JP4415304B2 - Electric power steering control device for vehicle - Google Patents

Description

  The present invention relates to an electric power steering control device for a vehicle that assists an operation of a steering wheel with an electric motor.

  Conventionally, as shown in Patent Document 1, for example, steering torque is detected, and by controlling the rotation of the electric motor in accordance with the detected steering torque, an assist force is applied to the turning operation of the steering wheel. An electric power steering control device for a vehicle that is provided is well known. Further, in this device, by adding a control amount corresponding to the differential value obtained by differentiating the steering torque to the control amount corresponding to the steering torque, the inertial force of the electric motor at the start of the turning operation of the steering handle, Insufficient assist force due to steering torque due to friction is compensated.

  However, in the above-mentioned conventional device, the faster the steering wheel is turned, the more the steering torque differential value increases and the steering assist force by the electric motor increases. There is a problem that a great difference in steering reaction force experienced by the driver occurs between when the vehicle is quickly turned and a good steering feeling cannot be obtained. In addition, when the steering wheel turning operation is reversed, a state occurs in which the sign of the control amount according to the steering torque and the control amount according to the differential value of the steering torque are different, and the two control amounts are in conflict with each other. Because it may act in the direction, the driver may feel that the steering wheel has come out of the steering operation or may suddenly return the steering wheel. In this case as well, a good steering feeling cannot be obtained. There's a problem.

  Therefore, an electric power steering control device has been devised in which means for correcting the amount of current applied to the electric motor according to the steering speed of the steering wheel is provided in order to compensate for the inertial force of the electric motor (see Patent Document 2). ).

Japanese Patent Laid-Open No. 10-157636 Japanese Patent No. 3412579

  Since the example of Patent Document 2 includes the speed of the vehicle as a control condition, it is robust against changes in road surface conditions (friction coefficient, etc.) or driving conditions (weather conditions, etc.). It was difficult to prevent deterioration of the operation feeling due to the inertial force of the electric motor while ensuring that the controllability is not impaired even if it is slightly different from the model assumed in the design. In addition, in order to ensure robust stability, in addition to the vehicle speed, sensors and peripheral circuits that detect changes in road surface conditions or driving conditions are required, and this complicates the control, increasing program capacity, and controlling data. The capacity increases, and a high-performance microcomputer and a large-capacity memory must be used. This leads to an increase in the cost of the device.

  Against the background of the above problems, an object of the present invention is to provide an electric power steering control device that optimizes the steering feeling of the driver by achieving robust stability in addition to removing the uncomfortable feeling of the steering feeling due to the motor inertia force. For the purpose.

Means for Solving the Problems and Effects of the Invention

The present invention provides an electric power steering control device for solving the above problems. That is, according to claim 1,
An electric motor for applying an assisting force to the rotation operation of the steering wheel;
Steering torque detection means for detecting steering torque;
Steering angle detection means for detecting the steering angle of the steering wheel;
Feedforward compensation means for calculating a steering torque generated from the steering angle to the steering wheel;
Reference steering torque calculation means for calculating reference steering torque based on the calculation result of the feedforward compensation means;
Deviation calculating means for calculating a deviation between the reference steering torque and the steering torque detected by the steering torque detecting means;
Feedback compensation means for performing feedback compensation based on the deviation;
An adjuster for feedforward control for calculating a target torque based on the steering torque calculated by the feedforward compensation means ;
Requested torque calculation means for calculating the required torque by adding the output from the feedback compensation means and the target torque; and
Conversion means for converting the required torque into a command current value for commanding the amount of current flowing through the electric motor;
It is provided with.

According to the above configuration, first, when steering wheel angle information is input by turning the steering wheel, the reference steering torque can be obtained by feedforward control to control the electric motor. On the other hand, if there is a deviation between the steering wheel torque actually generated and the reference steering torque due to the presence of model errors and disturbances, the electric motor can be controlled by obtaining the necessary steering torque by feedback control. And robust stability can be achieved.

