Electro-hydraulic brake system

Abstract

The invention provides an electro-hydraulic brake system. A braking system configured for an unmanned vehicle. The system comprises a main controller, a first main unit provided with a first controller and a second main unit provided with a second controller. The first main unit includes a first brake circuit and a second brake circuit each including one or more valves configured to operate a first number of wheel brakes. The second main unit includes a third brake circuit and a fourth brake circuit each configured to operate a second number of wheel brakes, the third brake circuit being selectively fluidly connected to the first brake circuit, and the fourth brake circuit being selectively fluidly connected to the second brake circuit. The second controller is configured to command the third brake circuit and the fourth brake circuit to operate the first number of wheel braking portions and the second number of wheel braking portions in response to a malfunction of the first controller.

Description

Technical Field

[0001] The present disclosure relates to brake systems, and in particular to electro-hydraulic brake systems configured for autonomous and semi-autonomous vehicles. Background Art

[0002] Certain vehicles may include a brake-by-wire (BBW) architecture to brake the vehicle. The BBW architecture may include a vehicle master cylinder that may be operated in a normal mode in which the master cylinder is completely isolated from the wheel brake and connected to a pedal feel simulator that replicates the force, travel, and damping of a conventional braking system, or may be operated in a fallback mode in which the master cylinder is braked directly by the driver of the vehicle. The brake pedal travel and / or force, together with the measured hydraulic brake pressure, is used by the system as an input signal to an electronic control unit. The electronic control unit, in turn, sends a signal to a pressure supply unit based on the measured hydraulic pressure, which may be composed of a high-efficiency brushless motor and a ball screw assembly that displaces one or more pistons. Thus, the applied pressure determines the speed and force at which the brakes are applied, with the goal of replicating the driver's intended instantaneous deceleration of the vehicle. Summary of the invention

[0003] The present disclosure provides an electro-hydraulic brake system configured for autonomous and semi-autonomous vehicles. The brake system may include one or more main units (e.g., two main units), e.g., a first unit and a second unit, each of which is configured to operate one or more wheel brakes. The two main units may each include an electronic control unit (ECU), which may receive commands from a dedicated CAN to control the desired braking level provided by the first unit and the second unit, and each unit may be interconnected by one or more crossover connections to achieve redundancy when one of the two units fails to operate as expected. A pressure supply unit (PSU) may be provided in each unit, and each PSU may be fluidly connected to one or more control valves (e.g., twelve control valves), some of which may be normally closed and some of which may be normally open.

[0004] According to another aspect of the present disclosure, the PSUs may be substantially identical to one another. As an example, each PSU includes an identical motor, ball screw, and piston configured to translate within a hydraulic bore capable of providing brake pressure to a wheel brake.

[0005] According to another aspect of the present disclosure, the brake system may be configured to operate in multiple modes, such as basic brake modulation, ABS release, in-stop ECU fault, and basic brake fault.

[0006] According to another aspect of the present disclosure, an electro-hydraulic brake system for an unmanned vehicle is provided. The brake system may include a main controller, a first main unit and a second main unit. The first main unit may be configured to operate a right front wheel brake portion and a left front wheel brake portion, and the first main unit may be provided with a first pressure supply unit (PSU), a first brake circuit, a second brake circuit and a first controller. The second main unit may be configured to operate a left rear wheel brake portion and a right rear wheel brake portion, and may be provided with a second pressure supply unit (PSU), a third brake circuit, a fourth brake circuit and a second controller. The first brake circuit may be configured to receive a pressurized fluid from the first PSU, and the first brake circuit may include a first plurality of valves, and the first plurality of valves are collectively configured to provide a pressurized fluid to the right front wheel brake portion and receive a pressurized fluid from the right front wheel brake portion. The second brake circuit may be configured to receive a pressurized fluid from the first PSU, and the second brake circuit may include a second plurality of valves, and the second plurality of valves may be collectively configured to provide a pressurized fluid to the left front wheel brake portion and receive a pressurized fluid from the left front wheel brake portion. The first controller may communicate with the main controller. The third brake circuit may be configured to receive pressurized fluid from the second PSU, the third brake circuit may include a third plurality of valves, the third plurality of valves may be collectively configured to provide pressurized fluid to and receive pressurized fluid from the right rear wheel brake portion, and the third brake circuit may be selectively fluidly connected to the first brake circuit. The fourth brake circuit may be configured to receive pressurized fluid from the second PSU. The fourth brake circuit may include a fourth plurality of valves, the fourth plurality of valves may be collectively configured to provide pressurized fluid to and receive pressurized fluid from the left rear wheel brake portion, and the fourth brake circuit may be selectively fluidly connected to the second brake circuit. The first controller may be configured to: in response to receiving a first basic brake modulation command from the main controller, activate the first plurality of valves and the second plurality of valves to apply and release the right front wheel brake portion and the left front wheel brake portion. The second controller may be configured to: in response to receiving a second basic brake modulation command from the main controller, activate the third plurality of valves and the fourth plurality of valves to apply and release the right rear wheel brake portion and the left rear wheel brake portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 A schematic diagram of a known brake-by-wire (BbW) architecture is illustrated.

