Redundant electropneumatic brake control system and method for redundant brake control of a vehicle

Abstract

A redundant pneumatic brake control system for a vehicle (1) comprising a service brake (12) and a spring brake (11), the redundant pneumatic brake control system comprising an electro-pneumatic parking brake module (EPB) (13), a first pneumatic connection (15), a second pneumatic connection (16), a pressure control valve (PCV) (14), and a control device (10). The second pneumatic connection is arranged to connect the EPB to a control port (122) of a pneumatic control module (PCM) (121) such that the generated EPB pressure regulates the control pressure present at the control port. The control device is configured to perform independent control of the pressure-actuated spring brake and service brake by alternately controlling the PCV to an open position and a closed position based on a difference in step response of the first and second pneumatic connections while controlling the EPB pressure level.

Description

Technical Field

[0001] The present invention relates to a vehicle, and in particular to a redundant electropneumatic brake control system for a vehicle and a method for redundant brake control of a vehicle. The present invention also relates to a vehicle including a redundant electropneumatic brake control system, a computer program, and a computer-readable medium for implementing the method. Background Art

[0002] A redundant braking system is a system that provides braking capability in the event of a failure of the primary (or main) braking system. Typical redundant braking systems utilize service brakes in the front axle group and in the rear axle group, and if applicable, in one or more hitched trailers.

[0003] Currently, the commonly used backup system relies on the driver to manually depress the brake pedal to open a valve, thereby providing pressure to actuate the brakes. However, when the driver is not present, such as in an autonomous vehicle, or in the event of a malfunction and unable to depress the brake pedal, a redundant braking system is needed that can brake the vehicle based on control input from the electronic system.

[0004] Redundant braking systems for autonomous vehicles proposed to date are either complex and expensive, or simplistic and offer little in the way of ensuring vehicle stability or providing adequate braking force. In many cases, the redundant system is essentially another electronic braking system added to the primary braking system. Therefore, there is a need for improved braking systems that can provide reliable braking with reasonable effort. Summary of the Invention

[0005] The present disclosure aims to alleviate at least some of the shortcomings of the prior art. Thus, it is an object to provide a cost-effective and relatively simple redundant brake control system that utilizes many existing components available in a vehicle. Furthermore, it is an object to provide a redundant brake control system that avoids vehicle instability when braking with it.

[0006] According to a first aspect, the present disclosure relates to a redundant pneumatic brake control system for a vehicle, the vehicle comprising a service brake actuable by a pneumatic control module (PCM) and one or more pressure-actuated spring brakes. The service brakes are configured to be electrically actuated by a primary brake system during normal operation of the vehicle. The redundant pneumatic brake control system is configured to be activated if the primary brake system of the vehicle fails. The redundant pneumatic brake control system includes an electric pneumatic parking brake module (EPB), a first pneumatic connection, a second pneumatic connection, a pressure control valve, and a control device. The step response of the second pneumatic connection is shorter than that of the first pneumatic connection. The EPB is configured to generate a controllable EPB pressure. The first pneumatic connection is configured to connect the EPB to the spring brakes so that the spring brakes can be actuated by the EPB pressure. The second pneumatic connection is configured to connect the EPB to a control port of the PCM so that the generated EPB pressure regulates the control pressure present at the control port. Furthermore, the pressure control valve (PCV) is disposed in the second pneumatic connection. The PCV is controllable between an open position and a closed position. When the PCV is in the closed position, the control pressure at the control port of the PCM is maintained. Finally, the control device is configured to independently control the pressure-actuated spring brakes and service brakes by alternately controlling the PCV between the open and closed positions based on the difference in step response of the first and second pneumatic connections while controlling the EPB pressure level. Using the EPB for redundant braking is a cost-effective solution because it allows the parking brake function, which is an independent function of the primary service brake system, to be reused. By using the EPB for redundant braking, the vehicle can be electrically braked with sufficient braking force in the event of a failure without the driver having to depress the brake pedal. By using the EPB as a single regulator for both brake types to at least approximately independently (i.e., partially independently) control the spring brakes and service brakes, instability and locking of the rear brake axle can be avoided because braking force can be applied independently to different axles of the vehicle.

[0007] In some embodiments, the control means is configured to control the EPB pressure level based on the service brake pressure demand during a time period shorter than the maximum pulse length.Thereby, the spring brakes are not significantly affected when the service brakes are controlled.

[0008] In some embodiments, the maximum pulse length is shorter than the step response of the first pneumatic connection. This means that the time periods during which the EPB pressure is controlled based on the service brake pressure demand are so short that the spring brake pressure does not have time to stabilize at the new EPB pressure level. This is because the air volume in the spring brake prevents the pressure from changing too quickly. Consequently, during these time periods, the spring brake pressure is likely unable to reach a level corresponding to the service brake pressure demand.

[0009] In some embodiments, the control device is configured to control the PCV to the open position while simultaneously controlling the EPB pressure level based on the service brake demand, thereby controlling the service brakes based on the service brake demand. Furthermore, the control device is configured to control the PCV to the closed position while simultaneously controlling the EPB pressure level based on the spring brake demand, thereby controlling the spring brakes based on the spring brake demand, and maintaining the control pressure at the control port of the PCM. In some embodiments, the spring brakes are applied to the rear wheels, and the service brakes are applied to the front wheels of the vehicle. Thus, by limiting the braking force on the spring brakes without affecting the braking force on the service brakes, vehicle instability can be avoided when braking with a redundant braking system.

