JP2001233234A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering device properly securing data of a variable resistance value R, accurately carrying out estimation computing of the number of revolution ωon the basis of the data, and appropriately achieving control using the number of revolutions ω. SOLUTION: A control circuit 2 is provided with a function of correcting the resistance value R according to a motor temperature t (motor resistance correcting part 6; steps S1-S3) and a function of computing the resistance R from a voltage and a current by determining a steering holding condition and assuming ω=0 (a motor resistance learning part 7 and the like; steps S11-S23) or a function of computing the resistance R from a voltage and a current before/after a current change by determining a stable steering state and carrying out current reducing control (the motor resistance learning part 7a; steps S31-S45).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric power steering apparatus for generating a steering assist torque in a vehicle, and accurately estimates and calculates a motor rotation speed required for a rotation speed responsive control of an assist motor in a control unit. The present invention relates to an inexpensive and highly mountable electric power steering device.

[0002]

2. Description of the Related Art In general, an electric power steering device used for a small vehicle such as a mini car detects a steering torque generated on a steering shaft by operating a steering wheel with a torque sensor (steering torque detecting means). A current is supplied to an assist motor (hereinafter, sometimes simply referred to as a motor in some cases) attached to a steering shaft or the like to generate a steering assist torque.
To control the current of the assist motor for this purpose, an H-bridge circuit usually composed of four FETs (field-effect transistors) is used, and the PWM control of the assist motor is performed via a drive circuit (motor driving means) composed of the H-bridge circuit.
(Pulse width modulation) method. Then, a current command value is calculated in accordance with the detected steering torque. For example, a current control signal (for example, a signal for determining a duty ratio of the PWM drive) based on the current command value and an actual assist motor current value The current value of the assist motor is controlled to a preferable value according to the steering torque by a normal one-loop feedback control that corrects the current control signal in accordance with the difference (deviation) from the above. Here, the calculation of the current command value, the generation of the current control signal including the feedback control processing, and the like are normally performed by a control circuit including a microcomputer.

[0003] In this type of device, there is an increasing tendency to mount it on a large vehicle (for example, a small car or a normal car) in which the motor current is much larger than that of a mini car. In order to cope with the problem that becomes remarkable, it is necessary to perform more advanced motor control (current control and the like) in consideration of the number of rotations of the motor. For example, in an operation in which the motor rotates temporarily in a direction opposite to the steering direction (for example, at the time of operating the steering wheel end), the energizing direction of the motor is temporarily changed to the rotational direction while a considerable steering torque is generated. Therefore, it is known that the induced voltage of the motor acts in a direction to further increase the current, and a large spike-like current flows instantaneously. For such an instantaneous large current, it is impossible to cope only with the control by the current control signal based on the current command value (corresponding to the steering torque). It is necessary to cope with this by performing a rotational speed sensitive control as described above. In this rotation speed sensitive control, the above-described control circuit determines such a normally uncontrollable steering state (a state in which the energizing direction of the motor is opposite to the rotation direction), and determines whether the steering is not normally performed by the PWM drive. Are driven by PWM with a duty ratio that cancels out the current of the induced voltage (that is, the motor rotation speed) (that is, the motor is driven normally). This is excellent in that the drive output of the motor is attenuated by the number of revolutions) to positively suppress the spike-like large current.

In this type of apparatus, more advanced motor control (current control, etc.) in consideration of the number of rotations of the motor may be performed in order to improve the steering feeling.
For example, control may be added by negative feedback of the steering wheel angular velocity (that is, the motor rotation speed) in order to increase the responsiveness of the steering wheel operation during high-speed running or the like. This is to reduce the magnitude of the motor current (that is, the steering assist torque) according to the magnitude of the steering wheel angular velocity, and in some cases, to generate a steering assist torque in a direction opposite to the steering torque. Is made more preferable according to the vehicle speed or the like.

However, in such control using the motor rotation speed, it is naturally necessary to obtain data of the motor rotation speed with a required degree of accuracy. If the data becomes inaccurate, problems such as the spike-like large current being unable to be sufficiently suppressed and the drive output being excessively attenuated, for example, not generating the necessary steering assist torque may be caused. However, providing a rotation sensor (for example, a sensor for detecting a rotation angle or a rotation angular velocity of a motor, or a sensor for detecting a rotation angle or a rotation angular velocity of a steering wheel or a steering shaft) for detecting a motor rotation speed for that purpose, It is difficult from the viewpoints of cost and mountability to a vehicle (easiness of assembling the device and miniaturization), and there is a strong demand in the market for a configuration without a rotation sensor without such a rotation sensor. This is because, if such a rotation sensor is to be provided, the cost of the sensor itself is added to the cost of the apparatus, and a space for disposing the sensor itself is required in the vehicle, and the above-described drive circuit in the vehicle is required. From the control unit in which the control circuits are stored to the place where such sensors are arranged (for example, the place where the assist motor is arranged), the troublesome work of laying signal lines and power lines for the sensors, This is because more space is required for laying the signal lines and the like.

In recent years, for example, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent No. 59463, in an arithmetic circuit (for example, a control circuit including the above-described microcomputer) in the control unit, the following equation (1) is obtained from the motor current IM, voltage VM (applied voltage), and resistance value R. ), It is proposed to estimate and calculate the rotational speed ω of the motor in real time. K is an induced voltage constant of the motor. ω = 1 / K · (VM−R · IM) (1) Further, in the above-mentioned publication, the resistance value R used in the calculation of the above equation (1) is defined as that the rotational speed ω is zero. There has been proposed a technique of determining (i.e., being in a steering-holding state) and appropriately calculating the following equation (2) obtained as ω = 0 in the above equation (1). R = VM / IM (2)

[0007]

However, in the above-described conventional power steering apparatus, as described in the above-mentioned publication, the fact that the rotation speed ω is zero by the rotation detecting means such as a steering angle sensor is disclosed. Or if the current control signal (motor current signal) of the motor exceeds the maximum value (maximum target current signal) in normal steering, it is determined that the rotational speed ω is zero, and the resistance The calculation for obtaining the value R was performed. Therefore, there are the following problems. That is, when the rotation detecting means such as the steering angle sensor is used, the rotation sensor ω is calculated and estimated without any difficulty, but the rotation sensor is not required. This leads to deterioration in mountability on vehicles. Furthermore, if there is a steering angle sensor, the value of the rotational speed ω can be obtained by differentiating the output of the steering angle sensor, but the process of estimating the rotational speed ω and calculating the rotational speed ω is uselessly. Has become.

In any case, unless the rotational speed ω becomes zero, the latest value of the resistance value R cannot be obtained, so that the resistance value R is corrected or updated to a more correct value at that time. There is a disadvantage that the frequency of learning to be registered cannot be sufficiently high, and the change in the resistance value R due to temperature cannot be sufficiently reflected. The change in the resistance value of the motor due to aging is generally moderate, but the change (or fluctuation) due to the temperature is relatively large in a relatively short time. Therefore, in order to sufficiently reflect the change in the resistance value caused by the temperature, more frequent learning of the resistance value R is required. In the conventional configuration, such frequent learning cannot be performed, or It was not enough. In particular, in the configuration in which the rotation speed ω is determined to be zero when the current control signal exceeds the maximum value, the state where the rotation speed ω is actually zero cannot be determined every time, and is usually rarely performed. Such a special operation (that is, an operation in which steering is maintained at the rack end as described in the above-mentioned publication) is performed, and the rotational speed ω
The learning of the resistance value R based on the estimation calculation of the resistance value R is realized only when the value of the resistance value R becomes zero. Therefore, the learning frequency is extremely low and insufficient.
Is reflected in the estimation calculation of the rotational speed ω,
In practice it is almost impossible. Therefore, in summary, in the related art, with the configuration without the rotation sensor, it is not possible to appropriately secure the data of the resistance value R that constantly changes or fluctuates, and to execute the estimation calculation of the rotation speed ω sufficiently accurately based on this data. Was. Therefore, the present invention performs a rotation sensorless configuration and performs a sufficiently accurate estimation calculation of the rotational speed ω based on the data while properly securing the resistance value R data.
It is an object of the present invention to provide an electric power steering device having excellent functions to accurately realize various controls using the rotational speed ω.

