Patent Application
20150219487
The present invention relates to railcar weighing systems and, more particularly, to on board railcar weighing systems.
It is desirable to be able to obtain the weight of loading in a railway freight car or tank car. It is especially desirable to be able to obtain the weight of loading in a railway freight car or tank car on a real time basis, without need for the railcar to be in a specific location, such as a scale.
It is also desirable to be able to transmit a signal indicative of the weight of loading in the railcar or tank car to a bolster wherein such signal can be stored.
Accordingly, it is an object of the present invention to provide a method and apparatus for measuring the weight of loading in a railway freight car or tank car and to transmit a signal indicative of such weight to a receiver.
This invention covers several embodiments of a system for measuring the static or dynamic load of a railway car. In one embodiment, displacement/strain type transducers are mounted symmetrically to the bolsters of the trucks supporting the railway car body. In this embodiment, the lateral and longitudinal load imbalances are measured, in addition to the weight of the railway car body. Wireless sensors are used to read and transmit the output of the transducers. The readings are sent to either a local receiver, or a remote location.
A general three piece truck system is shown in
The first embodiment of the invention is shown in
Each wireless strain/displacement sensor 7 includes a strain/displacement transducer 8 and wireless sensing unit 9 as shown in
The wireless sensing unit 9 interfaces directly with the transducer 8 with the primary function of reading and digitizing the output signal from the transducer 8. In the preferred embodiment, the wireless sensing unit 9 contains a microprocessor unit with associated analog-to-digital (A/D) convertors and signal conditioning, a power source, and a communications unit in the form of a wireless transmitter/receiver. The wireless sensing unit 9 may also contain additional sensing elements including inertial, temperature, or pressure sensors. These additional sensors may be used for logic and decision making on the integrity of transducer 8 data. For example, transducer signals collected outside of the operating temperature limits of the transducer may be discarded using logic within the wireless sensing unit 9. The wireless sensing units 9 communicate with a local communications manager 15 which will be described hereafter.
A second embodiment of the invention is shown in
The preferred embodiment illustrated in
As noted previously, the preferred embodiment utilizes sealed calibration parameters in the communications manager 15 to convert the digital sensor data into weight readings. In the present invention, sensors 7 are mounted to structurally supportive areas of the railway car that have been analytically and experimentally proven to react with a high degree of repeatability to an applied load. However, it is recognized that there is an intrinsic variation in the relationship between applied load and strain/displacement that warrants unique calibration of each component. In the preferred embodiment, this necessitates calibrating individual truck assemblies. Calibration of an individual truck assembly can be achieved using a dedicated hydraulic load frame for applying loads to the center plate 4 and side bearings 5a-5b of the bolster 1, while the truck is supported on rails through the axle assemblies 6a-6b. The preferred method is the adoption of industry accepted calibration routines, such as ASTM E74-Standard Practice of Calibration of Force-Measuring Instruments for Verifying the Force Indication of Testing Machines. In this preferred method, at least 5 ascending and descending calibration points are used and repeated at least 3 times. The use of such calibration practices ensures the highest degree of accuracy possible in the weight readings for a given truck assembly. By calibrating the truck systems before assembling the railway car, the system will thus measure the railway car body weight, as opposed to the gross rail load (GRL). Alternative methods, including calibration in the field with 1 or 2 calibration points will have significantly lower statistical certainty. However, simplified field calibrations may be used in cases where the highest degree of accuracy is not required. In commercial weighing applications used for custody transfer, evaluation in accordance with a National Type Evaluation Program (NTEP) may be necessary, which requires both laboratory and field verification testing.
The most basic form of transducer data processing has been described with reference to
As static conditions are generally assumed with respect to the motion of the railway car, static environmental conditions are also generally assumed and preferred. However, it is commonly accepted that strain gage based transducers will exhibit some degree of zero-output shift with temperature change. In the preferred embodiment, a temperature detector 13 within the transducer 8 is sampled with each transducer reading in order to apply correction algorithms in the wireless sensing unit 9. In the simplest form, correction algorithms utilize first-order linear relationships between transducer 8 output and temperature, although higher order fitting may be necessary in some cases. Similar approaches could be used for correction for elevation, or correction of thermal output for different transducer types described previously. The highest degree of correction is achieved by calibrating the entire truck assembly (with sensors) in a thermal chamber or similar fixture. In the preferred embodiment, temperature correction provides the desired system accuracy (say 1% of full-scale) from −10 to 40° C., in accordance with NCWM Publication 14 and NIST Handbook 44.
Both static and weigh-in-motion type weight measurement have been described in previous sections. Additionally, transient forces occurring at the wheel-rail interface are transferred from the axle assemblies 6a-6b into the side frames 2a-2b, through the spring group 3a-3b, and into the bolster 1 during service. Both embodiments of the invention (
As noted above, the wireless sensing units 9 transmit and receive data with a communications manager 15 mounted locally on the railway vehicle car body. This short range allows for the use of low-power radios conforming to standards such as IEEE802.15.4, for operation in the 2.4 GHz license-free band. In the preferred embodiment, the sensing units 9 are capable of being wireless routers, communicating with all other sensing units 9 for a redundant communication path to the manager 15. The manager 15 also continuously monitors and optimizes the network, dynamically changing data paths, and adjusting when sensing units 9 talk, listen, or sleep.
Additionally, the preferred embodiment provides end-to-end data security with 128 bit AES-based encryption, or similar methods common to the art. Similar low-power wireless networks can be employed, and data transmission is not limited to the methods discussed herein.
In the preferred embodiment, the communications manager 15 includes a computation element such as a micro-controller, memory, a stand-alone power supply, and sensors. Sensors may include ambient temperature, barometric pressure, proximity, or inertial sensors. Additionally, the manager 15 incorporates several communication methods including the aforementioned wireless sensor network, cellular (GSM/GPRS), satellite, and Bluetooth or WiFi for local communications. The manager 15 may also incorporate a wireless sensing unit 9 for creating a network of managers 15 along the train. With an additional manager 15 in the locomotive or the like, data from all aforementioned sensors can be monitored in the locomotive. Various methods can be used for communications along the train.
The manager 15 also may include a location measurement means such as a global positioning system (OPS). The positioning system can be used to determine railway car speed and location. Both speed and location can be used within algorithms to adjust wireless sensing unit 9 sampling rates, or inhibit data output all-together. For example, the weight of the railway car may not be of interest when being stored in a yard, so the position information could be used to inhibit the sampling and output of weight readings, thus preserving energy on both the communications manager 15 and wireless sensing units 9. Alternatively, weight readings may be needed every minute while the railway car is being loaded, so it is necessary for the manager 15 to be able to adjust sensor 9 sampling rates based on a combination of parameters and user inputs. In the preferred embodiment, the end user can adjust the sampling rate from a local digital weight indicator 17 as desired, although other autonomous methods may be needed in different environments.
It has been previously noted that the wireless strain/displacement sensors 7 can be used to measure dynamic forces at the rail/wheel interface. When combined with the aforementioned inertial sensor within the manager 15 or wireless sensing unit 9, an added level confidence is achieved regarding the reported state of the truck system. For example, periodic lateral forces in the bolster 1 may be detected by the sensors 7, and the associated car body response measured with an inertial sensor may be used to corroborate the event. The relationship between wheel/axle inputs and car body response can be readily determined with both computational and empirical techniques. This information can be used to create transfer functions within the manager 15 or wireless sensing unit 9 to accurately predict inputs.
