Patent Description:
As a conventional technique related to a motorcycle (a two-wheeled motor vehicle or a three-wheeled motor vehicle), a technique of assisting with an operation by a rider is available. For example, a driver-assistance system is disclosed in PTL <NUM>. Based on output of a sensor that detects an obstacle present in a travel direction or substantially in the travel direction, the driver-assistance system notifies the rider that the motorcycle inappropriately approaches the obstacle. In PTL <NUM>, a saddled vehicle driven by a rider includes a detection device and a cruise control device for judging the other vehicles detected by the detection device and traveling in a same traffic lane as a preceding vehicle and for automatically controlling of the saddled vehicle to keep a preset intervehicular distance relative to the preceding vehicle. In PTL <NUM> and <NUM>, various vehicles have been proposed which achieve cruise control to also automatically keep the intervehicular distance constant.

By the way, in order to assist with the operation by the rider, it is considered to make the motorcycle execute automatic cruise operation. In the automatic cruise operation, behavior of the motorcycle is controlled such that a travel speed of the motorcycle approximates a speed reference value. In addition, in adaptive cruise operation that is a mode of the automatic cruise operation, a preceding vehicle on a lane where the motorcycle travels is identified as a follow-up vehicle, relative position information between the motorcycle and the follow-up vehicle is acquired, and the behavior of the motorcycle is controlled such that an inter-vehicular distance from the motorcycle to the follow-up vehicle approximates a distance reference value. In the adaptive cruise operation, deceleration that is generated on the motorcycle during automatic deceleration in the operation is restricted to such a magnitude of the deceleration that does not impair comfort of the rider.

The adaptive cruise operation that is executed in wide vehicles (for example, four-wheeled passenger vehicles, four-wheeled trucks, and the like) has already been widespread, and various techniques thereof have already been established. However, a technique of the adaptive cruise operation that is executed in the motorcycle has not been established. For example, the wide vehicle is allowed to change the travel lane relatively freely even during the automatic deceleration when the driver manipulates a steering wheel. Meanwhile, the travel direction of the motorcycle is changed by shifting weight of the rider. In addition, depending on a distribution state of a braking force to front and rear wheels, a force in a direction to lift a vehicle body may act on the motorcycle. Thus, it is relatively difficult to change the travel lane of the motorcycle during the automatic deceleration. In other words, in the adaptive cruise operation of the motorcycle, such a magnitude of the automatic deceleration that causes the rider to feel uncomfortable may have to be permitted. Thus, it is considered that unique control specialized in the adaptive cruise operation of the motorcycle has to be introduced.

The present invention has been made with the above-described problem as the background and therefore obtains a controller and a control method capable of appropriately assisting with an operation by a rider. The present invention also obtains a driver-assistance system including such a controller.

The present invention relates to a driver-assistance system according to claim <NUM>.

The present invention also relates to a driver-assistance system according to claim <NUM>.

The present invention further relates to a control method for a driver-assistance system used for a motorcycle, according to claim <NUM>.

In the present invention, the information relevant to the automatic deceleration generated during the adaptive cruise operation is acquired. In the case where the information satisfies the determination criteria, the notification device executes the notification operation to the rider. That is, even in the case where such a magnitude of the automatic deceleration that causes the rider to feel uncomfortable is generated on the motorcycle during the adaptive cruise operation, it is possible to reduce a negative influence on comfort actually received by the rider by improving predictive performance realized by the notification operation of the notification device. Thus, in the adaptive cruise operation, the motorcycle can be decelerated in various modes. Therefore, it is possible to appropriately assist with the operation by the rider.

A description will hereinafter be made on an example of a controller, a driver-assistance system, and a control method according to the present invention with reference to the drawings.

Note that a term "motorcycle" means a two-wheeled motor vehicle or a three-wheeled motor vehicle among straddle-type vehicles straddled by riders. A configuration and operation, which will be described in the following embodiment, merely constitute one example. The present invention is not limited to the configuration and the operation, which will be described in the following embodiment. For example, the following description will be made on a case where the motorcycle is the two-wheeled motor vehicle. However, the motorcycle may be the three-wheeled motor vehicle. In addition, the following description will be made on a case where the driver-assistance system includes two wheel cylinders. However, the driver-assistance system may include the wheel cylinders in a different number.

