JP2006076331A - Electric power steering device - Google Patents

Abstract

An electric power steering apparatus that does not impair steering feeling when starting or restarting is provided.
A normal proportional gain until the absolute value of a target current Im * becomes equal to or less than a determination current Im0 when an initial state is detected or until a predetermined time T1 elapses after the initial state is detected. An initial proportional gain Kp2 and an initial integral gain Ki2 that are smaller than Kp1 and the normal integral gain Ki1 are set.
[Selection] Figure 2

Description

  The present invention relates to an electric power steering apparatus.

2. Description of the Related Art Conventionally, an electric power steering apparatus performs proportional / integral control (PI control) based on a deviation between a target current of an assist motor calculated from, for example, steering torque and vehicle speed, and an electric motor current flowing through the assist motor (for example, , See Patent Document 1).
JP-A-8-332969

  By the way, in the case where the electric power steering device is started or when the failure is recovered after the failure is diagnosed by the failure diagnosis and the device is restarted, the device is started immediately and the steering by the assist motor is performed. Auxiliary force is generated. For example, when the apparatus is started or restarted with a steering torque applied to the steering wheel, a steering assist force is applied by the assist motor, and the steering force is suddenly reduced to impair the steering feeling. It was.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an electric power steering device that does not impair the steering feeling even when the device is started or restarted. To do.

(1) First Invention An electric power steering apparatus according to a first invention is provided to an assist motor for assisting a steering force, a steering torque detecting means for detecting a steering torque applied to a steering shaft, and supplied to the assist motor based on the steering torque. Target current setting means for setting a target current to be performed, motor current detection means for detecting a motor current flowing in the assist motor, and at least one of a proportional element and an integral element based on a deviation between the target current and the motor current Proportional integral control means, and motor drive means for driving the assist motor based on the output of the proportional integral control means. And the characteristic matter of the electric power steering device of the first invention further includes an initial state detecting means for detecting an initial state which is a start state or a restart state of the electric power steering device, and when the electric power steering device is not the initial state, First gain setting means for setting the proportional gain of the proportional element and / or the integral gain of the integral element to the first proportional gain and / or the first integral gain; and the proportional gain and / or the integral in the initial state And a second gain setting means for setting a gain to a second proportional gain smaller than the first proportional gain and / or a second integral gain smaller than the first integral gain.

  Here, the starting state of the electric power steering device is, for example, a state when the ignition switch is turned on. The restart state is a state when the failure is recovered after the failure diagnosis is made. That is, when the apparatus is started or restarted, a gain smaller than the gain in the normal state is set.

(2) Second invention An electric power steering device according to the second invention is provided to an assist motor for assisting a steering force, a steering torque detecting means for detecting a steering torque applied to a steering shaft, and supplied to the assist motor based on the steering torque. Target current setting means for setting a target current to be performed, motor current detection means for detecting a motor current flowing through the assist motor, and motor drive control for driving and controlling the assist motor based on a deviation between the target current and the motor current Means. And the characteristic matter of the electric power steering device of the second invention is further the initial state detecting means for detecting the initial state which is the starting state or the restarting state of the electric power steering device, and the initial state is detected. And an assist permission signal output means for outputting an assist permission signal to the electric motor drive control means when the steering torque or the target current is equal to or less than a predetermined threshold value. Furthermore, the motor drive control means starts or restarts drive control when the assist permission signal is output.

  That is, the assist permission signal output means outputs an assist permission signal to the motor drive control means when the initial state is detected and the steering torque is equal to or less than the predetermined torque threshold. Alternatively, the assist permission signal output means outputs an assist permission signal to the motor drive control means when the initial state is detected and the target current is equal to or less than a predetermined current threshold.

  The motor drive control means starts or restarts the drive control when the assist permission signal is output. In other words, the motor drive control means is stopped until the assist permission signal is output when starting or restarting.

(1) Effects of the First Invention According to the electric power steering apparatus of the first invention, the proportional gain / integral gain in the initial state is smaller than the proportional gain / integral gain in the non-initial state (normal state). Proportional gain and integral gain. Here, reducing the proportional gain / integral gain lowers the steering tracking ability. As a result, a steady deviation occurs, and the motor current flowing through the assist motor becomes smaller than the target current. Therefore, when the steering torque is applied to the steering wheel in the initial state, the steering follow-up performance is reduced to reduce the steering assist force, thereby suppressing the sudden generation of the steering assist force by the assist motor. it can. That is, even in the initial state, even when the steering torque is applied to the steering wheel, a good steering feeling can be obtained.

(2) Effect of the Second Invention According to the electric power steering apparatus of the second invention, when the initial state is detected and the steering torque or the target current becomes equal to or less than the predetermined threshold value, the motor drive control means Starts or restarts.

  Here, the case where the steering torque is larger than the predetermined torque threshold and the case where the target current is larger than the predetermined current threshold are states where a large steering torque is applied to the steering wheel. That is, when a large steering torque is applied to the steering wheel, even if the electric power steering device is started or restarted, the auxiliary steering force by the assist motor is not generated immediately. Therefore, the steering feeling due to the steering assist force that occurs suddenly is not impaired.

