Steering assistance display device

The steering assistance display device according to this invention includes: a determination unit determining a radius of a curved road on which a vehicle travels, and a velocity and a steering angle of the vehicle; a calculation unit calculating a direction of travel of the vehicle on the basis of an inertial force determined on the basis of the radius and the velocity of the vehicle, and the steering angle; and a display unit displaying by a head-up display a direction of travel.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2013-124136 filed on Jun. 12, 2013 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a steering assistance display device which displays required information to a driver when steering a vehicle.

2. Description of Related Art

When approaching a corner while driving a vehicle, the act of “predicting how far to turn the steering wheel” is generally much more difficult for a beginner than for an experienced driver. An experienced driver can understand, in an instinctive fashion, the predicted path of travel of the vehicle, from the relationship between the vehicle speed and the radius of the corner, based on his or her vision and experience, and can perform a steering operation in accordance with this instinctive understanding. On the other hand, a beginner performs a steering operation by looking at a relatively close point on the corner. Therefore, the beginner cannot “read” the end of the corner, and adjusts the steering angle while in the curve, which is liable to give rise to wobbles in the travel of the vehicle.

In order to prevent wobbling of this kind, Japanese Patent Application Publication No. 5-058196 (JP 5-058196 A) discloses displaying virtual vehicle wheels to a driver by a display device, such as a head-up display (HUD), in the vicinity of the bonnet, as a parameter indicating the actual steering angle of the vehicle wheels.

However, by displaying the actual steering angle, it is only possible to provide a predicted path of travel when the vehicle is at low speeds, and it is not possible to prompt a beginner to predict the path of travel in a broad vehicle speed range, and therefore the beginner cannot be prompted to perform a suitable steering operation. In other words, with the available technology, there has been a problem in that it has been difficult to prompt such a driver to perform a suitable steering operation.

SUMMARY OF THE INVENTION

Therefore, it is an object of this invention to provide a steering assistance display device capable of displaying necessary information for prompting a driver to perform a suitable steering operation.

The steering assistance display device relating to an aspect of this invention includes: a detection unit configured to detect a radius of a curved road on which a vehicle is travelling, and a velocity and a steering angle of the vehicle; a calculation unit configured to calculate a direction of travel of the vehicle on the basis of an inertial force determined on the basis of the radius and the velocity, and the steering angle; and a display unit configured to display by an HUD the direction of travel.

According to the steering assistance display device of the aspect of the invention, since the direction of travel of the vehicle is calculated on the basis of an inertial force determined on the basis of the radius and velocity, and the steering angle, then it is possible to prompt a driver to perform a suitable steering operation.

DETAILED DESCRIPTION OF EMBODIMENTS

Below, an embodiment of this invention is described with reference to the drawings.

As shown inFIG. 1, the steering assistance display device1according to the first embodiment includes an HUD unit electronic control unit (ECU)2, a display device4, a concave mirror5which projects a display image of the display device4onto a front windshield3of a vehicle, and a reflecting surface3a, provided on the front shield3, which reflects the displayed image. The HUD unit ECU2is connected to a car navigation ECU6, a brake ECU7, and an electronic power steering (EPS) ECU8, by a communication standard such as controller area network (CAN).

The front windshield3is the glass window on the front side of the vehicle, and the reflecting surface3ais formed by appropriate means, such as providing a combiner, for example, on the surface of the region where a display image of the cabin interior is to be projected.

The display device4is composed by an light emitting diode (LED) array including a plurality of LED elements and a thin-film transistor (TFT) screen having a backlight, for example, and projects a display image of the vehicle relating to this invention onto the concave mirror5. The concave mirror5has a function of reflecting and enlarging the projected display image so that the image passes through an opening in an instrument panel (not illustrated) to be projected onto the reflecting surface3aof the front windshield3, thereby forming a virtual image in front of the vehicle. A driver views the display image as a virtual image by viewing the reflecting surface3a.

The HUD unit ECU2is, for example, composed by a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), a data bus interconnecting these, an input/output interface, and the like, and the CPU carries out the prescribed processing described below, in accordance with a program stored in the ROM. The HUD unit ECU2composes a detection unit2a, a calculation unit2band a display unit2c.

The car navigation ECU6detects the location of the vehicle by a global positioning system (GPS) function, and also reads out, from database, map information including the radius R of the road along which the vehicle is travelling, and sends this information to the HUD unit ECU2via a CAN.