[0010] In some embodiments, the second pneumatic connection is arranged to connect the generated EPB pressure to the trailer input port of the trailer so that the brakes of the trailer can be controlled by the EPB pressure. Thus, the brakes of the trailer can also be controlled using the EPB as a regulator.

[0011] In some embodiments, the service brakes are actuated by a pressure increase in the control pressure at the control port of the PCM, and the spring brakes are actuated by a pressure decrease. In these embodiments, the redundant pneumatic brake control system includes a pressure reversal device disposed in the second pneumatic connection to reverse the EPB pressure and provide the reversed EPB pressure at the control port of the PCM. In some embodiments, the redundant pneumatic brake control system includes a trailer control module (TCM) disposed in the second pneumatic connection to control the input pressure at the trailer input port, and wherein the pressure reversal device is disposed in the TCM. These embodiments provide a cost-effective and relatively simple redundant brake system that utilizes many existing components of the primary brake system.

[0012] According to a second aspect, the present disclosure relates to a vehicle comprising service brakes actuatable by a pneumatic control module (PCM), pressure-actuated spring brakes, and a redundant pneumatic brake control system according to the first aspect, wherein the service brakes are configured to be electrically actuated by a primary brake system during normal operation of the vehicle.

[0013] According to a third aspect, the present disclosure relates to a method for redundant brake control of a vehicle. The vehicle includes spring brakes actuable by an electropneumatic parking brake (EPB), pressure generated by the EPB, and service brakes actuable by the EPB pressure. The pneumatic connection between the EPB and the spring brakes has a longer step response than the pneumatic connection connecting the EPB and the service brakes. The method includes: obtaining a spring brake demand and a service brake demand; and independently controlling the spring brakes and the service brakes using the EPB based on the difference in the step response of the pneumatic connection. The independent control is performed by alternately controlling a pressure control valve (PCV) disposed between the EPB and one or more service brakes to an open position while controlling the EPB pressure level based on the service brake demand, such that the EPB pressure controls the spring brakes. The method also includes controlling the PCV to a closed position while controlling the EPB pressure level based on the spring brake demand, such that the EPB pressure actuates the spring brakes and a control pressure for the service brakes is maintained.

[0014] In some embodiments, the method includes receiving an activation request message indicating a spring brake demand and a service brake demand.

[0015] In some embodiments, the EPB pressure level is controlled based on the service brake pressure demand during a time period shorter than the maximum pulse length.

[0016] In some embodiments, the maximum pulse length is shorter than a step response of the first pneumatic connection.

[0017] According to a fourth aspect, the present disclosure relates to a computer program comprising instructions which, when said program is executed by a computer, cause said computer to perform the method according to the third aspect.

[0018] According to a fifth aspect, the present disclosure relates to a computer-readable medium comprising instructions which, when executed by a computer, cause the computer to perform the method according to the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A vehicle is shown in which the proposed technology may be implemented.

[0020] Figure 2 A manually driven vehicle is shown.

[0021] Figure 3A A vehicle including a redundant electro-pneumatic brake control system is shown.

[0022] Figure 3BThe control device according to the first aspect is shown in more detail.

[0023] Figure 4 Another exemplary implementation of the proposed technology is shown.

[0024] Figure 5 is a flow chart of a method for redundant brake control.

[0025] Figure 6 is a graph showing how pressure in a redundant electro-pneumatic brake control system varies based on input. DETAILED DESCRIPTION

[0026] Ideally, a redundant braking system would allow for separate adjustment of the braking force between the front axle group (and / or trailer) and the rear axle group, and it would also prevent vehicle instability and locking of the rear axle wheels by limiting the braking force on the rear axle. The present disclosure proposes a redundant electro-pneumatic brake control system for providing braking capability in the event of failure of the main brake control system, which enables the service brakes and spring brakes to be independently controlled with one regulator. The proposed redundant electro-pneumatic brake control system uses an electro-pneumatic parking brake (EPB) as a regulator for the redundant brake control. The EPB is a component that most vehicles currently have. The main task of the EPB is to regulate the spring brakes (usually at the rear axle of the vehicle) by generating pressure at the spring brakes during driving, thereby preventing the spring brakes from being actuated. When the vehicle is parked, the pressure can be released, causing the spring brakes to lock the rear axle.

[0027] The proposed technique is based on the fact that, due to the considerable air volume in the spring brake chamber, the step response of the pneumatic connection from the pressure demand at the EPB to the actuation of the spring brake is typically significantly longer than the step response of the pneumatic connection to the service brake. This led to the realization that the service brakes (e.g., at the front axle) can be independently controlled using the EPB as a regulator, as long as the step response between the EPB and the service brakes is significantly shorter than the step response between the EPB and the spring brakes. This can often be the case because the service brakes can be controlled by the control pressure present in a capillary tube, as will be explained further below.

[0028] Therefore, this paper proposes to use the EPB as a regulator for both the spring brakes and the service brakes during redundant braking. More specifically, a pressure control valve (PCV) is added to enable control of the service brakes during short pulses and to maintain a control pressure (in a thin tube downstream of the PCV) the rest of the time. The control pressure affecting the service brakes can then be adjusted by opening the PCV during short pulses of service brake pressure required by the EPB. Between these short pulses, the EPB pressure can be used to control the spring brake pressure. Thus, the pulses must be long enough to control the service brakes, but short enough not to seriously affect the spring brakes. In this way, for example, the rear axle braking force generated by the spring brakes can be limited when necessary to avoid instability without affecting the front axle braking force generated by the service brakes.

