Method and device for determining a maximum speed for a vehicle and automatic drive system

Abstract

A method for determining a maximum speed for a vehicle, including: receiving items of state information concerning a state of at least one vehicle component of the vehicle; and determining a maximum speed of the vehicle on the basis of the state information, such that a stopping path of the vehicle from a recognition of a dangerous state until the vehicle is at a standstill is less than or equal to a specified value.

Claims

1. A method of a vehicle, the method comprising: the vehicle monitoring a state of a braking system of the vehicle; a processor of the vehicle determining, as a first time period and based on the monitored state of the braking system, an amount of time required for building up a maximum braking potential in the braking system; the processor determining, as a second time period, an amount of time required to bring the vehicle to a standstill after the maximum braking potential is built up in the braking system; the processor determining a maximum speed of the vehicle based on the first and second time periods, such that a stopping path of the vehicle from a recognition of a dangerous state until the vehicle is at a standstill is less than or equal to a specified value; and the processor outputting an indication of the determined maximum speed to a user interface or performing an automatic control of the vehicle speed based on the determined maximum speed.

2. The method of claim 1, further comprising the vehicle monitoring a state of at least one vehicle sensor of the vehicle and, based on the state of the at least one vehicle sensor, a recognition time required for the recognition of the dangerous state, wherein the maximum speed is determined additionally based on the recognition time.

3. The method of claim 2, further comprising the vehicle monitoring a state of a communication system between the brake system and the at least one vehicle sensor and the processor determining a communication time for a communication between the brake system and the at least one vehicle sensor, wherein the maximum speed is determined additionally based on the communication time.

4. A device of a vehicle, the device comprising: a processor; and an input interface; wherein the processor is configured to: receive state information about, and obtained by the vehicle monitoring, a state of a braking system of the vehicle; determine, as a first time period and based on the monitored state of the braking system, an amount of time required for building up a maximum braking potential in the braking system; determine, as a second time period, an amount of time required to bring the vehicle to a standstill after the maximum braking potential is built up in the braking system; determine the maximum speed of the vehicle based on the first and second time periods so that a stopping path of the vehicle from a recognition of a dangerous state until the vehicle is at a standstill is less than or equal to a specified value; and output an indication of the determined maximum speed to a user interface of the device or perform an automatic control of the vehicle speed based on the determined maximum speed.

5. The device of claim 4, wherein the processor is configured to receive state information about, and obtained by the vehicle monitoring, a state of at least one vehicle sensor of the vehicle and calculate, based on the state of the at least one vehicle sensor, a recognition time that is required to recognize the dangerous state, and wherein the maximum speed is determined additionally based on the recognition time.

6. The device of claim 5, wherein the processor is configured to receive state information about, and obtained by the vehicle monitoring, a state of a communication system between the brake system and the at least one vehicle sensor and calculate, based on the state of the communication system, a communication time for a communication between the brake system and the at least one vehicle sensor, and wherein the maximum speed is determined additionally based on the communication time.

7. An automated driving system for a vehicle, the automated driving system comprising: a device including a processor and an input interface, wherein the processor is configured to: receive state information about, and obtained by the vehicle monitoring, a state of a braking system of the vehicle; determine, as a first time period and based on the monitored state of the braking system, an amount of time required for building up a maximum braking potential in the braking system; determine, as a second time period, an amount of time required to bring the vehicle to a standstill after the maximum braking potential is built up in the braking system; determine the maximum speed of the vehicle based on the first and second time periods so that a stopping path of the vehicle from a recognition of a dangerous state until the vehicle is at a standstill is less than or equal to a specified value; perform an automatic control of the vehicle speed based on the determined maximum speed.

8. The method of claim 1, wherein the first time period is an amount of time required for a maximal brake pressure build up in hydraulics of the braking system.

9. The method of claim 1, wherein the method comprises the processor performing the automatic control of the vehicle speed based on the determined maximum speed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic diagram of a device for determining a maximum speed for a vehicle according to a specific embodiment of the present invention.