In the drawings, the same or similar members or portions will be denoted by the same reference signs. A detailed structure will appropriately be illustrated in a simplified manner or will not be illustrated. If it is desired to indicate a component that is not illustrated in any of the drawings, a broken lead line is used to indicate such a component.

A description will hereinafter be made on an example of a driver-assistance system according to an embodiment and a motorcycle, to which the driver-assistance system is applied.

<FIG> is a view of a configuration of the motorcycle to which the driver-assistance system according to the embodiment of the present invention is applied. <FIG> is a diagram illustrating the driver-assistance system according to the embodiment of the present invention. <FIG> is a system configuration diagram of a main section of the driver-assistance system according to the embodiment of the present invention.

As illustrated in <FIG> and <FIG>, at least a part of a driver-assistance system <NUM> is mounted on a motorcycle <NUM>. The motorcycle <NUM> includes: a trunk <NUM>; a handlebar <NUM> that is held in a freely turnable manner by the trunk <NUM>; a front wheel <NUM> that is held in a freely turnable manner with the handlebar <NUM> by the trunk <NUM>; and a rear wheel <NUM> that is held in a freely rotatable manner by the trunk <NUM>.

The driver-assistance system <NUM> includes: a front brake operation section <NUM>; a front-wheel brake mechanism <NUM> that brakes the front wheel <NUM> in an interlocking manner with at least the front brake operation section <NUM>; a rear brake operation section <NUM>; and a rear-wheel brake mechanism <NUM> that brakes the rear wheel <NUM> in an interlocking manner with at least the rear brake operation section <NUM>.

The front brake operation section <NUM> is provided on the handlebar <NUM> and is operated by a user's hand. The front brake operation section <NUM> is a brake lever, for example. The rear brake operation section <NUM> is provided in a lower portion of the trunk <NUM> and is operated by the user's foot. The rear brake operation section <NUM> is a brake pedal, for example.

Each of the front-wheel brake mechanism <NUM> and the rear-wheel brake mechanism <NUM> includes: a master cylinder <NUM> in which a piston (not illustrated) is installed; a reservoir <NUM> that is attached to the master cylinder <NUM>; a brake caliper <NUM> that is held by the trunk <NUM> and is provided with a brake pad <NUM>; a wheel cylinder <NUM> that is provided in the brake caliper <NUM>; a primary channel <NUM> through which a brake fluid in the master cylinder <NUM> is delivered to the wheel cylinder <NUM>; a secondary channel <NUM> through which the brake fluid in the wheel cylinder <NUM> is released; and a supply channel <NUM> through which the brake fluid in the master cylinder <NUM> is supplied to the secondary channel <NUM>.

An inlet valve (EV) <NUM> is provided in the primary channel <NUM>. The secondary channel <NUM> bypasses a portion of the primary channel <NUM> between the wheel cylinder <NUM> side and the master cylinder <NUM> side from the inlet valve <NUM>. The secondary channel <NUM> is sequentially provided with an outlet valve (AV) <NUM>, an accumulator <NUM>, and a pump <NUM> from an upstream side. Between an end of the primary channel <NUM> on the master cylinder <NUM> side and a portion of the primary channel <NUM> to which a downstream end of the secondary channel <NUM> is connected, a first valve (USV) <NUM> is provided. The supply channel <NUM> communicates between the master cylinder <NUM> and a suction side of the pump <NUM> in the secondary channel <NUM>. A second valve (HSV) <NUM> is provided in the supply channel <NUM>.

The inlet valve <NUM> is an electromagnetic valve that is opened in an unenergized state and closed in an energized state, for example. The outlet valve <NUM> is an electromagnetic valve that is closed in an unenergized state and opened in an energized state, for example. The first valve <NUM> is an electromagnetic valve that is opened in an unenergized state and is closed in an energized state, for example. The second valve <NUM> is an electromagnetic valve that is closed in an unenergized state and is opened in an energized state, for example.

