JP7124449B2 - Hands-on-off detection device, electric power steering device, external torque estimation method, and hands-on-off detection device control program - Google Patents

Description

The present invention provides a hands-on/off detection device to be installed in an electric power steering device that drives and controls a motor according to a current command value and assists and controls a steering system of a vehicle by drive control of the motor, and an electric power steering equipped with the hands-on/off detection device. The present invention relates to a device, an external torque estimation method and a hands-on-off detection device control program.

2. Description of the Related Art In an electric power steering system (EPS) that assists and controls a steering system of a vehicle with the rotational force of a motor, the driving force of the motor is applied to a steering shaft or a rack shaft as a steering assist force (assist force).

Advanced Driver Assistance System (ADAS) is a system that assists the driving operation of an automobile driver. It is intended to prevent or mitigate In ADAS, "hands-on/hands-off detection" is used to determine whether the driver is gripping the steering wheel (hands-on state) or the driver is not gripping the steering wheel (hands-off state). there is In recent years, it has become more and more important to improve detection accuracy in hands-on/hands-off detection.

The steering wheel operation state determination device described in Patent Document 1 performs hands-on/hands-off detection by estimating driver torque generated by steering by the driver. The driver torque is estimated by a torque estimation observer that inputs the rotation angle detected by the rotation angle sensor installed on the EPS motor and the steering torque (torsion bar torque) detected by the torque sensor installed on the steering shaft. be done.

JP 2017-114324 A

By the way, since the steering shaft transmits the rotation of the steering wheel to the steered wheels, not only the driver torque but also the road surface reaction torque generated by the reaction force received by the steered wheels from the road surface acts on the steering shaft.
However, the steering wheel operation state determination device described in Patent Document 1 estimates the driver torque directly from the steering torque (torsion bar torque) using a torque estimation observer. Therefore, it is difficult to determine whether the estimated driver torque is the true driver torque generated by the driver's steering or the road surface reaction torque generated by factors such as the road surface reaction force. rice field.

In view of the above circumstances, the present invention provides a hands-on/off detection device capable of robust hands-on/hands-off detection against road surface reaction torque, etc., an electric power steering device equipped with the same hands-on/off detection device, and an external torque estimation method. and a hands-on-off detection device control program.

In order to solve the above problems, the present invention proposes the following means.
The hands-on-off detection device of the present invention comprises an input shaft to which a handle is connected, a torque sensor attached to an output shaft connected to the input shaft, and a torque sensor connected to the output shaft for detecting a rotor rotation angle. an electric motor connected to a sensor and a current sensor for detecting a motor current value; and a controller connected to the torque sensor and the electric motor, wherein the controller detects steering torque from the torque sensor. the control unit acquires the rotor rotation angle and the motor current value from the electric motor; the control unit calculates motor torque by multiplying the motor current value by a torque constant; , from the steering torque, the rotor rotation angle, and the motor torque, a disturbance torque, which is a torque other than the motor torque among the torques acting on the input shaft and the output shaft, is estimated; Low-pass filter processing is performed on the disturbance torque and the steering torque, phase comparison is performed between the disturbance torque after the low-pass filter processing and the steering torque, and it is determined that the disturbance torque and the steering torque are in the same phase. If so, it is determined that the disturbance torque is the torque input from the input shaft side, and if it is determined that the disturbance torque and the steering torque are in opposite phase, the disturbance torque is input from the output shaft side It is determined that it is the input torque.

In the hands-on-off detection device of the present invention, the control unit has a counter, and when it is determined that the disturbance torque is the torque input from the input shaft side, the counter value of the counter is increased by a predetermined addition value. If the condition for adding the counter value is not satisfied, the counter value is subtracted by a predetermined subtraction value, and if the counter value exceeds a predetermined hands-on determination threshold value, the driver grips the steering wheel. If the counter value is less than a predetermined hands-off determination threshold, it may be determined that the driver is not gripping the steering wheel.

In the hands-on-off detection device of the present invention, when the control unit determines that the disturbance torque is the torque input from the input shaft side, and the disturbance torque after the low-pass filter processing is a predetermined torque threshold If greater, the counter value may be incremented by a predetermined additional value.

In the hands-on-off detection device of the present invention, when the control unit determines that the disturbance torque is the torque input from the input shaft during a period in which a predetermined operation flag is activated, and A predetermined addition value may be added to the counter value when the disturbance torque subjected to band-pass filtering after low-pass filtering is greater than a predetermined torque threshold.

The hands-on-off detection device of the present invention may convert the motor torque into a corrected motor torque that considers the operating error of the electric motor.

In the hands-on-off detection device of the present invention, the added value may be greater than the subtracted value.

An electric power steering system according to the present invention is equipped with the hands-on-off detection device described above.

The external torque estimation method of the present invention includes a steering torque detection step of detecting a steering torque from an input shaft to which a steering wheel is connected and an output shaft connected to the input shaft, and an electric motor connected to the output shaft. A rotor rotation angle detection step of detecting a rotor rotation angle, a motor current value detection step of detecting a motor current value from the electric motor, and a motor torque calculation step of calculating a motor torque by multiplying the motor current value by a torque constant. a corrected motor torque calculation step of calculating a corrected motor torque from the motor torque and a deformation characteristic of a reduction mechanism coupled to the electric motor; the steering torque, the rotor rotation angle, the motor torque, and the corrected motor; and an external torque estimating step of estimating a disturbance torque, which is torque other than the motor torque among torques acting on the input shaft and the output shaft, from the torque.

