JP2024111371A - Steering Assistance Device - Google Patents

Abstract

To improve detection accuracy of steering intervention by a user and enable steering support controllability to be ensured at the time of steering intervention.SOLUTION: A steering support device includes a variable limiter 25 configured to limit a steering servo command current Sc according to steering torque T detected by a torque sensor 13 during parking assist, and includes a torque calculation unit 22 configured to acquire vehicle speed information with a vehicle side sensor S and calculate necessary steering torque required for steering based on the vehicle speed information. When the magnitude of steering torque T1 detected by the torque sensor 13 during parking assist is a threshold T1 or more, the limitation amount of the operation servo command current Sc by the variable limiter 25 is changed and mitigated according to the calculated necessary steering torque.SELECTED DRAWING: Figure 2

Description

This invention relates to a steering assist device that assists in steering a vehicle such as an automobile.

In recent years, some vehicles, such as automobiles, are equipped with a steering assistance function that assists the vehicle user in steering. A specific example is a parking assistance function that provides parking assistance when parking a vehicle. With this parking assistance function, when a parking space (target parking position) is set by the vehicle user in a parking lot at a commercial facility, for example, steering operations are automatically performed so that the vehicle moves from its current position along the target trajectory to the target parking position and is parked in the parking position.

If the user wishes to cancel (end) steering during such a parking assistance function, this must always be given priority. An example of an operation that indicates the user's intention to cancel is steering by the user. One method for detecting this steering operation is to use information (torque sensor value) from a torque sensor mounted on the EPS (Electric Power Steering) system (Patent Document 1).

JP 2021-142891 A (see paragraphs 0002-0004)

In a device that determines whether the user intends to intervene in steering assistance such as parking assistance, even if there is steering intervention by the user, there is a need to ensure controllability of the steering assistance by providing steering assistance so that the steering can be turned even if the user's intervening steering torque is small, but there is also a need to stop steering assistance in order to prioritize the user's steering assistance if there is steering intervention by the user during parking assistance, and these two conflicting needs must be met.

In this case, it is conceivable to provide an electrostatic sensor on the steering wheel so that, once it detects that the user has touched the steering wheel, it can be determined that the user has intended to intervene in steering. However, providing an electrostatic sensor would increase costs.

It is also possible to determine whether the user has intervened in steering from the torque detected by an existing torque sensor without installing a new electrostatic sensor. However, even if the steering torque increases due to the user's intervention in steering, the steering torque is immediately reduced by the steering assist control, and the steering torque detected by the torque sensor becomes small. This makes it difficult to accurately determine whether the user has intervened in steering, and there is a need to develop technology that can more accurately determine the user's intention to intervene in steering.

The purpose of this invention is to improve the accuracy of detecting steering intervention by the user in steering assistance, and to ensure the controllability of steering assistance during steering intervention.

In order to achieve the above-mentioned object, the steering assist device of the present invention is a steering assist device comprising a motor that generates a torque applied to the steering of a vehicle, a torque detection means that detects the steering torque of the steering, a steering angle detection means that detects the steering angle of the steering, and a steering assist means that controls the motor according to a command steering angle and provides a command value to the motor so that the steering angle of the steering coincides with the command steering angle to perform steering assist, the steering assist device further comprising a limiting means that limits the command value by the steering assist means according to the steering torque detected by the torque detection means, and a calculation means that acquires predetermined external information and calculates the necessary steering torque required for steering based on the external information, and the limiting means varies the limit amount of the command value according to the necessary steering torque calculated by the calculation means when the steering torque detected by the torque detection means during steering assist by the steering assist means is equal to or greater than a predetermined value.

According to this configuration, a limiting means is provided for limiting the command value by the steering assist means in response to the steering torque detected by the torque detection means, and a calculation means is provided for acquiring predetermined external information and calculating the required steering torque required for steering based on the external information, and when the steering torque detected by the torque detection means during steering assistance by the steering assist means is equal to or greater than a predetermined value, the amount of limiting the command value by the limiting means is varied in response to the required steering torque calculated by the calculation means.