According to claim 2,
An electric motor for applying an assisting force to the rotation operation of the steering wheel;
Steering torque detection means for detecting steering torque;
Steering angle detection means for detecting the steering angle of the steering wheel;
Feedforward compensation means for calculating a steering angle generated from the steering torque to the steering wheel;
Reference steering angle calculation means for calculating a reference steering angle based on the calculation result of the feedforward compensation means;
Deviation calculating means for calculating a deviation between the reference steering angle and the steering angle detected by the steering angle detecting means;
Feedback compensation means for performing feedback compensation based on the deviation;
An adjuster for feedforward control that calculates a target steering angle based on the steering angle calculated by the feedforward compensation means ;
Requested steering angle calculating means for calculating the required steering angle by adding the output from the feedback compensation means and the target steering angle;
Conversion means for converting the required steering angle into a command current value for commanding the amount of current flowing through the electric motor;
It is provided with.

According to the above configuration, first, when steering wheel torque information is input by turning the steering wheel, the reference steering angle can be obtained by feedforward control to control the electric motor. In addition, when there is a deviation between the steering wheel angle that actually occurs and the reference steering angle due to the presence of model errors and disturbances, the electric motor can be controlled by obtaining the necessary steering angle by feedback control. And robust stability can be achieved.

Further, the feedforward compensation means in the electric power steering control device of the present invention can include a vehicle speed detection means for detecting the vehicle speed, and the output of the feedforward compensation means can be made variable according to the detected vehicle speed. . According to this configuration, the electric motor can be controlled more finely by converting the target steering torque or the target steering angle obtained by the control into a command current value according to the characteristic according to the speed.

  By the way, the characteristics required for the control system are roughly divided into a target value response (feed forward) characteristic and a feedback characteristic. The target value response characteristic is a request to match the response characteristic of the control system to the desired response characteristic, and the feedback characteristic is the sensitivity characteristic or the robust stability (the actual control target) of the control target. That the controllability is not impaired even if the characteristic of the control system is slightly different from the model assumed in the control system design), and that the desired removal characteristic against disturbance and observation noise is obtained. Usually, a control system design employs a one-degree-of-freedom control system that calculates an operation amount using only deviation information between a target value and a control amount. The class of the value response characteristic is also limited, and the target value response characteristic and the feedback characteristic cannot be set independently.

  Therefore, a two-degree-of-freedom control system having two controllers using two pieces of information on the target value and the control amount available has been proposed. By configuring this control system, the two characteristics can be set independently. However, at the beginning of the proposal, the demand for control performance was not so strict and it was not necessary to use a two-degree-of-freedom control system, or it was difficult to realize a two-degree-of-freedom control device with the hardware technology at that time. , Attention was low. In recent years, the demand for control has become high, coupled with the advancement of hardware technology including high-performance microprocessors, the importance of two-degree-of-freedom control systems has been rediscovered, and theoretical and applied research has rapidly developed. is doing.

By applying this two-degree-of-freedom control system, the electric power steering control device for a vehicle according to the present invention can be easily realized. For example, when the steering wheel steering torque is obtained from the steering wheel steering angle, the operation is as follows. First, when steering wheel turning angle information is input by turning the steering wheel, it is possible to obtain an ideal steering wheel steering torque ( reference steering torque of the present invention) by feedforward control. In addition, if there is a difference between the actual steering torque and the ideal steering torque due to the presence of model errors and disturbances, the ideal steering steering torque can be obtained by feedback control, which is robust and stable. It becomes possible to aim at sex.

  As a result, only the steering wheel steering angle information and the steering torque need be input as input information, and other vehicle information such as vehicle speed (that is, sensors and peripheral circuits) is not an essential requirement for control. Large capacity memory is also unnecessary. Therefore, the electric power steering control device for a vehicle according to the present invention can be realized at low cost.

  With the electric power steering control device for a vehicle according to the present invention, it is possible to optimize the driver's steering feeling by achieving robust stability in addition to removing the uncomfortable feeling of the steering feeling due to the motor inertia force.

