DE10160278A1 - Braking assistance function improvement method adjusts relationship between accelerator pedal movement and delivered engine torque during emergency braking - Google Patents

Abstract

The method has a given braking force provided automatically upon indication of an emergency braking situation by detection of maximum braking by the driver or a critical travel situation, with adjustment of the relationship between the movement of the accelerator pedal and the torque delivered by the engine.

Description

The invention relates to a method for improving a Brake assist function, in which after the detection of a Driver request for a maximum delay and / or one critical driving situation related to an emergency braking situation indicate a certain braking force automatically adjustable is for a vehicle with a selectable relationship between the actuation path of an accelerator pedal or accelerator pedal and one resulting engine torque (accelerator pedal engine torque characteristic).

Brake assist (BA / TBA) systems were developed because Investigations have shown that normal drivers in Emergency braking situations often fail or the required braking force can only enter with a delay using the brake pedal. Therefore control brake assist systems after recognizing one Driver request after a certain delay and / or one critical driving situation related to an emergency braking situation indicate a certain braking force automatically. to Realization of the shortest possible braking distance is the Braking force automatically compared to that of the driver induced braking force preferably up to the maximum Braking power increased.

The object of the invention is the method for operating a Brake assist system to improve.

The object is achieved by the features of independent claims.

Particularly advantageous developments and refinements of Invention are specified in the dependent subclaims.  

It is essential for the invention that according to a recognized indication of an emergency braking situation, d. H. when a Indication of a driver request for a maximum deceleration and / or is recognized as a critical driving situation or as recognized, the accelerator pedal engine torque characteristic can be changed is.

It is provided according to the invention that if a reference to an emergency braking situation is recognized or is recognized, one certain, predetermined accelerator pedal engine torque characteristic is set or an accelerator pedal engine torque characteristic is calculated and set.

According to the invention, the predetermined or calculated accelerator pedal Motor torque characteristic is a reduced motor torque with a preferably substantially linear relationship between the Accelerator pedal position and engine torque.

According to the invention, if a reference to a Emergency braking situation is recognized or is considered recognized, a increased brake force boost set. That means at given a braking system, the gain factor V increased, resulting in a certain brake pedal position increased braking pressure or braking force in the wheel brakes is controlled.

According to the invention it is provided that if a reference to an emergency braking situation is recognized or is considered to be recognized Brake force offset is set. Through the brake force offset at least the games (air games) of the braking system overcome, whereby the brake pads at least to the Brake discs and / or drums of the wheel brakes are applied. If necessary, a (low) form of a few bar brake pressure, preferably approx. 1 to 5 bar upstream pressure, in particular about 3 bar, or a corresponding braking force in the wheel brakes are activated.  

It is provided according to the invention that the change in Accelerator pedal engine torque characteristic according to a Danger calculator of a radar or one Vehicle environment sensors, driver footwell monitoring and / or an analysis of the brake pedal movement is carried out.

The vehicle is preferably a motor vehicle with a electronic accelerator pedal (e-gas). With an e-gas can technically advantageous the accelerator pedal engine torque characteristic can be changed relatively easily.

According to the invention, the method is used in vehicles with active, Interventionally capable braking systems are used, in which one External power source that is not directly from the driver depends, is controllable to the brake application of the In principle, the driver independent of the wheel brakes with braking force to act upon. Here the brake system gain and a Brake pressure or vehicle deceleration offset technically relative can be easily predetermined or changed so that the driver can achieve a faster build-up of brake pressure. such Braking systems are especially optimized hydraulic brakes (OHB), in which braking force generated by the driver by a hydraulic pump to be reinforced or built, or brake by-wire brake systems, such as electro-hydraulic brakes (EMS) or electromechanical brakes (EMB).

According to the invention, the vehicle advantageously has a brake by-wire braking system on which the brake pedal is pressed detected by a sensor device and in corresponding Input signals for a control unit for controlling the Brake system is converted. The control unit controls one External energy source (pressure source or power source) that basically means a driver-independent energy source through which the wheel brakes with braking pressure or braking force are acted upon. The pedal feel you are used to  is generated by a brake pedal travel simulator. The brake pressure or the braking force can be controlled by hydraulic Actuators in the case of an electro-hydraulic brake (EMS) or through electromechanical actuators at one Electromechanical brake (EMB) applied to the wheel brakes become. At the EMB the brake pads are against the Brake disc or drum using electromechanical Actuators pressed. There are no hydraulic Components needed. The electromechanical actuators are through an electrical power supply system of the Motor vehicle supplied as an energy source.

According to the invention, however, the vehicle preferably has one electro-hydraulic brake (EMS) on which a hydraulic Motor-pump unit with high-pressure accumulator as External energy source is used, by means of which the wheel brakes Brake pressure can be applied via hydraulic lines.

The invention will now reference to figures (Fig. 1 to Fig. 3) explained in greater detail.

