Method for controlling a vehicle with a driver assistance system having a brake assistance function

Abstract

Method for controlling a vehicle with a driver assistance system having a brake assistance function and with an environment sensor unit generating environment data, in which the brake pedal position or the brake pedal actuation force of a brake pedal actuated by a driver is detected by means of a brake pedal position sensor or a brake pedal actuation force sensor and evaluated by the driver assistance system, wherein - when the driver operates the brake pedal, a brake pedal position or a brake pedal actuation force is detected that is less than a predetermined threshold value, the driver assistance system generates a braking torque request depending on the dynamic driving state of the vehicle and the environmental data, and - if the specified threshold value is exceeded by the driver's brake pedal operation with regard to the brake pedal position or the brake pedal operation force, the brake assistance function is deactivated, and - in the event of a brake pedal actuation by the driver with a brake pedal position or a brake pedal actuation force that is less than the predetermined threshold value, the driver assistance system generates a second modified braking request that differs from a first braking request that the driver assistance system generates without brake actuation by the driver.

Description

[0001] The invention relates to a method for controlling a vehicle with a driver assistance system having a brake assistance function according to the preamble of patent claim 1.

[0002] Driver assistance systems that support the driver in driving are now widespread in modern vehicles and are constantly being developed further. Examples include Adaptive Cruise Control (ACC), Blind Spot Detection (BSD), Emergency Brake Assist (EBA), and Lane Departure Warning (LDW). Semi-automatic and fully automatic parking systems are also already available.

[0003] Assistance functions that control longitudinal dynamics, such as those in an ACC system, are usually switched on and off as vehicle control elements via the brake pedal and the accelerator pedal (also called gas pedal), thus representing an HMI interface between the driver and the vehicle or the driver assistance system. The driver assistance system detects brake or accelerator pedal actuations by the driver using fixed or situation-adapted detection thresholds.

[0004] It is also known that emergency braking interventions in an emergency braking system can be overridden by significantly depressing the accelerator pedal. In an ACC system, ACC interventions are suppressed by depressing the accelerator pedal.

[0005] Electronic braking systems, so-called brake-by-wire systems, are also known. In these systems, the driver simply operates a so-called simulator, which recreates the brake pedal feel familiar from conventional braking systems. The hydraulic pressures required for braking are generated by an electro-hydraulic pump. Furthermore, so-called electronic accelerator pedals, also called pedal position sensors, are already state of the art and usually feature a kick-down function for automatic transmissions.

[0006] The disadvantage of such systems in connection with driver assistance systems is that the driver, especially in autonomous or semi-autonomous driving with such driver assistance systems, is increasingly decoupled from the vehicle and thus has less control or influence on the driving dynamics of the vehicle.

[0007] For example, DE 10 2006 039 121 A1 describes a driver assistance system with an emergency braking function in which automatic braking can only be overridden, i.e. deactivated, by the driver if the brake pressure generated by the driver by actuating the brake pedal, which corresponds, for example, to a specific brake pedal position, exceeds a predefined proportion or a predetermined multiple of the brake pressure requested by the emergency braking function. The aim of this is to ensure that the driver, when taking over the vehicle, brakes as hard as the emergency braking function, depending on the hazardous situation. Otherwise, the emergency braking function remains active as long as the driver requests a lower braking torque based on the brake pedal position than the braking torque determined by the emergency braking assistant would be required, for example to prevent a collision with a vehicle ahead.

[0008] Based on this, the invention is based on the object of improving the method mentioned at the outset with regard to the operation of the driver assistance system in order to thereby increase operating comfort.

[0009] This problem is solved by a method having the features of patent claim 1.

[0010] This method for controlling a vehicle with a driver assistance system having a brake assistance function and an environment sensor unit generating environment data, in which the brake pedal position or the brake pedal actuation force of a brake pedal actuated by a driver is detected by means of a brake pedal position sensor or a brake pedal actuation force sensor and evaluated by the driver assistance system, is characterized according to the invention in that - when the driver operates the brake pedal, a brake pedal position or a brake pedal actuation force is detected that is less than a predetermined threshold value, the driver assistance system generates a braking torque request depending on the dynamic driving state of the vehicle and the environmental data, and - if the specified threshold value is exceeded by the driver's brake pedal operation with regard to the brake pedal position or the brake pedal operation force, the brake assistance function is deactivated.

