JP7823728B2 - Vehicle behavior control device - Google Patents

Description

The present disclosure relates to a vehicle behavior control device that controls vehicle behavior by operating brake devices corresponding to each wheel.

In recent years, vehicles have become known that are capable of implementing brake control, such as braking the vehicle with a predetermined total braking force by operating the brake devices corresponding to each wheel (see Patent Document 1). This brake control can assist the vehicle's travel on steep or slippery slopes while maintaining a predetermined total braking force.

Japanese Patent Application Publication No. 2012-206679

However, with the above configuration, there is a risk that road conditions may cause some wheels to come off the road surface, resulting in a loss of ground contact load. This could result in the total braking force required by the brake control described above not being maintained, resulting in a significant decrease in braking force. This decrease in braking force is undesirable, as it can cause problems such as a feeling of freewheeling to the occupants and unintended speed fluctuations and wheel slippage.

This disclosure has been made to solve these problems, and its purpose is to suppress problems caused by a significant decrease in braking force during brake control.

The vehicle behavior control device disclosed herein comprises: a load-release determination means for determining whether the ground load of each wheel is released based on the operating state of the vehicle during brake control that operates the brake devices of each wheel of the vehicle and generates individual braking forces for each wheel, thereby braking the vehicle with a predetermined total braking force; and an operation addition means for adding, for an insufficient braking force, which is the individual braking force of a wheel determined to be in the load-release state, an operation amount of the brake device corresponding to part or all of the insufficient braking force as an operation amount of one or more of the brake devices corresponding to wheels that are not determined to be in the load-release state.

With this vehicle behavior control system, when some wheels are unloaded, an operating amount corresponding to some or all of the insufficient braking force can be applied to the brake devices corresponding to the other wheels to generate additional individual braking force. In this way, the insufficient braking force caused by the unloaded wheel is compensated for by the other wheels, preventing a significant reduction in the total braking force required by brake control. As a result, problems such as giving occupants a feeling of freewheeling, unintended speed fluctuations, and wheel slippage can be reduced.

This disclosure provides a vehicle behavior control device that can suppress the occurrence of malfunctions caused by the total braking force not being maintained during brake control.

A block diagram showing the overall configuration of a vehicle according to the present disclosure. Flowchart showing the procedure for action addition processing

The following describes an embodiment of the present disclosure based on the drawings.

(1) Overall Configuration As shown in FIG. 1 , the vehicle 1 includes a plurality of wheels 10, a brake device 20 provided on each wheel 10, a drive device 30 that drives each brake device 20, a suspension device 40 that suspends each wheel 10 from the vehicle 1 body, a stroke sensor 50 provided in each suspension device 40, an acceleration sensor 60 that detects the acceleration of the vehicle 1, a vehicle speed sensor 70 that detects the speed of the vehicle 1, and a vehicle behavior control device 80 that is an ECU (Electronic Control Unit) for controlling the operation of the entire vehicle 1.

In this embodiment, an example is shown in which the vehicle 1 has a pair of wheels 10 arranged on the left and right sides at the front and a pair of wheels 10 arranged on the left and right sides at the rear.

The drive unit 30 operates each of the brake units 20 upon receiving a command from the vehicle behavior control device 80. In this embodiment, the brake units 20 and the drive unit 30 are directly or indirectly connected by a hydraulic path, and the drive unit 30 is configured to apply the necessary hydraulic pressure to each of the brake units 20 upon receiving a command from the vehicle behavior control device 80 to generate a predetermined braking force on each wheel 10 in accordance with the command.

The stroke sensor 50 is a sensor that detects the stroke amount of the shock absorber (not shown) located between the vehicle body 1 and the wheel 10 in the suspension device 40.

The acceleration sensor 60 consists of a sensor that detects acceleration in the forward/backward direction of the vehicle 1 and a sensor that detects acceleration in the left/right direction.

