JP2010202144A - Electric power steering device, and device and method for estimating rotational speed - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of accurately estimating the rotational speed of an electric motor. <P>SOLUTION: The electric power steering device has a first estimation part 241 for estimating the rotational speed of the electric motor based on an actual current detected by a motor current detection part 33 and mechanical characteristic of the electric motor, a high-pass filter (HPF) 243 for removing a low frequency component of the rotational speed estimated by the first estimation part 241, a second estimation part 242 for estimating the rotational speed of the electric motor based on the actual current detected by the motor current detection part 33, the voltage detected by a motor voltage detection part 160, and the electric characteristic of the electric motor, and a low-pass filter (LPF) 244 for removing a high frequency component of the rotational speed estimated by the second estimation part 242. The rotational speed of the electric motor is estimated based on the output result of the high-pass filter 243 and the output result of the low-pass filter 244. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric power steering device, a rotational speed estimation device, and a rotational speed estimation method.

  In recent years, there has been proposed an electric power steering device that includes an electric motor in a steering system of a vehicle and assists a driver's steering force with the power of the electric motor. The control device that controls the electric power steering device determines a current to be supplied to the electric motor based on the detected steering torque and the estimated rotation speed of the electric motor in order to control the driving of the electric motor.

  The following techniques have been proposed as techniques for estimating the rotational speed of the electric motor. For example, in Patent Document 1, the rotation speed is estimated based on the detected current and voltage of the electric motor and the electrical characteristics (for example, armature resistance) of the electric motor.

Japanese Patent Laid-Open No. 3-176271

The method for estimating the rotational speed of the electric motor based on the electric characteristics of the electric motor as described in Patent Document 1 is based on the premise that there is no current change, and thus the estimation accuracy in a transient state is low. Become. In addition, if there is noise in the detected current value of the electric motor or the like, it is easily affected by the noise, and the estimation accuracy is lowered.
Therefore, an object of the present invention is to accurately estimate the rotational speed of an electric motor.

  For this purpose, the present invention detects a steering torque detecting means for detecting a steering torque of a steering wheel, an electric motor for giving a steering assist force to the steering wheel, and an actual current actually supplied to the electric motor. Current detecting means for detecting, voltage detecting means for detecting the voltage across the terminals of the electric motor, and the rotational speed of the electric motor is estimated based on the actual current detected by the current detecting means and the voltage detected by the voltage detecting means. Rotation speed estimation means for performing, and target current setting means for setting a target current to be supplied to the electric motor based on the steering torque detected by the steering torque detection means and the rotation speed estimated by the rotation speed estimation means, In the electric power steering apparatus provided, the rotational speed estimating means includes the actual current detected by the current detecting means and the electric motor. First estimating means for estimating the rotational speed of the electric motor based on mechanical characteristics, low frequency component removing means for removing a low frequency component of the rotational speed estimated by the first estimating means, and the current Second estimation means for estimating the rotational speed of the electric motor based on the actual current detected by the detection means, the voltage detected by the voltage detection means, and the electrical characteristics of the electric motor; and the second estimation means High-frequency component removing means for removing the high-frequency component of the estimated rotational speed, and the rotational speed of the electric motor is determined based on the output result of the low-frequency component removing means and the output result of the high-frequency component removing means. An electric power steering apparatus characterized by estimating.

  Here, the first estimation unit includes a calculation unit that multiplies the actual current detected by the current detection unit by a torque constant of the electric motor and a reciprocal of the inertia of the electric motor, and the calculation unit. It is preferable to have integration means for integrating the output results of

  Further, the second estimating means includes first multiplying means for multiplying the actual current detected by the current detecting means and the armature resistance of the electric motor, and the first detecting means based on the voltage detected by the voltage detecting means. It is preferable to have subtracting means for subtracting the output result of the multiplying means, and second multiplying means for multiplying the output result of the subtracting means by the inverse of the induced voltage constant of the electric motor.