The hands-on-off detection device control program of the present invention comprises an input shaft to which a handle is connected, a torque sensor attached to an output shaft connected to the input shaft, and a torque sensor connected to the output shaft to detect a rotor rotation angle. A hands-on/off detection device comprising: an electric motor connected to an angle sensor that detects a current value of the motor; and a controller connected to the torque sensor and the electric motor, wherein the controller includes the The steering torque is obtained from a torque sensor, the controller obtains the rotor rotation angle and the motor current value from the electric motor, and the controller calculates the motor torque by multiplying the motor current value by a torque constant. and causing the control unit to estimate disturbance torque, which is torque other than the motor torque among the torques acting on the input shaft and the output shaft, from the steering torque, the rotor rotation angle, and the motor torque. and causing the control unit to perform low-pass filter processing on the disturbance torque and the steering torque, perform phase comparison between the disturbance torque after the low-pass filter processing and the steering torque, and perform a phase comparison between the disturbance torque and the steering torque. is in the same phase, the disturbance torque is determined to be the torque input from the input shaft side, and when it is determined that the disturbance torque and the steering torque are in opposite phase, the disturbance torque is the torque input from the output shaft side.

According to the hands-on/off detection device, the electric power steering device equipped with the hands-on-off detection device, the external torque estimation method, and the hands-on-off detection device control program of the present invention, robust hands-on/hands-off detection against road surface reaction torque, etc. It can be performed.

1 is a schematic diagram showing the configuration of an electric power steering device according to a first embodiment of the present invention; FIG. 2 is a configuration diagram of a steering shaft of the same electric power steering device; FIG. 2 is a block diagram showing the configuration of an ECU of the electric power steering device; FIG. It is a block diagram which shows the structure of the control part of same EUC. FIG. 3 is a functional block diagram when the same ECU assists the steering of the driver; FIG. 3 is a functional block diagram when the same ECU performs hands-on/hands-off detection; It is a graph for obtaining a corrected motor torque in consideration of an operation error from a motor current value. FIG. 2 is a state variable diagram of the electric power steering system according to the first embodiment of the present invention; FIG. 4 is a state variable diagram of an observer; These are measurement results of steering torque, steering torque estimation value, and disturbance torque estimation value. This is the measurement result when the disturbance torque simulating the road surface reaction force is input from the output shaft side in the hands-off state. It is the measurement result of the disturbance torque estimated value and the steering torque estimated value in the hands-off state. It is a measurement result of the disturbance torque estimated value and the steering torque estimated value in the hands-on state. 4 is a graph showing the operation of a hands-on-off counter; FIG. 10 is a functional block diagram when the ECU of the electric power steering device according to the second embodiment of the present invention performs hands-on/hands-off detection; It is a Bode diagram of a bandpass filter of the same electric power steering apparatus. It is a graph which shows the effect of the LDW band pass filter of the same electric power steering apparatus.

(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS. 1 to 14. FIG.
FIG. 1 is a schematic diagram showing the configuration of an electric power steering device 100 equipped with a hands-on/off detection device 200 according to this embodiment. The electric power steering device 100 is a column assist type electric power steering device in which an electric motor and a speed reduction mechanism are arranged on a column portion (steering shaft).

As shown in FIG. 1, the electric power steering apparatus 100 includes a steering wheel 1 which is a steering member for steering a vehicle, a steering mechanism 2 which steers steered wheels in conjunction with the rotation of the steering wheel 1, and a steering assist mechanism 3 that assists the steering of the driver.

The steering mechanism 2 includes a steering shaft (column shaft, steering wheel shaft) 20 connected to the steering wheel 1, a steering angle sensor 20a for detecting the steering angle θ _IS of the steering wheel 1, a universal joint 24, an intermediate shaft 25, It has a pinion rack mechanism 26, tie rods 27a and 27b, and hub units 28a and 28b.
The steering shaft 20 is connected to the steered wheels via a universal joint 24, an intermediate shaft 25, a pinion rack mechanism 26, tie rods 27a and 27b, and via hub units 28a and 28b.
A torque sensor 29 is provided on the steering shaft 20 . A torque sensor 29 is used to calculate a steering torque (steering torque) Ts.

The steering assist mechanism 3 includes an electric motor 30, a speed reduction mechanism 31, a vehicle speed sensor 32 for detecting vehicle speed, and an ECU (control unit) 33, as shown in FIG.

FIG. 2 is a configuration diagram of the steering shaft 20. As shown in FIG.
The steering shaft 20 has an input shaft 21 connected to the steering wheel 1, an output shaft 22 connected to a universal joint 24, and a torsion bar 23 connecting the input shaft 21 and the output shaft 22. The input shaft 21 and the output shaft 22 are connected via a torsion bar 23 so as to be relatively rotatable on the same axis.
The input shaft 21 and the output shaft 22 may be connected (integrated) without using the torsion bar 23 for the steering shaft 20 .

The torque sensor 29 is attached to the input shaft 21 and the output shaft 22, as shown in FIG. The torque sensor 29, for example, electrically detects a phase rotation displacement amount of the input shaft 21 with respect to the output shaft 22 (detects an increase or decrease in magnetic flux density), and calculates a steering torque Ts from the phase rotation displacement amount (steering torque detection process). The torque sensor 29 detects the number of rotation pulses, and may detect the steering torque Ts from the difference in the number of rotation pulses detected from the input shaft 21 and the output shaft 22 . Moreover, the torque sensor 29 may detect the steering torque Ts by a strain gauge or an optical sensor. Torque sensor 29 outputs the detected steering torque Ts to ECU 33 .
If the torque sensor 29 can detect the angle of the input shaft 21 (the steering angle of the steering wheel 1) θ _IS , the steering angle sensor 20a is not necessarily required.

The torque sensor 29 may detect the rotation angles of the input shaft 21 and the output shaft 22, output the detected rotation angles to the EUC 33, and the ECU 33 may calculate the steering torque Ts based on the rotation angles.

The pinion rack mechanism 26 has a pinion and rack (not shown).
The pinion is connected to the intermediate shaft 25 and rotates as the intermediate shaft 25 rotates.
The rack extends linearly along the left-right direction of the automobile (direction orthogonal to the straight-ahead direction). The rack meshes with the pinion near the axial middle portion of the rack. The pinion and rack convert rotation of the pinion into axial movement of the rack. Axial movement of the rack steers the steerable wheels.

