Method for actuating hydraulic non-human powered vehicle braking equipment for autonomous driving

Abstract

To activate a hydraulic non-human-powered vehicle braking system for autonomous driving, the present invention proposes generating brake pressure by a second non-human-powered brake pressure generator when no brake pressure or insufficient brake pressure is generated by the first non-human-powered brake pressure generator after a predetermined first time span (t1).If there is no error message of the first non-human-powered brake pressure generator within a second time span (t2) longer than the first time span (t1), the generation of brake pressure by the second non-human-powered brake pressure generator is stopped.

Description

[Technical Field]

[0001] The present invention relates to a method for actuating a hydraulic non-human-powered vehicle brake system for a land vehicle that drives autonomously on public roads up to level 4 or level 5, comprising the features of the preamble of claim 1. While the term "drive autonomously" refers to the possibility of driving autonomously, the vehicle brake system according to the invention is also applicable to land vehicles that do not drive autonomously or that drive autonomously at a relatively low level. [Background technology]

[0002] Autonomous driving up to Level 4 (where driver intervention can be requested) and Level 5 (highest level; no driver required) requires redundant, non-human-powered vehicle braking systems that virtually guarantee complete failure of the vehicle braking system without driver intervention.

[0003] Patent Document 1 discloses an electrohydraulic non-human-powered vehicle brake system having two brake units, each of which has a non-human-powered brake pressure generator with an electrically drivable pressure source and a brake pressure control valve structure for each wheel brake. One brake unit is connected to the other brake unit, and a hydraulic wheel brake is connected to one brake unit, so that the wheel brake can be operated by one brake unit and, through the one brake unit, by the other brake unit. In this way, if one brake unit fails or breaks down, the wheel brake can be operated by the other brake unit without driver intervention. The active brake unit controls the wheel brake pressure at the wheel brake. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] German Patent Application Publication No. 102014220440A1 Summary of the Invention [Problem to be solved by the invention]

[0005] The object of the present invention is to ensure that when a first non-human brake pressure generator is not generating brake pressure, or at least not generating sufficient brake pressure, the shortest possible time is lost during non-human braking for the second non-human brake pressure generator to generate brake pressure, whereby, as a rule, not both but preferably only one non-human brake pressure generator is active at any one time. [Means for solving the problem]

[0006] The vehicle brake system intended for the method of the present invention has two non-human brake pressure generators that can generate brake pressure for operating the hydraulic wheel brakes of the vehicle brake system. The non-human brake pressure generators can be a hydropump that can be driven by an electric motor, or a piston-cylinder unit in which a piston can slide in a cylinder by an electric motor, for example via a helical gear and, optionally, via an intervening mechanical reduction gear. Another option for a non-human brake pressure generator is a master brake cylinder that can be operated by a controllable vacuum brake booster or an electromechanical brake booster. This list is illustrative and not exhaustive.

[0007] According to the present invention, when the first non-human brake pressure generator has not generated the predetermined brake pressure after a first predetermined time span from receiving the brake signal and the brake signal is still present, the brake pressure is generated by the second non-human brake pressure generator. The brake signal may be a brake operation by the vehicle driver if braking should be performed non-humanly. The brake signal may also be generated independently of the vehicle driver, for example, by an autonomous vehicle management unit, a distance control for a preceding vehicle, or a distance control when approaching another vehicle or other obstacle too quickly.

[0008] When an error in the first non-operable brake pressure generator is recognized within a second time span from receipt of the brake signal, the second non-operable brake pressure generator can generate brake pressure to operate the wheel brakes. This saves time from the end of the first time span to the recognition of the error in the first non-operable brake pressure generator. If an error in the first non-operable brake pressure generator is not recognized within the second time span, in one embodiment of the method according to the present invention, the generation of brake pressure by the second non-operable brake pressure generator can be stopped. This prevents the vehicle brake equipment from being operated by the second non-operable brake pressure generator even when it should not be operated despite the presence of a brake signal or when it should not be operated by the generation of brake pressure by the first non-operable brake pressure generator. The vehicle brake system can also be operated, for example, by a third, non-human brake pressure generator, for example, by muscle or non-human operation of a master brake cylinder, or the vehicle equipped with the vehicle brake system can be decelerated in some other way, for example, by generating current through generator operation of an electric machine, whereby the hydraulic wheel brakes are not intentionally operated. The electric machine can be, for example, an electric motor or a generator operating as a generator.

