the damper compensation signal and the inertia compensation signal compensating the base signal to give a steering assist force. the electric power steering system to the characteristics of the inertia compensation signal computing part, the characteristics of the differentiation means (230) Issue is divided into a characteristic of improving stability means (235), said compensation signal the base signal compensated by the damper compensation signal and an adder for adding the output signal from said differentiating means (250) is provided, wherein The signal stability improving means is arranged on the output side of the adder.

  The base signal is calculated according to at least the steering torque, and the damper compensation signal is calculated according to the rotation speed or steering speed of the motor. On the other hand, the inertia compensation signal is calculated according to only the steering torque. Therefore, the characteristics calculated by the inertia compensation signal calculation unit can be set independently from the base signal calculation unit and the damper compensation signal calculation unit. Further, the gain characteristic of the stabilization improving means is in a relation inverse to the gain characteristic of the steering torque Ts, and the phase characteristic of the differentiating means and the phase characteristic of the stabilization improving means are in a relationship canceling each other. Thereby, the output gain of the electric power steering apparatus is made uniform, the phase characteristic is improved, and the control stability is enhanced.

  ADVANTAGE OF THE INVENTION According to this invention, the calculation characteristic setting method and electric power steering apparatus which can reduce the influence between an inertia compensation signal, a damper compensation signal, and a base signal can be provided.

(First embodiment)
An electric power steering apparatus according to an embodiment of the present invention will be described with reference to the drawings.
In FIG. 1, an electric power steering apparatus 100 includes a main steering shaft 3 provided with a steering handle 2, a shaft 1, and a pinion shaft 5 connected by two universal joints (universal joints) 4. A pinion gear 7 provided at the lower end of the pinion shaft 5 meshes with the rack teeth 8a of the rack shaft 8 that can reciprocate in the vehicle width direction. The steered wheels 10 and 10 are connected. With this configuration, the electric power steering apparatus 100 can change the traveling direction of the vehicle when the steering handle 2 is steered. Here, the rack shaft 8, the rack teeth 8a, and the tie rods 9 and 9 constitute a turning mechanism. The pinion shaft 5 is supported by the steering gear box 20 through the bearings 6a, 6b, and 6c at its lower, middle, and upper portions.

  The electric power steering apparatus 100 also includes an electric motor 11 that supplies an auxiliary steering force for reducing the steering force by the steering handle 2, and a worm gear 12 provided on the output shaft of the electric motor 11 is connected to a pinion shaft. 5 is meshed with a worm wheel gear 13 provided at 5. That is, the worm gear 12 and the worm wheel gear 13 constitute a speed reduction mechanism. The worm gear 12, the worm wheel gear 13, the pinion shaft 5, the rack shaft 8, the rack teeth 8a, the tie rods 9, 9 and the like connected to the rotor of the electric motor 11, the electric motor 11, and the like constitute a steering system.

The electric motor 11 is a three-phase brushless motor including a stator (not shown) having a plurality of field coils and a rotor (not shown) that rotates inside the stator, and mechanically transfers electric energy. It is converted into energy (P _M = ωT _M ). Here, ω is the rotational speed, and T _M is the torque generated by the electric motor 11. Further, the relationship between the generated torque T _M and the output torque T _M ′ that can actually be taken out as an output is expressed by the following equation. (I: Reduction ratio between the worm gear 12 and the worm wheel gear 13)
_{T M '= T M - (} c m dθ m / dt + J m d 2 θ m / dt 2) i 2 (1)
From this equation, the relationship between the output torque T _M ′ and the motor rotation angle θ _m is defined by the inertia moment J _m of the rotor of the motor 11 and the viscosity coefficient _cm, and is independent of the vehicle characteristics and the vehicle state.

Here, varying the steering torque applied to the steering wheel 2 Ts, the coefficients of the assist amount A _H, which assists the torque of the electric motor 11, which is boosted through a reduction mechanism, for example, as a function of the vehicle speed V k _A (V). In this case, since A _H = k _A (V) × Ts, the pinion torque that is the road surface load Tp is
Tp = Ts + A _H
= Ts + k _A (V) × Ts
It becomes. From this, the steering torque Ts is
Ts = Tp / (1 + k _A (V)) (2)
It is expressed.

