JP2014051242A - Electric power steering system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering system that gives a good steering feeling by generating an appropriate assisting force while driving on a terrible road.SOLUTION: When a vehicle velocity is equal to or higher than a predetermined vehicle velocity within a predetermined time, the number of times by which an absolute value of a motor rotation-angle acceleration becomes equal to or larger than a predetermined motor rotation-angle acceleration is equal to or larger than a predetermined number of times, and an integrated value of an absolute value of a steering torque becomes equal to or larger than a predetermined value within the predetermined time, an assisting force is increased.

Description

  The present invention relates to an electric power steering apparatus.

  2. Description of the Related Art Conventionally, in an electric power steering apparatus that assists steering by an electric motor, the assist force is determined simply by the steering torque and the vehicle speed on a normal road or a bad road.

  However, in such a control method, when the vehicle travels on a rough road such as a gravel road, the steering wheel may be taken due to the kickback of the steering system. At this time, if the assist for normal running continues, there is a possibility that the straight running stability is impaired. Therefore, for example, in the electric power steering apparatus described in Patent Document 1, when it is determined that the time change rate of the steering torque exceeds a predetermined number of times within a predetermined time, the steering feeling is improved by increasing the assist force. I am trying.

JP 2002-302057 A

  However, if the steering torque is determined to be rough road driving only when the time change rate of the steering torque exceeds a predetermined number of times within a predetermined time and the assist force is increased, the road surface is dry and the driver When turning and turning back, there is a case where a sufficient steering feeling cannot be obtained due to a feeling of rudder slipping. Therefore, in order to perform control to increase the assist force from that during normal steering, it is necessary to grasp the exact vehicle state.

  An object of the present invention is to provide an electric power steering apparatus having a good steering feeling by generating an appropriate assist force on a rough road.

  In order to solve the above-described problems, the invention according to claim 1 is directed to a steering force assisting device provided to apply an assist force for assisting a steering operation to a steering system by a motor, and a steering torque detection for detecting a steering torque. Means for detecting a motor speed, motor rotation angle detection means for detecting the motor rotation angle, and motor rotation angular acceleration for calculating motor rotation angular acceleration from the motor rotation angle detected by the motor rotation angle detection means Based on the calculation means, the steering torque detected from the steering torque detection means, the assist force generation means for generating an assist force from the vehicle speed detected from the vehicle speed detection means, and the steering force assisting device based on the assist force generation means Control means for controlling the operation of the steering force assisting device by supplying driving power to a motor that is a driving source of In the obtained electric power steering apparatus, the control means determines that the number of times that the vehicle speed is equal to or higher than a predetermined vehicle speed within a predetermined time and the absolute value of the motor rotation angular acceleration is equal to or higher than a predetermined motor rotation angular acceleration is predetermined. The assist force is increased when the absolute value of the steering torque becomes a predetermined value or more within the predetermined time.

  In the electric power steering apparatus according to the present invention, the number of times that the vehicle speed is equal to or higher than the predetermined vehicle speed within a predetermined time and the absolute value of the motor rotational angular acceleration is equal to or larger than the predetermined motor rotational angular acceleration is a predetermined number. The assist force is increased when the absolute value of the steering torque becomes equal to or greater than a predetermined value within a predetermined time.

  That is, by detecting that the vehicle speed is equal to or higher than the predetermined vehicle speed, it is possible to grasp the state where the driver is stepping on the accelerator on a rough road. Further, by detecting that the absolute value of the motor rotation angular acceleration is greater than or equal to the predetermined motor rotation angular acceleration, it is possible to grasp the state where the driver is turning the steering wheel to the left or right on a rough road. Then, by detecting that the above operation has continued for a predetermined number of times within a predetermined time and that the integrated value of the absolute value of the steering torque is equal to or greater than the predetermined value, it is precisely that the driver feels a great sense of fatigue. Can be estimated. In this state, the assist force is increased to reduce the driver's fatigue.

  As a result, since it is possible to determine a bad road with high accuracy, the steering feeling can be improved by generating an appropriate assist force.

  According to a second aspect of the present invention, the control means increases the assist force, and then the vehicle speed is equal to or higher than a predetermined vehicle speed within a predetermined time, and the absolute value of the motor rotation angular acceleration is a predetermined motor rotation angle. The gist is to restore the normal assist force without increasing the assist force when the condition of acceleration or higher is not satisfied.

