Abstract:
An apparatus for determining the rotation of a wheel truck on a rail vehicle and further for determining the relative direction of motion of said truck with respect to said rail vehicle and further for determining the rate at which the truck moves with respect to the rail vehicle is disclosed, which is a low power radar sensor disposed underneath the rail vehicle and directed toward the truck. In a Preferred embodiment, two sensors are shown which are disposed on opposite sides of the rail vehicle. The sensors are coupled with an onboard computing device and with other components of a train control system which can be used for precisely locating the train on closely spaced parallel tracks and further for updating and augmenting position information used by the train control system. The system including GPS receivers and wheel tachometers for providing alternate sources of information for position determination.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The application of present invention relates to and incorporates herein by these references co-pending patent applications entitled “Method and Apparatus for Controlling Trains by Determining a Direction Taken By a Train Through a Railroad Switch” by David H. Halvorson, Joe B. Hungate, and Stephen R. Montgomery, and entitled “Method and Apparatus For Using Machine Vision to Detect Relative Locomotive Position On Parallel Tracks” by Jeffrey D. Kernwein, both of which were filed on even date herewith, and are subject to assignment to the same entity as the present application. 
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to railroads, and more specifically relates to train control systems and even more particularly relates to automatic and remote sensing of the passage of rail switches. 
     In the past, train control systems have been used to facilitate the operation of trains. These train control systems have endeavored to increase the density of trains on a track system while simultaneously maintaining positive train separation. The problem of maintaining positive train separation becomes more difficult when parallel tracks are present. Often, parallel tracks exist with numerous cross-over switches for switching from one track to another. It is often very difficult for electronic and automatic systems such as train control systems to positively determine upon which of several parallel train tracks a train may be located at any particular time. For example, when tracks are parallel, they are typically placed very close to each other with a center-to-center distance of approximately fourteen (14) feet. 
     In the past, several different methods have been attempted to resolve the potential ambiguity of which track, of a group of parallel tracks, a train may be using. These methods have included use of global positioning system receivers, track circuits and inertial navigation sensors. These prior art approaches of determining which track is being used each have their own significant drawbacks. Standard GPS receivers are normally incapable of positively resolving the position of the train to the degree of accuracy required. The separation of approximately fourteen (14) feet between tracks is often too close for normal GPS receivers to provide a positive determination of track usage. The use of differential GPS increases the accuracy, i.e. reduces the uncertainty in the position determined. However, differential GPS would require that numerous remotely located differential GPS “stations” which include transmitters be positioned throughout the country. The United States is not currently equipped with a sufficient number of differential GPS transmitting stations to provide for the accuracy needed at all points along the U.S. rail systems. 
     The track circuits which have been used in the past to detect the presence of a train on a particular track also require significant infrastructure investment to provide comprehensive coverage. Currently, there are vast areas of “dark territory” in which the track circuits are not available. Additionally, these track circuits are subject to damage at remote locations and are susceptible to intentional sabotage. 
     The inertial navigation sensors proposed in the past have included both gyroscopes and acceleration sensors. The gyroscopes are capable of sensing a very gradual turn; however, gyros with sufficient accuracy to sense such turns are very expensive. Acceleration sensors, while they are less expensive than sensitive gyros, typically lack the ability to sense the necessary movement of a train especially when a switch is being made from one parallel track to another at very low speeds. 
     Consequently, there exists a need for improvement in train control systems which overcome the above-stated problems. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a train control system having enhanced positive train separation capabilities. 
     It is a feature of the present invention to include a train control system having capabilities for sensing the direction a train takes through switches. 
     It is an advantage of the present invention to reduce the ambiguity of track occupancy which is often present when trains operate within a group of parallel tracks. 
     It is another object of the present invention to improve position determination accuracy of trains. 
     It is another feature of the present invention to include a sensor on board the train for sensing the rotation of a locomotive truck as it pivots from its normal position. 
     It is an advantage of the present invention to provide additional information regarding the train position which can be used to supplement and update other positional information, including GPS signals. 
     It is yet another object of the present invention to detect curves in the tracks. 
     It is yet another feature of the present invention to monitor the duration of the rotation of the locomotive truck, as well as the extent of the rotation of the locomotive truck over a period of time after a significant truck rotation has occurred. 
     It is another advantage of the present invention to provide an additional source of information relating to passage of a locomotive through a curve in the track. 