The low frequency component removing means is preferably a high pass filter, and the high frequency component removing means is preferably a low pass filter.
Furthermore, it is preferable that the cutoff frequency of the high pass filter is higher than the cutoff frequency of the low pass filter.

From another point of view, the present invention is a rotation speed estimation device that estimates the rotation speed of an electric motor that applies a steering assist force to a steering wheel, and is a current detection unit that detects an actual current supplied to the electric motor. And voltage detection means for detecting a voltage between terminals of the electric motor;
First estimation means for estimating the rotational speed of the electric motor based on the actual current detected by the current detection means and the mechanical characteristics of the electric motor; and a low rotational speed estimated by the first estimation means. Based on the low frequency component removing means for removing the frequency component, the actual current detected by the current detecting means, the voltage detected by the voltage detecting means, and the electrical characteristics of the electric motor, the rotational speed of the electric motor is estimated. Second estimation means, high frequency component removal means for removing high frequency components of the rotational speed estimated by the second estimation means, output results of the low frequency component removal means, and output results of the high frequency component removal means And an addition means for adding the rotation speed.

  From another point of view, the present invention is a rotational speed estimation method for estimating the rotational speed of an electric motor that applies a steering assist force to a steering wheel, and detects an actual current supplied to the electric motor, The voltage between the terminals of the electric motor is detected, the value obtained by removing the low frequency component of the rotational speed estimated based on the detected actual current and the mechanical characteristics of the electric motor, the detected actual current and the detected voltage, A rotational speed estimation method for estimating a rotational speed by adding a value obtained by removing a high-frequency component of a rotational speed estimated based on the electrical characteristics of the electric motor.

  According to the present invention, it is possible to accurately estimate the rotation speed of the electric motor.

It is a figure showing the schematic structure of the electric power steering device concerning an embodiment. It is a schematic block diagram of the control apparatus of an electric power steering apparatus. It is a schematic block diagram of a target current calculation part. It is a schematic block diagram of a control part. It is a block diagram of a motor rotation speed estimation part. It is a figure which shows the characteristic of the high-pass filter and low-pass filter which are used by this Embodiment. It is a figure which shows the relationship between a cutoff frequency and a vehicle speed. It is a figure which shows the relationship between a cutoff frequency and torque variation.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIG. 1 is a diagram illustrating a schematic configuration of an electric power steering apparatus 100 according to an embodiment.
The electric power steering device 100 (hereinafter sometimes simply referred to as the “steering device 100”) is a steering device for arbitrarily changing the traveling direction of the vehicle. In the present embodiment, the configuration is applied to an automobile. Illustrated.

  The steering device 100 includes a wheel-like steering wheel (handle) 101 operated by a driver, and a steering shaft 102 provided integrally with the steering wheel 101. The steering shaft 102 and the upper connection shaft 103 are connected via a universal joint 103a, and the upper connection shaft 103 and the lower connection shaft 108 are connected via a universal joint 103b.

  Steering device 100 includes tie rods 104 connected to left and right front wheels 150 as rolling wheels, and rack shaft 105 connected to tie rods 104. Further, the steering device 100 includes a pinion 106 a that constitutes a rack and pinion mechanism together with rack teeth 105 a formed on the rack shaft 105. The pinion 106 a is formed at the lower end portion of the pinion shaft 106.

  The steering device 100 also has a steering gear box 107 that houses the pinion shaft 106. The pinion shaft 106 is connected to the lower connection shaft 108 via a torsion bar (not shown) in the steering gear box 107. Inside the steering gear box 107, a torque sensor 109 is provided as an example of a steering torque detecting means for detecting the steering torque of the steering wheel 101 based on the relative angle between the lower connecting shaft 108 and the pinion shaft 106.

The steering device 100 includes an electric motor 110 supported by the steering gear box 107, and a speed reducing mechanism 111 that decelerates the driving force of the electric motor 110 and transmits it to the pinion shaft 106.
In addition, the steering device 100 includes a motor current detection unit 33 (see FIG. 4) as an example of a current detection unit that detects the magnitude and direction of the actual current that actually flows through the electric motor 110, and the voltage between the terminals of the electric motor 110. Has a motor voltage detection unit 160 for detecting.