  Further, when the steering torque is equal to or less than a predetermined torque threshold value or the target current is equal to or less than the predetermined current threshold value, the generation of the steering assist force by the assist motor is permitted. Here, when the steering torque is equal to or smaller than the predetermined torque threshold value or the target current is equal to or smaller than the predetermined current threshold value, the steering assist force itself by the assist electric motor is reduced. That is, when generating the steering assist force by the assist motor, the steering feeling is not impaired because the steering assist force itself is small. As a result, a good steering feeling can be obtained.

  Next, the present invention will be described in more detail with reference to embodiments.

(1) Embodiment of the First Invention As described above, the electric power steering apparatus of the first invention is an assist motor, steering torque detection means, target current setting means, motor current detection means, and proportional-integral control means. And an electric motor driving means, an initial state detecting means, a first gain setting means, and a second gain setting means.

(1.1) Assist motor / motor drive means Here, for example, a DC motor, a brushless DC motor, or the like can be used as the assist motor. In the case where a brushless DC motor is used as the assist motor, the motor driving means includes an inverter circuit including a plurality of switching elements, a PWM output unit that outputs a PWM signal, and the like. When a DC motor is used as the assist electric motor, the electric motor driving means includes a full bridge circuit having a plurality of switching elements, a PWM output unit that outputs a PWM signal, and the like.

(1.2) Steering torque detection means / proportional integral control means The steering torque detection means may be a steering torque sensor capable of detecting steering torque. This steering torque sensor is provided on, for example, a steering shaft. Further, the proportional-plus-integral control means may be any of a proportional element only, an integral element only, a proportional element and an integral element.

(1.3) Gain setting means The second gain setting means is configured to set the proportional gain and / or the integral gain when the steering torque or the target current is greater than a predetermined threshold value in the initial state. The electric power steering device is further set to the second proportional gain and / or the second integral gain, and the electric power steering device further includes the proportional gain when the steering torque or the target current is equal to or less than a predetermined threshold value in the initial state. And / or third gain setting means for setting the integral gain to the first proportional gain and / or the first integral gain.

  Here, the second gain setting means sets the second proportional gain and / or the second integral gain when the initial state is detected and the steering torque is larger than the predetermined torque threshold. Alternatively, the second gain setting means sets the second proportional gain and / or the second integral gain when the initial state is detected and the target current is larger than the predetermined current threshold.

  That is, even when the initial state is detected, if the steering torque or the target current is equal to or less than the predetermined threshold, the same gain as the first gain setting means is set by the third gain setting means. In other words, a gain smaller than that in the normal state is set only when the initial state is detected and the steering torque or the target current is larger than the predetermined threshold.

  Here, when the steering torque is larger than the predetermined torque threshold and when the target current is larger than the predetermined current threshold, as described above, a large steering torque is applied to the steering wheel. In other words, when a large steering torque is applied to the steering wheel, even if the electric power steering device is started or restarted, the followability of the steering assist force generated by the assist motor is reduced to reduce the steering assist force. Yes. Therefore, even in the above case, a good steering feeling can be obtained.

  On the other hand, when the steering torque is equal to or smaller than the predetermined torque threshold value or when the target current is equal to or smaller than the predetermined current threshold value, the steering assist force itself by the assist motor is in a small state. That is, in the above case, the steering feeling is not impaired even if the steering assist force by the assist motor is generated by the same followability as in the normal state. Furthermore, in this case, a good steering feeling can be obtained by generating a steering assist force with high followability.

  The second gain setting means sets the proportional gain and / or the integral gain to the second proportional gain and / or the second integral gain until a predetermined time elapses after detecting the initial state. You may make it do. In the above description, the first proportional gain and / or the first integral gain are set based on the steering torque or the target current even in the initial state. However, the present invention is not limited to this. That is, the second proportional gain and / or the second integral gain may be set only after the initial state is detected until a predetermined time elapses. In other words, even when the initial state is detected, when the predetermined time has elapsed since the initial state was detected, the first proportional gain and / or the first integral gain are set. As a result, even when the initial state is detected, when a certain amount of time has passed, the steering assist force by the assist motor can be generated with good steering followability, resulting in good steering feeling. Obtainable.

  The second gain setting means is both in the case of the above-described initial state, where the steering torque or the target current is not more than a predetermined threshold value, and when the predetermined time has elapsed since the detection of the above-described initial state. In consideration of the above, the second proportional gain and / or the second integral gain may be set. For example, the second gain setting means is in the initial state, when the steering torque or the target current is below a predetermined threshold, or when the predetermined time has elapsed since the detection of the initial state, whichever comes first Until then, the second proportional gain and / or the second integral gain may be set. In this case, both effects described above can be achieved.

  Here, when the proportional-plus-integral control means comprises only a proportional element, the first gain setting means, the second gain setting means, and the third gain setting means set only the proportional gain. Further, when the proportional-integral control means includes only an integral element, the first gain setting means, the second gain setting means, and the third gain setting means set only the integral gain. Further, when the proportional-integral control means includes a proportional element and an integral element, the first gain setting means, the second gain setting means, and the third gain setting means set the proportional gain and the integral gain.