[0008] Figure 2 A schematic diagram of a known BbW architecture modified for level four of the SAE driving automation levels is illustrated.

[0009] Figure 3 A schematic diagram of a level four braking system is illustrated in accordance with one or more embodiments.

[0010] Figure 4 The example shows the operation in the basic brake modulation mode. Figure 3 The schematic diagram shown in .

[0011] Figure 5 The example shows the operation of the anti-lock braking system (ABS) in the release mode. Figure 3 The schematic diagram shown in .

[0012] Figure 6 This example shows the operation of the ECU in the stopped fault mode. Figure 3 The schematic diagram shown in .

[0013] Figure 7 The example shows the operation in the basic brake fault mode. Figure 3 The schematic diagram shown in . DETAILED DESCRIPTION

[0014] Embodiments of the present disclosure are described herein. However, it should be understood that the disclosed embodiments are merely examples, and other embodiments may take various and alternative forms. The drawings are not necessarily drawn to scale; some features may be exaggerated or minimized to show the details of specific components. Therefore, the specific structural and functional details disclosed herein should not be interpreted as restrictive, but only as a representative basis for teaching those skilled in the art to adopt the embodiments in various ways. As will be understood by those of ordinary skill in the art, the various features illustrated and described with reference to any one of the drawings may be combined with the features illustrated in one or more other drawings to produce embodiments that are not explicitly illustrated or described. The combination of the illustrated features provides representative embodiments of typical applications. However, for specific applications or implementations, various combinations and modifications of features consistent with the teachings of the present disclosure may be desired.

[0015] The present invention is not limited to the specific embodiments and methods described below, as specific components and / or conditions may of course vary. Furthermore, the terminology used herein is for the purpose of describing specific embodiments of the present invention only and is not intended to be limiting in any way.

[0016] As used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. For example, reference to a component in the singular is intended to include a plurality of components.

[0017] The terms "substantially" or "approximately" may be used herein to describe the disclosed or claimed embodiments. The terms "substantially" or "approximately" may modify a value or relative property disclosed or claimed in the present disclosure. In such cases, "substantially" or "approximately" may mean that the value or relative property it modifies is within ±0%, 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, or 10% of the value or relative property.

[0018] When an element or layer is referred to as being "on," "engaged to," "connected to," or "coupled to" another element or layer, it may be directly on, engaged, connected, or coupled to that other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as being "directly on," "directly engaged to," "directly connected to," or "directly coupled to" another element or layer, there may be no intervening elements or layers. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.). The term "and / or" includes any and all combinations of one or more of the associated listed items.

[0019] Although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms can only be used to distinguish an element, component, region, layer or section from another region, layer or section. Terms such as "first", "second" and other numerical terms do not imply order or sequence when used in this article unless the context clearly indicates. Therefore, without departing from the teaching of the example embodiments, the first element, component, region, layer or section discussed below can be referred to as the second element, component, region, layer or section.

[0020] For ease of description, spatially relative terms such as "inside," "outside," "beneath," "below," "lower," "above," "upper," etc. may be used to describe the relationship of one element or feature to another element or feature as illustrated in the figure. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the accompanying drawings. For example, if the device in the figure is turned over, an element described as being "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the example term "below" may encompass both above and below orientations. The device may be oriented in other ways (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein are interpreted accordingly.