According to the above configuration, when the assist force is increased and the vehicle speed is not less than the predetermined vehicle speed and the absolute value of the motor rotation angular acceleration does not satisfy the condition of the predetermined motor rotation angular acceleration within the predetermined time. The assist force is not increased and is returned to the normal assist force.
As a result, the normal assist force is obtained after traveling on a rough road, so that it is possible to obtain a comfortable steering feeling without a feeling of rudder slipping.

  ADVANTAGE OF THE INVENTION According to this invention, the electric power steering apparatus with a favorable steering feeling can be provided by generating appropriate assist force in the driving | running | working on a rough road.

The schematic block diagram of an electric power steering device (EPS). The control block diagram of EPS. The block diagram of an Iq * electric current command value calculating part. The flowchart figure which shows the process sequence of an Iq * electric current command value calculating part.

Hereinafter, an embodiment of the present invention embodied in a column-type electric power steering apparatus (hereinafter referred to as EPS) will be described with reference to the drawings.
As shown in FIG. 1, in the EPS 1 of the present embodiment, a steering shaft 3 to which a steering 2 is fixed is connected to a rack shaft 5 via a rack and pinion mechanism 4. The rotation of the steering shaft 3 accompanying the steering operation is converted into a reciprocating linear motion of the rack shaft 5 by the rack and pinion mechanism 4. The steering shaft 3 of this embodiment is formed by connecting a column shaft 8, an intermediate shaft 9, and a pinion shaft 10. The reciprocating linear motion of the rack shaft 5 accompanying the rotation of the steering shaft 3 is transmitted to a knuckle (not shown) via tie rods 11 connected to both ends of the rack shaft 5, whereby the steered angle of the steered wheels 12. Has been changed.

  The EPS 1 controls the EPS actuator 24 (steering force assisting device) as a steering force assisting device that applies assisting force for assisting the steering operation to the steering system using the motor 21 as a driving source, and the operation of the EPS actuator 24. ECU27 which performs.

  The EPS actuator 24 of the present embodiment is a column type EPS actuator, and the motor 21 that is a drive source thereof is drivingly connected to the column shaft 8 via a speed reduction mechanism 23. The rotation of the motor 21 is decelerated by the speed reduction mechanism 23 and transmitted to the column shaft 8 so that the motor torque is applied to the steering system as an assist force.

  On the other hand, a vehicle speed sensor 25 (vehicle speed detection means), a torque sensor 26 (steering torque detection means), and a motor rotation angle sensor 22 (motor rotation angle detection means) are connected to the ECU 27. The vehicle speed V, the steering torque τ, and the motor rotation angle θm are detected based on the output signal.

  The torque sensor 26 is a twin resolver type torque sensor. The ECU 27 calculates a steering torque τ based on output signals from a pair of resolvers provided at both ends of a torsion bar (not shown). Further, the ECU 27 calculates a target assist force based on each of the detected state quantities, and assists the operation of the EPS actuator 24 through the supply of drive power to the motor 21 that is the drive source, that is, the assist that is given to the steering system. Control the power.

Next, an electrical configuration in the EPS 1 of the present embodiment will be described.
FIG. 2 is a control block diagram of the EPS 1 of the present embodiment. As shown in the figure, the ECU 27 supplies three-phase drive power to a motor 21 that is a drive source of the EPS actuator 24 based on a microcomputer 29 (control means) that outputs a motor control signal and the motor control signal. Drive circuit 40, and current sensors 30u, 30v, and 30w for detecting a U-phase current value Iu, a V-phase current value Iv, and a W-phase current value Iw that are supplied to the motor 21.

  The drive circuit 40 is a known PWM inverter (not shown) formed by connecting three arms corresponding to each phase in parallel with a pair of switching elements connected in series as a basic unit (arm). Further, the motor control signal output from the microcomputer 29 defines the on-duty ratio of each switching element constituting the motor drive circuit 40. A motor control signal is applied to the gate terminal of each switching element, and in response to the motor control signal, each switching element is turned on / off to generate three-phase motor driving power based on the power supply voltage of the battery 28. The motor 21 is configured to output.

