Braking systems for autonomous vehicles

Abstract

The invention relates to a braking system in an at least partially autonomous vehicle, which has a wheel brake (1) for each wheel (VR, VL, HR, HL), the wheel brakes being equipped with a main brake control system (BRS1) and a redundant secondary brake control system (BRS2), the main brake control system having a main controller and an electromechanical main actuator for each wheel for actuating the wheel brakes, the main controller generating a main control signal for actuating the corresponding electromechanical main actuator based on a theoretical deceleration preset value generated in a pilot system and / or a theoretical deceleration preset value generated on the driver's side by means of a brake pedal. According to the invention, the secondary brake control system has a secondary controller independent of the main controller and an electromechanical secondary actuator independent of the main actuator for each wheel. The secondary controller generates a secondary control signal for actuating the corresponding electromechanical secondary actuator based on the theoretical deceleration preset value generated in the pilot system.

Description

Technical Field

[0001] The invention relates to a braking system in an at least partially autonomous vehicle. Background Art

[0002] In the case of at least partially autonomous vehicles, the brake system must be designed for autonomous brake pressure build-up and autonomous driver assistance control (such as ABS functions or ESP functions). According to the system characteristics, the brake system must perform braking tasks and steering tasks in the event of a fault and automatically bring the vehicle to a safe stop and keep it stationary. For this purpose, the brake system is equipped with a primary brake control system and a redundant secondary brake control system.

[0003] In a brake system of this type, the main brake control system has a main control unit and an electromechanical main actuator for each wheel for actuating the wheel brakes. Based on a theoretical deceleration setpoint value generated in a pilot system (e.g., a driver assistance system) and / or a theoretical deceleration setpoint value generated on the vehicle side by means of a brake pedal, the main control unit generates a main control signal in order to actuate the corresponding electromechanical main actuator.

[0004] In the prior art, the auxiliary brake control system is equipped with reduced functionality compared to the main brake control system. Therefore, in the event of a brake system failure, highly automated driving functions can only be used under driving conditions that do not require high lateral dynamics, for example. Therefore, use on highway sections is possible. However, this is limited by the turning radius of the highway, which must be as large as possible, or by good road conditions. Likewise, the function is limited in terms of maximum speed. During normal operation, the maximum speed for level 3 or level 4 automated driving is 130 km / h. When using the auxiliary brake control system, the maximum speed is currently limited to 80 km / h. In addition, in current vehicles, the parking lock function is integrated into the transmission structure of the vehicle in a simple way in terms of component technology.

[0005] DE 10 2017 211 955 A1 discloses a brake system with an additional module. DE 10 2011 120 614 A1 discloses a drive train with a hydrodynamic retarder. DE 195 43 583 C1 discloses a brake pressure control device for a road vehicle. Summary of the invention

[0006] The object of the present invention is to provide a brake system in an at least partially autonomous vehicle, whose auxiliary brake control system has an increased functionality compared to the prior art.

[0007] The invention relates to a braking system in an at least partially autonomous two-track vehicle with a front axle and a rear axle. The braking system has a wheel brake for each wheel, to which a main brake control system and a redundant secondary brake control system are assigned. The main brake control system comprises a main control unit and, for each wheel, an electromechanical main actuator for actuating the wheel brake. In normal driving operation, the main control unit generates a main control signal based on a theoretical deceleration setpoint generated by a pilot system or generated on the driver's side by means of a brake pedal, with which the corresponding electromechanical main actuator is actuated.

[0008] In order to improve functionality, the secondary brake control system has a secondary controller independent of the main controller and an electromechanical secondary actuator independent of the main actuator for each wheel. The secondary controller generates a secondary control signal based on a theoretical deceleration preset value generated in the pilot system and / or generated on the driver's side by means of a brake pedal, and uses the secondary control signal to control the corresponding electromechanical secondary actuator.

[0009] Therefore, the braking system according to the present invention is handled with a dry system topology in the absence of brake fluid. The conversion of the braking force is implemented on the wheel brakes by an electromechanical actuator that works in a hydraulic-free manner. The input signal of the driver's braking desire can be detected with the help of a pedal simulation unit. The redundant sensor integrated in the pedal simulation unit converts the mechanical movement of the brake pedal into an electrical signal. The signal is sent to the main controller and the auxiliary controller via simple wiring. The two controllers can be supplied with electrical energy via a redundant onboard power system and a dual design of wiring. Similarly, each controller can obtain the wheel speed of each wheel via a redundant speed sensor and a dual signal line. In addition, the two controllers can be connected to a redundant bus system via a bus line of a respective dual design. In addition, a redundant bus line (hereinafter usually a connecting signal line) for information transmission between the two controllers can be provided.