Therefore, the steering torque Ts is reduced to 1 / (1 + k _A (V)) times the pinion torque Tp (load). For example, if k _A (0) = 2 when the vehicle speed V = 0, the steering torque Ts is controlled to be 1/3 lighter than the pinion torque Tp, and k _A when the vehicle speed V = 100 km / h. If (100) = 0, the steering torque Ts becomes equal to the pinion torque Tp, and the steering feeling is controlled to a solid weight equivalent to that of manual steering. That is, by controlling the steering torque Ts according to the vehicle speed V, a light and stable steering feeling can be imparted lightly at low speeds and firmly at high speeds.

In general, the steering torque Ts is
Ts = J · d ² θ _S / dt ² + C · dθ _S / dt + K (θ _S −θ _F ) (3)
I know that Here, θ _S is a steering rotation angle, and θ _F is a value obtained by dividing the motor rotation angle θ _m by the rotation ratio n _M of the speed reduction mechanism. J is the inertia coefficient (inertia) of the steering system, C is the viscosity coefficient (damper) of the steering system, and K is the base signal coefficient. This formula is also irrelevant to the vehicle characteristics and the vehicle state, like the formula (1).

At this time, in evaluating the steering feeling, attention is paid to the difference in the steering reaction force depending on the presence or absence of the moment of inertia, and the moment of inertia can be evaluated using the ratio Ev between the input torque and the reaction force torque (inertia torque) as an evaluation function. it can. From the evaluation results using this evaluation function, it was found that there is a region where the steering feeling evaluation is high in the vicinity of the inertia coefficient J of the steering system and the point Ev0 where the viscosity around the steering system is ignored. Here, the ratio Ev is
Ev = Tdet / Ts = K (θ _S −θ _F ) / Ts (4)
It is. Thereby, it is possible to obtain a compensator H (S) that makes the gain characteristic of the transfer function from Ts to Tdet = K (θ _S −θ _F ) equal to or less than Ev0.

Since the compensator obtained by the H∞ control is determined by the target model and the order of the frequency weighting function, it becomes a high-order compensator that is difficult to realize with a normal microcomputer. Therefore, the order of the compensator was reduced by focusing on the frequency band necessary for controlling the steering system.
For example, the transfer function Hf (S) is set to have four zeros and four poles.
Hf (S) = 8.88 (S + 140) (S + 65.1) (S + 30.1) (S + 1.77) / {(S + 1730) (S + 209) (S + 37.1) (S + 15.6)}
Can be set to As described in the second embodiment, the gain characteristic of the transfer function Hf (S) has a differential characteristic.

The electric power steering apparatus 100 includes a control unit 200, a motor driving means 60 for driving the electric motor 11, a resolver 50, a torque sensor 30 for detecting the pinion torque _{T P} applied to the pinion shaft 5, a torque sensor 30 Are provided with a differential amplifier circuit 40 and a vehicle speed sensor 35.

The motor driving means 60 includes a plurality of switching elements such as a three-phase FET bridge circuit, for example, and generates a rectangular wave voltage using a DUTY (DUTY U, DUTY V, DUTY W) signal from the control device 200. The motor 11 is driven. The motor driving means 60 has a function of detecting a three-phase motor current I (IU, IV, IW) using a hall element (not shown). The resolver 50 detects an electric motor rotation angle θ _m of the electric motor 11 and outputs an angle signal θ. For example, a magnetic sensor provided with a plurality of uneven portions at equal intervals in the circumferential direction is provided as a sensor for detecting a change in magnetoresistance. There is something close to the rotating body.

The torque sensor 30 is for detecting the pinion torque T _P applied to the pinion shaft 5, the magnetic film is deposited such that the reverse anisotropy in the axial direction two portions of the pinion shaft 5, the magnetic A detection coil is inserted on the surface of the membrane so as to be separated from the pinion shaft 5. The differential amplifier circuit 40 amplifies a difference in magnetic permeability change between the two magnetostrictive films detected by the detection coil as an inductance change, and outputs a torque signal T.