     The present invention is a method and apparatus for controlling trains by detecting the extent, duration and direction of locomotive truck rotation as the locomotive passes through railroad switches and/or turns, which is designed to satisfy the aforementioned needs, provide the previously stated objects, include the above-listed features, and achieve the already articulated advantages. The invention is carried out in an “ambiguity-less” system in the sense that the track ambiguity is greatly reduced by providing information on the passage of switches, and the direction a train has taken through a switch, as well as the passage of turns in the track. 
     Accordingly, the present invention is a method and apparatus for determining the passage of a locomotive through a switch or a turn by monitoring truck rotation. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may be more fully understood by reading the following description of the preferred embodiments of the invention, in conjunction with the appended drawings wherein: 
     FIG. 1 is a plan view of a common parallel track configuration showing a first track, a switch, and a parallel second track. 
     FIG. 2 is a block diagram of the train control system of the present invention. 
     FIG. 3 is a plan view of a locomotive having two trucks and the outline of the locomotive shown as a dashed line. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Now referring to the drawings, wherein like numerals refer to like matter throughout, and more particularly to FIG. 1, there is shown a section of rail tracks generally designated  100 , having a first set of rail tracks  102  and a second set of tracks  104 . Connecting tracks  104  and  102  are switches  106  and  108 . Also shown for discussion purposes are several positions along tracks. Position A represents a position on track  102 . Position B represents a position along track  102  which is disposed between switch  106  and  108 , while position C represents a position on track  104  disposed between switch  106  and  108 , and position D represents a position along track  102 . 
     Also shown in FIG. 1 are positions AA, AB and AC along tracks  102  and  104 . 
     Now referring to FIG. 2, there is shown a train control system of the present invention generally designated  200  which would be found on board a locomotive (not shown). System  200  includes a locomotive data radio  202  which is coupled to an antenna  204  and further coupled to an onboard computer  210 . Also coupled to onboard computer  210  is GPS receiver  206  which is coupled to a GPS antenna  208 . Further coupled to onboard computer  210  is wheel tachometer  212 , LCD display  214 , LED aspect display  216 , brake interface  218 , and locomotive ID module  220 . Radio  202 , antennas  204 ,  208 , GPS receiver  206 , wheel tachometer  212 , displays  214  and  216 , brake interface  218 , and locomotive ID module  220  are well known in the art. Onboard computer  210  is preferably a computer using a P.C. architecture. The processor and operating system and other details are subject to the desires of the system designer. Onboard computer  210  may include a comprehensive rail track data base. Coupled to onboard computer  210  is turnout detector  222 . Turnout detector  222  is described more fully in FIG.  5  and its associated text of the above-referenced patent application entitled “Method and Apparatus for Controlling Trains by Determining a Direction Taken By a Train Through a Railroad Switch”. 
     Now referring to FIG. 3, there is shown a rail vehicle  300 , typically a locomotive, including a front truck  302  and a rear truck  304 . Rail vehicle  300  is shown having a dotted line  306  which designates the periphery of the vehicle. The view in FIG. 3 is a view of the trucks of a locomotive as it enters switch  106  of FIG.  1 . 
     Vehicle  300  has a left side  308 , a right side  310 , a left side front truck front wheel  318 , a right side front truck front wheel  320 , a left side distance sensor  328 , and a right side distance sensor  330 . Distance sensor  328  senses the distance from a point on the vehicle  300  to the left side front truck front wheel  318 , while distance sensor  330  measures the distance from a predetermined point on the vehicle to the right side front truck front wheel  320 . During operation over a straight track, the distance sensors  328  and  330  are generally stable and are preferably equal. As the rail vehicle  300  enters a switch, the front truck  302  begins to rotate. As shown, the distance from sensor  328  to wheel  318  increases while the distance from sensor  330  to wheel  320  decreases. The rotation of the truck  302  is used to determine if the vehicle has entered a switch or is traveling along a curved section of track. The maximum rotation of the truck  302  normally occurs just as the truck  302  is entirely in the switch and has left the rail segments  112  and  114 . After that point, the locomotive body will begin to rotate, reducing the angle of the truck with respect to the body. There will be a second occurrence of this maximum rotation, in the opposite direction, when the lead truck  302  just enters the straight track at Point C of FIG.  1 . 
     The distance sensors  328  and  330  of this invention are of the general type that emit a signal and receive an echo of that signal reflected from the target. Distance to the target is determined by: 
     Measuring the time it takes the signal to travel to and from the target. 