(2) FIG. 2 shows an illustration of a stopping path of a vehicle under normal conditions and under impaired conditions, with the same initial speed in each case.

(3) FIG. 3 shows an illustration of the stopping path under normal conditions and under impaired conditions and with reduced initial speed.

(4) FIG. 4 shows a schematic diagram of an automated driving system for a vehicle according to a specific embodiment of the present invention.

(5) FIG. 5 shows a flow diagram explaining a method for determining a maximum speed for a vehicle according to a specific embodiment of the present invention.

DETAILED DESCRIPTION

(6) FIG. 1 shows a block diagram of a device 1 for determining a maximum speed for a vehicle.

(7) Device 1 includes an input interface 2 that is configured to receive state information concerning a state of vehicle components 4. Input interface 2 can be coupled to the vehicle components 4 for this purpose. In particular, input interface 2 can be capable of being coupled to vehicle components 4 via a bus system of the vehicle.

(8) Device 1 further includes a determining device 3 that is configured to determine, on the basis of the state information, the maximum speed v.sub.max of the vehicle in such a way that a stopping path d.sub.stopping of the vehicle from a recognition of a dangerous state until the vehicle is at a standstill is less than or equal to a specified value.

(9) Vehicle components 4 include at least one vehicle sensor 4a that can include radar sensors, infrared sensors, or vehicle cameras. Vehicle sensor 4a is configured to provide sensor data or environmental data relating to a surrounding environment of the vehicle. Vehicle sensor 4a may include a recognition device that is configured to recognize a dangerous situation on the basis of the sensor data.

(10) Vehicle components 4 further include a brake system 4b that is configured to brake the vehicle. Brake system 4b may include a hydraulic brake system, for example a plunger-based brake system or a piston brake system. The brake system can in addition include an anti-locking system. The brake system can include an automatic brake system that automatically brakes the vehicle to a standstill when a dangerous state has been recognized by the at least one vehicle sensor 4a.

(11) Vehicle components 4 further include a communication system 4c that is coupled to brake system 4b and to the at least one vehicle sensor 4a and that is configured to transmit information from the at least one vehicle sensor 4a, possibly via at least one control device, to brake system 4b. Communication system 4c can include a bus system of the vehicle.***

(12) Vehicle components 4a, 4b, 4c can each provide corresponding information about the state of the respective vehicle component 4a, 4b, 4c, and transmit it to input interface 2.

(13) This state information can include for example information about a state of the at least one vehicle sensor 4a. This can include for example a recognition time TD (“time to detect”) that the at least one vehicle sensor 4a requires in order to acquire an object, such as a pedestrian, to classify it, and to recognize a dangerous state. Recognition time TD thus corresponds to the time required for vehicle sensor 4a to recognize the dangerous state. If at least one of the vehicle sensors 4a fails due to a defect or has a lower precision of recognition due to changed environmental conditions, such as poor weather conditions, then recognition time TD is reduced correspondingly. The information about the state of the at least one vehicle sensor 4a can include the recognition time TD reduced in this way. The information about the state of the at least one vehicle sensor 4a can however also include information relating to a defect or to the operating states of vehicle sensor 4a, determining device 3 being configured to calculate recognition time TD on the basis of this information.

(14) The state information can in addition include information about a state of brake system 4b, for example information as to whether brake system 4b is in a normal state or in an impaired state. Determining device 3 is configured to calculate, based on the information about the state of brake system 4b, a brake time TB (“time to brake”) from a beginning of the braking process until the vehicle is at a standstill. Determining device 3 here calculates a first brake time TTL (“time to lock”) from a beginning of the braking process until the full braking power is achieved. In a hydraulic brake system, this corresponds to the time required to build up the complete brake pressure. In addition, determining device 3 calculates a second brake time T.sub.stop from the reaching of the full brake power until the vehicle is at a standstill. This corresponds to the time required by the brake system to brake the vehicle at full brake pressure.

(15) Braking time TB corresponds to the sum of first braking time TTL and second braking time T.sub.stop.