  The present invention achieves the object of optimizing the driver's steering feeling by an electric power steering control device for a vehicle to which a two-degree-of-freedom control system is applied.

Hereinafter, an electric power steering control device (hereinafter simply referred to as an electric power steering control device) for a vehicle according to a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a configuration diagram of an electric power steering control device 1. A steering handle 10 is connected to the steering shaft 12a. Further, the lower end of the steering shaft 12 a is connected to the torque sensor 11, and the upper end of the pinion shaft 12 b is connected to the torque sensor 11. Further, a pinion (not shown) is provided at the lower end of the pinion shaft 12 b, and this pinion is meshed with the rack bar 18 in the steering gear box 16. Further, one end of a tie rod 20 is connected to each end of the rack bar 18, and a steered wheel 24 is connected to the other end of each tie rod 20 via a knuckle arm 22. An electric motor 15 is attached to the pinion shaft 12b via a gear (not shown) to constitute a so-called column type electric power steering control device.

  The mounting position of the electric motor 15 is a rack type that is coaxially attached to the rack bar 18 in addition to the configuration of FIG. 1 or a pinion type that is attached to the steering gear box 16 and rotates the steering shaft 12a. May be.

  The torque sensor 11 detects the movement of the driver's steering handle 10 and corresponds to the steering force detecting means of the present invention. The torque sensor 11 is a well-known torque such as a torsion bar and a pair of resolvers installed apart from each other in the axial direction thereof. It consists of a detector. When the handle shaft 12a rotates, torque corresponding to the amount of rotation is detected, and the detected information is sent to the steering control unit 30.

  A steering angle sensor 13 for detecting the steering angle of the steering handle 10 is attached to the steering shaft 12a. The steering angle sensor 13 corresponds to the steering angle detection means of the present invention, and is composed of a known angle detection unit such as a rotary encoder or a resolver. The detected information is sent to the steering control unit 30.

  The steering control unit 30 includes a well-known CPU 31, RAM 32, ROM 33, I / O 34 which is an input / output interface, and a bus line 35 for connecting these components. The CPU 31 controls the program and data stored in the ROM 33 and RAM 32. The ROM 33 has a program storage area 33a and a data storage area 33b. A steering control program 33p is stored in the program storage area 33a. The data storage area 33b stores data necessary for the operation of the steering control program 33p.

  In the steering control unit 30, the CPU 31 executes a steering control program stored in the ROM 33, so that the electric motor 15 corresponding to the torque detected by the torque sensor 11 and the steering angle detected by the steering angle sensor 13 is driven. Torque is calculated, and a voltage for generating the calculated drive torque is applied to the electric motor 15 via the motor driver 14. The electric motor 15 is not particularly limited as long as it can be used in the electric power steering control device 1 of the present invention.

  FIG. 2 is a block diagram in which a two-degree-of-freedom control system is applied to an electric power steering control device. Reference numeral 41 denotes a feedforward compensator that performs a calculation for generating a steering torque with respect to an input steering angle, and a transfer function (ratio between input and output, the same applies hereinafter) is represented by H. In this embodiment, H × Θ is output with respect to the steering wheel steering angle Θ that is an input.

Reference numeral 42 denotes a reference input element for obtaining a reference steering torque T ₀ based on the input from the feedforward compensator 41, and the transfer function is represented by N. In this embodiment, N × H × Θ is output with respect to the input H × Θ from the feedforward compensator 41.

  Reference numeral 44 denotes an adjuster for setting the input from the feedforward compensator 41 to a value usable in the plant 47, and the transfer function is represented by D. In this embodiment, D × H × Θ is output for the input H × Θ from the feedforward compensator 41. Further, as will be described later, the transfer function D is determined to be an irreducible decomposition of the transfer function P of the plant 47 (a value divisible by the transfer function P, P = N / D).

  Reference numeral 45 denotes a feedback compensator for feedback control (details will be described later).