[0029] The proposed technology can be implemented by reusing several components commonly used by a vehicle's primary service brake system. For example, in some embodiments, a trailer control module (TCM) and a pressure control regulator (PCM) are used to control the service brakes.

[0030] The TCM takes EPB pressure as input and provides a control pressure suitable for actuating the trailer's service brakes. The control pressure provided by the TCM output is typically inverted relative to the EPB pressure and readjusted to suit the trailer's service brakes. Therefore, this control pressure is also suitable for activating the other service brakes. By adding a connection from the TCM to the front axle group's PCM, the control pressure normally used to brake the trailer can also be used to apply the front axle service brakes.

[0031] Figure 1 The vehicle 1 , here a truck, in which the proposed technology can be implemented is shown. The vehicle 1 may include a transportation vehicle in a broad sense, such as a bus, a truck or other similar manned or unmanned vehicle.

[0032] The proposed technology relates to a redundant electro-pneumatic brake control system that can be electrically activated. The proposed electro-pneumatic brake control system can be implemented by reusing components used by the primary brake control system and components used by the pneumatic brake system that can be actuated by the driver by depressing the brake pedal. Therefore, in order to better understand the proposed technology, reference will first be made to Figure 2 Describes a human-piloted vehicle. Figure 2 is a conceptual diagram of the vehicle 1 (seen from above). More specifically, Figure 2 Parts of the vehicle 1 are shown which are also used by the proposed redundant electro-pneumatic braking system.

[0033] The vehicle 1 comprises a first pair of wheels (i.e. front wheels 23a, 23b) arranged on a front axle 23 and a second pair of wheels (i.e. rear wheels 24a, 24b) arranged on a rear axle 24. The vehicle 1 also comprises a spring brake 11, a service brake 12 and an air supply system 21.

[0034] The air supply system 21 is arranged to supply pressurized air for use by the vehicle's brake control system. The compressed air is produced by a compressor which is typically driven by an engine (not shown) of the vehicle 1 .

[0035] One or more spring brakes 11, often simply referred to as "parking brakes" or "emergency brakes," are pressure-activated. In other words, the spring brakes 11 are actuated by changes in pressure, typically the pressure in a pressure chamber. More specifically, the spring brakes 11 include elastic means controlled by the pressure level in the pressure chamber. When the air pressure in the brake chamber drops (the air is evacuated), the spring brakes 11 are actuated, and when the air pressure in the chamber increases, the spring brakes are released. Therefore, during driving, a certain pressure must be present in the pressure chamber to prevent the spring brakes from braking the rear wheels 24a, 24b.

[0036] Traditionally, the parking brake has been actuated by the driver manually releasing the pressure by pulling the parking lever. In modern vehicles, electropneumatic parking brakes EPB have been introduced. The EPB 13 is a component configured to generate a controllable EPB pressure. More specifically, the EPB 13 is configured to receive an electrical signal (referred to herein as a pressure demand) and generate the EPB pressure based on the pressure demand. In other words, the EPB pressure level can be controlled by a control signal provided by the control device 10. For example, the EPB pressure is controlled step by step by providing different control data (referred to herein as pressure demands) to the EPB. Thus, in Figure 2 In the vehicle 1 , the EPB pressure is used to control the pressure level in the brake chamber of the spring brake 11 so that the spring brake 11 can be actuated and released.

[0037] The EPB 13 generates EPB pressure using air supplied by the air supply system 21. The EPB pressure is supplied to a first EPB port 131 and a second EPB port 132. In these exemplary embodiments, the pressure supplied at the first EPB port 131 is controlled to the same level as the pressure at the second EPB port 132. However, the pressures at the first and second EPB ports may differ. While the pressure is substantially the same throughout the volume regulated by the corresponding EPB port 131 or 132, this does not mean that the pressure in the volume downstream of the first EPB port 131 is the same as the pressure in the volume downstream of the second EPB port 132. In other words, the volumes downstream of the ports are fully independent or disconnected from each other, even though they are regulated to the same pressure (i.e., the EPB pressure). Therefore, during transient conditions (e.g., a change in pressure demand), any flow rate required to equalize the pressures between the volumes is typically significantly less than the inflow / outflow of the EPB ports. Consequently, due to the restricted airflow through the EPB ports, step response times may differ between the EPB ports, as the larger volume downstream of the EPB port takes longer to fill / empty to reach the desired pressure.

[0038] It should be appreciated that other EPB implementations are possible. For example, the EPB may be able to adjust the pressure on the EPB ports to different levels, but still not be completely independent. For example, there may be a dependency between the pressure levels at the EPB ports, such as a pressure offset.

[0039] A pneumatic connection (referred to herein as the first pneumatic connection 15) is arranged to connect the EPB to the spring brake 11. The pneumatic connection is a pneumatic circuit that is configured to achieve pneumatic control by transmitting pressure changes to pneumatic control components. The pneumatic connection may include one or more pneumatic connections (e.g., pipes, tubes, or fittings) connected by pneumatic fittings. The pneumatic connection may additionally include additional pneumatic components, such as valves. In the example shown, the first pneumatic connection 15 transmits the EPB pressure supplied at the first EPB port 131 to the pressure chamber of the spring brake 12, so that the spring brake 11 can be actuated by the EPB pressure. Spring brakes are typically actuated at atmospheric pressure. Therefore, when driving the vehicle 1, the EPB pressure is controlled to a level above atmospheric pressure to prevent the spring brake from braking the vehicle. The second EPB port is used to brake the trailer, which will be explained further below.