[0021] Figure 1A schematic block diagram of a brake-by-wire (BbW) system 10 in a vehicle, such as a car, is shown, and includes a plurality of wheel brakes 22a, 22b, 22c, 22d, each having a corresponding actuator, such as a hydraulic cylinder. The basic brake-by-wire (BBW) architecture is now well-accepted in the automotive industry. The vehicle's master cylinder 30 directly applies one or more of the wheel brakes 22a, 22b, 22c, 22d in a fail-safe mode, or is isolated from the wheel brakes 22a, 22b, 22c, 22d and connected to a pedal feel simulator (PFE) 39 that replicates the force, travel, and damping of a conventional brake system. The brake pedal travel and / or force and / or brake pressure are used by the system 10 as input signals to a brake electronic control unit (ECU) 90. It in turn sends appropriate signals to a pressure supply unit (PSU) assembly 40. The PSU assembly 40 may include a high-efficiency brushless motor and ball screw 60 assembly that displaces one or more PSU pistons, which may be considered an electric master cylinder. The master cylinder 30 and / or the PSU assembly 40 may be coupled to the wheel brake parts 22a, 22b, 22c, 22d via a series of control valves 15, which may include apply valves and release valves (not shown) for each of the wheel brake parts 22a, 22b, 22c, 22d to provide functions such as anti-lock braking (ABS), electronic traction control, and the like.

[0022] The brake pedal input defines the driver's intent, which determines how quickly and how hard the brakes are applied, with the goal of replicating the feel of a conventional vacuum booster brake system. The brake ECU 90 may also send a signal to a drive control unit (DCU) 18, which may also be referred to as a powertrain control module (PCM) 18, to use one or more electric motors to decelerate the vehicle in regenerative mode.

[0023] Figure 2 A schematic diagram of an exemplary BBW architecture 12 is shown, modified for level 4 or level 5 of the SAE levels of driving automation. The Society of Automotive Engineers originally introduced SAE J3016 TM Recommended Practice: Classification and definitions of terms related to driving automation systems for road motor vehicles, commonly referred to as SAE driving automation levels TM , which includes levels 0 to 5 of driving automation. SAE Level 4 no longer requires a driver, and many operations are performed by the braking system (i.e., the autopilot 16), including: (1) monitoring the driving environment; (2) performing vehicle steering, acceleration, and deceleration; and (3) fail-safe performance. Therefore, the master cylinder 30 and the pedal feel simulator 39 can be eliminated.

[0024] Thus, the vehicle is guided by an autopilot which measures the external environment and then executes a programmed destination or route. However, at Level 4, the capabilities of the system are limited by factors such as the maximum permissible vehicle speed and the permissible operating area. At Level 5, these limitations are removed and the vehicle must be able to self-navigate anywhere a human can drive. However, in order to meet the necessary brake system fail-backup requirements at Level 4, there must be a second independent system that can safely stop the vehicle and allow it to continue with some degree of reduced operation. This can include maintaining dynamic rear ratios and some level of axle-based ABS.

[0025] Figure 3 A schematic diagram of an exemplary level 4 braking system according to one or more embodiments is shown. The braking system includes two braking units identified as Main-1 and Main-2, and each braking unit is connected through a communication network (e.g., a controller area network (identified as "autopilot dedicated CAN")) via a first ECU 48a of the first main unit Main-1 and a second ECU 48b of the second main unit Main-2 (collectively referred to as ECU 48). The dedicated CAN 16 can provide relatively fast uninterrupted communication between the two units Main-1 and Main-2. Each of the units Main-1 and Main-2 is connected to a plurality of brake parts, including a right front brake part 22a, a left front brake part 22, and a right rear brake part 22c and a left rear brake part 22d. The ECUs 48 of the two braking units Main-1 and Main-2 can receive commands from the dedicated CAN 16 to control the desired or commanded braking level provided by the first unit Main-1 and the second unit Main-2.

[0026] ECU 48 may include a microprocessor or central processing unit (CPU) that communicates with various types of computer-readable storage devices or media. For example, computer-readable storage devices or media may include volatile and non-volatile storage in read-only memory (ROM), random access memory (RAM), and keep-alive memory (KAM). KAM is a persistent or non-volatile memory that can be used to store various operating variables when the CPU is powered off. Computer-readable storage devices or media may be implemented using any of a variety of known memory devices (such as PROM (programmable read-only memory), EPROM (electric PROM), EEPROM (electrically erasable PROM), flash memory, or any other electrical, magnetic, optical, or combined memory device capable of storing data), some of which represent executable instructions used by ECU 48 when controlling the first unit master 1 and the second unit master 2, respectively. Although ECU 48 may be composed of substantially similar or identical hardware (e.g., the memory devices cited above), ECU 48a of the first unit master 1 may execute instructions (e.g., software) different from instructions of ECU 48b of the second unit master 2.