The brake ECU7is an ECU which controls the whole braking function of the vehicle. The brake ECU7calculates the velocity V of the vehicle from an output signal from a vehicle wheel speed sensor (not illustrated) and sends data frames including the vehicle velocity V to the HUD unit ECU2.

The HUD ECU8is an ECU for controlling the EPS on the basis of the driver's operation of the steering wheel. The EPS ECU8detects the steering angle0of the vehicle wheels based on the EPS, by a steering angle sensor (not illustrated), and sends same to the HUD unit ECU2.

The detection unit2aof the HUD unit ECU2detects, from the CAN, the radius R of a curving road on which the vehicle is travelling, the velocity V of the vehicle, and the steering angle θ, on the basis of communications with the car navigation ECU6, the brake ECU7, and the EPS ECU8. The calculation unit2bof the HUD unit ECU2calculates the direction of travel of the vehicle on the basis of an inertial force, which is determined from the radius R and the vehicle velocity V, and the steering angle θ.

More specifically, the calculation unit2bcalculates a correction steering angle Δθ from the radius R and the vehicle velocity V, and calculates a display steering angle, Θ=θ−Δθ, as the direction of travel, by subtracting the correction steering angle ≢θ from the steering angle θ. The display unit2cof the HUD unit ECU2displays a shallow display steering angle θ which is calculated by the formula above, in front of the driver, by the HUD, on the basis of controlling the display device4.

Here, as shown inFIG. 2, the steering angle of the vehicle travelling at a velocity V along a curving road having a radius of R is taken as θ1. The actual steering angle θ2detected by the steering angle sensor and sent by the EPS ECU8is given by θ1=θ2, if the vehicle velocity V is ignored. This is based on the fact that correction based on the correction steering angle Δθ, which is an inertial force correction, is carried out in the first embodiment. Therefore, in this first embodiment, the steering angle detected by the steering angle sensor is taken as θ, and is used directly in the calculation of the display steering angle Θ.

Furthermore, in calculating the correction steering angle Δθ, the relational expression, Δθ=βmV2/R=αV2is used. Here, m is the vehicle weight and α and β are coefficients obtained by experimentation or simulation. In other words, as shown inFIG. 3, if the vehicle velocity V is plotted on the horizontal axis and the correction steering angle Δθ is plotted on the vertical axis, then the smaller the radius R, the larger the gradient of the resulting quadratic curve.

Here, as shown inFIG. 4A, the display unit2cdisplays the display steering angle Θ, on the basis of the rotation of the centre MC of an assistance display mark M, which is an upwardly-convex laterally-long semi-ellipse shape. Here, inFIG. 4A, the single-dotted line C indicates the front/rear direction of the vehicle (vehicle body), and the display steering angle Θ is indicated by the angle between the arrow showing the centre of the assistance display mark M and the single-point line C. In other words, the display steering angle Θ is shown with reference to the front/rear direction C.

Upon confirming the shallow display steering angle Θ=θ−Δθ which is shown inFIG. 4A, the driver selects an ideal steering angle θ+Δθ on the basis of general driving characteristics (reactive characteristics whereby the driver recognizes that with the current steering operation, the vehicle is travelling to the outside of the curve of the road, and steers the vehicle more tightly). If the vehicle is travelling along a straight road as shown inFIG. 4B, both the steering angle θ and the display steering angle Θ become zero, and the arrow indicating the centre of the assistance display mark M coincides with the dotted line C.

When the detection unit2adetects the ideal steering angle θ+Δθ after amendment by the driver, the display unit2cdisplays the currently amended steering angle θ+Δθ, and in the next control period displays another shallow display steering angle Θ on the basis of the new vehicle velocity V, the radius R and the steering angle θ.

Next, the details of the control performed by the HUD unit ECU2according to the first embodiment will be described with reference to the flowchart shown inFIG. 5. As shown in step S1, the detection unit2adetects and acquires the vehicle velocity V, the steering angle θ, and map information including the radius R, from the CAN. In step S2, the calculation unit2bcalculates a correction steering angle Δθ, which is an inertial force correction, from the radius R and the vehicle velocity V, by the method described above.

In step S3, the calculation unit2bcalculates the display steering angle Θ by subtracting the correction steering angle Δθ from the steering angle θ. In step S4, the display unit2cdisplays this shallow display steering angle Θ by using the HUD.