[0009]

An electric power steering apparatus according to a first aspect of the present invention is connected to a steering system of a vehicle for generating a steering assist torque, and detects a steering torque of the steering system. An electric power steering apparatus, comprising: a steering torque detection unit, and a control unit that controls the assist motor based on a parameter including at least a steering torque detection value obtained by the steering torque detection unit and a rotation speed of the assist motor. The control unit, a motor voltage detecting means for detecting an applied voltage to the assist motor, a motor current detecting means for detecting a current flowing in the assist motor,
Motor temperature output means for outputting a detected temperature value or an estimated temperature value of the assist motor; resistance value storage means for storing a resistance value of the assist motor; and a detected temperature value or temperature output from the motor temperature output means. A motor that corrects the resistance value stored in the resistance value storage means as needed based on an estimated value based on a preset temperature characteristic, and registers the corrected resistance value in the resistance value storage means. Resistance value correcting means, a voltage and a current detected by the motor voltage detecting means and the motor current detecting means,
And a rotational speed calculating means for estimating and calculating the rotational speed from the latest resistance value stored in the resistance value storing means.

The "resistance value storage means", "motor resistance value correction means", and "rotation speed calculation means" are realized by a circuit including a microcomputer and a program registered in a ROM or the like. In addition, the above "control unit"
Is, for example, a motor driving means for controlling the motor (for example, the above-described H-bridge circuit), and a predetermined control signal (for example, a current control signal) is output to the motor driving means to operate the motor (for example, The magnitude and direction of the current)
And a motor control means (for example, a circuit including a microcomputer) for controlling the resistance value.
"Motor resistance value correction means" and "rotation speed calculation means"
Is the same circuit as this motor control means (common CPU)
May be realized. The "motor voltage detecting means" is, for example, a circuit (a resistor for voltage division or a voltage dividing resistor) for detecting a potential difference between motor connection terminals (both terminals connected to both ends of the motor coil) in the above-described H-bridge circuit as a motor voltage value. A filter circuit for shaping the waveform). The “motor current detecting unit” detects, for example, a potential difference between both terminals of a shunt resistor connected to a power line (for example, a low-potential-side power line) of the H-bridge circuit as a motor current value. A filter circuit for shaping the waveform).

The "motor temperature output means" receives a detection signal from, for example, a temperature sensor attached to the motor, and amplifies the detection signal or performs noise removal processing as necessary to indicate the motor temperature. It is a circuit that outputs a signal (temperature detection value). Or this "motor temperature output means"
In a known method, for example, as disclosed in JP-A-4-71379, for example, the motor temperature is estimated and calculated from the current value detected by the motor current detection means,
A means for outputting the calculation result (temperature estimation value) (for example, a circuit including a microcomputer and a program registered in a ROM or the like thereof) is provided. In this case, the circuit for performing the temperature estimation calculation may be realized by the same circuit as the motor control means. Also, "correcting the resistance value as necessary" means that the stored resistance value is determined to be in an appropriate range based on the temperature detection value or temperature estimation value at that time, This means that the motor resistance value correction means does not necessarily need to execute the correction. The estimation of the rotational speed by the rotational speed calculating means may be performed, for example, periodically, but is not necessarily limited to the periodicity. The necessity of the control using this (for example, the above-described rotational speed sensitive control) is necessary. May be appropriately performed based on the latest resistance value (the same applies to other inventions described later). Further, the correction by the motor resistance value correction means may be, for example, performed periodically and the resistance value (at least the latest one) after the sequential correction is registered (stored). When performing the estimation calculation of (i.e., only when necessary), the calculation may be performed prior to the calculation.

The registration of the corrected resistance value into the resistance value storage means may be an update registration in which the resistance value before correction is erased and the same area is deleted, or the resistance value before correction is stored in the same area, for example. The information may be registered in another area while keeping the reference value. Further, the registration of the corrected resistance value does not necessarily have to be registered in the nonvolatile memory. If the resistance value as the reference value remains, it is temporarily used for the rotational speed estimation calculation. It may be a memory to be performed. In the case of erasing the resistance value before correction and registering the resistance value after correction, the data of the motor temperature used for the correction is grasped in association with the data of the resistance value after correction. It needs to be in a state. This is because if it is not known how many times the resistance value corresponds to the motor temperature, the position on the temperature characteristic diagram is not determined and subsequent temperature correction cannot be performed. The same applies to the resistance value (initial value), which is the reference initially registered in the resistance value storage means. The “latest resistance value” used in the rotation speed estimation calculation is a resistance value (initial reference value) registered as an initial value if correction has not been performed yet, and Is performed once or more and the corrected resistance value is stored, it is the resistance value after the correction performed last.

According to the present invention, the motor resistance value correction means performs the above-described correction at any time, for example, at a constant cycle. Since the learning for the fluctuation can be performed with sufficient frequency, the accuracy and reliability of the rotation speed estimation calculation by the rotation speed calculation unit can be improved without increasing the cost of the device or deteriorating the mountability of the vehicle. In addition, the accuracy and effectiveness of motor control (for example, the above-described rotational speed responsive control) using the estimated value of the rotational speed can be significantly improved. In this case, since a rotation sensor is not required at all, wiring for the rotation sensor (signal line between the control unit and the rotation sensor) is not required. The voltage and current used for the rotation speed estimation calculation by the rotation speed calculation unit are detected by, for example, the motor voltage detection unit and the motor current detection unit realized by the circuit in the control unit as described above. Since a sensor is used, there is no need to provide a sensor for detecting the voltage or the current or wiring for the sensor outside the control unit. When the motor temperature is estimated and calculated as described above, it is not necessary to attach a temperature sensor to the motor, and wiring for the temperature sensor (such as a signal line between the control unit and the temperature sensor) is not required. Become. Therefore,
It is possible to realize an inexpensive device with high vehicle mountability, in which the number of sensors and the number of wires outside the control unit are significantly reduced.

According to a second aspect of the present invention, there is provided an electric power steering apparatus similar to the first invention, wherein the control unit detects a voltage applied to the assist motor. Detecting means, motor current detecting means for detecting a current flowing through the assist motor, resistance value storing means for storing a resistance value of the assist motor, and at least a fluctuation amount of the steering torque detected value is equal to or less than a predetermined value. And, on condition that the amount of change in the load of the assist motor is equal to or less than a predetermined value, a steering state determining unit that determines that the vehicle is in a steering state, and at least a steering state by the steering state determining unit. Is determined on condition that the voltage and the voltage detected by the motor voltage detecting means and the motor current detecting means are Motor resistance calculating means for estimating and calculating the resistance value of the assist motor from the current assuming that the rotation speed is zero, and using the resistance value obtained by the motor resistance value calculating means as a new resistance value, Resistance value storage processing means registered in the storage means, the voltage and current detected by the motor voltage detection means and the motor current detection means, and the rotation from the latest resistance value stored in the motor resistance value storage means. And a rotational speed calculating means for estimating and calculating the number.

Here, the "resistance value storage means", "steering state determination means", "motor resistance value calculation means", "resistance value storage processing means" and "rotation speed calculation means" are, for example, microcomputers. It may be realized by a circuit including the same and a program registered in a ROM or the like, and may also be realized by the same circuit as the above-described motor control means. Further, the estimation calculation of the resistance value by the motor resistance value calculation means does not necessarily need to be performed every time when the steering state determination means determines that the vehicle is in the steering state. The estimation calculation by the motor resistance value calculation means is based on the above-described equation (2). Further, the update registration of the resistance value by the resistance value storage processing means may be executed unconditionally when the estimation calculation of the resistance value is executed by the motor resistance value calculation means. May be executed only when the difference between the resistance value and the storage value of the resistance value storage means exceeds a prescribed allowable value (the same applies to a third invention described later). The "variation in the load of the assist motor" is output from the motor control means described above, the variation in the estimated rotational speed, the variation in the detected current value, the variation in the detected voltage value. The amount of fluctuation of the current control signal can be used (the same applies to a third invention described later). Also,
The registration of the resistance value obtained by the motor resistance value calculation means by the resistance value storage processing means may be an update registration in which the previous resistance value is erased and the same area is erased, or another area while the previous resistance value is retained. May be registered (the same applies to a third invention described later). Further, the “latest resistance value” used in the rotation speed estimation calculation means that when there are a plurality of resistance values obtained and registered by the motor resistance value calculation means,
If it is the latest one of them and the calculation of the resistance value has not been performed yet, it is the resistance value (initial reference value) registered as an initial value (the same applies to a third invention described later). .

