Display control device, display control method, display control computer program, and voice control device

Abstract

To provide a display control device which reduces flickering of vehicle speed display and associated uneasiness felt by a driver when a vehicle is in pulse-and-glide mode.SOLUTION: A display control device is provided, comprising a display control unit 31 configured to display, on a display device 15, display vehicle speed within a display vehicle speed range that is included in and smaller than an actual vehicle speed range, in such a way that the display vehicle speed increases while a vehicle 10 is being accelerated and decreases while the vehicle 10 is gliding, as long as the vehicle 10 is under pulse-and-glide driving control to alternate between acceleration and gliding within a given actual vehicle speed range.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a display control device, a display control method, a computer program for display control, and a voice control device for controlling voices to be generated in the vehicle cabin when the vehicle is traveling in a predetermined direction. [Background technology]

[0002] It is known that fuel consumption can be reduced by a vehicle performing intermittent running (also called pulse-and-glide running), which involves repeating acceleration and coasting within a predetermined vehicle speed range. A technology has been proposed to prevent flickering of the speed display due to speed changes when a vehicle is performing such intermittent running (see Patent Document 1).

[0003] In the proposed technology, the vehicle display device displays a fixed vehicle speed limit when the vehicle is traveling intermittently, and also displays the actual vehicle speed and acceleration / deceleration state when the vehicle is traveling intermittently. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-113720 Summary of the Invention [Problem to be solved by the invention]

[0005] If the speed display is fixed when the vehicle is pulse-and-glide traveling, the vehicle speed is actually changing, which may cause discomfort to drivers who are sensitive to speed changes due to the difference between the displayed vehicle speed and the actual vehicle speed.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a display control device that can reduce flickering of the vehicle speed display and discomfort felt by the driver when the vehicle is traveling in pulse-and-glide mode. [Means for solving the problem]

[0007] A display control device according to one embodiment has a display control unit that causes a display device to display a displayed vehicle speed within a displayed vehicle speed range that is included in the actual vehicle speed range but narrower than the actual vehicle speed range, while the vehicle is under pulse-and-glide driving control so as to repeat acceleration driving and coasting within a predetermined actual vehicle speed range, so that the displayed vehicle speed increases when the vehicle is accelerating and decreases when the vehicle is coasting.

[0008] In one embodiment, the display control device further has a judgment unit that judges whether the situation around the vehicle or the behavior of the vehicle driver satisfies a gaze suppression condition in which the driver does not gaze at the display device, and the display control unit sets the display vehicle speed range when the gaze suppression condition is satisfied to be wider than the display vehicle speed range when the gaze suppression condition is not satisfied.

[0009] In one embodiment, when the pulse-and-glide driving control ends, the display control unit controls the display device so that the displayed vehicle speed approaches the actual vehicle speed at a rate of change that is equal to or less than a predetermined upper limit rate of change.

[0010] Another embodiment of the audio control device has an audio control unit that, while the vehicle is undergoing pulse-and-glide driving control to repeat acceleration driving and coasting within a predetermined vehicle speed range, causes an audio generator mounted on the vehicle to output a pseudo-acceleration sound that simulates the sound produced when the vehicle is accelerating inside the vehicle's cabin when the vehicle is coasting.

[0011] In one embodiment, the sound control unit reduces the volume of the pseudo acceleration sound as the noise generated when the vehicle is running increases.

[0012] A display control method according to yet another embodiment includes, while a vehicle is under pulse-and-glide driving control so as to repeat acceleration driving and coasting within a predetermined actual vehicle speed range, displaying the displayed vehicle speed on a display device so that the displayed vehicle speed increases when the vehicle is accelerating and decreases when the vehicle is coasting within a displayed vehicle speed range that is included in the actual vehicle speed range and narrower than the actual vehicle speed range.

[0013] In yet another embodiment, a computer program for display control includes instructions to cause a processor mounted on a vehicle to display a display vehicle speed on a display device so that the displayed vehicle speed increases when the vehicle is accelerating and decreases when the vehicle is coasting, within a display vehicle speed range that is included in the actual vehicle speed range and narrower than the actual vehicle speed range, while the vehicle is being controlled by pulse and glide driving to repeat acceleration and coasting within a predetermined actual vehicle speed range. [Effects of the Invention]