When the steering wheel 1 is steered (rotated) by the driver, the rotation of the steering wheel 1 is transmitted to the pinion via the steering shaft 20 and the intermediate shaft 25 . Rotation of the pinion is then converted into axial movement of the rack. Tie rods 27a, 27b and hub units 28a, 28b connected to both ends of pinion rack mechanism 26 move in the axial direction of the rack, and steerable wheels connected to hub units 28a, 28b are steered.

The electric motor 30 is, for example, a three-phase brushless motor that assists the steering force of the steering wheel 1 . The electric motor 30 is connected to the output shaft 22 via a speed reduction mechanism 31 . A rotation angle sensor such as a resolver or a TMR sensor is connected to the electric motor 30, and the rotation angle sensor (rotor rotation angle) θ _OS of the rotor of the electric motor 30 is detected (rotor rotation angle detection step). ). The rotation angle sensor outputs the detected rotor rotation angle θ _OS to the ECU 33 . A current sensor is connected to the electric motor 30, and the motor current value Im flowing through the electric motor 30 is measured by the current sensor. The current sensor outputs the measured motor current value Im to the EUC 33 (motor current value detection step).

The reduction mechanism 31 is a worm gear mechanism having a worm gear 31a and a worm wheel 31b that meshes with the worm gear 31a. The worm gear 31 a is rotationally driven by the electric motor 30 . Also, the worm wheel 31b is connected to the output shaft 22 so as to be able to rotate integrally therewith. The worm wheel 31b is rotationally driven by the worm gear 31a.

The vehicle speed sensor 32 is a sensor that detects vehicle speed Vel. The vehicle speed sensor 32 outputs the detected vehicle speed Vel to the ECU 33 .

FIG. 3 is a block diagram showing the configuration of the ECU 33. As shown in FIG.
The ECU (control unit) 33 has, as shown in FIG.

FIG. 4 is a block diagram showing the configuration of the control section 34. As shown in FIG.
The control unit 34 is a device (computer) capable of executing a program including a CPU (Central Processing Unit) 36, a memory 37, a storage unit 38, and an input/output control unit 39, as shown in FIG. By executing a predetermined program, it functions as a plurality of functional blocks such as a current command value calculator 41, which will be described later. At least part of the functions of the control unit 34 may be configured by a dedicated logic circuit or the like.

The storage unit 38 is a non-volatile recording medium that stores the above-described programs and necessary data. The storage unit 38 is composed of, for example, a ROM, a hard disk, or the like. A program recorded in the storage unit 38 is read into the memory 37 and executed by the CPU 36 .

The input/output control unit 39 receives input data from the vehicle speed sensor 32, the rotation angle sensor of the electric motor 30, and the like. The input/output control unit 39 also generates control signals and the like for the vehicle speed sensor 32 and the electric motor 30 based on instructions from the CPU 36 when the CPU 36 controls the vehicle speed sensor 32 and the electric motor 30 .

The motor drive circuit 35 is an inverter that PWM-drives the electric motor 30 . The motor drive circuit 35 uses, for example, FETs (Field Effect Transistors) as drive elements, and is composed of an FET bridge circuit.

The ECU 33 calculates the current command value of the assist (steering assistance) command based on the steering torque Ts detected by the torque sensor 29 and the vehicle speed Vel detected by the vehicle speed sensor 32, and compensates the current command value. The current supplied to the electric motor 30 is controlled by the voltage control command value Vref obtained by applying the

FIG. 5 is a functional block diagram of the ECU 33 when the ECU 33 assists the steering of the driver.
The steering torque Ts detected by the torque sensor 29 and the vehicle speed Vel detected by the vehicle speed sensor 32 are input to a current command value calculator 41 that calculates a current command value Iref1. The current command value calculation unit 41 calculates a current command value Iref1, which is a control target value of the current supplied to the electric motor 30, using an assist map or the like based on the input steering torque Ts and vehicle speed Vel.

The current command value Iref1 is input to the current limiter 43 via the adder 42A, the current command value Irefm whose maximum current is limited is input to the subtractor 42B, and the deviation I (Irefm -Im) is calculated. The deviation I is input to a PI (proportional-integral) control section 45 in order to improve steering operation characteristics.

A voltage control value Vref PI-controlled by the PI control unit 45 is input to the PWM control unit 46 together with the modulation signal (carrier) CF. The PWM control unit 46 calculates the duty and PWM-drives the electric motor 30 via the motor drive circuit 35 according to the PWM signal.

The motor current value is detected by the motor current detection means, input to the subtractor 42B, and fed back. In the case of a three-phase brushless motor, the PWM control unit 46 includes a duty calculation unit that calculates a PWM duty value D for three phases according to a predetermined formula for voltage control values, and a PWM duty value D that controls the gate of an FET as a drive element. It is composed of a gate driving section that drives and turns ON/OFF after compensating for dead time. The motor drive circuit 35 is composed of, for example, a three-phase bridge composed of upper and lower arms composed of a U-phase upper FET and a lower FET. driven.

The compensation signal CM from the compensation signal generator 44 is added to the adder 42A, and the characteristics of the steering system are compensated by the addition of the compensation signal CM to improve convergence and inertia characteristics. . Compensation signal generation unit 44 adds self-aligning torque (SAT) 443 and inertia 442 in addition unit 444, adds convergence 441 to the addition result in addition unit 445, and outputs the addition result of addition unit 445 as a compensation signal. It is commercial.