According to the present invention, the steering state determination means includes:
The fluctuation amount of the detected steering torque value is equal to or smaller than a predetermined value (for example, zero or less), and the fluctuation amount of the assist motor load is equal to or less than a predetermined value (for example, zero or less). It is determined that the vehicle is in the steering-holding state on the condition that this is the case. That is, a state in which the amount of torque fluctuation and the amount of load fluctuation are small is a condition for determining whether the steering is maintained. Such a condition
Since the rotation speed ω can be almost zero (steering state) (because it is difficult to rotate the steering wheel while keeping the torque variation and load variation small), the steering state can be maintained with considerable accuracy. In addition, the state is not necessarily limited to a special state such as at the time of operating the handle end (at the end of the rack), and a state where the rotational speed ω is actually zero can be widely determined. For this reason, despite the rotation sensorless configuration,
The frequency of calculating and estimating the resistance value by the motor resistance value calculating means performed based on the determination of the steering holding state (i.e., the learning frequency of the latest resistance value including the temperature change and the aging change) is much more than before. It is possible to improve the accuracy and reliability of the rotation speed estimation calculation by the rotation speed calculation means without increasing the cost of the device or deteriorating the mountability of the vehicle. The accuracy and effectiveness of the control of the used motor (for example, the above-described rotational speed sensitive control) can be remarkably improved. Also in this case, since the rotation sensor is completely unnecessary, wiring (signal lines between the control unit and the rotation sensor, etc.) for the rotation sensor is also unnecessary, and the sensor for detecting the voltage and the current (and, in some cases, the motor temperature). There is no need to provide a wiring for this purpose outside the control unit, as in the first aspect. Therefore, an inexpensive device with high vehicle mountability, in which the number of sensors and the number of wires outside the control unit are significantly reduced, can be realized.

In a preferred aspect of the present invention, the condition that the steering state determination means determines that the vehicle is in the steering state is that a current detected by the motor current detection means is equal to or more than a predetermined value. Are further added. In this case, the determination of the steering holding state becomes more reliable. This is because the motor current is basically controlled in accordance with the steering torque. In this case, the fact that the current is considerable (above the predetermined value) means that the steering torque is considerably large. It is. Since it is very difficult to rotate the steering wheel with a considerable amount of steering torque while maintaining the torque variation and the load variation very small, the torque variation and the load variation are very small and the steering It is very unlikely that there is a considerable amount of torque other than in the steering-holding state. For this reason, the determination of the steering holding state becomes more reliable, and the accuracy of the above-described resistance value estimation calculation and the accuracy of the rotation speed estimation calculation using the resistance value estimation value are further improved. The control of the motor using the estimated value of the rotation speed becomes more accurate. By the way, if there are tires on the road surface with extremely low resistance such as ice burn,
Although it is possible to rotate the steering wheel while keeping the amount of torque fluctuation and the amount of load fluctuation small, even in such a situation, it is not possible to rotate the steering wheel while further maintaining the steering torque at a considerable amount. In this mode, even in a special situation, there is very little possibility that an erroneous steering determination (actually, a determination that the steering speed is not zero but the steering is maintained) will be made. .

The "predetermined value" (the above-described threshold value of the current for judging the hold) in the present embodiment is set to a value as large as possible in order to achieve the above-described effects at a higher level. However, if this value is set too large, the frequency of the steering determination (that is, the frequency of learning the latest resistance value) tends to decrease. Should be set. At least, it is necessary to avoid setting the current to be equal to or more than the maximum current value of the motor as in the related art. However, as described later, when the concept of the first invention of the present application described above is combined with the idea of the second invention, it is not necessary to consider the above-described problem of a decrease in the learning frequency, and the “default value” is not provided. It is preferable that the condition be set to a large value (in this case, the maximum current value may be used). That is, if the temperature correction according to the first aspect of the invention is performed, it is not necessary to perform the learning on the temperature change, and the motor current value gradually changes over time (initial variation for each product) or a long time. This is because the latest resistance value estimation calculation may be performed only to reflect the influence of aging.

In another preferred aspect of the present invention, the condition for the motor resistance value calculating means to execute the estimation calculation is such that the steering state determination means determines that the vehicle is in a steering state. It is further added that the time has exceeded the prescribed time. In this case, the accuracy of the calculation for estimating the resistance value is further improved, and the accuracy of the calculation for estimating the rotational speed using the estimated value of the resistance value is further improved. Control becomes more accurate. This is because there is no possibility that the above-described condition of the hold determination is instantaneously satisfied even though the steering is not held, and the estimation calculation of the resistance value is executed.

According to a third aspect of the present invention, there is provided an electric power steering apparatus similar to the first or second aspect, wherein the control unit controls a current flowing through the assist motor. Motor voltage detecting means for detecting a voltage applied to the assist motor; motor current detecting means for detecting the current; resistance value storing means for storing a resistance value of the assist motor; and at least the steering torque detected value. Is less than or equal to a predetermined value, the amount of change in the load of the assist motor is less than or equal to a predetermined value, and provided that the current detected by the motor current detecting means is equal to or greater than a predetermined value. A stable steering state determining means for determining that the vehicle is in a stable steering state, and at least the stable steering state is determined by the stable steering state determining means. Current reduction control means for temporarily and forcibly changing the control signal of the motor drive means in a direction in which the magnitude of the current decreases, and Motor resistance value calculation for estimating and calculating the resistance value of the assist motor from the voltage and the current detected by the motor voltage detection means and the motor current detection means before and after the start of the change, assuming that the change in the rotation speed is zero. Means, a resistance value storage processing means for registering the resistance value obtained by the motor resistance value calculation means in the resistance value storage means as a new resistance value, and a resistance value detected by the motor voltage detection means and the motor current detection means. The rotation speed is estimated and calculated from the voltage and the current, and the latest resistance value stored in the motor resistance value storage means. Is obtained by a rolling speed calculation means.

Here, "resistance value storage means", "stable steering state determination means", "current reduction control means", "motor resistance value calculation means", "resistance value storage processing means", and "rotation speed calculation means" Means ”means, for example, a circuit including a microcomputer and its R
It is realized by a program registered in the OM or the like, and may also be realized by the same circuit as the motor control means described above. The “motor driving unit” is, for example, the above-described H-bridge circuit. The “stable steering state” refers to a state in which rapid steering is not performed (a state in which the change in rotation speed is almost zero), and a steering state (a rotation speed is zero) and a slow steering state (the rotation speed is reduced). Almost constant state). As will be described later, the estimation of the resistance value by the resistance value calculating means in the present invention does not assume that the rotational speed is zero, and the change in the rotational speed (angular acceleration) is zero (strictly, a predetermined error). This is based on the premise that it is almost zero within the range). Further, for the same reason, the "default value" in the condition of the determination by the "stable steering state determination means" of the present invention has a different meaning from the default value in the above-described steering determination in the second invention. That is, here, it is sufficient to determine a stable steering state in which the change in the number of revolutions is almost zero. Therefore, for example, the “predetermined value” as the threshold value for the torque variation and the load variation is not necessarily close to zero. There is no necessity, and a relatively large value may be set. Similarly, the determination condition for the current (the condition of “above the predetermined value”) does not necessarily have to be a large value (a considerable amount) as described above, and may be a value greater than zero in extreme cases. The reason why the current is used as a condition here is that it is determined whether or not a current value that can be calculated by Expression (3) described later exists.