[0010] The control of the electromechanical main actuator and the secondary actuator on the wheel is implemented by means of a controller. Here, the controller is responsible for the control of a total of four actuators.

[0011] Each of the actuators is integrated into a different brake caliper. The actuator is a simple regulator that is controlled by an operating current that is switched by a control unit. No components for processing information or operating current are integrated into the actuator.

[0012] According to the invention, a more efficient backup stage is achieved by designing the dry brake system compared to the prior art. The networking of the system components of the primary and secondary brake control systems enables lateral stability of the vehicle even in the event of a fault. The improved dynamic characteristics overall enable faster deceleration in the event of a fault. A parking lock installed in a gearbox of the vehicle can also be omitted.

[0013] According to the invention, the dry system concept uses a double integration of components for protecting the auxiliary brake control system. The functions of the system components are designed to be double. In the event of a component failure, a second component is provided to take over the function. Likewise, all system components can be used during normal operation. In an embodiment variant, any of the components can be redundant and only function in the event of a fault.

[0014] If the driver steps on the pedal simulator, an electrical signal is generated and transmitted to two controllers, which process the signal. Accordingly, the driver is completely mechanically disconnected from the brake system. The two controllers control the electromechanical actuators on the wheel brakes that generate the braking force. Due to the networking, the controllers can generate the braking force of each wheel on all four wheels. Tilts caused by uneven buildup of braking force, which is caused by different calculation times of the controllers, can be eliminated. Here, the four wheel brakes are always controlled by one controller, so that the waiting time for building up the braking force is the same. Braking force regulation is ensured by the forward and reverse movement of the motor.

[0015] The dry brake system according to the invention is based on a dual implementation of each system component. When a component fails, a second component exists, which can continue to perform the same function regardless of the failure. The most serious failure of a system component is the failure of a controller. In the event of such a failure, 50% of the functions of the electromechanical actuators are regulated, because these actuators are no longer controlled by the failed controller. However, this means that the deceleration of the vehicle does not necessarily decrease by 50%. The limiting factor for the maximum deceleration of the vehicle is the friction coefficient between the tires and the road surface. The main brake system is designed in such a way that the wheels are always locked during braking. The clamping force of the brake caliper is so large that theoretically a higher braking force can be achieved than can actually be transmitted to the road surface.

[0016] The clamping force of each electromechanical actuator must be designed such that the electromechanical actuator can lock the wheel independently.

[0017] In addition, the auxiliary brake control system according to the present invention can adjust the braking force of each wheel. The functions of longitudinal stability and lateral stability of the vehicle are also guaranteed in the event of a fault in the main brake control system. Compared with the main brake control system, the auxiliary brake control system has no overall restrictions and can realize all functions that the main brake control system can also realize.

[0018] The holding function is implemented by means of an operating current which is applied to at least one electromechanical actuator for each wheel. The braking force is thereby built up and maintained. In addition, the system topology enables protection of the holding function in the event of a fault, since a second electromechanical actuator can be activated for each wheel.

[0019] Different variants are implemented about the parking function. By using the locking function in the electromechanical actuator, the locking of the actuator is basically ensured, and the force used for parking can be maintained. In order to achieve the requirement that the parking force can be transmitted to at least two wheels when a fault occurs in the main brake adjustment system, at least four of the eight electromechanical actuators must have a locking function. In this case, the controller must be able to control at least two actuators for the locking function respectively. Here, the design on which wheels the locking function is integrated is unimportant. However, the optimal structure of the integration of the locking function is to integrate the locking function on each wheel brake of the vehicle. Here, the locking function of the opposing wheel brakes is controlled by the controller respectively. As a result, the prior art in the vehicle with a driven axle is surpassed, and the vehicle can park with four wheels instead of two wheels in normal operation. The prior art in the vehicle with all-wheel drive and parking lock is not implemented because the parking lock also acts on four wheels in these vehicles. In addition, in this prior art, the force flow is realized by form locking and force locking.

[0020] In the event of a serious fault, i.e. a controller failure, the possibility of transmitting the parking force via both wheels is also provided. The parking force acts on the wheels of the front axle and the rear axle respectively. In addition, the parking force always acts on the right and left wheels. This can reduce the influence of road conditions.

[0021] The important aspects of the present invention are shown again in detail below: Therefore, preferably, the main controller and the secondary controller can be designed in the same structure and in the same function. In the same way, the main actuator and the secondary actuator can also be designed in the same structure and in the same function.

[0022] Preferably, the brake pedal can be a component of a pedal simulation unit having at least one pedal sensor. The pedal simulation unit can convert a mechanical pedal movement into an electrical pedal signal, which is a setpoint deceleration value generated on the driver's side.