  A motor rotation angle sensor 22 for detecting the motor rotation angle θm of the motor 21 is connected to the ECU 27. The microcomputer 29 is driven based on the phase current values Iu, Iv, Iw of the motor 21 and the motor rotation angle θm detected based on the output signals of these sensors, the steering torque τ, and the vehicle speed V. A motor control signal is output to the circuit 40.

  Each control block shown below is realized by a computer program executed by the microcomputer 29. The microcomputer 29 detects each state quantity at a predetermined sampling period, and generates a motor control signal by executing each arithmetic processing shown in the following control blocks every predetermined period.

  As shown in FIG. 2, the microcomputer 29 includes an Iq * current command value calculation unit 31 (assist force generation means) that calculates a q-axis current command value Iq * that controls the motor 21, and a motor control that controls the drive circuit 40. A motor control signal generation unit 44 for generating a signal.

The microcomputer 29 performs current feedback control in the d / q coordinate system by mapping the phase current values Iu, Iv, and Iw to the d / q coordinate system (d / q conversion).
Then, the PWM output unit 38 generates a DUTY command value for determining the on / off timing of the FET constituting the drive circuit 40, and outputs a gate on / off signal based on the DUTY command value.

Details of the Iq * current command value calculation unit 31 will be described based on the block diagram of the current command value calculation unit in FIG.
The Iq * current command value calculation unit 31 receives the vehicle speed V and the steering torque τ, and outputs an uncorrected q-axis current command value Iq **. The Iq ** calculation unit 32, the vehicle speed V, the steering torque τ, and The Iq ** correction calculation unit 33 is configured to output the Iq ** correction current value Iq0 with the motor rotation angle θm as an input. Further, the Iq * current command value calculation unit 31 includes an adder 50 that adds the uncorrected q-axis current command value Iq ** and the Iq ** corrected current value Iq0.
The Iq * current command value calculation unit 31 outputs the q-axis current command value Iq * generated by addition by the adder 50 to the motor control signal generation unit 44.

The Iq * current command value calculation unit 31 is processed based on a flowchart (described later) showing the processing procedure of the Iq * current command value calculation unit shown in FIG.
The Iq ** calculator 32 calculates the uncorrected q-axis current command value Iq ** from the steering torque / uncorrected q-axis current command value map (not shown) based on the input steering torque τ and the vehicle speed V. decide. Note that the steering torque / pre-correction q-axis current command value map is configured to determine a larger pre-correction q-axis current command value Iq ** as the vehicle speed V decreases with the same steering torque.

  The motor control signal generation unit 44 includes a d / q conversion calculation unit 34, a q-axis PID control unit 35, a d-axis PID control unit 36, a d / q reverse conversion calculation unit 37, and a PWM output unit 38.

  The U-phase current value Iu, the V-phase current value Iv, and the W-phase current value Iw input to the d / q conversion calculation unit 34 are d / q-converted to obtain a q-axis current value Iq and a d-axis current value Id. Become. The q-axis current value Iq is input to the subtractor 53. The subtractor 53 inputs the q-axis deviation current value ΔIq obtained by subtracting the q-axis current value Iq from the q-axis current command value Iq * output from the Iq * current command value calculation unit 31 to the q-axis PID control unit 35. . The q-axis voltage command value Vq * calculated by the q-axis PID control unit 35 is input to the d / q inverse conversion calculation unit 37.

  On the other hand, the d-axis current value Id converted by the d / q conversion calculation unit 34 is input to the subtractor 54. The subtractor 54 inputs a d-axis deviation current value ΔId obtained by subtracting the d-axis current value Id from the d-axis current command value Id * (Id * = 0) to the d-axis PID control unit 36. The d-axis voltage command value Vd * calculated by the d-axis PID control unit 36 is input to the d / q inverse conversion calculation unit 37.

  The q-axis voltage command value Vq * and the d-axis voltage command value Vd * input to the d / q reverse conversion calculation unit 37 are converted by the d / q reverse conversion calculation unit 37 into the U-phase voltage command value Vu * and V-phase. The voltage command value Vv * and the W-phase voltage command value Vw * are converted and input to the PWM output unit 38.

Next, a processing procedure of the Iq * current command value calculation unit by the microcomputer 29 of the present embodiment will be described with reference to FIG.
First, the microcomputer 29 determines whether or not the rough road determination flag FLG1 is set (FLG1 = “1”, step S100). When the rough road determination flag FLG1 is not set (FLG1 = "0", step S100, NO), the time measurement timer 1TR1 is incremented (TR1 = TR1 + 1, step S101).