  The vehicle speed sensor 35 detects the vehicle speed V of the vehicle as the number of pulses per unit time, and outputs a vehicle speed signal VS.

The control device 200 includes a computer and a program including a CPU, a ROM, a RAM, and the like, and realizes the functions described in the algorithm configuration diagram of FIG.
2 includes a base signal calculation unit 220, an inertia compensation signal calculation unit 210, a damper compensation signal calculation unit 225, a Q-axis (torque axis) PI control unit 240, and a D-axis (magnetic pole axis) PI. A control unit 245, a two-axis three-phase conversion unit 260, a PWM conversion unit 270, a three-phase two-axis conversion unit 265, a motor speed calculation unit 280, and an excitation current generation unit 285 are provided.

The three-phase two-axis converter 265 detects the three-phase currents IU, IV, IW of the electric motor 11 (see FIG. 1) detected by the electric motor driving means 60, the D-axis that is the magnetic pole axis of the rotor of the electric motor 11, and this is intended to convert the two axes of the Q axis is an axis rotated 90 electrical degrees with respect to the D-axis, Q-axis current IQ is proportional to the generated torque T _M of the motor 11, the D-axis current ID is energized Proportional to current. The motor speed calculation unit 280 generates an angular velocity signal ω by differentiating the angle signal θ. The exciting current generator 285 generates a target signal of the exciting current “0” of the electric motor 11 (see FIG. 1), and performs field-weakening control by making the D-axis current and the Q-axis current substantially equal if necessary. be able to.

The base signal calculation unit 220 generates a base signal D _T that serves as a reference for the target signal IM of the output torque T _M ′ from the torque signal T and the vehicle speed signal VS. This signal generation is performed by referring to the base table 220a previously set by experimental measurement or the like by the torque signal T and the vehicle speed signal VS, and the base signal D _T stored in the base table 220a in FIG. The function of The base signal calculation unit 220 is provided with a dead band N1 in which the base signal _DT is set to zero when the value of the torque signal T is small. When the value of the torque signal T becomes larger than the dead band N1, the base signal calculation unit 220 is linear with the gain G1. It has an increasing characteristic. Further, the base signal calculation unit 220 has a characteristic that the output increases with the gain G2 at a predetermined torque value, and the output is saturated when the torque value further increases. In general, since the load on the road surface (road reaction force) varies depending on the traveling speed, the vehicle has a gain adjusted by the vehicle speed signal VS. The load is heaviest during stationary operation at zero vehicle speed, and the load is relatively light at medium and low speeds. For this reason, the base signal calculation unit 220 sets the gain (G1, G2) to be low and the dead zone N1 to be large as the vehicle speed V increases and increases to increase the manual steering area and provide road surface information to the driver. To give. That is, as the vehicle speed V increases, a firm feeling of steering torque Ts is given. At this time, it is necessary to perform inertia compensation also in the manual steering region.

Returning to FIG. 2, the damper compensation signal calculation unit 225 is provided to compensate for the viscosity of the steering system and to have a steering damper function that compensates for a decrease in convergence when the vehicle travels at a high speed. The angular velocity signal ω is obtained by referring to the damper table 225a. FIG. 3B is a diagram showing a characteristic function of the damper table 225a. The compensation value I increases linearly as the rotational speed ω of the electric motor 11 (see FIG. 1) increases, and the compensation value is increased at a predetermined speed. It has characteristics that increase rapidly. Further, as the value of the vehicle speed signal VS is higher, the gain is increased to attenuate the output torque T _M ′ of the electric motor 11 according to the rotational speed of the electric motor 11, that is, the steering speed (steering rotational speed). In other words, when a large current is supplied to the electric motor 11 (see FIG. 1) and the rotational speed is increased, the rotational speed does not decrease immediately due to the inertia of the electric motor 11. In order to avoid this phenomenon, the damper compensation signal calculation unit 225 suppresses and controls the rotation speed of the electric motor 11. Due to this steering damper effect, the convergence of the steering wheel can be improved and the vehicle characteristics can be stabilized.

