JP3560024B2 - Electric power steering device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electric power steering device that applies an auxiliary steering torque to a steering system of a vehicle by an electric motor, and more particularly to an electric power steering device that enables reliable unloader control even in the case of sudden steering of the steering system. is there.
[0002]
[Prior art]
2. Description of the Related Art As a vehicle steering device, a so-called electric power steering device that reduces the steering force of a driver by adding an auxiliary steering torque by an electric motor to a steering system when a steering wheel is operated has recently become widespread. This electric power steering device basically detects a steering torque of a steering system accompanying an operation of a steering wheel, and controls an auxiliary steering torque of the electric motor according to a direction and a magnitude of the detected torque. Is configured.
[0003]
In the above-described electric power steering apparatus, when a large auxiliary steering torque is applied by the electric motor in the vicinity of the maximum steering angle of the steering system, a large impact occurs when the steering system reaches the maximum steering angle, and in rare cases, The steering system including the electric motor may be locked. Therefore, in this type of electric power steering device, when the steering angle of the steering system approaches the maximum steering angle, so-called unloader control is adopted, in which the auxiliary steering torque by the electric motor is reduced and corrected to protect the steering system. (See Japanese Utility Model Application Laid-Open No. 60-193868).
[0004]
[Problems to be solved by the invention]
By the way, in the conventional unloader control of the electric power steering device,When the steering angle of the steering system exceeds a predetermined steering angle in the vicinity of the maximum steering angle, the auxiliary steering torque by the electric motor is reduced, and the steering feeling is reduced at medium to high speeds of the vehicle, or the maximum steering angle in an emergency or the like. Difficult to steer untilThere is a fear.
[0005]
Therefore, the present inventionEasy steering up to the maximum steering angle when the vehicle is at medium or high speedIt is an object to provide an electric power steering device.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a steering torque sensor for detecting a steering torque of a steering system of a vehicle, a steering angle sensor for detecting a steering angle of the steering system, and an auxiliary steering torque added to the steering system. An electric motor, and a control device that controls an auxiliary steering torque of the electric motor based on at least a detection signal of the steering torque sensor. An unloader correction unit that reduces and corrects the auxiliary steering torque of the electric motor when the steering angle exceeds a predetermined steering angle near the maximum steering angle. The unloader correction unit performs steering based on a detection signal of a steering speed of the steering system. The higher the speed is, the more the correction amount for reducing the auxiliary steering torque is increased and corrected.Also, when the vehicle speed is equal to or higher than a predetermined vehicle speed, the correction for reducing the auxiliary steering torque is avoided based on a detection signal of a vehicle speed sensor that detects the speed of the vehicle.It is configured as a means.
[0007]
In the electric power steering device according to the present invention, the steering torque sensor detects the steering torque of the steering system accompanying the operation of the steering wheel and the like, and the steering angle sensor detects the steering angle of the steering system. When the steering angle of the steering system is smaller than the predetermined steering angle, the control device controls the auxiliary steering torque of the electric motor based on the steering torque of the steering system. Here, when the steering angle exceeds a predetermined steering angle near the maximum steering angle, the unloader correction unit of the control device corrects and reduces the auxiliary steering torque of the electric motor. At this time, the unloader correction unit increases and corrects the reduction correction amount of the auxiliary steering torque of the electric motor as the steering speed of the steering system increases, and reduces the auxiliary steering torque of the electric motor more quickly.Further, based on the detection signal of the vehicle speed sensor, the unloader correction unit avoids the correction of the reduction of the auxiliary steering torque of the electric motor when the vehicle speed is equal to or higher than the predetermined vehicle speed. As a result, even when the steering angle of the steering system exceeds a predetermined steering angle in the vicinity of the maximum steering angle, the auxiliary steering torque by the electric motor is obtained. At times, the steering can be smoothly and suddenly increased to the maximum steering angle.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of an electric power steering device according to the present invention will be described with reference to the drawings. In the drawings to be referred to, FIG. 1 is a configuration diagram of a steering system to which an electric power steering device of one embodiment is applied, and FIG. 2 is a block configuration diagram of the electric power steering device of one embodiment.
