JP5011700B2 - Power steering electric drive - Google Patents

Description

The present invention provides a base assist command determining means for determining a base assist command based on a detected steering torque or a reference torque and a vehicle speed as a processing signal in order to give an assist torque to a steering operation of a steering wheel; The present invention relates to a power steering electric drive device for a vehicle including an assist motor and an electric motor drive control device that drives and controls the electric motor using an output of a base assist command determination unit.

This type of conventional power steering electric drive device is, for example, a final torque command for determining a current command of an assisting motor as disclosed in Japanese Patent Application Laid-Open Nos. 2002-249063 and 2003-285552. Is simply added to the base assist command with various compensation torque commands such as mechanical inertia compensation torque command, steering wheel return compensation torque command, damping compensation torque command, etc. there were. As a matter of course, in order to generate a conventional parallel-coupled final torque command, it is necessary to generate various compensation torque commands to be added in parallel, and these have been individually considered and generated. . The simple addition of various compensation torque commands that are considered and generated individually makes the final torque command more complicated in the feedback system because the various compensation torque commands are actually closely related to each other in the feedback system. . As a result, the overall tuning of various compensation torque commands for the driver to obtain a comprehensively good steering feeling is very complicated, and the achievement of the best steering feeling is practically contrary to the existence of the tuning function. Was almost impossible.

Problems to be solved by the invention

The present invention has been made under the above-mentioned background, and its purpose is to generate a base assist command that should originally be a base in a form that is more complete than the original, and to add additional compensation torque commands. An object of the present invention is to provide a power steering electric drive device that can be minimized and, by extension, can easily obtain a desired steering feeling for the steering wheel.

Means for solving the problem

In order to achieve the above object, according to the first aspect of the present invention, a base torque command or a base assist command which is a base current command based on the steering torque or a reference torque which is a processing signal and a vehicle speed is provided. In a power steering electric drive device for assisting steering, comprising a base assist command determining means for determining, an assisting motor, and an electric motor drive control means for driving and controlling the assisting motor using the base assist command. The base assist command determining means includes a dynamic amplitude amplifying means for amplifying the amplitude according to at least the frequency of either the steering torque or the reference torque, and a static amplitude for amplifying the amplitude according to the amplitude of the processing target signal and the vehicle speed. Amplifying means is provided in a form coupled in series .

Furthermore, the invention according to claim 1 is configured such that the dynamic amplitude amplifying means is configured using a dynamic amplitude amplifier having a continuous time transfer function having a relative degree of 1 or more or an equivalent discrete time transfer function. Features.

The invention according to claim 2 is the power steering electric drive device according to claim 1, wherein the dynamic amplitude amplifying means further generates a coefficient signal from the setting signal, and the coefficient of the dynamic amplifier is obtained from the coefficient signal. The coefficient determiner includes a storage unit capable of storing and storing the coefficient of the dynamic amplifier determined by the setting signal, and an input unit that controls an interface function for transmitting the setting signal to the storage unit And an output unit that controls an interface function for transmitting the coefficient of the dynamic amplifier stored and stored in the storage unit to the dynamic amplifier.

The invention according to claim 3 is the power steering electric drive device according to claim 1 or 2 , wherein the assist motor is an AC motor whose input power to the motor is AC power. It is characterized by doing.

Next, the operation of the present invention will be described. According to the first aspect of the present invention, the base assist command determination means performs dynamic amplitude amplification means for performing amplitude amplification according to at least the frequency of the processing target signal, and performs amplitude amplification according to the amplitude of the processing target signal and the vehicle speed. The static amplitude amplifying means is provided in a form coupled in series.

In the conventional techniques disclosed in JP-A-2002-249063, JP-A-2003-285752, etc., the base assist command determination means has only static amplitude amplification means. That is, the base assist command is determined by the static amplitude amplifying means based on the steering torque or the reference torque and the vehicle speed as the processing signal. This static amplitude amplifying means performs base assist as an output signal in accordance with input / output characteristics (input signal: steering torque or reference torque, vehicle speed, output signal: base assist command) prepared in advance for the input signal. The directive was to be determined. The mapped input / output characteristics at this time focus only on the static characteristics (static amplitude magnitude) of the input signal. In other words, only steady state characteristics are considered.