[0023] In order to further improve the system safety, preferably, a main onboard power grid and a redundant auxiliary onboard power grid are provided. The main onboard power grid and the auxiliary onboard power grid can supply power to the main controller and the auxiliary controller respectively independently of each other.

[0024] In one technical solution, each wheel can be equipped with a main speed sensor and a secondary speed sensor. The main speed sensor is connected to the main controller signal. In the same way, the secondary speed sensor is connected to the secondary controller signal.

[0025] Preferably, the pilot system is connected to the main controller signal through the main signal line. Independently of this, the pilot system can be connected to the sub-controller signal through another sub-signal line.

[0026] In a first embodiment variant, only the main brake control system can be used in normal driving operation, while the auxiliary brake control system is deactivated. Preferably, the main control can be connected to the auxiliary control system via a connecting signal line. Status information can be exchanged between the two controllers via the connecting signal line. If a fault situation in the main brake control system is diagnosed in the main control, a fault signal is generated, with which the auxiliary control system can be activated via the connecting signal line. In this case, the auxiliary brake control system assumes the conversion of the theoretical deceleration preset value instead of the main brake control system.

[0027] In an alternative operating mode, the main brake control system and the auxiliary brake control system can already be used in normal driving operation. Therefore, in this case, the two brake control systems already work in a parallel operation mode in normal driving operation.

[0028] In a further development of the invention, at least one of the electromechanical main actuators and at least one of the electromechanical secondary actuators can each have a locking function, by means of which the actuators lock the associated wheels by brake actuation in a parking situation. Preferably, all actuators are equipped with such a locking function. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] According to the following Figure 1 An embodiment of the present invention is described.

[0030] List of reference numerals:

[0031] 1 Wheel brake

[0032] 2 Brake calipers

[0033] 3.5 Main actuator and auxiliary actuator

[0034] 7 Brake disc

[0035] 9 Main Controller

[0036] 11 Main speed sensor

[0037] 13 Sub-controller

[0038] 15. Auxiliary speed sensor

[0039] 17 Pilot system

[0040] 19 Brake pedal

[0041] 21. Pressure sensor

[0042] 23 Travel sensor

[0043] 25 Main signal line

[0044] 27 Auxiliary signal line

[0045] 29 Connecting the signal line

[0046] 31 Main onboard power grid

[0047] 33 Auxiliary onboard power supply

[0048] S F Fault signal

[0049] V P 、V B Theoretical deceleration preset value

[0050] y1, y2 adjustment signal

[0051] BRS1 main brake regulation system

[0052] BRS2 auxiliary brake adjustment system DETAILED DESCRIPTION

[0053] exist Figure 1 , a schematic block diagram of a brake system of a two-track autonomous vehicle with a front axle and a rear axle is shown. Accordingly, each of the two front wheels VL, VR and each of the two rear wheels HR, HL is respectively equipped with a wheel brake 1. The wheel brake 1 has a brake caliper 2, which can be acted upon by an electromechanical main actuator 3 and an electromechanical secondary actuator 5, whereby the brake caliper 2 with its brake lining (not shown) is pressed against a brake disk 7 of the wheel brake 1. The electromechanical main actuator 3 is a component of a main brake control system BRS1, while the electromechanical secondary actuator 5 is a component of a secondary brake control system BRS2. All actuators 3, 5 operate in a hydraulically non-hydraulic manner.

[0054] The main brake regulation system BRS1 Figure 1The main control unit 9 and a total of four electromechanical main actuators 3 are formed, each of which is assigned to a wheel brake 1. The main control unit 9 is also signal-connected to a main rotational speed sensor 11 for each wheel VL, VR, HR, HL.

[0055] The redundant auxiliary brake control system BRS2 has the same components as the main brake control system BRS1. Accordingly, the auxiliary brake control system BRS2 is composed of an auxiliary controller 13 and an electromechanical auxiliary actuator 5 for each wheel. In addition, the auxiliary controller 13 is signal-connected to the auxiliary speed sensor 15 provided for each wheel.

[0056] In normal driving operation, based on the theoretical deceleration preset value V generated in the pilot system 17 (eg, a driver assistance system having ABS function and EPS function), the deceleration time is set to 0. P and / or a theoretical deceleration preset value V generated on the driver's side by means of the brake pedal 19 B A main control signal y1 is generated in the main control unit 9. The main control signal y1 is used to control the corresponding electromechanical main actuator 3 in order to perform different braking tasks or steering tasks.

[0057] The main controller 9 and the slave controller 13 are powered independently of each other by a main onboard power supply 31 and a redundant slave onboard power supply 33 , respectively.

[0058] exist Figure 1 In the embodiment, the brake pedal 19 is a pedal simulation unit having a pressure sensor 21 and a travel sensor 23. The pedal simulation unit converts the pedal movement detected by the two sensors 21, 23 into an electrical pedal signal corresponding to the theoretical deceleration preset value V generated on the driver side. B .

