Abstract:
A system for controlling movements of a vehicle along a guideway includes an array of targets that are mounted on the vehicle, and a series of wayside sensors that are mounted on the guideway. A signal processor monitors the passage of targets past appropriate sensors and uses resultant signals to derive parametric values that are characteristic of the vehicle&#39;s movements. The parametric values are then coordinated with a controller for the operation of a linear synchronous motor that propels the vehicle.

Description:
[0001]     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/839,933, filed Aug. 5, 2006. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention pertains generally to transportation systems (e.g. trains) that move heavy objects, such as cargo and passengers, over long distances. More particularly, the present invention pertains to transportation control systems that use stationary, land-based sensors to monitor the movements of a vehicle. The present invention is particularly, but not exclusively useful as a vehicular control system wherein external sensors provide parametric values for coordinating the operation of a vehicle&#39;s propulsion system with its movements along a guideway.  
       BACKGROUND OF THE INVENTION  
       [0003]     As is well known, the basic components of a Linear Synchronous Motor (LSM) correspond to the standard rotor and stator components of an electric motor. Specifically, the operational interaction of these components are correspondingly similar. Unlike a standard electric motor, however, the components of an LSM are laid out substantially in-line. Such a configuration lends itself well for use as a propulsion unit for a vehicle that is designed to travel long distances (e.g. a train). For example, such a system might use a vehicle-based rotor, and a land-based stator.  
         [0004]     Several advantages can be mentioned for using a hard wire, land-based stator as part of the propulsion unit for a long distance vehicle. For one, in general, the land-based stator will not be influenced by weather conditions or terrain variations (e.g. mountains and valleys) that might otherwise interfere with the reception of radiated signals. For another, it is not affected by vehicle travel through tunnels or other such obstructions. Moreover, by having a hard wire stator, it has been determined that an LSM can be made effectively impervious to electromagnetic interference (EMI) and noise.  
         [0005]     Despite the many advantages that can be mentioned for an LSM, the motor has its sensitivities. In particular, it is also important to note that maintenance of the motor phase angle (i.e. the electrical phase angle between the vehicle-based rotor and the land-based stator) is crucial. Maximum thrust for a vehicle propelled by an LSM is achieved when the motor phase angle is maintained at ninety degrees (90°). Otherwise, motor operation can be significantly degraded, with unstable motor fluctuations and possible stoppage. The cure, however, is to have control over the spatial relationship between the rotor and the stator. Stated differently, it is necessary to know the position of the vehicle-based rotor (i.e. the vehicle itself), relative to the fixed, land-based stator.  
         [0006]     In light of the above, it is an object of the present invention to provide a system and method for controlling movements of a vehicle along a land-based guideway, where the vehicle uses a propulsion unit (LSM) with its motor phase angle controlled by vehicle position. Another object of the present invention is to provide a system and method for controlling the motor phase angle of an LSM that is robust and can be used with either a wheeled or levitated vehicle. Still another object of the present invention is to provide a system and method for controlling the motor phase angle of an LSM that is reliable and resistant to high levels of wide band electromagnetic interference. Yet another object of the present invention is to provide a system for controlling movements of a vehicle along a land-based guideway that is relatively easy to manufacture, is simple to use and is comparatively cost effective.  
       SUMMARY OF THE INVENTION  
       [0007]     In accordance with the present invention, a system and method for controlling movements of a vehicle along a guideway employs an external land-based monitor. Specifically, the monitor has sensors, and it has a signal processor. Respectively, the sensors and the signal processor detect and determine parametric values that are indicative of the vehicle&#39;s movements. These parametric values are then used to coordinate vehicle movement with the operation of its propulsion unit (i.e. a linear synchronous motor). The purpose here is to achieve optimal operation of the propulsion unit by maintaining the motor phase angle (i.e. the phase angle between the vehicle-based rotor and the land-based stator) as close to 90° as possible.  
         [0008]     In detail, the system of the present invention requires that a linear array of targets be mounted on the vehicle. In the array, each target is positioned at a known distance “d” from adjacent targets, and all of the targets in the array are aligned through a length “l”. The system and method of the present invention also requires that a first plurality of wayside sensors (i.e. the monitor) be placed along the guideway on which the vehicle will travel. These wayside sensors of the first plurality are separated from each other by a spacing “s”. As envisioned by the present invention, a second plurality of wayside sensors may also be employed. If so, each sensor of the second plurality is placed midway between adjacent sensors of the first plurality. For the present invention, each sensor (primary and secondary) is electronically connected to a signal processor.  