Here, the display processing in step S4is continued until the driver, in response to the display of the shallow display steering angle Θ, selects the ideal steering angle θ+Δθ, which is a tighter steering angle, based on general driving characteristics, and in step S5, the detection unit2adetects the steering angle θ+Δθ. When the steering angle θ+Δθ has been detected in step S5, then in step S6, the display unit2cdisplays the display steering angle Θ=θ+Δθ.

The mode of the assistance display mark M is not limited to that shown inFIGS. 4A and 4B. For example, as shown inFIG. 6A, the assistance display mark M may adopt a mode which combines a thick-lined arrow with a lateral bar in the left/right direction. Furthermore, as shown inFIG. 6B, the assistance display mark M may adopt a mode which combines a semi-elliptical shape with the mode inFIG. 6A.

Moreover, as shown inFIG. 6C, the assistance display mark M may adopt the mode inFIG. 6B, and also include a dotted line indicating the direction of the thick dotted arrow. Furthermore, as shown inFIG. 6D, the assistance display mark M may also be a chevron shape formed by an isosceles triangle having different angles with the bottom edge removed, and as shown inFIG. 6E, may also include a dotted line indicating the direction of orientation of the chevron.

According to the steering assistance display device1according to the first embodiment described above, the following actions and beneficial effects can be obtained. More specifically, in the first embodiment, by determining a correction steering angle Δθ which takes account of inertial forces, from the vehicle velocity V and the radius R, and showing the display angle Θ shallowly, it is possible to cause the driver to select an ideal steering angle θ+Δθ which is a tighter steering angle that takes account of the inertial force. In other words, in the first embodiment, it is possible to prompt a suitable steering operation at high speeds, which could not be achieved conventionally.

In the first embodiment described above, the display steering angle Θ is used as the direction of travel of the vehicle, but it is also possible to use the predicted path of travel. A second embodiment related thereto is described below. The hardware composition of the steering assistance display device1according to the second embodiment is the same as that shown in the first embodiment, and therefore the description centers on the points of difference.

In the steering assistance display device1according to the second embodiment, the calculation unit2bof the HUD unit ECU2calculates a correction steering angle Δθ from the radius R and the vehicle velocity V, calculates a travel steering angle Θ by subtracting the correction steering angle Δθ from the steering angle θ, and calculates the predicted path of travel D as the direction of travel of the vehicle, on the basis of the travel steering angle Θ and the vehicle velocity V. In other words, the calculation unit2bcalculates the travel steering angle Θ and the predicted path of travel D when continuing in the path of travel direction B included in map information including the radius R, by autonomous navigation, for example. The display unit2cdisplays the predicted path of travel D on the HUD, together with the path of travel direction B.

The display mode of the display unit2cis as shown inFIG. 7, for example. In other words, the display unit2cdisplays the predicted path of travel D in green as a dotted line, and displays the path of travel direction B in white as a solid line. Below, the details of control by the steering assistance display device1according to the second embodiment are described with reference toFIG. 8.

As shown in step S11inFIG. 8, the detection unit2aacquires the vehicle velocity V, the steering angle θ, and map information including the radius R, from the CAN. In step S12, the calculation unit2bcalculates the correction steering angle Δθ, which is an inertial force correction, from the radius R and the vehicle velocity V, by a similar method to that in the first embodiment. In step S13, the calculation unit2bcalculates the travel steering angle Θ=θ−Δθ, and in step S14, the calculation unit2bcalculates the predicted travel of path D from the travel steering angle Θ.

In step S15, the calculation unit2bcalculates the path of travel direction B from the radius R and the map information. In step S16, the display unit2cdisplays the predicted path of travel D, with reference to the path of travel direction B.

According to the steering assistance display device1of the second embodiment described above, the following actions and beneficial effects can be obtained. More specifically, by determining a correction steering angle Δθ that takes account of inertial force, and a shallow travel steering angle Θ=θ−Δθ, from the vehicle velocity V and the radius R, and displaying a shallow predicted path of travel D based on the travel steering angle Θ, it is possible to cause the driver to select an ideal steering angle θ+Δθ which is a tighter steering angle that takes account of inertial force. In other words, in the second embodiment, it is possible to prompt a suitable steering operation at high speeds, which could not be achieved conventionally.