  Reference numeral 47 denotes an output-side control target called a plant. In this embodiment, the steering handle 10, the steering shaft 12a, the pinion shaft 12b, the pinion (not shown), the steering gear box 16, the rack bar 18, the tie rod 20, the knuckle arm 22, the electric motor 15 and the like shown in FIG. Is included.

The steering characteristic element 48 is one of feed-forward terms and is determined by the steering characteristic. The steering characteristic element 48 is a second-order parameter using the steering wheel inertia J _S and the steering wheel viscosity C _S generated in the direction opposite to the rotation direction of the steering wheel as parameters. Expressed as a transfer function. The steering characteristic element 48 is not involved in feedback compensation described later.

In the configuration of FIG. 2, when the steering wheel steering angle Θ is input, the feed forward compensator 41 multiplies the transfer function H and outputs H × Θ. The output from the feedforward compensator 41 is input to the regulator 44 and the reference input element generator 42. The regulator 44 multiplies the transfer function D to output D × H × Θ, and the reference input element generator 42 transmits it. The function N is multiplied to output the standard steering torque T ₀ = N × H × Θ.

When a disturbance such as a model error or a change in road condition occurs and a deviation e occurs between the reference steering torque T ₀ and the actual steering torque T _SN obtained from the torque sensor 11, the feedback compensator 45 performs the deviation. generating a value T _K such that the e zero and outputs. This _TK and the output (D × N × H × Θ) from the controller 44 are added, and this result is set as a required torque (= (D × N × H × Θ) + T _K ). The plant 47 is input as _a motor applied current ia that generates this required torque.

Then, the plant 47 obtains _a voltage for generating the motor applied current ia and applies it to the electric motor 15 included in the plant 47. The steering torque actually generated in the plant 47 is (N × H × Θ) + P × T _K
In this case, T _SN = N × H × Θ. Plus steering characteristic element 48 is the steering torque T _S felt by the driver to this value. That means
T _S = (N × H × Θ) + P × T _K + (J _S s ² + C _S s) (1)
It becomes.

On the other hand, when there is no deviation e between the reference steering torque T ₀ and the actual steering torque T _SN obtained from the torque sensor 11 (e = 0), the calculation by the feedback compensator 45 is not performed, and the feedback compensation amount _TK is zero. Therefore, the required torque in this case is D × N × H × Θ of the output value from the adjuster 44. The plant 47 is input as _a motor applied current ia that generates this required torque. Seek motor applied voltage for generating the applied motor current i _a In the plant 47, is applied to the electric motor 15 included in the plant 47.

The steering torque actually generated in the plant 47 is N × H × Θ, and in this case, T _SN = N × H × Θ. Plus steering characteristic element 48 is the steering torque T _S felt by the driver to this value. That means
T _S = (N × H × Θ) + (J _S s ² + C _S s)
It becomes. This is equivalent to the equation (2) with T _K = 0.

Therefore, regardless of the occurrence of disturbances such as changes in the model error and road conditions, the steering torque T _S can be expressed by equation (1). As shown in this block diagram (FIG. 2), it is understood that the steering torque calculation control of the electric power steering control device can be performed by the two-degree-of-freedom control system based on the combination of feedforward compensation and feedback compensation.

FIG. 3 is a block diagram showing an outline of the motor control process performed by the steering control unit 30. This represents the control structure represented by the block diagram of FIG. 2 in a form in which control processing can actually be performed. This process is repeatedly performed together with other processes of the steering control program 33p while the electric power steering control device 1 is operating. First, the actual steering torque T _SN detected by the torque sensor 11 is input to the comparison unit 53, and the steering angle Θ detected by the steering angle sensor 13 is input to the feedforward element calculation unit 51.

The feedforward element calculation unit 51 calculates H × θ as described in FIG. 2 and outputs the result to the reference input element calculation unit 52 and the adjustment element calculation unit 54. The reference input element calculation unit 52 ( reference steering torque calculation means of the present invention) obtains the reference steering torque T ₀ (= N × H × θ) and outputs it to the comparison unit 53, and the adjustment element calculation unit 54 calculates the transfer function D. By multiplying, D × H × θ is output to the motor command current calculation unit 56.