  Next, the microcomputer 29 determines whether or not the time measurement timer 1TR1 is equal to or greater than the time measurement timer 1 time-up TR10 (step S102). Then, when the time measurement timer 1TR1 is smaller than the time measurement timer 1 time-up TR10 (TR1 <TR10, step S102: NO), the microcomputer 29 continues the microcomputer 29 so that the vehicle speed V is equal to or higher than the predetermined vehicle speed V0. Whether or not (step S103). When the vehicle speed V is smaller than the predetermined vehicle speed V0 (V <V0, step S103: NO), the microcomputer 29 sets the q-axis current command value Iq ** to the q-axis current command value Iq **. Then, the signal is output to the motor control signal generator 44 (step S104), and the process is terminated.

  On the other hand, when the vehicle speed V is equal to or higher than the predetermined vehicle speed V0 (V ≧ V0, step S103: YES), the microcomputer 29 determines that the driver is stepping on the accelerator on a rough road. Subsequently, the microcomputer 29 determines whether or not the absolute value of the motor rotation angular acceleration αm is greater than or equal to a predetermined motor rotation angular acceleration αm0 (step S105). When the absolute value of the motor rotational angular acceleration αm is smaller than the predetermined motor rotational angular acceleration αm0 (| αm | <αm0, step S105: NO), the microcomputer 29 corrects the q-axis current command value Iq * before correction. The q-axis current command value Iq ** is set and output to the motor control signal generation unit 44 (step S104), and the process ends. The motor rotation angular acceleration αm is calculated by differentiating the motor rotation angle detected by the motor rotation angle detection means by the motor rotation angle acceleration calculation means twice.

  Next, when the absolute value of the motor rotational angular acceleration αm is equal to or greater than the predetermined motor rotational angular acceleration αm0 (| αm | ≧ αm0, step S105: YES), the microcomputer 29 causes the driver to steer left and right on a rough road. It is judged that it is in a state where it is suddenly cut. Then, the microcomputer 29 increments the processing number counter CTR (CTR = CTR + 1, step S107). Subsequently, the microcomputer 29 adds the absolute value of the steering torque τ to the steering torque integrated value Τsum (Τsum = Τsum + | τ |, step S108).

  Then, the microcomputer 29 determines whether or not the processing number counter CTR is equal to or greater than the processing number counter count-up CTR0 (step S109). When the processing number counter CTR is smaller than the processing number counter count-up CTR0 (CTR <CTR0, step S109: NO), the microcomputer 29 sets the q-axis current command value Iq * to the q-axis current command value Iq before correction. ** is set and output to the motor control signal generation unit 44 (step S104), and the process ends.

  On the other hand, the microcomputer 29 determines whether or not the steering torque integrated value Τsum is greater than or equal to the predetermined steering torque integrated value Τsum0 when the processing number counter CTR is greater than or equal to the process number counter count-up CTR0 (CTR ≧ CTR0, step S109: YES). Is determined (step S110). When the steering torque integrated value Τsum is smaller than the predetermined steering torque integrated value Τsum0 (Τsum <Τsum0, step S110: NO), the microcomputer 29 sets the q-axis current command value Iq * to the q-axis current command value Iq before correction. ** is set and output to the motor control signal generation unit 44 (step S104), and the process ends.

  Next, when the steering torque integrated value Τsum is equal to or greater than the predetermined steering torque integrated value Τsum0 (Τsum ≧ Τsum0, step S110: YES), the microcomputer 29 causes the driver to feel considerably tired due to running on a rough road. It is determined that it is in a state. Then, the microcomputer 29 sets a rough road determination flag FLG1 (FLG1 = "1", step S111). The microcomputer 29 outputs a value obtained by adding the Iq ** corrected current value Iq0 to the uncorrected q-axis current command value Iq ** to the motor control signal generation unit 44 as the q-axis current command value Iq * (step S112). Then, the process ends. By performing the above-described series of operations, it is determined that the assist force can be increased and the driver's fatigue can be reduced.