In the second embodiment described above, it is also possible display an even more shallow predicted path of travel D on the basis of the selection made by the driver. A third embodiment related thereto is described. The hardware composition of the steering assistance display device1according to the third embodiment is the composition shown in the second embodiment, to which a selector switch9is added as a selection unit. The following description centers on the points of difference.

More specifically, the steering assistance display device1according to the third embodiment includes a selector switch9as a selection unit capable of selecting an inside mode for travelling the inner side of the radius R of a curving road. The driver can select “inside mode”, on the basis of an appropriate operation of the selector switch9. As shown inFIG. 10, if this “inner mode” is selected (α inFIG. 10), then the display unit2cdisplays the predicted path of travel D on the outer side of the radius R, compared to when the inside mode is not selected (β inFIG. 10).

The control details of the third embodiment are as shown in the flowchart inFIG. 11. In the flowchart inFIG. 11, steps S17and S18are added to the flowchart shown inFIG. 8. As shown in step S17, the calculation unit2bamends the predicted path of travel D so as to be positioned to the outer side of the radius R, if the “inside mode” is selected by the selector switch9. In step S16, the display unit2cdisplays the amended predicted path of travel D and the path of travel direction B, by the HUD.

In other words, according to the third embodiment, in the steering assistance display device1shown in the second embodiment, it is possible to select to travel on the inside of the curving road, on the basis of a selection made by the driver. Moreover, if the past travel trajectories of the vehicle with respect to curving roads as illustrated by the diagonal lines inFIG. 12are available, for instance, in a database controlled by the car navigation ECU6, and furthermore, if the past slippage history of the vehicle with respect to curving roads as indicated by the mesh hatching inFIG. 13is available in the abovementioned database, then these can also be displayed by the display unit2c.

In other words, a “performance-based travel mode” in which the vehicle is caused to travel along a past travel trajectory of the vehicle on a curving road can be selected by a selector switch9(a selection unit), and if this performance-based travel mode is selected, then the display unit2cdisplays the travel trajectory by the HUD.

Similarly, a “history-based travel mode” in which the vehicle is caused to travel in accordance with past slippage history of the vehicle on a curving road can be selected by a selector switch9(a selection unit), and if this history-based travel mode is selected, then the display unit2cdisplays the slippage history by the head-up display. As shown inFIG. 14, these control details are executed by the HUD unit ECU2by adding the processing details from step S19to S22, to the control details inFIG. 11. Only one of the steps19and20in which, if this performance-based travel mode is selected, then the display unit2cdisplays the travel trajectory by the HUD, and the steps in which, if this history-based travel mode is selected, then the display unit2cdisplays the slippage history by the head-up display may be applied a control flowchart as shown inFIG. 14.

In other words, as shown in step S19, the calculation unit2bdetermines whether or not the “performance-based travel mode” has been selected by the selector switch9and if this mode has been selected, then in step S20, the display unit2cdisplays a past travel trajectory as shown inFIG. 12. Furthermore, in step S21, the calculation unit2bdetermines whether or not the “history-based travel mode” has been selected by the selector switch9and if this mode has been selected, then in step S22, the display unit2cdisplays a past slippage trajectory as shown inFIG. 13.

The dotted line shown inFIG. 12differs in significance from the dotted line shown inFIG. 10, and indicates a path of travel which the driver is predicted to trace, in combination with a past travel trajectory. Similarly, the dotted line shown inFIG. 13indicates a trajectory that the driver is predicted to trace, in combination with a past slippage history. Therefore, it is possible to provide customized travel based on the travel performance of the driver. Here, customized travel is a travel mode which is suited to sports travel on a circuit, or limit travel during testing.

Embodiments of this invention were described in detail above, but this invention is not limited to the embodiments described above, and it is also possible to add various modifications and substitutions to the embodiments given above, without departing from the claims of the invention.

In the embodiment described above, the detection unit2adetects the radius R on the basis of the GPS function of the car navigation ECU6and map information, but the detection unit2amay also detect the radius R by a white line detection device.

The above-described embodiments of the invention can prompt a driver to perform a suitable steering operation, by determining a correction steering angle Δθ that takes account of the inertial force, from the vehicle velocity V and the radius R, and displaying the display steering angle Θ or predicted path of travel D shallowly.

Consequently, the steering assistance display device according to the embodiments of the invention is useful in that it can be applied to various automobiles.