DESC:Field of the invention
The present invention relates to optical fiber sensing technology. In particular, the invention relates to Fiber Bragg Grating (FBG) based air brake monitoring system for railway vehicle. The area of concern of this system is about brake engagement and to measure force applied by brake pads on brake disc. The system monitors the performance of each brake in every coach in real time even while the train is running.
Background
An air brake system uses air as the medium to transmit pressure from driver’s control to the service brake. Presently, air brake system is the standard, fail safe braking system used by heavy vehicle all over the world due to its reliability. The system uses compressed air passing through brake pipe (BP) to make changes in vehicle motion. This brake pipe runs across the length of the train and transmits variations in pressure.
Railways air brake system includes two parts - single pipe air brake system and twin pipe air brake system. Single pipe air brake system is used in wagons and twin pipe air brake system is used in coaches for braking purpose. Twin pipe Air brake system consists of two pipes - brake pipe (BP) and feed pipe (FP) charged with fixed amount of air pressure. During brake application, the pressure in the brake pipe (BP) is reduced and further in distributive valve (DV). This connects auxiliary reservoir (AR) with Brake cylinder (BC) to pass the air and apply service brake. During Brake release stage, the pressure in the brake pipe (BP) is increased up to fixed air pressure. The distributive valve (DV) senses the change in air pressure and disconnect Auxiliary reservoir (AR) and Brake cylinder (BC). This time DV connects Brake cylinder (BC) with exhaust to vent out the air and release the brake.
The optical fiber sensors are developed for industrial, consumer, medical and military applications. These sensors are used to detect parameters such as strain, temperature, pressure, vibrations, displacements, rotations, etc. FBG is an intrinsic type of optical fiber sensor which reflect back one particular wavelength of input light, satisfied by Bragg condition, while transmit all other wavelengths. The reflected wavelength is called Bragg wavelength. External perturbations such as strain and/or temperature cause a shift in this Bragg wavelength from the initial value which is detected and monitored using optical interrogators. Thus, FBG sensor senses physical and biochemical perturbation through Bragg wavelength shift.
Various system and methods are known for detection of various parameters using FBG sensors for industrial applications, but have their own limitations. In any case, such systems typically cannot detect and monitor the air brake force in real time and there is a need to monitor the force applied by the brake pads on brake disc of vehicle.
Thus, there is enormous scope of faultless and dynamic air brake monitoring solution which can save on the time taken and also maintenance cost.
The Application No. US6662641B2, entitled “Method and device to measure brake force for railroad vehicles” relates to a bending moment sensing device inserted between the braking surfaces. The processing of bending moment signal represents braking force applied between braking surfaces. But, the method does not provide real time information about brake force.
The Application US20100131167A1 entitled “Air brake Monitoring System” relates to a system for monitoring a pressure of the system and/or warning to the user. The system monitors the pressure in both the service/control line and the emergency/supply line using pressure sensors for measuring the various line pressures, and a processor for receiving the various pressure measurements. The processor is programmed to compare the actual measured pressure of a particular line with a desired threshold pressure level setting and generate warning also. But the system does not provide real time information about air brake system and very complex.
The Application No. CN102145689A, entitled “Detecting method and device for failure of automatic air brake system of train” relates to detecting device for failure of an automatic air brake system of a train and monitoring and alarming equipment for train braking in real time. The invention analyzes train tube pressure at the real time, brake cylinder pressure at different time and compare them to detect fault in brakes with alarm indication. But this device with two class pressure sensors installed in train braking. The method to detect failure is complex.
Therefore, a method and system for real time monitoring of air brake with reduction in maintenance time, wheel protection, predicting braking system failure, identify brake binding and result storage for future references is highly desired.
Summary of invention
The present invention fulfils the foregoing needs by providing a system and method with sensing device for monitoring air brake and measuring air brake force applied by brake pads on brake disc in railway vehicle in real time.
The invention further provides a system and method for monitoring emergency air brake force in railway braking system.