[0040] To actuate or release the spring brake 11, the pressure in the pressure chamber needs to change. The volume of the pressure chamber is significantly larger than the volume of the pneumatic connection used to actuate the service brake, for example. This means that when the EPB pressure is changed based on the pressure demand provided to the EPB 13, the pressure at the EPB port 131 and in the pressure chamber takes some time to reach the required level. Consequently, some time is required before the spring brake reacts. This reaction time can be expressed as the step response of the first pneumatic connection 15. For example, the step response is defined as the time required to reach, for example, 95% of the required pressure at the EPB port 131 or 132.

[0041] The service brakes 12 can be of any conceivable type controlled by supplying compressed air. The service brakes 12 are, for example, disc brakes or drum brakes. In contrast to the spring brakes 11, the service brakes 12 are typically applied when the pressure in the pressure chamber increases. One or more pressure control modules (PCMs) 121 are arranged to supply controlled pressure to the service brakes 23. For example, one PCM 121 is arranged at the front axle 23 and one (not shown) is arranged at the rear axle 24. In other words, the service brakes 12 can be actuated by a pneumatic control module (PCM) 121. This pressure is generated using the air supply system 21. The PCM can be electrically or pneumatically controlled. The PCM is essentially a relay valve that opens airflow from the air supply system 21 based on (e.g., proportionally to) the control pressure at the PCM port 122. It should be noted that in this simplified example, the service brakes 12 are shown at the front axle. However, the vehicle 1 typically includes service brakes arranged on both the front axle 23 and the rear axle 24. Additionally, other types of brakes are often available and used for braking during operation of the vehicle, often referred to as auxiliary brakes. Examples of auxiliary brakes are the engine brake and the exhaust brake.

[0042] During normal operation, the braking of the vehicle 1 is controlled by the main (or primary) brake system. In modern vehicles, the main brake system is typically implemented using brake-by-wire, i.e., brake control is performed by electrical means. Braking of the vehicle 1 is then achieved, for example, by sending an electrical signal to the PCM 121, instructing the PCM 121 to apply pressure to the service brakes 12 using compressed air supplied by the air supply system 21. The main brake control system may also control the EPB to actuate the spring brakes 11.

[0043] The vehicle 1 also includes a pneumatic brake control system actuated by the service brake module (FBM) 20. If the primary brake control system fails (for any reason), the pneumatic brake control system is activated. The pneumatic brake control system uses the control pressure generated by the service brake module (FBM) 20 to actuate the service brakes 12. If the primary brake control system is operating normally, it closes a valve in the PCM to block the control pressure generated by the FBM 20, preventing the FBM 20 from applying control pressure to the service brakes. In other words, the PCM selects between "electric" and "air" pressure from the FBM. In normal operation, it selects electric pressure. However, if the primary brake control system fails, the pneumatic brake control system immediately takes over brake control without requiring any action. In other words, control of the brakes is automatically taken over. The primary brake system is typically fail-silent. Therefore, it is self-diagnostic and can automatically shut down if a fault is detected. Additionally, if the electrical system (which controls the primary brake system) becomes inoperative, the pneumatic redundant system takes over.

[0044] The pneumatic brake control system operates as follows. When the brake pedal is depressed, a valve in the FBM opens, generating control pressure using the air supply system 21. The control pressure generated by the FBM is supplied to the PCM 121 and the trailer control module (TCM) 17. The PCM 121 is then controlled to supply pressure to activate the service brakes 12, typically on the front axle 23 and rear axle 24. In this way, the braking force applied by the service brakes 23 is pneumatically controlled by the control pressure supplied by the FBM.

[0045] If a trailer is attached to the vehicle 1, the trailer service brakes can also be controlled by the main brake system or by the pneumatic brake control system. The TCM 17 is a component that takes pressure as input and, based on that pressure, generates a control pressure suitable for controlling the trailer service brakes. For example, the TCM can be controlled by the control pressure generated by the FBM or the EPB pressure generated by the EPB 13.

[0046] Thus, the second EPB port 132 is pneumatically connected to the input port of the TCM 17. Since reduced EPB pressure is required to apply the spring brakes 11, the control pressure provided by the TCM output port is generally inverted and readjusted relative to the EPB pressure to be suitable for controlling the trailer brakes. In this way, the trailer brakes can also be activated when the driver depresses the brake pedal.

[0047] The proposed technology will now be described with reference to FIG3. The vehicle 1 of FIG3 comprises Figure 23 . Furthermore, components are added that implement electric brake control based on electronic control signals in the event of a failure of the vehicle's primary brake system 1 . Thus, redundant brake control can be controlled by an electrical signal generated by the autonomous driving control function, rather than by pneumatic control pressure generated when the driver depresses the brake pedal. Electric brake control is typically controlled by a redundant power source (e.g., an independent battery). Thus, the proposed redundant electric pneumatic brake control system (referred to herein as the electric pneumatic brake control system) can be used when no driver is present. For simplicity, the pressure supply system 21 is not shown in FIG. 3 .