The comparison unit 53 (deviation calculation means of the present invention) compares the actual steering torque T _SN obtained from the torque sensor 11 with the reference steering torque T ₀ from the input element calculation unit 52, and stabilizes the comparison result as the deviation e. Output to the compensation compensation calculation unit 55.

In stability compensation calculation unit 55 (the inertia compensation control amount calculation means of the present invention), calculates a correction torque T _K such that the input deviation e to zero and outputs a motor command current calculation section 56. When the deviation e is zero, the correction torque _TK is also zero.

The motor command current calculation unit 56 (conversion means of the present invention) outputs a value corresponding to the input D × H × Θ from the adjustment element calculation unit 54, and the obtained steering torque T _SN is added to the stabilization compensation calculation unit. This was a new steering torque T _SN by adding the correction torque T _K of from 55, the motor applied current i _a by the map data define the relationship between the steering torque T _SN and the motor applied current i _a stored in the ROM33 Calculate and output to the current control calculation unit 57.

Current control calculation section 57 included in the plant 47, to the electric motor 15 via a motor driver 14, the calculated voltage for generating the applied motor current i _a is applied, the motor actual current value obtained from the current sensor 8 and compared with the motor applied current i _a, performs drive control of the electric motor 15 included in the plant 47 so it matches.

  Hereinafter, an electric power steering control apparatus according to a second embodiment of the present invention will be described with reference to the drawings. The electric power steering apparatus according to the second embodiment is the same as the electric power steering apparatus according to the first embodiment of the present invention as shown in FIG. The description will be made using the reference numerals given to the respective components in FIG. 1 used in the description of the embodiment. 4 and 5, the difference from the first embodiment in the present invention is that the input or output parameter and the steering characteristic part are different, and the control structure does not change. Therefore, FIG. 2 and FIG. The description will be made using the reference numerals assigned to the respective components.

  Reference numeral 41 denotes a feedforward compensator that performs an operation for generating an ideal steering angle with respect to the input steering wheel torque T. A transfer function (input / output ratio, the same applies hereinafter) is represented by H. In this embodiment, the steering wheel torque T, which is an input, is multiplied by a transfer function H to output H × T.

Reference numeral 42 is a reference input element for obtaining a reference steering angle Θ ₀ based on the input from the feedforward compensator 41, and the transfer function is represented by N. In this embodiment, N × H × T is output for the input H × T from the feedforward compensator 41.

  An adjuster 44 outputs the input from the feedforward compensator 41 as a usable value in the plant 47, and the transfer function is represented by D. In this embodiment, D × H × T is output for the input H × T from the feedforward compensator 41. Further, as will be described later, the transfer function D is determined to be an irreducible decomposition of the transfer function P of the plant 47 (a value divisible by the transfer function P, P = N / D).

  Reference numeral 45 denotes a feedback compensator for feedback control (details will be described later).

  Reference numeral 47 denotes an output-side control target called a plant. In this embodiment, the steering handle 10, the steering shaft 12a, the pinion shaft 12b, the pinion (not shown), the steering gear box 16, the rack bar 18, the tie rod 20, the knuckle arm 22, the electric motor 15, and the like are included.

In the configuration of FIG. 4, when the steering torque T is input, the feedforward compensator 41 multiplies the transfer function H and outputs H × T. The output from the feedforward compensator 41 is input to the regulator 44 and the reference input element generator 42. The regulator 44 multiplies the transfer function D to output D × H × T, and the reference input element generator 42 transmits it. The reference steering angle Θ ₀ (= N × H × T) is output by multiplying the function N.