[0010]
Before describing the electric power steering device of one embodiment, first, the structure of a steering system to which the electric power steering device is applied will be described with reference to FIG. The steering system is a so-called rack and pinion type steering system. A lower end of a steering shaft 2 integrally connected to a steering wheel 1 is connected to a pair of universal joints 4 connected to each other via a connection shaft 3. 4 is connected to an input shaft 5 </ b> A of the steering torque sensor 5. The pinion 6A of the rack and pinion mechanism 6 is formed integrally with the output shaft of the steering torque sensor 5.
[0011]
The rack and pinion mechanism 6 includes a rack shaft 6C formed with rack teeth 6B that mesh with the pinion 6A, and knuckle arms attached to left and right front wheels 7, 7 of the vehicle at both ends of the rack shaft 6C. (Not shown) are connected via tie rods 8, 8, respectively. A ball screw portion 9A of the ball screw mechanism 9 is formed coaxially with the rack shaft 6C, and a ball nut 9B that meshes with the ball screw portion 9A is disposed around the rack shaft 6C in a state where the rack shaft 6C passes therethrough. The motor 10 is fixed to a rotor 10A.
[0012]
Here, as shown in FIGS. 1 and 2, an electric power steering apparatus according to one embodiment includes a vehicle speed sensor 11 for detecting a rotation speed of a transmission output shaft (not shown), and at least the vehicle speed sensor 11 and the steering torque sensor. 5, a motor driving circuit 13 for inputting an output signal of the control device 12, a current value supplied from the motor driving circuit 13 to the motor 10, and the signal is detected. A current sensor 14 for outputting to the control device 12, a voltage sensor 15 for detecting a voltage value applied to the electric motor 10 and outputting the signal to the control device 12, and a steering wheel attached to the steering torque sensor 5. And an angle sensor 16.
[0013]
The steering torque sensor 5 detects the direction and magnitude of the steering torque according to the torsion angle between the input shaft 5A and the pinion 6A as the output shaft, and sends a steering torque signal TS as a detection signal to the control device 12. Output. Further, the vehicle speed sensor 11 outputs a vehicle speed signal VP corresponding to the rotation speed of a transmission output shaft (not shown) to the control device 12.
[0014]
The current sensor 14 includes a resistor or a Hall element connected in series to the electric motor 10 composed of a DC servo motor, and sends a motor current signal IM corresponding to the direction and magnitude of the electric current flowing through the electric motor 10 to the control device 12. Output. The voltage sensor 15 outputs a motor voltage signal VM corresponding to the voltage applied to the electric motor 10 to the control device 12 by being connected in parallel to the electric motor 10. Then, the steering angle sensor 16 outputs a steering angle signal θS corresponding to the steering angle of the steering wheel 1 to the control device 12.
[0015]
The control device 12 includes an input / output interface I / O between the steering torque sensor 5, the vehicle speed sensor 11, the current sensor 14, the voltage sensor 15, the steering angle sensor 16, and the like, and an analog signal input from these sensors. A / D converter that converts the data into a digital signal, a ROM that stores various data and programs, a RAM that temporarily stores various data, and a CPU that performs various arithmetic processes are provided as hardware. . As a software configuration, as shown in FIG. 2, a target current value setting unit 12A, an unloader correction unit 12B, a deviation calculation unit 12C, a PID control unit 12D, a PWM signal generation unit 12E, and a motor rotation speed calculation unit 12F are provided. I have. On the other hand, the motor drive circuit 13 includes a gate drive circuit 13A and a bridge circuit 13B.
[0016]
The target current value setting section 12A of the control device 12 receives the vehicle speed signal VP output from the vehicle speed sensor 11 and converts the steering torque signal TS output from the steering torque sensor 5 into a digital signal. Is entered. The target current value setting unit 12A is configured to generate a target current value signal for causing the electric motor 10 to generate an auxiliary steering torque having a basic characteristic that increases as the steering torque of the steering system increases and decreases as the vehicle speed increases. IT is retrieved from a data area having the steering torque signal TS and the vehicle speed signal VP as addresses, and the retrieved target current value signal IT is output to the unloader correction unit 12B.