[0048] The proposed electropneumatic brake control system uses several components which are also Figure 2 More specifically, the electropneumatic brake control system includes an EPB 13 configured to generate a controllable EPB pressure. The system also includes a first pneumatic connection 15 arranged to connect the EPB to the spring brake 11 so that the spring brake 11 can be actuated by the EPB pressure. These components have been combined Figure 2 Described.

[0049] Furthermore, the electropneumatic brake control system includes a second pneumatic connection 16 , a pressure control valve PCV 14 and a control device 10 .

[0050] The second pneumatic connection 16 is a pneumatic connection that connects the second EPB port 132 of the EPB 13 to the control port 122 of the PCM 121. The generated EPB pressure thereby regulates the control pressure present at the control port 122. Thus, the second pneumatic connection 16 enables the use of the EPB pressure to control the service brakes 12. The second pneumatic connection 16 may include one or more pneumatic components. Thus, it may be a pneumatic circuit. In the illustrated example, the second pneumatic connection 16 is a pneumatic circuit comprising several pneumatic components. More specifically, the second pneumatic connection 16 includes the TCM 17, the PCV 14, the valve 18, and the pneumatic linkages connecting these components. However, in all cases, the step response of the second pneumatic connection 16 is shorter than that of the first pneumatic connection 15. In the illustrated example, there are two physical ports at the EPB 13. However, in some embodiments, the EPB has only one port, so the first and second pneumatic connections may have common portions. In any case, the first pneumatic connection 15 and the second pneumatic connection 16 are arranged in such a way that there is a difference in the step response from the EPB pressure demand to the control pressure between the two connections.

[0051] Therefore, the pressure control valve (PCV) 14 is arranged in the second pneumatic connection 16. The PCV 14 is a valve that can be controlled to be set to an open position and a closed position. In the open position, fluid can flow freely through the PCV 14, so that the pressure upstream of the PCV is the same as the pressure downstream of the PCV 14. When the PCV 14 is in the closed position, fluid flow through the PCV 14 is blocked. When the connection downstream of the PCV 14 is substantially closed, the control pressure at the control port 122 of the PCM 121 can be maintained, or at least only varies slightly (e.g., due to leakage). In other words, when the PCV 14 is in the closed position, the control pressure at the control port 122 of the PCM 121 is maintained. "Maintained pressure" here means that the pressure remains nearly constant. In reality, of course, there may be a small amount of leakage, but this does not affect the service brakes 12. However, if leakage reduces the pressure by a certain amount, the pressure can be replenished by opening the PCV. The PCV 14 facilitates independent control of the spring brakes 11 and the service brakes 12, as will be described further below. In the example shown, the PCV 14 is positioned downstream of the TCM 17 , but the same functionality can be achieved by placing the PCV 14 upstream of the TCM 17 .

[0052] Since the service brakes 12 are typically actuated by an increase in control pressure at the control port 122 of the PCM 121, and the spring brakes 11 are actuated by a decrease in pressure, the EPB pressure needs to be reversed to suit the control of the service brakes 12. This reversal is essentially a reversal of the pressure change, meaning that an increase in EPB pressure is converted to a decrease in pressure. In other words, in some embodiments, the redundant pneumatic brake control system includes a pressure reversal device 17 (e.g., a reversal valve) disposed in the second pneumatic connection 16 to reverse the EPB pressure and provide the reversed EPB pressure at the control port of the PCM.

[0053] In the illustrated example, the pressure reversal device is implemented by the TCM 17, which, as mentioned above, is the component normally used to control the trailer brakes. The TCM 17 reverses pressure variations in the EPB pressure, allowing the pressure generated by the TCM 17 to also be used to control the service brakes 12. By adding a connection from the TCM 17 to the front axle group PCM, the pressure normally used to brake the trailer is also used to apply the front axle service brakes 12 by opening valve 18, located between the TCM 17 and the PCM 12. Valve 18 is, for example, a 3 / 2 valve with three pipe connections and two orifices. When one orifice is open, the other is closed, and vice versa. Thus, valve 18 is controllable to connect control port 122 of the PCM 121 to the TCM output or atmospheric pressure. Valve 18 is used to activate the redundant braking of the front service brakes. When the redundant brake control system is not in use, it is closed, ensuring that the normal braking function performed by the primary brake system is not affected by the redundant brake control system. Valve 18 is required in this exemplary embodiment because otherwise the main brake system would respond to the EPB pressure at the PCM, which is undesirable. However, other solutions are possible. In summary, using this embodiment, there is no need to add an additional reversing valve, which would be required if the TCM 17 were not used.

[0054] As in the example above, the vehicle 1 can be connected to a trailer. Therefore, in some embodiments, a portion 16 a of the second pneumatic connection 16 is arranged to connect the generated EPB pressure to the trailer input port of the trailer, so that the trailer's brakes can be controlled by the EPB pressure. Thus, the EPB 13 can also be used to brake the trailer during redundant braking.

[0055] It must be appreciated that in this disclosure, embodiments using spring brakes at the rear axle and service brakes at the front axle have been used to illustrate the proposed technology. However, it must be appreciated that the technology can of course be used to control spring brakes and service brakes arranged on any axle.