[0014] The display control device according to the present disclosure has the effect of reducing flickering of the vehicle speed display and discomfort felt by the driver when the vehicle is pulse-and-glide driving. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic configuration diagram of a vehicle in which an electronic control device that is an example of a display control device or a voice control device is implemented. [Figure 2] FIG. 2 is a functional block diagram of a processor of an ECU related to display control processing according to the first embodiment. [Figure 3] FIG. 10 is a diagram showing an example of the relationship between changes in actual vehicle speed and changes in displayed vehicle speed when pulse-and-glide driving control is applied to the vehicle. [Figure 4] 4 is an operation flowchart of a display control process according to the first embodiment. [Figure 5] FIG. 10 is a functional block diagram of a processor of an ECU related to voice control processing according to a second embodiment. [Figure 6]FIG. 10 is a diagram showing an example of the relationship between changes in actual vehicle speed and the output of pseudo acceleration sound when pulse-and-glide driving control is applied to the vehicle. [Figure 7] 10 is an operational flowchart of a voice control process according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, with reference to the drawings, a display control device, a display control method executed on the display control device, and a computer program for display control, as well as a voice control device, a voice control method executed on the voice control device, and a computer program for voice control, will be described. While the vehicle is undergoing pulse-and-glide driving control so as to alternate between acceleration and coasting within a predetermined actual vehicle speed range, this display control device sets a change range of the displayed vehicle speed (hereinafter referred to as the display vehicle speed range) displayed to the driver to be narrower than the actual vehicle speed range. Furthermore, while the vehicle is undergoing pulse-and-glide driving control, the voice control device generates a pseudo-acceleration sound by using a sound generator during coasting, which simulates the sound generated during acceleration. Hereinafter, pulse-and-glide driving control will be referred to as PS driving control.

[0017] 1 is a schematic configuration diagram of a vehicle in which an electronic control device, which is an example of a display control device or a voice control device, is implemented. In this embodiment, the vehicle 10 is preferably a vehicle in which a powertrain 11 includes a motor as a power source, such as a battery electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle, from the perspective of improving fuel efficiency through PS driving control. However, the vehicle 10 may also be a vehicle in which the powertrain 11 includes only a power source other than a motor, such as an engine. The vehicle 10 has a vehicle speed sensor 12, an external sensor 13, a driver monitor camera 14, a display device 15, a voice generator 16, and an electronic control unit (ECU) 17.

[0018] The vehicle speed sensor 12 measures the speed of the vehicle 10 , generates a speed signal representing the speed of the vehicle 10 , and outputs the speed signal to the ECU 17 .

[0019] The exterior sensor 13 is a sensor that generates an exterior sensor signal that indicates the situation around the vehicle 10, and is, for example, an exterior camera that is installed so as to be able to capture images of the area around the vehicle 10, or a distance measurement sensor such as a LiDAR or radar. The vehicle 10 may be provided with a plurality of exterior sensors 13 with different detectable ranges or types. Each time the exterior sensor 13 generates an exterior sensor signal, the exterior sensor 13 outputs the generated exterior sensor signal to the ECU 17.

[0020] The driver monitor camera 14 is an example of an in-vehicle sensor, and is attached to the instrument panel or its vicinity, facing the driver seated in the driver's seat of the vehicle 10, so that the head of the driver is included in the imaging target area. The driver monitor camera 14 may have a light source such as an infrared LED. The driver monitor camera 14 captures an image of the driver at each predetermined imaging period to generate an image of the driver (hereinafter referred to as a driver image), and outputs the generated driver image to the ECU 17.

[0021] The display device 15 is provided in the cabin of the vehicle 10. The display device 15 has a display device such as a liquid crystal display or an organic EL display. Furthermore, the display device 15 may have a meter such as a speedometer. The display device 15 is installed in the cabin of the vehicle 10, for example, on an instrument panel, facing the driver. The display device 15 notifies the driver of various information received from the ECU 17 via the in-vehicle network by displaying the information. In this embodiment, the display device 15 displays at least the vehicle speed of the vehicle 10. The vehicle speed may be displayed in an analog format or a digital format.

[0022] The sound generator 16 outputs sound to the interior of the vehicle 10 in response to control from the ECU 17. To this end, the sound generator 16 has a generation circuit that generates a sound signal in response to a control signal from the ECU 17, and a speaker that outputs sound in response to the sound signal generated by the generation circuit.

[0023] The ECU 17 is capable of executing automatic driving control processing for the vehicle 10 or driving assistance processing, such as adaptive cruise control (ACC), which includes speed control for automatically controlling the vehicle speed of the vehicle 10. The ECU 17 is also capable of executing PG driving control while the automatic driving control or vehicle speed control is being applied to the vehicle 10.

[0024] In addition, the ECU 17 is an example of a display control device or an audio control device, and controls the display of vehicle speed via the display device 15 or controls audio output via the audio generator 16 while PG driving control is being applied to the vehicle 10.

[0025] The ECU 17 has a communication interface 21, a memory 22, and a processor 23. The communication interface 21, the memory 22, and the processor 23 may be configured as separate circuits, or may be integrated into a single integrated circuit.

[0026] The communication interface 21 has an interface circuit for connecting the ECU 17 to other devices. The communication interface 21 passes signals from the vehicle speed sensor 12, the vehicle exterior sensor 13, and the driver monitor camera 14 to the processor 23. Furthermore, the communication interface 21 outputs a control signal for the powertrain 11 received from the processor 23 to the powertrain 11. Furthermore, the communication interface 21 outputs a speed display signal received from the processor 23 to the display device 15. Furthermore, the communication interface 21 outputs an audio control signal received from the processor 23 to the audio generator 16.

[0027] The memory 22 is an example of a storage unit and includes a volatile semiconductor memory and a non-volatile semiconductor memory. The memory 22 stores various data used in the display control process or the voice control process executed by the processor 23 or generated during the display control process or the voice control process. Furthermore, the memory 22 stores various data used in the automatic driving control or the speed control of the vehicle 10 executed by the processor 23 or generated during the automatic driving control or the speed control.