(1.4) Second gain The second proportional gain and / or the second integral gain set by the second gain setting means described above may be a constant value. Here, the second proportional gain and the second integral gain may be different constant values or may be the same constant value. Further, the second proportional gain and / or the second integral gain may be 0 (zero). Thus, setting the second proportional gain and / or the second integral gain to a constant value facilitates the setting of the gain. In particular, when the second integral gain is set to 0, a steady deviation is more reliably generated. In this case, the actual current that actually flows through the assist motor is smaller than the target current set by the target current setting means. That is, particularly when the second integral gain is set to 0, in addition to lowering the steering followability, the steering assist force by the assist motor can be reduced by generating a steady deviation more reliably. Thereby, a favorable steering feeling can be obtained in the initial state.

  The second proportional gain and / or the second integral gain may be determined based on an elapsed time-gain relationship that increases with an elapsed time from when the initial state is detected. Here, the second proportional gain and the second integral gain may be determined based on different elapsed time-gain relationships. With respect to the elapsed time-gain relationship, for example, the relationship between the elapsed time and the gain may be a linear relationship or a curved relationship. As a result, since the steering followability gradually improves after the initial state is detected, it is possible to prevent the steering force from suddenly decreasing in the initial state and to improve the steering followability in the normal state. It is possible to provide better steering follow-up performance even before reaching. Therefore, a very good steering feeling can be obtained.

(2) Embodiment of the Second Invention As described above, the electric power steering device of the second invention is an assist motor, steering torque detection means, target current setting means, motor current detection means, and motor drive control means. And an assist permission signal output means.

  Here, the motor drive control means includes, for example, proportional-integral control means and motor drive means in the electric power steering apparatus of the first invention.

  Further, the assist permission signal output means may output the assist permission signal when a predetermined time has elapsed after detecting the initial state. That is, even when the steering torque or the target current is larger than a predetermined threshold, when a predetermined time has elapsed since the initial state was detected, an assist permission signal is output to the motor drive control means, and steering by the assist motor is performed. The generation of auxiliary power is allowed. Thus, by generating a good steering assist force when a certain amount of time (predetermined time) has elapsed from the initial state, it is possible to prevent the steering force from rapidly decreasing in the initial state and to some extent. When the time has elapsed, a good steering feeling can be obtained.

(1) 1st Example Next, an Example is given and this invention is demonstrated more concretely with reference to drawings. A block diagram of the overall configuration of the electric power steering apparatus of the first embodiment is shown in FIG. As shown in FIG. 1, the electric power steering apparatus includes a steering torque sensor (steering torque detection means) 1, a target current setting unit (target current setting means) 2, a subtractor 3, and a PI control unit (proportional integral control). Means) 4, inverter drive unit (motor drive unit) 5, assist motor 6, motor current detection unit (motor current detection unit) 7, initial state detection unit (initial state detection unit) 8, and gain setting unit. 9. Hereinafter, each part which comprises the electric power steering apparatus of 1st Example is demonstrated in detail.

(1.1) Steering torque sensor 1
The steering torque sensor 1 is a sensor that detects a steering torque Ts applied to a steering shaft (not shown). Here, the steering shaft connected to the steering wheel includes a torsion bar (not shown). A steering torque sensor 1 is attached to the torsion bar. When the steering wheel rotates, a rotational force is applied to the torsion bar, and the torsion bar is twisted according to the applied rotational force. The steering torque applied to the steering shaft corresponding to the twist of the torsion bar is detected by the steering torque sensor 1.

(1.2) Target current setting unit 2
The target current setting unit 2 first inputs the steering torque Ts detected by the steering torque sensor 1. And the phase compensation process of the inputted steering torque Ts is performed. Based on the steering torque Ts on which the phase compensation processing has been performed, a target current Im * to be supplied to the assist motor 6 is set. The target current Im * is set based on a target current map indicating the relationship of the target current Im * with respect to the steering torque Ts stored in advance.

(1.3) Subtractor 3
The subtractor 3 is a deviation current (deviation) ΔIm (= Im * −) obtained by subtracting a motor current Im detected by a motor current detection unit 7 described later from a target current Im * set by the target current setting unit 2. Im) is calculated.

(1.4) PI control unit 4
The PI control unit 4 receives the deviation current ΔIm calculated by the subtractor 3, performs proportional-integral control on the input deviation current ΔIm, and calculates a voltage command value Vm to be applied to the assist motor 6. In the proportional-integral control, the proportional gain Kp of the proportional element and the integral gain Ki of the integral element are set by the gain setting unit 9 described later. Note that, as the proportional gain Kp and the integral gain Ki are larger, the motor current Im can be quickly converged to the target current Im *. That is, the larger the proportional gain Kp and the integral gain Ki, the better the followability.

(1.5) Inverter drive unit 5, assist motor 6, motor current detection unit 7
The inverter drive unit 5 includes a PWM signal generation unit and an inverter circuit unit. The PWM signal generation unit calculates a PWM signal based on the voltage command value Vm output from the PI control unit 4. The inverter circuit unit is composed of a plurality of switching elements. In the inverter circuit unit, each switching element is driven based on the PWM signal output from the PWM signal generation unit, and supplies current to the assist motor 6. By supplying current to the assist motor 6, the assist motor 6 generates a steering assist force. The assist motor 6 is, for example, a DC motor or a brushless DC motor. The motor current detector 7 detects the motor current Im flowing through the assist motor 6 and outputs the detected motor current Im to the subtracter 3.