[0011] With such a method according to the invention, the advantage arises that, for example, not only does an automatic intervention in the braking system take place in a dangerous situation detected by the driver assistance system, but that the driver can also use the braking assistance function and thus the "capabilities" of the driver assistance system for "normal" driving situations and thus overall a significantly more comfortable operation and influence of the driver assistance system is achieved and ultimately also a more relaxed driving is made possible for the driver.

[0012] Furthermore, this method according to the invention offers the advantage that the known braking concepts can continue to be used, and the method according to the invention and these braking concepts cannot block or interfere with each other. The most important advantage of the method according to the invention is that the available environmental information can also be used during normal driving by activating the driver assistance system.

[0013] In the method according to the invention, the brake pedal can be actuated by the driver up to a threshold value S or S' with respect to the brake pedal position or the brake pedal actuation force, i.e. between a value 0 and the value S or S' of the threshold value, whereby the brake assistance function is simultaneously activated and thus the braking torque requested by the brake pedal position or the brake pedal actuation force generated by the driver is not generated, but rather a braking torque request is generated by the driver assistance system based on the current environmental data, i.e. the current traffic situation. Thus, by light braking, i.e. by only slightly actuating the brake pedal, the brake assistance function of the driver assistance system is activated, which then in turn generates a braking torque request adapted to the current traffic situation.

[0014] For example, even if a brake pedal actuation by the driver indicates a brake pressure that is higher than the one determined by the driver assistance system as appropriate based on the current environmental data, the driver assistance system will still only output the brake torque request that generates this required brake pressure. Therefore, if a driver brakes too harshly when approaching a stationary or preceding vehicle, for example, as part of an ACC system, the brake pressure determined by the driver assistance system as appropriate based on the current traffic situation will still be requested, but only as long as the driver has not yet depressed the brake pedal beyond the threshold S or S'.

[0015] According to the invention, if the driver applies the brake pedal with a brake pedal position or a brake pedal application force that is less than the predetermined threshold value, the driver assistance system generates a second modified braking request that differs from a first braking request generated by the driver assistance system without the driver applying the brake. The background to this embodiment of the invention is that the driver obviously desires earlier or stronger braking. This desire is taken into account by the driver assistance system issuing a modified braking request that is based on the traffic situation. Braking is initiated, for example, earlier but less forcefully, or has a shorter braking duration, or is carried out in a weaker manner over the further course of the braking process.A further embodiment of the invention provides that an increased braking request is issued upon brake application. This case is particularly intended if the driver operates the brake pedal during an already initiated automatic braking. To compensate for the initially increased braking request, the modified braking action can be shorter and, alternatively or additionally, can be weakened in its subsequent course compared to an automatic braking action without the driver applying the brakes.

[0016] The threshold S or S' can be the value in % of the maximum brake pedal position or the maximum brake pedal actuation force.

[0017] If the driver presses the brake pedal beyond this threshold S or S', i.e., into a range where the brake pedal position is above the threshold S or the generated brake pedal actuation force is above the threshold S', the brake assistance function of the driver assistance system is overridden, i.e., a "kick-down" function is executed. This overrides the system requirement of the driver assistance system, so that the driver once again experiences unaffected brake pedal behavior.

[0018] The process of this "kick-down" function can be displayed to the driver via a display unit, allowing the driver to adapt more quickly to the changed braking behavior, which is no longer supported by the driver assistance system. This also allows the driver to better distinguish between malfunctions of the driver assistance system and intended functions.

[0019] In this method according to the invention, the driver's actuation can also be carried out only briefly, whereby even in such a case the driver assistance system generates a braking torque request according to the current traffic situation.

[0020] When a driver is driving in normal city traffic and wants to stop behind a vehicle in front, they only need to apply the brake pedal slightly, so that the threshold S or S' is not reached, and the braking performance is adjusted based on the current environmental data. The deceleration, i.e., the braking force curve, is therefore adjusted so that the vehicle decelerates evenly and, just before coming to a standstill, the deceleration is reduced to ensure a comfortable stop.

[0021] In line with the further development, this procedure allows the deceleration curve of a vehicle with a hybrid or electric drive to be adapted to the available or retrievable regenerative deceleration or braking power. If the available regenerative braking power corresponds to the braking power indicated or requested by the braking torque request, the braking force curve can be adapted to this available regenerative braking power.