[0056] Now go to Figure 3B , which shows in more detail a control device 10 configured to implement the proposed method. In some embodiments, the control device 10 is a "unit" in a functional sense. Thus, in some embodiments, the control device 10 is a control device comprising several physical control devices operating together.

[0057] The control device 10 includes one or more ECUs. An ECU is essentially a digital computer that controls one or more electrical systems (or electrical subsystems) of the vehicle 1 based on information read from, for example, sensors and instruments located in various parts and components of the vehicle 1. An ECU is a general term used in automotive electronics to refer to any embedded system that controls one or more functions of an electrical system or subsystem in a transportation-demand vehicle. The control device 10 includes, for example, a brake control module (BCM), an automated driving control unit (ADAS), or any other suitable ECU.

[0058] The control device 10 comprises hardware and software. The hardware essentially consists of various electronic components on a printed circuit board (PCB). The most important of these components are typically one or more processors 101, such as microprocessors, and memory 102, such as EPROM or flash memory chips. For simplicity, only one processor 101 and memory 102 are shown in the control device 10, but in actual implementations, more processors 101 and memory 102 may be present.

[0059] The control device 10 , or more specifically the processor 101 thereof, is configured to cause the control device 10 to perform all aspects of the method described above and below. This is typically done by running computer program code 'P' stored in the memory 102 of the processor 101 of the control device 10 .

[0060] More specifically, the control device 10 is configured to independently control the pressure-actuated spring brake 11 and service brake 12 by alternately controlling the PCV 14 to an open and closed position while controlling the EPB pressure level. Independent or separate control, as used herein, means that the service and spring brakes can be independently controlled to a certain extent. As will be appreciated from the following examples, this does not mean that the control is completely independent, as the spring brakes will be affected by the control of the service brakes. In other words, independent brake control, as used herein, means that the brake control is approximately independent, meaning that it is sufficiently independent to allow for independent control of the service and spring brakes to a certain extent. Therefore, independence does not require that the other brakes are completely unaffected when the other is controlled. In any case, the control is sufficiently independent to distribute the braking force between the axles to avoid instability. Control is based on the difference in the step response of the first and second pneumatic connections 15, 16. For example, when the control pressure for the service brakes changes, control can be performed as follows.

[0061] In the initial position, the PCV 14 is closed and the EPB is controlled based on the spring brake demand. The spring brake demand herein refers to a spring brake request, corresponding to, for example, the braking force required at the rear axle, while the service brake demand herein refers to a service brake request, corresponding to, for example, the braking force required at the front axle and / or trailer. While the PCV is closed, the pressure at control port 122 of the PCM 121 is maintained (i.e., kept constant) and is independent of the EPB pressure. The EPB control signal is then changed based on the service brake demand, and the PCV 14 is controlled to open to balance the pressure between the input and output of the PCV 14. As a result, the control pressure present at control port 122 of the PCM 121 is updated, which controls the "service brakes" through the PCM.

[0062] Once the desired pressure at the control port 122 of the PCM 121 has been reached, the PCV 14 is controlled to close and the spring brake demand is again requested from the EPB 13. The service brake demand will remain downstream of the PCV 14. Thus, the control pressure downstream of the PCV 14 has been changed based on the service brake demand, and the EPB can again be controlled based on the spring brake demand.

[0063] In some embodiments, the redundant brake control routine has two primary states. These two states can be selectively set using the control device 10. In one state, the control device 10 is configured to control the PCV to an open position while simultaneously controlling the EPB pressure level based on the service brake demand. The service brake 12 is then controlled based on the service brake demand. In the other state, the control device 10 is configured to control the PCV 14 to a closed position while simultaneously controlling the EPB pressure level based on the spring brake demand. Thus, the spring brake 11 is controlled based on the spring brake demand, and the control pressure at the control port 122 of the PCM 121 remains at the same level as before closing the PCV 14. When the PCV 14 is open, the effect of the EPB pressure at the spring brake 11 is limited by the inertia of the first pneumatic connection 15. It should be appreciated that other states may be used as appropriate for a given application.

[0064] The period during which the EPB 13 is adjusted based on the service brake demand must be short enough not to significantly affect the spring brakes 11. Typically, the EPB 13 is controlled based on the service brake demand only during short pulses. In other words, the control device 10 is configured to control the EPB pressure level based on the service brake pressure demand during periods shorter than the maximum pulse length. The rest of the time, the EPB can be controlled based on the spring brake demand.

[0065] The pulse length should be long enough to allow the pressure at the control port 122 of the PCM 121 to reach the service brake demand, but no longer than necessary because the pressure will also affect the spring brake pressure (albeit much more slowly). In other words, the pulse length should be equal to or longer than the step response of the second pneumatic connection 16. For example, if 95% of the time to reach the service brake demand is 100 ms, a suitable time might be 150 ms.

[0066] This time (i.e., pulse length) is typically required to be significantly shorter than the step response of the first pneumatic connection 15 , otherwise the spring brake may be affected by the service brake demand. In other words, in some embodiments, the maximum pulse length is shorter than the step response of the first pneumatic connection 15 . Therefore, it is desirable that the pulse length be significantly shorter than the step response of the first pneumatic connection 15 so that the spring brake is not significantly affected. For example, the pulse length may be shorter than 10% or 50% of the step response of the first pneumatic connection 15 . However, this all depends on the response time of the pneumatic connections. For example, if the step response of the first pneumatic connection 15 is 100 ms and the step response of the second pneumatic connection 16 is 1000 ms, then a suitable on-time may be 150 ms. On the other hand, if the step response of the first pneumatic connection 15 is 200 ms and the step response of the second pneumatic connection 16 is 3000 ms, then a suitable on-time may be 200-600 ms.