(1.6) Initial state detector 8
The initial state detection unit 8 detects an initial state in which the electric power steering device is in a start state or a restart state. Here, the case where the electric power steering apparatus is in the starting state is, for example, when the ignition switch is turned on. Moreover, the case where the electric power steering apparatus is in the restart state is, for example, when the failure is recovered after the failure diagnosis by the failure diagnosis. That is, the initial state detection unit 8 detects a state (initial state) when the electric power steering device starts to operate after the state where the electric power steering device is temporarily stopped. When the initial state is detected, the initial state detection unit 8 outputs initial state information indicating that the state is the initial state to the gain setting unit 9 described later.

(1.7) Gain setting unit 9
The gain setting unit 9 receives the initial state information output from the initial state detection unit 8. Then, based on the input initial state information, the proportional gain Kp and integral gain Ki of the PI control unit 4 described above are set. Specifically, the gain setting unit 9 includes an initial state information storage unit 91, a target current value determination unit 92, a timer 93, and a normal gain setting unit (first gain setting unit, A third gain setting unit 94 and an initial gain setting unit (second gain setting unit) 95 are included. Hereinafter, each part which comprises the gain setting part 9 is demonstrated in detail.

(1.7.1) Initial state information storage unit 91
The initial state information storage unit 91 first inputs and stores the initial state information output from the initial state detection unit 8. The initial state information storage unit 91 changes and stores the initial state information according to a determination result by a target current value determination unit 92 described later. Further, the initial state information is changed and stored by the timer 93.

(1.7.2) Target current value determination unit 92
The target current value determination unit 92 inputs the target current Im * set by the target current setting unit 2. Then, the target current value determination unit 92 compares the absolute value of the input target current Im * with a determination current (predetermined current threshold) Im0 stored in advance, and the absolute value of the target current Im * is determined as the determination current. It is determined whether it is larger than Im0. When the absolute value of the target current Im * is equal to or smaller than the determination current Im0, an initial state end process is performed on the initial state information storage unit 91. Here, the initial state end process is a process of changing the initial state information to information indicating that the initial state information is not the initial state when the initial state information stored in the initial state information storage unit 91 is the initial state information. It is. The determination current Im0 does not decrease the steering feeling even when a current corresponding to the determination current Im0 is supplied to the assist motor 6 when a steering torque corresponding to the determination current Im0 is applied to the steering wheel. The current value is about.

(1.7.3) Timer 93
The timer 93 counts the elapsed time from when the initial state detection unit 8 detects the initial state. Specifically, the timer 93 starts counting up the timer counter t when the initial state information indicating that the initial state is output from the initial state detection unit 8. Then, the timer 93 outputs the timer counter t to the initial state information storage unit 91.

(1.7.4) Normal gain setting unit 94
The normal gain setting unit 94 sets a normal proportional gain (first proportional gain) Kp1 that is a proportional gain Kp in a normal state and a normal integral gain (first integral gain) Ki1 that is an integral gain Ki in a normal state. Specifically, the normal gain setting unit 94 first reads the initial state information stored in the initial state information storage unit 91. When the read initial state information is information indicating that the initial state is not the initial state, the normal gain setting unit 94 changes the proportional gain Kp and the integral gain Ki of the PI control unit 4 to the normal proportional gain Kp1 and the normal integral gain Ki1. Set each. Here, the normal state means a state different from the initial state, and means a state that is not the initial state.

(1.7.5) Initial gain setting unit 95
The initial gain setting unit 95 sets an initial proportional gain (second proportional gain) Kp2 that is a proportional gain Kp in an initial state and an initial integral gain (second integral gain) Ki2 that is an integral gain Ki in an initial state. Specifically, the initial gain setting unit 95 first reads the initial state information stored in the initial state information storage unit 91. When the read initial state information is information indicating that the initial state is the initial state information, the initial gain setting unit 95 sets the proportional gain Kp and the integral gain Ki of the PI control unit 4 as the initial proportional gain Kp2 and the initial integral gain Ki2. Set to each.

  Here, the initial proportional gain Kp2 is smaller than the normal proportional gain Kp1 and is a constant value. The initial integration gain Ki2 is a constant value that is smaller than the normal integration gain Ki1.

(1.8) Processing Operation of Gain Setting Unit 9 Next, the processing operation of the gain setting unit 9 will be described with reference to FIG. FIG. 2 is a flowchart showing the processing operation of the gain setting unit 9.

  The processing operation of the gain setting unit 9 first reads the initial state information stored in the initial state information storage unit 91 (step S1). Here, when the initial state is detected by the initial state detection unit 8, the initial state information stored in the initial state information storage unit 91 is information indicating that it is the initial state. On the other hand, when the initial state is not detected by the initial state detection unit 8, the initial state information stored in the initial state information storage unit 91 is information indicating that the initial state is not the initial state.

  Subsequently, it is determined whether or not the initial state information stored in the initial state information storage unit 91 is information indicating that it is an initial state (step S2). If the initial state information is information indicating that the initial state is not the initial state (step S2: No), that is, if the initial state detecting unit 8 has not detected the initial state, the normal gain setting unit 94 sets the normal proportional gain Kp1. The proportional gain Kp of the proportional element of the PI control unit 4 is set (step S3). Furthermore, the normal gain setting unit 94 sets the normal integral gain Ki1 as the integral gain Ki of the integral element of the PI control unit 4 (step S3). That is, when the initial state is not detected, PI control is performed using the normal proportional gain Kp1 and the normal integral gain Ki1. Then, the process ends.

