Description:Complete Specification:
The following specification describes and ascertains the nature of this invention and the manner in which it is to be performed

Field of the invention
[0001] The present invention relates to a brake by wire systems and more specifically to enable to a brake by wire functionality during a latent fault in the brake by wire system.
[0002] Background of the invention

[0003] A brake-by-wire system includes a brake assembly, a pedal assembly, a pedal feel simulator unit and an actuator assembly or a pressure unit. The actuator assembly/pressure unit consists of a plunger piston system which is connected to a high dynamic motor using a planetary gear. A controller receives braking signals from the pedal assembly and outputs a command signal to the actuator. The actuator drives the motor and plunger which push the brake fluid to the brakes.
[0004] Thus, the driver requested pressure (pressure applied on the brake pedal) is boosted (amplified) in the brake by-wire mode. The pedal is coupled to the pedal feel simulator through a valve when in By-wire mode. The pedal feel simulator provides a comfortable pedal feel to the driver. Due to reasons such as sensor failure or leakage in the brake circuits or the master cylinder, the brake-by-wire functionality of the vehicle is disabled, in such a scenario the vehicle runs in the backup mode where the driver directly pushes the fluid to the brakes. Therefore, in the backup mode, no boosting of driver pressure occurs.
[0005] In the brake by-wire-system, when driver presses the brake, the driver requested pressure is calculated using master cylinder sensor and input rod sensor. The calculated pressure is sent to pressure unit for the actuation. A controller calculates the required volume flow (motor speed) to realize the target pressure and actuates the motor accordingly. The ratio of driver applied pressure from master cylinder sensor and the system actuated pressure decides the boost ratio (in comparison with conventional vacuum booster). In case of the sensor failures (either master cylinder sensor or input rod sensor), the state of the art is to switch to mechanical backup state, where driver directly pushes the brake fluid to the brakes.
[0006] Even if one of the sensor is working, the detection of latent failures in the system is not present in the state of the art. If in such a scenario, the brake by wire functionality is continued relying on the sensors still functioning, there is a risk of actuation of too little brake pressure than the actual brake pressure requested by the driver.
[0007] The prior art US2014028084 AA discloses a motor vehicle brake system operable in a brake-by-wire and fallback modes. The system includes a brake pedal, a master cylinder, a reservoir, a travel simulator , an electrically controllable pressure source , isolation valves pumps and a low-pressure accumulator, an inlet valve and an outlet valve for each wheel brake , valves connected to the pumps, and a control and regulation unit. A valve arrangement establishes for each brake circuit a connection from the pressure chamber of the master cylinder to the modulator admission pressure line and disconnects the connection when unenergized, the valve arrangement preventing the pressure source from being subjected to pressure from the pressure chambers.
[0008] The present disclosure proposes a enable a brake by wire functionality during a latent fault in the brake by wire system and a method thereof. In the present disclosure a latent fault in the system in addition to any sensor failure (for instance an input rod failure or a failure of master cylinder pressure sensor) in the system can be detected.
[0009] The disclosure proposes to monitor the leakage in tandem master cylinder and to detect any latent defect in the pedal feel simulator unit. The pressure unit can be used as a source to build pressure in one of the chambers of Tandem Master Cylinder (TMC) by opening/closing valve in the brake circuit. The pressurization of the first chamber of TMC (TMC1) moves the floating piston in the second (TMC2). This pressure in the Tandem master cylinder is calculated in the Master cylinder pressure sensor. By holding the pressure in the tandem master cylinder, any pressure drop observed during the holding period due to a leakage in TMC may be recorded and calculated by the master cylinder pressure sensor. During this time the Pedal feel simulator (PFS) and the base brakes on the first brake circuit shall be filled to ensure no adverse base brake effects while monitoring. Further, based on the volume consumption from the pressure unit , which is calculated from Actuator pressure sensor and the Motor current sensor, one can estimate the leakage in the TMC. In order to be more robust, both the circuit separation valves may be closed for a more robust leakage estimation. Once the TMC leakage is estimated, the second circuit separation valve and the simulator separation valve shall be opened and the loss of pressure shall be observed based on the volume consumption in Pedal feel simulator.
[0010] Based on the presence of the latent fault (leakage/defect) and the sensor fault in the brake by wire system, the “by wire mode” can be enabled in one or both the brake circuits of the system. The driver’s input request can be calculated from available sensors (either master cylinder sensor or input rod sensor) depending on the fault in the sensors and the latent fault. Based on the detection of leakage in the tandem master cylinder and the detection of the defect in the pedal feel simulator unit (PFS) unit, one or both the brake circuits of the brake by wire system can function under brake by wire mode. There may also be a case where only one brake circuit is provided with the brake fluid to enable the by wire mode and the other circuit can be coupled to the driver for mechanical braking.