However, the steering feeling greatly depends on the dynamic characteristics resulting from the change of the input signal. According to the first aspect of the present invention , the power steering electric drive device includes the dynamic amplitude amplifying means in addition to the static amplitude amplifying means. This dynamic amplitude amplification means performs amplitude amplification according to the dynamic characteristics of the input signal (synonymous with amplitude amplification according to frequency; hereinafter, amplitude amplification according to frequency is abbreviated as “frequency amplitude amplification”). As a result, it becomes possible to provide a steering feeling that is impossible or difficult with the static amplitude amplifying means. As will be apparent to those skilled in the art from the above description , according to the first aspect of the present invention , the base assist can provide a steering feeling that is impossible or difficult to generate only by the static amplitude amplifying means. The effect is that the command can be determined. In addition, there is also an effect that this can be performed only by the dynamic amplitude amplification means, that is, in a unified manner.

Furthermore, in the invention described in claim 1 , the dynamic amplitude amplification means is configured using a dynamic amplitude amplifier having a continuous time transfer function having a relative degree of 1 or more or a discrete time transfer function equivalent thereto. . The continuous time transfer function having a relative order of 1 or more of the dynamic amplitude amplifier can be given by the following equation (1).

Here, s is a Laplace operator (complex number). The relative order of the continuous-time transfer function shown in the equation (1) (that is, the order difference = denominator order−numerator order) is clearly 1 or more. By selecting the coefficient of the upper order of the numerator as zero, the relative order can be increased without difficulty. An amplitude amplification characteristic corresponding to the frequency (hereinafter abbreviated as frequency amplitude amplification characteristic) is immediately obtained by replacing the complex number s with the imaginary number jω. That is,

FIG. 3 shows an example of frequency amplitude amplification characteristics of the denominator secondary and numerator primary (relative order is 1). The unit of the horizontal axis (frequency) in the figure is (rad / s), and the unit of the vertical axis (amplitude amplification) is dB. In this example, about 10 (dB) amplitude amplification is performed in the middle frequency range centered around 300 (rad / s), and the amplitude amplification is zero (dB) in the low frequency range, which is 1000 (rad / s) or more. On the contrary, in the high frequency range, an attenuation characteristic is given at −20 (dB / dec). Steering feeling with good response needs to have the required amplitude amplification characteristics in the middle frequency range. On the other hand, amplitude amplification in the high frequency range stimulates a noise component included in the detected steering torque. Therefore, amplitude amplification in the high frequency range is suppressed and amplitude attenuation is necessary. FIG. 3 is a simple example, but realizes a frequency amplitude amplification characteristic for obtaining such a good steering feeling.

ここに、ｚはｚ変換演算子（複素数）であり、Ｔｓはサンプリング周期である。連続／離散変換には、（３）式に代わって、前進差分、後進差分等の他のものを利用しても、もちろんかまわない。以上の説明より当業者には既に明らかなように、請求項２の発明によれば、良好な操舵フィーリングを得るための周波数振幅増幅特性（すなわち動的な振幅増幅特性）を、難なく実現できると言う作用が得られる。The attenuation characteristic in the high frequency region can be easily improved to −40 (dB / dec) and −60 (dB / dec) by increasing the relative order to the second order and the third order. In addition, the amplitude amplification characteristic from the low frequency range to the medium frequency range can be set in detail by increasing the order of the equation (1) and setting the coefficient associated therewith. A continuous-time transfer function having a required frequency amplitude amplification characteristic can be easily changed to a discrete-time transfer function through, for example, the continuous / discrete conversion shown in the following equation (3).

Here, z is a z conversion operator (complex number), and Ts is a sampling period. For the continuous / discrete conversion, it is of course possible to use other things such as forward difference, reverse difference, etc. instead of the expression (3). As will be apparent to those skilled in the art from the above description, according to the invention of claim 2, the frequency amplitude amplification characteristic (that is, dynamic amplitude amplification characteristic) for obtaining a good steering feeling can be realized without difficulty. Is obtained.

Subsequently, in the invention according to claim 3, the dynamic amplitude amplifying means includes a characteristic setting means for the steering person to set the characteristic of the amplitude amplification. As described in the first aspect of the present invention , the dynamic amplitude amplifying means has a function of determining a base assist command that can give a steering feeling in a unified manner. According to the second aspect of the present invention , the dynamic amplitude amplifying means includes the characteristic setting means. As a result, the steering wheel himself can set the steering feeling according to the preference of the steering wheel himself. The effect that it becomes will be obtained.