(2) Action Addition Processing by Vehicle Behavior Control Device 80 Next, the action addition processing performed by the vehicle behavior control device 80 will be described with reference to Fig. 2. This action addition processing is processing that the vehicle behavior control device 80 executes in accordance with a program stored in the internal memory 71, and is activated on the condition that a brake control processing that is similarly executed in accordance with a program is also activated.

This brake control process is a process for brake control in which the drive unit 30 generates individual braking forces for each wheel 10, thereby braking the vehicle 1 with a predetermined total braking force. In this embodiment, an example of brake control is provided in which hill descent control (HDC) is implemented to assist the vehicle 1 in traveling forward on a steep or slippery slope while maintaining a predetermined total braking force.

When this action addition process is started, first, a standby state is entered until the speed of the vehicle 1 detected by the vehicle speed sensor 70 becomes equal to or lower than a predetermined speed (30 km/h in this embodiment) (s110: NO).

If the speed is equal to or lower than the predetermined speed in step s110 (YES in step s110), it is checked whether or not the ground contact load of each wheel 10 is released (step s120) based on the operating state of the vehicle 1. Here, the stroke amount detected by each stroke sensor 50 is checked, and for the stroke sensor 50 whose stroke amount is the amount reached when the wheel 10 is off the ground, it is determined that the corresponding wheel 10 is in the ground contact state.

In addition to the detection value of the stroke sensor 50, step S120 may also determine that wheels 10 whose ground load has become somewhat small are in a unloaded state. In this case, the ground load of each wheel 10 may be estimated based on the vehicle 1 specifications such as the wheelbase and center of gravity height, the vehicle body inclination angle calculated from the detection value of the acceleration sensor 60, the friction coefficient of the road surface, etc., and the ground load may be determined to be unloaded when it is below a predetermined threshold value.

If, in this step S120, it is determined that none of the wheels 10 is in a weight-free state (step S120: NO), the process returns to step S110.

On the other hand, if at least one of the wheels 10 is determined to be in a weight-released state in step s120 (YES in step s120), the braking force that is insufficient due to the wheels 10 determined to be in a weight-released state (deficient braking force) is calculated (step s130). Here, the sum of the individual braking forces generated at each wheel 10 in the brake control for the wheels 10 determined to be in a weight-released state is calculated as the braking force deficiency.

In addition, when the individual braking forces generated on each wheel 10 during brake control are the same (including within a predetermined threshold range), the insufficient braking force may be calculated based on "(number of wheels 10 determined to be in an unloaded state x individual braking force) / number of wheels 10 not determined to be in an unloaded state."

Next, the ground contact load of each wheel 10 is detected (s140). Here, the ground contact load is detected as an estimated value calculated based on the vehicle 1 specifications such as wheelbase and center of gravity height, the vehicle body inclination angle calculated from the detection value of the acceleration sensor 60, the friction coefficient of the road surface, etc.

Next, the individual braking force required for each wheel 10 to generate the additional braking force calculated in step s130 is set (step s150). Here, for each wheel 10 that is not determined to be in a weight-relieved state, a larger individual braking force is set for the wheel 10 with a larger ground load, the wheel 10 that is located further forward, and depending on its position relative to the wheel 10 in a weight-relieved state.

In this embodiment, the sum of a first coefficient corresponding to the ground load, a second coefficient corresponding to whether it is front or rear, and a third coefficient corresponding to the positional relationship with the wheel 10 in a weight-relieved state is calculated for each wheel 10, and the individual braking force is set according to the ratio of these sums. Here, the first coefficient is set to a larger value for a wheel 10 with a larger ground load detected in s130. The second coefficient is set to a larger value for the wheel 10 at the front in the direction of travel (at the front of the vehicle 1 in this embodiment) than for the wheel 10 at the rear. The third coefficient is set to a larger value for the wheel 10 located on the same left and right side of a pair of wheels 10 determined to be in a weight-relieved state than for the other wheels 10.

In addition, if the wheels 10 that are not determined to be in a weight-released state include both the left and right wheels 10 that make up a pair, the value of at least one of the individual braking forces is adjusted so that the difference between the individual braking forces of the left and right wheels 10 is below a predetermined threshold value.