[0009] The generation of brake pressure by the second non-human brake pressure generator can also be stopped using other stopping criteria, such as if the first non-human brake pressure generator (somehow) generates the specified brake pressure within the second time span from the receipt of the brake signal, or if the vehicle equipped with the vehicle brake equipment is stopped or has been stopped.

[0010] The dependent claims are directed to developments and preferred embodiments of the invention stated in the independent claims.

[0011] Any and all features disclosed in the detailed description and drawings may be embodied in an embodiment of the present invention either alone or in principle in any combination. In principle, embodiments of the present invention are also possible that have only one or more features, but not all of one claim or one embodiment of the present invention.

[0012] The invention will now be described in more detail with reference to embodiments illustrated in the drawings, which show: [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a simplified hydraulic circuit diagram showing a hydraulic non-powered vehicle brake installation for autonomous driving for implementing the method according to the invention; FIG. [Figure 2] 1 is a flow chart illustrating a method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The electrohydraulic non-human-powered vehicle braking system 1 shown in Figure 1 is intended for road vehicles, i.e., passenger cars, that operate autonomously on public roads up to level 4 or 5. Level 4 refers to autonomous driving, where the driver can be requested to intervene, and level 5, or the highest level, is autonomous driving without driver intervention. Lower levels and non-autonomous driving are possible as well.

[0015] The vehicle brake system 1 is configured as a dual-circuit vehicle brake system including four hydraulic wheel brakes 2, two of which are connected to one of two brake circuits I and II. The brake circuit I including the two hydraulic wheel brakes 2 is shown, and the other brake circuit II has the same configuration.

[0016] For non-human operation, the vehicle brake system 1 has two non-human brake pressure generators 3, 4, which can operate the wheel brakes 2 independently of each other. The first of the two non-human brake pressure generators, the first non-human brake pressure generator 3, has a piston-cylinder unit 5, the piston 6 of which is slidable in a cylinder 9 via a helical gear 8, e.g., a ball screw, by a first electric motor 7 to generate brake pressure. A mechanical reduction gear, e.g., a planetary gear (not shown), may be interposed between the first electric motor 7 and the helical gear 8. Both brake circuits I, II are hydraulically connected in parallel to the cylinder 9 of the piston-cylinder unit 5 of the first non-human brake pressure generator 3 via a first isolation valve 10, only one of which is shown in the drawings.

[0017] The second unoperated brake pressure generator 4 has a hydropump 11 that can be driven by a second electric motor 12. The hydropump 11 is, for example, a piston pump or an (internal) gear pump. Both brake circuits I, II are hydraulically connected in parallel to the second unoperated brake pressure generator 4; in this embodiment, both brake circuits I, II are connected to the pressure side of the hydropump 11. Both brake circuits I, II may be connected directly to the second unoperated brake pressure generator 4 without an intervening valve; in this embodiment, both brake circuits I, II are connected to the second unoperated brake pressure generator 4 by a non-return valve 24 to prevent backflow of brake fluid from the brake circuits I, II into or through the second unoperated brake pressure generator 4. However, it is possible that no controllable valves, such as solenoid valves, between the second unoperated brake pressure generator 4 and both brake circuits I, II are provided (not shown). The cylinder 9 of the piston-cylinder unit 5 of the first non-human brake pressure generator 3 and the hydropump 11 of the second non-human brake pressure generator 4 are both connected to a pressureless brake fluid reservoir 13 mounted on a muscle-operable dual-circuit master brake cylinder 14 to which both brake circuits I and II are hydraulically connected in parallel via a second isolation valve 15.

[0018] Between the first and second isolating valves 10, 15 on the one hand and between the wheel brake 2 and the second non-operated brake pressure generator 4, a third isolating valve 16 is arranged in each brake circuit I, II, hydraulically connected in parallel with a non-return valve 25 through which flow can pass in the direction of the wheel brake 2.