A hydraulic pressure control unit <NUM> is configured to include: members such as the inlet valves <NUM>, the outlet valves <NUM>, the accumulators <NUM>, the pumps <NUM>, the first valves <NUM>, and the second valves <NUM>; a base body <NUM> that is provided with those members and is formed with channels constituting the primary channels <NUM>, the secondary channels <NUM>, and the supply channels <NUM> therein; and a controller (ECU) <NUM>. In the driver-assistance system <NUM>, the hydraulic pressure control unit <NUM> is a unit that has a function of controlling a hydraulic pressure of the brake fluid in the wheel cylinder <NUM>, that is, a braking force on the front wheel <NUM> that is generated by the front-wheel brake mechanism <NUM> and a braking force on the rear wheel <NUM> that is generated by the rear-wheel brake mechanism <NUM>.

The members may collectively be provided in the single base body <NUM> or may separately be provided in the multiple base bodies <NUM>. In addition, the controller <NUM> may be provided as a single unit or may be divided into multiple units. Furthermore, the controller <NUM> may be attached to the base body <NUM> or may be attached to the member other than the base body <NUM>.

As illustrated in <FIG> and <FIG>, the driver-assistance system <NUM> includes a front-wheel rotational frequency sensor <NUM>, a rear-wheel rotational frequency sensor <NUM>, a distance measurement sensor <NUM>, an image sensor <NUM>, and an inertial measurement unit (IMU) <NUM>.

The front-wheel rotational frequency sensor <NUM> detects a rotational frequency of the front wheel <NUM>. The front-wheel rotational frequency sensor <NUM> may detect another physical quantity that can substantially be converted into the rotational frequency of the front wheel <NUM>. The rear-wheel rotational frequency sensor <NUM> detects a rotational frequency of the rear wheel <NUM>. The rear-wheel rotational frequency sensor <NUM> may detect another physical quantity that can substantially be converted into the rotational frequency of the rear wheel <NUM>.

In a state of facing forward, the distance measurement sensor <NUM> is attached to a front portion of the motorcycle <NUM>. The distance measurement sensor <NUM> is a radar, a Lidar, an ultrasonic sensor, a stereovision sensor, or the like, for example, and detects a distance and an orientation from the motorcycle <NUM> to an object ahead.

In a state of facing forward, the image sensor <NUM> is attached to the front portion of the motorcycle <NUM>. The image sensor <NUM> can be any sensor as long as the sensor can learn a travel lane of the motorcycle <NUM> and a positional relationship between the motorcycle <NUM> and a preceding vehicle. Note that the distance measurement sensor <NUM> may have the functions of the image sensor <NUM>, and, in such a case, the image sensor <NUM> may not be provided.

The inertial measurement unit <NUM> includes a three-axis gyroscope sensor and a three-directional acceleration sensor, for example. That is, the inertial measurement unit <NUM> detects an angular velocity and acceleration generated on the traveling motorcycle <NUM>. The inertial measurement unit <NUM> may detect another physical quantity that can substantially be converted into the angular velocity and may detect another physical quantity that can substantially be converted into the acceleration.

As illustrated in <FIG>, the controller <NUM> includes a follow-up vehicle identification section <NUM>, a vehicle position information acquisition section <NUM>, a control amount setting section <NUM>, an execution section <NUM>, relevant information acquisition section <NUM>, and a notification control section <NUM>. The controller <NUM> may partially or entirely be constructed of a microcomputer, a microprocessor unit, or the like, may be constructed of a member in which firmware or the like can be updated, or may be a program module or the like that is executed by a command from a CPU or the like, for example.

The controller <NUM> receives output of the various sensors (a master-cylinder pressure sensor, a wheel-cylinder pressure sensor, the front-wheel rotational frequency sensor <NUM>, the rear-wheel rotational frequency sensor <NUM>, the distance measurement sensor <NUM>, the image sensor <NUM>, the inertial measurement unit <NUM>, and the like). In addition, the controller <NUM> outputs a signal to each component of the driver-assistance system <NUM> (each component of the hydraulic pressure control unit <NUM>, each component used to control engine output, and the like), so as to control behavior of the motorcycle <NUM>.