Brief description of the accompanying drawings
[0011] Preferred exemplary embodiments of the present invention will hereinafter be described in conjunction with the appended drawings:

[0012] Figure 1 depicts a brake by wire system with a controller to enable a brake by wire functionality during a latent fault in the brake by wire system.
[0013] Figure 2 depicts a flowchart for a method to enable a brake by wire functionality during a latent fault in the brake by wire system.

Detailed description of the drawings

[0014] The present invention will now be described by way of example, with reference to accompanying drawings. Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments are sometimes illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In predetermined instances, details which are not necessary for an understanding of the present invention, or which render other details difficult to perceive may have been omitted.

[0015] The advantages of the present invention will be apparent with this detailed description, wherein, the best method known to the applicant to implement the invention has also been described. It is however to be noted that numerous alternate embodiments of the present invention are possible and the disclosure of one of them is not to be construed as limiting the others.

[0016] The disclosure further provides examples for the working of the present disclosure and the best method known to the applicant to perform the said disclosure. The working of the present disclosure as described below is to be taken just as an example and should not impart any limitation.

[0017] The brake-by-wire system includes a brake assembly (coupled with the base brakes of front and rear wheels of the vehicle), a pedal assembly coupled with a pedal feel simulator, and a pressure unit comprising an actuator and a motor to provide a target brake pressure. The pedal is coupled to the pedal feel simulator through a simulator separation valve when the vehicle is in the brake by-wire mode to provide a comfortable pedal feel to the driver. The actuator consists of a plunger piston system which in connected to the high dynamic motor using planetary gear. A controller receives braking signals from the pedal assembly and outputs a command signal to the actuator. The actuator drives the motor and plunger which push the brake fluid to the brakes. The brake assembly is connected to the pressure unit in a brake by-wire mode. In the brake by wire mode, the driver requested pressure is boosted.