[0019] Each non-human brake pressure generator 3, 4 has its own electrical energy supply 17 - in this example each a battery - and its own electronic control unit 19.

[0020] Each wheel brake 2 has an inlet valve 20, by which it is connected to the brake circuit I, II of the associated vehicle brake system 1. Each wheel brake 2 is connected to the pressureless brake fluid reservoir 14 via a respective outlet valve 21. The inlet valve 20 and outlet valve 21 form a wheel brake pressure control valve structure, which allows for individual control of the wheel brake pressure at each wheel brake 2, where control also means control. In addition to controlling the wheel brake pressure during unpowered braking, slip control is also possible by selectively using the inlet valve 20, the outlet valve 21, and both unpowered brake pressure generators 3, 4. Such slip control includes antilock control, traction slip control, and vehicle dynamic control or electronic stability program, commonly referred to as ABS, ASR, and FDR or ESP. Such slip control is well known to those skilled in the art and will not be described here.

[0021] In this embodiment, the isolation valves 10, 15, and 16, the inlet valve 20, and the discharge valve 21 are 2 / 2-way solenoid valves, with the second and third isolation valves 15 and 16 and the inlet valve 20 open in their de-energized home positions, and the first isolation valve 10 and the discharge valve 21 closed in their de-energized home positions. Other valves and valve positions are possible. For example, the inlet valve 20 and the discharge valve 21 may be combined into a 3 / 3-way solenoid valve (not shown). The valves shown are those of the illustrated brake circuit I, 10, 13, 16, 20, and 21. The brake circuit II, not shown, has the same configuration and includes the same valves 10, 15, 16, 20, and 21.

[0022] The flowchart of FIG. 2 shows the progression of autonomous, unattended braking according to the present invention, starting with block 500. For autonomous driving, an autonomous vehicle management unit 22, which is not necessarily part of the vehicle brake system 1, sends a brake signal to the electronic controllers 18, 19 of both unattended brake pressure generators 3, 4 in step 501. The brake signal indicates that the vehicle brake system 1 should be operated unattended. In response, the first electric motor 7 drives the piston 6 in the cylinder 9 of the piston-cylinder unit 5, thereby generating brake pressure in the first unattended brake pressure generator 3 (step 502). The first isolation valve 10 is opened, and the third isolation valve 16 remains open, allowing the wheel brakes 2 to be operated with the brake pressure generated by the first unattended brake pressure generator 3. The second isolation valve 15 is closed, thereby hydraulically isolating the wheel brakes 2 from the master brake cylinder 15 and allowing non-human braking to be performed by the brake pressure generated by the first non-human brake pressure generator 3.

[0023] The generation of brake pressure by the first non-human-operated brake pressure generator 3 is monitored by the electronic control device 19 of the second non-human-operated brake pressure generator 4 by the pressure sensor 23 connected to the cylinder 9 of the piston-cylinder unit 5 of the first non-human-operated brake pressure generator 3 (step 503). In addition to the electronic control device 19 of the second non-human-operated brake pressure generator 4, the pressure sensor 23 also transmits its pressure signal to the electronic control device 18 of the first non-human-operated brake pressure generator 3 and the autonomous vehicle management unit 22.

[0024] If the first non-human brake pressure generator 3 does not generate brake pressure, or at least does not generate the predetermined brake pressure, during the first predetermined time span t1 from the start of the brake signal, or the brake pressure generation gradient is too low and the brake signal of the autonomous vehicle management unit 22 is still present, brake pressure is generated by the second non-human brake pressure generator 4 by driving the hydropump 11 by the second electric motor 12 (step 504).

[0025] If the electronic control device 19 of the second non-human brake pressure generator 4 receives an error message from the first non-human brake pressure generator 3 within a predetermined second time span t2, which is longer than the first time span t1, from the start of the brake signal (step 505), the first isolation valve 10 of the first non-human brake pressure generator 3 is closed, and the wheel brakes 2 are operated by the brake pressure generated by the second non-human brake pressure generator 4 (step 506). The error message from the first non-human brake pressure generator 3 indicates that the first non-human brake pressure generator 3 has failed, or at least is unable to generate sufficient brake pressure in a sufficiently short time. In addition to the electronic control device 18 of the first non-human brake pressure generator 3, the error message can also be received from, for example, the autonomous vehicle management unit 22.