Then, a command is issued to the drive unit 30 to generate additional braking force to compensate for the lack of braking force for each wheel 10 that has not been determined to be in a weight-released state (s160). Here, each brake unit 20 is instructed via the drive unit 30 to operate at the amount of operation required to generate the additional individual braking force set in s150, and the brake unit 20 that receives this command generates the additional individual braking force.

As a result, the operating amount of the brake device 20 corresponding to part or all of the insufficient braking force is added as an additional operating amount of one or more of the brake devices 20 corresponding to the wheels 10 that are not determined to be in a weight-released state. Thus, after S160, the process returns to S110.

In the action addition processing described above, s110 is a vehicle speed detection means, s120 is a weight release determination means, s140 is a load detection means, and s160 is an action addition means.

The above describes embodiments of the present disclosure, but it goes without saying that the present disclosure is in no way limited to the above embodiments and can take various forms as long as they fall within the technical scope of the present disclosure.

(3) Effects According to the vehicle behavior control device 80 of the above embodiment, when some of the wheels 10 are in a non-weighted state, an operation amount corresponding to part or all of the insufficient braking force can be applied to the brake devices 20 corresponding to the other wheels 10 to generate additional individual braking force. In this way, the insufficient braking force due to the non-weighted wheel 10 is compensated for by the other wheels 10, so that the total braking force required by the brake control is not significantly reduced. As a result, it is possible to suppress problems such as giving the occupant a feeling of freewheeling, unintended speed fluctuations, and wheel 10 slippage.

Furthermore, in the vehicle behavior control device 80, when applying an operating amount corresponding to the insufficient braking force to the brake device 20, the greater the ground load of the wheel 10, the greater the operating amount can be applied to the brake device 20 corresponding to that wheel 10, thereby generating additional individual braking force (s150 in Figure 2). This prevents an unnecessarily large operating amount of the brake device 20 from being allocated to a wheel 10 with a small ground load, thereby preventing the wheel 10 from locking due to the allocation of the operating amount, and ultimately preventing the locked wheel from slipping.

Furthermore, in the vehicle behavior control device 80, when applying an operating amount to the brake device 20 corresponding to the insufficient braking force, the further forward the wheel 10 is positioned in the direction of travel of the vehicle 1, the greater the operating amount is applied to the brake device 20 corresponding to that wheel 10, thereby generating additional individual braking force (s150 in Figure 2). When braking the vehicle 1, inertia comes into play, and the further forward the wheel 10 is in the direction of travel, the greater the ground load tends to be. Therefore, in this embodiment, an unnecessarily large operating amount of the brake device 20 is not allocated to wheels 10 with small ground loads, thereby preventing the wheels 10 from locking due to the allocation of operating amounts, and ultimately preventing the locked wheels 10 from slipping.

The vehicle behavior control device 80 also adjusts the amount of operation of the brake device 20 so that the difference in the individual braking forces generated by the paired left and right wheels 10 is equal to or less than a predetermined threshold value (s150 in Figure 2). If the difference in the individual braking forces generated by the paired left and right wheels 10 becomes too large, problems such as unintended vehicle 1 turning or differential locking of the differential device may occur. In this regard, with this embodiment, the occurrence of the above problems can be prevented by setting an appropriate threshold value.

In addition, the vehicle behavior control device 80 can apply a larger amount of operation to the brake device 20 of the wheel 10 located on the same left-right side of the pair of wheels 10 determined to be in a weight-free state than to the other brake devices 20, thereby generating an additional individual braking force (s150 in Figure 2).This makes it possible to generate another yaw moment in a direction that cancels out the yaw moment caused by the wheel 10 in a weight-free state.

In addition, the vehicle behavior control device 80 can determine whether the wheel 10 is in a weight-free state and generate additional individual braking forces when the vehicle speed is below a predetermined speed.

While various embodiments have been described above, it goes without saying that the present invention is not limited to these examples. It is clear that a person skilled in the art could conceive of various modifications or alterations within the scope of the claims, and it is understood that these naturally fall within the technical scope of the present invention. Furthermore, the components of the above embodiments may be combined in any manner as long as they do not deviate from the spirit of the invention.