[0018] Due to reasons such as sensor failures, where an input brake pressure requested by the driver cannot be measured, the vehicle goes into a backup mode wherein, the brake is applied mechanically through hydraulic means as in conventional braking systems. The mechanical braking/backup mode includes a hydraulic connection between pedal interface to the brakes, where the driver directly pushes the fluid to the brakes, therefore no boosting of driver pressure possible in the backup mode.
[0019] The brake assembly comprises a tandem master cylinder connected with a first brake circuit and a second brake circuit and a first and second circuit separation valves (CSV 1 and CSV2, respectively). When the vehicle is in by wire mode, these CSVs isolate the pedal assembly from the base brakes (braking the wheels). In the backup mode the CSVs are opened to provide a direct communication between the pedal assembly and the brakes.
[0020] The pressure unit is connected to the first and second brake circuit through the first and second plunger separation valve (PSV1 and PSV2). The PSVs are in normal position (PSVs opened) that provides hydraulic communication between pressure unit to the brakes when in the by wire mode and the PSVs are closed when the system is in backup mode (mechanical braking) to isolate the pressure unit from brakes when during the mechanical backup mode.
[0021] In the brake by wire system, when a driver presses the brake, the driver requested pressure is calculated using a master cylinder pressure sensor and input rod sensor , the calculated target pressure is sent to pressure unit for the actuation. The controller calculates the required volume flow (and motor speed) to realize the target pressure and actuate the motor accordingly. The ratio of driver applied pressure from master cylinder pressure sensor and the system actuated pressure decides a boost ratio.
[0022] In case of the sensor failures including either master cylinder sensor or input rod sensor, as per the state of the art requirement, the driver directly pushes the brake fluid to the brakes. Therefore, no boosting of driver pressure is possible in this mode. The reasons to switch to this mechanical back up is an underlying safety concern. For instance, in an example, in case of master cylinder pressure sensor failure, the system cannot depend completely on the input rod sensor because a second failure of a simulator separation valve or a leakage in the pedal feel simulator will result in a calculation error and actuation of too less brake pressure than driver originally intended. This means, the performance in this situation is worse than the driver would have got in mechanical back up.
[0023] In another example, in case of input rod sensor failure, the system cannot depend completely on master cylinder pressure sensor because a second failure of leakage in tandem master cylinder results the pressure drop in master cylinder pressure sensor. It is not possible to distinguish this pressure drop as driver release or leakage. This means in case if the real leakage occurs, the system will reduce the brake pressure and the performance in this situation would be worse than what the driver would have got in mechanical back up.
[0024] In order to solve the problem aforementioned the present disclosure proposes to monitor the leakage in tandem master cylinder and to detect any latent defect in the pedal feel simulator unit. The pressure unit can be used as a source to build pressure in one of the chambers of Tandem Master Cylinder (TMC) by opening/closing valve in the brake circuit. The pressurization of a first chamber of TMC (TMC1) moves the floating piston in the second (TMC2). This pressure in the Tandem master cylinder is calculated in the Master cylinder pressure sensor. By holding the pressure in the tandem master cylinder, any pressure drop observed during the holding period due to a leakage in TMC may be recorded and calculated by the master cylinder pressure sensor. During this time the Pedal feel simulator (PFS) and the base brakes on the first brake circuit shall be filled to ensure no adverse base brake effects while monitoring. Further, based on the volume consumption from the pressure unit , which is calculated from Actuator pressure sensor and the Motor current sensor, one can estimate the leakage in the TMC. In order to be more robust, both the circuit separation valves may be closed for a more robust leakage estimation. Once the TMC leakage is estimated, the second circuit separation valve and the simulator separation valve shall be opened and the loss of pressure shall be observed based on the volume consumption in Pedal feel simulator.
[0025] Based on the presence of the latent fault (leakage/defect) and the sensor fault in the brake by wire system, the “by wire mode” can be enabled in one or both the brake circuits of the system. The driver’s input request can be calculated from available sensors (either master cylinder sensor or input rod sensor) depending on the fault in the sensors and the latent fault. Based on a detection of leakage in the tandem master cylinder and a detection of a defect in the pedal feel simulator unit (PFS) unit, one or both the brake circuits of the brake by wire system can function under brake by wire mode. If only one brake circuit is provided with the brake fluid in the by wire mode , the other circuit can be coupled to the driver for mechanical braking.