         [0009]     In the operation of the present invention, each wayside sensor will generate a signal whenever a target in the array on the vehicle passes within a predetermined range from the sensor. This signal is then passed to the signal processor. At the signal processor, parametric values that are characteristic of the movement of the vehicle can be derived. In particular, a computer in the signal processor can measure a time interval “Δt” between successive signals. Further, because the distance “d” between adjacent targets in the array is known, a speed for the vehicle can be determined using “d” and “Δt”. It also happens that by monitoring signals from successive sensors, the acceleration, speed and position of the vehicle on the guideway can also be determined by the signal processor.  
         [0010]     Structurally, the targets in the array on the vehicle, and the wayside sensors that are placed along the guideway need to be geometrically related. With this requirement in mind, consider the relationships between the length “l” of the array, the distance “d” between targets in the array, and the spacing “s” between sensors along the guideway. With regard to the length “l” of the array, it is important that it be greater than the spacing “s” between wayside sensors (l&gt;s). This is so in order to provide overlap, and to insure that each sensor will be responsive to at least two adjacent targets during the time interval “Δt”.  
         [0011]     The relationship between “s” and “d” will, in part, help determine the types of targets and sensors that are to be used. For example, in a first preferred embodiment, the distance “d” between targets in the array is less than the spacing “s” between wayside sensors (d&lt;s) along the guideway. Thus, fewer sensors are needed. In this embodiment, the wayside sensors may be relatively more expensive eddy current sensors, and the targets on the vehicle can be relatively inexpensive metal bars. For an alternate preferred embodiment, the distance “d” between targets in the array is greater than “s” (d&gt;s). In this case, the wayside sensors may be relatively less expensive “hall effect” sensors, and the targets on the vehicle can be magnets.  
         [0012]     As mentioned above, the present invention envisions a propulsion unit for the vehicle that is a linear synchronous motor of a type well known in the pertinent art. More particularly, the present invention envisions the signal processor will include a computer that is capable of deriving parametric values with input from the monitor (i.e. the sensor signals). These parametric values (including speed and position of the vehicle) are then sent to a controller that will control a phase angle of the linear synchronous motor, to thereby optimize operation of the linear synchronous motor.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:  
         [0014]      FIG. 1  is a perspective view of a vehicle using the system of the present invention, with portions broken away for clarity;  
         [0015]      FIG. 2A  is a schematic drawing of a first relationship between a target array on the vehicle and sensor placement along the guideway for the present invention;  
         [0016]      FIG. 2B  is a schematic drawing of a second relationship between a target array on the vehicle and sensor placement along the guideway for the present invention; and  
         [0017]      FIG. 3  is a schematic drawing of a single sensor positioned for response to a single target. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]     Referring initially to  FIG. 1 a  system in accordance with the present invention is shown and is generally designated  10 . As shown, the system  10  includes a vehicle  12  that is positioned to travel along a guideway  14 . As envisioned for the present invention, the vehicle  12  may be any of several types well known in the pertinent art. Preferably, vehicle  12  is of the maglev type. In any case, the vehicle  12  will travel along rails  16  in the guideway  14 , of which the rails  16   a  and  16   b  are exemplary. Also, the vehicle  12  will include an array  18  of targets  20  that are affixed to, or mounted on, the vehicle  12 . Preferably, the array  18  is linear and, for the configuration shown in  FIG. 1 , the targets  20  in the array  18  are aligned so they are substantially parallel to the rail  16   a.    
         [0019]     Still referring to  FIG. 1  it will be seen that the system  10  also includes a plurality of wayside sensors  22 , of which the sensors  22   a ,  22   b ,  22   c  and  22   d  are exemplary. As shown, the wayside sensors  22  are placed in-line along a rail  16  of the guideway  14  (placement along the rail  16   a  is illustrated). Further, as shown, two different sets of these sensors  22  can be placed along the rail  16   a . A first set of sensors  22  (also referred to herein as primary sensors) will be connected to a signal processor  24  via a common line  26 . The sensors  22   a  and  22   b  are shown to be primary sensors. On the other hand, a second set of sensors  22  (i.e. secondary sensors  22   c  and  22   d ) will be connected to the signal processor  24  via another common line  28 . When the two sets of sensors  22  are used, they intermesh with each other. Stated differently, each primary sensor ( 22   a  or  22   b ) is placed midway between adjacent secondary sensors (e.g.  22   c  and  22   d ), and vice versa. Thus, as arranged, the sensors  22  can provide redundancy for the system  10 .  
         [0020]      FIG. 1  also shows that the system  10  includes a control  30  for a Linear Synchronous Motor (LSM) (not shown). More specifically, the LSM control  30  is used to move the vehicle  12  in a manner well known in the pertinent art. This propulsion of the vehicle  12  is possible, due to connections between LSM control  30  and the rail  16   a  via line  32   a , and/or rail  16   b  via line  32   b . Importantly, for the system  10  of the present invention, LSM control  30  uses input from the signal processor  24  for its operation. This interconnection is accomplished by line  34  shown between the signal processor  24  and the LSM control  30  in  FIG. 1 . The exact nature of the input provided by signal processor  24  for the operation of LSM control  30  will, however, be best appreciated with reference to  FIGS. 2A and 2B .  