The invention includes an optical fiber sensing based system for detection of force applied by the brake pads on the brake disc in real time. The system includes FBG sensor mounted on the lever of brake caliper unit of rail wheel. The optical fiber sensor, integrated to the lever, gets compressed or elongated as a force is generated on the brake lever during the application and release of the brake, resulting in a shift in Bragg wavelength. The sensor is connected to an optical interrogation instrument using optical fibre cable. The instrument sends an input light signal to the sensor and interrogates the reflected optical signals. Data processing unit (DPU) process the corresponding Bragg wavelength shift to obtain information about the strain (micro strain, µe) developed in the sensor and displays the results at Graphical user interface (GUI) of the server. The micro strain value directly corresponds to the pressure on the brake cylinder through young’s modulus of the fiber and by monitoring the strain value, the efficacy of the air brake can be monitored in real time.
The present invention also provides facility to send alarm to the users. The users having authorized user ID and password can monitor the brake status of each rail wheel and take appropriate action.
Hence a modular design with visual characteristic is leveraged to discriminate between brake applied/released monitoring of air brake system in railway industry. The real time monitoring of performance of each brake also detects air pressure in brake pipe.
Brief description of figures
Exemplary embodiments of the present invention will become more fully understood from the description and the accompanying figures, wherein:
Figure1: Illustrate System architecture.
Figure2: shows the front view of sensor insertion on brake Caliper unit
Figure3: shows variation of Bragg Wavelength vs. time when the brake pressure is changing.
Figure4 (a-d): shows the change in strain, falling time, rising time with change in pressure.
Detailed description of invention
The foregoing description of the embodiments, the various features, and advantageous details of the invention has been presented for the purpose of illustration. It is not intended to be exhaustive or to limit the invention to the precise form disclosed as many modifications and variations are possible in light of this disclosure for a person skilled in the art in view of the figures and description. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by person skilled in the art.
The embodiments herein below provide an optical fiber sensing based system for monitoring of air brake of railway coaches in real time. The system and method for detecting force applied by the brake pads on brake disc in real time.
Fig 1 illustrate the system architecture includes FBG sensor, Optical interrogator, data processing unit (DPU) and the server.
The optical fiber with fiber Bragg grating as shown in fig.1, is obtained by periodically modulating the refractive index of the core of single mode optical fiber using laser beam. At this interface, one particular wavelength of light is reflected, called Bragg wavelength, depending on the effective refractive index of the fundamental mode propagating through the fiber and period of the grating/modulation. The FBG sensors (101) get strain due to the force applied by the brake pads on brake disc, resulting shift in Bragg wavelength.
Further in fig1, optical interrogator (102) act as a light source for optical fiber with FBG sensors and also receive and analyse the reflected light from FBG sensors (101).
Data processing unit (DPU) (103) process all the data received from optical interrogator and connected to server through Ethernet switch (104).
The server (105) displays the change in strain or force with respect to change in Brake pressure.
Fig 2 shows Brake units consisting essentially of the brake cylinder 204, the brake caliper 201 and the brake shoes with snap lock gates. The brake caliper units 201 are held in the vehicle bogies by a three – point-mounting arrangement and drive the brake shoes to generate brake force.
As shown in Fig 2, FBG sensor 207 is attached with Brake Caliper unit 201. When the locomotive driver applies brake, the brake cylinder 204 gets charged and presses the brake pads against the brake disc to generate Brake force. When the driver releases the brake, Brake cylinder 204 pressure get reduces and the brake pads get detached from the brake disc.
Fig 3 shows graph between shift in Bragg wavelength with respect to time obtained directly from optical interrogator. If the brake is released / applied, corresponding change in Bragg wavelength as the sensor gets compressed/elongated.
Further in fig.3, t1-t2 represents the time taken for the brake to be fully applied and t3-t4 represents the time taken for the brake to be fully released. As can be inferred from the same figure, when the brake force is applied, there is increase in the Bragg wavelength corresponding to the elongation (positive strain) in the FBG sensor and when the brake force is released, there is a decrease in Bragg wavelength corresponding to the compression (negative strain) in the FBG sensor.
Hence, the strain measured by the FBG sensor can detect the brakes engagement. In case of engagement, the solution can measure the brake cylinder pressure acting on the brake. This can detect air leakage/blockage in braking system or any other mechanical fault. Further, the solution can detect the performance of each brake by analysing the graph showing time taken by brakes to get engaged/disengaged.
Furthermore, using Machine learning and Artificial Intelligence on the received FBG data, imminent brake failures can be detected early by analysing the pattern of brake application and release waveform. Since the system knows the status of each brake in a train individually, the occurrence of brake binding can be easily detected and locomotive driver can be informed.