[0028] The processor 23 has one or more central processing units (CPUs) and their peripheral circuits. The processor 23 may further have other arithmetic circuits such as a logic operation unit, a numerical operation unit, or a graphics processing unit. The processor 23 then executes display control processing or audio control processing. Furthermore, the processor 23 executes automatic driving control or speed control.

[0029] (First embodiment) The following describes the processing of each part of the processor 23 in the first embodiment. In this embodiment, the ECU 17 functions as a display control device, and the processor 23 executes display control processing while the PG driving control is applied to the vehicle 10.

[0030] 2 is a functional block diagram of the processor 23 related to the display control process according to the first embodiment. The processor 23 has a display control unit 31, a determination unit 32, and a driving control unit 33. Each of these units included in the processor 23 is, for example, a functional module realized by a computer program running on the processor 23. Alternatively, each of these units may be a dedicated arithmetic circuit provided in the processor 23.

[0031] While PG driving control is being applied to the vehicle 10, the display control unit 31 sets a display vehicle speed range that is included in the range of the actual vehicle speed of the vehicle 10 under PG driving control (hereinafter referred to as the actual vehicle speed range) but is narrower than the actual vehicle speed range. Then, the display control unit 31 calculates the display vehicle speed within the display vehicle speed range so that the display vehicle speed increases when the vehicle 10 is accelerating and decreases when the vehicle 10 is coasting.

[0032] The actual vehicle speed range is set to include the target vehicle speed. The target vehicle speed is set by the driver via an operating device (not shown) provided in the vehicle cabin. Alternatively, when the vehicle 10 is under autonomous driving control, the target vehicle speed may be set to the speed limit of the road section on which the vehicle 10 is traveling or a speed obtained by subtracting a predetermined offset from the speed limit. In this case, the display control unit 31 identifies the road section on which the vehicle 10 is traveling by referring to map information and the current position of the vehicle 10. The display control unit 31 then uses the speed limit of the identified road section, which is indicated in the map information, to set the target vehicle speed. The map information is pre-stored in the memory 22. Alternatively, the vehicle 10 may have a separate storage device (not shown) for storing map information. The display control unit 31 may set the latest position of the vehicle 10, determined by a satellite positioning system receiver (not shown), such as a GPS receiver, mounted on the vehicle 10, as the current position of the vehicle 10.

[0033] The actual vehicle speed range may be, for example, a speed range of 5% to 10% of the target vehicle speed. The actual vehicle speed range is set so that the target vehicle speed is any speed value within the actual vehicle speed range, such as the center value, lower limit value, or upper limit value of the actual vehicle speed range. The display vehicle speed range may be, for example, a range having a width of 30% to 70% of the actual vehicle speed range and including the target vehicle speed. Furthermore, the display control unit 31 sets the display vehicle speed range when a gaze suppression condition, in which the driver does not gaze at the display device 15, is satisfied to be wider than the display vehicle speed range when the gaze suppression condition is not satisfied. For example, the display control unit 31 sets the display vehicle speed range when the gaze suppression condition is not satisfied to a range having a width of 50% of the actual vehicle speed range, and sets the display vehicle speed range when the gaze suppression condition is satisfied to a range having a width of 70% of the actual vehicle speed range. As a result, in cases where the driver only occasionally checks the displayed vehicle speed, the display control unit 31 can make the displayed vehicle speed closer to the actual vehicle speed, thereby further reducing the sense of discomfort that the driver feels when checking the displayed vehicle speed. Whether or not the gaze suppression condition is satisfied is determined by the determination unit 32. Details of the processing by the determination unit 32 will be described later.

[0034] While the vehicle 10 is under PG driving control by the driving control unit 33, the display control unit 31 calculates a display vehicle speed based on the actual vehicle speed of the vehicle 10 measured by the vehicle speed sensor 12. In this embodiment, the display control unit 31 calculates the difference between the display speed and the target vehicle speed (hereinafter referred to as the display speed residual) by multiplying a value obtained by subtracting the target vehicle speed from the actual vehicle speed by the ratio of the width of the display vehicle speed range to the width of the actual vehicle speed range. The display control unit 31 then calculates the display vehicle speed by adding the target vehicle speed to the display speed residual. For example, it is assumed that the target vehicle speed Vt is 100 km / h, the actual vehicle speed range Rvr is 95 km / h to 105 km / h, and the display vehicle speed range Rvd is 97 km / h to 103 km / h. In this case, if the actual vehicle speed Vr is 105 km / h, the displayed vehicle speed Vd is (105-100)*(103-97) / (105-95)+100=103 km / h. Since the displayed vehicle speed is calculated in this manner, it falls within the displayed vehicle speed range. Furthermore, the higher the actual vehicle speed, the higher the displayed vehicle speed. Therefore, when the vehicle 10 is accelerating, the displayed vehicle speed increases as the actual vehicle speed increases. On the other hand, when the vehicle 10 is coasting, the displayed vehicle speed decreases as the actual vehicle speed decreases.