  On the other hand, when the initial state information stored in the initial state information storage unit 91 is information indicating that the initial state is the initial state (step S2: Yes), that is, when the initial state detection unit 8 detects the initial state, the target current The value determination unit 92 reads the target current Im * (step S4).

  Subsequently, the target current value determination unit 92 compares the read absolute value of the target current Im * with a previously stored determination current Im0, and determines whether the absolute value of the target current Im * is greater than the determination current Im0. It is determined whether or not (step S5). When the absolute value of the target current Im * is equal to or smaller than the determination current Im0 (step S5: No), the target current value determination unit 92 performs an initial state end process (step S6). That is, the target current value determination unit 92 changes the initial state information stored in the initial state information storage unit 91 to information indicating that the initial state is not the initial state.

  Then, when the initial state end processing is performed by the target current value determination unit 92, the normal gain setting unit 94 sets the normal proportional gain Kp1 as the proportional gain Kp of the proportional element of the PI control unit 4 (step S3). Furthermore, the normal gain setting unit 94 sets the normal integral gain Ki1 as the integral gain Ki of the integral element of the PI control unit 4 (step S3). That is, even when the initial state is detected, if the absolute value of the target current Im * is equal to or less than the determination current Im0, PI control is performed using the normal proportional gain Kp1 and the normal integral gain Ki1. Then, the process ends.

  On the other hand, when the absolute value of the target current Im * is larger than the determination current Im0 (step S5: Yes), the initial proportional gain Kp2 is set as the proportional gain Kp of the proportional element of the PI controller 4 by the initial gain setting unit 95. (Step S7). Further, the initial gain setting unit 95 sets the initial integral gain Ki2 as the integral gain Ki of the integral element of the PI control unit 4 (step S7). That is, when the initial state is detected and the absolute value of the target current Im * is larger than the determination current Im0, the initial proportional gain Kp2 and the initial integral gain Ki2 that are smaller than the normal proportional gain Kp1 and the normal integral gain Ki1. Is PI controlled. That is, in this case, the steering followability is lowered, and as a result, the steering assist force is reduced.

  Subsequently, the timer 93 starts counting up the timer counter t (step S8). Subsequently, the timer counter t is compared with a predetermined counter T1 stored in advance in the timer 93 to determine whether or not the timer counter t is equal to or greater than the predetermined counter T1 (step S9). Here, immediately after detecting the initial state, the timer counter t is not greater than or equal to the predetermined counter T1. If the timer counter t is not greater than or equal to the predetermined counter T1 (step S9: No), the process is terminated as it is. In this case, the initial state information stored in the initial state information storage unit 91 stores information indicating that the initial state is the initial state. Accordingly, when the gain setting process is subsequently performed, it is determined that the initial state information in step S2 is information indicating that it is in the initial state, and the process proceeds to step S4.

  That is, after the initial state is detected, until the absolute value of the target current Im * becomes equal to or smaller than the determination current Im0, PI control is performed based on the initial proportional gain Kp2 and the initial integral gain Ki2 until the timer counter t reaches the predetermined counter T1. Is done.

  When the timer counter t becomes equal to or greater than the predetermined counter T1 (step S9: Yes), an initial state end process is performed by the timer 93 (step S10). That is, the timer 93 changes the initial state information stored in the initial state information storage unit 91 to information indicating that it is not in the initial state. That is, when the timer counter t becomes equal to or greater than the predetermined counter T1, the initial state is terminated, and PI control is performed using the normal proportional gain Kp1 and the normal integral gain Ki1.

(1.9) Changes in proportional gain Kp and integral gain Ki Here, after the initial state is detected by the initial state detector 8, the state where the absolute value of the target current Im * is greater than the determination current Im0 continues. Changes in the proportional gain Kp and the integral gain Ki of the PI control unit 4 will be described with reference to FIG. FIG. 3A shows a proportional gain Kp with respect to the timer counter (elapsed time) t. FIG. 3B is a diagram showing the integral gain Ki with respect to the timer counter (elapsed time) t.

  As shown in FIGS. 3A and 3B, when the initial state is detected and until the timer counter t reaches T1, the proportional gain Kp is the initial proportional gain Kp2, and the timer counter t is equal to or greater than T1. The proportional gain Kp is usually the proportional gain Kp1. The integration gain Ki is the initial integration gain Ki2 from when the initial state is detected until the timer counter t reaches T1, and when the timer counter t is equal to or greater than T1, the integration gain Ki is the normal integration gain Ki1. is there.

(2) First Modification of First Embodiment Although the initial proportional gain Kp2 and the initial integral gain Ki2 in the first embodiment are both constant values, they are not limited to this. For example, the initial proportional gain Kp2 and the initial integral gain Ki2 may change with the elapsed time. For example, the initial gain setting unit 95 determines the initial proportional gain Kp2 and the initial integral gain Ki2 based on the following formula 1, respectively.