[0067] As mentioned above, the control device 10 is also configured to control the valve 18 to open when the redundant brake control system is active and to close when it is inactive.

[0068] Figure 4 Another exemplary embodiment of the proposed technology is shown. Figure 4 In the example of , the vehicle does not include the FBM 20 and associated pneumatic connections. This may be the case in a fully autonomous vehicle that can only be driven autonomously.

[0069] Figure 5 A flow chart showing a method for redundant brake control of a vehicle 1 is shown. The method is used to control a device, such as Figure 3A or 4 in the control device 10 of the vehicle 1. The method is used in a control device, such as the control device 10 of the vehicle 1.

[0070] The method is typically performed when the primary brake system is not operational. This may be indicated, for example, by the primary brake system itself or by another subsystem of the vehicle 1. In other words, in some embodiments, the method comprises receiving S0 an activation request message indicating that the primary brake control system is malfunctioning.

[0071] The control unit also needs to know how much braking force is required on the front axle 23 and the rear axle 24, as well as on the trailer. In some embodiments, the activation request includes information indicating a spring brake demand and a service brake demand. Alternatively, the spring brake demand and the service brake demand are determined by the control device 10 based on available data (e.g., sensor data and driving data). In other words, the method includes obtaining S1 the spring brake demand and the service brake demand.

[0072] The method also includes independently controlling the spring brakes and service brakes using the EPB (S2) based on differences in the step response of the pneumatic connections by alternately or selectively allowing the EPB pressure to control the spring brakes and service brakes. The spring brakes 11 are controlled by the EPB pressure by controlling the PCV (S2b) to the closed position while simultaneously controlling the EPB pressure level based on the spring brake demand. The service brakes 12 are controlled by the EPB pressure by controlling the PCV (S2a) positioned between the EPB and one or more service brakes to the open position while simultaneously controlling the EPB pressure level based on the service brake demand. In some embodiments, other states may be provided between these control states.

[0073] In some embodiments, the S2b EPB pressure level is controlled based on the service brake pressure demand during a period shorter than the maximum pulse length. The pulse length is set based on the step response of the first and second pneumatic connections, as described above in conjunction with Figure 3A In some embodiments, the pulse length is at least equal to the step response of the second pneumatic connection 16. In some suitable embodiments, the maximum pulse length is shorter than the step response of the first pneumatic connection 15. In some embodiments, the S2a EPB pressure is controlled based on the spring brake pressure demand at other times.

[0074] Figure 5 is a graph showing how pressure in a redundant electro-pneumatic brake control system varies based on input.

[0075] The upper graph shows the change of spring brake control over time. More specifically, the solid line shows the pressure demand on the EPB and the dashed line shows the corresponding pressure at the first EPB port 131.

[0076] The middle graph shows the corresponding service brake control over time. More specifically, the dashed line shows the pressure downstream of PCV 14 and the dotted line shows the pressure upstream of PCV.

[0077] The lower graph shows PCV control. More specifically, the solid line shows the control signal to the PCV, which can be set to two control levels representing "hold pressure" or "pass pressure."

[0078] At 41 , the EPB pressure demand is set to a low pressure level and the PCV is opened. This causes the pressure in the spring brake chamber to slowly decrease to the EPB pressure while the pressure downstream of the PCV 14 increases quickly to the inverse of the EPB pressure.

[0079] At 42 , the EPB pressure demand changes (increases) to prevent the spring brakes from locking the rear axle. Simultaneously, the PCV 14 is controlled to maintain pressure, thereby keeping the control pressures for the service brakes 12 and the trailer brakes at the same level. Consequently, the pressure at the first EPB port 13 controlling the spring brakes slowly rises to the desired level.

[0080] At 43 , a different control pressure is requested for the service brakes. Thus, the EPB demand changes in short pulses based on the service brake demand, while the PCV 14 is opened to regulate the pressure downstream of the PCV 14. Note that during the pulse, the pressure at the first EPB port decreases slightly. However, due to the slow step response of the first pneumatic connection 15 , the effect of this decrease is not noticeable.

[0081] The terminology used in the description of the embodiments as illustrated in the accompanying drawings is not intended to limit the described methods, control devices or computer programs. Various changes, substitutions and / or alterations may be made without departing from the embodiments of the invention as defined in the appended claims.

[0082] As used herein, unless expressly stated otherwise, the term "or" should be interpreted as a mathematical OR, i.e., as an inclusive disjunction, and not as a mathematical exclusive OR (XOR). In addition, the singular forms "a", "an", and "the" should be interpreted as "at least one", and thus may also include multiple entities of the same type, unless expressly stated otherwise. It should also be understood that the terms "comprises", "includes", and / or "contains" specify the presence of stated features, actions, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, actions, integers, steps, operations, elements, components, and / or groups thereof. A single unit, such as a processor, may implement the functions of several items recited in the claims.