  The steering device 100 includes a control device 10 that controls the operation of the electric motor 110. The control device 10 receives the output value of the torque sensor 109, the output value of the vehicle speed sensor 170 that detects the vehicle speed of the vehicle, the output value of the motor current detection unit 33, and the output value of the motor voltage detection unit 160.

  The electric power steering apparatus 100 configured as described above detects the steering torque applied to the steering wheel 101 by the torque sensor 109, drives the electric motor 110 according to the detected torque, and generates the electric motor 110. Torque is transmitted to the pinion shaft 106. Thereby, the torque generated by the electric motor 110 assists the driver's steering force applied to the steering wheel 101.

Next, the control device 10 will be described.
The control device 10 is an arithmetic and logic circuit composed of a CPU, ROM, RAM, backup RAM, and the like.
FIG. 2 is a schematic configuration diagram of the control device 10 of the electric power steering device 100.
The control device 10 includes a torque signal Td in which the steering torque detected by the torque sensor 109 described above is converted into an output signal, and a vehicle speed signal v in which the vehicle speed detected by the vehicle speed sensor 170 is converted into an output signal. Is entered.

Further, the control device 10 converts the motor current signal Im obtained by converting the actual current detected by the motor current detector 33 into an output signal and the voltage detected by the motor voltage detector 160 into an output signal. The motor terminal voltage signal Vm is input.
Since the detection signal from the torque sensor 109 or the like is input as an analog signal, the control device 10 converts the analog signal into a digital signal by an A / D conversion unit (not shown) and takes it into the CPU.

  Then, the control device 10 calculates a target auxiliary torque based on the torque signal Td, a target current calculation unit 20 that calculates a target current necessary for the electric motor 110 to supply the target auxiliary torque, and a target current And a control unit 30 that performs feedback control and the like based on the target current calculated by the calculation unit 20.

Next, the target current calculation unit 20 will be described in detail. FIG. 3 is a schematic configuration diagram of the target current calculation unit 20.
The target current calculation unit 20 includes a base current calculation unit 21 that calculates a base current that serves as a reference for setting the target current, an inertia compensation current calculation unit 22 that calculates a current for canceling the inertia moment of the electric motor 110, and It has. The target current calculation unit 20 estimates the rotation speed of the electric motor 110 based on the damper compensation current calculation unit 23 that calculates a current that limits the rotation of the motor, the motor current signal Im, and the motor terminal voltage signal Vm. A motor rotation speed estimation unit 24 is provided as an example of the rotation speed estimation means. Further, the target current calculation unit 20 includes a final target current determination unit 25 that determines a final target current based on outputs from the base current calculation unit 21, the inertia compensation current calculation unit 22, the damper compensation current calculation unit 23, and the like. I have.

  The base current calculation unit 21 calculates a base current based on the torque signal Ts obtained by phase compensation of the torque signal Td by the phase compensation unit 26 and the vehicle speed signal v from the vehicle speed sensor 170, and information on the base current is obtained. The base current signal Ims including it is output. Note that the base current calculation unit 21, for example, displays a map indicating the correspondence between the torque signal Ts and the vehicle speed signal v and the base current, which is previously created based on an empirical rule and stored in the ROM, and the torque signal Ts and vehicle speed. The base current is calculated by substituting the signal v.

  The inertia compensation current calculation unit 22 calculates an inertia compensation current for canceling the inertia moment of the electric motor 110 and the system based on the torque signal Td and the vehicle speed signal v, and generates an inertia compensation current signal Is including information on the current. Output. For example, the inertia compensation current calculation unit 22 generates a torque signal Td on a map indicating the correspondence between the torque signal Td, the vehicle speed signal v, and the inertia compensation current, which is previously created based on an empirical rule and stored in the ROM. And the inertia compensation current is calculated by substituting the vehicle speed signal v.