  Here, the proportional gain initial value Kp0 and the integral gain initial value Ki0 are values smaller than the normal proportional gain Kp1 and the normal integral gain Ki1, respectively. For example, the proportional gain initial value Kp0 and the integral gain initial value Ki0 are set to the same values as the initial proportional gain Kp2 and the initial integral gain Ki2 in the first embodiment. The proportional gain setting coefficient G1 and the integral gain setting coefficient G2 will be described with reference to FIG. FIG. 4A shows a proportional gain setting coefficient G1 and an integral gain setting coefficient G2 for the timer counter t. As shown in FIG. 4A, both the proportional gain setting coefficient G1 and the integral gain setting coefficient G2 are linearly increased with respect to the timer counter t. Specifically, when the timer counter t is 0, the proportional gain setting coefficient G1 and the integral gain setting coefficient G2 are 0. As the timer counter t increases, the proportional gain setting coefficient G1 and the integral gain setting coefficient G2 increase linearly. When the timer counter t is the predetermined counter T1, the proportional gain setting coefficient G1 and the integral gain setting coefficient G2 are 1.

  Changes in the initial proportional gain Kp2 and the initial integral gain Ki2 in this case will be described with reference to FIGS. FIG. 4B shows an initial proportional gain Kp2 for the timer counter t. FIG. 4C shows the initial integration gain Ki2 for the timer counter t. As shown in FIG. 4B, the initial proportional gain Kp2 is a proportional gain initial value Kp0 when an initial state is detected. As the timer counter t increases, the initial proportional gain Kp2 increases linearly. When the timer counter t is the predetermined counter T1, the initial proportional gain Kp2 coincides with the normal proportional gain Kp1.

  Further, as shown in FIG. 4C, the initial integral gain Ki2 is an integral gain initial value Ki0 when an initial state is detected. As the timer counter t increases, the initial integration gain Ki2 increases linearly. When the timer counter t is the predetermined counter T1, the initial integration gain Ki2 is equal to the normal integration gain Ki1.

  As described above, the initial proportional gain Kp2 and the initial integral gain Ki2 are gradually improved as time passes after the initial state is detected. When the timer counter t reaches the predetermined counter T1, the initial proportional gain Kp2 and the initial integral gain Ki2 are made to coincide with the normal proportional gain Kp1 and the normal integral gain Ki1, respectively. That is, the steering follow-up performance is gradually improved by increasing the initial proportional gain Kp2 and the initial integral gain Ki2 over time. As a result, the steady deviation gradually decreases, and the motor current flowing through the assist motor gradually increases with respect to the target current. That is, the steering assist force gradually increases with time.

  Further, when the initial state is detected and a predetermined time elapses, the proportional gain Kp and the integral gain Ki are continuous during the transition from the initial proportional gain Kp2 and the initial integral gain Ki2 to the normal proportional gain Kp1 and the normal integral gain Ki1. Changes. As a result, the steering assist force changes continuously. That is, a very good steering feeling can be obtained.

(3) Second Modification of First Example In the target current value determination unit 92 of the gain setting unit 9 of the first example, a determination result of whether or not the absolute value of the target current Im * is larger than the determination current Im0. However, the present invention is not limited to this.

  For example, the target current value determination unit 92 of the first embodiment may be replaced with a steering torque value determination unit. The steering torque value determination unit inputs the steering torque Ts detected by the steering torque sensor 1. The steering torque value determination unit compares the absolute value of the input steering torque Ts with a determination torque value (predetermined torque threshold) Ts0 stored in advance, and the absolute value of the steering torque Ts is determined as the determination torque value Ts0. Determine if greater than. When the absolute value of the steering torque Ts is equal to or less than the determination torque value Ts0, the initial state end process is performed on the initial state information storage unit 91. As described above, the initial state end process is a process of changing to information indicating that the initial state is not the initial state when the initial state information stored in the initial state information storage unit 91 is the information indicating the initial state. The determination torque value Ts0 means that the target current Im * calculated based on the steering torque Ts0 is supplied to the assist motor 6 when the steering torque Ts corresponding to the determination torque value Ts0 is applied to the steering wheel. However, the steering torque value is set so as not to lower the steering feeling.

  The initial gain setting unit 95 in the first modification of the first embodiment sets the initial proportional gain Kp2 and the initial integral gain Ki2 based on Equation 1, but is not limited thereto. For example, the initial proportional gain Kp2 and the initial integral gain Ki2 may be determined based on a map of each gain with respect to the elapsed time stored in advance. Further, the initial proportional gain Kp2 and the initial integral gain Ki2 may be calculated based on a relational expression or a map that increases in a curve with the passage of time.

(4) Second Embodiment Next, an electric power steering apparatus according to a second embodiment will be described with reference to FIGS. FIG. 5 is a block diagram of the overall configuration of the electric power steering apparatus of the second embodiment. FIG. 6 is a flowchart showing the permission signal generation output process.

  As shown in FIG. 5, the electric power steering apparatus according to the second embodiment includes a steering torque sensor (steering torque detecting means) 1, a target current setting unit (target current setting means) 2, a subtractor 3, and PI control. Unit (proportional integral control means) 4, inverter drive part (motor drive means) 5, assist motor 6, motor current detection part (motor current detection means) 7, and initial state detection part (initial state detection means) 8 And a permission signal generation output unit 10. The PI control unit 4 and the inverter drive unit 5 serve as an electric motor drive control unit (electric motor drive control means). Here, in the configuration of the electric power steering apparatus of the second embodiment, the same components as those of the electric power steering apparatus of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. Of the configuration of the electric power steering device of the second embodiment, the configurations different from the configuration of the electric power steering device of the first embodiment are the permission signal generation output unit 10 and the motor drive control unit, and therefore only this. This will be described in detail below.