  On the other hand, when the time measurement timer 1TR1 is equal to or greater than the time measurement timer 1 time-up TR10 (TR1 ≧ TR10, step S102: YES), the microcomputer 29 resets the processing number counter CTR (CTR = “0”, step S113). Subsequently, the steering torque integrated value Τsum is reset (Τsum = “0”, step S114), and the time measurement timer 1TR1 is further reset (TR1 = “0”, step S115). Then, the microcomputer 29 sets the q-axis current command value Iq ** before correction to the q-axis current command value Iq *, and outputs it to the motor control signal generation unit 44 (step S104), and the process is completed.

  Subsequently, when the rough road determination flag FLG1 is set (FLG1 = “1”, Step S100, YES), the microcomputer 29 increments the time measurement timer 2TR2 (TR2 = TR2 + 1, Step S116). Then, the microcomputer 29 determines whether or not the time measurement timer 2TR2 is equal to or greater than the time measurement timer 2 time-up TR20 (step S117).

  Then, when the time measurement timer 2TR2 is smaller than the time measurement timer 2 time-up TR20 (TR2 <TR20, step S117: NO), the microcomputer 29 continues the microcomputer 29 so that the vehicle speed V is equal to or higher than the predetermined vehicle speed V0. Is determined (step S118). When the vehicle speed V is smaller than the predetermined vehicle speed V0 (V <V0, step S118: NO), the microcomputer 29 adds the Iq ** corrected current value Iq0 to the q-axis current command value Iq ** before correction. The value is output to the motor control signal generation unit 44 as the q-axis current command value Iq * (step S112), and the process ends.

  Next, when the vehicle speed V is equal to or higher than the predetermined vehicle speed V0 (V ≧ V0, step S118: YES), the microcomputer 29 continues to check whether the absolute value of the motor rotational angular acceleration αm is equal to or higher than the predetermined motor rotational angular acceleration αm0. It is determined whether or not (step S119). When the absolute value of the motor rotational angular acceleration αm is smaller than the predetermined motor rotational angular acceleration αm0 (| αm | <αm0, step S119: NO), the microcomputer 29 determines the q-axis current command value Iq ** before correction. Is added to the motor control signal generator 44 as a q-axis current command value Iq * (step S112), and the process ends.

  On the other hand, when the absolute value of the motor rotation angular acceleration αm is equal to or greater than the predetermined motor rotation angular acceleration αm0 (| αm | ≧ αm0, step S119: YES), the microcomputer 29 resets the time measurement timer 2TR2 (TR2 = “ 0 ", step S120). As a result, the time measurement timer 2TR2 does not time up, so that the state where the assist force is increased can be continued. The microcomputer 29 outputs a value obtained by adding the Iq ** corrected current value Iq0 to the uncorrected q-axis current command value Iq ** to the motor control signal generation unit 44 as the q-axis current command value Iq * (step S112). Then, the process ends.

  Further, when the time measurement timer 2TR2 is equal to or greater than the time measurement timer 2 time-up TR20 (TR2 ≧ TR20, step S117: YES), the microcomputer 29 continues to reset the rough road determination flag FLG1. (FLG1 = "0", step S121). Then, the microcomputer 29 sets the q-axis current command value Iq ** before correction to the q-axis current command value Iq *, and outputs it to the motor control signal generation unit 44 (step S104), and the process is completed.

Next, the operation and effect of the EPS 1 of the present embodiment configured as described above will be described.
That is, the number of times that the vehicle speed is equal to or higher than the predetermined vehicle speed within the predetermined time and the absolute value of the motor rotational angular acceleration is equal to or larger than the predetermined motor rotational angular acceleration is equal to or greater than the predetermined number of times and When the added value of the absolute value of the steering torque becomes a predetermined value or more within the time, the assist force is increased. With such a configuration, it is possible to grasp a state in which the driver suddenly turns the steering to the left and right on a rough road. Then, by detecting that the above operation has continued for a predetermined number of times within a predetermined time and that the integrated value of the absolute value of the steering torque is equal to or greater than the predetermined value, it is precisely that the driver feels a great sense of fatigue. Can be estimated. In this state, the assist force is increased to reduce the driver's fatigue.

  As a result, since it is possible to determine a bad road with high accuracy, the steering feeling can be improved by generating an appropriate assist force.