[0017]
The unloader correction unit 12B includes, in addition to the target current value signal IT, a vehicle speed signal VP output from the vehicle speed sensor 11, a steering angle signal θS output from the steering angle sensor 16, and the motor rotation speed calculation unit. Rotational angular velocity signals MVEL output from 12F are respectively input. As will be described later, the unloader correction unit 12B performs reduction correction on the target current value signal IT and outputs the corrected target current value signal IT 'to the deviation calculation unit 12C.
[0018]
The motor current signal IM output from the current sensor 14 is converted into a digital signal and input to the deviation calculator 12C in addition to the corrected target current value signal IT '. The deviation calculator 12C calculates a deviation between the correction target current value signal IT 'and the motor current signal IM, and outputs the deviation signal? I to the PID controller 12D.
[0019]
The PID control unit 12D drives the electric motor 10 so that the deviation converges to zero by performing processes such as proportional (P), integral (I), and differentiation (D) on the deviation signal ΔI. Is output to the PWM signal generation unit 12E. The PWM signal generation unit 12E generates a PWM signal VO for performing a PWM (pulse width modulation) operation of the electric motor 10 based on the drive control signal SO, and supplies the PWM signal VO to the gate drive circuit 13A of the electric motor drive circuit 13. Output.
[0020]
The motor current signal IM output from the current sensor 14 and the motor voltage signal VM output from the voltage sensor 15 are converted into digital signals and input to the motor rotation speed calculation unit 12F. When the voltage of the motor 10 is VM, the current is IM, the resistance is RM, and the induced voltage coefficient is KP, the motor rotation speed calculation unit 12F calculates the rotation angular speed MVEL of the motor 10 by the following equation (1). The rotation angular velocity signal MVEL is output to the unloader correction unit 12B as a steering speed signal of the steering system.
MVEL = (VM−IM × RM) / KP (1)
[0021]
On the other hand, the gate drive circuit 13A of the motor drive circuit 13 switches the bridge circuit 13B based on the PWM signal VO. As shown in FIG. 3, the bridge circuit 13B includes four power FETs (field effect transistors) T1, T2, T3, and T4 forming a bridge circuit between a DC 12V power supply (vehicle battery) and the motor 10. It has. The gate drive circuit 13A outputs a drive signal corresponding to the magnitude of the deviation signal ΔI to one of the gates G1 and G2 of the power FET (T1, T2) according to the polarity of the deviation signal ΔI, and outputs the other. Outputs an off signal. At this time, an ON signal is output to one of the gates G3, G4 of the power FET (T3, T4), and an OFF signal is output to the other. For example, when a drive signal is output to the gate G1 of the power FET (T1), an ON signal is output to the gate G4 of the power FET (T4), and the gates G2 and G3 of the other power FETs (T2, T3) are output. Outputs an off signal.
[0022]
Here, when the steering angle of the steering system exceeds a predetermined steering angle near the maximum steering angle, the unloader correction unit 12B of the control device 12 reduces the target current value signal so as to reduce the auxiliary steering torque by the electric motor 10. It has a function of adding reduction correction to IT and increasing and correcting the amount of reduction correction applied to the target current value signal IT as the steering speed of the steering system increases. As shown in FIG. 4, the unloader correction unit 12B includes an offset amount setting unit 12B1, a control steering angle calculation unit 12B2, an unloader ratio setting unit 12B3, an unloader ratio correction amount setting unit 12B4, an unloader ratio correction calculation unit 12B5, and a target current. It comprises a value correction unit 12B6. Hereinafter, the function of each unit of the unloader correction unit 12B will be sequentially described.
[0023]
The offset amount setting unit 12B1 stores the offset amount α in a data area having the vehicle speed VP as an address, and instantaneously searches for the offset amount α according to the input of the vehicle speed signal VP from the vehicle speed sensor 11. The characteristic of the offset amount α is set so that, for example, as shown in the graph of FIG. 5, the vehicle speed VP is “0 degree” when the vehicle speed is less than 5 km / h, and is “50 degrees” when the vehicle speed VP is 10 km / h or more. I have.