This application is based on a Japanese patent application (Patent Application No. 2022-031532) filed on March 2, 2022, the contents of which are incorporated by reference into this application.

1...vehicle, 10...wheel, 20...brake device, 30...drive device, 40...suspension device, 50...stroke sensor, 60...acceleration sensor, 70...vehicle speed sensor, 71...built-in memory, 80...vehicle behavior control device.

Claims (7)

a load-release determination means for determining whether or not the ground contact load of each wheel is released based on the operating state of the vehicle during brake control that operates the brake devices of each wheel of the vehicle to generate individual braking forces for each wheel and thereby brake the vehicle with a predetermined total braking force;
an operation adding means for adding an operation amount of a brake device corresponding to a part or all of the insufficient braking force, which is an individual braking force of a wheel determined to be in the unloaded state, as an operation amount of one or more of the brake devices corresponding to the wheels not determined to be in the unloaded state;
a load detection means for detecting a ground load of each wheel;
Equipped with
The vehicle behavior control device is configured such that the greater the ground load detected by the load detection means for a wheel, the higher the proportion of the amount of operation applied to the brake device of that wheel. a load-release determination means for determining whether or not the ground contact load of each wheel is released based on the operating state of the vehicle during brake control that operates the brake devices of each wheel of the vehicle to generate individual braking forces for each wheel and thereby brake the vehicle with a predetermined total braking force;
an operation adding means for adding an operation amount of a brake device corresponding to a part or all of the insufficient braking force, which is an individual braking force of a wheel determined to be in the unloaded state, as an operation amount of one or more of the brake devices corresponding to the wheels not determined to be in the unloaded state;
Equipped with
The vehicle behavior control device is configured such that the operation adding means increases the proportion of the amount of operation added to the brake device of a wheel disposed further forward in the traveling direction of the vehicle. a load-release determination means for determining whether or not the ground contact load of each wheel is released based on the operating state of the vehicle during brake control that operates the brake devices of each wheel of the vehicle to generate individual braking forces for each wheel and thereby brake the vehicle with a predetermined total braking force;
an operation adding means for adding an operation amount of a brake device corresponding to a part or all of the insufficient braking force, which is an individual braking force of a wheel determined to be in the unloaded state, as an operation amount of one or more of the brake devices corresponding to the wheels not determined to be in the unloaded state;
Equipped with
In the case where the vehicle has a pair of wheels arranged on the left and right sides at the front and a pair of wheels arranged on the left and right sides at the rear,
The operation addition means increases the proportion of the amount of operation added to the brake devices of the wheels located on the same left and right sides of the pair of wheels opposite each other in the front and rear direction that are determined to be in the unloaded state, compared to the other brake devices. In the case where the vehicle has a pair of wheels arranged on the left and right,
the operation adding means adds an amount of operation within a range in which the difference between the individual braking forces generated by the pair of left and right wheels is equal to or less than a predetermined threshold value;
The vehicle behavior control device according to any one of claims 1 to 3 . A vehicle speed detection means for detecting a vehicle speed is provided,
the determination by the unloading determination means and the addition of the operation amount by the operation addition means are performed when the vehicle speed detected by the vehicle speed detection means is equal to or lower than a predetermined speed;
The vehicle behavior control device according to any one of claims 1 to 3 . In the case where the shock absorber of the suspension device corresponding to each wheel is equipped with a stroke sensor that detects the stroke amount,
the unloading determination means determines that the wheel corresponding to the stroke sensor is in the unloaded state when the stroke amount detected by the stroke sensor is the stroke amount reached when the wheel is off the ground.
The vehicle behavior control device according to any one of claims 1 to 3 . a load detection means for detecting a ground load of each wheel;
The unloading determination means determines that the wheel bearing the ground load detected by the load detection means is in the unloading state when the ground load detected by the load detection means is equal to or less than a predetermined threshold value.
The vehicle behavior control device according to any one of claims 1 to 3 .