In addition, you may change this embodiment as follows.
-In this embodiment, when the driver's fatigue level on a rough road is obtained by integrating the steering torque integrated value with the absolute value of the steering torque, and the steering torque integrated value is greater than or equal to the predetermined steering torque integrated value In addition, the assist power was increased. However, the degree of fatigue of the driver traveling on a rough road may be obtained not by the integrated value of the steering torque but by the integrated value of the actual current of the motor.

-In this embodiment, although the value which increases assist force at the time of rough road driving | running was made into the fixed value, the value to increase may be gradually increased for every control period. Further, when the vehicle returns from the rough road traveling to the normal traveling, the increased assist force may be gradually decreased.

In the present embodiment, the present invention is embodied in the column assist EPS, but the present invention may be applied to a rack assist EPS or a pinion assist EPS.

1: Electric power steering device (EPS), 2: Steering,
3: Steering shaft, 4: Rack and pinion mechanism, 5: Rack shaft,
8: column shaft, 9: intermediate shaft, 10: pinion shaft, 11: tie rod, 12: steered wheel, 21: motor,
22: Motor rotation angle sensor (motor rotation angle detection means), 23: Deceleration mechanism,
24: EPS actuator (steering force assist device),
25: vehicle speed sensor (vehicle speed detection means), 26: torque sensor (steering torque detection means), 27: ECU, 28: battery, 29: microcomputer (control means),
30u, 30v, 30w: current sensor,
31: Iq * current command value calculation unit (assist force generation means),
32: Iq ** calculation unit, 33: Iq ** correction calculation unit, 34: d / q conversion calculation unit,
35: q-axis PID control unit, 36: d-axis PID control unit, 37: d / q inverse transformation calculation unit,
38: PWM output unit, 40: drive circuit, 44: motor control signal generation unit,
50: Adder, 53, 54: Subtractor,
V: vehicle speed, τ: steering torque, θm: motor rotation angle,
Iu, Iv, Iw: current value of each phase,
Iq *: q-axis current command value, Iq **: q-axis current command value before correction,
Iq0: Iq ** correction current value,
Iq: q-axis current value, ΔIq: q-axis deviation current value,
Id *: d-axis current command value, Id: d-axis current value, ΔId: d-axis deviation current value,
Vq *: q-axis voltage command value, Vd *: d-axis voltage command value,
Vu *, Vv *, Vw *: Voltage command values for each phase,
V0: predetermined vehicle speed,
αm: motor rotation angular acceleration, αm0: predetermined motor rotation angular acceleration,
TR1: Time measurement timer 1, TR10: Time measurement timer 1 time up,
TR2: Time measurement timer 2, TR20: Time measurement timer 2 time up,
CTR: Process count counter, CTR0: Process count counter count up,
Τsum: Steering torque integrated value, Τsum0: Predetermined steering torque integrated value,
FLG1: Bad road judgment flag

Claims (2)

A steering force assisting device provided to apply an assisting force to assist the steering operation to the steering system by the motor;
Steering torque detection means for detecting steering torque;
Vehicle speed detection means for detecting the vehicle speed;
Motor rotation angle detection means for detecting the motor rotation angle;
Motor rotation angular acceleration calculation means for calculating motor rotation angular acceleration from the motor rotation angle detected from the motor rotation angle detection means;
An assist force generating means for generating an assist force from the steering torque detected from the steering torque detecting means and the vehicle speed detected from the vehicle speed detecting means;
An electric power steering apparatus comprising: control means for controlling the operation of the steering force assisting device by supplying driving power to a motor that is a drive source of the steering force assisting device based on the assist force generating device. In
The control means is configured such that the number of times that the vehicle speed is equal to or higher than a predetermined vehicle speed within a predetermined time and the absolute value of the motor rotation angular acceleration is equal to or higher than a predetermined motor rotation angular acceleration is equal to or higher than a predetermined number , If the integrated value of the absolute value of the steering torque is equal to or greater than a predetermined value within the predetermined time, increasing the assist force;
An electric power steering device. The control means, after increasing the assist force, when the vehicle speed does not satisfy the condition that the vehicle speed is equal to or higher than the predetermined vehicle speed and the absolute value of the motor rotation angular acceleration is equal to or higher than the predetermined motor rotation angular acceleration within a predetermined time To return to the normal assist force without increasing the assist force,
The electric power steering apparatus according to claim 1.

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