Therefore, in addition to the normal assist control that allows steering with light force when turning the steering wheel, it is possible to realize steering angle servo control that controls the actual steering angle to match the command steering angle. Then, by setting a limit amount for the command current determined by the steering angle servo control and varying this limit amount, a current is generated in a direction that cancels the normal assist control, which allows adjustment to be made so that a range in which the user can steer with light force and a torque sufficient to detect the user's steering intervention can be generated, making it possible to accurately determine whether or not there has been steering intervention by the user, improving the accuracy of detection of steering intervention by the user in steering assistance and ensuring controllability of steering assistance during steering intervention.

The vehicle may further include a steering assistance stop means for stopping the steering assistance provided by the steering assistance means when the steering torque detected by the torque detection means exceeds the required steering torque calculated by the calculation means.

In this case, when the steering torque detected by the torque detection means exceeds the required steering torque calculated by the calculation means, it can be determined that there has been a definite steering intervention by the user, and the steering assistance can be stopped by the steering assistance stopping means, so that the steering intervention by the user can be prioritized.

The limiting means may also vary the limiting amount of the command value to a smaller amount when the required steering torque calculated by the calculating means is large.

In this way, when the detected steering torque during steering assistance is equal to or greater than a predetermined value, the amount of restriction on the command value can be relaxed by varying it to a small or large amount depending on whether the required steering torque is large or small.

According to the present invention, in the control of steering assistance by the steering assistance means, it is possible to improve the accuracy of detection of steering intervention by the user and ensure the convenience of steering assistance during steering intervention, thereby improving the accuracy of detection of steering intervention by the user and ensuring the controllability of steering assistance during steering intervention.

1 is a diagram showing a configuration relating to steering of a vehicle equipped with a steering assist device according to an embodiment of the present invention; FIG. 2 is a block diagram showing a configuration relating to the steering assistance in FIG. 1, particularly the parking assistance function. FIG. 2 is an explanatory diagram of the operation of FIG. 1;

An embodiment of the steering assist device according to the present invention applied to parking assistance will be described in detail with reference to Figures 1 to 3.

<Steering configuration>
As shown in Fig. 1, a vehicle 1 is equipped with an electric power steering device 2. The electric power steering device (EPS: Electric Power Steering) 2 includes an electric motor M and a steering wheel 3, and is a device that applies torque generated by the electric motor M to the steering wheel 3 to steer the steering wheels (e.g., the left and right front wheels) of the vehicle 1.

The steering 3 includes a handle (steering) 4, a steering gear mechanism 5, and a steering shaft 6.

The handle 4 is, for example, a steering wheel that is rotated by the driver to steer the vehicle 1, and is disposed in front of the driver's seat inside the vehicle cabin.

The steering gear mechanism 5 is, for example, a mechanism that includes a rack-and-pinion type steering gear.

The steering shaft 6 is disposed so as to penetrate from the interior to the exterior of the vehicle. The upper end of the steering shaft 6 is connected to the steering wheel 4. The lower end of the steering shaft 6 is connected to the steering gear mechanism 5. If the steering gear mechanism 5 is configured to include a rack-and-pinion type steering gear, the lower end of the steering shaft 6 is connected to the pinion of the steering gear so as not to rotate relative to it.

The vehicle 1 is also equipped with an EPSECU 7. This EPSECU (Electronic Control Unit) 7 is an ECU (Electronic Control Unit) that mainly controls the electric motor M of the electric power steering device 2. In addition to the EPSECU 7, the vehicle 1 is equipped with multiple ECUs to control various parts, such as a camera ECU 8 that controls the vehicle-mounted camera shown in FIG. 2. These ECUs are connected to enable two-way communication using the CAN (Controller Area Network) communication protocol.

The EPSECU7 is equipped with a microcomputer (microcontroller unit) 10 including a CPU and memory, a current control unit 11 that receives a current command value from the microcomputer 10, and a motor drive circuit 12 consisting of an H-bridge circuit that converts the command current from the current control unit 11 into a voltage.

Various sensors necessary for control are connected to the microcomputer 10. The various sensors include, for example, a torque sensor 13 and a steering angle sensor 14 that detect the steering torque and steering angle, respectively, when the steering wheel is operated. The torque sensor 13 corresponds to the "torque detection means" in the present invention.