Returning to FIG. 2 again, the adder 251 subtracts the output signal of the damper compensation signal calculation unit 225 from the output signal _DT of the base signal calculation unit 220. The adder 250 adds the output signal of the adder 251 to the output signal _DT. The output signal of the inertia compensation signal calculation unit 210 is added. The base signal calculation unit 220, the damper compensation signal calculation unit 225, and the adder 251 perform assist control.

The inertia compensation signal calculation unit 210 compensates for the influence of the inertia of the steering system, the torque signal T is calculated by referring to the inertia table 210a, and the transfer function Hf (S) of the stored table is
Hf (S) = 8.88 (S + 140) (S + 65.1) (S + 30.1) (S + 1.77) / {(S + 1730) (S + 209) (S + 37.1) (S + 15.6)}
It is.

  The inertia compensation signal calculation unit 210 compensates for a decrease in responsiveness due to the inertia of the rotor of the electric motor 11. In other words, when switching the rotation direction from the normal rotation to the reverse rotation, or from the reverse rotation to the normal rotation, the electric motor 11 tries to maintain the state by inertia, so the rotation direction is not immediately switched. Therefore, the inertia compensation signal calculation unit 210 performs control so that the switching of the rotation direction of the electric motor 11 coincides with the timing at which the rotation direction of the steering handle 2 is switched. In this way, the inertia compensation signal calculation unit 210 improves the response delay of the steering due to the inertia (or viscosity) of the steering system and provides a clean steering feeling. It is also practical for vehicle characteristics such as front engine front wheel drive (FF), front engine rear wheel drive (FR), recreation vehicle (RV) and sedan, and steering characteristics that vary depending on vehicle conditions such as vehicle speed and road surface. Sufficient properties are imparted.

  The output signal IM of the adder 250 is a Q-axis current target signal that defines the torque of the electric motor 11 (see FIG. 1), and the adder 252 subtracts the Q-axis current IQ from the output signal IM to obtain the deviation signal IE. Generate. The Q-axis (torque axis) PI control unit 240 performs P (proportional) control and I (integral) control so that the deviation signal IE decreases. The adder 253 subtracts the D-axis current ID from the output signal of the exciting current generator 285. The D axis (magnetic pole axis) PI control unit 245 performs PI feedback control so that the output signal of the adder 253 decreases.

  The 2-axis 3-phase converter 260 converts the 2-axis signal of the output signal VQ of the Q-axis (torque axis) PI control unit 240 and the output signal VD of the D-axis (magnetic pole axis) PI control unit 245 into 3-phase signals UU, UV , UW. The PWM converter 270 is a DUTY signal (DUTY U, DUTY V, DUTY W) which is an ON / OFF signal [PWM (Pulse Width Modulation) signal] with a pulse width proportional to the magnitude of the three-phase signals UU, UV, UW. Is generated. The biaxial three-phase converter 260 and the PWM converter 270 receive the angle signal θ of the electric motor 11 (see FIG. 1) and output a signal corresponding to the magnetic pole position of the rotor.

Next, a method for setting the base table 220a, the inertia table 210a, and the damper table 225a will be described with reference to the flowchart of FIG.
In step SP10, the setter connects the steering gear box 20 and the control device 200. At this time, the steering gear box 20 is not mounted on the vehicle body. In other words, this state is a state in which the electric power steering device 100 is not mounted on the vehicle. In step SP20, the inertia table 210a of the inertia compensation signal calculation unit 210 is set. The inertia table 210a depends on the torque signal T and does not depend on the vehicle speed signal VS. For example, the inertia table 210a is calculated on the desk and reduced in dimension like the above-described H∞ control, and can be set without applying a vehicle load. Easy to set up. In step SP30, the electric power steering device 100 is mounted on the vehicle. In step SP40, the base table 220a of the base signal calculation unit 220 is set. Then, the damper table 225a of the damper compensation signal calculation unit 225 is set. That is, since the base table 220a and the damper table 225a are functions of the vehicle speed signal VS, it is necessary to set them by mounting on the vehicle.