[0035] Furthermore, when the PG driving control ends, the display control unit 31 corrects the displayed vehicle speed so that it approaches the actual vehicle speed of the vehicle 10 at a rate of change that is equal to or less than a predetermined upper limit rate of change. At this time, the display control unit 31 may increase the upper limit rate of change as the absolute value of the acceleration / deceleration of the vehicle 10 increases. For example, the upper limit rate of change may be a value obtained by multiplying the absolute value of the acceleration / deceleration over the most recent predetermined period by a predetermined constant (e.g., 1.1 to 1.2). This prevents the displayed vehicle speed from changing suddenly compared to the change in the actual vehicle speed when the PG driving control ends. Therefore, the display control unit 31 can prevent the driver from feeling uncomfortable with the change in the displayed vehicle speed immediately after the PG driving control ends.

[0036] 3 is a diagram showing an example of the relationship between changes in actual vehicle speed and changes in displayed vehicle speed when PG driving control is applied to vehicle 10. In FIG. 3, the horizontal axis represents elapsed time, and the vertical axis represents speed per hour. Graph 301 represents the change in actual vehicle speed over time, and graph 302 represents the change in displayed vehicle speed over time. Furthermore, period P represents the period during which PG driving control is applied to vehicle 10.

[0037] 3, during a period P in which PG driving control is applied to the vehicle 10, the actual vehicle speed and the displayed vehicle speed each change within a range that includes the target vehicle speed, and the displayed vehicle speed changes within a displayed vehicle speed range Rvd that is narrower than the actual vehicle speed range Rvr, which is the range in which the actual vehicle speed changes. Furthermore, as the vehicle 10 accelerates and the actual vehicle speed increases, the displayed vehicle speed also increases, and conversely, as the vehicle 10 coasts and the actual vehicle speed decreases, the displayed vehicle speed also decreases. This suppresses flickering of the speed display and reduces the sense of incongruity caused by the difference between the actual vehicle speed and the displayed vehicle speed.

[0038] Furthermore, as shown in graphs 301 and 302, the displayed vehicle speed slowly approaches the actual vehicle speed after the end of period P. In this way, it can be seen that the driver is less likely to feel uncomfortable with the change in the displayed vehicle speed because abrupt changes in the displayed vehicle speed are suppressed.

[0039] The display control unit 31 generates a speed display signal that indicates the displayed vehicle speed, and outputs the speed display signal to the display device 15 via the communication interface 21, thereby causing the display device 15 to display the displayed vehicle speed.

[0040] The determination unit 32 determines, at predetermined intervals (for example, every few seconds to every few minutes), whether the situation around the vehicle 10 or the behavior of the driver of the vehicle 10 satisfies the gaze suppression condition.

[0041] In this embodiment, when the situation around the vehicle 10 corresponds to any of the following situations: bad weather, the number of other vehicles traveling around the vehicle 10 is greater than or equal to a predetermined number, or the vehicle 10 is traveling through a curved section, the judgment unit 32 judges that the gaze suppression condition is satisfied.

[0042] For example, the determination unit 32 determines that the weather around the vehicle 10 is bad if the amount of rain measured by a rainfall sensor (not shown) installed on the vehicle 10 is greater than a predetermined bad weather threshold. Alternatively, the determination unit 32 may determine that the weather around the vehicle 10 is bad if the wiper operation mode of the vehicle 10 is a mode in which the wipers operate continuously. Alternatively, the determination unit 32 may determine whether the weather around the vehicle 10 is bad by inputting an exterior image generated by an exterior camera installed to capture images of the surroundings of the vehicle 10, which is an example of the exterior sensor 13, into a classifier that has been trained in advance to determine whether the weather around the vehicle 10 is bad. In this case, the classifier is configured, for example, by a deep neural network (DNN) having a convolutional neural network (CNN)-type architecture that includes, from the input side, one or more convolutional layers and one or more fully connected layers. Alternatively, the classifier may be configured as a classifier based on a machine learning algorithm other than a DNN, such as a support vector machine. Such a classifier is trained in advance according to a predetermined learning algorithm such as backpropagation using a large number of training images including vehicle exterior images obtained under bad weather conditions and vehicle exterior images obtained under non-bad weather conditions.

[0043] Furthermore, the determination unit 32 inputs the vehicle exterior image into a classifier that has been trained in advance to detect other vehicles in order to count the number of other vehicles traveling around the vehicle 10. The determination unit 32 then counts the number of other vehicles detected by the classifier, and determines that the gaze suppression condition is satisfied if the number of detected other vehicles is equal to or greater than a predetermined number. The classifier for detecting other vehicles is configured as a classifier based on a CNN-type DNN, a DNN with an attention mechanism, or a machine learning algorithm other than DNN, such as AdaBoost. Such a classifier is also trained in advance according to a predetermined learning algorithm using a large number of training images including vehicle exterior images depicting the vehicle to be detected.