Claims

1. A redundant pneumatic brake control system for a vehicle (1), the vehicle comprising a service brake (12) actuatable by a pneumatic control module (PCM) (121) and a pressure-actuated spring brake (11), wherein the service brake (12) is configured to be electrically actuated by a primary brake system during normal operation of the vehicle (1), and wherein the redundant pneumatic brake control system is arranged to be activated upon failure of the primary brake system of the vehicle (1), the redundant pneumatic brake control system comprising: - an electropneumatic parking brake module EPB (13), said EPB being configured to generate a controllable EPB pressure, a first pneumatic connection (15) arranged to connect the EPB to the spring brake (11) such that the spring brake (11) can be actuated by the EPB pressure, a second pneumatic connection (16) arranged to connect the EPB to a control port (122) of the PCM (121) such that the generated EPB pressure regulates the control pressure present at the control port (122), wherein the step response of the second pneumatic connection (16) is shorter than the step response of the first pneumatic connection (15), Characterized in that, the redundant pneumatic brake control system includes: a pressure control valve PCV (14) arranged in the second pneumatic connection (16), wherein the PCV (14) is controllable to an open position and a closed position, wherein when the PCV is in the closed position, the control pressure at the control port (122) of the PCM (121) is maintained, and - an electronic control unit (10) configured to perform independent control of the pressure-actuated spring brake (11) and the service brake (12) by alternately controlling the PCV (14) to the open position and the closed position based on a difference in step responses of the first and second pneumatic connections (15, 16) while controlling an EPB pressure level.

2. The redundant pneumatic brake control system according to claim 1, wherein the electronic control device (10) is configured to: - Controlling the EPB pressure level based on the service brake pressure demand during time periods shorter than the maximum pulse length.

3. A redundant pneumatic brake control system according to claim 2, wherein the pulse length is at least as long as a step response of the second pneumatic connection (16).

4. The redundant pneumatic brake control system according to claim 3, wherein the pulse length is shorter than a step response of the first pneumatic connection (15).

5. The redundant pneumatic brake control system according to any one of claims 1 to 4, wherein the electronic control device (10) is configured to: - controlling the PCV to the open position while controlling the EPB pressure level based on the service brake demand, thereby controlling the service brakes based on the service brake demand, and - controlling the PCV (14) to the closed position while controlling the EPB pressure level based on the spring brake demand, whereby the spring brake is controlled based on the spring brake demand and the control pressure at the control port (122) of the PCM (121) is maintained.

6. A redundant pneumatic brake control system according to any one of claims 1 to 4, wherein the spring brakes (11) are arranged to the rear wheels and the service brakes (12) are arranged to brake the front wheels of the vehicle (1).

7. A redundant pneumatic brake control system according to any one of claims 1 to 4, wherein the second pneumatic connection (16) is arranged to connect the generated EPB pressure to a trailer input port of a trailer such that the brakes of the trailer can be controlled by the EPB pressure.

8. The redundant pneumatic brake control system according to any one of claims 1 to 4, wherein the service brake is actuated by a pressure increase of a control pressure at a control port (122) of the PCM (121), wherein the spring brake is actuated by a pressure decrease, and wherein the redundant pneumatic brake control system comprises: - a pressure reversal device (17) arranged in the second pneumatic connection to reverse the EPB pressure and provide the reversed EPB pressure at a control port of the PCM.

9. The redundant pneumatic brake control system according to claim 8, wherein the redundant pneumatic brake control system includes a trailer control module (TCM) arranged in the second pneumatic connection to control the input pressure at the trailer input port, and wherein the pressure reversal device is arranged in the TCM.

10. A carrier (1), comprising: - a service brake (12) actuatable by a pneumatic control module PCM (121), - a pressure-actuated spring brake (11), wherein the service brake (12) is configured to be electrically actuated by a main brake system during normal operation of the vehicle (1), and - A redundant pneumatic brake control system according to any one of claims 1-9.

11. A method for operating a redundant pneumatic brake control system for a vehicle (1), wherein the vehicle (1) comprises a spring brake (11) actuatable by an electropneumatic parking brake (EPB), pressure generated by the EPB, and a service brake actuatable by the EPB pressure, and wherein a pneumatic connection between the EPB and the spring brake has a longer step response than a pneumatic connection connecting the EPB and the service brake, the method comprising: - obtain the spring brake demand and service brake demand, and - Independent control of the spring brake and the service brake is performed using the EPB and based on the difference in step response of the pneumatic connection by alternately performing the following operations: controlling a pressure control valve (PCV) disposed between the EPB and one or more service brakes to an open position while controlling the EPB pressure level based on the service brake demand such that the EPB pressure controls the spring brakes, and Controlling the PCV to a closed position while controlling the EPB pressure level based on spring brake demand so that EPB pressure actuates the spring brakes and control pressure controlling the service brakes is maintained.

12. The method according to claim 11, comprising: - Receiving an activation request message indicating a spring brake demand and a service brake demand.

13. A method according to claim 11 or 12, controlling the EPB pressure level based on the service brake pressure demand during a time period shorter than the maximum pulse length.

14. The method of claim 13, wherein the redundant pneumatic brake control system comprises a first pneumatic connection (15) arranged to connect the EPB to the spring brake (11) such that the spring brake (11) can be actuated by the EPB pressure; and The maximum pulse length is shorter than a step response of the first pneumatic connection (15).

15. A computer program comprising instructions which, when executed by a computer, cause the computer to perform the method according to any one of the preceding claims 11 to 14.

16. A computer-readable medium comprising instructions which, when executed by a computer, cause the computer to perform the method according to any one of the preceding claims 11 to 14.

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