The estimation of the resistance value by the motor resistance value calculating means does not necessarily have to be performed every time the stable steering state determining means determines that the vehicle is in a stable steering state. The estimation calculation of the resistance value R by the motor resistance value calculation means is specifically performed by the following equation (3). R = (VM0−VM1) / (IM0−IM1) (3) Here, VM0 and IM0 are the voltage and current immediately before the current change control unit starts the current change (just before the start of the control signal change). IM1 is the voltage and current immediately after the start of the current change by the current reduction control means (immediately after the start of the control signal change). The above equation (3) is derived assuming that the rotation speeds (or induced voltages) obtained from the respective voltages and currents immediately before and immediately after the start of the current change by the above-mentioned equation (2) are equal. Further, the width of the current change (control signal change) by the current reduction control means is not necessarily limited as long as the above-mentioned equation (3) is satisfied. Should be taken into account. This is because if the width of the current change is too large, the steering assist torque suddenly decreases and the steering torque rapidly increases, even temporarily, so that the operator may feel uncomfortable in steering (uncomfortable steering). Get higher. On the other hand, if the width of the current change is too small, the accuracy of the estimation calculation of the resistance value by the above equation (3) may be degraded. Therefore, the width of the current change should be set in consideration of such a balance. Specifically, for example, when the current of the motor is 50 to 60 A, the reduction width may be set to about 10 to 20 A (that is, about 20 to 30%).

According to the present invention, on the condition that the stable steering state judging means judges the stable steering state as described above, the forcible current change by the current reduction control means (hereinafter, referred to as the "stable steering state").
Current reduction control) is temporarily executed, and the resistance value is estimated and calculated from the voltage and the current before and after the start of the forced current change. That is, the resistance value is accurately estimated and calculated under a wider condition that is not necessarily limited to the steering holding state. For this reason, despite the rotation sensorless configuration,
The frequency of estimating the resistance value by the motor resistance value calculating means (i.e., the frequency of learning the latest resistance value including temperature change and aging) can be much higher than before, and the cost of the device can be increased. The accuracy and reliability of the rotation speed estimation calculation by the rotation speed calculation means are improved without causing the deterioration of the vehicle mountability and the control of the motor using the estimated value of the rotation speed (for example, as described above). The accuracy and effectiveness of the rotational speed sensitive control can be remarkably improved. Also in this case, since the rotation sensor is completely unnecessary, wiring (signal lines between the control unit and the rotation sensor, etc.) for the rotation sensor is also unnecessary, and the sensor for detecting the voltage and the current (and, in some cases, the motor temperature). There is no need to provide wiring for this purpose outside the control unit, as in the first or second aspect of the present invention. Therefore, an inexpensive device with high vehicle mountability, in which the number of sensors and the number of wires outside the control unit are significantly reduced, can be realized.

In a preferred aspect of the present invention, the amount of change of the control signal by the current reduction control means is limited to a range that does not cause a feeling of steering discomfort.
In this case, there is an advantage that the possibility of occurrence of the steering discomfort as described above is eliminated. In another preferred aspect of the present invention, the current reduction control means may set a change amount for changing the control signal each time based on the current detected by the motor current detection means.
By doing so, it is possible to always maintain the variation width of the current at the optimum value, and it is possible to reliably avoid or suppress the occurrence of steering discomfort while maintaining high accuracy in the estimation calculation of the resistance value. This is because the feeling of steering discomfort is more easily perceived by the human as the current at that time (ie, the steering torque) is larger. Therefore, in order to reliably avoid or suppress the steering discomfort, the larger the current at that time is, In addition, it is necessary to further reduce the ratio of the change width of the current. On the other hand, in order to maintain high accuracy of the estimation calculation of the resistance value, it is necessary to increase the ratio of the change width of the current as the current at that time is small, and to sufficiently secure the absolute value of the change width. . That is, the optimum value of the current change width is not always a constant ratio with respect to the current at that time. Therefore, for example, if the change width of the current is determined at a rate inversely proportional to the current magnitude at that time, a more preferable optimum change width is maintained.

In a preferred aspect of the present invention, the number of times the current reduction control means changes the control signal is limited each time the control unit is started. According to this configuration, there is an advantage that the adverse effect of the possibility of occurrence of a steering discomfort can be suppressed to a necessary minimum. That is, in the case of the third aspect of the present invention, the current is changed (the current reduction control described above) triggered by the fact that the stable steering state having a high frequency of occurrence occurs, as described above. This current reduction control may unnecessarily increase the chance of occurrence of steering discomfort. However, if the frequency of the current reduction control is limited every time the control unit is started in this way, it is possible to suppress an unnecessary increase in the chance of occurrence of such a steering discomfort. Usually, the control unit of this type of device is
Since the vehicle is started by turning on the ignition switch of the vehicle, even if such a limitation is provided, it is possible to periodically learn the resistance value at least to reflect the influence of the aging of the resistance value. In another preferred aspect of the present invention, the frequency of the control signal changing by the current reduction control means per prescribed time is limited to a predetermined value or less. This configuration also has the advantage of minimizing the possibility of occurrence of a steering discomfort.

In another preferred aspect of the second and third aspects of the present invention, the motor temperature output means for outputting a detected temperature value or an estimated temperature value of the assist motor, and an output from the motor temperature output means. From the detected temperature value or the estimated temperature value, the resistance value stored in the resistance value storage means is corrected as needed based on a preset temperature characteristic, and the corrected resistance value is changed to the resistance value. And a motor resistance value correction means registered in the value storage means. That is, the first invention is combined with the second or third invention. According to this configuration, the following excellent effects can be obtained in addition to the various effects described above. That is, with respect to the fluctuation of the resistance value caused by the temperature change, the resistance value can always be maintained at an appropriate value by the motor resistance value correcting means. Learning of the latest resistance value based on the calculation may be performed to deal only with a change in resistance value due to other factors (change due to aging or initial variation) (that is, the learning frequency is extremely low and Is no problem).
For this reason, in the second invention, the predetermined value in the above-described condition of the steering state determination is set to a stricter value to make the determination of the steering state extremely reliable, and furthermore, the estimation calculation of the resistance value is performed. Accuracy (further, accuracy of the rotational speed estimation calculation) can be extremely increased. Further, in the third aspect, the frequency of the current reduction control is extremely limited, and the possibility (or frequency) of the occurrence of a steering discomfort due to a change in the current can be significantly reduced. Note that, in this case, when registering a new resistance value obtained by the estimation calculation, it is necessary that at least the corresponding motor temperature data be grasped in association with the new resistance value data. is there. If it is not known how many times the resistance value corresponds to the motor temperature, the position cannot be determined on the temperature characteristic diagram, and the resistance value cannot be temperature-corrected thereafter. In addition, the temperature correction of the resistance value by the motor resistance value correction means always corrects the reference value by correcting the reference value with the temperature at that time while storing and holding the reference value (reference value of temperature correction). Is calculated (in the case of a first embodiment described later), the new resistance value obtained by the estimation calculation of the motor resistance value calculation means is converted into a temperature (as a reference temperature) as necessary. It is necessary to register the converted data as a reference resistance value.

[0027]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) First, an electric power steering apparatus according to an embodiment corresponding to the above-described first invention will be described.
FIG. 1A is a functional block diagram illustrating an apparatus (mainly the configuration and functions of a control system) according to the present embodiment. The present device includes an assist motor 1 (hereinafter, sometimes simply referred to as a motor 1) that is connected to a steering system of a vehicle and generates a steering assist torque;
A control circuit 2 for controlling the assist motor 1 via a drive circuit (motor drive means) not shown. Here, the drive circuit includes the above-described H-bridge circuit, and four FETs (not shown) constituting the H-bridge circuit drive signals including a PWM drive signal output from the control circuit 2 (the present invention). (Equivalent to a control signal). More specifically, for example, when the motor 1 is driven in the left rotation direction of the steering wheel (when a current in the left direction is supplied), for example, one of the FETs connected to the low-potential power supply is driven in an ON state. Then, a drive signal for PWM driving one FET connected to the high potential power supply side is output.