The damper compensation current calculation unit 23 calculates a damper compensation current for limiting the rotation of the electric motor 110 based on the torque signal Td, the vehicle speed signal v, and the rotation speed signal Nm of the electric motor 110, and information on this current A damper compensation current signal Id including is output. The damper compensation current calculation unit 23 indicates the correspondence between the torque compensation signal Td, the vehicle speed signal v, the rotation speed signal Nm, and the damper compensation current, which are previously created based on empirical rules and stored in the ROM, for example. The damper compensation current is calculated by substituting the torque signal Td, the vehicle speed signal v, and the rotational speed signal Nm into the map.
The motor rotation speed estimation unit 24 estimates the rotation speed of the electric motor 110 based on the actual current detected by the motor current detection unit 33 and the voltage detected by the motor voltage detection unit 160. Details will be described later.

The final target current determination unit 25 includes the base current signal Ims output from the base current calculation unit 21, the inertia compensation current signal Is output from the inertia compensation current calculation unit 22, and the damper compensation output from the damper compensation current calculation unit 23. A final target current is determined based on the current signal Id, and a target current signal IT including information on this current is output. For example, the final target current determination unit 25 previously created a compensation current obtained by adding the inertia compensation current to the base current and subtracting the damper compensation current based on an empirical rule, and stored it in the ROM. The final target current is calculated by substituting it into a map indicating the correspondence between the compensation current and the final target current.
As described above, the target current calculation unit 20 functions as an example of a target current setting unit that sets a target current to be supplied to the electric motor 110 based on the steering torque detected by the torque sensor 109.

Next, the control unit 30 will be described in detail. FIG. 4 is a schematic configuration diagram of the control unit 30.
The control unit 30 includes a motor drive control unit 31 that controls the operation of the electric motor 110, a motor drive unit 32 that drives the electric motor 110, and a motor current detection unit 33 that detects the actual current that actually flows through the electric motor 110. have.

  The motor drive control unit 31 performs feedback control based on the deviation between the target current calculated by the target current calculation unit 20 and the actual current supplied to the electric motor 110 detected by the motor current detection unit 33. A feedback (F / B) control unit 40 and a PWM signal generation unit 60 that generates a PWM (pulse width modulation) signal for PWM driving the electric motor 110 are included.

The feedback control unit 40 includes a deviation calculating unit 41 for obtaining a deviation between the target current calculated by the target current calculating unit 20 and the actual current detected by the motor current detecting unit 33, and the deviation becomes zero. And a feedback (F / B) processing unit 42 for performing feedback processing.
The deviation calculation unit 41 outputs a deviation value between the output value IT from the target current calculation unit 20 and the output value Im from the motor current detection unit 33 as a deviation signal 41a.

The feedback (F / B) processing unit 42 performs feedback control so that the target current and the actual current match. For example, the input deviation signal 41a is proportionally processed by a proportional element. A signal obtained by the integration processing by the integration element is output, and the addition calculation unit adds these signals to generate and output a feedback processing signal 42a.
The PWM signal generation unit 60 generates the PWM signal 60a based on the output value from the feedback control unit 40, and outputs the generated PWM signal 60a.

  The motor drive unit 32 drives a motor drive circuit 70 in which four power field effect transistors are connected in an H-type bridge circuit configuration, and drives the gates of two field effect transistors selected from the four. And a gate drive circuit unit 80 for switching the field effect transistor. The gate drive circuit unit 80 selects two field effect transistors according to the steering direction of the steering wheel 101 based on the drive control signal (PWM signal) 60a output from the PWM signal generation unit 60, and selects the selected 2 The field effect transistors are switched.

  The motor current detection unit 33 detects the value of the motor current (armature current) flowing through the electric motor 110 from the voltage generated at both ends of the shunt resistor 71 connected in series with the motor drive circuit 70, and outputs the motor current signal Im. To do.