When the driver steers the steering wheel 1 , the input shaft 21 rotates and the torsion bar 23 twists, causing phase rotation displacement between the input shaft 21 and the output shaft 22 . The torque sensor 29 detects the steering torque Ts from the phase rotation displacement amount (θ _IS −θ _OS ) of the input shaft 21 with respect to the output shaft 22 . Based on the steering torque Ts and the vehicle speed Vel detected by the vehicle speed sensor 32, the ECU 23 controls driving of the electric motor 30 so that the steering torque Ts is reduced. As a result, the worm gear 31a is rotationally driven by the electric motor 30 controlled by the ECU 33. As shown in FIG. As a result, the worm wheel 31b is rotationally driven, motor torque is applied to the output shaft 22, and the output shaft 22 rotates. Rotation of the output shaft 22 is transmitted to the pinion rack mechanism 26 via the intermediate shaft 25 . Further, the rotation of the pinion of the pinion rack mechanism 26 is converted into axial movement of the rack to steer the steerable wheels. Thus, the electric motor 30 can assist the driver's steering by rotationally driving the worm gear 31a.

Next, hands-on/hands-off detection by the electric power steering apparatus 100 will be described in detail. Hands-on/hands-off detection is performed by a hands-on/off detection device 200 configured by a torque sensor 29, an electric motor 30, and an ECU 23. FIG.

FIG. 6 is a functional block diagram of the ECU 33 when the ECU 33 detects hands-on/hands-off. Functional blocks used when the ECU 33 performs hands-on/hands-off detection include a motor torque calculator 50, a steering state observer 51, a low-pass filter 52, a low-pass filter 53, a phase comparator 54, and a first threshold value comparator 55. , and a determination unit 56 .

The motor torque calculation unit 50, the steering state observer 51, the low-pass filter 52, the low-pass filter 53, the phase comparison unit 54, the first threshold value comparison unit 55, and the determination unit 56 are controlled by the control unit 34 of the ECU 33 executing a predetermined program. It is a functional block to be implemented.

<Motor torque calculator>
A motor current value Im detected by the current sensor of the electric motor 30 is acquired and input to the motor torque calculation unit 50 . The motor torque calculator 50 outputs the motor torque Tm calculated by multiplying the motor current value Im by the torque constant of the electric motor 30 to the steering state observer 51 .

<Steering state observer>
The steering torque Ts detected by the torque sensor 29 , the rotor rotation angle θ _OS detected by the rotation angle sensor of the electric motor 30 , and the motor torque Tm are acquired and input to the steering state observer 51 . A steering state observer (observer) 51 estimates a disturbance torque Tdis, which is a torque acting on the output shaft 22 other than the motor torque Tm, based on the steering torque Ts, the rotor rotation angle θ _OS , and the motor torque Tm. (external torque estimation step).

Based on the steering mechanism of the electric power steering device 100, a vector having as elements an input shaft angle θ _IS that is the angle of the input shaft 21 and an input shaft angular velocity θ _IS (dotted θ _IS ) is defined as a state variable vector x. , rotor rotation angle θ _OS , driver torque Td, and motor torque Tm as elements. Here, Kt is the spring constant of the torsion bar 23, and Js is the handle inertia of the steering system.

The steering torque Ts is obtained by adding the motor torque Tm of the electric motor 30 to the torque obtained by multiplying the phase rotation displacement amount (θ _IS - θ _OS ) of the input shaft 21 with respect to the output shaft 22 by the spring constant Kt. A steering torque estimated value ^Ts, which is an estimated value of Ts, can be expressed as shown in Equation 2 using a state variable vector x and an input variable vector u.

Here, F(Tm) in Equation 2 is a function for obtaining a corrected motor torque that takes into account operating errors such as deformation of the worm gear that change with the motor torque Tm. The graph shown in FIG. 7 is an example of F(Tm). The horizontal axis of FIG. 7 is the motor current value Im (the value obtained by dividing the motor torque Tm by the torque constant), and the vertical axis is the corresponding corrected motor torque. In the example of F(Tm) shown in FIG. 7, it is possible to output a corrected motor torque in consideration of the backlash that occurs when the motor current value is near zero.

FIG. 8 is a state variable diagram based on Equations 1 and 2. FIG. FIG. 9 is a state variable diagram of an observer that estimates a state variable vector x (input shaft angle θ _IS and input shaft angular velocity·θ _IS ) using steering torque Ts. L is the observer gain. The state equation of the observer shown in FIG. 9 is expressed as Equation 3.

Next, the observer gain L of the observer shown in FIG. 9 and Equation 3 is obtained. Since the driver torque Td, which is one of the input variable vectors u of the observer, is an unknown value, the observer gain L is obtained with the driver torque Td set to zero. Equation 4 is an observer state equation with the driver torque Td set to zero. Formula 5 is a formula (formula 2) for calculating the steering torque estimated value ^Ts with the driver torque Td set to zero.

When the driver does not grip the steering wheel (hands-off state), the observer is provided so that the electric motor 30 can be arbitrarily operated and the state variable vector x (input shaft angle θ _IS and input shaft angular velocity θ _IS ) can be estimated. Adjust the gain L.
The observer gain L is adjusted so that the estimation error between the actual input shaft angle θ _IS and the input shaft angle θ _IS estimated by the observer can be made zero.

After adjusting the observer gain L, the steering torque estimated value ̂Ts can be obtained from the state variable vector x estimated by the observer according to Equation (5).

After the observer gain L is adjusted, the estimated steering torque ^Ts substantially matches the steering torque Ts in a state where no torque other than the motor torque from the electric motor 30 acts on the input shaft 21 and the output shaft 22 . Here, the steering torque estimated value ^Ts does not need to match the steering torque Ts completely, and may have an error such as an offset error.

Here, disturbances such as friction with bearings and vibrations transmitted from the vehicle body act on the input shaft 21 and the output shaft 22 attached to the vehicle body. It is desirable to set the offset error in consideration of such disturbance.