The torque sensor 13 is associated with a torsion bar 15 that is attached to the middle of the steering shaft 6, detects the magnitude and direction of the twist that occurs in the torsion bar 15 as steering torque, and outputs a detection signal that corresponds to that steering torque.

The steering angle sensor 14 outputs a detection signal corresponding to the steering angle (absolute steering angle) of the steering wheel 4 relative to the midpoint of the steering angle of the steering wheel 4 (the steering angle of the steering wheel 3). The steering angle detected by the steering angle sensor 14 takes a positive value when the steering wheel 4 is turned to the right from the steering angle midpoint, and takes a negative value when the steering wheel 4 is turned to the left.

The microcomputer 10 sets a command current value based on information obtained from detection signals of various sensors and/or various information input from other ECUs, and controls the switching of the switching elements included in the motor drive circuit 12 so that a drive current equivalent to the command current value is converted into a voltage and supplied to the electric motor M.

<Parking assistance function>
FIG. 2 is a block diagram showing a configuration related to the parking assistance function.

The vehicle 1 has a parking assistance function (automatic parking function). The functional processing units for the parking assistance function include, for example, a surrounding object detection unit, a parking area detection unit, a target parking position setting unit, a vehicle position estimation unit, a parking trajectory calculation unit, a steering control unit, and a driver information provision unit. Of these functional processing units, the EPSECU 7 controls the function of the steering control unit, and the camera ECU 8 processes the surrounding images captured by the vehicle-mounted camera, and controls the functions of the surrounding object detection unit, the parking area detection unit, the target parking position setting unit, the vehicle position estimation unit, the parking trajectory calculation unit, the driver information provision unit, etc.

The surrounding object detection unit detects objects around the vehicle 1 from image information captured by the onboard camera, and also detects information including the shape of the object and the distance to the object (information about the surroundings of the vehicle 1). As onboard cameras, the vehicle 1 is provided with a front camera that captures images in front of the vehicle 1, a back camera that captures images behind the vehicle 1, and side cameras that capture images on the left and right sides of the vehicle 1.

The parking area detection unit detects multiple parking areas around vehicle 1 where vehicle 1 can be parked, based on the surrounding information generated by the surrounding object detection unit.

The target parking position setting unit sets a target parking position in a parking area selected by the user from among the parking areas detected by the parking area detection unit.

The vehicle position estimation unit receives positioning signals from, for example, GNSS (Global Navigation Satellite System) satellites using a GNSS antenna, and estimates the current position of vehicle 1 (vehicle position) from either the vehicle speed, steering angle, or autonomous navigation calculation results based on front and rear G forces, or a combination of these, of the positioning signals received by the GNSS antenna.

The parking trajectory calculation unit calculates the target trajectory of the vehicle 1 from the vehicle position estimated by the vehicle position estimation unit to the target parking position set by the target parking position setting unit, and sets an instructed steering angle, which is a target value for the steering angle of the steering wheel 3, according to the target trajectory. This set instructed steering angle is input from the camera ECU 8 to the EPSECU 7.

The steering control unit controls the steering of the vehicle 1 based on the commanded steering angle.

The driver information providing unit causes the display to show an image of the surroundings of the vehicle 1 and the parking area. The display may be any display that is placed in a position visible to the driver, for example a multi-information display built into a combination meter. When the parking area detection unit detects a parking area in which the vehicle 1 can be parked, the driver information providing unit causes the display to show an image of the surroundings of the vehicle 1, including the detected parking area. The user selects a parking area on the display on which this image is being displayed.

After selecting a parking area, when the driver instructs the display to perform parking assistance using the parking assistance function, the parking assistance operation begins.

The microcomputer 10 of the EPSECU 7 has an assist control unit 21, a required steering torque calculation unit 22, a steering angle servo control unit 23, and a steering angle servo stop control unit 24 as functional processing units realized in software by program processing, and a variable limiter 25 for preventing malfunction due to erroneous calculations in the EPSECU 7. The microcomputer 10 corresponds to the "steering assist means" and "steering assist stop means" in this invention.