Next, the motor rotation speed estimation unit 24 will be described.
In general, the equation of motion of the electric motor 110 is composed of two equations, the following equation (1) that is an equation for voltage and the following equation (2) that is an equation for torque. .
V = Lm × (dI / dt) + Rm × I + Ke × (dθ / dt) (1)
T = Kt × I (2)
Here, V is a voltage between terminals of the electric motor 110, I is a current flowing through the electric motor 110, θ is a rotation angle of the electric motor 110, and Lm, Rm, Ke, and Kt are inductance and armature resistance of the electric motor 110, respectively. , Induced voltage constant and torque constant.

Further, the balance of torque in the rotational motion can be expressed by the following formula (3).
T = Jm × (d ² θ / dt ² ) (3)
Here, Jm is the inertia of the electric motor 110.
When formulas (2) and (3) are arranged, formula (4) is obtained.
Jm × (d ² θ / dt ² ) = Kt × I (4)
Looking at Equations (1) and (4), Equation (1) is an equation based on the electrical characteristics of the electric motor 110, and Equation (4) is an equation based on the mechanical properties of the electric motor 110. I can say that.

In Expression (1), Lm is usually small and can be ignored. Therefore, when Lm = 0 and the deformation is performed, Expression (5) is obtained.
dθ / dt = (V−Rm × I) / Ke (5)
From this equation (5), the rotational speed (dθ / dt) of the electric motor 110 can be derived based on the electrical characteristics of the electric motor 110.
Further, when equation (4) is modified, equation (6) is obtained.

この式（６）により、電動モータ１１０の回転速度（ｄθ／ｄｔ）を、電動モータ１１０の機械的特性に基づいて導き出すことができる。

From this equation (6), the rotational speed (dθ / dt) of the electric motor 110 can be derived based on the mechanical characteristics of the electric motor 110.

FIG. 5 is a block diagram of the motor rotation speed estimation unit 24.
The motor rotation speed estimation unit 24 is a first estimation unit that estimates the rotation speed of the electric motor 110 based on the actual current detected by the motor current detection unit 33 and the mechanical characteristics of the electric motor 110. Estimator 241. Further, the motor rotation speed estimation unit 24 is based on the actual current detected by the motor current detection unit 33, the voltage detected by the motor voltage detection unit 160, and the electrical characteristics of the electric motor 110. It has the 2nd estimation part 242 as an example of the 2nd estimation means to estimate.

Further, the motor rotation speed estimation unit 24 includes a high-pass filter (HPF) 243 as an example of a low-frequency component removal unit that removes a low-frequency component of the rotation speed estimated by the first estimation unit 241, and a second estimation unit. A low-pass filter (LPF) 244 is provided as an example of a high-frequency component removing unit that removes a high-frequency component of the rotational speed estimated by 242.
Furthermore, the motor rotation speed estimation unit 24 includes an addition unit 240 that adds the output result of the high-pass filter 243 and the output result of the low-pass filter 244.

The 1st estimation part 241 is a site | part estimated based on Formula (6) mentioned above. Therefore, the first estimation unit 241 multiplies the actual current detected by the motor current detection unit 33 by the torque constant Kt of the electric motor 110 and multiplies the reciprocal (1 / Jm) of the inertia Jm of the electric motor 110. And an integrator 246 as an example of integrating means for integrating the output result of the calculating unit 245.
The calculation unit 245 multiplies the output value Im from the motor current detection unit 33 by (torque constant Kt / inertia Jm), and outputs the result 245a. The integrator 246 integrates the output value 245a from the calculation unit 245, and outputs the result 246a.

  The 2nd estimation part 242 is a site | part estimated based on Formula (5) mentioned above. Therefore, the second estimation unit 242 includes a first multiplication unit 247 as an example of a first multiplication unit that multiplies the actual current detected by the motor current detection unit 33 and the armature resistance Rm of the electric motor 110. The subtraction unit 248 as an example of a subtracting unit that subtracts the output result of the first multiplication unit 247 from the voltage detected by the motor voltage detection unit 160, and the output result of the subtraction unit 248 includes the induced voltage constant Ke of the electric motor 110. And a second multiplication unit 249 as an example of second multiplication means for multiplying the reciprocal (1 / Ke).