[0026] Referring to Figure 1, disclosed is a brake by wire system comprising a controller(1) to enable a brake by wire functionality during a latent fault in the brake by wire system, according to an embodiment of the present disclosure.
[0027] A controller (1) is present to enable a brake-by-wire functionality during a latent fault in a tandem master cylinder (7) and the PFS unit (16) of the brake-by-wire system (10) of a vehicle. The controller (1) may have an input/output interface, and associated memory to store a software logic. The controller may be a general electronic control unit (ECU) for automobiles the applications of which are widely known in the art. Said brake by wire system comprises a first brake circuit (5) with a first circuit separation valve (CSV1) (5a) and a second brake circuit (6) with a second circuit separation valve (CSV2) (6a). The brake by wire system comprises at least one sensor (2, 3, 4a, 4b, 8b, 8c) in communication with the controller (1) to measure a physical quantity, which may be not limited to a pressure, volume and current and signals to the controller (1).
[0028] From Figure 1, in an example, the at least one sensor (2) is an input rod sensor to monitor how much the brake pedal is applied by the driver and the at least one sensor (3) is a master cylinder pressure sensor to monitor the pressure in a tandem master cylinder (7). The first and second brake circuits (5, 6) are connected to the tandem master cylinder (as shown in Fig 1) through the respective first and second CSV (5a, 6a).
[0029] A pressure unit (8) comprising an actuator (8b) and a motor(8a) provides a target brake pressure. The actuator consists of a plunger piston system which in connected to the high dynamic motor using planetary gear. The pressure unit (8) further comprises a plunger supply pressure sensor (4a). The pressure unit is connected to the first and second brake circuits (5,6) with the respective first and second plunger separation valves (PSV) (5b, 6b). When the system is in brake by wire mode (as explained above), the PSVs (5b, 6b) are kept open and the CSVs (5a,6a) are closed. Further, The pedal (11) is coupled to the pedal feel simulator(9) through a simulator separation valve (SSV) (9a) when in By-wire mode. The pedal feel simulator provides a comfortable pedal feel to the driver. The same is coupled with a simulator pressure sensor (4b).
[0030] When the system is in mechanical mode (mechanical braking), the CSVs (5a, 6a) are opened and the PSVs (5b, 6b) and SSV (9) are closed. A person skilled in the art would appreciate that the brake by wire system also comprises the valves (12a, 12b, 12c, 12d) as the inlet valves and valves (13a, 13b,13c,13d) as the outlet valves for the base brakes (14a, 14b,14c,14d) of the vehicle. The same are not being described in detail for the sake of brevity.

[0031] Said controller (1) is adapted to control the said first and second CSV (5a, 6a), the SSV(9a), the first and second PSV(5b, 6b) and said at least one sensor (2,3,4a-b, 8c-d). A person skilled in the art would appreciate that the controller is also adopted to control the inlet/outlet valves (12a-12d)/(13a-13d). The same can be opened or closed depending on the brake circuit(5,6) to which they are connected to provide the brake pressure to the wheels.