[0027] As will be described in more detail below, each of the unit masters 1 and 2 may include a plurality of valves and a plurality of ports. Because the valves and ports of the first unit master 1 may be the same or substantially the same as those of the second unit master 2, for the sake of brevity, only the valves and ports of the first unit master 1 will be described. The plurality of valves may include a release valve right rear 20a, a release valve left rear 20b, a release valve right front 28a, a release valve left front 28b, an apply valve right front 14a, an apply valve left front 14b, an apply valve right rear 32a, and an apply valve left rear 32b. The plurality of ports may include a first master cylinder inlet port 36, a second master cylinder inlet port 38, a left front wheel port outlet 64, a right front wheel port outlet 66, a left rear port outlet 68, and a right rear wheel port outlet 70.

[0028] The first unit main 1 includes a fluid reservoir 50 that holds hydraulic fluid to the first brake circuit BC1 and the second brake circuit BC2. A fluid level sensor such as a float switch monitors the level of the hydraulic fluid in the fluid reservoir 50. The pressure supply unit "PSU" includes the same motor 44, a ball screw 60 and a piston 62, which is configured to translate within a hydraulic bore to supply hydraulic fluid from the fluid reservoir 50 to the first brake circuit BC1 and the second brake circuit BC2. The motor 44 can be a three-phase motor that is configured to receive power through the motor stator lead 46.

[0029] An exemplary PSU assembly is provided in Applicant's U.S. Patent Publication No. 2023 / 0119335, which is incorporated herein by reference. The PSU 40 can draw fluid from a return fluid channel that is connected to a fluid reservoir 50 and maintained at or near ambient atmospheric pressure. In one or more embodiments, a PSU refill check valve 42, which can be a normally closed check valve, can be operable to allow the PSU 40 to draw fluid from the reservoir 50. A rotor angle sensor 56 can be coupled to the electric motor 44 to determine the position of the rotor in the motor, and thereby determine the position of the PSU 40. A pressure and temperature sensor 34 can be disposed in the PSU fluid channel 52 and configured to measure the temperature and pressure therein.

[0030] The PSUs 40 can be substantially identical to each other so that two PSUs 40 can supply pressure to the wheel brakes simultaneously, which can enable the use of the braking system on larger (e.g., non-passenger) vehicles. The first unit main 1 and the second unit main 2 are interconnected by multiple cross connections, which can achieve redundancy if one of the two units fails to operate as expected. In other words, if one unit fails, the other unit can still provide full functionality of ABS and electronic stability control (ESC) at each of the four wheel brakes. Each wheel can be powered by a drive motor 44, which can be configured to provide regenerative braking in certain circumstances. In addition to the drive motor M, each wheel may include an electric parking brake 54.

[0031] The first pressure supply unit valve 26a and the second pressure supply unit valve 26b may each be a normally closed control valve that may be arranged in parallel with each other. The inlets of the first supply unit valve 26a and the second supply unit valve 26b may be fluidly connected to the outlet of the PSU 40 through the PSU fluid channel 52. The outlet of the first supply unit valve 26a may define a first brake circuit BC1, and the outlet of the second supply unit valve 26b may define a second brake circuit BC2.

[0032] The first master cylinder isolation valve 24a and the second master cylinder isolation valve 24b may be normally open control valves that may be arranged in parallel with each other. The outlets of the first master cylinder isolation valve 24a and the second master cylinder isolation valve 24b may be fluidly connected to the outlets of the first supply unit valve 26a and the second supply unit valve 26b, respectively. The inlets of the first master cylinder isolation valve 24a and the second master cylinder isolation valve 24b in Master 1 may be fluidly connected to the wheel port outlets of the second master unit Master 2, such as the right front wheel port outlet 66 and the left rear wheel port outlet 68. The inlets of the first master cylinder isolation valve 24a and the second master cylinder isolation valve 24b of Master 2 may be fluidly connected to the wheel port outlets of the first master unit Master 1, such as the left front wheel port outlet 64 and the right rear wheel port outlet 70, to complete the hydraulic cross connection between the two master units. Such a hydraulic cross connection may be directed through the first master cylinder inlet port 36 and the second master cylinder inlet port 38, respectively.