[0024]
The control steering angle calculation unit 12B2 receives the steering angle signal θS output from the steering angle sensor 16 and the signal of the offset amount α output from the offset amount setting unit 12B1. Then, a value β obtained by subtracting the offset amount α from the steering angle θS is output to the unloader ratio setting unit 12B3 as a control steering angle signal β.
[0025]
The unloader ratio setting unit 12B3 stores the unloader ratio R in a data area having the control steering angle β as an address, and instantaneously sets the unloader ratio R in response to the input of the control steering angle signal β from the control steering angle calculator 12B2. To search. Then, it outputs the signal of the retrieved unloader ratio R to the unloader ratio correction operation unit 12B5. For example, as shown in the graph of FIG. 6, the characteristic of the unloader ratio R is “1” when the control steering angle β is, for example, less than 220 degrees, and gradually decreases at a constant reverse gradient when the control steering angle β exceeds 220 degrees, and becomes 270 degrees. Is set to “0”. In the present embodiment, 270 degrees is the maximum steering angle, and 220 degrees is the predetermined steering angle.
[0026]
The unloader ratio correction amount setting unit 12B4 includes a vehicle speed signal VP output from the vehicle speed sensor 11, a steering angle signal θS output from the steering angle sensor 16, and a rotation angular speed signal MVEL output from the motor rotation speed calculation unit 12F. Enter The unloader ratio correction amount setting unit 12B4 stores the unloader ratio correction amount A in a data area whose address is the rotational angular velocity MVEL. The unloader ratio correction amount setting unit 12B4 calculates the unloader ratio correction amount according to the rotation angular velocity signal MVEL under the condition that the steering angle θS is larger than, for example, 220 degrees and the vehicle speed VP is lower than, for example, 10 km / h. Search for A instantly. Then, a signal of the retrieved unloader ratio correction amount A is output to the unloader ratio correction operation unit 12B5. As shown in the graph of FIG. 7, for example, the characteristic of the unloader ratio correction amount A is “0” when the rotational angular velocity MVEL is less than “50 degrees / second”, and is constant when the rotational angular velocity MVEL exceeds “50 degrees / second”. It is set to increase gradually with a gradient.
[0027]
The unloader ratio correction calculator 12B5 receives the unloader ratio R signal output from the unloader ratio setting unit 12B3 and the unloader ratio correction amount A signal output from the unloader ratio correction amount setting unit 12B4. Then, a value obtained by subtracting the unloader ratio correction amount A from the unloader ratio R is output to the target current value corrector 12B6 as a signal of the corrected unloader ratio R '.
[0028]
The target current value correction unit 12B6 receives the target current value signal IT output from the target current value setting unit 12A and the corrected unloader ratio R 'signal output from the unloader ratio correction calculation unit 12B5. Then, a value obtained by multiplying the target current value signal IT by the modified unloader ratio R 'is output to the deviation calculator 12C as a corrected target current value signal IT'.
[0029]
In the electric power steering apparatus according to the embodiment configured as described above, the steering torque sensor 5 detects the direction and magnitude of the steering torque generated in the steering system in accordance with the operation of the steering wheel 1 shown in FIG. Then, the detected steering torque signal TS is output to the control device 12. The vehicle speed sensor 11 detects the speed of the vehicle, and outputs the detected vehicle speed signal VP to the control device 12. Further, the steering angle sensor 16 detects the steering angle of the steering system, and outputs the detected steering angle signal θS to the control device 12.
[0030]
In the control device 12, when the target current value setting unit 12A shown in FIG. 2 receives the steering torque signal TS and the vehicle speed signal VP, the target current value setting unit 12A increases with an increase in the steering torque of the steering system and increases the vehicle speed. A target current value signal IT for causing the electric motor 10 to generate an auxiliary steering torque having a basic characteristic that decreases with the change is instantaneously searched, and the target current value signal IT is output to the unloader correction unit 12B.