Show it:

Fig. 1 is a flow diagram of one embodiment of the method according to the invention,

Fig. 2 shows a first example of a course according to the invention of the engine torque and braking torque as a function of accelerator pedal position

Fig. 3 shows a second example of a course of the engine torque and braking torque according to the invention depending on the accelerator pedal position.

In Fig. 1 is a flow diagram of one embodiment of the method according to the invention is shown schematically. To detect an emergency braking situation, the signals of a vehicle surroundings sensor system, in particular a radar hazard computer 1 , a monitoring of the driver's footwell 2 , a monitoring of the accelerator pedal position or movement 3 and a "classic" brake assistant 4 with monitoring of the movement of the brake pedal are evaluated. These possible input signals can be evaluated together or individually or in any combination, the signal of the brake pedal actuation, ie the "classic" brake assistant 4 , being preferably always taken into account.

The risk calculator of the radar or the vehicle surroundings sensor system 1 forms as output a safety size .DELTA.d 5 d from the distance and d is the derived quantities relative velocity and relative acceleration d "to a preceding vehicle as input quantities 6, z 7, 8, brake. As a preceding vehicle at a short distance from your own vehicle, the safety variable Δd 5 is large (against 1.) When driving freely, it is 0.

Footwell monitoring 2 is carried out e.g. B. by analyzing the movement of the driver's foot away from the accelerator pedal, given by the input variables distance × 9 and foot / pedal relative speed x '10. A safety variable Δx is also calculated as output variable 11 . If the foot moves away from the accelerator quickly, this safety parameter is high (against 1). In the formation of the safety variable, the time period between leaving the accelerator pedal and touching the brake pedal T can also be taken into account as input variable 12 .

Furthermore, the movement of the accelerator pedal in actuation travel y and derived variables, such as speed y 'and acceleration y ", are monitored as input variables 13 , 14 , 15 and converted into a further safety variable Δy as output variable 16 .

The classic brake assistant 4 analyzes the movement of the brake pedal in a known manner, ie the pedal travel s 17 and its time derivative s' 18 as input variables. B. the driving speed of the own vehicle also a safety variable Δs as the output variable 18th

In a central unit 19 , which is assigned to the brake assistant BA / TBA, these various safety variables are weighted according to situational relevance, coordinated (e.g. temporally) and in a brake / engine intervention with the respective movement variables (brake assistant or Ba / TBA intervention ) implemented and the vehicle braking system, e.g. B. EMS system supplied.

The implementation of the BA / TBA intervention takes place according to the invention in a change in the resulting accelerator pedal engine torque characteristic, with a torque M _reducing the engine torque as output variable 20 and a brake force _offset F _pre-filling as output variable 21 . The brake force offset "pre-fills" (hydraulic) wheel brakes, as a result of which the air clearances are overcome, brake pads are at least applied to the brake discs and / or drums and, if necessary, a low brake pressure of a few bar or a corresponding force is applied. A new gain factor V for the brake system is preferably determined and set as a further output variable 22 . This means that the amplification factor V is changed in particular in the direction of stronger amplification 13 , represented schematically by the arrow V in the illustration in FIG. 1. The amplification is dependent on the brake pedal position S _pedal 23 . 22 from the gain V and the braking force F offset _prefill 21 is obtained by adding 24 a resulting braking force F _brake 25th From this, a brake force or brake pressure distribution to be set is determined in a control unit 26 in accordance with the known methods of electronic brake control and the brake forces F _{brakes VA} 27 and F _brakesHA 28 are applied to the wheel brakes of the front axle VA and rear axle Ha.

In FIG. 2 is a first embodiment of an inventive course of the engine torque, an indexed from an electronic accelerator pedal (E) gas engine torque M ie _ind and braking torque or braking force F _brake in dependence on the accelerator pedal position S shown with the change in the "normal" characteristic of the E-Gas KL ₀ (thick solid line) can be seen. If the driver's foot is on the accelerator pedal and an emergency braking situation is recognized, the TBA / BA preferably calculates an increased braking system gain V 22 and one for the vehicle environment sensor system using the safety variable Δd 5 or directly from the movement variables d, d ', d "of the vehicle surroundings sensor system Reaching the necessary deceleration required braking force F _{pre-filling max} 21. According to the invention, a reducing engine torque M _red (thin dashed line) is calculated and a situation-adapted accelerator pedal characteristic curve KL ₁ (thin solid line) and a brake pre-filling F _pre-filling (thin dashed line) are set The reduced engine torque M _red can be transmitted to the electronics of the drive motor by means of an interface of the electronic brake control system, such as already exists, for example, for traction control (ASR or TCS) or vehicle dynamics control (ESP). In the unaffected case, the engine torque M _reduces the value of the maximum engine torque ts.