Next, a state in which a torque (disturbance torque Tdis) other than the motor torque of the electric motor 30 acts on the input shaft 21 and the output shaft 22 will be examined. When the disturbance torque Tdis acts on the input shaft 21 and the output shaft 22, the steering torque Ts detected by the torque sensor 29 and the steering torque estimated value ^Ts estimated by the steering state observer 51 are different due to the disturbance torque Tdis. there is a difference. Therefore, as shown in Equation 5, the difference (Ts−̂Ts) between the steering torque Ts and the estimated steering torque ^Ts is multiplied by a predetermined coefficient to obtain the estimated disturbance torque ^Tdis (Tdis with a hat). ).

In Equation 6, M is the disturbance torque gain. The disturbance torque gain M is set to a value that is as large as possible within the range that satisfies Equation 7 and does not overemphasize the noise component of the disturbance torque estimated value ^Tdis. Here, when the disturbance torque gain M satisfies Expression 6, the response of the disturbance torque gain M is slower than that of the observer gain L.

Further, the disturbance torque estimated value ̂Tdis is fed back to the steering state observer 51 as the driver torque estimated value ̂Td, which is one of the input variable vectors u, as shown in Equation (6). By feeding back the estimated driver torque ̂Td to the steering state observer 51 as the driver torque Td, the operation of the steering state observer 51 is corrected so as to take the driver torque Td into consideration.

<Low pass filter>
A disturbance torque estimation value ^Tdis estimated by the steering state observer 51 is input to the low-pass filter 52 . A low-pass filter 52 attenuates frequency components higher than a predetermined cutoff frequency from the disturbance torque estimated value Tdis. In this embodiment, the cutoff frequency is set to approximately 15 Hz. The low-pass filter 52 can attenuate high-frequency noise components included in the disturbance torque estimation value ^Tdis to improve the accuracy of hands-on/hands-off detection.

The steering torque Ts detected by the torque sensor 29 and input to the steering state observer 51 is separately input to the low-pass filter 53 . The configuration of the low-pass filter 53 is the same as that of the low-pass filter 52 . The low-pass filter 53 attenuates frequency components higher than a predetermined cutoff frequency from the steering torque Ts. In this embodiment, the cutoff frequency is set to approximately 15 Hz. By setting the cutoff frequency of the lowpass filter 52 and the cutoff frequency of the lowpass filter 53 to be the same, it is easy to compare the signals output from both lowpass filters.

<Phase comparator>
The disturbance torque estimated value ^Tdis that has passed through the low-pass filter 52 and the steering torque Ts that has passed through the low-pass filter 53 are input to the phase comparator 54 .
When the disturbance torque is an input from the steering wheel side (input shaft side), that is, the driver torque, the disturbance torque estimated value ̂Tdis and the steering torque Ts have the same phase. The simplest phase comparison is a method of determining by the signs of the disturbance torque estimated value ̂Tdis and the steering torque Ts, as in Equation (8). The cross-correlation or phase relationship of the two signals may be calculated to more accurately determine whether they are in phase.
Since the steering torque Ts is calculated from the phase rotation displacement amount (θ _IS - θ _OS ), the disturbance acting on the input shaft side has the same phase as the steering torque Ts.

On the other hand, when the disturbance torque is the input from the pinion side (output shaft side), that is, the road surface reaction torque, the disturbance torque estimated value ^Tdis and the steering torque Ts are in opposite phases. The simplest phase comparison is a method of determining by the signs of the disturbance torque estimated value ̂Tdis and the steering torque Ts, as in Equation (9). A cross-correlation or phase relationship between the two signals may be calculated to more accurately determine whether they are in antiphase.
Since the steering torque Ts is calculated from the phase rotation displacement amount (θ _IS - θ _OS ), the disturbance acting on the output shaft side has an opposite phase to the steering torque Ts.

FIG. 10 shows measurement results of the steering torque Ts, the steering torque estimated value ̂Ts, and the disturbance torque estimated value ̂Tdis in the electric power steering device 100. FIG. Actual Angle in FIG. 10 indicates the actual rotation angle [deg] of the steering wheel 1 .
As shown in FIG. 10, when the driver is steering the steering wheel (hands-on state), the disturbance torque estimation value ^Tdis and the steering torque Ts are in phase, but the driver has released the steering wheel. In the (hands-off state), the estimated disturbance torque ^Tdis and the steering torque Ts are in opposite phases.

FIG. 11 shows the measurement results when the road reaction force torque simulating the road reaction force is input from the pinion side (output shaft side) when the driver releases the steering wheel (hands-off state). The disturbance torque estimated value ̂Tdis and the steering torque estimated value ̂Ts are in opposite phases. In this way, by confirming the phase relationship between the disturbance torque estimated value ^Tdis and the steering torque Ts, it is possible to determine whether the disturbance torque is the driver torque input from the input shaft side generated by the driver's steering or the road surface. It can be determined whether the road surface reaction torque is input from the output shaft side and is generated due to a reaction force or the like. This enables robust hands-on/hands-off detection even when road surface reaction torque is generated.

The phase comparator 54 outputs a result flag indicating whether the estimated disturbance torque Tdis and the steering torque Ts are in the same phase or in the opposite phase.

<First threshold comparison unit>
The disturbance torque estimated value ̂Tdis that has passed through the low-pass filter 52 and the steering torque Ts that has passed through the low-pass filter 53 are also input to the first threshold comparator 55 .
The first threshold comparison unit 55 determines whether the absolute value of the estimated disturbance torque ^Tdis and the absolute value of the steering torque Ts are greater than a torque threshold (for example, 0.1 [Nm]), as shown in equations 10 and 11. discriminate.

FIG. 12 shows the estimated disturbance torque ^Tdis and the estimated steering torque ^Ts when the electric motor 30 is repeatedly automatically steered from +90 deg to -90 deg/sec while the driver does not touch the steering wheel (hands-off state). ing. Target Angle is the target angle, and Actual Angle is the steering angle θ _IS of the steering wheel 1 detected by the steering angle sensor 20a. In the automatic steering, the electric motor 30 is controlled so that the steering angle θ _IS follows the target angle.
As shown in FIG. 12, both the absolute value of the estimated disturbance torque ^Tdis and the absolute value of the steering torque Ts are small.