[0033] A plurality of apply valves and release valves may connect the first brake circuit BC1 and the second brake circuit BC2 to the wheel brake portions 22a, 22b, 22c, 22d to selectively control the fluid flow between a corresponding one of the wheel brake portions and an associated one of the two brake circuits BC1, BC2. As an example, the first brake circuit BC1 may include an apply valve right front 14a, an apply valve left front 14b, a release valve right front 28a, and a release valve left front 16b. The second brake circuit BC2 may include an apply valve right rear 32a, an apply valve left rear 18b, a release valve right rear 20a, and a release valve left rear 19b. The apply valves 14, 32 and the release valves 20, 28 may be collectively referred to as anti-lock braking system (ABS) valves for use in such ABS. However, the apply valves 14, 32 and the release valves 20, 28 may be used for other functions, such as for traction control and / or for torque vectoring control.

[0034] Figure 4 Shows Figure 3 Schematic diagram of the illustrated braking system when operating in the basic brake modulation mode. During the basic brake modulation mode, during each application of the brake, all eight ABS valves 14a, 14b, 20a, 20b, 28a, 28b, 32a, 32b are actuated in each of the units master 1 and master 2. The front wheel brakes RF, LF are applied and released by the first unit master 1, and the rear wheel brakes RR, LR are applied and released by the second unit master 2.

[0035] Figure 5 Shows Figure 3Schematic diagram of the illustrated braking system when operating in ABS release mode. The ABS release mode can be accomplished via one or more paths. As an example, activation of the release valves 28a, 28b, 20a, 20b can provide an immediate reduction in pressure in the respective fluid reservoirs. Alternatively or in addition, a second fluid path can be formed such that as the volume of each PSU increases, fluid is drawn back into each PSU to reduce the total brake pressure. This increase in PSUs can reduce the total number of replenishments required.

[0036] Figure 6 Shows Figure 3 Schematic diagram of the illustrated braking system when operating in a stop ECU failure mode. As described above, the first unit 1 and the second unit 2 of the braking system provide redundancy if one or more components (e.g., ECU) of one of the units fails to operate as expected. In the illustrated embodiment, the first unit master 1 fails, and therefore, the normally open master cylinder isolation valves 24a, 24b are no longer energized. Therefore, the PSU 40 of the second unit master 2 is configured to pressurize each of the front brake parts RF, LF through the control valves identified by box number 1, box number 2 and box number 3.

[0037] Figure 7 Shows Figure 3 Schematic diagram of the illustrated braking system when operating in a basic brake failure mode. As an example, the basic brake failure mode can be caused by a disconnection or opening between the right front wheel and the apply valve right front 14a and the release valve 28a, resulting in a leak (as shown by the directional arrows). Thus, during the basic brake failure mode of one or more of the front brake parts 22a, 22b, there is no pressure at the fluid connection with the front brake parts RF, LF, as shown by "O". Therefore, braking will only occur at the rear brake parts 22c, 22d and at subsequent stops, each of the master cylinder isolation valves 24a and 24b can continue to be activated to ensure that the first unit master 1 and the second unit master 2 remain isolated from each other.

[0038] As an example, each of the brake units may include a pair of normally closed control valves that may be arranged in parallel with each other. The inlet of the normally closed control valve may be fluidically connected to the outlet of the corresponding PSU of each of the unit master 1 and master 2. The outlet of the PSU and the outlet of the normally open control valve may each define a brake circuit (identified as BC1 and BC2). In one or more embodiments, each brake unit may include a pair of normally open control valves that may be arranged in parallel with each other. The inlet of the normally open control valve may be fluidically connected to the outlet of the normally closed control valve, and the outlet of the normally closed control valve may be fluidically connected to the outlet ports MC1 and MC2 of each of the unit master 1 and master 2.

[0039] Each electric motor of each PSU may include a sensor (e.g., a rotation angle sensor) that may be configured to measure the angular displacement of one or more components of each motor (e.g., a motor rotor) or the linear position of a piston as a function of the pitch of a ball screw 60. Each fluid reservoir may include a fluid level switch 58 configured to actuate in response to the fluid level within the fluid reservoir exceeding or falling below a predetermined threshold. The fluid reservoir may be fluidly connected to the respective PSU.