The control circuit 2 is a processing means specifically composed of a circuit including a microcomputer, and as shown in FIG. 1A, a command value creation unit 3, a current control unit 4, a motor rotation estimation calculation It has a processing unit 5 and a motor resistance temperature correction unit 6 as processing functions. The motor resistance temperature correction unit 6 corresponds to a motor resistance value correction unit of the present invention, and the motor rotation estimation calculation unit 5 corresponds to a rotation speed calculation unit of the present invention. Further, the control circuit 2 and the above-described drive circuit are formed on a substrate in the unit case, and constitute a control unit as a whole. Further, the resistance value storage means of the present invention is constituted by, for example, a ROM or a RAM of a microcomputer constituting the control circuit 2. Although not shown,
On a substrate in the control unit, a current detection circuit or a voltage detection circuit corresponding to the motor current detection means and the motor voltage detection means of the present invention, and a motor temperature output circuit corresponding to the motor temperature output means are formed. The current detection circuit is a circuit that detects a potential difference between both terminals of a shunt resistor connected on a power supply line of the H-bridge circuit as a motor current value. The voltage detection circuit is a circuit that detects a potential difference between motor connection terminals in the H-bridge circuit as a motor voltage value (motor applied voltage). Further, the motor temperature output circuit receives, for example, a detection signal from a temperature sensor (not shown) attached to the motor 1 and performs amplification or noise removal processing of the detection signal as necessary to indicate the motor temperature. It is a circuit that outputs a signal (temperature detection value). Instead of the motor temperature output circuit, the control circuit 2 may be provided with a function of estimating and calculating the temperature of the motor 1 by the known method described above.

The command value creating unit 3 basically calculates a command including a steering torque detection value signal (torque signal) from a torque sensor (steering torque detecting means) (not shown) for detecting the steering torque of the steering system of the vehicle. A current command value corresponding to the direction and magnitude of the steering torque is calculated and output. That is, when the steering torque is leftward, for example, a current command value corresponding to a leftward current having a magnitude proportional to the magnitude of the steering torque is generated. In this case, the command value creation unit 3 outputs the output of a vehicle speed sensor (not shown) (that is, a signal of the vehicle speed) as a parameter for determining the current command value and the rotation speed ω output from the motor rotation estimation calculation unit 5. Data (that is, a signal equivalent to the steering wheel angular velocity) is also input, and the current command value is appropriately changed by these signals, so that the steering torque does not depend on the steering torque uniformly but a more preferable steering assist torque depending on the situation. It is configured to generate. That is, when the vehicle speed is relatively low, the steering assist torque is set to a relatively large value, or by performing the negative feedback processing of the steering wheel angular speed as described above, the steering assist torque is reduced according to the steering wheel angular speed. (Or so that the steering assist torque is in the opposite direction), a process of changing the current command value is also performed.

The current controller 4 determines the content of the current control signal including the duty ratio of the PWM drive signal from the current command value and the actual motor current value (output of the current detection circuit), and further drives the FET control signal. And output it. For example, if the current command value is for commanding a current in the left direction, it is determined that a predetermined drive signal including a PWM drive signal for the left FET is output, and the PWM signal is output.
The duty ratio of the M drive signal is, for example, a value obtained by correcting the magnitude of the current command value according to the difference (ie, deviation) from the magnitude of the actual motor current value (ie, feedback value). That is, the content of the control signal is determined by the feedback control (PD control) so that the magnitude and direction of the actual current value follow the magnitude and direction of the current command value.
The current control unit 4 includes a motor rotation estimation calculation unit 5
, The above-described rotational speed sensitive control may be executed.

The motor rotation estimation calculating section 5 stores the voltage and current detected by the voltage detection circuit and the current detection circuit, and the resistance value storage means (for example, a predetermined area in the RAM of the microcomputer constituting the control circuit 2). From the stored latest resistance value R (if this is not registered, a reference resistance value R0 described later), the rotational speed ω is estimated and calculated by the above-described equation (1). The motor resistance temperature correction unit 6 uses a temperature detection value output from the motor temperature output circuit, based on a preset temperature characteristic, based on a resistance value storage means (for example, a ROM in a microcomputer of the control circuit 2). The reference resistance value R0 stored in the predetermined area is corrected as necessary, and the corrected resistance value is registered as the latest resistance value R in resistance value storage means (for example, the predetermined area in the RAM described above). I do. In addition, as the reference resistance value R0,
A standard resistance value (design value or measured value in a shipping test, etc.) of the motor 1 at a reference temperature (for example, 20 ° C.) is registered in advance. As the temperature characteristics, for example, as shown in FIG. 1B, the relationship between the correction coefficient K for temperature correction with respect to the reference resistance value R0 and the motor temperature t is as follows.
It is given as a data table or a function (formula) and is registered in advance in the above-mentioned ROM or the like. Accordingly, in this case, the correction process specifically performed here is to first read the temperature t at that time, obtain a correction coefficient K for the temperature t from the above data table or function, and then obtain the obtained coefficient K
Is multiplied by the reference resistance value R0 to obtain the latest resistance value R.
(= R0 · K). Then, for example, the resistance value R is unconditionally updated and registered in a predetermined area in the RAM (the old resistance value R is erased and registered). If the resistance value R obtained by the latest correction operation is the same as the previously registered resistance value R or the difference is within the allowable error range, the update registration is not performed. May be. Further, the old resistance value R does not always need to be erased. It goes without saying that the data of the correction coefficient K can be easily obtained as the physical properties of the material (for example, copper) constituting the motor coil.

The operation of the control circuit 2 (actually, the processing contents of the microcomputer) for actually implementing the functions described above may be such that, for example, a series of processing as shown in FIG. 2 is periodically repeated. That is, first, in step S1, the motor temperature t is read, and then in step S2, the coefficient K corresponding to the motor temperature t is read. Next, step S3
Then, the correction calculation of the motor resistance temperature correction unit 6 is executed,
At least the latest resistance value R as the calculation result is stored and held. Then, in Step S4, the detected current and voltage are read, and then in Step S5, Step S3
Using the latest resistance value R obtained in step (1), the above-described estimation calculation of the rotation speed ω (the above-described equation (1)) is performed to generate the latest value of the rotation speed ω. After this step S5, the processing of one sequence is completed. The execution cycle of the correction calculation of the resistance value R (in this case, the execution cycle of the series of processes in FIG. 2) can be freely set within the range of the processing capability of the microcomputer. Needless to say, it can be executed at a much higher frequency.

According to this apparatus, learning of a change or a change in the motor resistance value caused by a temperature change can be performed with sufficient frequency by setting the execution cycle of the correction calculation, even though the rotation sensor is not used. Therefore, it is possible to improve the accuracy and reliability of the calculation for estimating the rotation speed of the motor rotation estimation calculation unit 5 without increasing the cost of the device or deteriorating the mountability of the vehicle, and to use the estimated value of the rotation speed. The accuracy and effectiveness of the control of the motor (for example, the negative feedback control of the steering wheel angular velocity and the control of the rotation speed described above) can be remarkably improved. In this case, since a rotation sensor is not required at all, wiring for the rotation sensor (signal line between the control unit and the rotation sensor) is not required. In addition, as the voltage and current used for the rotation speed estimation calculation,
Since the one detected by the detection circuit in the control unit described above is used, it is not necessary to provide a sensor for detecting the voltage or the current and a wiring therefor outside the control unit. When the motor temperature is estimated and calculated as described above, it is not necessary to attach a temperature sensor to the motor, and wiring for the temperature sensor (such as a signal line between the control unit and the temperature sensor) is not required. Become. Therefore, it is possible to realize an inexpensive device with high vehicle mountability, in which the number of sensors and the number of wires outside the control unit are significantly reduced.