[0031]
In the unloader correction unit 12B, as shown in FIG. 4, the offset amount setting unit 12B1 is based on the vehicle speed signal VP. The signal of the amount α is output to the control steering angle calculation unit 12B2. Subsequently, based on the steering angle signal θS and the signal of the offset amount α, the control steering angle calculation unit 12B2 outputs a value β obtained by subtracting the offset amount α from the steering angle θS to the unloader ratio setting unit 12B3 as the control steering angle signal β. I do. Then, the unloader ratio setting unit 12B3 outputs a signal of the unloader ratio R corresponding to the control steering angle signal β to the unloader ratio correction operation unit 12B5.
[0032]
On the other hand, in the unloader ratio correction amount setting unit 12B4 that inputs the vehicle speed signal VP, the steering angle signal θS, and the rotation angular speed signal MVEL, as shown in the flowchart of FIG. 8, it is determined whether the steering angle θS is greater than 220 °. It is determined (step S1), and then it is determined whether the vehicle speed VP is lower than 10 km / h (step S2). When the steering angle θS is larger than 220 degrees and the vehicle speed VP is lower than 10 km / h, the unloader ratio correction amount setting unit 12B4 instantaneously searches for the unloader ratio correction amount A according to the rotation angular speed signal MVEL. The signal is output to the unloader ratio correction calculator 12B5 (step S3).
[0033]
The unloader ratio correction calculator 12B5, which inputs the signal of the unloader ratio R and the signal of the unloader ratio correction amount A, calculates a value obtained by subtracting the unloader ratio correction amount A from the unloader ratio R as a correction unloader ratio R ′ signal. Output to the value correction unit 12B6. The target current value correction unit 12B6 generates a target current value signal IT based on the target current value signal IT from the target current value setting unit 12A and the corrected unloader ratio R ′ from the unloader ratio correction calculation unit 12B5. A value obtained by multiplying the corrected unloader ratio R 'is output to the deviation calculator 12C as a corrected target current value signal IT'.
[0034]
Thereafter, in the control device 12, the deviation calculation unit 12C outputs a deviation signal ΔI between the correction target current value signal IT ′ from the unloader correction unit 12B and the motor current signal IM from the current sensor 14 to the PID control unit 12D. , The PID control unit 12D outputs a drive control signal SO for causing the deviation to converge to zero to the PWM signal generation unit 12E, and the PWM signal generation unit 12E outputs the PWM signal VO corresponding to the drive control signal SO to the electric motor drive circuit 13. Output to The electric motor drive circuit 13 drives the electric motor 10 to rotate in response to the PWM signal VO from the control device 12, so that in the steering system shown in FIG. This is applied to the rack shaft 6C via the ball screw mechanism 9, and the steering force of the steering wheel 1 is reduced.
[0035]
Here, in the electric power steering apparatus according to one embodiment, when the vehicle speed becomes, for example, 10 km / h or more after the start of the vehicle, the offset amount setting unit 12B1 of the unloader correction unit 12B sets the offset amount α to “50 degrees”. Output a signal. Therefore, if the maximum value of the steering angle θS of the steering system is, for example, 270 degrees, the control steering angle calculation unit 12B2 always outputs the control steering angle signal β of less than 220 degrees, and the unloader ratio setting unit 12B3 sets the unloader ratio R as A signal of "1" is always output. At this time, the unloader ratio correction amount setting unit 12B4 stops outputting the unloader ratio correction amount A because the vehicle speed is higher than 10 km / h. In other words, a signal of “0” is output as the unloader ratio correction amount A. As a result, the unloader ratio correction calculator 12B5 always outputs a signal of "1" to the target current value corrector 12B6 as the corrected unloader ratio R '.
[0036]
Therefore, the target current value corrector 12B6 outputs the same value as the target current value signal IT to the deviation calculator 12C as a corrected target current value signal IT '. That is, when the vehicle speed is higher than, for example, 10 km / h, the unloader control for reducing and correcting the auxiliary steering torque of the electric motor 10 is avoided.