[0022] This ensures optimal use of the regenerative braking system's power. For example, when braking for a vehicle in front, braking can be performed purely electrically if the driver assistance system detects that the regenerative braking power is sufficient.

[0023] Furthermore, in a vehicle with a hybrid or electric drive, it is of course possible that the braking power indicated by the braking torque request is initially provided by regenerative braking, in order to then generate the remaining braking power by an engine brake of the hybrid vehicle or, for example, by an electro-hydraulic brake of the electric vehicle.

[0024] If a driver brakes his vehicle in slow-moving traffic and does not press the brake pedal down to the threshold value S or S', the driver assistance system optimises the deceleration, ie the braking force curve in the sense of an optimal traffic flow similar to an ACC control, so that the most harmonious deceleration curve possible is achieved over time.

[0025] If, for example, a vehicle rear-ends another vehicle, the adaptive cruise control of an ACC system as a driver assistance system or automatic braking by the brake assist system as a driver assistance system can be activated by briefly applying the brake, even if the critical thresholds of the ACC system or brake assist system regarding the distance to the vehicle ahead have not yet been exceeded, and braking would therefore normally occur much later and more forcefully. This allows the driver to intuitively influence the behavior of the driver assistance system, such as an ACC system or brake assist system, in order to better "flow" with traffic.

[0026] If the vehicle also has environmental sensors that can detect the neighboring lanes of the vehicle, in an ACC system as a driver assistance system, the braking intervention initiated by the driver according to the invention, which therefore does not constitute an ACC intervention, can be aborted by briefly pressing the accelerator pedal and the driver can automatically accelerate the vehicle to the speed at which it was overtaken by vehicles in one of the neighboring lanes in order to simplify a lane change.

[0027] This allows the driver to confirm a target for an ACC object within the context of an ACC system as a driver assistance system, or for a collision-threatening object within the context of an emergency braking system. This also makes it possible to react to stationary obstacles with ACC control at significantly higher speeds than would be possible based on sensors alone, for example, by merging camera and radar sensors.

[0028] In order to avoid a temporary drop in braking performance when the driver exceeds the threshold S or S' using the brake pedal, since a different brake pressure may have been generated with the brake torque request of the driver assistance system before these thresholds S or S' were exceeded, the relationship between braking distance, braking force and brake pressure is adjusted accordingly in order to obtain a continuous braking characteristic.

[0029] In one embodiment of the invention, the threshold value is determined according to the end of the free travel of the brake pedal.

[0030] Ideally, the range in which the driver assistance system automatically adjusts the brake pressure to the current traffic situation is the range in which the play in the braking system is overcome, the so-called free travel. This provides a haptic pressure point for the brake pedal's "kick-down" function, i.e., when the brake pedal is overpressed beyond the threshold S or S'. Especially when using a simulator as the brake pedal, a pressure point is created by simulating the brake booster valve.

[0031] Instead of the free travel, the threshold value S or S' can be used to define a comfort braking range, as the range in which an automatic adjustment of the brake pressure is carried out by the driver assistance system.

[0032] According to an advantageous development of the invention, when negotiating a curve, a braking torque request optimized with regard to the driving dynamics state of the vehicle when negotiating the curve is generated by the driver assistance system.

[0033] If a driver brakes before or in a bend and does not press the brake pedal all the way to the threshold S or S', i.e. not to the "kick-down" point, the driver assistance system optimises the deceleration, i.e. the braking force curve, and thus generates a braking torque request so that the maximum speed for the bend is not exceeded, and in particular the vehicle's dynamic limits are not exceeded.

[0034] This allows the driver to request the brake assistance function of the driver assistance system when cornering by gently braking or by lightly tapping the brake pedal. The system then requests brake pressure depending on the cornering situation and the vehicle's dynamic driving condition, so that the driver can steer the vehicle safely through the corner.

[0035] The information about entering the curve or about to enter the curve is determined from the surrounding data by the driver assistance system or recognized based on digital map data provided by the driver assistance system.

[0036] Furthermore, according to the further development, traffic sign recognition information is provided to the driver assistance system from the surrounding data. Upon detection of a speed-limiting traffic sign, a braking torque request adapted to the speed limit indicated by the traffic sign is generated when the brake pedal is depressed below the threshold S or S'. Even in this situation, the driver can request the brake assistance function by gently braking or by tapping the brake pedal to have the vehicle decelerate or accelerate according to the detected speed limit.