(4.1) Permission signal generation output unit 10
The permission signal generation output unit 10 receives the initial state information output from the initial state detection unit 8. When the motor drive control unit determines that the drive control is possible according to the input initial state information, a permission signal (assist permission signal) is output to the motor drive control unit.

  The permission signal generation / output unit 10 includes a target current value determination unit 101, a permission signal output unit (assist permission signal output unit) 102, and a timer 103. The target current value determination unit 101 inputs the target current Im * set by the target current setting unit 2. Then, the target current value determination unit 101 compares the absolute value of the input target current Im * with a determination current (predetermined current threshold) Im0 stored in advance, and the absolute value of the target current Im * is determined as the determination current. It is determined whether it is larger than Im0. Then, this determination result is output to the permission signal output unit 102. The determination current Im0 does not decrease the steering feeling even when a current corresponding to the determination current Im0 is supplied to the assist motor 6 when a steering torque corresponding to the determination current Im0 is applied to the steering wheel. The current value is about.

  The permission signal output unit 102 outputs a permission signal for starting or restarting the motor drive control unit based on the initial state information output from the initial state detection unit 8 and the determination result of the target current value determination unit 101. Decide whether to output. Further, the permission signal output unit 102 determines whether or not to output a permission signal based on a timer counter t output from the timer 103 described later. When the permission signal output unit 102 determines to output the permission signal, the permission signal output unit 102 outputs a permission signal to the motor drive control unit.

  The timer 103 counts an elapsed time from when the initial state detection unit 8 detects the initial state. Specifically, the timer 103 starts counting up the timer counter t when the initial state information is output from the initial state detector 8. Then, the timer 103 outputs the timer counter t to the permission signal output unit 102.

(4.2) Electric Motor Drive Control Unit The electric motor drive control unit includes the PI control unit 4 and the inverter drive unit 5 as described above. And when this electric motor drive control part has stopped drive control, after the permission signal is output from the permission signal output part 102, drive control is started or restarted. Here, the case where the electric motor drive control unit stops the drive control is a case where the electric power steering apparatus is in an initial state. That is, when the electric power steering apparatus is in the initial state, the motor drive control unit does not start or restart the drive control until the permission signal output unit 102 outputs the permission signal.

(4.3) Permission signal generation output processing operation Next, the permission signal generation output processing in the permission signal generation output unit 10 will be described with reference to the flowchart of FIG. First, the permission signal output unit 102 reads the initial state information output from the initial state detection unit 8 (step S11). Subsequently, it is determined whether or not the read initial state information is information indicating that it is an initial state (step S12). If the read initial state information is information indicating that the initial state is not the initial state (step S12: No), that is, if the initial state detection unit 8 has not detected the initial state, a permission signal is output (step S12). S13). Then, the process ends.

  On the other hand, when the read initial state information is information indicating that it is the initial state (step S12: Yes), that is, when the initial state detection unit 8 detects the initial state, the target current value determination unit 101 detects the target current. Im * is read (step S14). Subsequently, the target current value determination unit 101 compares the read absolute value of the target current Im * with a previously stored determination current Im0 to determine whether the absolute value of the target current Im * is greater than the determination current Im0. It is determined whether or not (step S15). Then, the target current value determination unit 101 outputs this determination result to the permission signal output unit 102.

  When the permission signal output unit 102 inputs a determination result that the absolute value of the target current Im * is equal to or less than the determination current Im0 (step S15: No), a permission signal is output (step S13). ). Then, the process ends.

  On the other hand, when the determination result that the absolute value of the target current Im * is larger than the determination current Im0 is input in the permission signal output unit 102 (step S15: Yes), the timer counter t of the timer 103 is incremented. Start (step S16). Subsequently, the timer counter t is compared with a predetermined counter T1 stored in advance in the timer 103 to determine whether or not the timer counter t is equal to or greater than the predetermined counter T1 (step S17). Here, immediately after detecting the initial state, the timer counter t is normally not greater than or equal to the predetermined counter T1. If the timer counter t is not greater than or equal to the predetermined counter T1 (step S17: No), the process returns to step S14 and the process is repeated.

  Then, when the process is repeated and the timer counter t becomes equal to or greater than the predetermined counter T1 (step S17: Yes), the permission signal output unit 102 outputs a permission signal (step S13). Then, the process ends.

  In other words, when the initial state is detected, when the absolute value of the target current Im * is equal to or less than the determination current Im0, or when the elapsed time since the initial state has been detected has passed a predetermined time, the permission signal Is output. When the permission signal is output, the electric motor drive control unit starts or restarts the drive control.

(5) Modification of Second Embodiment In the target current value determination unit 101 of the permission signal generation output unit 10 of the second embodiment, it is determined whether or not the absolute value of the target current Im * is larger than the determination current Im0. However, it is not limited to this.