         [0021]     With specific reference to  FIG. 2A , it is to be appreciated that the targets  20  in an array  18  will be aligned to extend through a length “l”. The exact measure of length “l” is somewhat arbitrary and is primarily a matter of design choice. Indeed, the length “l” of the array  18  is preferred to be as long as the vehicle  12 . The distance “d” between targets  20 , however, is not arbitrary. For the example shown in  FIG. 2A , it is important that the distance “d” between targets  20   a  and  20   b , be known with certainty. The same applies to all corresponding distances “d” between any other pair of adjacent targets  20  in the array  18 . Recall, the targets  20  in array  18  are mounted on the vehicle  12 . The sensors  22   a  and  22   b  shown in  FIG. 2A , however, are land-based. Specifically, they are placed along the guideway  14  (see  FIG. 1 ). As shown in  FIG. 2A , there is a spacing “s” between adjacent sensors  22 .  
         [0022]     Still referring to  FIG. 2A , several important relationships between “l”, “s” and “d” must be noted. For one, the spacing “s” between sensors  22  is preferably shorter than the length “l” of the array  18 . This is so to insure that a target  20  in the array  18  is always interacting with a sensor  22 . Further, for operational reasons discussed below, the distance “d” between targets  20  in the array  18  must be known with certainty. The importance of these relationships will be best appreciated with reference to  FIG. 3 .  
         [0023]     In  FIG. 3 , targets  20   a ,  20   b , and  20   c  are selected from an array  18  and are shown as though traveling with a vehicle  12  in the direction indicated by the arrow  36 . On the other hand, it is important to appreciate that the wayside sensor  22   a  shown in  FIG. 3  is stationary. Recall, all of the wayside sensors  22  are placed in-line along the guideway  14 . Further, as intended for the present invention, each sensor  22  will interact with each target  20  as the target  20  passes the particular sensor  22 . Specifically, the system  10  of the present invention envisions that a sensor (e.g. sensor  22   a ) will send a signal via line  26  to the signal processor  24  whenever a target  20  (e.g. target  20   b ) is within a range “r” of the sensor  22   a . Moreover, the present invention envisions this signal will peak when a target  20  is at its closest to a sensor  22 . In any event, each sensor  22  will send a signal to the signal processor  24  each time a target  20  passes the sensor  22  within the range “r”. For the example shown in  FIG. 3 , sensor  22   a  previously sent a signal to the signal processor  24  when the target  20   c  was within range “r”. It is presently shown in a circumstance for sending a signal indicating the passage of target  20   b . The sensor  22   a  will also send another signal when the target  20   a  passes the sensor  22   a . In turn, each sensor  22  will do this, regardless whether it is a primary sensor (e.g. sensor  22   a ) or a secondary sensor (e.g. sensor  22   c ). Importantly, in each case, the distance between targets  20   b  and  20   c  is “d”, and the distance between targets  20   a  and  20   b  is the same “d”.  
         [0024]      FIG. 2A  shows an embodiment for the system  10  wherein the distance “d” between targets  20  on the vehicle  12  is less than the spacing “s” between sensors  22  on the guideway  14  (d&lt;s). In this configuration, fewer sensors  22 , but more targets  20 , may be desired. This embodiment lends itself to the use of relatively more expensive eddy current sensors  22 , with less expensive metal bar targets  20 . For an alternate embodiment,  FIG. 2B  shows a system  10  wherein the distance “d”′ between targets  20   a ′ and  20   b ′ on the vehicle  12  is more than the spacing “s”′ between sensors  22   a ′ and  22   b ′ on the guideway  14  (d&gt;s). In this case the perceptions are reversed. For example, more less expensive “hall effect” sensors  22 ′ can be used with fewer, but relatively more expensive, magnetic targets  20 ′.  
         [0025]     In the operation of the system  10  of the present invention, it is essential to recall that the distance “d” between targets  20  in the array  18  is known, and is the same for all targets  20 . Further, as the vehicle  12  moves along the guideway  14  (e.g. in the direction of arrow  36 ), a sensor  22  (e.g.  22   a , regardless of type) will be able to determine a time interval “Δt” (i.e. time interval) between the passage of successive targets  20  (e.g.  22   c  and  22   b ). Signal processor  24  can then use these measurements to derive parametric values, such as the velocity of vehicle  12 , to characterize the movements of the vehicle  12 . In turn, the present invention envisions passing the derived parametric values for the signal processor  24  to the LSM control  30  for phase angle control of a linear synchronous motor (not shown), to control movements of the vehicle  12  and optimize operation of the system  10 .  
         [0026]     While the particular Linear Synchronous Motor with Phase Control as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.