[0037]
On the other hand, when the vehicle travels at an extremely low speed lower than 5 km / h, for example, the offset amount setting unit 12B1 outputs a signal of “0 degrees” as the offset amount α, so that the control steering angle calculation unit 12B2 performs control that matches the steering angle θS. And outputs the steering angle signal β. In this case, if the steering angle θS is less than 220 degrees, the control steering angle calculation unit 12B2 outputs a control steering angle signal β that matches the steering angle θS, so that the unloader ratio setting unit 12B3 outputs a signal of “1” as the unloader ratio R. Output. At this time, the unloader ratio correction amount setting unit 12B4 outputs a signal of “0” as the unloader ratio correction amount A because the steering angle θS is less than 220 degrees. Therefore, also in this case, as in the case where the vehicle speed is higher than 10 km / h, the unloader control for reducing and correcting the auxiliary steering torque of the electric motor 10 is avoided.
[0038]
Here, when the steering angle θS exceeds 220 degrees when the vehicle speed is lower than 5 km / h, for example, when the vehicle speed is lower than 5 km / h, such as when the vehicle is put in a garage, the offset amount setting unit 12B1 outputs a signal of “0 degrees” as the offset amount α. And the control steering angle calculation unit 12B2 outputs a control steering angle signal β exceeding 220 degrees which coincides with the steering angle θS. Therefore, the unloader ratio setting unit 12B3 outputs the control steering angle signal β from “1” in accordance with the control steering angle signal β. A signal having a characteristic that gradually decreases to “0” is output as an unloader ratio R. At this time, if the steering speed of the steering system is low and the rotation angular velocity signal MVEL is correspondingly equal to or less than a predetermined value, the unloader ratio correction amount setting unit 12B4 outputs a signal of “0” as the unloader ratio correction amount A. As a result, the unloader ratio correction calculator 12B5 outputs a signal between “1” and “0” corresponding to the control steering angle signal β as the corrected unloader ratio R ′ to the target current value corrector 12B6.
[0039]
Therefore, the target current value correction unit 12B6 outputs a value smaller than the target current value signal IT to the deviation calculation unit 12C as a corrected target current value signal IT '. That is, when the steering angle θS exceeds 220 degrees when traveling at an extremely low speed where the vehicle speed is lower than 5 km / h, unloader control for reducing and correcting the auxiliary steering torque of the electric motor 10 is executed.
[0040]
On the other hand, when the steering angle θS exceeds 220 degrees due to sudden steering during extremely low speed traveling at a vehicle speed lower than 5 km / h, the unloader ratio setting unit 12B3 changes from “1” to “0” according to the control steering angle signal β. A signal having a gradually decreasing characteristic is output as an unload ratio R. At this time, the unloader ratio correction amount setting unit 12B4 outputs, as the unloader ratio correction amount A, a signal having a characteristic that gradually increases from “0” according to the rotation angular speed signal MVEL because the rotation angular speed signal MVEL is equal to or more than a predetermined value. . As a result, the unloader ratio correction calculating unit 12B5 gradually increases the unloader ratio from “0” to “0” according to the rotational angular velocity signal MVEL from the unloader ratio R between “1” and “0” according to the control steering angle signal β. The value obtained by subtracting the correction amount A is output to the target current value correction unit 12B6 as a signal of the correction unloader ratio R '. The value of the modified unloader ratio R 'decreases as the rotational angular velocity signal MVEL increases, that is, as the steering speed of the steering system increases.
[0041]
Therefore, the target current value correction unit 12B6 corrects the reduction correction amount of the target current value signal IT to increase according to the increase of the steering speed of the steering system, and calculates the correction target current value signal IT ′ that has been reduced and corrected to a smaller value by the deviation calculation unit. Output to 12C. That is, when the steering angle θS exceeds 220 degrees due to abrupt steering when the vehicle speed is lower than 5 km / h, the auxiliary steering torque of the electric motor 10 is reduced and corrected more rapidly as the steering speed increases. Also in the case of steering, the auxiliary steering torque of the electric motor 10 can be reduced quickly, and reliable unloader control can be performed.