[0032] In an example any of the at least one of the sensors (2,3 4a-b,8c-d) may be a sensor at fault (unhealthy sensor). In such an event, the controller may be configured to receive an input brake pressure request from a healthy sensor (the sensor not at fault) when the fault is detected in the unhealthy sensor. In such an event the controller may enable a brake-by-wire functionality in the first brake circuit (5) and enables a mechanical braking functionality in the second brake circuit (6).However, the account has to be taken of a leakage in the tandem master cylinder(TMC) (7) if the input rod sensor (2) is at fault and brake by wire functionality is being enabled based on the input brake pressure requested being calculated by the master cylinder pressure sensor. Similarly, if the master cylinder pressure sensor (3) is at fault, account has to be taken of a possible defect in the PFS unit (16) which may include a possible leakage in the pedal feel simulator(9) or may be the SSV (9a) is stuck.
[0033] A person skilled in the art would further appreciate that the aforementioned unhealthy/healthy sensors can in an example can be any one of (not limited to) the master cylinder pressure sensor (3) and the input rod sensor (2), that is, either one of the two can be unhealthy (faulty) so as to receive the input brake pressure request from the healthy (not faulty) sensor. The fault can occur in any of the two (or any other sensor) and the same is not be construed as limiting the scope of the invention.
[0034] It is further disclaimed that the brake-by-wire systems as known in the art comprise multiple valves and sensors which are controlled by the controller to enable a braking functionality.
[0035] Referring again to Figure 1, the controller enables the brake by wire functionality during the latent fault in the brake by wire system (10). In order to detect the latent fault, the controller is configured to detect the leakage in the tandem master cylinder (7), based on a change in pressure across the tandem master cylinder, said change in pressure calculated by the at least one sensor.
[0036] The controller is further configured to detect a defect in the PFS unit (16), by measuring a change in a volume of a brake fluid in the PFS (9) , said change in volume calculated by the at least one sensor (4a, 4b) and the controller enables the brake by wire functionality based on the input brake pressure request from at least one sensor(4a, 4b) and the latent fault so detected.
[0037] In an example, in order to detect the leakage in tandem master cylinder (7), the pressure unit (8) can be used as a source to build pressure in the first chamber (7a) of Tandem Master Cylinder (TMC) by opening the PSV1 (5b), the CSV1 and closing the CSV2, PSV 2 and a test separation valve (TSV) (15a) between a reservoir (15) and the TMC(7). The SSV may remain closed. (It is to be noted that whenever the PSV and CSV are open for a brake circuit while monitoring, a person skilled in the art would appreciate that the inlet valves {12a-d} for the said brake circuit will also remain closed).
[0038] The pressurization of the first chamber (7a) of TMC (TMC1) moves the floating piston in the second chamber (TMC2) (7b). This pressure in the Tandem master cylinder is calculated in the Master cylinder pressure sensor (3). By holding the pressure in the tandem master cylinder, any pressure drop observed during the holding period due to a leakage in TMC may be recorded and calculated by the master cylinder pressure sensor (3). In order to detect leakage more robustly, the Pedal feel simulator (PFS) (9) and the base brakes (14c, 14d) on the first brake circuit shall be filled (by opening the SSV and the CSV 1) to ensure no adverse base brake effects while monitoring.
[0039] In an example, in order to detect a defect in the PFS unit (16), the volume of brake fluid consumed by the PFS unit can be calculated by 4a and 4b by opening the PSV1, CSV1 and closing the TSV, CSV2. The volume consumption from the pressure unit may be calculated from Actuator pressure sensor (4a) , simulator pressure sensor (4b) and in addition, with the Motor current sensor (8d) or the motor position sensor (8c). Based on the volume consumption, one can estimate the leakage in the TMC (7). The SSV may remain closed at first. When the pressurization of the first chamber (a) of TMC (TMC1) moves the floating piston in the second (TMC2), the SSV might be opened. The pressure and volume consumption in PFS must be observed for pre-determined time. The pressure drop in the Pedal feel simulator may be measured by 4a and 4b. Further the motor current sensor may be used to estimate the volume/pressure in the PFS.
[0040] In an example, assuming that the input rod sensor (2) is detected by the controller to be an unhealthy sensor (for instance, the input rod sensor (2) has a fault), the controller may enable the brake by wire functionality in the second circuit (6) and a mechanical braking functionality in the first circuit (5). In order to enable the brake by wire functionality in the at least one brake circuit (5,6), an input brake pressure request can be measured by the master cylinder pressure sensor (3) being the healthy sensor. However, relying on the master cylinder pressure to enable brake by wire functionality in the second brake circuit would not be possible if a leakage is detected in the TMC as explained above. If no leakage is detected in the TMC based on the input brake pressure request, the controller can signal the motor and actuators in the pressure unit to provide a target brake pressure by providing the appropriate power to move the piston in a chamber of the tandem master cylinder.