When a disturbance such as a model error or a change in road condition occurs and a deviation e occurs between the reference steering angle Θ ₀ and the actual steering angle Θ _SN obtained from the steering angle sensor 13, the feedback compensator 45 A value Θ _K is generated so that the deviation e is zero. The output from the regulator 44 and the theta _K a (D × N × H × T ) by adding, to the result required steering angle (= (D × N × H × T) + Θ K). The plant 47 is input as _a motor applied current ia that generates this required steering angle.

Then, the plant 47 obtains _a voltage for generating the motor applied current ia and applies it to the electric motor 15 included in the plant 47. The steering angle Θ _SN actually generated in the plant 47 is
Θ _SN = (N × H × T) + P × Θ _K (2)
It becomes.

On the other hand, when there is no deviation e between the reference steering angle Θ ₀ and the actual steering angle Θ _SN obtained from the steering angle sensor (e = 0), the calculation by the feedback compensator 45 is not performed, and the feedback compensation amount Θ _K is zero. Therefore, the required steering angle in this case is D × N × H × T of the output value from the adjuster 44. The plant 47 is input as _a motor applied current ia that generates this required steering angle. Seek motor applied voltage for generating the applied motor current i _a In the plant 47, is applied to the electric motor 15 included in the plant 47.

The steering angle Θ _SN actually generated in the plant 47 is
Θ _SN = (N × H × T)
It becomes. This is equivalent to the equation (2) in which Θ _K = 0.

Therefore, regardless of the occurrence of disturbances such as changes in the model error and road conditions, the steering angle theta _SN can be represented by the formula (2). As shown in this block diagram (FIG. 4), it is understood that the steering angle calculation control of the electric power steering control device can be performed by the two-degree-of-freedom control system based on the combination of feedforward compensation and feedback compensation.

FIG. 5 is a block diagram showing an outline of the motor control process performed by the steering control unit 30. This represents the control structure represented by the block diagram of FIG. 4 in a form in which control processing can actually be performed. This process is repeatedly performed together with other processes of the steering control program 33p while the electric power steering control device 1 is operating. First, the actual steering angle Θ _S detected by the steering angle sensor 13 is input to the comparison unit 53, and the steering wheel steering torque T detected by the torque sensor 11 is input to the feedforward element calculation unit 51.

The feedforward element calculation unit 51 obtains H × T as described in FIG. 4 and outputs the result to the reference input element calculation unit 52 (the reference steering angle calculation means of the present invention) and the adjustment element calculation unit 54. Yes. The reference input element calculation unit 52 obtains the reference steering angle θ ₀ (= N × H × T) and outputs it to the comparison unit 53, and the adjustment element calculation unit 54 multiplies the transfer function D to obtain D × H × T as a motor command. This is output to the current calculation unit 56.

The comparison unit 53 (deviation calculation means of the present invention) compares the steering wheel steering angle Θ _SN with the reference steering angle Θ ₀ from the input element calculation unit 52 and outputs the comparison result to the stabilization compensation calculation unit 55 as a deviation e. is doing.

In stability compensation calculation unit 55 (the inertia compensation control amount calculation means of the present invention), calculates a correction steering angle theta _K such that the input deviation e to zero and outputs a motor command current calculation section 56.

The motor command current calculation unit 56 (conversion unit of the present invention) outputs a value corresponding to the input D × H × T from the adjustment element calculation unit 54, and the obtained steering angle Θ _SN is added to the stabilization compensation calculation unit. the plus correction steering angle theta _K from 55 as a new steering angle theta _SN, applied motor current i _a by the map data define the relationship between the steering angle theta _SN and the motor applied current i _a stored in the ROM33 Is output to the current control calculation unit 57.

Current control calculation section 57 included in the plant 47, to the electric motor 15 via a motor driver 14, the calculated voltage for generating the applied motor current i _a is applied, the motor actual current value obtained from the current sensor 8 and compared with the motor applied current i _a, performs drive control of the electric motor 15 included in the plant 47 so it matches.