The assist control unit 21 calculates the assist control command current Sa according to the steering torque detected by the torque sensor 13 (the steering torque obtained from the detection signal of the torque sensor 13) and the vehicle speed of the vehicle 1 detected by the vehicle speed sensor S connected to the EPSECU 7. Specifically, an assist control command current map that defines the characteristics of the assist control command current Sa with respect to the steering torque is prepared for each of a plurality of vehicle speed ranges, and the assist control unit 21 selects an assist control command current map according to the vehicle speed of the vehicle 1, and calculates the assist control command current Sa according to the steering torque detected by the torque sensor 13 according to the selected assist control command current map. Note that the vehicle speed is not limited to that detected by the vehicle speed sensor S, and may be transmitted to the EPSECU 7 from another ECU.

The required steering torque calculation unit 22 calculates the required steering torque according to the vehicle speed of the vehicle 1 detected by the vehicle speed sensor S, which is predetermined external information. Specifically, a required steering torque map that defines the characteristics of the required steering torque relative to the vehicle speed is prepared for each of a plurality of vehicle speed ranges, and the required steering torque calculation unit 22 selects a required steering torque map according to the vehicle speed detected by the vehicle speed sensor S, and calculates the required steering torque according to the vehicle speed detected by the vehicle speed sensor S according to the selected required steering torque map. Such a function of the required steering torque calculation unit 22 corresponds to the "calculation means" in the present invention. Note that the vehicle speed in this case is not limited to that detected by the vehicle speed sensor S, and may be transmitted to the EPSECU 7 from another ECU.

The steering angle servo control unit 23 calculates the steering angle control amount. Specifically, the steering angle servo control unit 23 receives the actual steering angle and actual steering speed detected by the steering angle sensor 14, as well as the command steering angle obtained by processing the camera image from the camera ECU 8, and calculates the steering angle control amount according to the deviation between the steering angle detected by the steering angle sensor 14 and the command steering angle so that the steering angle detected by the steering angle sensor 14 matches the command steering angle input from the camera ECU 8 to the EPS ECU 7.

The steering angle servo stop control unit 24 judges whether or not to stop the parking assistance while the parking assistance operation is being performed, and stops the parking assistance when the stop condition is met. Specifically, the steering torque detected by the torque sensor 13 is used for the stop judgment, and it judges whether the magnitude (absolute value) of the steering torque by the torque sensor 13 during parking assistance is equal to or greater than a predetermined value. When the magnitude of the steering torque does not exceed the predetermined value, it switches the changeover switch SW provided between the steering angle servo control unit 23 and the variable limiter 25 described later so as to connect the steering angle servo control unit 23 to the variable limiter 25 described later. When the magnitude of the steering torque is equal to or greater than the predetermined value, it judges that the stop condition is met and the user intends to intervene in the steering, and switches the changeover switch SW between the steering angle servo control unit 23 and the variable limiter 25 to the "0" side, and disconnects the steering angle servo control unit 23 from the variable limiter 25 to stop the parking assistance.

For example, when the steering torque T detected by the torque sensor 13 shown in FIG. 3 is equal to or greater than T1 or equal to or less than -T1, that is, when the magnitude (absolute value) of the steering torque T is equal to or greater than a predetermined value T1 (|T|≧T1), the changeover switch SW is switched to the "0" side. Note that the vertical axis of FIG. 3 indicates the steering angle servo command current Sc by the variable limiter 25, and the horizontal axis indicates the steering torque T detected by the torque sensor 13.

The variable limiter 25 is provided to prevent malfunctions due to incorrect calculations in the EPSECU 7, and outputs a steering angle servo command current Sc according to the steering torque detected by the torque sensor 13 during parking assistance.

Specifically, the variable limiter 25 is provided with a steering angle servo command current map according to the steering torque T by the torque sensor 13 during parking assistance as shown in FIG. 3. This map outputs a constant steering angle servo command current Sc when the magnitude (absolute value) of the steering torque does not exceed a predetermined value T1, that is, when -T1<T<tT1, and when the magnitude (absolute value) of the steering torque T is equal to or greater than the predetermined value T1 (|T|≧T1), the steering angle servo stop control unit 24 switches the changeover switch SW between the steering angle servo control unit 23 and the variable limiter 25 to the "0" side. At this time, as shown by the dashed line in FIG. 3, the steering angle servo command current Sc (the "command value" in the present invention) should be limited to 0, but as described below, the limit amount of the steering angle servo command current Sc is relaxed according to the required steering torque calculated by the required steering torque calculation unit 22.