Next, an invention according to claim 3 will be described . As the assist motor, as shown in many prior inventions, at present, a DC motor whose input power to the motor is DC power is mainly used. The DC motor has a large motor moment of inertia due to mechanical limitations. When the DC motor is used as an assist motor, the moment of inertia seen by the steering wheel is unnecessarily increased. In addition, it is essential to construct a special pseudo inertia reduction circuit (a circuit for generating a motor inertia compensation torque command) for this purpose. On the other hand, an AC motor in which the input power to the motor is AC power has a characteristic that the motor moment of inertia is much smaller than that of a DC motor. By using an AC motor as an assisting motor in the power steering electric drive device according to any one of claims 1 and 2, it is possible to obtain an effect of suppressing an increase in the moment of inertia as viewed from the driver. As a result, it is possible to realize a power steering electric drive device that does not require a pseudo inertia reduction circuit (that is, suppresses additional addition of a compensation torque command). As a result, in the invention according to claim 1 or 2, Compared to the use of a DC motor , the effect of being more prominent can be obtained.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a typical embodiment of a power steering electric drive device using the present invention. The main devices constituting this electric drive apparatus are a base assist command determiner 1 that realizes a base assist command determination means, an assist motor 2, and an electric motor drive control that realizes an electric motor drive control means that controls the assist motor. Device 3. In this embodiment, an AC motor is used as the assisting motor.

When the steering is steered at a certain vehicle speed, the steering torque is detected by a steering torque detector, which is input to a base assist command determiner. Although depending on the dynamic characteristics of the entire system of the steering system, the detected steering torque may be input to the base assist command determiner after phase compensation through the phase compensator. In FIG. 1, the signal that has been phase compensated through the phase compensator is used as the reference torque. In addition, it is possible to switch between the steering torque and the reference torque to be input to the base assist command determiner. The vehicle speed at the time of steering is detected by a vehicle speed detector and input to a base assist command determiner. In the embodiment shown in FIG. 1, the setting signal is further input to the base assist command determiner according to the present invention. The description regarding the setting signal will be described later. The base assist command determiner receives these inputs and outputs a base assist command. In this embodiment, the base assist command is a base torque command.

If necessary, a compensation torque command is added to the base torque command to generate a final torque command, which is input to the motor drive control device 3. When a DC motor is used as an assisting motor, the moment of inertia seen from the steering wheel becomes unnecessarily large. Therefore, a special pseudo inertia reduction circuit (motor inertia compensation torque command for the increased inertia moment) is used to improve steering feeling. The construction of a circuit for generating The compensation torque command is an output signal from the pseudo inertia reduction circuit. When an AC motor is used as the assisting motor, the pseudo inertia reduction circuit is not necessarily required. In consideration of this point, in FIG. 1, the compensation torque command is indicated by a broken line.

When the motor drive control device obtains the final torque command, it drives and controls the assist motor to generate the assist torque that matches the final torque command. When an AC motor is used as the assisting motor, this drive control method is based on a vector control method. For the vector control of an AC motor such as a synchronous motor or an induction motor, position speed information of the rotor of the motor is required. This is detected by a resolver or the like attached to the rotor. In FIG. 1, a source signal including position / velocity information detected by a resolver or the like is shown as a drive assist signal. In the motor drive control device, a source signal is processed by a signal detector to obtain required position or speed information.

In an AC motor such as a synchronous motor or an induction motor, there is generally no linear relationship between a stator current and a generated assist torque. Although it is possible to maintain the linearity of the stator current and the generated assist torque by imposing special constraints on the stator current using the vector control method, it is generally effective when applying this control law. Will be damaged. The command converter in FIG. 1 plays a role of determining the current command of the stator current in consideration of efficiency. The main device in the motor drive control device 3 is composed of a vector-controlled inverter that generates AC power necessary for driving and controlling the assist motor from DC power obtained from a battery or the like. Since the vector control method for the efficient operation of the AC motor is already known to those skilled in the art, for example, in the following documents, further explanation is omitted.

Shinji Shinnaka: “Analysis by vector signal of salient pole type synchronous motor for efficiency-oriented current control”, IEEJ Transactions D, Vol. 119, no. 5, pp. 648-658 (1999-5) Shinnaka Shinji: “Practical optimum current command method considering iron loss for wide range and high efficiency operation of salient pole type permanent magnet synchronous motor”, IEEJ Transactions D, Vol. 123, no. 11, pp. 1360-1370 (2003-11) Shinnaka Shinji: “Minimum Loss Control Strategy for Induction Motors Having Iron Loss in Stator and Rotor”, IEEJ Transactions D, Vol. 118, no. 3, pp. 421-422 (1998-3)