(16) In addition, the items of state information include information about a state of communication system 4c, determining device 3 being configured to calculate, on the basis of the information about the state of the communication system 4c, a communication time TT (“time to travel”) for the communication between brake system 4b and the at least one vehicle sensor 4a.

(17) The respective items of state information can be ascertained by the respective vehicle components 4 themselves, using recognition algorithms. However, the items of state information can also be ascertained by a sensor device of device 1.

(18) According to further specific embodiments, the items of state information can already include recognition time TD, brake time TB, and/or communication time TT.

(19) Determining device 3 is configured to calculate a maximum stopping path d.sub.stopping of the vehicle, which is initially moving at a maximum speed v.sub.max, on the basis of the following equation:
d.sub.stopping=d1+d2+d3+d4,
where d1=TD.Math.v.sub.max, d2=TT.Math.v.sub.max, d3=TTL.Math.v.sub.max−⅙.Math.k.Math.TTL.sup.3, and d4=v.sub.rest.sup.2/(2.Math.a.sub.max).

(20) The first stopping path segment d1 corresponds to the path traveled during recognition time TD, the second stopping path segment d2 corresponds to the path traveled during communication time TT, the third stopping path segment d3 corresponds to the path traveled during the first braking time TTL, and the fourth stopping path segment d4 corresponds to the path traveled during the second braking time T.sub.stop.

(21) The variable a.sub.TTL=k.Math.TTL is the delay during the pressure buildup phase, where k=a.sub.max/TTL is the linear increase. Here, a.sub.max is the maximum deceleration that brake system 4b exerts on the vehicle during second braking time T.sub.stop. The first integral of a.sub.TTL is v.sub.TTL=½.Math.k.Math.TTL.sup.2 and the second integral is d.sub.TTL=⅙.Math.k.Math.TTL.sup.3, which is the second term of third stopping path segment d3.

(22) While, here, a linear curve is assumed for the deceleration, determining device 3 can also take into account, as a function of the characteristic of brake system 4b, a non-linear functional dependence of the deceleration on the first braking time TTL; in this case the respective shapes would be correspondingly modified.

(23) In addition, v.sub.rest=v.sub.max−½.Math.k.Math.TTL.sup.2 is the residual speed after the complete buildup of brake pressure, i.e. after first braking time TTL. Substituting this relation into the equation for the stopping path d.sub.stopping yields the following equation:
d.sub.stopping=TD.Math.v.sub.max+TT.Math.v.sub.max−TTL.Math.v.sub.max−⅙.Math.k.Math.TTL.sup.3+(v.sub.max−½.Math.k.Math.TTL.sup.2).sup.2/(2.Math.a.sub.max)

(24) In an errored or degraded state, first braking time TTL, second braking time T.sub.stop, recognition time TD and communication time TT, as well as the maximum deceleration a.sub.max, can deviate from the corresponding values in the normal state. In the degraded state, determining device 3 calculates stopping path d.sub.stopping according to the following equation, in which the maximum speed v.sub.max,degr is a free parameter:
d.sub.stopping degr,degr=TD.sub.degr.Math.v.sub.max,degr+TT.sub.degr.Math.v.sub.max,degrTTL.sub.degr.Math.v.sub.max,degr−⅙.Math.k.Math.TTL.sub.degr.sup.3+(v.sub.max,degr−½.Math.k.Math.TTL.sub.degr.sup.2).sup.2/(2.Math.a.sub.max,degr).

(25) Here, the index “degr” stands for the value of the respective variable in the degraded state.

(26) If the maximum speed v.sub.max of the vehicle is not changed, i.e. if v.sub.max=v.sub.max,degr, then the scenario shown in FIG. 2 results. In the normal state, the course of speed v shown in curve y1 results as a function of the traveled distance d. Due to the stopping path segments, prolonged in the degraded state, d1.sub.degr, d2.sub.degr, d3.sub.degr, d4.sub.degr, the overall stopping path becomes longer, as can be seen in the course of speed v shown in curve y2.