More specifically, in normal brake control, the controller <NUM> controls the inlet valves <NUM>, the outlet valves <NUM>, the first valves <NUM>, and the second valves <NUM> as follows. The normal brake control is control to generate the braking force, an amount of which corresponds to an operation amount of the front brake operation section <NUM>, on the front wheel <NUM> when the front brake operation section <NUM> is operated. In addition, the normal brake control is control to generate the braking force, the amount of which corresponds to an operation amount of the rear brake operation section <NUM>, on the rear wheel <NUM> when the rear brake operation section <NUM> is operated.

In the normal brake control, the controller <NUM> opens the inlet valves <NUM>, closes the outlet valves <NUM>, opens the first valves <NUM>, and closes the second valves <NUM>. When the front brake operation section <NUM> is operated in such a state, in the front-wheel brake mechanism <NUM>, the piston (not illustrated) in the master cylinder <NUM> is pressed to increase the hydraulic pressure of the brake fluid in the wheel cylinder <NUM>, and the brake pad <NUM>, which is provided in the brake caliper <NUM>, is pressed against a rotor 3a of the front wheel <NUM>. In this way, the braking force is generated on the front wheel <NUM>, and the front wheel <NUM> is thereby braked. Meanwhile, when the rear brake operation section <NUM> is operated, in the rear-wheel brake mechanism <NUM>, the piston (not illustrated) in the master cylinder <NUM> is pressed to increase the hydraulic pressure of the brake fluid in the wheel cylinder <NUM>, and the brake pad <NUM>, which is provided in the brake caliper <NUM>, is pressed against a rotor 4a of the rear wheel <NUM>. In this way, the braking force is generated on the rear wheel <NUM>, and the rear wheel <NUM> is thereby braked.

The controller <NUM> can execute adaptive cruise operation. The adaptive cruise operation is a mode of automatic cruise operation. In the automatic cruise operation, the engine output and the braking forces generated on the wheels (the front wheel <NUM> and the rear wheel <NUM>) are controlled such that a travel speed of the motorcycle <NUM> approximates a speed reference value. In this way, the motorcycle <NUM> is automatically accelerated or decelerated. The adaptive cruise operation is executed when the preceding vehicle is identified as a follow-up vehicle during the execution of the automatic cruise operation. In the adaptive cruise operation, the engine output and the braking forces generated on the wheels (the front wheel <NUM> and the rear wheel <NUM>) are controlled such that an inter-vehicular distance from the motorcycle <NUM> to the follow-up vehicle approximates a distance reference value. In this way, the motorcycle <NUM> is automatically accelerated or decelerated. In the adaptive cruise operation, upper limit values are set for target acceleration of the motorcycle <NUM>, which is set at the time of the automatic acceleration, and target deceleration of the motorcycle <NUM>, which is set at the time of the automatic deceleration. Each of those upper limit values is preferably a value at which comfort of the rider is not significantly impaired.

The follow-up vehicle identification section <NUM> identifies the follow-up vehicle on the basis of the output of the distance measurement sensor <NUM> and the image sensor <NUM>. More specifically, of the preceding vehicles located within a detection range of the distance measurement sensor <NUM>, the preceding vehicle that is located on the travel lane of the motorcycle <NUM> and has the shortest distance from the motorcycle <NUM> is identified as the follow-up vehicle.

Based on the output of the distance measurement sensor <NUM>, the vehicle position information acquisition section <NUM> acquires vehicle position information that is relative position information of the follow-up vehicle to the traveling motorcycle <NUM>. More specifically, the vehicle position information acquisition section <NUM> acquires, as the vehicle position information, the inter-vehicular distance between the motorcycle <NUM> and the follow-up vehicle.