(Modification of Example 2)
A modification of the second embodiment of the present invention will be described with reference to FIGS. This shows that an equivalent function can be obtained even when a steering characteristic element is added as in the first embodiment of the present invention. In the block diagram of FIG. 7 second embodiment of the block diagram of FIG. 4 differs from the form of the present invention obtains a steering characteristic element 48 based on the steering angle theta _SN, this steering torque T In addition, it is input to the feedforward compensator 41. Also in the control block diagram of FIG. 8, a steering characteristic element calculation unit 58 and an addition calculation unit 59 are added to the control block diagram of FIG. 5 which is the second embodiment of the present invention.

As described above, the steering characteristic element 48 is determined by the steering characteristic, and is a second-order transfer function (J _S) using the steering wheel inertia J _S and the steering wheel viscosity C _S generated in the direction opposite to the rotation direction of the steering wheel as parameters. s ² + C _S s). By taking the steering characteristic element into account, fine control can be performed according to the type of steering.

    7 and 8, since the control other than obtaining the steering characteristic element 48 and adding it to the steering torque T is the same as that of the second embodiment of the present invention, the description thereof will be omitted.

  Next, the relationship between the steering angle and the steering torque in the electric power steering control device to which the present invention is applied will be described with reference to FIG. This is a relationship between the steering wheel angle and the steering torque when the steering wheel 10 is continuously rotated to the left and right at a cycle of about 2 Hz (that is, the rotation of the rightward rotation for 1 second and the leftward rotation for 1 second). When the horizontal axis (handle steering angle) of the graph is 0, the steering handle 10 is in the center (neutral position). When the steering handle 10 is turned to the right, a positive steering angle is obtained, and when the steering handle 10 is turned to the left, a negative steering angle is obtained. As for the steering torque, a positive steering torque is obtained when the steering handle 10 is turned to the right, and a negative steering torque is obtained when the steering handle 10 is turned to the left.

  FIG. 6A shows the relationship between the steering wheel angle and the steering torque in the electric power steering control device according to the prior art. In the range indicated by 61 in this figure and in the vicinity thereof, the steering torque is negative (left rotation) even if the steering angle increases in the positive (right rotation) direction even though the steering wheel 10 is turned to the right. Has increased in the direction. This occurs because the inertial force in the left rotation direction of the electric motor 15 remains and the electric motor 15 does not rotate right, which is the rotation direction of the steering handle 10. At this time, the driver feels a sense of slipping out of the steering operation of the steering wheel. Further, in the range indicated by 62 and in the vicinity thereof, the inertial force in the right rotation direction of the electric motor 15 remains despite the steering handle turning from the right rotation to the left rotation. A steering torque in the right rotation direction opposite to the rotation direction is generated, and the driver feels a sudden return of the steering wheel.

  FIG. 6B shows the relationship between the steering wheel angle and the steering torque in the electric power steering control apparatus to which the present invention is applied. According to this figure, it can be seen that the direction in which the steering torque is generated is in good agreement with the direction of rotation of the steering handle 10.

  Furthermore, the present invention can be applied to any system other than the electric power steering control device as long as the system obtains the steering wheel torque from the steering wheel steering angle or obtains the steering wheel steering angle from the steering wheel steering torque. In this system, the steering wheel and the tire are not mechanically connected, and a steer-by-wire device that transmits an instruction from the steering wheel to the tire by an electric signal, the steering angle of the steering wheel and the turning angle of the steered wheel There is a variable transmission ratio variable mechanism (Variable Gear Ratio Steering = VGRS).

  In the embodiment of the present invention described above, the parameter of the transfer function H of the feedforward compensator 41 does not include the vehicle speed. However, even if a method that includes the vehicle speed is included in the parameter of the transfer function H, human operation is performed. It is possible to improve the sense. For example, when the steering angle Θ or the steering torque T is input to the feedforward compensator 41, the transfer function H is increased when the vehicle speed is low, and the transfer function H is decreased when the vehicle speed is high. The transfer function H is changed accordingly. In this way, robust stability is ensured, and the driver's uncomfortable feeling with respect to steering is eliminated. The vehicle speed sensor 17 (vehicle speed detection means of the present invention) that detects the vehicle speed is configured by a known rotation detection unit that detects the rotation of the wheel 24 such as a rotary encoder or a tachometer.