[0040] In one or more embodiments, the first brake unit main 1 may include two normally open valves fluidically connected in parallel to the normally closed control valve of the brake circuit 1BC1, and one of the two normally open valves may be connected to the individual wheel brake portion of the brake circuit BC1, and the second normally open valve may be connected to the brake outlet port. The second brake circuit BC2 may include two normally closed valves, which may be arranged in parallel with each other and connected to the individual wheel brake portion of the second brake circuit BC2, and the other valve may be connected to the brake portion outlet port.

[0041] The first brake circuit BC1 of the second unit master 2 may include two normally open control valves arranged in parallel and fluidically connected to the normally closed control valve. One of the two normally open valves may be connected to a separate wheel brake portion associated with the first brake circuit BC1 of the second unit master 2. The second brake circuit BC2 of the second unit master 2 may include two normally closed valves arranged in parallel with each other and fluidically connected to an inlet of one of the valves of the separate wheel brake portion of the second brake circuit BC2 of the second unit master 2, and the other valve may be connected to a brake portion outlet port.

[0042] In one or more embodiments, the pressure sensor can be fluidly connected to the outlet circuit of each PSU. The brake system can include multiple fluid connections. As an example, a fluid connection can be provided between the overflow portion of the main brake system storage unit and the auxiliary (e.g., fail-safe) brake system storage unit. Another fluid connection is provided between the brake port of the second brake circuit BC2 of the first unit master 1 and the normally open control valve brake port of the first brake circuit BC1 of the second unit master 2. In another embodiment, another fluid connection can be provided between the normally open control valve brake port of the first brake circuit BC1 of the first unit master 1 and the first brake circuit BC1 of the second unit master 2.

[0043] Although exemplary embodiments are described above, these embodiments are not intended to describe all possible forms covered by the claims. The words used in the specification are descriptive rather than limiting words, and it should be understood that various changes can be made without departing from the spirit and scope of the present disclosure. As mentioned above, the features of various embodiments can be combined to form other embodiments of the present invention that may not be explicitly described or illustrated. Although various embodiments may have been described as providing advantages or being superior to other embodiments or implementations of the prior art relative to one or more desired characteristics, it is recognized by those of ordinary skill in the art that, depending on the specific application and implementation, one or more features or characteristics may be sacrificed to achieve the desired overall system properties. These properties may include, but are not limited to, cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, applicability, weight, manufacturability, ease of assembly, etc. Therefore, any embodiment is described as less ideal than other embodiments or implementations of the prior art in terms of one or more characteristics, and these embodiments do not exceed the scope of the present disclosure and may be desirable for specific applications.

[0044] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 665,139, filed on June 27, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. An electro-hydraulic brake system for an unmanned vehicle, wherein the unmanned vehicle is provided with a plurality of wheel brake parts, and the brake system comprises: a main controller configured to control a driving operation of the unmanned vehicle; A first master unit, wherein the first master unit is configured to operate a first number of the plurality of wheel brakes when operating in a normal mode, the first master unit comprising: a first controller configured to control a first pair of wheel brakes among the plurality of wheel brakes in response to receiving a first signal from the main controller, a first pressure supply unit PSU, said PSU being provided with a first PSU outlet, a first pair of normally closed control valves configured to receive fluid from the first PSU outlet, and a first pair of normally open control valves arranged in fluid parallel with each other and configured to receive fluid from outlets of the first pair of normally closed control valves; and a second master unit, wherein the second master unit is selectively fluidly connected to the first master unit and, when operating in the normal mode, the second master unit is configured to operate a second number of the plurality of wheel brakes, the first number of wheel brakes being different from the second number of wheel brakes, the second master unit comprising: a second controller configured to control a second pair of wheel brakes among the plurality of wheel brakes in response to receiving a second signal from the main controller, a second PSU, the second PSU being provided with a second PSU outlet, a second pair of normally closed control valves arranged in fluid parallel with each other and configured to receive fluid from the second PSU outlet, and a second pair of normally open control valves arranged in fluid parallel with each other and configured to receive fluid from outlets of the second pair of normally closed control valves; Wherein, in response to the fluid pressure within the first master unit dropping below a predetermined threshold, the first controller is configured to command the first pair of normally open control valves to close to fluidly isolate the first master unit from the second master unit.

2. The electro-hydraulic brake system according to claim 1, wherein: The first pair of normally closed control valves are arranged in fluid parallel with each other.

3. The electro-hydraulic brake system according to claim 1, further comprising: a first fluid storage provided in the first main unit and configured to supply fluid to the first PSU; a second fluid reservoir disposed in the second main unit and configured to supply fluid to the second PSU; as well as A reservoir line fluidly connects the first fluid reservoir to the second fluid reservoir.

4. The electro-hydraulic brake system according to claim 1, wherein: The first PSU includes an electric motor, a ball screw and a piston, wherein the electric motor is operatively coupled to the ball screw and the piston such that when the electric motor is actuated, the ball screw is actuated to displace the piston and provide pressurized fluid to the first pair of normally closed control valves.

5. The electro-hydraulic brake system according to claim 1, wherein: The first main unit includes a first braking circuit and a second braking circuit, wherein the first braking circuit includes a first normally closed control valve of the first pair of normally closed control valves and a first normally open control valve of the first pair of normally open control valves, wherein the first braking circuit is configured to operate a first wheel braking portion of the multiple wheel braking portions, and the second braking circuit is configured to operate a second wheel braking portion of the multiple wheel braking portions.

6. The electro-hydraulic brake system according to claim 1, wherein: The main controller includes a control area network (CAN) bus.

7. An electro-hydraulic brake system for an unmanned vehicle, the unmanned vehicle being provided with a plurality of wheel brake parts, the brake system comprising: a main controller configured to control a driving operation of the unmanned vehicle; A first master unit, wherein the first master unit is configured to operate a first number of the plurality of wheel brake portions when operating in a normal mode, the first master unit comprising, a first controller configured to control a first braking level in response to receiving a first signal from the master controller, a first pressure supply unit PSU, said PSU being provided with a first PSU outlet, a first pair of normally closed control valves configured to receive fluid from the first PSU outlet, and a first pair of normally open control valves arranged in fluid parallel with each other and configured to receive fluid from outlets of the first pair of normally closed control valves, wherein the first pair of normally open control valves are collectively configured to supply pressurized fluid to the first number of the plurality of wheel brakes; and a second master unit, wherein the second master unit is selectively fluidly connected to the first master unit and, when operating in the normal mode, the second master unit is configured to operate a second number of the plurality of wheel brakes, the first number of wheel brakes being different from the second number of wheel brakes, the second master unit comprising: a second controller configured to control a second braking level in response to receiving a second signal from the primary controller, a second PSU, the second PSU being provided with a second PSU outlet, a second pair of normally closed control valves arranged in fluid parallel with each other and configured to receive fluid from the second PSU outlet, and a second pair of normally open control valves arranged fluidly parallel to each other and configured to receive fluid from outlets of the second pair of normally closed control valves to supply pressurized fluid to a second number of the plurality of wheel brakes, Wherein, the second controller is further configured to: in response to a failure of the first controller, command the second PSU to provide the pressurized fluid to the first pair of normally open control valves to operate the first number of wheel brake parts among the plurality of wheel brake parts.

8. The electro-hydraulic brake system according to claim 7, wherein: The second controller is further configured to command the second pair of normally open valves to close in response to a failure of the first controller.

9. The electro-hydraulic brake system according to claim 8, wherein: The second controller is further configured to command the second pair of normally closed valves to open in response to a failure of the first controller.

10. The electro-hydraulic brake system according to claim 7, further comprising: a first pair of application valves, the first pair of application valves being disposed in the first main unit, the first pair of application valves comprising a first application valve and a second application valve; a second pair of apply valves disposed in the first primary unit and comprising a third apply valve and a fourth apply valve; a third pair of apply valves disposed in the second main unit and comprising a fifth apply valve and a sixth apply valve; as well as a fourth pair of application valves, the fourth pair of application valves being arranged in the second main unit and comprising a seventh application valve and an eighth application valve, Wherein the first apply valve of the first master unit is configured to receive the pressurized fluid from a first normally open control valve of the first pair of normally open control valves and provide the pressurized fluid to a first wheel brake portion of the first number of wheel brake portions.

11. The electro-hydraulic brake system according to claim 10, wherein: The seventh apply valve and the eighth apply valve are arranged in series with respect to fluid flow, wherein the seventh apply valve is fluidly disposed between one of the second pair of normally closed control valves and the eighth apply valve.

12. The electro-hydraulic brake system according to claim 11, wherein: A second normally open control valve of the first pair of normally open control valves is configured to receive the pressurized fluid from the eighth apply valve.

13. The electro-hydraulic brake system according to claim 12, wherein: The fourth apply valve is configured to supply the pressurized fluid to a second wheel brake of the first number of wheel brakes.

14. The electro-hydraulic brake system according to claim 12, further comprising: a first inlet valve, the first inlet valve being disposed in the first main unit, the first inlet valve being directly fluidically connected to the first normally open control valve; as well as a second inlet valve, the second inlet valve being disposed in the first main unit, the second inlet valve being directly fluidically connected to the second normally open control valve, Wherein, the second pair of normally open control valves includes a third normally open control valve and a fourth normally open control valve, and Wherein, the first inlet valve is fluidly disposed between the first normally open control valve and the third normally open control valve.

15. An electro-hydraulic brake system for an unmanned vehicle, the unmanned vehicle being provided with a plurality of wheel brake parts, the brake system comprising: a main controller configured to control a driving operation of the unmanned vehicle; A first main unit, the first main unit is configured to operate a right front wheel brake part and a left front wheel brake part, the first main unit comprising: First pressure supply unit PSU, a first brake circuit configured to receive pressurized fluid from the first PSU, the first brake circuit comprising a first plurality of valves collectively configured to provide pressurized fluid to and receive pressurized fluid from the right front wheel brake portion, a second brake circuit configured to receive pressurized fluid from the first PSU, the second brake circuit comprising a second plurality of valves collectively configured to provide pressurized fluid to and receive pressurized fluid from the left front wheel brake, a first controller, the first controller communicating with the main controller, A second main unit, the second main unit is configured to operate the right rear wheel braking part and the left rear wheel braking part, the second main unit comprising: Second PSU, a third brake circuit configured to receive pressurized fluid from the second PSU, the third brake circuit comprising a third plurality of valves collectively configured to provide pressurized fluid to and receive pressurized fluid from the right rear wheel brake portion, wherein the third brake circuit is selectively fluidly connected to the first brake circuit, a fourth brake circuit configured to receive pressurized fluid from the second PSU, the fourth brake circuit comprising a fourth plurality of valves collectively configured to provide pressurized fluid to and receive pressurized fluid from the left rear wheel brake, wherein the fourth brake circuit is selectively fluidly connected to the second brake circuit, and a second controller, the second controller communicating with the main controller, wherein the first controller is configured to, in response to receiving a first basic brake modulation command from the master controller, activate the first plurality of valves and the second plurality of valves to apply and release the right front wheel brake portion and the left front wheel brake portion, and Wherein, the second controller is configured to: in response to receiving a second basic brake modulation command from the main controller, activate the third plurality of valves and the fourth plurality of valves to apply and release the right rear wheel brake portion and the left rear wheel brake portion.

16. The electro-hydraulic brake system according to claim 15, further comprising: A first isolation valve is fluidly coupled to the first brake circuit and the third brake circuit, wherein the first controller is further configured to command the first isolation valve to close in response to receiving the base brake modulation command.

17. The electro-hydraulic brake system according to claim 16, wherein: The first plurality of valves includes a PSU valve configured to receive the pressurized fluid directly from the first PSU, and wherein the PSU valve is disposed between the first isolation valve and the first PSU.

18. The electro-hydraulic brake system according to claim 17, further comprising: A second isolation valve is fluidly coupled to the second brake circuit and the fourth brake circuit, wherein the first controller is further configured to command the second isolation valve to close in response to receiving the base brake modulation command.

19. The electro-hydraulic brake system according to claim 18, further comprising: a third isolation valve fluidly coupled to the third brake circuit and the first brake circuit, wherein the first isolation valve, the second isolation valve, and the third isolation valve are normally open, and wherein the second controller is further configured to command the third isolation valve to close in response to a failure of the first controller such that the third brake circuit provides pressurized fluid to the first brake circuit.

20. The electro-hydraulic brake system according to claim 19, further comprising: a fourth isolation valve fluidly coupled to the fourth brake circuit and the second brake circuit, wherein the fourth isolation valve is normally open, and wherein the second controller is further configured to command the first, second, third, and fourth isolation valves to close in response to a loss of hydraulic pressure in at least one of the first and second brake circuits.

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