  As described above, according to the present embodiment, the characteristic of the inertia table 210a does not depend on the vehicle speed signal VS, and therefore can be set independently of the damper table 225a and the base table 220a. Therefore, the inertia table 210a can be set in a state where the steering gear box 20 and the control device 200 are connected. Of course, it may be designed on the desk, and in this case, only confirmation work is required.

(Second Embodiment)
Although the first embodiment compensates by adding / subtracting the output signal of the inertia compensation signal calculation unit 210 and the output signal of the damper compensation signal calculation unit 225 with reference to the output signal _DT of the base signal calculation unit 220, The characteristic of the compensation signal calculation unit 210 is divided into the characteristic of the differentiation unit and the characteristic of the stabilization improvement unit, and compensation is performed using the output signal of the differentiation unit and the output signal of the damper compensation signal calculation unit 225, thereby improving the stability. Means can be used to stabilize the control.

  The configuration of the control device of this embodiment will be described with reference to FIG. In the control device 205 of FIG. 5, a base signal calculation unit 220, a damper compensation signal calculation unit 225, a Q-axis (torque axis) PI control unit 240, a D-axis (magnetic pole axis) PI control unit 245, an excitation current generation unit 285, 2 Since the configurations of the shaft three-phase conversion unit 260, the PWM conversion unit 270, the three-phase two-axis conversion unit 265, the motor speed calculation unit 280, and the adders 251, 252, and 253 are the same as those in the first embodiment, a description will be given. Omitted. The electric power steering apparatus 100 shown in FIG.

  Differentiating means 230 differentiates the torque signal T, and the torque signal T is calculated by referring to the differentiation table 230a. The adder 250 adds the output signal of the differentiating means 230 and the output signal of the adder 251. The stabilization improving unit 235 includes a stabilization table 235 a, stabilizes the output signal of the adder 250, and outputs it to the adder 252. In other words, the differentiating unit 230 is disposed on the upstream side of the adder 250, and the stabilization improving unit 235 is disposed on the downstream side of the adder 250. The inertia compensation signal calculation unit 215 includes a differentiation unit 230 and a stabilization improvement unit 235.

FIG. 6 is a Bode diagram of the steering torque Ts, the differentiation means 230, and the stabilization improving means 235 of the electric power steering apparatus 100.
As can be seen from FIG. 6A, the steering torque Ts of the electric power steering apparatus 100 has a characteristic that it is low in the low frequency region, maximizes in the medium frequency region, and attenuates in the high frequency region. This indicates that the attenuation is insufficient in the middle frequency region.

  Further, as shown in FIG. 6B, the gain characteristic H1f of the differentiating means 230 has a characteristic that the gain increases with the increase of the frequency f and the phase advances although it attenuates in the low frequency region. . As shown in FIG. 6C, the gain characteristic H2f of the stabilization improving means 235 has a characteristic that the attenuation factor is low in the low frequency region, becomes minimal in the medium frequency region, and becomes maximal in the high frequency region. That is, the characteristics of the electric power steering apparatus 100 and the gain characteristics of the stabilization improving means 235 are basically different from each other in that they are slightly different in that they become maximum in the high frequency region of the stabilization improving means 235. . For this reason, by dividing into the differentiation means 230 and the stabilization improving means 235, the frequency characteristics of the output gain of the electric power steering apparatus 100 can be made uniform, and the control stability can be improved.

Next, an example of the second embodiment will be described with reference to FIG.
The transfer function Hf (S) of the inertia compensation signal calculation unit 215 (see FIG. 5) is expressed as Hf (S) = 8.88 (S + 140) (S + 65.1) (S + 30.1) (S + 1.77) / {(S + 1730) (S + 209) (S + 37.1) (S + 15.6)}
The transfer function Hf (S) is divided into a transfer function H1f (S) of the differentiating means 230 and a transfer function H2f (S) of the stabilization improving means 235 (see FIG. 5). That is, the transfer function H1f (S) is
H1f (S) = 2.77 (s + 30.1) (S + 1.77) / {(S + 209) (S + 37.1)}
And the transfer function H2f (S) is
H2f (S) = 2.97 (S + 140) (S + 65.1) / {(S + 1730) (S + 15.6)}
It is.