FIG. 13 shows the estimated disturbance torque ^Tdis and the estimated steering torque ^Ts when the electric motor 30 is automatically steered repeatedly from -90 deg/sec to +90 deg/sec while the driver is in contact with the steering wheel (hands-on state). ing. Both the absolute value of the estimated disturbance torque ^Tdis and the absolute value of the steering torque Ts are large. That is, the absolute values of the estimated disturbance torque value ̂Tdis and the estimated steering torque value ̂Ts are larger in the hands-on state than in the hands-off state. This torque difference can be used to assist hands-on/hands-off detection and improve the reliability of hands-on/hands-off detection.

The first threshold comparison unit 55 outputs a result flag indicating whether or not the estimated disturbance torque value ^Tdis and the estimated steering torque value ^Ts exceed the torque threshold value.

It is optional whether only the estimated disturbance torque value ^Tdis is compared with the torque threshold value or both the estimated disturbance torque value ^Tdis and the estimated steering torque value ^Ts are compared with the torque threshold value.

<Determination part>
The determination unit 56 makes a final determination in hands-on/hands-off detection. In order to reduce the influence of noise of the torque sensor 29 and the motor angle sensor and improve the reliability of detection, a counter (referred to as a "hands-on-off counter") is used for determination. The determination unit 56 receives the result flag of the phase comparison by the phase comparison unit 54 and the result flag of the threshold value comparison by the first threshold value comparison unit 55 .

A hands-on/off counter used for hands-on/hands-off detection is a counter that operates from zero to a predetermined maximum value. Even if the hands-on-off counter is decremented when the counter value is zero, the counter value is clipped and remains zero. Moreover, even if the hands-on-off counter is incremented when the counter value reaches the predetermined maximum value, the counter value is clipped and remains at the predetermined maximum value.

The closer the hands-on-off counter is to a predetermined maximum, the more likely it is to be "hands-on." On the other hand, the closer the hands-on-off counter is to zero, the more likely it is to be in a "hands-off state."

FIG. 14 is a graph showing the operation of the hands-on-off counter.
The hands-on-off counter is set to a predetermined value when (i) the estimated disturbance torque ^Tdis and the steering torque Ts are in phase, and (ii) the absolute value of the estimated disturbance torque ^Tdis exceeds the torque threshold. is incremented (added) by the increment amount of This processing is performed at predetermined intervals. If the above conditions (i) and (ii) are not satisfied when the result flag is checked at a predetermined cycle, the hands-on-off counter is decremented (subtracted) by a predetermined decrement amount.
That is, the hands-on-off counter is either incremented or decremented at predetermined intervals.

The counter value of the hands-on-off counter is compared with a hands-on determination threshold value and a hands-off determination threshold value set within a range from zero to a predetermined maximum value.
(a) If the counter value is equal to or greater than the hands-on determination threshold, it is determined that a transition from the "hands-off state" to the "hands-on state" has been detected.
(b) If the counter value is less than the hands-off determination threshold, it is determined that a transition from the "hands-on state" to the "hands-off state" has been detected.

In this embodiment, the hands-on determination threshold is set to a predetermined maximum value. Also, the hands-off determination threshold is set to "1".
As shown in FIG. 14, the increment of the counter value of the hands-on-off counter is started, and when the counter value becomes equal to or greater than the hands-on determination threshold value, the "hands-on state" is determined.
Decrement of the counter value of the hands-on-off counter is started, and when the counter value becomes less than the hands-off determination threshold value, it is determined to be in the "hands-off state".
Since hands-on/hands-off detection is not performed unless a period satisfying a predetermined condition continues, robust hands-on/hands-off detection that is resistant to noise is possible.

Note that although the hands-on determination threshold and the hands-off determination threshold are different thresholds in the present embodiment, they may be the same threshold.

Note that the increment amount and decrement amount of the hands-on-off counter need not be the same. For example, as shown in FIG. 14, by making the increment amount larger than the decrement amount, the transition from the hands-off state to the hands-on state can be quickly detected in a short time. In addition, since it takes time to detect the transition from the hands-on state to the hands-off state, robust and highly reliable hands-off detection becomes possible. Such detection characteristics are optimal for hands-on/hands-off detection in an autonomous driving system in which autonomous driving is enabled in the hands-on state and disabled in the hands-off state. This is because it is desirable to disable automatic operation after performing robust and highly reliable "hands-off detection" in order to reduce the risk of malfunction due to erroneous detection.

On the other hand, in a parking assist system that assists the driver in parking, the parking assist function is disabled in the hands-on state, and the parking assist function is enabled in the hands-off state. That is, in a parking assist system, it is necessary to disable the parking assist function after performing robust and reliable "hands-on detection". Therefore, in the parking assist system, by making the increment amount smaller than the decrement amount and taking time to detect the transition from the hands-off state to the hands-on state, robust and highly reliable hands-on detection becomes possible.

When the determination unit 56 detects the hands-on state, it outputs a hands-on flag (HOD Flag).

According to the hands-on-off detection device 200 of the present embodiment and the electric power steering device 100 equipped with the hands-on-off detection device 200, the steering state observer 51 estimates the steering torque estimated value ̂Ts. Further, the difference between the steering torque Ts and the estimated steering torque value ̂Ts is multiplied by a predetermined coefficient to obtain an estimated disturbance torque value ̂Tdis (Tdis with a hat). By comparing whether the disturbance torque estimated value ^Tdis and the steering torque Ts are in the same phase or in the opposite phase, the disturbance torque is the driver torque input from the input shaft side generated by the driver steering. or road surface reaction torque input from the output shaft side caused by a road surface reaction force or the like. This enables robust hands-on/hands-off detection even when road surface reaction torque is generated.