[0044] Furthermore, to determine whether the road section on which the vehicle 10 is traveling is a curve section, the determination unit 32 may identify the road section on which the vehicle 10 is traveling by referring to map information and the current position of the vehicle 10, similar to the setting of the target vehicle speed in the display control unit 31. If the identified road section shown in the map information is a curve section, the determination unit 32 determines that the vehicle 10 is traveling on a curve section and the gaze suppression condition is satisfied. Alternatively, the determination unit 32 may detect lane markings by inputting an outside-vehicle image into a classifier pre-trained to detect lane markings, and determine that the vehicle 10 is traveling on a curve section if the curvature of a curve approximation of the detected lane markings is equal to or greater than a predetermined curvature. Note that such a classifier may have a configuration similar to that of a classifier for detecting other vehicles. Alternatively, the classifier for detecting other vehicles may be pre-trained to also detect lane markings.

[0045] Furthermore, regarding the driver's behavior, when the number of times that the driver's line of sight is directed toward the display device 15 is less than or equal to a predetermined number of times in the most recent predetermined period (for example, several tens of seconds to several minutes), the determination unit 32 determines that the attention suppression condition is satisfied. Alternatively, when the ratio of the period during which the driver's line of sight is directed toward a location other than the display device 15 to the predetermined period is equal to or greater than a predetermined threshold, the determination unit 32 may determine that the attention suppression condition is satisfied.

[0046] To detect the driver's gaze direction, the determination unit 32 inputs the driver image into a classifier that has been trained in advance to detect the driver's face from the image, thereby detecting an area in the driver image where the driver's eyes appear (hereinafter referred to as the eye area). As such a classifier, the determination unit 32 may use, for example, a DNN with a CNN-type architecture, a support vector machine, or an AdaBoost classifier. The determination unit 32 may also detect the eye area from the driver image using other methods for detecting the eye area, such as template matching. Furthermore, the determination unit 32 detects a corneal reflection image of a light source (hereinafter referred to as the Purkinje image) and the center of gravity of the pupil (hereinafter simply referred to as the pupil center of gravity) from the eye area. In this case, the determination unit 32 detects the Purkinje image by template matching between a Purkinje image template and the eye area. Similarly, the determination unit 32 may detect the pupil by template matching between a pupil template and the eye area, and determine the center of gravity of the area where the detected pupil appears as the pupil center of gravity. The determination unit 32 then calculates the distance between the Purkinje image and the pupil center of gravity, and detects the driver's gaze direction by referring to a table that indicates the relationship between the distance and the driver's gaze direction. Such a table may be stored in advance in the memory 22. Furthermore, if the detected gaze direction is included in a display device direction range that corresponds to the direction toward the display device 15, the determination unit 32 determines that the driver's gaze direction is toward the display device 15. On the other hand, if the detected gaze direction is outside the display device direction range, the determination unit 32 determines that the driver's gaze direction is not toward the display device 15. The display device direction range may also be stored in advance in the memory 22.

[0047] The determination unit 32 may execute the above process on the latest driver image at predetermined intervals (e.g., 100 msec to 1 sec) to determine the number of times the driver's line of sight is directed toward the display device 15 or the period during which the driver's line of sight is directed away from the display device 15. That is, the determination unit 32 determines, as the period during which the driver's line of sight is directed away from the display device 15, the total of the individual periods from the time when a driver image was generated when the driver's line of sight was outside the display device direction range to the time when a driver image was generated when the driver's line of sight was included within the display device direction range within the most recent predetermined period. Furthermore, the determination unit 32 may determine, as the number of times the driver's line of sight is directed toward the display device 15, the number of times a driver image was generated within the most recent predetermined period, the number of times the driver's line of sight is determined to be included in the display device direction range.

[0048] The determination unit 32 notifies the display control unit 31 of the determination result as to whether or not the attention suppression condition is satisfied.

[0049] The driving control unit 33 executes PG driving control while automatic driving control or speed control is being applied to the vehicle 10. In particular, the driving control unit 33 executes PG driving control when the vehicle 10 can continue driving at a target vehicle speed. Specifically, the driving control unit 33 executes PG driving control when the distance between the vehicle 10 and a preceding vehicle traveling ahead of the vehicle 10 in the vehicle's own lane is greater than a distance threshold at which driving at the target vehicle speed can continue, or when there is no preceding vehicle traveling in the vehicle's own lane, and the vehicle 10 does not need to accelerate or decelerate.

[0050] Therefore, similar to the description of the determination unit 32, the driving control unit 33 may detect other vehicles and lane markings traveling around the vehicle 10 by inputting an exterior image, which is an example of an exterior sensor signal, into a classifier. The driving control unit 33 may then determine the area in the exterior image between the two lane markings closest to the vehicle 10 as the current lane area corresponding to the current lane. Furthermore, the driving control unit 33 may identify, among the detected other vehicles, a vehicle whose bottom edge is included in the current lane area in the exterior image as a leading vehicle. When a leading vehicle is detected, the driving control unit 33 may estimate the distance between the vehicle 10 and the leading vehicle based on parameters such as the mounting position, shooting direction, and angle of view of an exterior camera, which is an example of an exterior sensor 13, and the position of the bottom edge of the leading vehicle in the exterior image. Alternatively, if the vehicle 10 is equipped with a ranging sensor as one of the exterior sensors 13, the driving control unit 33 may determine the distance measured by the ranging sensor in the direction toward the detected leading vehicle as the distance between the vehicle 10 and the leading vehicle.