  FIG. 7 shows a Bode diagram of the transfer function H1f (S) and the transfer function H2f (S). FIG. 7A is a diagram showing the gain-frequency characteristics. The solid line H1f (S) attenuates in the low frequency region below 1 Hz, but the gain increases as the frequency increases, and in the high frequency region above several tens of Hz. The differential characteristic is saturated at a gain of 20 dB. A broken line H2f (S) in FIG. 7A has a characteristic of being attenuated by a certain amount of about −10 dB in the low frequency region, and having a minimum point of −20 dB in the middle frequency region, and the waveform of FIG. Similar. For this reason, the gain characteristic of the transfer function H2f (S) cancels the characteristic of FIG. 6A indicating the steering torque Ts.

  FIG. 7B shows the phase characteristics, the solid line H1f (S) shows the maximum in a low frequency region of about several Hz, the broken line H2f (S) shows the minimum in a low frequency region of about several Hz, and 100 Hz. It shows the maximum in degree. That is, it can be seen that the phase characteristics cancel each other out at least in the low frequency region.

イナーシャ特性Ｈｆのゲイン余裕は１０．９ｄＢであり、位相余裕は３５°であり、微分手段２３０および安定化向上手段２３５の合成特性Ｈ１ｆ＆Ｈ２ｆのゲイン余裕は１１．７ｄＢであり、位相余裕は５８．５°であり、ゲイン余裕と位相余裕との双方が増加している。 Further, gain margin (remainder) and phase margin (remainder) between the inertia characteristic Hf of the inertia compensation signal calculation unit 210, the combined characteristic of the differential characteristic H1f of the differentiating means 230, and the stabilization characteristic H2f of the stabilization improving means 235. Yes) is shown in Table 1.

The gain margin of the inertia characteristic Hf is 10.9 dB, the phase margin is 35 °, the gain margin of the combined characteristics H1f & H2f of the differentiating means 230 and the stabilization improving means 235 is 11.7 dB, and the phase margin is 58.5. °, both gain margin and phase margin are increasing.

  As described above, according to the present embodiment, the inertia characteristic Hf of the inertia compensation signal calculation unit 210 is divided into the differentiating means 230 and the stabilization improving means 235. Here, the gain characteristic of the stabilization improving means 235 is in a relationship inverse to the gain characteristic of the steering torque Ts, and the phase characteristic of the differentiating means 230 and the phase characteristic of the stabilization improving means 235 cancel each other. . Therefore, the inertia characteristic Hf has a differential characteristic in effect, and the responsiveness is improved. Further, the output gain of the electric power steering device 100 is made uniform, and the control stability is improved. Also, by cutting out the characteristic H2f of the stabilization improving means 235 that stabilizes the system from the inertia characteristic Hf, what has been conventionally designed separately can be designed simultaneously.

(Modification)
The present invention is not limited to the above-described embodiment, and for example, the following various modifications are possible.
(1) In each of the above embodiments, the target current is set and the current flowing through the motor 11 is controlled. However, the voltage applied to the motor 11 can also be set as the target voltage, and the torque output from the motor 11 can be set as the target. It is also possible to control the current flowing through the electric motor 11 by setting the torque. This target voltage or target torque is also included in the target signal.
(2) The electric power steering apparatus of the present invention includes a steer-by-wire (Steer_By_Wire) in which the steering handle 2 and the steered wheel 10 are mechanically separated.