[0037] It is particularly advantageous if the environment sensor unit also has sensors that monitor the area to the rear of the vehicle, so that when the driver assistance system generates the braking torque request when the brake pedal is actuated below the threshold S or S', these rear environment data of the vehicle can also be taken into account.

[0038] If, for example, a driver is driving in normal city traffic and wants to come to a stop behind a vehicle in front and to do so only slightly applies the brakes without the threshold S or S' being reached with regard to the brake pedal position or the brake pedal application force, the driver assistance system adjusts the braking performance on the basis of the current environmental data from the environmental sensors. The deceleration, i.e. the braking force curve, is therefore set so that the vehicle is decelerated as evenly as possible. If it is also detected that another vehicle is approaching quickly from behind, the braking torque request is generated so that the vehicle comes to a stop as close as possible behind the vehicle in front in order to give the vehicle approaching from behind as much braking distance as possible.

[0039] In addition to the area behind the vehicle, the environmental data of the lanes adjacent to the lane in which the vehicle is traveling can also be taken into account when generating the braking torque request.

[0040] It is particularly advantageous to combine the method according to the invention with an ACC system as a driver assistance system.

[0041] For example, if a driver is driving on a motorway in ACC mode of an ACC system in the right lane and approaches a truck from behind, while the vehicle is being overtaken by other vehicles in the left lane. If the driver brakes only slightly without reaching the threshold S or S' with regard to the brake pedal position or brake pedal application force, the vehicle will decelerate early on in accordance with the speed of the truck due to the driver's request for the brake assistance function. If the driver presses the accelerator pedal, the brake assistance function is initially deactivated and the ACC system automatically accelerates the vehicle to the speed of the vehicles in the adjacent left lane if further vehicles are detected from behind. If no following vehicles can be detected, the vehicle will simply accelerate to the old set speed of the ACC system.

Claims

[1] Method for controlling a vehicle with a driver assistance system having a brake assistance function and with an environment sensor unit generating environment data, in which the brake pedal position or the brake pedal actuation force of a brake pedal actuated by a driver is detected by means of a brake pedal position sensor or a brake pedal actuation force sensor and evaluated by the driver assistance system, wherein - when the driver operates the brake pedal, a brake pedal position or a brake pedal actuation force is detected that is less than a predetermined threshold value, the driver assistance system generates a braking torque request depending on the dynamic driving state of the vehicle and the environmental data, and - if the specified threshold value is exceeded by the driver's brake pedal operation with regard to the brake pedal position or the brake pedal operation force, the brake assistance function is deactivated, and - in the event of a brake pedal actuation by the driver with a brake pedal position or a brake pedal actuation force that is less than the predetermined threshold value, the driver assistance system generates a second modified braking request that differs from a first braking request that the driver assistance system generates without brake actuation by the driver. [2] Method according to claim 1, characterized by that threshold value is determined according to the end of the free travel of the brake pedal. [3] Method according to claim 1 or 2, characterized bythat when negotiating a curve, the driver assistance system generates a braking torque request that is optimized with regard to the vehicle's dynamic state when negotiating the curve. [4] Method according to claim 3, characterized by that the cornering or the impending cornering is detected by the driver assistance system from the surrounding data. [5] Method according to claim 3 or 4, characterized by that the cornering or the impending cornering is detected from the digital map data provided by the driver assistance system. [6] Method according to one of the preceding claims, characterized bythat traffic sign recognition information is provided to the driver assistance system from the surrounding data, and when a speed limiting traffic sign is detected, a braking torque request is generated that is adapted to the speed limit indicated by the traffic sign. [7] Method according to one of the preceding claims, characterized by that rear environmental data of the vehicle are taken into account when generating the braking torque request. [8] Method according to one of the preceding claims, characterized by that when generating the braking torque request, environmental data from the lanes adjacent to the lane in which the vehicle is traveling are taken into account. [9] Method according to one of the preceding claims, characterized by that the brake assistance function is carried out by an ACC system as a driver assistance system. [10] Method according to one of the preceding claims, characterized bythat the vehicle is equipped with a hybrid or electric drive and that the braking power to be generated with the braking torque request is initially provided by recuperative braking. [11] Method according to one of the preceding claims, characterized by that the vehicle is equipped with a hybrid or electric drive and, if the regenerative braking power is available and corresponds to the braking torque requirement, the braking force curve is adapted to the available regenerative braking power.