[0051] Furthermore, the driving control unit 33 may determine whether there is a point within a predetermined distance in the traveling direction of the vehicle 10 where acceleration or deceleration is required, based on map information, the latest position of the vehicle 10 measured by a satellite positioning system receiver (not shown), and the traveling direction of the vehicle 10 measured by a direction sensor (not shown) mounted on the vehicle 10. A point where deceleration is required may be, for example, a point where a stop line is installed or a point where a toll gate is installed on a motorway. If there is no such point where deceleration is required, the driving control unit 33 may determine that there is no need to decelerate the vehicle 10.

[0052] The driving control unit 33 may be configured to execute the PG driving control only when the driver has performed an operation to approve the execution of the PG driving control via an operating device provided in the vehicle cabin.

[0053] When the driving control unit 33 starts executing the PG driving control, it notifies the display control unit 31 to that effect. Then, while the PG driving control is being executed, the driving control unit 33 accelerates the vehicle 10 at a predetermined target acceleration until the actual vehicle speed of the vehicle 10 reaches the upper limit of the actual vehicle speed range. To achieve this, the driving control unit 33 generates a control signal for controlling the powertrain 11 so that the acceleration measured by an acceleration sensor (not shown) mounted on the vehicle 10 approaches the target acceleration. At this time, the driving control unit 33 may generate the control signal according to feedback control such as PID control. Then, the driving control unit 33 outputs the generated control signal to the powertrain 11.

[0054] When the actual vehicle speed of the vehicle 10 measured by the vehicle speed sensor 12 reaches the upper limit of the actual vehicle speed range, the cruise control unit 33 controls the powertrain 11 to coast the vehicle 10. That is, the cruise control unit 33 generates a control signal according to the minimum value of the accelerator opening and outputs the control signal to the powertrain 11. Then, when the speed of the vehicle 10 measured by the vehicle speed sensor 12 reaches the lower limit of the actual vehicle speed range, the cruise control unit 33 controls the powertrain 11 to accelerate the vehicle 10 at a predetermined target acceleration. In this way, while the PG cruise control is being applied, the cruise control unit 33 controls the powertrain 11 so that the actual vehicle speed of the vehicle 10 is within the actual vehicle speed range and the vehicle 10 alternately repeats acceleration cruise and coast cruise.

[0055] The driving control unit 33 terminates the PG driving control when the distance between the preceding vehicle and vehicle 10 in the own lane becomes equal to or less than a distance threshold, or when the distance from the current position of vehicle 10 to a point where deceleration is required becomes equal to or less than a predetermined distance. Alternatively, the driving control unit 33 may terminate the PG driving control when the driver performs an operation to terminate the PG driving control via an operating device, or when the driver depresses the accelerator pedal or brake pedal by a predetermined amount or more. When the driving control unit 33 terminates the execution of the PG driving control, it notifies the display control unit 31 to that effect.

[0056] 4 is an operational flowchart of the display control process according to the first embodiment. While the PG driving control is being executed, the processor 23 executes the display control process in accordance with this operational flowchart.

[0057] The determination unit 32 determines whether the gaze suppression condition is satisfied (step S101). If the gaze suppression condition is satisfied (step S101—Yes), the display control unit 31 sets a relatively wide display vehicle speed range, although it is narrower than the actual vehicle speed range (step S102). On the other hand, if the gaze suppression condition is not satisfied (step S101—No), the display control unit 31 sets a relatively narrow display vehicle speed range, although it is narrower than the actual vehicle speed range (step S103). Then, the display control unit 31 causes the display device 15 to display the display vehicle speed so that the display vehicle speed increases during acceleration and decreases during coasting within the display vehicle speed range (step S104). Then, the processor 23 repeats the processes from step S101 onwards.

[0058] As described above, the display control device according to the first embodiment sets the display vehicle speed range to be narrower than the vehicle's actual vehicle speed range while PG driving control is being applied to the vehicle. Furthermore, this display control device causes the display device to display the displayed vehicle speed so that, within the display vehicle speed range, the displayed vehicle speed increases when the vehicle is accelerating and decreases when the vehicle is coasting. As a result, this display control device changes the displayed vehicle speed in accordance with changes in the actual vehicle speed and more gradually than the actual vehicle speed, thereby reducing flickering of the displayed vehicle speed and alleviating any discomfort felt by the driver.

[0059] According to a modified example, the display control unit 31 may narrow the display vehicle speed range as the number of times the driver's gaze direction is directed toward the display device 15 increases in the most recent predetermined period, or as the ratio of the period during which the driver's gaze direction is directed away from the display device 15 decreases relative to the most recent predetermined period. Furthermore, regardless of whether the gaze suppression condition is satisfied, the display control unit 31 may set the display vehicle speed range based only on the actual vehicle speed range and the target vehicle speed. In this case, the processing of the determination unit 32 may be omitted. Therefore, according to this modified example, the calculation load on the processor 23 is reduced.