The control amount setting section <NUM> sets a control amount in the adaptive cruise operation on the basis of the vehicle position information acquired by the vehicle position information acquisition section <NUM> and the output of the front-wheel rotational frequency sensor <NUM> and the rear-wheel rotational frequency sensor <NUM>. More specifically, the control amount setting section <NUM> sets such a control amount that the inter-vehicular distance between the motorcycle <NUM> and the follow-up vehicle in a travel direction of the motorcycle <NUM> approximates the distance reference value. As the distance from the motorcycle <NUM> to the follow-up vehicle, the distance reference value is set to a value with which safety of the rider can be secured. In addition, the control amount setting section <NUM> sets such a control amount that the travel speed of the motorcycle <NUM> does not exceed the speed reference value. For example, the speed reference value can appropriately be set by the rider. In the case where the follow-up vehicle is not identified by the follow-up vehicle identification section <NUM>, the control amount setting section <NUM> sets such a control amount that the travel speed of the motorcycle <NUM> approximates the speed reference value.

The execution section <NUM> executes the adaptive cruise operation that corresponds to the control amount set by the control amount setting section <NUM>. For example, in the adaptive cruise operation, the execution section <NUM> controls the components of the driver-assistance system <NUM> to increase the engine output, and thereby executes the automatic acceleration. In addition, for example, in the adaptive cruise operation, the execution section <NUM> controls the components of the driver-assistance system <NUM> to increase the braking forces generated on the wheels (the front wheel <NUM> and the rear wheel <NUM>), and thereby executes the automatic deceleration. When executing the automatic deceleration, the execution section <NUM> operates the inlet valves <NUM>, the outlet valves <NUM>, the first valves, <NUM>, the second valves <NUM>, and the pumps <NUM> with the control amount set by the control amount setting section <NUM>, so as to control the deceleration generated on the motorcycle <NUM>.

For example, the controller <NUM> controls the inlet valves <NUM>, the outlet valves <NUM>, the first valves <NUM>, the second valves <NUM>, and the pumps <NUM> as follows. In order to generate the braking force on the front wheel <NUM>, the controller <NUM> drives the pump <NUM> in a state where the inlet valve <NUM> is opened, the outlet valve <NUM> is closed, the first valve <NUM> is closed, and the second valve <NUM> is opened in the front-wheel brake mechanism <NUM>. In addition, in order to generate the braking force on the rear wheel <NUM>, the controller <NUM> drives the pump <NUM> in a state where the inlet valve <NUM> is opened, the outlet valve <NUM> is closed, the first valve <NUM> is closed, and the second valve <NUM> is opened in the rear-wheel brake mechanism <NUM>.

During the adaptive cruise operation, the controller <NUM> can execute notification operation to the rider by outputting a signal to a notification device <NUM> in accordance with the output of the various sensors (the master-cylinder pressure sensor, the wheel-cylinder pressure sensor, the front-wheel rotational frequency sensor <NUM>, the rear-wheel rotational frequency sensor <NUM>, the distance measurement sensor <NUM>, the image sensor <NUM>, the inertial measurement unit <NUM>, and the like).

The relevant information acquisition section <NUM> acquires information relevant to the automatic deceleration that is generated during the adaptive cruise operation. The information relevant to the automatic deceleration may be information relevant to the automatic deceleration generated at the time point or may be information relevant to the automatic deceleration to be generated in the future.

The notification control section <NUM> determines whether the information relevant to the automatic deceleration, which is acquired by the relevant information acquisition section <NUM>, satisfies a determination criteria. If the determination criteria is satisfied, the notification control section <NUM> outputs a signal that makes the notification device <NUM> execute the notification operation.

According to the invention, the information relevant to the automatic deceleration includes the deceleration of the motorcycle <NUM> in the automatic deceleration generated during the adaptive cruise operation. The relevant information acquisition section <NUM> may acquire the deceleration generated at the time point on the basis of the output of the front-wheel rotational frequency sensor <NUM> and the rear-wheel rotational frequency sensor <NUM>, or may acquire the deceleration to be generated in the future on the basis of the control amount set by the control amount setting section <NUM>. In the case where the deceleration is higher than a reference value, the notification control section <NUM> outputs the signal that makes the notification device <NUM> execute the notification operation. Needless to say, the reference value is lower than an upper limit value of the target deceleration of the motorcycle <NUM>, which is set at the time of the automatic deceleration. In addition, in the case where a change amount of the deceleration is larger than a reference value, the notification control section <NUM> outputs the signal that makes the notification device <NUM> execute the notification operation.