  For example, the target current value determination unit 101 of the second embodiment may be replaced with a steering torque value determination unit. The steering torque value determination unit inputs the steering torque Ts detected by the steering torque sensor 1. The steering torque value determination unit compares the absolute value of the input steering torque Ts with a determination torque value (predetermined torque threshold) Ts0 stored in advance, and the absolute value of the steering torque Ts is determined as the determination torque value Ts0. Determine if greater than. Then, the steering torque value determination unit outputs the determination result to the permission signal output unit 102.

  In this case, the permission signal output unit 102 determines whether or not to output a permission signal for starting or restarting drive control to the motor drive control unit based on the determination result of the steering torque value determination unit. Specifically, when the absolute value of the steering torque Ts is equal to or less than the determination torque value Ts0, the permission signal is output to the motor drive control unit. The determination torque value Ts0 means that the target current Im * calculated based on the steering torque Ts0 is supplied to the assist motor 6 when the steering torque Ts corresponding to the determination torque value Ts0 is applied to the steering wheel. However, the steering torque value is set so as not to lower the steering feeling.

1 is a block diagram of an overall configuration of an electric power steering apparatus according to a first embodiment. 5 is a flowchart showing a processing operation of a gain setting unit 9. (A) It is a figure which shows the proportional gain Kp with respect to the timer counter (elapsed time) t in 1st Example. (B) It is a figure which shows the integral gain Ki with respect to the timer counter t. (A) It is a figure which shows the proportional gain setting coefficient G1 and the integral gain setting coefficient G2 with respect to the timer counter t in the 1st modification of 1st Example. (B) It is a figure which shows the proportional gain Kp with respect to the timer counter t. (C) It is a figure which shows the integral gain Ki with respect to the timer counter t. It is a block diagram of the whole structure of the electric power steering apparatus of 2nd Example. It is a flowchart which shows a permission signal production | generation output process.

Explanation of symbols

1: Steering torque sensor (steering torque detection means) 2: Target current setting section (target current setting means) 3: Subtractor 4: PI control section (proportional integration control means) 5: Inverter drive section (motor drive) Means), 6: Assist motor, 7: Motor current detection unit (motor current detection unit), 8: Initial state detection unit (initial state detection unit), 9: Gain setting unit, 10: Permission signal generation output unit, 91: Initial state information storage unit, 92: target current value determination unit, 93: timer, 94: normal gain setting unit (first gain setting unit, third gain setting unit), 95: initial gain setting unit (second gain setting unit) ), 101: target current value determination unit, 102: permission signal output unit (assist permission signal output means), 103: timer

Claims (7)

An assist motor to assist the steering force;
Steering torque detecting means for detecting steering torque applied to the steering shaft;
Target current setting means for setting a target current to be supplied to the assist motor based on the steering torque;
Motor current detection means for detecting a motor current flowing in the assist motor;
Proportional-integral control means including at least one of a proportional element and an integral element based on a deviation between the target current and the motor current;
Motor drive means for driving the assist motor based on the output of the proportional-integral control means;
In an electric power steering apparatus comprising:
further,
An initial state detecting means for detecting an initial state which is a start state or a restart state of the electric power steering device;
First gain setting means for setting the proportional gain of the proportional element and / or the integral gain of the integral element to the first proportional gain and / or the first integral gain when not in the initial state;
Second gain setting means for setting the proportional gain and / or the integral gain to a second proportional gain smaller than the first proportional gain and / or a second integral gain smaller than the first integral gain in the initial state; ,
An electric power steering apparatus comprising: The second gain setting means sets the proportional gain and / or the integral gain to the second proportional gain and / or the first gain when the steering torque or the target current is larger than a predetermined threshold in the initial state. Set to 2 integral gain,
Further, the proportional gain and / or the integral gain are set to the first proportional gain and / or the first integral gain in the initial state when the steering torque or the target current is equal to or less than a predetermined threshold. The electric power steering apparatus according to claim 1, further comprising third gain setting means.   The second gain setting means sets the proportional gain and / or the integral gain to the second proportional gain and / or the second integral gain until a predetermined time elapses after the initial state is detected. The electric power steering apparatus according to claim 1 or 2, wherein   The electric power steering apparatus according to any one of claims 1 to 3, wherein the second proportional gain and / or the second integral gain is a constant value.   The first proportional gain and / or the second integral gain is determined based on an elapsed time-gain relationship that increases with an elapsed time from when the initial state is detected. The electric power steering device according to any one of claims 3 to 4. An assist motor to assist the steering force;
Steering torque detecting means for detecting steering torque applied to the steering shaft;
Target current setting means for setting a target current to be supplied to the assist motor based on the steering torque;
Motor current detection means for detecting a motor current flowing in the assist motor;
Motor drive control means for driving and controlling the assist motor based on a deviation between the target current and the motor current;
In an electric power steering apparatus comprising:
further,
An initial state detecting means for detecting an initial state which is a start state or a restart state of the electric power steering device;
An assist permission signal output means for outputting an assist permission signal to the electric motor drive control means when the initial state is detected and the steering torque or the target current is not more than a predetermined threshold;
With
The electric power steering apparatus according to claim 1, wherein the electric motor drive control means starts or restarts the drive control when the assist permission signal is output.   The electric power steering apparatus according to claim 6, wherein the assist permission signal output means outputs the assist permission signal when a predetermined time has elapsed since the initial state was detected.

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