[0059] exist Figure 1 In the embodiment, the pilot system 17 is also connected to the main controller 9 by a main signal line 25, and the pilot system 17 is connected to the sub-controller 13 by a sub-signal line 27 independent of the main signal line. In addition, the two controllers 9, 13 are connected to each other by means of a connecting signal line 29. Status information can be exchanged between the two controllers 9, 13 via the connecting signal line 29.

[0060] In normal driving operation, in the embodiment variant shown, only the main brake control system BRS1 is used, while the redundant secondary brake control system BRS2 is deactivated. If the diagnostic module in the main control unit 9 detects a fault in the main brake control system BRS1, a fault signal S is generated. F The fault signal is read by the main controller 9 to the auxiliary controller 13 via the connecting signal line 29. Then, the auxiliary brake regulation system BRS2 assumes the theoretical deceleration preset value V P 、VB conversion.

[0061] As an alternative to this, in normal driving operation both the main brake control system BRS1 and the secondary brake control system BRS2 can be used, so that both brake control systems operate in parallel operation.

[0062] Furthermore, the electromechanical main actuator 9 and the secondary actuator 13 each have a locking function, by means of which the corresponding actuator 3 , 5 locks the associated wheels by actuating the brakes in a parking situation.

Claims

1. A braking system in an at least partially autonomous vehicle, the braking system comprising a wheel brake (1) for each wheel (VR, VL, HR, HL), the wheel brake being equipped with a primary brake control system (BRS1) and a redundant secondary brake control system (BRS2), wherein: A main brake control system (BRS1) has a main control unit (9) and, for each wheel (VR, VL, HR, HL), an electromechanical main actuator (3) for actuating a wheel brake (1), wherein based on a theoretical deceleration setpoint value (V P ) and / or a theoretical deceleration preset value (V B ), the main controller (9) generates a main regulating signal (y1) for controlling the corresponding electromechanical main actuator (3), It is characterized in that The auxiliary brake regulation system (BRS2) has an auxiliary controller (13) independent of the main controller (9) and an electromechanical auxiliary actuator (5) independent of the main actuator (3) for each wheel (VR, VL, HR, HL), and the auxiliary controller (13) is based on a theoretical deceleration preset value (V P ) generates a secondary control signal (y2) for controlling a corresponding electromechanical secondary actuator (5), The pilot system (17) is a driver assistance system. A connecting signal line (29) is provided between the main controller (9) and the auxiliary controller (13), through which status information can be exchanged between the controllers (9, 13). In the event of a fault in the main brake regulation system (BRS1), the main controller (9) generates a fault signal (S F ), the fault signal can be used to activate the secondary controller (13) via the connecting signal line (29), thereby replacing the main brake regulation system (BRS1), and the secondary brake regulation system (BRS2) assumes the theoretical deceleration preset value (V B 、V P ) conversion.

2. The braking system according to claim 1, characterized in that: The brake pedal (19) is a component of a pedal simulation unit having at least one pedal sensor (21, 23), which converts a mechanical pedal movement into an electrical pedal signal, which is a theoretical deceleration preset value (V B ).

3. The braking system according to claim 1 or 2, characterized in that: A main onboard power grid (31) and a redundant auxiliary onboard power grid (33) are provided, and the main onboard power grid and the redundant auxiliary onboard power grid respectively supply power to a main controller (9) and an auxiliary controller (13) independently of each other.

4. The braking system according to claim 1 or 2, characterized in that: Each wheel (VR, VL, HR, HL) is equipped with a main speed sensor (11) and a secondary speed sensor (15), and the main speed sensor and the secondary speed sensor are respectively connected to a main controller (9) and a secondary controller (13) by signals.

5. The braking system according to claim 1 or 2, characterized in that: The pilot system (17) is signal-connected to the main controller (9) via a main signal line (25), while the pilot system (17) is signal-connected to the sub-controller (13) via a sub-signal line (27) independent of the main signal line.

6. The braking system according to claim 1 or 2, characterized in that: During normal driving operation, both the primary brake control system (BRS1) and the secondary brake control system (BRS2) are used, so that the two brake control systems (BRS1, BRS2) operate in parallel operation.

7. The braking system according to claim 1 or 2, characterized in that: At least one of the electromechanical main actuator (3) and the electromechanical secondary actuator (5) has a locking function, by means of which the actuator with the locking function locks the associated wheels (VR, VL, HR, HL) by brake actuation in a parking situation.

8. The braking system according to claim 1 or 2, characterized in that: The main controller (9) and the sub-controller (13) are of the same structure, and / or the main actuator (3) and the sub-actuator (5) are of the same structure.

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