Experimentation of force monitoring of air brake system
In one embodiment the air brake test monitoring system, FBG sensors are placed on the lever of brake caliper unit of the wheel of every coach. The sensor is sensing the force developed on the brake lever due to the variation of pressure in the brake pipe from 2.9kg/cm2 to 1kg/cm2 and displaying in terms of strain. Optical interrogator analyse the stress through shift in Bragg wavelength with respect to time for different pressure. DPU converts the shift in Bragg wavelength to corresponding strain developed on the sensor due to the force on the brake lever. With the proposed system various experiments were conducted (as shown in fig.4a, 4b, 4c, 4d) to calculate strain with change in pressure, time of application and release of the force. The time t1-t2 represents brake application time and t3-t4 represents brake release time.
Initially, the experimentation started with 2.9 kg/cm2 of pressure that gives strain about 237.56µ?, with brake application time of 4.9s and brake release time of 22s. When the pressure reduced to 2.4kg/cm2, the resultant strain was about 178.02 µ?, with brake application time 4.58s and brake release time 21.3s. When the pressure reduced to 1.5 kg/cm2, the strain was about 107.20µ?, with brake application time 4.38s and brake release time 20.04s. Further, the pressure reduced to 1kg/cm2, causing a strain of about 57.27 µ?, with brake application time 4.4s and brake release time 21.59s.
Hence, the change in pressure of Brake cylinder, changes the force applied by the Brake pads on Brake disc and FBG sensor detect this force in terms of strain developed on it. This graphical presentation monitors the brake force applied by brake pads on brake disc in real time.
Hence, the proposed system provides closed loop-based monitoring of air brake system using FBG in real time to reduce maintenance and cost issues. The proposed system monitors the performance of brake of each rail wheel in a coach.
,CLAIMS:We Claim
1. A method for real time monitoring of brake force applied by brake pads on disc brake of vehicle, comprising:
providing a sensing device for producing a signal correspond to pressure of Brake cylinder applied on sensing device;
attaching said sensing device on to brake caliper unit of wheel of every coach;
applying pressure to said sensing device create stress and shift in Bragg wavelength of said sensing device;
analysing shift in Bragg wavelength with change in pressure on said sensing device;
converting shift in Bragg wavelength to corresponding microstrain shift developed on said sensing device; and
displaying the change in brake force corresponds to microstrain shift of said sensing device at server.
2. The method for real time monitoring the brake force as claimed in claim1, wherein said sensing device is mounted onto lever of brake caliper unit of the wheel of every coach.
3. The method for monitoring real time monitoring the brake force as claimed in claim 2, wherein said sensing device is FBG sensor.
4. The method for real time monitoring the brake force as claimed in claim2, wherein one strain sensing device is mounted on lever of brake caliper unit correspond to each wheel of coach.
5. A measuring device for real time monitoring the brake force applied by brake pads on disc brake of vehicle, the measuring device comprising:
sensors means positioned on the lever of brake caliper unit;
stress means on said sensing unit with change in air pressure leads to shift in Bragg wavelength; and
analyzer, processor and display means connected with said sensing unit means for analysing, processing of wavelength shift in to corresponding shift in strain and display the change in brake force corresponds to shift in strain at GUI device/server.
6. A system for real time monitoring of brake force applied by brake pads on disc brake of vehicle, comprising:
a sensor inserted on lever of brake caliper unit of the wheel of each coach;
an optoelectronic instrument to analyse the change in Bragg wavelength of sensor;
a data processing unit(DPU) to process change in Bragg wavelength and generate data continuously; and
GUI of the authorized person displays the strain or force with time corresponds to change in pressure of brake cylinder.
7. The system for real time monitoring of brake force applied by brake pads on disc brake of vehicle, as claimed in claim 6, wherein the vehicle is heavy transport vehicles.
8. The system for real time monitoring of brake force as claimed in claim 6, wherein an authorized person is the person having login ID and password.
9. The system for real time monitoring of brake force as claimed in claim 6, wherein an authorized person can remotely monitor brake force at different pressure.
10. The system for real time monitoring of brake force as claimed in claim 6, wherein FBG sensors are inserted using glue and steel tape.