In other words, when the magnitude (absolute value) of the steering torque T by the torque sensor 13 during parking assistance is equal to or greater than a predetermined value T1 (|T|≧T1), the required steering torque calculation unit 22 selects a required steering torque map according to the vehicle speed of the vehicle 1 detected by the vehicle speed sensor S at that time, and the required steering torque according to the vehicle speed detected by the vehicle speed sensor S is calculated according to the selected required steering torque map and input to the variable limiter 25, and the limit amount of the steering angle servo command current Sc is varied within the range of -Sc1 to Sc1 (but not including "0") according to the required steering torque input, as shown by the arrow in FIG. 3.

Specifically, when the vehicle speed is high, the required steering torque is small, and when the vehicle speed is low, the required steering torque is large; therefore, when the required steering torque is small, the limit amount of the steering angle servo command current Sc is large, i.e., the steering angle servo command current Sc is increased toward Sc1 or -Sc1 in the direction of the arrow in FIG. 3, whereas when the required steering torque is large, the limit amount of the steering angle servo command current Sc is small, i.e., it is reduced in the direction opposite to the arrow in FIG. 3, approaching 0 from the steering angle servo command current Sc. Note that it is desirable to vary the variable amount of the limit amount of the steering angle servo command current Sc in stages, for example, to 2V, 3V, 4V, depending on the magnitude of the required steering torque.

In this way, when the magnitude (absolute value) of the steering torque T detected by the torque sensor 13 during parking assistance is equal to or greater than a predetermined value T1, the variable limiter 25 does not limit the steering angle servo command current Sc to 0 according to the required steering torque, but rather varies the limit amount of the steering angle servo command current Sc within a predetermined range (-Sc1 to Sc1, a range other than 0) according to the magnitude of the required steering torque calculated by the required steering torque calculation unit 22, thereby relaxing the limit amount. Therefore, even if the magnitude of the steering torque detected by the torque sensor 13 during parking assistance is equal to or greater than a predetermined value, gentle steering assistance can be continued without completely stopping steering assistance.

As a result, it is possible to suppress the misidentification of an increase in steering torque that is not based on the user's intention to intervene in steering as being due to steering intervention, making it possible to accurately determine whether or not there has been steering intervention by the user, thereby improving the accuracy of detecting steering intervention by the user and ensuring the controllability of steering assistance during steering intervention.

However, if the steering torque T detected by the torque sensor 13 during parking assistance exceeds the required steering torque calculated by the required steering torque calculation unit 22, it can be determined that the user intentionally applied a steering torque greater than the expected required steering torque. In such a case, it can be determined that the user had a clear intention to intervene in the steering. Therefore, by limiting the steering angle servo command current Sc of the variable limiter 25 to 0, parking assistance can be stopped and steering intervention by the user can be prioritized.

As shown in FIG. 2, in the microcomputer 10, the assist control command current Sa calculated by the assist control unit 21 is added to the steering angle servo command current Sc calculated by the variable limiter 25, and the deviation between this sum and the actual motor current value of the motor M is input to the current control unit 11 as the target value of the current supplied to the electric motor M, and the output of the current control unit 11 is converted to a voltage by the motor drive circuit 12 and applied to the electric motor M of the electric power steering device 2, supplying a drive current equivalent to the current target value, and generating an assist torque by the motor M to perform steering assistance.

When the user is not operating the steering wheel 4 (steering wheel operation) and the steering torque detected by the torque sensor 13 is zero, the assist command current calculated by the assist control unit 21 is zero. Therefore, during parking assistance, the steering angle servo command current Sc based on the steering angle control amount calculated by the steering angle servo control unit 23 is basically set as the current target value, and a drive current is supplied from the motor drive circuit 12 to the electric motor M so that the steering angle of the steering wheel 4 matches the instructed steering angle.