  The first multiplier 247 multiplies the output value Im from the motor current detector 33 by the armature resistance Rm, and outputs the result 247a. The subtractor 248 subtracts the output value 247a from the first multiplier 247 from the output value Vm from the motor voltage detector 160, and outputs the result 248a. The second multiplication unit 249 multiplies the output value 248a from the subtraction unit 248 by the reciprocal (1 / Ke) of the induced voltage constant Ke, and outputs the result 249a.

  Here, each of the first estimation unit 241 and the second estimation unit 242 can estimate the rotation speed of the electric motor 110 alone. Therefore, if the output values from these are simply added by the adder 240, the value is much larger than the actual rotational speed. In addition, if the steering torque changes in the rotational speed estimated by the first estimating unit 241 even if it is in a steady state, the change appears as an offset error in the rotational speed, so the estimation accuracy in the steady state is high. Lower. Further, since the rotation speed estimated by the second estimation unit 242 is premised on that there is no current change, the accuracy is low in a transient state where the current changes. Further, when there is noise in the output value Im from the motor current detection unit 33, it is easily affected.

  Therefore, in the motor rotation speed estimation unit 24 according to the present embodiment, the low-frequency component of the rotation speed estimated by the first estimation unit 241 is removed by the high-pass filter 243, and the second estimation is performed by the low-pass filter 244. The high frequency component of the rotational speed estimated by the unit 242 is removed, and the output result of the high pass filter 243 and the output result of the low pass filter 244 are added by the adding unit 240.

FIG. 6 is a diagram showing characteristics of the high-pass filter 243 and the low-pass filter 244 used in the present embodiment.
The high pass filter 243 is a filter circuit that extracts a high frequency component of the electric signal and suppresses the low frequency component. The high-pass filter 243 according to the present embodiment sets the frequency region to be passed to be fch (Hz) or higher (that is, the cut-off frequency is fch (Hz)), and attenuates the frequency components that are lower than fch. Thereby, the high pass filter 243 removes the low frequency component of the rotational speed estimated by the first estimation unit 241.

  The low-pass filter 244 is a filter circuit that extracts a low frequency component of the electric signal and suppresses the high frequency component. The low-pass filter 244 according to the present embodiment sets the frequency range to be passed to 0 to fcl (Hz) (that is, the cutoff frequency is fcl (Hz)) and does not pass or attenuate the frequency component higher than fcl. Thereby, the low-pass filter 244 removes the high-frequency component of the rotational speed estimated by the second estimation unit 242.

  In the motor rotation speed estimation unit 24 according to the present embodiment, it is preferable that the cutoff frequency fch of the high-pass filter 243 is higher than the cutoff frequency fcl of the low-pass filter 244. For example, the cut-off frequency fch is 100 (Hz) and the cut-off frequency fcl is 50 (Hz).

  Then, the adding unit 240 adds the output result 243a of the high-pass filter 243 and the output result 244a of the low-pass filter 244, and outputs the added value as the rotation speed signal Nm estimated by the motor rotation speed estimating unit 24.

  In the motor rotation speed estimation unit 24 configured as described above, for example, even if there is a change in the steering torque in a steady state, the rotation speed estimated by the first estimation unit 241 based on mechanical characteristics is The high-pass filter 243 is not passed or attenuated, and the rotation speed estimated by the second estimation unit 242 based on the electrical characteristics is weighted. On the other hand, in the transient state, the rotational speed estimated by the second estimation unit 242 based on the electrical characteristics is not passed or attenuated by the low-pass filter 244 and is estimated by the first estimation unit 241 based on the mechanical characteristics. Emphasis is placed on the rotation speed.

Even if noise is mixed in the output value Im from the motor current detection unit 33, the rotational speed estimated by the second estimation unit 242 based on the electrical characteristics is not passed or attenuated by the low-pass filter 244. Therefore, the rotation speed estimated by the first estimation unit 241 based on mechanical characteristics including an integral element and not easily affected by noise is weighted.
Accordingly, the motor rotation speed estimation unit 24 can accurately estimate the rotation speed of the electric motor 110 in a steady state or a transient state, and can suppress the influence of noise.