Further, according to the hands-on-off detection device 200 of the present embodiment and the electric power steering device 100 equipped with the hands-on-off detection device 200, the estimated steering torque Ts and the steering torque Ts detected by the torque sensor 29 are Low-pass filtering is performed on the As a result, the noise component is removed, and it becomes possible to determine with high accuracy whether the hands-on state or the hands-off state.

Further, according to the hands-on-off detection device 200 of the present embodiment and the electric power steering device 100 equipped with the hands-on-off detection device 200, the steering state observer 51 uses the motor torque Tm of the electric motor 30 as an input. Furthermore, the steering state observer 51 uses the corrected motor torque after converting it into a corrected motor torque that takes into account errors such as deformation of the worm gear that change with the motor torque Tm. By correcting the error of the worm gear, the steering torque estimated value ̂Ts can be estimated with higher accuracy.

Further, according to the hands-on-off detection device 200 of the present embodiment and the electric power steering device 100 equipped with the hands-on-off detection device 200, even if the driver grips the steering wheel with both hands, even if the driver grips the steering wheel with one hand, hands-on state can be detected.

As described above, the first embodiment of the present invention has been described in detail with reference to the drawings, but the specific configuration is not limited to this embodiment, and design changes and the like are included within the scope of the present invention. . Also, the constituent elements shown in the above-described first embodiment and modifications can be configured by appropriately combining them.

(Modification 1)
For example, the electric power steering apparatus 100 according to the above embodiment is a column assist type electric power steering apparatus, but the form of the electric power steering apparatus is not limited to this. The electric power steering device may be of the downstream type or of the steer-by-wire type. In either method, robust hands-on/hands-off detection against road surface reaction torque and the like can be performed.

(Second embodiment)
A second embodiment of the present invention will be described with reference to FIGS. 15 to 17. FIG. In the following description, the same reference numerals are given to the same configurations as those already described, and redundant descriptions will be omitted.

LDW (Lane Depure Warning) is a function that vibrates the steering wheel 1 so that the vehicle does not deviate from the lane. The vibration frequency of the vibration caused by the LDW is about 10 to 20 [Hz], and when the LDW function is activated, the static friction of the steering mechanism decreases, making it difficult to estimate the driver's steering torque estimation value ^Ts. Become. As a result, hands-on/hands-off detection becomes difficult.

The electric power steering device 100B equipped with the hands-on/off detection device 200B according to the second embodiment can perform hands-on/hands-off detection with high accuracy even when LDW (Lane Depure Warning) is enabled and operating.

FIG. 15 is a functional block diagram of the ECU 33 of the hands-on/hands-off detection device 200B according to the second embodiment when the ECU 33 performs hands-on/hands-off detection. The hands-on/off detection device 200B according to the second embodiment differs from the hands-on/off detection device 200 according to the first embodiment only in the functional block diagram of the ECU 33 when detecting hands-on/hands-off.

As shown in FIG. 15, functional blocks used when the ECU 33 performs hands-on/hands-off detection include a steering state observer (observer) 51, a low-pass filter 52, a low-pass filter 53, a phase comparator 54, and a first threshold value. In addition to the comparison section 55 and the determination section 56B, it is composed of an LDW bandpass filter 57 and a second threshold comparison section 58 . The judging section 56B differs from the judging section 56 of the first embodiment in a part of the judging method.

The LDW bandpass filter 57 is a bandpass filter that matches the frequency of the LDW, and filters the disturbance torque estimation value ^Tdis (Tdis with a hat) output by the lowpass filter 52 . The disturbance torque estimated value Th after the band-pass filter processing is output to the second threshold comparing section 58 .

The LDW bandpass filter 57 receives an LDW Active Flag (F _LDW ), which is an operation flag indicating that the LDW function is enabled. The LDW bandpass filter 57 is enabled only when the LDW Active Flag is significant and the LDW function is enabled.

FIG. 16 is a Bode diagram of a bandpass filter with a center frequency of 20 Hz. In order to reduce the influence of low frequencies, the gain difference of the bandpass filter is set to 40 bB or more.

FIG. 17 is a graph comparing the presence and absence of LDW bandpass filtering. In the case of no LDW bandpass filtering shown on the left side of FIG. 17, the driver steers the steering wheel from 1 deg to 100 deg. On the other hand, in the case of LDW band-pass filtering, as shown on the right side of FIG. 17, there is a difference in the disturbance torque estimation value between the hands-on state and the hands-off state, so hands-on/hands-off detection is facilitated.

As with the first threshold comparison section 55 of the first embodiment, the second threshold comparison section 58 determines that the absolute value of the disturbance torque estimated value Th subjected to the LDW bandpass filter processing is the torque threshold (for example, 0.1 [Nm]). is greater than.

The determination unit 56B receives the LDW Active Flag (F _LDW ). When the LDW Active Flag is not significant and the LDW function is disabled, the operation of the determination section 56B is the same as the operation of the determination section 56 of the first embodiment.

On the other hand, when the LDW Active Flag (F _LDW ) is significant and the LDW function is enabled, the determination unit 56B performs hands-on/hands-off detection as follows.
The hands-on-off counter is set so that (i) the disturbance torque estimation value ^Tdis input via the low-pass filter 52 and the steering torque Ts are in phase, and (ii) the disturbance torque input via the LDW band-pass filter 57 When the estimated value Th exceeds the torque threshold, it is incremented (added) by a predetermined increment amount. This processing is performed at predetermined intervals. If the above conditions (i) and (ii) are not satisfied when the result flag is checked at a predetermined cycle, the hands-on-off counter is decremented (subtracted) by a predetermined decrement amount.

The counter value of the hands-on-off counter is compared with a hands-on determination threshold value and a hands-off determination threshold value set within a range from zero to a predetermined maximum value.
(a) If the counter value is equal to or greater than the hands-on determination threshold, it is determined that a transition from the "hands-off state" to the "hands-on state" has been detected.
(b) If the counter value is less than the hands-off determination threshold, it is determined that a transition from the "hands-on state" to the "hands-off state" has been detected.