[0060] (Second embodiment) Next, the processing of each part of the processor 23 in the second embodiment will be described. In this embodiment, the ECU 17 functions as a voice control device. The processor 23 executes voice control processing while the vehicle 10 is under PG driving control. Differences from the first embodiment will be described below.

[0061] 5 is a functional block diagram of the processor 23 related to voice control processing according to the second embodiment. The processor 23 has a voice control unit 34 and a driving control unit 33. Each of these units in the processor 23 is, for example, a functional module realized by a computer program running on the processor 23. Alternatively, each of these units may be a dedicated arithmetic circuit provided in the processor 23.

[0062] When the voice control unit 34 is notified by the driving control unit 33 that the vehicle has transitioned to coasting while PG driving control is being executed, the voice control unit 34 causes the voice generator 16 to output a pseudo acceleration sound that simulates the sound that is generated in the passenger compartment of the vehicle 10 when the vehicle 10 is accelerating. Acceleration sound data for causing the voice generator 16 to generate the pseudo acceleration sound is stored in advance in the memory 22, and the voice control unit 34 outputs a voice control signal including the acceleration sound data to the voice generator 16 while the vehicle 10 is coasting. Furthermore, when the voice control unit 34 is notified by the driving control unit 33 that the vehicle has transitioned to acceleration while PG driving control is being executed, the voice control unit 34 stops outputting the voice control signal, thereby stopping output of the pseudo acceleration sound from the voice generator 16.

[0063] It should be noted that the louder the noise while driving, the more difficult it becomes for the driver to notice changes in the sound produced by the powertrain 11 of the vehicle 10. Therefore, the sound control unit 34 may reduce the volume of the pseudo acceleration sound output from the sound generator 16 as the noise produced while the vehicle 10 is driving increases.

[0064] The sound control unit 34 may estimate the level of noise while the vehicle 10 is traveling based on the actual speed of the vehicle 10 or the unevenness of the road surface on which the vehicle 10 is traveling. Generally, the faster the actual vehicle speed, the louder the noise while traveling. Therefore, the sound control unit 34 controls the sound generator 16 so that the volume of the pseudo acceleration sound decreases as the actual speed of the vehicle 10 measured by the vehicle speed sensor 12 increases.

[0065] Furthermore, the greater the road surface roughness, the greater the noise generated during driving. The greater the road surface roughness, the greater the short-term fluctuation in the wheel speed measured by the vehicle speed sensor 12 along with the actual vehicle speed. Furthermore, the greater the road surface roughness, the greater the fluctuation range of the acceleration of the vehicle 10 measured by the acceleration sensor. Therefore, the voice control unit 34 performs an FFT on the wheel speed measurements taken over the most recent predetermined period to calculate each frequency component of the wheel speed fluctuation. The voice control unit 34 then controls the voice generator 16 to reduce the volume of the pseudo acceleration sound as the wheel speed fluctuation component at a predetermined frequency (e.g., several hundred Hz) increases. Alternatively, the voice control unit 34 may control the voice generator 16 to reduce the volume of the pseudo acceleration sound as the sum of the absolute values of the acceleration fluctuation amounts between individual sampling points included in the most recent predetermined period increases.

[0066] In this way, in a situation where the driver would not easily notice the volume of the pseudo acceleration sound even if it was reduced, the voice control unit 34 reduces the volume of the pseudo acceleration sound. Therefore, the voice control unit 34 can suppress unnecessary power consumption while making it difficult for the driver to notice the switch between acceleration running and coasting.

[0067] FIG. 6 is a diagram showing an example of the relationship between changes in actual vehicle speed and the output of pseudo acceleration sound when PG driving control is applied to the vehicle 10. In FIG. 6, the horizontal axis represents elapsed time. The vertical axis in the upper graph represents volume, and the vertical axis in the lower graph represents speed. The upper graph 601 represents the change over time in the pseudo acceleration sound output from the sound generator 16, and the lower graph 602 represents the change over time in the actual vehicle speed of the vehicle 10. As shown in FIG. 6, the pseudo acceleration sound is output while the vehicle 10 is decelerating by coasting. Therefore, it becomes difficult to distinguish between sounds generated during acceleration driving and sounds generated during coasting. As a result, it becomes difficult for the driver to notice the switch between acceleration driving and coasting.

[0068] When PS driving control is started, the driving control unit 33 notifies the voice control unit 34 of this. This allows the voice control unit 34 to execute voice control processing while PS driving control is being executed. Furthermore, when the driving control unit 33 transitions from coasting to acceleration driving, it notifies the voice control unit 34 of this. Furthermore, when the driving control unit 33 transitions from acceleration driving to coasting, it notifies the voice control unit 34 of this. Furthermore, when the driving control unit 33 ends PS driving control, it notifies the voice control unit 34 of this.

[0069] 7 is an operational flowchart of the voice control process according to the second embodiment. While the PG driving control is being executed, the processor 23 executes the voice control process according to this operational flowchart.