Note that the cut-off frequency fch of the high-pass filter 243 and the cut-off frequency fcl of the low-pass filter 244 described above may be changed according to the vehicle speed.
FIG. 7 is a diagram showing the relationship between the cutoff frequencies fch and fcl and the vehicle speed. For example, optimal cutoff frequencies fch and fcl corresponding to the vehicle speed are derived in advance as shown in FIG. Then, the motor rotation speed estimation unit 24 creates a map indicating the correspondence between the vehicle speed signal v and the cutoff frequency fch, and a map indicating the correspondence between the vehicle speed signal v and the cutoff frequency fcl, which is created and stored in the ROM in advance. Alternatively, the cut-off frequencies fch and fcl are calculated and set by substituting the vehicle speed signal v into the relational expression between the vehicle speed signal v and the cut-off frequencies fch and fcl.

  As shown in FIG. 7, the cut-off frequencies fch and fcl are 100 (Hz) when the vehicle speed is zero, increase to 150 (Hz) as the vehicle speed increases, and the vehicle speed is equal to or higher than a certain speed. It is preferable that the frequency is 150 (Hz). As a result, at low speeds, the rotation speed estimated by the first estimation unit 241 based on the mechanical characteristics becomes an estimated value in the motor rotation speed estimation unit 24. Therefore, the rotation speed is more accurate in the transient state. Can be estimated. On the other hand, at high speeds, the rotation speed estimated by the second estimation unit 242 based on the electrical characteristics expands in the frequency region where the estimated value in the motor rotation speed estimation unit 24 is widened. It becomes possible to estimate.

  Further, the cutoff frequencies fch and fcl may be changed according to the steering torque. FIG. 8 is a diagram showing the relationship between the cutoff frequencies fch and fcl and the torque change amount. For example, optimal cutoff frequencies fch and fcl corresponding to the amount of torque change of the steering wheel 101 are previously derived as shown in FIG. 8 based on empirical rules. Then, the motor rotation speed estimation unit 24 creates a map indicating the correspondence between the torque change amount of the steering wheel 101 and the cutoff frequency fch, which is created in advance and stored in the ROM, the torque change amount of the steering wheel 101 and the cutoff value. The cut-off frequencies fch and fcl are calculated by substituting the torque change amount derived from the torque signal Td into the map indicating the correspondence with the frequency fcl. Alternatively, the cut-off frequencies fch and fcl may be calculated by substituting the torque change amount into a relational expression between the cut-off frequencies fch and fcl and the torque change amount created in advance.

Further, it is also preferable that the motor rotation speed estimation unit 24 varies the cutoff frequencies fch and fcl according to the vehicle speed and the steering torque. For example, the relationship between the vehicle speed signal v and the torque change amount of the steering wheel 101 and the optimum cutoff frequencies fch and fcl is derived in advance based on empirical rules. A map showing these correspondences is created in advance and stored in the ROM, and the motor rotation speed estimation unit 24 substitutes the cut-off frequencies fch and fcl by substituting the vehicle speed signal v and the torque change amount into this map. calculate. Alternatively, fch and fcl may be calculated by substituting the vehicle speed signal v and the torque change amount into a relational expression between the vehicle speed signal v and torque change amount and the cut-off frequencies fch and fcl created in advance.
In this manner, the rotational speed of the electric motor 110 can be estimated with higher accuracy by changing the cutoff frequencies fch and fcl based on the vehicle speed signal v and / or the torque signal Td.