(Second Embodiment) Next, an electric power steering apparatus according to a second embodiment of the present invention will be described. FIG. 3 is a functional block diagram showing the apparatus (mainly the configuration and functions of the control system) of the present embodiment. In the following, the same elements as those in the first embodiment (FIG. 1A) are denoted by the same reference numerals, and redundant description will be omitted. This device has a motor resistance learning unit 7 instead of the motor resistance temperature correction unit 6 in the first embodiment, and further includes a low-pass filter unit 8, difference calculation units 9 and 10, and a steering state determination unit 11. It was done. Here, the motor resistance learning unit 7 constitutes the motor resistance value calculation unit and the resistance value storage processing unit of the present invention, and the low pass filter unit 8, the difference calculation units 9 and 10, and the steering state determination unit 11 The state determining means is constituted. In the motor resistance learning unit 7, the voltage detected by the voltage detection circuit and the current detected by the current detection circuit are determined on the condition that the steering state determination unit 11 determines that the steering state is maintained for a predetermined time or more. Assuming that the rotational speed ω is zero from the current, the resistance value R is estimated and calculated by the above equation (2). Then, for example, the resistance value R is unconditionally updated and registered in a predetermined area in the RAM of the microcomputer (the old resistance value R is erased and registered). Note that if the resistance value R obtained by the latest calculation is the same as the previously registered resistance value R or the difference is within the allowable error range, the update registration is not performed. Good. Further, the old resistance value R does not always need to be erased.

The low-pass filter section 8 performs processing as a low-pass filter (LPF) for removing high-frequency components of the input, and removes the influence of noise and the like from the torque signal.
Although the low-pass filter unit 8 can be realized as processing by a microcomputer, it is needless to say that the low-pass filter unit 8 can be easily configured as a hardware (filter circuit). Is). The difference calculation units 9 and 10 calculate a difference ΔT or Δω (that is, a differential value) between the torque signal T (the output of the low-pass filter unit 8) and the rotation speed ω (the output of the motor rotation estimation calculation unit 5). This is an element that is output to the steering state determination unit 11. The difference ΔT or Δω is, for example, the difference between the value of the torque signal T and the value of the rotational speed ω read at a constant sampling period, between the last read value and the previously read value. If the differences ΔT and Δω are equal to or less than a predetermined value (zero or near) and the current IM is equal to or more than a predetermined value, the steering state determination unit 11 determines that the vehicle is in the steering holding state and outputs a signal indicating the state. (Or set that information).

The operation of the control circuit 2 (actually the processing contents of the microcomputer) for actually realizing the functions described above may be such that a series of processing as shown in FIG. 4 is periodically repeated, for example. That is, first, in step S11, the torque signal T is read, and then, in step S12, the low-pass filter processing of the torque signal T is performed. Next, in step S13, the torque signal T after the low-pass filter processing is performed.
And the previous stored value (step S1
2. The difference ΔT is obtained by subtracting the latest value obtained this time (the value of the torque signal T obtained in the immediately preceding step S12) from the value of the torque signal T obtained in step 2). Next, in step S14, it is determined whether or not the difference ΔT obtained in step S13 is equal to or smaller than a predetermined value (in this case, whether it is zero). If it is zero, the process proceeds to step S5. finish. Then, step S1
In step S5, the latest rotation number ω obtained by the motor rotation estimation calculation unit 5 and the stored value of the rotation number ω read in this step one sequence before are read out, and the next step S
At 16, the latest value of the rotational speed ω is subtracted from the stored value to obtain a difference Δω. Next, in step S17, the difference Δ
It is determined whether or not ω is equal to or smaller than a predetermined value (zero or a value close thereto). If ω is equal to or smaller than the predetermined value, the process proceeds to step S18; otherwise, the processing of one sequence is terminated.

Next, in step S18, the output value of the current detection circuit at that time (ie, the detection value of the current IM) is read. Next, in step S19, step S18
It is determined whether or not the current IM read in step is equal to or larger than a predetermined value (for example, 50% of the rated current of the motor 1). If the current IM is equal to or larger than the predetermined value, the process proceeds to step S20. Then, in step S20, a process (predetermined time) for measuring the elapsed time in a state where the determination in step S19 is continuously positive (that is, a state where it is continuously determined to be in the steering holding state). (A process of starting the time counting operation of the timer of (1) or counting up). Next, in step S21, step S20
Then, it is determined whether or not the elapsed time measured in the process is equal to or longer than a predetermined value (for example, about 1 second). If the elapsed time is equal to or longer than the predetermined value, the process proceeds to step S22; otherwise, the process of one sequence is ended. Then, in step S22, the output value of the voltage detection circuit at that time (that is, the detection value of the voltage VM) is read. Next, in step S23, from the current IM read in step S18 and the voltage VM read in step S22, the above-described equation (2) is used to calculate the resistance value R. Register in a predetermined memory area of the RAM. After this step S23, the processing of one sequence ends.

According to the above-described device, the amount of change (difference ΔT) in the detected steering torque is equal to or less than the predetermined value by the functions of the steering state determination unit 11 and the like (the functions realized by the processing of steps S11 to S19). And that the amount of change in the load of the assist motor (in this case, the difference Δω of the rotational speed difference ω) has become equal to or smaller than a predetermined value, and that the detected current IM is equal to or larger than the predetermined value. It is determined that the vehicle is in the steering-holding state. That is, a state in which the amount of torque fluctuation and the amount of load fluctuation are extremely small is set as a condition for determining whether to maintain the steering. In such a state, the rotation speed ω can be almost zero (steering state), so that the steering state can be determined with considerable accuracy. The state is not limited to such a special state, and a state where the rotational speed ω is actually zero can be widely determined. For this reason, the frequency of the calculation and estimation of the resistance value R (the processing in step S23) performed based on the determination of the steering holding state (that is, the latest resistance including the temperature change and the aging change) is performed even though the rotation sensor is not provided. Value learning frequency) can be remarkably increased as compared with the related art, and the accuracy of the rotation speed ω estimation calculation by the motor rotation estimation calculation unit 5 can be improved without increasing the cost of the device or deteriorating the vehicle mountability. In addition, the accuracy and effectiveness of motor control (for example, the above-described rotational speed sensitive control) using the estimated value of the rotational speed ω can be remarkably improved.

In particular, in this embodiment, the condition that the detected current is equal to or more than a predetermined value is added as a condition for judging that the vehicle is in the steering-holding state. Be more certain. In this embodiment, as a condition for performing the estimation calculation of the resistance value R, the fact that the time for determining that the vehicle is in the steering holding state has exceeded the specified time is further added (steps S20 and S21). Therefore, as described above, the accuracy of the estimation calculation of the resistance value is further improved, and the accuracy of the estimation calculation of the rotation speed using the estimated value of the resistance value is further improved, and the estimated value of the rotation speed is further improved. The control of the used motor is more accurate.

(Third Embodiment) Next, an electric power steering apparatus according to a third embodiment of the present invention will be described. FIG. 5A is a functional block diagram illustrating the apparatus (mainly the configuration and functions of the control system) of the present embodiment. In the following, the same elements as those in the second embodiment (FIG. 3) are denoted by the same reference numerals, and redundant description will be omitted. This device is different from the second embodiment in that it includes a motor resistance learning unit 7a and a steering state determination unit 11a having different functions, and further includes an output reduction calculation unit 1
2 and an output thinning unit 13 are added. Here, the motor resistance learning unit 7a constitutes a motor resistance value calculation unit and a resistance value storage processing unit of the present invention, and includes a low-pass filter unit 8, difference calculation units 9 and 10, and a steering state determination unit 11
"a" constitutes a stable steering state determination means. Further, the output reduction calculating section 12 and the output thinning section 13 constitute a current reduction control means of the present invention.