Therefore, according to the above-described embodiment, the vehicle is provided with a variable limiter 25 that limits the steering angle servo command current Sc in accordance with the steering torque T detected by the torque sensor 13 during parking assistance, and a required steering torque calculation unit 22 that acquires vehicle speed information from the vehicle speed sensor S and calculates the required steering torque required for steering based on the vehicle speed information. When the magnitude of the steering torque T detected by the torque sensor 13 during parking assistance is equal to or greater than a predetermined value T1, the amount of limiting the steering angle servo command current Sc by the variable limiter 25 is varied in accordance with the calculated required steering torque. Therefore, in addition to the normal assist control that allows steering with light force when steering the steering wheel, the actual steering angle is set to the instructed steering angle. It is possible to realize steering angle servo control that controls the steering angle servo command current Sc to match the steering angle servo control, and by setting a limit amount for the steering angle servo command current Sc determined by the steering angle servo control and varying this limit amount, a current is generated in a direction that cancels the normal assist control, which allows adjustment to be made so that a range in which the user can steer with light force and a torque sufficient to detect the user's steering intervention can be generated. As a result, it becomes possible to accurately determine whether or not the user has intervened in steering. This improves the accuracy of detecting the user's steering intervention in parking assistance, and ensures the controllability of the steering assistance during steering intervention.

In addition, when the steering torque detected by the torque sensor 13 exceeds the required steering torque calculated by the required steering torque calculation unit 22, it can be determined that the user has definitely intervened in the steering, and the parking assistance can be stopped by limiting the steering angle servo command current Sc of the variable limiter 25 to 0, thereby prioritizing the user's steering intervention.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the invention.

For example, in the above embodiment, a case where parking assistance is performed as steering assistance is described, but the steering assistance is not limited to the parking assistance described above, and the present invention can be similarly implemented for other steering assistance.

In addition, in the above embodiment, the command value is a steering angle servo command current by the variable limiter 25, but the command value is not limited to a current and may be a voltage.

In the above embodiment, the vehicle speed from the vehicle speed sensor S is used as external information to calculate the required steering torque, but road surface condition information from a detection means for detecting the road surface friction coefficient (road surface μ) of an anti-skid device mounted on the vehicle may be used, and the limit amount of the command value may be increased when the road surface μ is small and decreased when it is large. In addition, when the steering torque detected by the torque detection means exceeds the required steering torque calculated by the calculation means, information regarding the exceedance of the required steering torque may be stored in the storage means. In this case, the stored information may be taken out to a maintenance shop or the like to analyze the presence of an abnormality caused by the detection of the steering torque.

The present invention can be widely applied to steering assistance devices that assist in steering vehicles such as automobiles.

1 ... vehicle 3 ... steering 10 ... microcomputer (steering assist means, steering assist stop means)
13 ... Torque sensor (torque detection means)
22 ... Required steering torque calculation unit (calculation means)
25 ... Variable limiter (limiting means)

Claims (3)

A steering assist device comprising: a motor that generates a torque applied to a steering wheel of a vehicle; a torque detection means that detects a steering torque of the steering wheel; a steering angle detection means that detects a steering angle of the steering wheel; and a steering assist means that controls the motor in response to a command steering angle and provides a command value to the motor so that the steering angle of the steering wheel coincides with the command steering angle,
a limiting means for limiting the command value by the steering assist means in response to the steering torque detected by the torque detecting means;
A calculation means for acquiring predetermined external information and calculating a necessary steering torque required for steering based on the external information,
The limiting means varies a limiting amount of the command value in accordance with the required steering torque calculated by the calculating means when the steering torque detected by the torque detecting means during steering assistance by the steering assist means is equal to or greater than a predetermined value. The steering assist device according to claim 1,
A steering assist device further comprising a steering assist stop means for stopping the steering assist by the steering assist means when the steering torque detected by the torque detection means exceeds the required steering torque calculated by the calculation means. The steering assist device according to claim 1 or 2,
The steering assist device according to claim 1, wherein the limiting means changes the limiting amount of the command value to a smaller amount when the required steering torque calculated by the calculating means is large.

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