     Dividing the measured time by two since the measured time was for a round trip from the sensor to the target. 
     Distance sensors  328  and  330  are preferably similar to the rail detectors located in turnout detector  222 , which is described in the above-referenced patent application entitled Method and Apparatus for Controlling Trains by Determining a Direction Taken by a Train Through a Railroad Switch. 
     Preferably the distance sensors  328  and  330  are mounted so that the point on the truck  302  which is being monitored is ideally as far from the pivot point as possible, thereby providing for maximum linear deviation. If a pair of sensors  328  and  330  are mounted symmetrically on the vehicle  300 , many of the concerns about operations in ice and snow could cancel out. While the figures show the distance sensors  328  and  330  coupled to the rail vehicle body, they could, in an alternate embodiment, be mounted on the truck and measure a distance to predetermined position on the rail vehicle. 
     The preferred embodiment of this invention utilizes a radar sensor to measure the distance to the target. The preferred radar sensor is a very low power, short range device known as a Micropower Impulse Radar as described in U.S. Pat. Nos. 5,361,070; 5,630,216; 5,457,394; 5,510,800; and 5,512,834 issued to Thomas E. McEwan and assigned to The Regents of the University of California. The preferred implementation of the radar operates utilizing very short pulses of Radio Frequency (RF) energy centered at 5.8 GHz. This frequency was chosen to operate the radar because: 
     This frequency band is available for low power devices to operate without a license from the FCC. 
     The wavelength of a signal in this band is approximately 5.2 centimeters which is small compared to the size of the target. (Lower frequency operation would result in wavelengths greater in length than the target size with significantly reduced reflection and resolution.) 
     The frequency is low enough to not be significantly affected by environmental conditions such as rain and snow. 
     A radar is preferred over other sensor technologies because it is less susceptible to environmental conditions such as rain, snow, dirt, etc. Acoustic and ultrasonic sensors are also affected to a small degree by temperature, barometric pressure, and humidity. These acoustic and other sensors are well known in the art and are discussed in U.S. Pat. No. 5,603,556 issued to Douglas D. Klink and assigned to Technical Services and Marketing, Inc. 
     Two radar sensors are shown in this invention to improve system reliability since they are part of a train safety system. While it is possible to implement this invention with a single distance sensor, having two sensors provide the following advantages: 
     Two sensors reduce the probability of false alarm. One sensor will detect the truck coming towards it, while the other sensor detects the truck moving away from it. 
     Distance data from the sensors can be evaluated in a differential mode to increase reliability and to cancel out any residual environmental effects that are common to both sensors. 
     Two sensors provide redundancy for higher overall system reliability. 
     The on-board computer  210 , or a processor dedicated to sensor  328  or  330 , can monitor the signals from sensor  328  and  330  and accumulate information on the number, magnitude, direction, and sequence of truck rotations to determine where the rail vehicle is with respect to turns and switches identified in the rail track data base. This information can then be used to control the rail vehicle, cross check the rail track data base, augment position determinations and among other things, confirm the course of the rail vehicle. 
     In operation, and now referring to FIGS. 1,  2 , and  3 , the turnout detector  222  of the present invention works closely with the on-board computer  210 , GPS receiver  206 , and a track database which may be included in on-board computer  210  or located at a central location and coupled to the system  200  through locomotive data radio  202 . The GPS receiver  206  provides current position information and together with the on-board computer  210  and the track database can predict when a train is approaching a switch or a curve in the track. These predictions may be used to initiate the turnout detector  222  into a monitoring mode or in an alternative embodiment, the turnout detector  222  may be in continuous operation, but the GPS derived track position predictions may be compared to the output of the turnout detector to determine precisely when a turn has been made or a switch has been passed. In some situations, the on-board computer  210  will be alerted to look for an absence of truck rotation signals. For example, when a train passes straight through a switch without making any changes, the on-board computer can confirm the direction through the switch by detecting no significant truck rotations during an interval when the GPS predicts the train is at or about a predetermined switch. 
     It is thought that the method and apparatus of the present invention will be understood from the foregoing description and that it will be understood from the foregoing description that it will be apparent that various changes may be made in the form, construction, steps and arrangement of the parts and steps thereof, without departing from the spirit and scope of the invention or sacrificing all of their material advantages. The form herein described being a preferred or exemplary embodiment thereof.