In this case, in the motor resistance learning section 7a, when a signal (during-decimation signal) indicating that the signal is being decimated (during the current reduction control) is input from the output reduction operation section 12, immediately before the rising of this decimated signal. From the voltage and current (VM0, IM0 and VM1, IM1) detected immediately thereafter, the change in the rotational speed ω is assumed to be zero, and the resistance value R is estimated and calculated by the above equation (3). Then, for example, unconditionally, the resistance value R
Is updated and registered in a predetermined area in the RAM of the microcomputer (the old resistance value R is erased and registered). Note that if the resistance value R obtained by the latest calculation is the same as the previously registered resistance value R or the difference is within the allowable error range, the update registration is not performed. Good.
Further, the old resistance value R does not always need to be erased.

The steering state determination section 11a calculates the difference ΔT and Δ
If ω is equal to or less than a predetermined value (zero or near) and the current IM is equal to or more than the predetermined value, it is determined that the vehicle is in a stable steering state and its signal (steering stable signal) is output (or the steering stable signal). Information). In the output reduction calculating section 12, the current change amount ΔIM of the current reduction control (specifically, during the duty ratio of the PWM drive signal, on the condition that the stable steering state is determined by the steering state determination section 11a). Is determined in accordance with the current IM detected at that time, and a signal of the thinning amount is output.
Specifically, as shown in FIG. 5B, a current change amount ΔIM is calculated based on a preset relationship (data table or function expression).
Is determined from the power supply voltage V and the resistance value R (which may be an ideal resistance value such as a design value).
Thinning amount (ΔIM / (V /
R)) and outputs the signal. Note that the current change amount ΔIM determined here is limited to a range that does not cause a feeling of steering discomfort. Then, in the output thinning section 13, when the signal of the thinning amount is output from the output reduction calculating section 12,
The duty ratio of the PWM drive signal output from the current control unit 4 is temporarily reduced by the signal of the thinning amount (for example,
(For about 1 msec) and output to the drive circuit. Further, the output thinning unit 13 simply transmits the drive signal including the PWM drive signal output from the current control unit 4 as it is when the signal of the thinning amount is not output from the output reduction calculation unit 12. . When the output thinning unit 13 performs the attenuation according to the signal of the thinning amount, the current IM temporarily decreases by the current change amount ΔIM as shown in FIG. 6, for example.

The operation of the control circuit 2 (actually the processing contents of the microcomputer) for actually realizing the functions described above may be such that, for example, a series of processing as shown in FIG. 7 is periodically repeated. That is, first, in step S31, it is determined whether or not the current reduction control is being executed.
Proceed to 43, otherwise proceed to step S32. Then, in a step S32, the torque signal T is read, and then, in a step S33, a low-pass filtering process of the torque signal T is performed. Next, in step S34, the torque signal T after the low-pass filter processing is used to calculate the latest value (the immediately preceding value) obtained from the previous stored value (the value of the torque signal T obtained in step S33 one sequence before). (The value of the torque signal T obtained in step S33) is subtracted to obtain a difference ΔT. Next, in step S35, it is determined whether or not the difference ΔT obtained in step S34 is equal to or smaller than a predetermined value (in this case, whether it is zero). If it is zero, the process proceeds to step S36. finish. Then, in step S36, the latest rotation speed ω obtained by the motor rotation estimation calculation section 5 and the stored value of the rotation speed ω read in this step one sequence before are read out, and in the next step S37, The difference Δω is obtained by subtracting the latest value of the rotational speed ω from the stored value. Next, in step S38, it is determined whether or not the difference Δω is equal to or less than a predetermined value (zero or a value close to the predetermined value). If the difference Δω is equal to or less than the predetermined value, the process proceeds to step S39; .

Next, in step S39, the output values of the current detection circuit and the voltage detection circuit at that time are read as the current IM0 and the voltage VM0 immediately before the current reduction control. Next, in step S40, it is determined whether or not the current IM0 read in step S39 is equal to or greater than a predetermined value (for example, 10% of the rated current of the motor 1). The processing of one sequence ends. Then, in step S41, the current change amount ΔIM of the current reduction control is determined from the relationship shown in FIG. 5B, and the current reduction control is started in the next step S42. On the other hand, in step S43, the output values of the current detection circuit and the voltage detection circuit at that time are read as the current IM1 and the voltage VM1 immediately after the start of the current reduction control. Then, in step S44, the current and voltage (IM0, VM0 and IM1, VM1) read in steps S39 and S43 are read.
From 1), the resistance value R is obtained by performing the calculation of the above equation (3), and is registered as the latest resistance value R in, for example, a predetermined memory area of a RAM of a microcomputer. Next, step S45
Then, the current reduction control started in step S42 is stopped (current reduction control is stopped). And this step S
After 45, the processing of one sequence ends.

According to the present invention, the steering state determination unit 11a
Is temporarily executed on condition that the stable steering state is determined as described above, the resistance value R is determined from the voltage and current before and after the start of the forced current change. Is estimated. That is, under a wider condition that is not necessarily limited to the steering holding state, the resistance R
Is accurately estimated. For this reason, the frequency of calculation and estimation of the resistance value (ie,
The learning frequency of the latest resistance value including temperature change and aging change) can be much higher than before, and the rotation speed can be estimated without increasing the cost of the device or deteriorating the vehicle mountability. The accuracy and reliability of the calculation can be improved, and the accuracy and effectiveness of motor control (for example, the above-described rotation speed sensitive control) using the estimated value of the rotation speed can be significantly improved. Further, in this embodiment, since the amount of change in the current due to the current reduction control is limited to a range that does not cause the steering discomfort, there is an advantage that the steering discomfort as described above does not occur. In this embodiment, the current change amount is set each time based on the detected current. For this reason, it is possible to always maintain the variation width of the current at the optimum value, and it is possible to reliably avoid the occurrence of a steering discomfort while maintaining the accuracy of the estimation calculation of the resistance value high.

The present invention is not limited to the above-described embodiment, but may have various aspects and modifications as described in the section of means for solving the problems. For example, the first embodiment may be combined with the second or third embodiment. That is, the motor resistance temperature correction section 6 is inserted between the motor resistance learning section 7 or 7a and the motor rotation estimation calculation section 5 in FIG. The motor resistance temperature correction unit 6
May be registered as the above-described reference resistance value R0. However, in this case, the motor resistance learning unit 7
Alternatively, it is necessary to convert the resistance value estimated and calculated in 7a into a resistance value at a reference temperature (for example, 20 ° C.) according to the relationship in FIG. 1B, and then register it as a reference resistance value R0. . Further, the number of times of the current reduction control may be limited each time the control unit is started, or the frequency of the current reduction control per specified time may be limited to a predetermined value or less. Instead of the current reduction control, it is possible in principle to estimate and calculate the resistance value by controlling the current to temporarily and forcibly increase.

[0047]

According to the first aspect of the present invention, the motor resistance correction means performs the above-described temperature correction at any time, for example, at a constant cycle. Since the learning for the change or fluctuation of the motor resistance value can be performed with sufficient frequency, the estimation of the rotation speed by the rotation speed calculating means can be performed without increasing the cost of the device or deteriorating the mountability of the vehicle. Accuracy and reliability can be improved, and, consequently, the accuracy and effectiveness of motor control (for example, the above-described rotational speed responsive control) using the estimated rotational speed can be significantly improved.

According to the second aspect of the present invention, the steering state determination means determines that the amount of change in the detected steering torque is equal to or less than a predetermined value (eg, equal to or less than zero or less) and the load of the assist motor is reduced. It is determined that the steering state is maintained on condition that the amount of change is equal to or less than a predetermined value (for example, equal to or less than a value near zero). That is, a state in which the amount of torque fluctuation and the amount of load fluctuation are small is a condition for determining whether the steering is maintained. In such a state, there is almost no possibility that the rotation speed ω is only zero (steering state) (because it is difficult to rotate the steering wheel while keeping the torque fluctuation and the load fluctuation small). It is possible to determine the steering holding state with the accuracy of, and it is not necessarily limited to a special state such as at the time of operating the steering wheel end (at the end of the rack), and it is possible to widely determine a state where the rotational speed ω is actually zero. For this reason, the frequency of the estimation of the resistance value by the motor resistance value calculating means performed based on the determination of the steering holding state (that is, the latest resistance value including the temperature change and the aging change) even though the rotation sensor is not used. Learning frequency) can be significantly increased as compared with the conventional method, and the accuracy and reliability of the rotation speed estimation calculation by the rotation speed calculation means are improved without increasing the cost of the device or deteriorating the mountability of the vehicle. As a result, the accuracy and effectiveness of the control of the motor using the estimated value of the rotational speed (for example, the above-described rotational speed sensitive control) can be remarkably improved.