According to the invention, the information relevant to the automatic deceleration includes a pitch angle or a pitch angular velocity of the motorcycle <NUM> in the automatic deceleration generated during the adaptive cruise operation. The relevant information acquisition section <NUM> preferably acquires the pitch angle or the pitch angular velocity generated at the time point on the basis of the output of the inertial measurement unit <NUM>. In the case where the pitch angle or the pitch angular velocity is larger than a reference value, the notification control section <NUM> outputs the signal that makes the notification device <NUM> execute the notification operation. Alternatively, in the case where a change amount of the pitch angle or the pitch angular velocity is larger than a reference value, the notification control section <NUM> outputs the signal that makes the notification device <NUM> execute the notification operation.

According to the invention, the information relevant to the automatic deceleration includes peripheral environment information of the motorcycle <NUM> that influences the automatic deceleration generated during the adaptive cruise operation. The relevant information acquisition section <NUM> acquires a lit state of a brake lamp of the preceding vehicle on the basis of the output of the image sensor <NUM>. In the case where the brake lamp of the preceding vehicle is lit, the notification control section <NUM> outputs the signal that makes the notification device <NUM> execute the notification operation. Alternatively, In the case where lighting of the brake lamp of the preceding vehicle continues for reference duration or longer, the notification control section <NUM> outputs the signal that makes the notification device <NUM> execute the notification operation.

The notification device <NUM> may notify the rider by sound, may notify the rider by a display, may notify the rider by vibrations, or may notify the rider by a combination of any of those. That is, the notification device <NUM> may execute the notification operation that does not exert an external force on the rider, or may execute the notification operation that exerts the external force on the rider. More specifically, the notification device <NUM> is a speaker, a display, a lamp, a vibrator, or the like. In addition, the notification device <NUM> may be provided on the motorcycle <NUM> or may be provided in an accessory such as a helmet that is associated with the motorcycle <NUM>. Furthermore, the notification device <NUM> may be constructed of a single output device or may be constructed of multiple output devices of the same type or different types. The multiple output devices may be provided integrally or may be provided separately.

<FIG> is a flowchart illustrating operation of the controller in the driver-assistance system according to the embodiment of the present invention.

The controller <NUM> repeatedly executes processing in <FIG> during the adaptive cruise operation.

In step S1, the control amount setting section <NUM> of the controller <NUM> sets the control amount for generating the desired automatic acceleration or the desired automatic deceleration on the motorcycle <NUM>.

In step S2, the relevant information acquisition section <NUM> of the controller <NUM> acquires the information relevant to the automatic deceleration generated on the motorcycle <NUM>.

In step S3, the notification control section <NUM> of the controller <NUM> determines whether the information relevant to the automatic deceleration, which is acquired in step S2, satisfies the determination criteria. If it is determined YES in step S3, in step S4, the notification control section <NUM> outputs the signal that makes the notification device <NUM> execute the notification operation.

In step S5, the execution section <NUM> of the controller <NUM> operates each of the components of the driver-assistance system <NUM> with the control amount set in step S1, and makes the motorcycle <NUM> execute the automatic acceleration or the automatic deceleration.

A description will be made on effects of the driver-assistance system according to the embodiment.

In the driver-assistance system <NUM>, the controller <NUM> includes: the relevant information acquisition section <NUM> that acquires the information relevant to the automatic deceleration generated during the adaptive cruise operation; and the notification control section <NUM> that makes the notification device <NUM> execute the notification operation to the rider in the case where the information relevant to the automatic deceleration, which is acquired by the relevant information acquisition section <NUM>, satisfies the determination criteria. That is, even in the case where such a magnitude of the automatic deceleration that causes the rider to feel uncomfortable is generated on the motorcycle <NUM> during the adaptive cruise operation, it is possible to reduce the negative influence on the comfort actually received by the rider by improving predictive performance realized by the notification operation of the notification device <NUM>. Thus, in the adaptive cruise operation, the motorcycle <NUM> can be decelerated in various modes. Therefore, it is possible to appropriately assist with the operation by the rider.