[0070] The voice control unit 34 determines whether the vehicle 10 is coasting or accelerating based on the notification from the driving control unit 33 (step S201). If the vehicle 10 is coasting (step S201—Yes), the voice control unit 34 sets the volume of the pseudo acceleration sound based on the level of noise when the vehicle 10 is traveling (step S202). Then, the voice control unit 34 causes the voice generator 16 to output the pseudo acceleration sound at the set volume (step S203). On the other hand, if the vehicle 10 is accelerating (step S201—No), the voice control unit 34 causes the voice generator 16 to stop outputting the pseudo acceleration sound (step S204). After step S203 or step S204, the processor 23 repeats the processes from step S201 onwards.

[0071] As described above, the sound control device according to the second embodiment causes the sound generator to output a pseudo acceleration sound during coasting while the PG running control is being applied to the vehicle. Therefore, this sound control device can make it difficult for the driver to notice the switch between acceleration running and coasting.

[0072] According to a modified example, the sound control unit 34 may cause the sound generator 16 to output a pseudo acceleration sound even when the vehicle 10 is accelerating while the PG driving control is being applied to the vehicle 10. In this case, however, it is preferable that the sound control unit 34 controls the sound generator 16 so that the volume of the pseudo acceleration sound when the vehicle 10 is accelerating is lower than the volume of the pseudo acceleration sound when the vehicle 10 is coasting. This makes it difficult for the driver to notice the switch between acceleration and coasting.

[0073] The processor 23 of the ECU 17 may simultaneously execute the display control according to the first embodiment or its modification and the audio control according to the second embodiment or its modification. That is, the processor 23 may include a display control unit 31, a determination unit 32, a driving control unit 33, and an audio control unit 34. That is, while the PS driving control is being applied to the vehicle 10, the processor 23 sets the display vehicle speed range to be narrower than the actual vehicle speed range of the vehicle, and causes the display device 15 to display the displayed vehicle speed so that the displayed vehicle speed increases when the vehicle is accelerating and decreases when the vehicle is coasting. Furthermore, the processor 23 causes the audio generator 16 to output a pseudo acceleration sound while the vehicle 10 is coasting.

[0074] A computer program that realizes the functions of the processor 23 of the ECU 17 according to each of the above embodiments or variations may be provided in a form recorded on a computer-readable portable recording medium such as a semiconductor memory, a magnetic recording medium or an optical recording medium. [Explanation of symbols]

[0075] 10 vehicle, 11 powertrain, 12 vehicle speed sensor, 13 outside sensor, 14 driver monitor camera, 15 display device, 16 voice generator, 17 electronic control unit (ECU), 21 communication interface, 22 memory, 23 processor, 31 display control unit, 32 determination unit, 33 driving control unit, 34 voice control unit

Claims

1. a display control unit that, while the vehicle is under pulse-and-glide travel control so as to repeat acceleration travel and coasting within a predetermined actual vehicle speed range, causes a display device to display the displayed vehicle speed so that the displayed vehicle speed increases when the vehicle is accelerating and decreases when the vehicle is coasting within a displayed vehicle speed range that is included in the actual vehicle speed range and is narrower than the actual vehicle speed range; A display control device having:

2. a determination unit that determines whether a situation around the vehicle or a behavior of a driver of the vehicle satisfies a gaze suppression condition that the driver does not gaze at the display device; The display control device according to claim 1 , wherein the display control unit sets the display vehicle speed range when the gaze suppression condition is satisfied to be wider than the display vehicle speed range when the gaze suppression condition is not satisfied.

3. 3. The display control device according to claim 1, wherein, when the pulse-and-glide driving control ends, the display control unit causes the displayed vehicle speed to approach the actual vehicle speed of the vehicle at a rate of change that is equal to or less than a predetermined upper limit rate of change.

4. a sound control unit that causes a sound generator mounted on the vehicle to output a pseudo acceleration sound that simulates a sound generated when the vehicle is accelerating while the vehicle is in the inertial running state while the vehicle is under pulse-and-glide running control so as to repeat acceleration running and inertial running within a predetermined actual vehicle speed range; A voice control device having:

5. The sound control device according to claim 4 , wherein the sound control unit reduces the volume of the pseudo acceleration sound as the noise generated while the vehicle is running increases.

6. While the vehicle is under pulse-and-glide travel control so as to repeat acceleration travel and coasting within a predetermined actual vehicle speed range, the display device displays the displayed vehicle speed within a display vehicle speed range that is included in the actual vehicle speed range and is narrower than the actual vehicle speed range, so that the displayed vehicle speed increases when the vehicle is accelerating and decreases when the vehicle is coasting. A display control method comprising:

7. While the vehicle is under pulse-and-glide travel control so as to repeat acceleration travel and coasting within a predetermined actual vehicle speed range, the display device displays the displayed vehicle speed within a display vehicle speed range that is included in the actual vehicle speed range and is narrower than the actual vehicle speed range, so that the displayed vehicle speed increases when the vehicle is accelerating and decreases when the vehicle is coasting. A display control computer program for causing a processor mounted on the vehicle to execute the above.

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