[0026] If the electronic control device 18 of the second non-operable brake pressure generator 4 does not receive an error message from the first non-operable brake pressure generator 3 within the second time span t2, the generation of brake pressure by the second non-operable brake pressure generator 4 is stopped (step 507). The reason for the absence of an error message may be that brake pressure should not be generated by the first non-operable brake pressure generator 3 despite the brake signal. This is the case, for example, when current is generated by an electric motor operating as a generator or by a generator for electrical energy harvesting, and the vehicle equipped with the vehicle brake equipment 1 is thus sufficiently decelerated by the electric motor or generator. In such a case, operation of the wheel brakes 2 by the second non-operable brake pressure generator 4 is impaired.

[0027] If the first non-human brake pressure generator 3 generates sufficient brake pressure within the second time span t2 from the start of the brake signal, and the vehicle is sufficiently decelerated despite insufficient or too low brake pressure generation, or if the vehicle is stopped or parked, the generation of brake pressure by the second non-human brake pressure generator 4 can also be stopped.

[0028] If an error message of the first non-human brake pressure generator 3 is already present at the start of the brake signal or within the first time span t1 from the start of the brake signal (step 502), brake pressure is generated by the second non-human brake pressure generator 4 from the start of the brake signal or from the reception of the error message (step 506).If the first non-human brake pressure generator 3 is not available for reasons other than an error, or if there is no error message but it is at least not available, brake pressure is also generated by the second non-human brake pressure generator 4 from the start of the brake signal (steps 502 and 506). [Explanation of symbols]

[0029] 1 Vehicle brake equipment 2 hydraulic wheel brakes 3. First non-human brake pressure generator 4. Second non-human brake pressure generator 18,19 Electronic control unit t1 first timespan t2 first time span p1 brake pressure

Claims

1. A method for operating a hydraulic non-human-powered vehicle braking system for autonomous driving, comprising a first non-human-powered brake pressure generator (3) and a second non-human-powered brake pressure generator (4) connected to hydraulic wheel brakes (2), the method comprising: １ ), the first non-human brake pressure generator (3) generates a predetermined brake pressure (p １ ) and brake pressure is generated by the second non-powered brake pressure generator (4) under a brake signal when the brake signal is still present.

2. A second predetermined time span (t) is longer than the first time span (t1) from the reception of the brake signal. ２ 2. The method according to claim 1, characterized in that the generation of brake pressure by the second non-human brake pressure generator (4) is discontinued when there is no error message of the first non-human brake pressure generator (3) within the

3. The second predetermined time span (t) is longer than the first time span (t1) from the reception of the brake signal. ２ 3. The method according to claim 1, wherein the generation of brake pressure by the second non-operable brake pressure generator (4) is stopped when the first non-operable brake pressure generator (3) generates a predetermined brake pressure inside the vehicle brake system (1) or when the vehicle equipped with the vehicle brake system (1) is stationary.

4. 4. The method according to claim 1, wherein when the first non-human brake pressure generator (3) is not ready to generate brake pressure, brake pressure is generated by the second non-human brake pressure generator (4) immediately upon receipt of a brake signal.

5. 5. The method according to claim 1, wherein when an error message of the first non-human brake pressure generator (3) is present, braking pressure is generated by the second non-human brake pressure generator (4) immediately upon receipt of a brake signal.

6. 6. The method according to claim 1, wherein the method is not performed when a predetermined brake pressure is generated in a manner other than by the first non-human brake pressure generator (3) and / or when a vehicle equipped with the vehicle brake equipment (1) is decelerated by a predetermined deceleration in a manner other than by the vehicle brake equipment (1).

7. 7. A method according to claim 1, wherein the non-powered brake pressure generator (3, 4) has an electronic control unit (18, 19).

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