[0042]
In the electric power steering device of the present invention, the steering speed of the steering system does not necessarily need to be obtained from the rotational angular speed MVEL of the electric motor 10, and may be obtained by differentiating the steering angle signal θS from the steering angle sensor 16 with time. .
[0043]
【The invention's effect】
As described above, in the electric power steering apparatus of the present invention, the steering torque sensor detects the steering torque of the steering system and the steering angle sensor detects the steering angle of the steering system in accordance with the operation of the steering wheel or the like. When the steering angle of the steering system is smaller than the predetermined steering angle, the control device controls the auxiliary steering torque of the electric motor based on the steering torque of the steering system. Here, when the steering angle exceeds a predetermined steering angle near the maximum steering angle, the unloader correction unit of the control device corrects and reduces the auxiliary steering torque of the electric motor. At this time, the unloader correction unit corrects the auxiliary steering torque of the electric motor by increasing the reduction correction amount as the steering speed of the steering system increases.
[0044]
Therefore, according to the electric power steering apparatus of the present invention, the auxiliary steering torque of the electric motor can be quickly reduced even in the case of a sharp steering operation in which the steering angle of the steering system exceeds the predetermined steering angle near the maximum steering angle at a high steering speed. And reliable unloader control can be performed.
[0045]
AndIn the electric power steering apparatus according to the present invention, the unloader correction unit is configured to avoid the correction correction of the auxiliary steering torque of the electric motor when the vehicle speed is equal to or higher than the predetermined vehicle speed, based on the detection signal of the vehicle speed sensor.CageEven when the steering angle of the steering system exceeds a predetermined steering angle in the vicinity of the maximum steering angle, the auxiliary steering torque by the electric motor can be obtained, so that a good steering feeling without a sense of incongruity can be obtained when the vehicle is running at medium to high speeds, such as in emergency. In, steering can be smoothly and suddenly performed up to the maximum steering angle.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a steering system to which an electric power steering device according to an embodiment of the present invention is applied.
FIG. 2 is a block configuration diagram of an electric power steering device according to one embodiment.
FIG. 3 is a circuit diagram of a bridge circuit of the electric power steering device according to one embodiment.
FIG. 4 is a block configuration diagram of an unloader correction unit of the electric power steering device according to the embodiment.
FIG. 5 is a characteristic graph of an offset amount subjected to data processing by an unloader correction unit of the electric power steering device according to the embodiment.
FIG. 6 is a characteristic graph of an unloader ratio for which the unloader correction unit of the electric power steering device according to the embodiment performs data processing.
FIG. 7 is a characteristic graph of an unloader ratio correction amount subjected to data processing by an unloader correction unit of the electric power steering device according to the embodiment.
FIG. 8 is a flowchart showing data processing in an unloader correction unit of the electric power steering device according to one embodiment.
[Explanation of symbols]
1: Steering wheel
2: Steering shaft
5: Steering torque sensor
6: Rack and pinion mechanism
9: Ball screw mechanism
10: Electric motor
11: Vehicle speed sensor
12: Control device
12A: target current value setting unit
12B: Unloader correction unit
12C: deviation calculator
12D: PID control unit
12E: PWM signal generation unit
12F: Motor rotation speed calculation unit
13: Motor drive circuit
13A: Gate drive circuit
13B: Bridge circuit
14: Current sensor
15: Voltage sensor
16: Rudder angle sensor

Claims (1)

A steering torque sensor that detects a steering torque of a steering system of a vehicle, a steering angle sensor that detects a steering angle of the steering system, an electric motor that adds an auxiliary steering torque to the steering system, and a detection signal of at least the steering torque sensor And a control device for controlling an auxiliary steering torque of the electric motor based on the steering angle. The auxiliary steering torque of the electric motor is reduced. When the steering speed is higher, the unloader correction unit is configured to reduce the auxiliary steering torque based on the detection signal of the steering speed of the steering system. with increasing fix the based on the detection signal of the vehicle speed sensor for detecting the speed of the vehicle, the vehicle speed is higher than a predetermined vehicle speed An electric power steering apparatus characterized by avoiding the decrease correction of the steering assist torque to come.

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