(27) Determining device 3 is configured to calculate the maximum speed v.sub.max in such a way that the stopping path d.sub.stopping,degr in the degraded state, starting from the maximum speed v.sub.max,degr in the degraded state, is the same size as the stopping path d.sub.stopping in the normal state, starting from the maximum speed v.sub.max in the normal state. This corresponds to the scenario illustrated in FIG. 3.

(28) Thus, determining device 3 calculates the maximum speed v.sub.max under the condition d.sub.stopping=d.sub.stopping,degr. Substitution and rewriting first yields the following equation:
d.sub.stopping+⅙.Math.k.Math.TTL.sub.degr.sup.3=TD.sub.degr.Math.v.sub.max,degr+TT.sub.degr.Math.b.sub.max,degr+TTL.sub.degr.Math.v.sub.max,degr+v.sub.max,degr.sup.2/(2.Math.a.sub.max,degr)−v.sub.max,degr.Math.k.Math.TTL.sub.degr.sup.2/2.Math.a.sub.max,degr+¼.Math.k.sup.2.Math.TTL.sub.degr.sup.4/(2.Math.a.sub.max,degr)
and, finally, the following equation:
d.sub.stopping+⅙.Math.k.Math.TTL.sub.degr.sup.3−¼.Math.k.sup.2.Math.TTL.sub.degr.sup.4/(2.Math.a.sub.max,degr)=v.sub.max,degr.Math.(TD.sub.degr+TT.sub.degr+TTL.sub.degr−k.Math.TTL.sub.degr.sup.2/(2.Math.a.sub.max,degr))+v.sub.max,degr.sup.2/(2.Math.a.sub.max,degr).

(29) The latter expression is a second-order equation for v.sub.max,degr that is correspondingly solved by determining device 3 according to v.sub.max,degr. The value obtained by solving this equation is the maximum speed calculated by determining device 3.

(30) According to a development, device 1 can be configured to control brake system 4b in such a way that the first brake time TTL is reduced when determining device 3 recognizes, on the basis of the state information, the impairment of at least one vehicle component 4. Thus, device 1 can control brake system 4b using a control signal in such a way that a hydraulic brake apparatus of brake system 4b is pre-filled with a pressure at a specified level, for example 5 bar. In this way, the time required to reach full braking power is reduced.

(31) Device 1 can in addition be configured to output a control signal in order to control the vehicle in such a way that a maximum achievable speed of the vehicle is limited by the determined maximum speed v.sub.max.

(32) In addition, device 1 can include a display device that displays the determined maximum speed to the driver of the vehicle.

(33) Device 1 can be an element of a driver assistance system for a vehicle that is configured to control the vehicle in such a way that the absolute speed of the vehicle is always less than the maximum speed v.sub.max.

(34) FIG. 4 shows an automated driving system 5 for a vehicle F according to a specific embodiment of the present invention. Automated driving system 5 includes a device 1 for determining a maximum speed v.sub.max for vehicle F according to one of the above-described specific embodiments. Automatic driving system 5 also has at least one vehicle component 4 that is coupled to device 1 and is configured to transmit state information to device 1. Vehicle component 4 may include, as described above, at least one vehicle sensor 4a, a brake system 4b, and a communication system 4c between brake system 4b and the at least one vehicle sensor 4a.

(35) Device 1 further includes a determining device 3 that, as described above, is configured to determine the maximum speed v.sub.max of the vehicle.

(36) Automated driving system 5 may have a control device that is configured to autonomously control vehicle F, a driving speed of vehicle F always being less than the defined maximum speed v.sub.max.

(37) FIG. 5 shows a flow diagram explaining a method for determining a maximum speed for a vehicle F.

(38) In a first method step S1, state information is received concerning a state of at least one vehicle component 4 of vehicle F.

(39) In a further method step S2, a maximum speed v.sub.max of vehicle F is determined on the basis of the state information, a stopping path of vehicle F from a recognition of a dangerous state until vehicle F is at a standstill always being less than or equal to a specified value. The calculation of the maximum speed v.sub.max can be carried out according to one of the specific embodiments described above.