The present invention in a power steering electric drive device is in a base assist command determiner 1 that implements a base assist command determination means. Hereinafter, the base base assist command determiner will be described in detail with reference to the drawings. FIG. 2 shows the internal structure of the base assist command determiner 1 according to the present invention. The base assist command determiner 1 is configured in the form of a serial combination of a dynamic amplitude amplifying unit 1-1 that implements dynamic amplitude amplifying means and a static amplitude amplifying unit 1-2 that implements static amplitude amplifying means. ing. The input signal to the base assist command determiner 1 is first subjected to amplitude amplification processing according to the frequency of the signal in the dynamic amplitude amplification unit 1-1, and the processed signal is output to the static amplitude amplification unit 1-2. The The static amplitude amplification unit performs static amplitude amplification on the processing signal in the dynamic amplitude amplification unit according to the amplitude and the vehicle speed, and uses this as a final processing signal (that is, as a base assist command). ) Output. The configuration of the static amplitude amplifying unit may determine the output signal for the input signal according to, for example, mapped static input / output characteristics. Since the configuration of the static amplitude amplifying unit according to the mapped static input / output relationship has already been disclosed in detail in JP-A-7-267109, JP-A-2001-260925, etc., further explanation is omitted. To do.

図４における１／ｓは積分器を意味している。また、６個の係数は可調整であり、同図ではこの可調整性を、係数を貫く貫徹矢印で表現している。The dynamic amplitude amplifier 1-1 includes a dynamic amplitude amplifier 1-1a and a coefficient determiner 1-1b. The dynamic amplitude amplifier directly performs an amplitude amplification process corresponding to the frequency on the input signal to the base assist command determiner 1, and the input / output transfer function has a relative order of 1 or more ( 1) It is expressed by the formula. A typical example of the frequency amplitude amplification characteristic is as shown in FIG. Since the transfer function and the frequency amplitude amplification characteristic have already been described in detail in connection with the operation of claims 2 and 3 of the present invention, further description thereof will be omitted. FIG. 4 shows an example of a more detailed configuration of the dynamic amplitude amplifier. The configuration example of this figure is one configuration example for the following denominator tertiary and numerator secondary transfer functions.

1 / s in FIG. 4 means an integrator. In addition, the six coefficients are adjustable, and in the figure, this adjustability is expressed by penetrating arrows that penetrate the coefficients.

The coefficient determiner 1-1b determines a coefficient in the dynamic amplitude amplifier 1-1a. More specifically, the coefficient of the dynamic amplitude amplifier is determined by the coefficient signal generated by the coefficient determiner. In order to clarify the relationship of the coefficient determination of the dynamic amplitude amplifier by the coefficient determiner, in FIG. 2, this is indicated by a penetrating arrow to the dynamic amplitude amplifier by the coefficient signal. Further, in FIG. 4 showing one example of realization of the dynamic amplitude amplifier, it is indicated by a penetrating arrow to the coefficient of the dynamic amplitude amplifier. Of course, the penetrating arrow in FIG. 4 means a coefficient signal.

FIG. 5 shows an example of the internal structure of the coefficient determiner 1-1b. The coefficient determiner of this example includes an input device 1-1b1, a storage device 1-1b2, an output device 1-1b3, and an indicator 1-1b4. The coefficient of the dynamic amplitude amplifier set by the setting signal is temporarily stored and stored in the storage device. Thereafter, the stored and stored coefficients are output as coefficient signals to the dynamic amplitude amplifier. The input device and the output device are means for controlling the interface function for this purpose. According to this configuration having a storage device having a storage / storage function, once the steering wheel sets a desired coefficient, it is not necessary to input the setting every time the steering is performed, and practical driving is possible. . When a plurality of steering persons steer the same vehicle, a coefficient stored in advance may be output as a coefficient signal according to the steering person. The indicator 1-1b4 has a function for this purpose. That is, the indicator is a means for managing a function for inputting, storing, and outputting a coefficient corresponding to the steering person. The function of the present indicator makes it possible to immediately realize a steering feeling according to the preference of the steering even when a plurality of steerings steer the same vehicle.

The power steering electric drive device according to the present invention has been described specifically and in detail with reference to various drawings. The base assist command determiner, which is the main object of the present invention, can be realized in an analog manner, but it is preferable that the base assist command determiner be configured digitally in view of the remarkable progress of recent digital technology. The configuration example of the dynamic amplitude amplifier shown in FIG. 4 is for an analog configuration, but the digital configuration is equivalent to this. In order to convert the analog configuration to the digital configuration, for example, the integrator in FIG. 4 may be discretely realized using the relationship of continuous / discrete conversion exemplified in Equation (3). Although the digital configuration includes a hardware configuration and a software configuration, as will be apparent to those skilled in the art, any of the present invention can be configured.