  Although the embodiments of the present invention have been described above, these are merely examples, and the present invention is not limited to these embodiments, and the knowledge of those skilled in the art can be used without departing from the spirit of the claims. Various modifications based on this are possible.

The block diagram which shows the whole structure of the electric power steering control apparatus of this invention. The block diagram for demonstrating the calculation process of steering torque. Example 1 The block diagram for demonstrating a motor control process. Example 1 The block diagram for demonstrating the calculation process of a steering angle. (Example 2) The block diagram for demonstrating a motor control process. (Example 2) The figure which shows the relationship between a steering wheel steering angle and steering torque. The block diagram for demonstrating the calculation process of a steering angle. (Modification of Example 2) The block diagram for demonstrating a motor control process. (Modification of Example 2)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric power steering control apparatus 8 Current sensor 10 Steering handle 11 Torque sensor (steering torque detection means)
12a Steering shaft 13 Steering angle sensor (steering angle detection means)
15 Electric motor 17 Vehicle speed sensor (vehicle speed detection means)
30 Steering control unit (inertia compensation control amount calculation means, command torque calculation means, conversion means, target torque calculation means, target steering angle calculation means)
41 Feedforward Compensator 42 Reference Input Element Generator 44 Controller 45 Feedback Compensator 47 Plant 48 Steering Characteristic Element 51 Feedforward Element Calculation Unit 52 Input Element Calculation Unit 53 Comparison Unit 54 Adjustment Element Calculation Unit 55 Stabilization Compensation Calculation Unit 56 Motor command current calculator 57 Current control calculator

Claims (4)

An electric motor for applying an assisting force to the rotation operation of the steering wheel;
Steering torque detection means for detecting steering torque;
Steering angle detection means for detecting a steering angle of the steering wheel;
Feedforward compensation means for calculating a steering torque to be generated in the steering wheel from the steering angle;
Reference steering torque calculation means for calculating a reference steering torque based on the calculation result of the feedforward compensation means;
Deviation calculating means for calculating a deviation between the reference steering torque and the steering torque detected by the steering torque detecting means;
Feedback compensation means for performing feedback compensation based on the deviation;
An adjuster for feedforward control for calculating a target torque based on the steering torque calculated by the feedforward compensation means ;
A required torque calculating means for calculating a required torque by adding the output from the feedback compensation means and the target torque; and
Conversion means for converting the required torque into a command current value for commanding an amount of current flowing through the electric motor;
An electric power steering control device for a vehicle, comprising: An electric motor for applying an assisting force to the rotation operation of the steering wheel;
Steering torque detection means for detecting steering torque;
Steering angle detection means for detecting a steering angle of the steering wheel;
Feedforward compensation means for calculating a steering angle generated in the steering handle from the steering torque;
Reference steering angle calculation means for calculating a reference steering angle based on the calculation result of the feedforward compensation means;
Deviation calculating means for calculating a deviation between the reference steering angle and the steering angle detected by the steering angle detecting means;
Feedback compensation means for performing feedback compensation based on the deviation;
An adjuster for feedforward control that calculates a target steering angle based on the steering angle calculated by the feedforward compensation means ;
Requested steering angle calculation means for calculating the required steering angle by adding the output from the feedback compensation means and the target steering angle;
Conversion means for converting the required steering angle into a command current value for commanding an amount of current to flow through the electric motor;
An electric power steering control device for a vehicle, comprising: 3. The vehicle according to claim 1 , wherein a transfer function of the regulator is determined to be an irreducible decomposition of a transfer function of an output-side control target including the electric motor and a motor driving unit that drives the electric motor . Electric power steering control device. 4. The feedforward compensation means includes vehicle speed detection means for detecting a vehicle speed, and makes the output of the feedforward compensation means variable according to the detected vehicle speed. Vehicle electric power steering control device.

Images