DESCRIPTION OF SYMBOLS 10 ... Control apparatus, 20 ... Target electric current calculation part, 24 ... Motor rotational speed estimation part, 30 ... Control part, 33 ... Motor current detection part, 40 ... Feedback control part, 100 ... Electric power steering apparatus, 101 ... Steering wheel, DESCRIPTION OF SYMBOLS 102 ... Steering shaft, 109 ... Torque sensor, 110 ... Electric motor, 160 ... Motor voltage detection part, 170 ... Vehicle speed sensor, 240 ... Addition part, 241 ... 1st estimation part, 242 ... 2nd estimation part, 243 ... High-pass filter, 244 ... Low-pass filter, 245 ... Calculation unit, 246 ... Integrator, 247 ... First multiplication unit, 248 ... Subtraction unit, 249 ... Second multiplication unit

Claims (7)

Steering torque detecting means for detecting steering torque of the steering wheel;
An electric motor for providing a steering assist force to the steering wheel;
Current detection means for detecting an actual current actually supplied to the electric motor;
Voltage detecting means for detecting a voltage between terminals of the electric motor;
A rotational speed estimating means for estimating the rotational speed of the electric motor based on the actual current detected by the current detecting means and the voltage detected by the voltage detecting means;
Target current setting means for setting a target current to be supplied to the electric motor based on the steering torque detected by the steering torque detection means and the rotation speed estimated by the rotation speed estimation means;
In the electric power steering apparatus with
The rotational speed estimation means includes
First estimation means for estimating the rotational speed of the electric motor based on the actual current detected by the current detection means and the mechanical characteristics of the electric motor;
Low frequency component removing means for removing the low frequency component of the rotational speed estimated by the first estimating means;
Second estimation means for estimating the rotation speed of the electric motor based on the actual current detected by the current detection means, the voltage detected by the voltage detection means, and the electrical characteristics of the electric motor;
High-frequency component removing means for removing the high-frequency component of the rotational speed estimated by the second estimating means;
Have
An electric power steering apparatus characterized in that a rotational speed of the electric motor is estimated based on an output result of the low frequency component removing means and an output result of the high frequency component removing means.   The first estimating means multiplies the actual current detected by the current detecting means by a torque constant of the electric motor and a reciprocal of the inertia of the electric motor, and an output result of the calculating means The electric power steering apparatus according to claim 1, further comprising an integrating unit that integrates.   The second estimating means includes first multiplying means for multiplying the actual current detected by the current detecting means and the armature resistance of the electric motor, and the first multiplication from the voltage detected by the voltage detecting means. 3. The subtracting means for subtracting the output result of the means, and the second multiplying means for multiplying the output result of the subtracting means by the reciprocal of the induced voltage constant of the electric motor. Electric power steering device.   The electric power steering apparatus according to any one of claims 1 to 3, wherein the low-frequency component removing unit is a high-pass filter, and the high-frequency component removing unit is a low-pass filter.   The electric power steering apparatus according to claim 4, wherein a cutoff frequency of the high-pass filter is higher than a cutoff frequency of the low-pass filter. A rotational speed estimation device that estimates the rotational speed of an electric motor that applies steering assist force to a steering wheel,
Current detection means for detecting an actual current supplied to the electric motor;
Voltage detecting means for detecting a voltage between terminals of the electric motor;
First estimation means for estimating the rotational speed of the electric motor based on the actual current detected by the current detection means and the mechanical characteristics of the electric motor;
Low frequency component removing means for removing the low frequency component of the rotational speed estimated by the first estimating means;
Second estimation means for estimating the rotation speed of the electric motor based on the actual current detected by the current detection means, the voltage detected by the voltage detection means, and the electrical characteristics of the electric motor;
High-frequency component removing means for removing the high-frequency component of the rotational speed estimated by the second estimating means;
Adding means for adding the output result of the low frequency component removing means and the output result of the high frequency component removing means;
A rotational speed estimation device comprising: A rotational speed estimation method for estimating a rotational speed of an electric motor that applies steering assist force to a steering wheel,
Detecting the actual current supplied to the electric motor;
Detecting the voltage across the terminals of the electric motor;
Based on the value obtained by removing the low frequency component of the rotational speed estimated based on the detected actual current and the mechanical characteristics of the electric motor, the detected actual current, the detected voltage, and the electrical characteristics of the electric motor A rotational speed estimation method, wherein a rotational speed is estimated by adding a value obtained by removing a high-frequency component of the estimated rotational speed.

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