According to the invention, in the driver-assistance system <NUM>, the information relevant to the automatic deceleration includes the deceleration of the motorcycle <NUM> in the automatic deceleration generated during the adaptive cruise operation. For example, in the case where the deceleration is higher than the reference value, the notification control section <NUM> preferably makes the notification device <NUM> execute the notification operation. Alternatively, for example, in the case where the change amount of the deceleration is larger than the reference value, the notification control section <NUM> preferably makes the notification device <NUM> execute the notification operation. With such a configuration, even in the case where the behavior of the motorcycle <NUM> has to be controlled by such automatic deceleration that generates the deceleration or the change amount of the deceleration with which the rider feels uncomfortable during the adaptive cruise operation, the rider is urged to be prepared in advance. Therefore, it is possible to reduce the negative influence on the comfort actually received by the rider.

According to the invention, in the driver-assistance system <NUM>, the information relevant to the automatic deceleration includes the pitch angle or the pitch angular velocity of the motorcycle <NUM> in the automatic deceleration generated during the adaptive cruise operation. For example, in the case where the pitch angle or the pitch angular velocity is larger than the reference value, the notification control section <NUM> preferably makes the notification device <NUM> execute the notification operation. Alternatively, for example, in the case where the change amount of the pitch angle or the pitch angular velocity is larger than the reference value, the notification control section <NUM> preferably makes the notification device <NUM> execute the notification operation. With such a configuration, even in the case where the behavior of the motorcycle <NUM> has to be controlled by such automatic deceleration that generates one of the pitch angle and the pitch angular velocity or one of the change amount of the pitch angle and the change amount of the pitch angular velocity with which the rider feels uncomfortable during the adaptive cruise operation, the rider is urged to be prepared in advance. Therefore, it is possible to reduce the negative influence on the comfort actually received by the rider.

According to the invention, in the driver-assistance system <NUM>, the information relevant to the automatic deceleration includes the peripheral environment information of the motorcycle <NUM> that influences the automatic deceleration generated during the adaptive cruise operation. The peripheral environment information includes the information on the lit state of the brake lamp of the preceding vehicle. With such a configuration, even in the case where the behavior of the motorcycle <NUM> has to be controlled by such automatic deceleration that causes the rider to feel uncomfortable during the adaptive cruise operation, the rider recognizes the need for the automatic deceleration and is urged to be prepared in advance. Therefore, it is possible to reduce the negative influence on the comfort actually received by the rider.

Preferably, in the driver-assistance system <NUM>, the notification operation does not exert the external force on the rider. With such a configuration, it is possible to suppress the notification operation from having the negative influence on the operation by the rider.

Preferably, in the driver-assistance system <NUM>, the notification operation is the operation that exerts the external force on the rider. With such a configuration, the rider is reliably notified.

Claim 1:
A driver-assistance system (<NUM>) used for a motorcycle (<NUM>), the driver-assistance system (<NUM>) comprising:
an electronic processor configured to
set a control amount in an adaptive cruise operation in which the motorcycle (<NUM>) travels at a speed corresponding to an inter-vehicular distance from said motorcycle (<NUM>) to a preceding vehicle;
make the motorcycle (<NUM>) execute the adaptive cruise operation corresponding to the control amount;
acquire information relevant to automatic deceleration generated during the adaptive cruise operation, the information including an automatic deceleration of the motorcycle (<NUM>), a pitch angle of the motorcycle (<NUM>), a pitch angular velocity of the motorcycle (<NUM>), and a lit state of a brake lamp of the preceding vehicle; and
make a notification device (<NUM>) execute a notification operation to a rider in the case where the information satisfies a determination criteria during the adaptive cruise operation.