The driver from point A to a known "old" gas pedal control map KL ₀ reduces Coming accelerator pedal position, so initially the engine torque is reduced (M _red) and with the redemption of the accelerator pedal, from the point A _1, the accelerator pedal operation follows a new characteristic curve KL ₁ . If the accelerator pedal is withdrawn further until below the point A ₂ , ie below the drag torque M _drag the drive motor and an additional (low) braking force Ffilling, e.g. B. applied by an EMS / EMB system, preferably an EMS system, a point B is reached as the resulting torque or force at which a torque M _reducing the drive torque is _reduced and a braking force F _is present. This enables the driver to continuously dose the process. If the accelerator pedal is withdrawn further, the maximum, in accordance with z. B. the vehicle _{environment sensor system} determined braking force F _{prefill max} . The brake is optimally conditioned (pre-filled) for driver (emergency) braking in the sense of TBA / BA.

If the driver presses the accelerator pedal again in point B, the resulting drive torque must increase according to the driver's specification. For this purpose, the braking force and the reducing torque are reduced, so that the same characteristic curve as when the accelerator pedal is withdrawn, but preferably an at least slightly steeper characteristic curve KL ₂ (thin solid line) results. When point C is reached, the normal characteristic curve KL ₀ becomes effective again unaffected by the brake assist (TBA / BA).

These measures make the driver very good adjustable drive and braking effect with the accelerator pedal in Combination achieved with a BA / TBA intervention.

FIG. 3 shows a second example of a course of the engine torque and braking torque according to the invention as a function of the accelerator pedal position, the maximum braking force F _{pre-filling max} changing _over time, in this example being increased. This can e.g. B. by changing the distance or relative speed to the vehicle ahead. In contrast to the situation shown in FIG. 2, from point B 'with F _{pre-filling max} at a first point in time (t ₁ ), the accelerator pedal characteristic curve KL ₃ (thin dashed line) adapted to the situation is continuously adjusted to the changing maximum braking force (arrow P), until at point C 'at a second point in time (t ₂ ) the characteristic of F _{pre-filling max} (t ₂ ) is defined and a further accelerator pedal characteristic curve KL ₄ (thin dashed line) is reached. Thus, in the sense of the invention, the currently valid characteristic curve of the current driving situation, ie the currently recognized dangerous situation, is adapted or determined.

In addition to the methods described here, a characteristic curve that can only be specified in stages or a fixed situation-adapted characteristic such as, for example, B. shown in Fig. 2 may be provided. These characteristic curves can then not only depend on information from the vehicle surroundings sensor system, but can also be generally specifiable. For example, the accelerator pedal characteristic can be automatically switched by a distance control system (ACC system) to assist when the accelerator pedal is actuated and / or automatically by a brake system or vehicle dynamics system (ESP, EHB) via switches during traffic jams, at low speeds for better maneuvering (maneuvering assistance to standstill) , EMB) for assistance when driving downhill, even with a trailer load. It is possible that the changes in the resulting accelerator pedal characteristic also depend on the accelerator pedal movement itself. Thus, it is provided that when the accelerator pedal is quickly withdrawn, the identifier is changed in the sense of a situation-adapted e-gas characteristic.

Basically, it is provided that the drive braking torque may only change in the direction specified by the driver. This means that the characteristic curves must be determined that when you take back the accelerator pedal, there is a decrease in the Driving torque or increase in braking torque results and  vice versa. Changes without a driver request are not here provided as the system is only to assist the driver should serve and z. B. no automatic heavy braking should initiate.

Claims (9)

1. A method for improving a brake assistant function, in which, after the detection of a driver's request for a maximum deceleration and / or a critical driving situation, which indicate an emergency braking situation, a specific braking force can be set automatically, for a vehicle with a selectable relationship between the actuation path of the accelerator pedal or accelerator pedal and a resulting engine torque (accelerator pedal engine torque characteristic or accelerator pedal characteristic), characterized in that the accelerator pedal engine torque characteristic can be changed in accordance with a recognized indication of an emergency braking situation. 2. The method according to claim 1, characterized in that if a reference to a Emergency braking situation is recognized or is considered recognized, a certain, predetermined accelerator pedal engine torque characteristic is set or an accelerator pedal engine torque characteristic is calculated and set. 3. The method according to claim 2, characterized in that the predetermined or calculated accelerator pedal engine torque characteristic a reduced Has engine torque. 4. The method according to claim 2 or 3, characterized in that the predetermined or calculated accelerator pedal engine torque characteristic one im essential linear relationship between the Has accelerator pedal position and the engine torque. 5. The method according to any one of claims 1 to 4, characterized in that if a reference to a  Emergency braking situation is recognized or is considered recognized, a increased brake booster is set. 6. The method according to any one of claims 1 to 5, characterized in that if a reference to a Emergency braking situation is recognized or is considered recognized Brake force offset is set. 7. The method according to any one of claims 1 to 6, characterized in that the change in accelerator pedal Motor torque characteristic curve in accordance with a hazard calculator a radar or a vehicle surroundings sensor system, one Driver footwell monitoring and / or an analysis of the Brake pedal movement takes place. 8. The method according to any one of claims 1 to 7, characterized in that the vehicle is a Motor vehicle with an electronic accelerator pedal (E-gas) is. 9. The method according to any one of claims 1 to 6, characterized in that the vehicle is a Motor vehicle with a brakeby-wire braking system, preferably an electro-hydraulic brake (EMS).