It is a lineblock diagram of the electric power steering device which is one embodiment of the present invention. It is an algorithm block diagram of the control apparatus of 1st Embodiment. It is a figure which shows the characteristic of a base signal calculating part and a damper compensation signal calculating part. It is a figure which shows the method of setting an inertia table, a damper table, and a base table. It is an algorithm block diagram of the control apparatus of 2nd Embodiment. It is a Bode diagram of an electric power steering device, a differentiation means, and a stabilization improvement means in a second embodiment. It is a Bode diagram of a differentiation means and a stabilization improvement means in an example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shaft 2 Steering handle 3 Main steering shaft 4 Universal joint 5 Pinion shaft 6a, 6b, 6c Bearing 7 Pinion gear 8 Rack shaft 8a Rack tooth 9 Tie rod 10 Steering wheel 11 Electric motor 12 Worm gear 13 Worm wheel gear 20 Steering gear box 30 Torque Sensor 35 Vehicle speed sensor 40 Differential amplifier circuit 50 Resolver 60 Motor drive means 100 Electric power steering device 200, 205 Control device 210, 215 Inertia compensation signal calculation unit 210a Inertia table 220 Base signal calculation unit 220a Base table 225 Damper compensation signal calculation unit 225a Damper table 230 Differentiation means 230a Differentiation table 235 Stabilization improvement means 235a Stabilization table 240 Q axis (torque Axis) PI control unit 245 D-axis (axis of magnetic pole) PI control unit 250,251,252,253 adder 260 2-axis-to-3-phase conversion unit 265 three-phase two-axis converting unit 270 PWM conversion unit 280 motor speed calculation unit

Claims (6)

A base signal calculation unit that calculates a base signal in accordance with at least a torque detection signal Tdet detected by the steering torque sensor;
A damper compensation signal calculation unit that calculates a damper compensation signal according to the rotational speed or steering speed of the electric motor;
An inertia compensation signal calculation unit that calculates an inertia compensation signal based on at least the steering torque Ts,
A calculation characteristic setting method in an electric power steering apparatus in which the motor is driven by a target signal determined by the damper compensation signal and the inertia compensation signal compensating the base signal, and a steering assist force is applied.
An evaluation function Ev is set based on the steering torque Ts,
When setting the compensator H (S) used for calculation in the inertia compensation signal calculation unit ,
A calculation characteristic setting method comprising: setting the gain characteristic of the evaluation function Ev to be equal to or less than the gain characteristic of the evaluation function Ev0 when the inertia coefficient of the steering system and the viscosity around the steering system are ignored . A base signal calculation unit that calculates a base signal in accordance with at least a torque detection signal Tdet detected by the steering torque sensor;
A damper compensation signal calculation unit that calculates a damper compensation signal according to the rotational speed or steering speed of the electric motor;
An inertia compensation signal calculation unit that calculates an inertia compensation signal based on at least the steering torque Ts,
A calculation characteristic setting method in an electric power steering apparatus in which the motor is driven by a target signal determined by the damper compensation signal and the inertia compensation signal compensating the base signal, and a steering assist force is applied.
An evaluation function Ev is set based on the ratio of the torque detection signal Tdet to the steering torque Ts,
A calculation characteristic setting method comprising: a step of setting a compensator H (S) used for calculation in the inertia compensation signal calculation unit based on the evaluation function Ev. The calculation characteristic setting method according to claim 1, wherein the evaluation function Ev is set based on a ratio of the torque detection signal Tdet to the steering torque Ts. The steering torque Ts is the inertia torque, and the viscous torque, calculation of any one of claims 1 to 3, characterized in that said torque detection signal Tdet, the sum of a reactive torque Characteristic setting method. The step includes
Executed in a state where the electric power steering device is not mounted on a vehicle,
The electric power steering apparatus is executed in a state where the electric power steering apparatus is mounted on the vehicle, and includes another step in which a characteristic calculated by the base signal calculation unit and a characteristic calculated by the damper compensation signal calculation unit are set. The calculation characteristic setting method according to any one of claims 1 to 4, characterized in that: A base signal calculator for calculating a base signal according to at least the steering torque Ts;
A damper compensation signal calculation unit that calculates a damper compensation signal according to the rotational speed or steering speed of the electric motor;
An inertia compensation signal calculation unit that calculates an inertia compensation signal based on at least the steering torque Ts using the calculation characteristic setting method according to any one of claims 1 to 5.
In the electric power steering device in which the motor is driven by a target signal determined by the damper compensation signal and the inertia compensation signal compensating the base signal, and a steering assist force is applied,
The characteristic of the inertia compensation signal calculation unit is divided into the characteristic of the differentiating means and the characteristic of the signal stability improving means,
An adder for adding a compensation signal obtained by compensating the base signal with the damper compensation signal and an output signal from the differentiating means;
The electric power steering apparatus, wherein the signal stability improving means is arranged on an output side of the adder.

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