In the embodiment using FIG. 1, an AC motor is used as the assist motor. However, the base assist command determiner according to the present invention can also use a DC motor as the assist motor. In the case of a DC motor, since the current to the motor and the generated assist torque are in a proportional relationship, the base assist command may be a base current command instead of the base torque command. This also reduces the amount of calculation slightly. Naturally, when using a DC motor, the electric drive control device for the DC motor does not require detection of rotor position speed information using a resolver or the like.

It should be pointed out that the power steering electric drive device according to the present invention can be applied to various types of power steering including a column assist type, a rack assist type, and a pinion assist type.

The invention's effect

As is clear from the above description, the present invention has the following effects. According to the first aspect of the present invention, it is possible to determine a base assist command that can provide a steering feeling that is impossible or difficult to generate only by the static amplitude amplifying means. In addition, there is also obtained an effect that this can be performed only by the dynamic amplitude amplification means of the present invention, that is, in a unified manner. As a result of this operation, according to the first aspect of the present invention, it is possible to obtain an effect that the base assist command can be generated in a unified manner with a high degree of completeness considering the steering feeling from the beginning.

Furthermore, the invention according to claim 1 has an effect that a frequency amplitude amplification characteristic (that is, a dynamic amplitude amplification characteristic) for obtaining a good steering feeling can be realized without difficulty. As a result of this action, the invention according to claim 1 has an effect that a good steering feeling can be easily imparted in generating the base assist command.

In the invention according to the second aspect, there is obtained an effect that the steering wheel himself can set the steering feeling according to the preference of the steering wheel himself. Further, as described in detail in the embodiment using FIG. 5, it is only necessary to set a desired steering feeling once through a dynamic amplitude amplifier coefficient or the like. Further, even when a plurality of steering persons steer the same vehicle, it is possible to cope with each steering person. As described above, in the invention according to claim 2, in the base assist command generation, it is possible to obtain an effect that the steering wheel can easily obtain the steering feeling according to the individual desires of the steering wheel. It becomes like this.

According to the third aspect of the present invention, an effect of suppressing an increase in the moment of inertia viewed from the steering person is obtained. As a result, in the invention according to claim 1 or claim 2 , the effect that the effect can be more conspicuous is obtained as compared with the use of the DC motor. As a result of this adoption, according to the invention described in claim 3, the effect of the invention described in either claim 1 or claim 2 can be further enhanced (that is, additional compensation torque command is added). The effect that no addition is required) can be obtained.

Block diagram showing one configuration example of a power steering electric drive device 1 is a block diagram showing a configuration of a base assist command determiner in an embodiment. The figure which shows one example of the frequency amplitude amplification characteristic of a dynamic amplitude amplifier 1 is a block diagram illustrating a configuration of a dynamic amplitude amplifier according to an embodiment. 1 is a block diagram showing a configuration of a coefficient determiner in an example embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base assist instruction | command determination device 1-1 Dynamic amplitude amplifier 1-1a Dynamic amplitude amplifier 1-1b Coefficient determination device 1-1b1 Input device 1-1b2 Storage device 1-1b3 Output device 1-1b4 Indicator 1-2 Static amplitude amplifying unit 2 Assist motor 3 Motor drive control device

Claims (3)

Base assist command determining means for determining a base torque command or a base assist command that is a base current command based on the steering torque or a reference torque and a vehicle speed as a processing signal, an assisting motor, and the base assist command In a power steering electric drive device that assists steering with an electric motor drive control means for controlling the driving of the assist electric motor using
The base assist command determination means includes
A dynamic amplitude amplifying means for performing amplitude amplification in accordance with at least the frequency of either the steering torque or the reference torque and a static amplitude amplifying means for performing amplitude amplification in accordance with the amplitude of the signal to be processed and the vehicle speed are connected in series. In a combined form, prepared,
The dynamic amplitude amplification means uses a dynamic amplitude amplifier having a continuous time transfer function having a relative degree of 1 or more or a discrete time transfer function equivalent to the continuous time transfer function . The dynamic amplitude amplification means further includes:
A coefficient determiner that generates a coefficient signal from a setting signal and determines a coefficient of the dynamic amplifier according to the coefficient signal;
The coefficient determiner includes a storage unit capable of storing and storing the coefficient of the dynamic amplifier determined by the setting signal;
An input device that controls an interface function for transmitting the setting signal to the storage device;
An output unit that controls an interface function for transmitting the coefficient of the dynamic amplifier stored and stored in the storage unit to the dynamic amplifier;
The power steering electric drive device according to claim 1, comprising: 3. The power steering electric drive device according to claim 1, wherein the assist motor is an AC motor whose input power to the motor is AC power. 4.

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