[0041] In another example, assuming that the master cylinder pressure sensor (3) is detected by the controller to be an unhealthy sensor (for instance, the master cylinder pressure sensor(3) has a fault), the controller may enable the brake by wire functionality in at least one of the first and the second brake circuit (5,6). In order to enable the brake by wire functionality in the second circuit (6), an input brake pressure request can be measured by the first sensor (for instance the input rod sensor (2)) being the healthy sensor. However, the latent fault in the PFS unit has to be detected as explained above. If no defect is detected in the PFS unit, the pedal feel simulator coupled with the simulator pressure sensor (4b) can further be relied to calculate the input brake pressure request and further no leakage in the tandem master cylinder. The simulator separation valve will be opened. Based on the input brake pressure request, the controller can signal the motor and actuators in the pressure unit to provide a target brake pressure by providing the appropriate power to move the piston in a chamber of the tandem master cylinder. A person skilled in the art would appreciate that the controller is also adopted to control the inlet/outlet valves (12a-12d)/(13a-13d)the same can be opened or closed depending on the brake circuit(5,6) to which they are connected to provide the brake pressure to the wheels (15). The aforementioned example thus can advantageously provide the brake by wire functionality safely, in spite of a latent fault in the brake by wire system such as a possible leakage in the tandem master cylinder or a fault in the pedal feel simulator or the simulator separation valve.
[0042] Referring to figure 2, the same depicts a method to enable a brake by wire functionality during a latent fault in the brake by wire system, the brake-by wire system (10) as described in Figure 1. The method step (100) to enable the brake by wire functionality during a latent fault in the brake by wire system includes the step (101) of detecting the latent fault. If the latent fault is a leakage in master cylinder pressure sensor, the method step (101a) is detecting a leakage in the tandem master cylinder, by the at least one sensor, based on a change in pressure across the at least one tandem master cylinder, said change in pressure calculated by the at least one sensor. If the latent fault in the brake by wire system is a defect in the PFS unt (for instance a PFS leakage or SSV valve stuck) the method step (101b) is detecting a defect in the detecting the defect in the PFS unit, by the at least one sensor, by measuring a change in a volume of a brake fluid entering the PFS. This is followed by the step (102) of enabling the brake by wire functionality in at least one brake circuit of the brake by wire system, by the controller, based on the input brake pressure request from the at least one sensor and the latent fault. If there is a fault in the first sensor (for instance the input rod sensor is at fault), detection of leakage in the tandem master cylinder is done by the second sensor (for instance the master cylinder pressure sensor) before enabling the brake by wire functionality in at least one of the two brake circuits (5,6). Further detecting the defect in the PFS unit can be done by 4a and 4b during the fault in the master cylinder pressure sensor. The brake by wire functionality can be enabled by the controller, based on the input brake pressure request from the at least one sensor (either the master cylinder pressure sensor or input rod sensor) and the latent fault. To enable the detection of the leakage in the tandem master cylinder or detection of the defect in the PFS unit, the controller controls the opening and closing the at least one valve for a predefined time.
[0043] In an example, assuming that the input rod sensor (2) is detected by the controller to be an unhealthy sensor (for instance, the input rod sensor (2) has a fault), the controller may enable the brake by wire functionality in the second circuit (6) and a mechanical braking functionality in the first circuit (5). In order to enable the brake by wire functionality in the at least one brake circuit (5,6), an input brake pressure request can be measured by the master cylinder pressure sensor (3) being the healthy sensor. However, relying on the master cylinder pressure to enable brake by wire functionality in the second brake circuit would not be possible if a leakage is detected in the TMC as explained above. If no leakage is detected in the TMC based on the input brake pressure request, the controller can signal the motor and actuators in the pressure unit to provide a target brake pressure by providing the appropriate power to move the piston in a chamber of the tandem master cylinder.
[0044] In another example, assuming that the master cylinder pressure sensor (3) is detected by the controller to be an unhealthy sensor (for instance, the master cylinder pressure sensor(3) has a fault), the controller may enable the brake by wire functionality in at least one of the first and the second brake circuit (5,6). In order to enable the brake by wire functionality in the second circuit (6), an input brake pressure request can be measured by the first sensor (for instance the input rod sensor (2)) being the healthy sensor. However, the latent fault in the PFS unit has to be detected as explained above. If no defect is detected in the PFS unit, the pedal feel simulator coupled with the simulator pressure sensor (4b) can further be relied to calculate the input brake pressure request and further no leakage in the tandem master cylinder. The simulator separation valve will be opened. Based on the input brake pressure request, the controller can signal the motor and actuators in the pressure unit to provide a target brake pressure by providing the appropriate power to move the piston in a chamber of the tandem master cylinder. A person skilled in the art would appreciate that the controller is also adopted to control the inlet/outlet valves (12a-12d)/(13a-13d)the same can be opened or closed depending on the brake circuit(5,6) to which they are connected to provide the brake pressure to the wheels (15).
[0045] The disclosure advantageously provides the brake boost even in case of sensor failures in the brake by wire systems, including any latent failures such as tandem master cylinder leakage and fault in the pedal feel simulator.
, Claims:WE CLAIM:
1. A controller (1) to enable a brake by wire functionality during a latent fault in the brake by wire system, the brake-by wire system (10) comprising:

-the controller(1) in communication with at least one sensor (2,3,4a,4b) comprising a first sensor (2), a second sensor(3) and at least one third sensor(4a, 4b),

- the controller (1) adapted to receive an input brake pressure request from the at least one sensor (2,3) and control the at least one valve (5a, 5b, 6a, 6b, 9a, 12a-d, 13a-d) of the brake by wire system,
- a pedal (11) coupled with the first sensor (2),
-at least one brake circuit (5,6) in a connection with a tandem master cylinder(TMC), said TMC (7) coupled with the second sensor (3),
-a pedal feel simulator unit (PFS unit)(16) coupled with the at least one third sensor(4a) and the at least one valve , said at least valve comprising a simulator separation valve (9a),
characterized in that,
the controller (1) detects a latent fault in the brake by wire system(10), the controller configured to:
-detect a leakage in the tandem master cylinder (7), based on a change in pressure across the tandem master cylinder, said change in pressure calculated by the at least one sensor (3),
-detect a defect in the PFS unit, by measuring a change in a volume of a brake fluid in the PFS, said change in volume calculated by the at least one sensor (4a, 4b); and
-the controller enables the brake by wire functionality based on the input brake pressure request from at least one sensor and the latent fault.

2. The controller(1) as claimed in Claim 1, wherein, the change in pressure across the tandem master cylinder(7) is calculated by the second sensor(3), during a fault in the first sensor(2).

3. The controller as Claimed in Claim 1, wherein, the change in the volume of the brake fluid in the PFS is calculated by the at least one third sensor(4a, 4b) during a fault in the second sensor (3).

4. The controller as claimed in Claim 1, wherein, the controller(1) enables the detection of the leakage in the tandem master cylinder(1) by controlling the opening and closing of the at least one valve (5a, 5b, 6a, 6b, 9a, 12a-d, 13a-d ) for a pre-defined time.

5. The controller as claimed in Claim 1, wherein, the controller (1) enables the detection of the defect in the PFS unit by controlling the opening and closing the at least one valve (5a, 5b, 6a, 6b, 9a, 12a-d, 13a-d) for another pre-defined time, said at least one valve comprising the at least one SSV (9a).

6. The controller as claimed in Claim 1, wherein, the controller enables the brake by wire functionality in the at least one brake circuit (5, 6) of the brake by wire system (10) based on the input brake pressure request from at least one sensor (2,3) and the latent fault.

7. The controller as claimed in Claim 1, wherein, the controller enables a mechanical braking functionality in the at least one brake circuit (5,6) of the brake by wire system based on the input brake pressure request from at least one sensor(2,3) and the latent fault.

8. A method (100) to enable a brake by wire functionality during a latent fault in the brake by wire system, the brake-by wire system comprising:

--a controller in communication with at least one sensor comprising a first sensor, a second sensor and a third sensor,
- the controller adapted to receive an input brake pressure request from the at least one sensor and control at least one valve of the brake by wire system,
- a pedal interface coupled with the first sensor,
- at least one brake circuit in a connection with a tandem master cylinder(TMC), said TMC coupled with the second sensor,
-a pedal feel simulator unit (PFS unit) coupled with the third sensor and at least one valve, said valve comprising a simulator separation valve;
characterized in the method (100),
-the latent fault detected (101) by:
-detecting a leakage in the tandem master cylinder, by the controller, based on a change in pressure across the at least one tandem master cylinder, the change in pressure calculated by the at least one sensor (101a),
-detecting a defect in the detecting the defect in the PFS unit, by the controller, by measuring a change in a volume of a brake fluid entering the PFS, the change in volume measured by the at least one sensor (101b); and
-enabling the brake by wire functionality in at least one brake circuit of the brake by wire system, by the controller, based on the input brake pressure request from the at least one sensor and the latent fault(102).

9. The method (100) as claimed in Claim 1, wherein, detecting the leakage in the tandem master cylinder, by the second sensor, during a fault in the first sensor;

detecting the defect in the PFS unit, the third sensor, during the fault in the second sensor; and

enabling the brake by wire functionality, by the controller, based on the input brake pressure request from at least one sensor and the latent fault.

10. The method (100) as claimed in Claim 1, wherein, enabling a detection of the leakage in the tandem master cylinder and detecting the defect in the PFS unit, by the controller, by controlling the opening and closing the at least one valve for a predefined time.