According to the hands-on-off detection device 200B of the present embodiment and the electric power steering device 100B equipped with the hands-on-off detection device 200B, whether the hands-on state or the hands-off state is highly discriminated even when the LDW function is activated. Accurate judgment is possible.

INDUSTRIAL APPLICABILITY The present invention can be applied to an electric power steering system.

100, 100B Electric power steering device 200, 200B Hands-on-off detection device 1 Handle 2 Steering mechanism 20 Steering shaft 21 Input shaft 22 Output shaft 23 Torsion bar 24 Universal joint 25 Intermediate shaft 26 Pinion rack mechanism 27a Tie rod 27b Tie rod 28a Hub unit 28b hub unit 29 torque sensor 3 steering assist mechanism 30 electric motor 31 reduction mechanism 31a worm gear 31b worm wheel 32 vehicle speed sensor 34 controller 35 motor drive circuit 36 CPU
37 memory 38 storage unit 39 input/output control unit 41 current command value calculation unit 42A addition unit 42B subtraction unit 43 current limiting unit 44 compensation signal generation unit 45 PI (proportional integral) control unit 46 PWM control unit 51 steering state observer (observer)
52 low-pass filter 53 low-pass filter 54 phase comparison unit 55 first threshold comparison unit 56, 56B determination unit 57 band-pass filter 58 second threshold comparison unit

Claims (9)

a torque sensor attached to an input shaft to which a handle is connected and an output shaft to which the input shaft is connected;
an electric motor coupled to the output shaft and connected to an angle sensor for detecting a rotor rotation angle and a current sensor for detecting a motor current value;
a controller connected to the torque sensor and the electric motor;
with
The control unit acquires steering torque from the torque sensor,
The control unit acquires the rotor rotation angle and the motor current value from the electric motor,
The control unit calculates a motor torque by multiplying the motor current value by a torque constant,
The control unit estimates disturbance torque, which is torque other than the motor torque among torques acting on the input shaft and the output shaft, from the steering torque, the rotor rotation angle, and the motor torque, and
The control unit
performing low-pass filter processing on the disturbance torque and the steering torque;
comparing the phases of the disturbance torque after the low-pass filter processing and the steering torque;
determining that the disturbance torque is the torque input from the input shaft side when it is determined that the disturbance torque and the steering torque are in phase;
when it is determined that the disturbance torque and the steering torque are in opposite phase, it is determined that the disturbance torque is the torque input from the output shaft side;
Hands-on-off detector. The control unit
has a counter,
when it is determined that the disturbance torque is the torque input from the input shaft side, adding a predetermined addition value to the counter value of the counter;
if the conditions for adding the counter value are not satisfied, subtracting a predetermined subtraction value from the counter value;
When the counter value exceeds a predetermined hands-on determination threshold value, it is determined that the driver is in a hands-on state in which the driver is gripping the steering wheel,
2. The hands-on/off detection device according to claim 1, wherein when the counter value is less than a predetermined hands-off determination threshold value, it is determined that the driver is in a hands-off state in which the driver is not gripping the steering wheel. The control unit
When it is determined that the disturbance torque is the torque input from the input shaft side and when the disturbance torque after the low-pass filter processing is greater than a predetermined torque threshold, the counter value is increased by a predetermined addition value. to add,
3. A hands-on-off detection device according to claim 2. The control unit, during a period in which a predetermined operation flag is activated,
When it is determined that the disturbance torque is the torque input from the input shaft side, and when the disturbance torque subjected to band-pass filtering after the low-pass filtering is greater than a predetermined torque threshold, the counter add a value by a given addition value,
3. A hands-on-off detection device according to claim 2. converting the motor torque into a corrected motor torque that takes into consideration the operating error of the electric motor;
A hands-on-off detection device according to any one of claims 1 to 4. the addition value is greater than the subtraction value;
A hands-on-off detection device according to any one of claims 2 to 4. An electric power steering device equipped with the hands-on-off detection device according to any one of claims 1 to 6. a steering torque detection step of detecting steering torque from an input shaft to which a steering wheel is connected and an output shaft connected to the input shaft;
a rotor rotation angle detection step of detecting a rotor rotation angle from an electric motor coupled to the output shaft;
a motor current value detection step of detecting a motor current value from the electric motor;
a motor torque calculation step of calculating a motor torque obtained by multiplying the motor current value by a torque constant;
a corrected motor torque calculation step of calculating a corrected motor torque from the motor torque and a deformation characteristic of a speed reduction mechanism coupled to the electric motor;
external for estimating disturbance torque, which is torque other than the motor torque among torques acting on the input shaft and the output shaft, from the steering torque, the rotor rotation angle, the motor torque, and the corrected motor torque; a torque estimation step;
External torque estimation method. a torque sensor attached to an input shaft to which a handle is connected and an output shaft to which the input shaft is connected;
an electric motor connected to the output shaft and connected to an angle sensor for detecting a rotor rotation angle and a current sensor for detecting a motor current value;
a controller connected to the torque sensor and the electric motor;
A hands-on-off detection device comprising:
causing the control unit to acquire the steering torque from the torque sensor;
causing the control unit to acquire the rotor rotation angle and the motor current value from the electric motor;
causing the control unit to calculate a motor torque obtained by multiplying the motor current value by a torque constant;
causing the control unit to estimate disturbance torque, which is torque other than the motor torque among torques acting on the input shaft and the output shaft, from the steering torque, the rotor rotation angle, and the motor torque;
to the control unit,
performing low-pass filter processing on the disturbance torque and the steering torque;
comparing the phases of the disturbance torque after the low-pass filter processing and the steering torque;
If it is determined that the disturbance torque and the steering torque are in phase, it is determined that the disturbance torque is the torque input from the input shaft side;
When it is determined that the disturbance torque and the steering torque are in opposite phase, determining that the disturbance torque is the torque input from the output shaft side;
Hands-on-off detector control program.

Images