According to the third aspect of the present invention, the forcible current change (current reduction control) by the current reduction control means is temporarily performed on the condition that the stable steering state determination means determines the stable steering state as described above. The resistance value is estimated and calculated from the voltage and the current before and after the start of the forced current change. That is, the resistance value is accurately estimated and calculated under a wider condition that is not necessarily limited to the steering holding state. For this reason, the frequency of calculating and estimating the resistance value by the motor resistance value calculating means (that is, the learning frequency of the latest resistance value including the temperature change and the aging change) despite the configuration without the rotation sensor.
Can be much higher than before, and the accuracy and reliability of the rotation speed estimation calculation by the rotation speed calculation means can be improved without increasing the cost of the device or deteriorating the mountability of the vehicle. The accuracy and effectiveness of the control of the motor using the estimated value of the rotational speed (for example, the rotational speed sensitive control described above) can be remarkably improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a control system (first embodiment) of an electric power steering device.

FIG. 2 is a flowchart showing an operation (resistance temperature correction and the like) of the apparatus.

FIG. 3 is a diagram showing a control system (second embodiment) of the electric power steering device.

FIG. 4 is a flowchart showing an operation (resistance value learning) of the apparatus.

FIG. 5 is a diagram showing a control system (third embodiment) of the electric power steering device.

FIG. 6 is a diagram showing an example of a change in current or the like due to current reduction control of the device.

FIG. 7 is a flowchart showing an operation (resistance value learning) of the apparatus.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 assist motor 2 control circuit (control unit, resistance value storage means) 3 command value creation section 4 current control section 5 motor rotation estimation calculation section (rotation speed calculation means) 6 motor resistance temperature correction section (motor resistance value correction means) 7 Motor resistance learning section (motor resistance value calculation means, resistance value storage processing means) 7a Motor resistance learning section (motor resistance value calculation means, resistance value storage processing means) 8 Low pass filter section (stable steering state determination means) 9 difference calculation section (Steering state determining means, stable steering state determining means) 10 Difference calculating section (steering state determining means, stable steering state determining means) 11 Steering state determining section (steering state determining means) 11a Steering state determining section (stable steering) State determination means) 12 output reduction calculating section (current reduction control means) 13 output thinning section (current reduction control means)

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Claims (10)

[Claims] 1. An assist motor connected to a steering system of a vehicle for generating a steering assist torque, a steering torque detecting means for detecting a steering torque of the steering system, and a steering torque detection by at least the steering torque detecting means. A control unit that controls the assist motor based on a parameter including a value and a rotation speed of the assist motor, wherein the control unit detects a voltage applied to the assist motor. Voltage detecting means, motor current detecting means for detecting a current flowing through the assist motor, motor temperature output means for outputting a detected temperature value or an estimated temperature value of the assist motor, and a resistor for storing a resistance value of the assist motor Value storage means, and a temperature detection value output from the motor temperature output means Alternatively, the resistance value stored in the resistance value storage means is corrected as necessary based on a temperature characteristic set in advance by a temperature estimation value, and the corrected resistance value is registered in the resistance value storage means. And a motor resistance value correcting means for calculating the rotational speed from the voltage and current detected by the motor voltage detecting means and the motor current detecting means, and the latest resistance value stored in the resistance value storing means. An electric power steering device comprising: a rotation speed calculating means. 2. An assist motor connected to a steering system of a vehicle for generating a steering assist torque, a steering torque detecting means for detecting a steering torque of the steering system, and a steering torque detection by at least the steering torque detecting means. A control unit that controls the assist motor based on a parameter including a value and a rotation speed of the assist motor, wherein the control unit detects a voltage applied to the assist motor. Voltage detection means, motor current detection means for detecting a current flowing through the assist motor, resistance value storage means for storing a resistance value of the assist motor, and at least a variation in the steering torque detection value is equal to or less than a predetermined value. And that the amount of change in the load of the assist motor has fallen below a predetermined value. A steering state determining means for determining a steering state; and a motor voltage detecting means and a motor current provided that at least the steering state is determined by the steering state determining means. Motor resistance value calculation means for estimating and calculating the resistance value of the assist motor based on the voltage and current detected by the detection means assuming that the rotation speed is zero, and calculating the resistance value obtained by the motor resistance value calculation means. Resistance value storage processing means for registering a new resistance value in the resistance value storage means; voltage and current detected by the motor voltage detection means and motor current detection means; and stored in the motor resistance value storage means. An electric power steering device comprising: a rotational speed calculating means for estimating and calculating the rotational speed from the latest resistance value. Apparatus. 3. The method according to claim 2, wherein the condition that the steering state determination means determines that the vehicle is in the steering state is that a current detected by the motor current detection means is a predetermined value or more. The electric power steering apparatus according to claim 2, wherein 4. A condition in which the motor resistance value calculation means executes the estimation calculation, wherein the steering holding state determination means includes:
4. The electric power steering apparatus according to claim 2, further comprising a condition that the time for determining that the vehicle is in the steering maintaining state exceeds a prescribed time. 5. An assist motor connected to a steering system of the vehicle for generating a steering assist torque, a steering torque detecting means for detecting a steering torque of the steering system, and a steering torque by at least the steering torque detecting means. An electric power steering apparatus comprising: a control unit that controls the assist motor based on a parameter including a detected value and a rotation speed of the assist motor, wherein the control unit controls a current flowing through the assist motor. Motor drive means, motor voltage detection means for detecting a voltage applied to the assist motor, motor current detection means for detecting the current, resistance value storage means for storing a resistance value of the assist motor, The fluctuation amount of the steering torque detection value is equal to or less than a predetermined value, and the negative A stable steering state determining unit that determines that the vehicle is in a stable steering state, provided that a variation amount of the load is equal to or less than a predetermined value, and that a current detected by the motor current detecting unit is equal to or greater than a predetermined value. At least, provided that the stable steering state is determined by the stable steering state determining means,
Current reduction control means for temporarily and forcibly changing the control signal of the motor drive means in a direction in which the magnitude of the current decreases; and the motor before and after the start of the change of the control signal by the current reduction control means Motor resistance value calculation means for estimating and calculating the resistance value of the assist motor based on the voltage and current detected by the voltage detection means and the motor current detection means, assuming that the change in the number of revolutions is zero; Resistance value storage processing means for registering the resistance value obtained by the means as a new resistance value in the resistance value storage means; voltage and current detected by the motor voltage detection means and motor current detection means; and Rotation speed calculation means for estimating and calculating the rotation speed from the latest resistance value stored in the motor resistance value storage means. An electric power steering apparatus according to claim. 6. An electric power steering apparatus according to claim 5, wherein said current reduction control means limits a change amount for changing said control signal to a range in which a steering discomfort does not occur. 7. The method according to claim 5, wherein the current reduction control means sets a change amount for changing the control signal each time based on the current detected by the motor current detection means. Electric power steering device. 8. The electric power steering apparatus according to claim 5, wherein the current reduction control means limits the number of times the control signal is changed every time the control unit is started. 9. The electric power steering apparatus according to claim 5, wherein said current reduction control means limits the frequency of changing said control signal per specified time to a predetermined value or less. 10. A motor temperature output means for outputting a detected temperature value or an estimated temperature value of the assist motor, and a temperature characteristic set in advance based on the detected temperature value or the estimated temperature value output from the motor temperature output means. And a motor resistance correction unit that corrects the resistance value stored in the resistance value storage unit as needed based on the above, and registers the corrected resistance value in the resistance value storage unit. The electric power steering apparatus according to any one of claims 2 to 9, wherein: