GB2610409A

GB2610409A - Electrohydraulic brake by wire system for autonomous vehicles and fully decoupled applications

Info

Publication number: GB2610409A
Application number: GB2112541.4A
Authority: GB
Inventors: Rodney Thomas Jackson Oliver; William Houlton Paul
Original assignee: Alcon Components Ltd
Current assignee: Alcon Components Ltd
Priority date: 2021-09-02
Filing date: 2021-09-02
Publication date: 2023-03-08
Also published as: GB202112541D0; WO2023031610A1

Abstract

A system and method for controlling a self-sufficient electrohydraulic brake-by-wire system for use in autonomous or semi-autonomous vehicles or fully decoupled braking applications. Upon detection of a fault or failure in the brake-by-wire system (e.g. valve malfunction), a controller switches from a first configuration to a second configuration. In the first configuration, a flow of volume of pressurised fluid from a reservoir 138 via a pump 144 and/or an accumulator 136 to brake calipers 150, 152 is via a primary route 300, in which first solenoid valve 120 is engaged (open) and second solenoid valve 132 is disengaged (closed). In the second configuration, the flow is via a secondary route (400, fig. 4) in which first solenoid valve 120 is disengaged (closed) and second solenoid valve 132 is engaged (open). The two routes are included for redundancy. There may also be a crosslink valve 130 between two brake calipers on the same axle. There may also be a pressure relief valve 134 to relieve excess fluid from the accumulator or pump.

Description

ELECTROHYDRAULIC BRAKE BY WIRE SYSTEM FOR AUTONOMOUS VEHICLES AND

FULLY DECOUPLED APPLICATIONS

TECHNICAL FIELD

The present invention relates to an electrohydraulic brake-by-wire system in autonomous vehicles and, more particularly, to a brake-by-wire system that offers improved safety and redundancy in brake-by-wire systems in an autonomous vehicle in the event of detection of a fault or a failure in the vehicle braking system or braking capability.

BACKGROUND

With the move to fully autonomous vehicles, car manufacturers look to remove elements of human machine interaction such as steering wheels and acceleration/braking pedals completely from the autonomous vehicle whilst keeping vehicle systems robust, safe and reliable. Braking systems in hybrid and electric vehicles are typically performed by electrical control systems that replace some of the more traditional hydraulic and mechanical control systems. This technology is referred to as brake-by-wire technology with various implementations currently being used in order to achieve electronic or electromechanical control of braking in vehicles. It is appreciated that this technology is not limited by the propulsion system of the vehicle and is also present in vehicles with internal combustion engines. Given the safety critical aspect of the vehicle braking system, the implementations of brake-by-wire technology have to include redundancy in the event of a vehicle braking system fault or failure that negatively impacts the braking capability of the vehicle.

A vehicle braking system fault may be defined as an unwanted event occurring within the vehicle braking system that may negatively impact the performance of the braking capabilities of the vehicle. A vehicle braking system failure may be defined as the loss of the ability to stop a vehicle at a predetermined location such as a stop sign or traffic signal. It can also be the uncommanded application of brake pressure causing the vehicle to lose control or stop in a dangerous position. Whilst braking system faults or failure can occur due to many contributing factors such as sudden loss of power, faulty valves or ruptured brake lines causing loss of pressure, there are redundancies in place to ensure continued performance and safety in the event of such system faults or failures. A vehicle power loss refers to events where the power supplied to a vehicle by any source such as low or high voltage energy storages devices, fuel cells, internal combustion engines or alternative sources of power, is suddenly interrupted resulting in no response or control of a vehicle component or a vehicle.

In some known brake-by-wire systems for human controlled or semi-autonomous vehicles, the redundancy in place to protect against system faults or failure, is that such brake-by-wire systems revert to manual driver operation hence requiring the driver to manually engage the brakes or compression of the brake pedal in order to decelerate or stop a vehicle. In the case of a fully autonomous vehicle, due to the lack of human machine interaction, this redundancy action is not an option and thus there is a need to provide a solution to ensure the desired safety performance of a vehicle braking system in the event of a vehicle braking system fault or failure.

To at least address some of the above identified issues, there is provided a solution by the present invention which discloses the employing of an electrohydraulic brake-by-wire system.

It is appreciated that the present invention can also be employed in braking systems of non-autonomous or semi-autonomous vehicles.

SUMMARY

The disclosure is generally directed to a system for controlling a self-sufficient electrohydraulic brake-by-wire system 12 for use in an autonomous or semi-autonomous vehicles or fully decoupled applications comprising; sensors 102, 104, 106, 108, 110, 112, 114 configured to determine the operating state of a brake-by-wire system 12; brake calipers 150, 152, configured to apply a braking force on a wheel hub to slow the rotation of the wheel hub; a reservoir 138 configured to supply a volume of fluid to actuate the brake calipers 150,152 the volume of fluid used to engage and disengage the brake calipers 150, 152; a pump 144 configured to supply a volume of fluid to an accumulator 136 and the brake calipers 150, 152 via the flow of a volume of fluid from the reservoir 138; the accumulator 136 configured to store pressure used to flow a volume of fluid in the brake-by-wire system 12, wherein the accumulator acts as a supplement pressure source in addition to pressure provided by the pump 144 via the flow of fluid or as a backup; a controller 101 configured to couple or decouple the flow of fluid from the reservoir 138 via the pump 144 and/or accumulator 136 to the brake calipers 150, 152, via a primary route 300 or a secondary route 400, wherein primary route 300 and secondary route 400 are independent of each other; and wherein in a first configuration, the controller 101 is configured to allow the flow of fluid via the primary route 300 by engaging the first solenoid valve 120 whilst the second solenoid valve 132 remains disengaged to enable active control of the self-sufficient electrohydraulic brake-by-wire system 12; and wherein in a second configuration, the controller 101 is configured to allow the flow of fluid via the secondary route 400 by keeping the first solenoid valve 120 disengaged and engaging the second solenoid valve 132 to enable the vehicle to stop/slow down; wherein the controller 101 is configured to switch from the first configuration to the second configuration upon detection of a fault or failure of one or more of the sections of the self-sufficient electrohydraulic brake-by-wire system 12.

It should be noted that the initial state of all valves in the present invention are closed or disengaged unless a fault or failure results in the valves remaining open or engaged. It is appreciated that a valve that is currently opened or engaged will remain in its current state if requested to open or engage by the controller 101.

The disclosure is further generally directed to a method for controlling a self-sufficient electrohydraulic brake-by-wire system 12 for use in an autonomous or semi-autonomous vehicles or fully decoupled braking applications comprising; activating a pump 144 configured to supply a volume of fluid to an accumulator 136 and the brake calipers 150, 152 via the flow of a volume of fluid from the reservoir 138; storing a volume of fluid in a reservoir 138 configured to supply a volume of fluid to actuate the brake calipers 150, 152, the volume of fluid used to engage and disengage the brake caliper 150, 152; receiving information from sensors 102, 104, 106, 108, 110, 112, 114 configured to determine the operating state of a brake-by-wire system 12; determining the operating state of the brake-by-wire system 12; selecting to couple the flow of a volume of fluid from the reservoir 138 to the brake calipers 150,152 via the pump 144 and/or the pressurised accumulator 136 to the brake calipers 150,152; wherein in a first configuration, the flow of a volume of fluid is via a primary route 300 wherein the controller 101 engages the first solenoid valve 120 whilst the second solenoid valve 132 remains disengaged; wherein in a second configuration, the flow of pressure is via a secondary route 400 wherein the controller 101 engages the second solenoid valve 132 whilst the first solenoid valve 120 remains disengaged; determining the switch from the first configuration to the second configuration upon detection of a fault of one or more of the sections of the brake-by-wire system 12.

Advantageously such a system allows for a decoupled braking system in which there is provided a redundancy in the event of failure of the overall vehicle braking system or self-sufficient electrohydraulic brake-by-wire system 12. As the electrohydraulic brake-by-wire system 12 is for use in an autonomous or semi-autonomous vehicle system, it is configured to engage such redundancy without the need of human intervention.

Additionally, utilisation of the second solenoid valve 132 provides further redundancy as a last line of defence in the system in the event of a system failure with no other available redundancy options which can be triggered by the vehicle, the brake-by-wire system 12 itself or the corresponding controller 101 on the opposite axle in vehicle configurations where this is present and dependent on vehicle failure mode configurations.

Other aspects of the invention are apparent from the appended claim set. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 depicts an autonomous or semi-autonomous vehicle fitted with two exemplary self-sufficient electrohydraulic brake-by-wire systems, one on each axle, used for autonomous or 5 semi-autonomous vehicles and fully decoupled applications, according to various embodiments described herein.

FIGURE 2 depicts an exemplary architecture of a self-sufficient electrohydraulic brake-by-wire system for autonomous or semi-autonomous vehicles and fully decoupled applications, according to various embodiments described herein.

FIGURE 3 illustrates the configuration of the self-sufficient electrohydraulic brake-by-wire system operating under normal conditions by routing a volume of fluid via the primary route to the brake calipers to provide a braking force, according to various embodiments described herein.

FIGURE 4 illustrates the configuration of the self-sufficient electrohydraulic brake-by-wire system operating under failure conditions by routing a volume of fluid via the secondary route to the brake calipers to provide a braking force, according to various embodiments described herein.

FIGURES 5A-5C illustrates the configuration of the self-sufficient electrohydraulic brake-bywire system operating under various fault conditions by routing a volume of fluid to the brake calipers to provide a braking force, according to various embodiments described herein.

FIGURE 6 depicts a flow chart of an exemplary process of a self-sufficient electrohydraulic brake-by-wire system operating under normal conditions to route a volume of fluid to the brake calipers to provide a braking force, according to various embodiments described herein.

FIGURE 7 depicts a flow chart of an exemplary process of a self-sufficient electrohydraulic brake-by-wire system for operating under failure conditions to route a volume of fluid to the brake calipers to provide a braking force, according to various embodiments described herein.

FIGURE 8 depicts a flow chart of an exemplary process of a self-sufficient electrohydraulic brake-by-wire system operating under fault conditions to route a volume of fluid to the brake calipers to provide a braking force, according to various embodiments described herein.

FIGURES 9-10 depicts a flow chart of an exemplary process of a self-sufficient electrohydraulic brake-by-wire system for switching operation between normal conditions to fault or failure conditions upon detection of a fault or failure, according to various embodiments described herein.

FIGURE 11 depicts an autonomous or semi-autonomous vehicle fitted with an exemplary self-sufficient electrohydraulic brake-by-wire system used for controlling braking of the vehicle across all axles according to various embodiments described herein.

DETAILED DESCRIPTION

The present invention provides a self-sufficient electrohydraulic brake-by-wire system 12 that does not require manual driver operation in an event of brake loss due to a fault or failure in the brake system or loss of power. The benefit provided by such a system is that of an improved safety system that ensures the vehicle braking system is still able to operate safely in an effective manner. Furthermore, given the system described in the present invention is self-sufficient, it eliminates the need for human machine interaction leading to improved safety as there is no dependency on the driver to brake and particularly in autonomous vehicles where means for manual operation such as brake pedals may not be available. Thus such a system is particularly suitable for fully autonomous vehicles where human intervention is eliminated.

The system is also suitable for semi-autonomous or decoupled non-autonomous vehicles where no mechanical or hydraulic link between the driver and the braking system is required.

Additionally, further benefits include the flexibility of vehicle packaging design, reduction in vehicle design complexity and improved vehicle manufacturing flexibility.

Whilst car manufacturers are guided by legislation and regulatory requirements on vehicle safety, additional benefits of having a self-sufficient electrohydraulic brake-by-wire system 12 include improved safety of autonomous vehicles and their occupants by eliminating, or at the least, reducing the risk of potential accidents caused my human error and/or delayed driver reaction in the event of a brake system fault that reverts control to manual operation requiring the driver to react.

It should be noted that whilst the present invention is particularly suited for use in an autonomous vehicle, the present invention improves the vehicle braking system of any autonomous vehicle, as well as semi and non-autonomous vehicles by improving the level of safety offered by the increased level of redundancy present in the system.

The present invention is intended to allow the vehicle to decelerate as commanded, by either driver or autonomous system, with minimal interruption in the event of fault or failure of the braking system. Furthermore, the present invention provides a means for a vehicle to be brought to a safe stop in the event of complete vehicle system damage or failure where other redundancies are ineffective.

Referring to Figure 1, there is shown a vehicle, 10, in accordance with the invention, which includes two self-sufficient electrohydraulic brake-by-wire systems 12 coupled to the brakes 16, 18, of a vehicle and furthermore communicatively coupled to each other as well as an autonomous or semi-autonomous vehicle driving system 14 wherein the self-sufficient electrohydraulic brake-by-wire system 12 can receive commands from the autonomous vehicle driving system 14 to engage or disengage the brakes 16, 18. The vehicle 10 may be any suitable autonomous, semi-autonomous or partially augmented driver controlled vehicle. It should be noted that the present invention is not autonomous itself but works with autonomous or semi-autonomous vehicle systems to provide total failsafe redundancy.

The self-sufficient electrohydraulic brake-by-wire system 12, and its functionality are discussed in further detail below.

With reference to Figure 1, Figure 2 shows the architecture of a self-sufficient electrohydraulic brake-by-wire system 12, also referred to as 100 in Figure 2 (and are used interchangeably), wherein the brake-by-wire system 12 is connected to the either brakes, 16a, 16b or 18a, 18b, via brake calipers 150 and 152 dependent on the system configuration. The self-sufficient electrohydraulic brake-by-wire system 12 includes a reservoir 138 fluidly connected to brake calipers 150 and 152 via a pump 144, a one way valve 154, filter 156, and a series of valves,120, 122, 124, 126, 128, 130, 132, 134, used to control the flow of pressure in self-sufficient electrohydraulic brake-by-wire system 12. The one way valve 154 and filter 156, can be housed in a single one way filter component 148. The accumulator 136 is pressurised when used to store a volume of fluid that is used to actuate the brake calipers 150 and 152 either in combination with the volume of fluid provided by the pump 144 or as a standalone backup. The self-sufficient electrohydraulic brake-by-wire system 12 also includes a printed circuit board (PCB) controller 101 (not shown in figure 1) containing control logic that uses various sensors to determine the status of the system as well as status of various components in order to engage and disengage various electronic servo valves, 120, 122, 124, 126, 128, 130, 132, used to control and deploy stored a volume of fluid from the reservoir 138 and/or the pressurised accumulator 136 to brake calipers 150 and 152. Figure 2 further shows the default state of the brake-by-wire system 12 under normal operating conditions when no faults or failures are present. Pressure sensors 102 through 112 are present to assist in both the control of brake pressure to the axle and to detect/ensure operational mode behaviour and safety. The measurement of pressure outside what is expected by the brake-by-wire system 12 for a given operational mode, either through sensor or valve malfunction will result in the triggering of an appropriate failsafe mode to ensure vehicle safety.

In some embodiments, the control logic housed by the controller 101 can be located in the autonomous vehicle driving system 14 that receives status signals of the various sensors and signals as well as sending brake engage/disengage commands to the brake-by-wire system 12.

In some embodiments, a vehicle with more than one self-sufficient electrohydraulic brake-by-wire system 12 has additional redundancy offered in case a failure of the other brake-bywire system 12.

Figures 3 and 4 show the architecture of a self-sufficient electrohydraulic brake-by-wire system 12 wherein a pump 144 and accumulator 136 are further connected to the brake calipers 150, 152, via a primary route 300, and a secondary route, 400 respectively. The flow of a volume of fluid from the reservoir 140 via the pump 144 and/or deployment of stored volume of fluid by the pressurised accumulator, 136, can be via a primary route 300 as depicted in Figure 3 or a secondary route 400 as depicted in Figure 4, wherein the selection of the appropriate route is determined by the PCB controller 101 and based on the operating conditions of the self-sufficient electrohydraulic brake-by-wire system 12 as determined by the sensors 102, 104, 106, 108, 110, 112, 114, as well as status of various components such as first solenoid valve 120, and pump 144. The benefit of having two separate routes provides an additional level of redundancy to the self-sufficient electrohydraulic brake-by-wire system 12 ensuring the brakes are still able to be operated effectively in the event of a fault or system failure. Furthermore, the use of a secondary route 400, provides a failsafe mode that ensures the brakes can be applied with no actively controlled intervention from the controller 101 and can be applied without any external electrical, mechanical or hydraulic power input to the brake-by-wire system 12. The primary route 300 and the secondary route 400 are decoupled and thus work independently from each other. As the primary route 300 and secondary route 400 are fully decoupled, in the event of failure of either route the self-sufficient electrohydraulic brake-by-wire system 12 the decoupled nature ensures that the self-sufficient electrohydraulic brake-by-wire system 12 is able to function thus providing a further level of safety by allowing an autonomous vehicle driving system 14, as well as other semiautonomous and non-autonomous driving systems to still engage/disengage brake calipers on command and bring the vehicle to a controlled stop or slow the vehicle.

In some embodiments, the pump 144 normally caters to the demands of the self-sufficient electrohydraulic brake-by-wire system 12 to push the brake calipers 150, 152 to a required force equal to the requested braking force by the driving system 14. If the demand generated by the autonomous vehicle driving system 14 is too great, the pump 144 is supplemented by the stored a volume of fluid in the pressurised accumulator 136 in such instances where the force required at an instantaneous time is greater that the pump can respond to in an allotted time.

In some embodiments, a vehicle 10 may consist of one or more self-sufficient electrohydraulic brake-by-wire systems 12 as depicted in Figures 1 and 11. The self-sufficient electrohydraulic brake-by-wire system 12 may consist of two or more independent and mutually supervisory electronic PCB controllers 101 (not shown) that are communicatively connected and wherein the function of one controller is for the purpose of error checking whilst the function of the other controller is for operational status monitoring. In some embodiments, a controller 101 may contain both error checking and operational status monitoring. In vehicle configurations where two or more brake-by-wire systems 12 exist, preferably each system 12 contains a controller 101 housing both error checking and operational status monitoring. This results in an additional level of redundancy being offered in the event of a failure of one brake-by-wire system 12 having a fault or failure with the other brake-by-wire system 12 able to take over functions of the failed system. This provides further improved safety. It should also be noted that the logic determining the operating status of the brake-by-wire system 12 and the trigger to switch to the failsafe mode offered by switching to the secondary route 400 via valve 132 can be within the brake-by-wire system 12 or held independently within the vehicle driving system 14.

In some embodiments, there is also provided an internal backup energy storage device (not shown) such as a battery, super capacitor or the like. The internal backup energy storage device allows for short term operation of self-sufficient electrohydraulic brake-by-wire system 12 to assist in bringing the vehicle to a stop in the case of a fault or failure in the vehicle brake system. In the event of loss of power from the vehicle power source which would negatively impact the performance of the self-sufficient electrohydraulic brake-by-wire system 12 and may potentially render it inactive, the internal backup energy storage device in the self-sufficient electrohydraulic brake-by-wire system 12, provides further redundancy in brake systems on an autonomous vehicle leading to additional safety in case of power failure of an autonomous vehicle. In some embodiments, the backup energy storage device can be external to the brake-by-wire system 12 or a secondary and independent source of electrical power in addition to the internal backup energy storage device. The internal backup energy storage device may be internal or external to the brake by wire system 12.

With reference to Figure 3, the brake-by-wire system 12 under normal operation, hydraulic fluid from the reservoir 140 is pumped under high pressure by pump 144 to charge an accumulator 136 and also to engage brake calipers 150 and 152 via the primary route 300. Accumulator 136 is used as a storage of a high volume of fluid under pressure that is to be deployed when required as controlled by valves 122 and 124 for each individual brake caliper output. The initial state of first solenoid valve 120 is closed or disengaged, and engaging and disengaging first solenoid valve 120 controls the supply of high pressure fluid to valves 122 and 124, thus requiring the brake-by-wire system 12 to be powered before active control of brake pressure is enabled. Valves 126 and 128 are shuttle valves, sprung to favour the active side of the vehicle braking system but are configured to allow both active and passive sides of the vehicle braking system to have command over brake pressure depending on operational mode. The use of the volume of fluid stored in the accumulator 136 also allows for short term operation of the self-sufficient electrohydraulic brake-by-wire system 12, to assist in decelerating or stopping the vehicle 10 in the event of a vehicle power loss or fault or failure of the self-sufficient electrohydraulic brake-by-wire system 12 such as a fault with the pump 144. This provides additional redundancy in the vehicle braking system and further improves safety by still allowing the control of a vehicle's braking system. The accumulator 136, can be used to supplement the pressure provided by the pump 144 during normal operation or in alternative embodiments, the accumulator is solely used as a backup in the event of a fault or failure that renders the pump 144 inoperable. Thus the present invention offers additional levels of redundancy which would be desirable and above normal requirement levels hence resulting in an improvement over existing systems and thus a safer system.

The self-sufficient electrohydraulic brake-by-wire system 12 has various redundancies in place to ensure effective operation of the vehicle braking system should a fault or failure occur.

As described in more detail with reference to figures 5.A and 5.B below, the first level of redundancy of the electro-hydraulic braking system is achieved by the implementation of an electronically controlled crosslink valve 130 for the purpose of controlling the inter link between individual wheel channels on a given axle. This allows the individual direct drive valves 122 and 124 utilised for each wheel during normal operation as shown in Figure 3, to be exploited for redundancy across the axle and allowing normal axle level brake pressure control in the event of failure of an individual valve such as 122, 124, 126 or 128. Under normal operation, crosslink valve, 130, is closed allowing differential pressure to be applied across an axle and hence brake caliper, for brake yaw torque vectoring and/or wheel slip control behaviour. As described with reference to Figures 5.A and 5.5, should a fault occur on valves, 122, 124, 126 or 128 whilst the self-sufficient electrohydraulic brake-by-wire system 12 is coupled to the primary route 300, the crosslink valve 130 provides additional redundancy to ensuring effective and safe operation of the self-sufficient electrohydraulic brake-by-wire system 12. In a further embodiment, the crosslink valve 130 may be replaced by another suitable valve such as a servo valve or any other suitable valve which performs the same functionality.

As described in more detail with reference to Figure 4, the second level of redundancy is achieved by the active control of the vehicle braking system using a secondary route 400 by closing the first solenoid valve 120 of the primary route 300 and utilising the stored volume of fluid in the accumulator 136 under pressure as a passive system to deploy a fixed amount of hydraulic pressure to the vehicle axle to bring the vehicle to a complete stop. In the event of a serious failure in the self-sufficient electrohydraulic brake-by-wire system 12 such redundancy ensures that the vehicle can be safely brought to a halt.

In this mode of operation, normally closed second solenoid valve 132 is energised to release stored brake pressure in accumulator 136 to both wheel channels via shuttle valves 126 and 128, overriding the active side of the self-sufficient electrohydraulic brake-by-wire system 12.

Brake pressure balance across the axle is redundantly ensured by normally open crosslink valve 130. As stored accumulator pressure rapidly applied directly to the wheels may result in wheel locking, the rate of increase is moderated by restrictor 158 and its peak passively reduced by pressure reducing valve 134 releasing excess flow back to the reservoir 138. Flow rates and maximum pressure are specified with the vehicle properties and vehicle safety case.

Therefore, depending on vehicle operating environment, different levels of failsafe deceleration are implemented. For example, in a motorsport environment with a high level of energy absorbent barriers present, a lower level of deceleration may be preferable to a loss of stability, whereas in a low speed public environment, an immediate halt of the vehicle with some risk of wheel locking may be acceptable. The skilled person is able to implement different strategies according to the intended usage of the vehicle.

Depending on vehicle implementation, this failsafe backup can be setup to be triggered by the autonomous vehicle driving system 14, by the controller 101 of the brake-by-wire system 12 itself (and its redundant pair e.g. another controller or brake-by-wire system 12), or by either. This flexibility allows for safe vehicle implementation in a variety of different environments where different vehicle responses to failure may be preferable. For example some vehicle implementations may have insufficient redundancy in the layers above the brake-by-wire system 12 to ensure vehicle safety in the event of a control system fault or failure or electrical failure (ultimately relying on the battery backup powered the brake-by-wire system 12 as the final layer of defence to stop the vehicle) whereas others may have sufficient electrical and control redundancy to exploit the presence of multiple brake-by-wire systems 12 on each controlled axle and avoid stopping or immobilising the vehicle unnecessarily.

The final level of redundancy of the electro-hydraulic brake-by-wire system 12 is achieved by the implementation of an electronically controlled first solenoid valve 120 releasing stored pressure from the accumulator 136 to control the flow of a volume of fluid in the brake circuit via the primary route 300 or the secondary route 400 dependent on the operation status of the electrohydraulic braking system and fault condition. As the route is decoupled from the primary route 300, in the event of failure of first solenoid valve 120, this is implemented. This is controlled passively to a pre-set pressure by means of a pressure regulating valve.

It is appreciated that the sensors and valves mentioned in the exemplary examples can be of the form of any suitable commercially available sensor and valve for the control system to monitor and control the flow and/or pressure of the volume of fluid in the brake system. It will be appreciated that in some embodiments, the sensor may additionally measure other parameters such as temperature. The skilled person would appreciate that any other suitable sensor or valve can be also be used as a replacement.

It is appreciated that responsibility for vehicle stability is held by the overall autonomous vehicle driving system 14 allowing the self-sufficient electrohydraulic brake-by-wire system 12 to be operated purely as an actuation device and individual wheel control to be evolved upwards to the autonomous vehicle driving system 14, allowing better energy management and blending between regenerative and friction braking on an autonomous vehicle.

Figure 3 depicts an exemplary embodiment under normal operating conditions of the present invention using the primary route 300 to actuate the brake calipers.

Pump 144 initially pressurises the accumulator 136 that stores a volume of fluid to be used to actuate the brake calipers 150 and 152 when the self-sufficient electrohydraulic brake-by-wire system 12 is requested to decelerate or stop the vehicle. The self-sufficient electrohydraulic brake-by-wire system 12 controls the flow of a volume of fluid by actuating the first solenoid valve 120 whilst the second solenoid valve 132 remains closed. The first solenoid valve 120 allows the electrohydraulic brake-by-wire system 12 to control the brake calipers 150 and 152 via the primary route 300 under normal operating conditions.

In the primary configuration, the accumulator 136 is fluidly connected to brake calipers 150 and 152 via a first solenoid valve 120. The primary configuration further splits into routes for the left brake caliper 150 and right brake caliper 152 and is fluidly connected via direct drive valve 122 and shuttle valve 126 for the left brake caliper 150 and direct drive valve 124 and shuttle valve 128 for the right brake caliper. The left and right brake caliper routes 180 and 182 are fluidly connected via crosslink valve 130 that balances the difference in pressure between the left and right brake caliper routes. As depicted in Figure 3, the primary configuration refers to the fluidly connected route, i.e. primary route 300, taken by the self-sufficient electrohydraulic brake-by-wire system 12 to actuate the control the brake calipers 150 and 152 under normal operation conditions with no fault present when requested to decelerate or stop the vehicle.

This mode of operation allows the electrohydraulic brake-by-wire system 12 to operate effectively and in a safe manner in case of failure by shutting down the first route and enabling the second route allowing pressure to be applied to the brake calipers via the secondary route 400 resulting in decelerating or stopping the vehicle.

The self-sufficient electrohydraulic brake-by-wire system 12 can be configured to apply a required amount of force dependent on the application. For example, in sports or racing environments, the system can be configured to have a harsh braking setting up thus stopping a vehicle with a significant/ total loss of electrical power or control authority as soon as possible whilst in road or commuter environments, the self-sufficient electrohydraulic brakeby-wire system 12 may be set up to have a soft braking set up that would bring the vehicle to a stop more gradually without compromising vehicle stability.

In a second configuration as depicted in figure 4, the reservoir 138 and pressurised accumulator 136 are fluidly connected to brake calipers 150 and 152 via an alternate operated second solenoid valve 132. The second configuration further splits into routes for the left brake caliper 150 and right brake caliper 152 and is fluidly connected via shuttle valve 126 for the left brake caliper 150 and shuttle valve 128 for the right brake caliper. As depicted in Figure 4, the second configuration refers to the fluidly connected route taken by the self-sufficient electrohydraulic brake-by-wire system 12 to actuate the control the brake calipers 150 and 152 in the event of a fault or failure when requested to decelerate or stop the vehicle.

The return circuit, 168, fluidly connects the primary route 300, and secondary route 400, to a closed reservoir 138, which fluidly connects to reservoir 140. A bleed valve/screw, 146, is fluidly connected to closed reservoir, 138, in order to bleed the self-sufficient electrohydraulic brake-by-wire system 12.

The benefit awarded by such a brake-by-wire system 12 includes improved vehicle and passenger safety due to the number of redundancies present as a risk associated with some existing autonomous or semi-autonomous vehicles is that in the case of catastrophic brake failure, the vehicle may have no means of stopping and would carry on moving under its own inertia, thereby risking a collision or accident.

Figure 4 depicts an exemplary embodiment under failure operating conditions of the present invention using the secondary route 400 to actuate the brake calipers. Pump, 144, initially charges the accumulator, 136, that stores a volume of fluid to be used to actuate the brake calipers 150 and 152 when the self-sufficient electrohydraulic brake-by-wire system 12 is requested to decelerate or stop the vehicle. The self-sufficient electrohydraulic brake-by-wire system 12 controls the release of pressure by actuating the first solenoid valve, 120 whilst the second solenoid valve, 132, remains closed. On attempting to actuate the first solenoid valve, 120, the self-sufficient electrohydraulic brake-by-wire system 12 detects and determines that there is an error with the first solenoid valve, 120.In some embodiments, the detection and determining of errors is performed by the brake-by-wire system 12 and communicated to the vehicle driving system 14. The vehicle driving system 14 then sends a command back to the brake-by-wire system 12 to stop the vehicle. Alternatively the vehicle driving system 14 can itself detect and determine if errors are present and send a command to the brake-by-wire system 12 to stop the vehicle. The self-sufficient electrohydraulic brakeby-wire system 12 then actuates the second solenoid valve, 132, to control the brake calipers 150 and 152 via the secondary route 400.

It should be noted that any fault or failure is communicated to a vehicle driving system 14 which may be independent of the brake-by-wire system 12.

As depicted in Figure 4, if a fault condition is detected, the fault may be minor that allows the self-sufficient electrohydraulic brake-by-wire system 12, to reroute the flow of fluid in the braking system and the vehicle 10 is still considered safe to drive although with reduced range or functionality. Whilst the vehicle 10 can still function in a safe manner, due to the fault conditions, the vehicle 10 may have reduced functionality such as reduced maximum speed or distance of travel, but still allow the vehicle 10 to complete its journey and if necessary, to be driven to a service centre or garage for the fault to be rectified. This is an additional benefit provided by the present invention in that the system design provides further redundancy that facilitates the safe operation of the braking system in a vehicle 10 in the event of a fault.

Thus in such an embodiment, the self-sufficient electrohydraulic brake-by-wire system 12 is still able to maintain a differential pressure to be applied across an axle and hence brake caliper, for brake yaw torque vectoring and/or wheel slip control behaviour despite a fault having occurred. Should either shuttle valve 126 or 128 develop a fault, crosslink valve 130 would engage to open and provide additional redundancy offering yet another level of redundancy in the self-sufficient electrohydraulic brake-by-wire system 12 and ensuring the system is safe and effective.

Figure 4 further depicts a pressure relief valve 134 on the secondary route 400 that returns excess a volume of fluid provided by the pump 144 and/or accumulator 136 back to the reservoir 138 in the event that too much pressure force is supplied to the brake calipers 150,152 in the event of a fault. The technical benefit provided prevents the wheels from locking and provides a smoother braking experience as the brake calipers are not immediately provided with an excess pressure force that would otherwise result in wheel lock.

FIGURE 5A-5C depicts an exemplary embodiment under fault operating conditions of the present invention using the primary route, 300, to actuate the brake calipers 150 and 152. Pump, 144, initially charges the accumulator, 136, that stores a volume of fluid to be used to actuate the brake calipers150 and 152 when the self-sufficient electrohydraulic brake-by-wire system 12 is requested to decelerate or stop the vehicle. The self-sufficient electrohydraulic brake-by-wire system 12 controls the release of pressure by actuating the first solenoid valve, whilst the second solenoid valve, 132, remains closed. The self-sufficient electrohydraulic brake-by-wire system 12 engages the first solenoid valve, 120, in lorder to connect to the primary route 300. The self-sufficient electrohydraulic brake-by-wire system 12 detects and determines that there is an error with either of the valves, 122, 124 on the left or right hand side routes and then actuates the crosslink valve, 130, to open to ensure the pressure difference between left and right routes are equal.

Another benefit of the present invention is that in the case of a fault, or failure, that could create an incorrect pressure delivery in the caliper circuit, the first solenoid valve 120 isolates valves 122, 124, and ensure that there is no chance of runaway brake pressure risking wheel locking and loss of control of a vehicle.

In one aspect of the present invention, the self-sufficient electrohydraulic brake-by-wire system 12 can be used in conjunction with regenerative braking available on an autonomous or semi-autonomous vehicle to control braking of a vehicle. Such regenerative braking systems may be any suitable commercially available system.

In another aspect of the present invention, in the event of a fault or failure of one on the control systems depicted in figure 1, the self-sufficient electrohydraulic brake-by-wire system 12 can work with the other functioning unit on the other axle to slow the vehicle to safety or bring the vehicle to a controlled stop at a controlled rate using all four wheels.

With reference to Figure 5.A -5C, in the event of a fault or failure to valve 122, 124, 126 or 128 whether on the primary route 300 or secondary route 400, the crosslink valve fluidly connects both brake calipers 150 and 152 and ensures the self-sufficient electrohydraulic brake-by-wire system 12 is still effective and can still operate safely.

Figure 5.A shows the self-sufficient electrohydraulic brake-by-wire system 12 configuration in the event of a fault to valve 124 supplying the right brake caliper 152, the crosslink valve 130 is engaged to open to reroute fluid pressure via the left brake caliper 150 route. Similarly, Figure 5.B shows the self-sufficient electrohydraulic brake-by-wire system 12 configuration in the event of a failure of either direct drive valve 122 or shuttle valve 126 on the left brake caliper 150 route with the crosslink valve 130 compensating.

Figure 5.0 shows the self-sufficient electrohydraulic brake-by-wire system 12 configuration in the event of solenoid valve 120 or direct drive valves 122 and 124, and in addition, shuttle valve 126 developing a fault.

In some embodiments, in the event of a fault or failure of the self-sufficient electrohydraulic brake-by-wire system 12, optionally this information may be fed back to the autonomous vehicle driving system 14 such that the route may change to find the nearest garage or safe stopping area.

In one aspect of the present invention, the operating mode utilising valve 132 as depicted by figure 5.0 is intended to offer a final level of redundancy to stop the vehicle in the event of a catastrophic system failure with no available redundancy which can be triggered by the vehicle, the brake-by-wire system 12 itself or a corresponding brake-by-wire system 12 on the opposite axle (if present) depending on vehicle failure mode configurations.

Figure 6 is a flowchart of an exemplary process under normal operating conditions of the present invention.

At, Step 5600, the self-sufficient electrohydraulic brake-by-wire system 12 continuously monitors and determines the operating state of the self-sufficient electrohydraulic brake-by-wire system 12 using various methods, one of which may be reading the values of pressure sensors 102 through to 112 and/or reading the state of valves 120 through to 132 in the self-sufficient electrohydraulic brake-by-wire system 12.

At Step S602, the self-sufficient electrohydraulic brake-by-wire system 12 confirms no faults are present in the self-sufficient electrohydraulic brake-by-wire system 12.

At Step 5604, the self-sufficient electrohydraulic brake-by-wire system 12 selects to couple to the primary route 300 given no faults were detected by the self-sufficient electrohydraulic brake-by-wire system 12 and thus the self-sufficient electrohydraulic brake-by-wire system 12 should function in the normal mode of operation.

At Step 5606, the self-sufficient electrohydraulic brake-by-wire system 12 engages the primary route 300 by engaging the first solenoid valve 120 and ensuring the second valve remains disengaged. It is appreciated that determining the operating state of the vehicle braking system is not limited to the examples given and may include other methods of determining operating state, such as but not limited to, determining the power mode of the vehicle. When the self-sufficient electrohydraulic brake-by-wire system 12 has determined that the operating state of the self-sufficient electrohydraulic brake-by-wire system 12 is normal and no faults are detected, when the self-sufficient electrohydraulic brake-by-wire system 12 is requested to brake a vehicle, the self-sufficient electrohydraulic brake-by-wire system 12 will autonomously select to couple to the primary route 300 by engaging the first solenoid valve, 120, and further engaging direct drive valves, 122 and 124, respectively for left and right side brake calipers.

The described process is performed by a processor associated with the self-sufficient electrohydraulic brake-by-wire system 12. The processor may be part of one or more PCB controllers, or a separate processing device.

Figure 7 is a flowchart of an exemplary process under fault operating conditions of the present invention.

At, Step 5700, the self-sufficient electrohydraulic brake-by-wire system 12 continuously monitors and determines the operating state of the self-sufficient electrohydraulic brake-bywire system 12 as disclosed in Figure 6.

At Step 5702, the self-sufficient electrohydraulic brake-by-wire system 12 detects that there is a fault present either in first solenoid valve 120 or both valves 122 and 124.

At Step 5704, as the self-sufficient electrohydraulic brake-by-wire system 12 has detected the fault the self-sufficient electrohydraulic brake-by-wire system 12 autonomously selects to couple to the secondary route 400.

Therefore at step S706 the self-sufficient electrohydraulic brake-by-wire system 12 engages the second solenoid valve 132, and leaving the first solenoid valve 120 disengaged, and further engaging direct drive valves, 122 and 124, respectively for left and right side brake calipers 150 and 152. As described above, such a selection means the pressure in the self-sufficient electrohydraulic brake-by-wire system 12 is routed through the fully decoupled secondary route 400 allowing the vehicle to remain functioning. The benefit of this is that it provides an independent failsafe system. Therefore in contrast to existing autonomous systems where failure would require someone in the driver seat to compress the foot pedal, in the case of autonomous vehicles, as a foot pedal is not necessarily present, the present invention therefore provides a completely independent and safe backup in case of a power failure therefore allowing the car to stopped in a controlled and safe manner. Depending on how the car is driven, optionally, if danger is detected, the amount of pressure supplied to the brake calipers can be varied in accordance with the situation to alter the manner of the braking.

Figure 8 is a flowchart depicting an exemplary process under fault operating conditions of either direct drive valves 122 or 124 of the present invention.

At, Step 5800, the self-sufficient electrohydraulic brake-by-wire system 12 continuously monitors and determines the operating state of the self-sufficient electrohydraulic brake-by-wire system 12.

At Step 5802, the self-sufficient electrohydraulic brake-by-wire system 12 determines that the operating state of the self-sufficient electrohydraulic brake-by-wire system 12 is normal and no faults are detected. Thus the system behaves as described above for normal operation.

At Step 5804, when the self-sufficient electrohydraulic brake-by-wire system 12 is requested to brake a vehicle, the self-sufficient electrohydraulic brake-by-wire system 12 selects to couple to the primary route 300 by engaging the first solenoid valve 120 whilst the second solenoid valve 132 remains disengaged and further engaging direct drive valves 122 and 124 respectively for left and right side brake calipers. At Step S806, the self-sufficient electrohydraulic brake-by-wire system 12 detects there is an error with either first solenoid valve 120 or both valves 122 and 124 upon attempting to engage the valves. At Step S808, the self-sufficient electrohydraulic brake-by-wire system 12 determines there is a fault with the primary route 300 and switches to operate under fault conditions. At Step 5810, the self-sufficient electrohydraulic brake-by-wire system 12 switches to the secondary route, 400, by engaging the second solenoid valve 132 whilst the first solenoid valve 120 remains disengaged.

The benefit of this is that it provides numerous redundancies via different configurations and thus provides a safer braking system.

Figure 9 depicts an exemplary process under fault operating conditions or failure of both direct drive valves, 122, 124, of the present invention. At Step 5900, the self-sufficient electrohydraulic brake-by-wire system 12 continuously monitors and determines the operating state of the self-sufficient electrohydraulic brake-by-wire system 12. Step 5902 depicts the self-sufficient electrohydraulic brake-by-wire system 12 has determined that the operating state of self-sufficient electrohydraulic brake-by-wire system 12 is normal and no faults are detected. At step 5904, the self-sufficient electrohydraulic brake-by-wire system 12 is requested to brake a vehicle and autonomously selects to couple to the primary route 300 by engaging the first solenoid valve, 120, and leaving the second solenoid valve 132 disengaged and further engaging direct drive valves, 122 and 124, respectively for left and right side brake calipers 150 and 152. At Step 5906, the self-sufficient electrohydraulic brakeby-wire system 12 detects an error in either one of valves 122 or 124. Upon detection of a fault in either direct drive valves, 122 or 124, the self-sufficient electrohydraulic brake-bywire system 12 determines there is a fault in the brake-by-wire system 12 at step 5908. At Step 5910, the vehicle braking system selects to engage the crosslink valve as depicted in Figures 5.A and 5.5.

Figure 10 depicts an exemplary process under fault operating conditions on both primary route 300 and secondary route 400. In particular, Figure 10 depicts the vehicle braking system configuration upon detecting a fault in first solenoid valve 120 or direct drive valves 122 or 124 and further in shuttle valve 126 of the present invention. At, Step 51000, the self- sufficient electrohydraulic brake-by-wire system 12 continuously monitors and determines the operating state of the self-sufficient electrohydraulic brake-by-wire system 12. At Step 51002, the self-sufficient electrohydraulic brake-by-wire system 12 determines that there is a fault present on first solenoid valve 120 or both 122 and 124. At Step 51004, the self-sufficient electrohydraulic brake-by-wire system 12 is requested to brake a vehicle and autonomously selects to couple to the secondary route 400 by engaging the second solenoid valve 132 whilst the first solenoid valve 120 remains disengaged, and further engaging shuttle valves 126 and 128 respectively for left and right side brake calipers. At Step 51006, the self-sufficient electrohydraulic brake-by-wire system 12 detects there is an error with either shuttle valve 126 or 128 upon attempting to engage the valves. At Step 51008, the self-sufficient electrohydraulic brake-by-wire system 12 determines there is a fault and switches to operate under fault conditions by engaging the crosslink valve 130 to open.

Figure 11 depicts a vehicle, 10, in accordance with the invention, which includes a self-sufficient electrohydraulic brake-by-wire system 12 coupled to the brakes 16, 18, of a vehicle and furthermore communicatively coupled to an autonomous or semi-autonomous vehicle driving system 14 wherein the self-sufficient electrohydraulic brake-by-wire system 12 can receive commands from the autonomous vehicle driving system 14 to engage or disengage the brakes 16, 18. The vehicle 10 may be any suitable autonomous, semi-autonomous or partially augmented driver controlled vehicle.

It is shown from the various configurations that the vehicle braking system has numerous redundancies in place to ensure the vehicle braking system is still effective and safe if a fault or failure occurs. Thus the vehicle braking system is safer and more efficient.

Claims

Claims 1. A system for controlling a self -sufficient brake-by-wire system 12 for use in an autonomous or semi-autonomous vehicles or fully decoupled braking applications comprising: sensors 102, 104, 106, 108, 110, 112, 114 configured to determine the operating state of a brake-by-wire system 12; brake calipers 150,152 configured to apply a braking force on a wheel hub to slow the rotation of the wheel hub; a reservoir 138 configured to supply a volume of fluid to actuate the brake calipers 150, 152, the volume of fluid used to engage and disengage the brake caliper 150, 152; a pump 144 configured to supply a volume of fluid to an accumulator 136 and the brake calipers 150, 152 via the flow of a volume of fluid from the reservoir 138; the accumulator 136 configured to store pressure used to flow a volume of fluid in the brake-by-wire system 12, wherein the accumulator acts as a supplement pressure source in addition to pressure provided by the pump 144 via the flow of fluid or as a backup; a controller 101 configured to autonomously and selectively couple or decouple the flow of fluid from the reservoir 138 via the pump 144 and/or accumulator 136 to the brake calipers 150, 152, via a primary route 300 or a secondary route 400, wherein primary route 300 and secondary route 400 are independent of each other; wherein in a first configuration the controller 101 is configured to allow the flow of fluid via a primary route 300 by engaging a first solenoid valve 120 whilst a second solenoid valve 132 remains disengaged to enable active control of the brake system 12; and wherein in a second configuration the controller 101 is configured to allow the flow of fluid via the secondary route 400 by keeping the first solenoid valve 120 disengaged and engaging the second solenoid valve 132 to enable the vehicle to stop/slow down; wherein the controller is configured to switch from the first configuration to the second configuration upon detection of a fault or failure of one or more of the sections of the brake-by-wire system 12.
2. The system of claim 1, wherein the system consists of a crosslink valve 130 which selectively provides a differential flow of a volume of fluid to each brake caliper 150,152.
3. The system of claim 1, wherein a crosslink valve 130 can provide a means for applying the same a volume of fluid applied either brake caliper 150,152, in the event of a fault or failure that results in a disruption of the individual routes to the brake calipers 150,152.
4. The system of claim 1, wherein the controller 101 is further configured to selectively engage at least an individual axle.
5. The system of claim 1, wherein the system can be sub divided into a separate system for a front and rear axle, wherein the front and rear axle system controllers are communicatively linked to apply a volume of fluid equal or differential across the axles.
6. The system of claim 1, wherein the self-sufficient brake-by-wire system 12 is communicatively linked to receive instructions from a vehicle driving system 14, to control the brake calipers 150,152, wherein the vehicle driving system can be autonomous or semi -autonomous or a controller for a fully decoupled driver interface with no mechanical or hydraulic link between the driver input and the braking system.
7. The system of claim 1, wherein if the a volume of fluid exceeds a predefined limit whilst in a secondary configuration using the secondary route 400, the excess a volume of fluid from the pump 144 or accumulator 136 is relieved by a pressure relief valve 134.
8. The system of claim 1, wherein the system contains at least one internal or external, or combination of, backup energy storage device capable of powering the system in the event of power loss.
9. The system of claim 9, wherein the internal backup energy storage device is a battery, super capacitor, fuel cell or suitable energy storage device.
10. The system of claim 1, wherein the valves can be substituted for any equivalent valve capable of achieving the same operation.
11. A method for controlling a self-sufficient electrohydraulic brake-by-wire system 12 for use in an autonomous or semi-autonomous vehicles or fully decoupled braking applications comprising: activating a pump 144 configured to supply a volume of fluid to an accumulator 136 and brake calipers 150, 152 via the flow of a volume of fluid from the reservoir 138; storing a volume of fluid in a reservoir 138 configured to supply a volume of fluid to actuate the brake calipers 150, 152, the volume of fluid used to engage and disengage the brake caliper 150, 152; receiving information from sensors 102, 104, 106, 108, 110, 112, 114 configured to determine the operating state of a brake-by-wire system 12; determining the operating state of the brake-by-wire system 12; selecting to couple the flow of a volume of fluid from the reservoir 138 to the brake calipers 150,152 via the pump 144 and/or the pressurised accumulator 136 to the brake calipers 150,152; wherein in a first configuration, the flow of a volume of fluid is via a primary route 300 wherein the controller 101 engages a first solenoid valve 120 whilst a second solenoid valve 132 remains disengaged; wherein in a second configuration, the flow of pressure is via a secondary route 400 wherein the controller 101 engages the second solenoid valve 132 whilst the first solenoid valve 120 remains disengaged; determining the switch from the first configuration to the second configuration upon detection of a fault of one or more of the sections of the brake-by-wire system 12.
12. The method of claim 12, wherein if the a volume of fluid exceeds a predefined limit whilst in a secondary configuration and using a secondary route 400: determining a volume of fluid limit is exceeded, activating a pressure relief valve 134 to return the excess a volume of fluid back to the reservoir 138.
13. The method of claim 12 or 13, further comprising in the event of a power loss: switching to an internal power source, activating an internal power source to power the system.
14. The method of any of claims 12 to 14, wherein if the a volume of fluid exceeds a predefined limit whilst in a secondary configuration using the secondary route 400, the excess a volume of fluid from the pump 144 or accumulator 136 is relieved by a pressure relief valve 134.
15. The method of any of claims 12 to 15, further consisting of providing a differential flow of stored a volume of fluid to each brake caliper 150,152.
16. The method of any of claims 12 to 16, further consisting of applying the same a volume of fluid across both brake calipers 150,152, in the event of a fault or failure that results in a disruption of the individual routes to the brake calipers 150,152.
17. The method of any of claims 12 to 17, further consisting selectively engage at least one axle or all axles on a vehicle.
18. The method of any of claims 12 to 18, further consisting: receiving instructions from an autonomous vehicle driving system 14, to control the brake calipers 150,152.communicating the status of a self-sufficient brake-by-wire system 12.
19. The method of claim 11, further consisting storing pressure by the accumulator 136 to be used to flow a volume of fluid in the brake-by-wire system 12, wherein the accumulator is configured to act as a supplement pressure source.