Abstract:
A method and system for coordinating the transfer of control of a remotely controlled locomotive is disclosed. The generation and assignment of command authority between remote controllers is accomplished by signal transfer between the remote controllers themselves, in contrast to a system that requires the use of a slave controller to determine, assign, and/or transfer command authority. In an exemplary embodiment, a transfer request is transmitted from a first control unit to a second control unit, the first control unit initially having a command authority. An acceptance of the transfer request is transmitted from the second control unit to the first control unit, and a confirmation of transfer is transmitted from the first control unit to the second control unit. Following the transmission of the confirmation of transfer from the first control unit to the second control unit, the second control unit assumes the command authority from the first control unit.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. provisional application No. 60/379,628 filed May 10, 2002 the contents of which are incorporated by reference herein in their entirety. 

   BACKGROUND OF THE INVENTION 
   The present disclosure relates generally to remote controlled locomotives and, more particularly, to a method and system for coordinated transfer of control of a remote controlled locomotive. 
   The remote control operation of a locomotive is useful for allowing a ground-based operator to control the locomotive from trackside in a switching yard. A remote control unit typically includes one or more hand held transmitting units for communicating with a controller on the locomotive. This type of system permits an operator to perform such operations as coupling and uncoupling cars while retaining control over the speed of the locomotive by manually regulating the throttle and brake systems. 
   Since a remote control system can be used in conjunction with a train having multiple cars, it may be the case that an individual system operator cannot adequately view all of the cars at once. Accordingly, there are systems in existence that allow two or more operators to monitor different sections of the train. For example, in a two-operator system, each operator has a hand held transmitting unit, each of which has the capability of transmitting the full set of remote control commands to the locomotive. For obvious reasons, the system is designed such that (with the exception of certain commands) the controller on the locomotive will only accept commands from one of the transmitters at any given point in time. However, because it is desirable to be able to selectively designate which of the hand held controllers will have “command authority”, there is a need to coordinate and control such a transfer of command authority in an appropriate and effective manner. 
   U.S. Pat. No. 5,685,507 issued to Horst, et al. discloses a remote locomotive control system in which the transfer of command authority from one transmitter to another is processed and executed by a slave controller mounted on board the locomotive. The slave controller initially assigns a “command authority holder status” to one of the transmitters and a “command authority non-holder status” to another of the transmitters. The slave controller keeps track of the current command authority holding transmitter by including a memory portion that associates a specific transmitter identifier with the command authority holder. When it is desired to change the command authority from the current command authority holder to a current command authority non-holder, the slave controller receives a transfer command signal from the transmitter having the command authority. Assuming certain safety checks are first met, if a command authority non-holder transmitter acknowledges (within 10 seconds) the transfer request by an appropriate signal (in this case, by transmitting a “reset” bit set at high), then the CPU within the slave controller shifts in memory the identifier associated with the reset bit at high to the position of the current command holder. 
   Essentially, the slave controller is the entity that determines which transmitter has the control authority. Each command signal sent by a given transmitter includes an identifier therewith, which identifies the specific transmitter sending the command signal. Depending upon the command sent, the slave controller then examines the identifier to see whether the command comes from the command authority holder. 
   A drawback, however, of the system in &#39;507 patent stems from the fact that it is the slave controller (remotely located on board an unmanned locomotive) that ultimately has the responsibility of assigning and determining which transmitter has the command authority, as well as implementing a change in the command authority. If there is any problem with system hardware, software, or even with external operator-to-operator coordination, then there is no person “in the loop” to manage an unexpected or erroneous transfer of authority. 
   BRIEF DESCRIPTION OF THE INVENTION 
   The above discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by a method and system for coordinating the transfer of control of a remotely controlled locomotive. The generation and assignment of command authority between remote controllers is accomplished by signal transfer between the remote controllers themselves, in contrast to a system (such as the &#39;507 patent) that requires the use of a slave controller to determine, assign, and/or transfer command authority. 
   In an exemplary embodiment, a transfer request is transmitted from a first control unit to a second control unit, the first control unit initially having a command authority. An acceptance of the transfer request is transmitted from the second control unit to the first control unit, and a confirmation of transfer is transmitted from the first control unit to the second control unit. Following the transmission of the confirmation of transfer from the first control unit to the second control unit, the second control unit assumes the command authority from the first control unit. 
   In another embodiment, a method and system is disclosed for coordinating the transfer of control of a remotely controlled locomotive between a first operator control unit having primary command authority asserted to a locomotive control unit, and a second operator control unit not having primary command authority asserted to the locomotive control unit. A pitch, initiated by an operator of the first operator control unit, is received by the first operator control unit. A catch request is then transmitted from the first operator control unit to the second operator control unit. The second operator control unit transmits to the first operator control unit an acceptance of the catch request by an operator of the second operator control unit. Then, the operator of the first operator control unit receives a confirmation of the pitch. Following the confirmation of the pitch, the second operator control unit asserts primary command authority to the locomotive control unit and the first operator control unit does not assert primary command authority to the locomotive control unit. 
   In still another embodiment, a remote control system for a locomotive includes a first operator control unit for transmitting a set of commands to a locomotive control unit within the locomotive. A second operator control unit is for transmitting a set of commands to the locomotive control unit. One of the operator control units has a primary command authority at a given time, with each of the first and said second operator control units providing a signal to the locomotive control unit indicative of whether it has the primary command authority. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring to the exemplary drawings wherein like elements are numbered alike in the several Figures: 
       FIG. 1  is a schematic diagram of an exemplary remote controlled locomotive system  100  suitable for use in conjunction with the present invention embodiments; 
       FIG. 2  is a signal state diagram which illustrates a method and system for coordinated transfer of control of a remote controlled locomotive, in accordance with an embodiment of the invention; and 
       FIG. 3  is a flow diagram which alternatively illustrates the method and system shown in FIG.  2 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring initially to  FIG. 1 , there is shown a schematic diagram of an exemplary remote controlled locomotive system  100  suitable for use in conjunction with the present invention embodiments. The system  100  includes both a first hand held operator control unit (OCU)  102  and a second OCU  104  for transmitting digitally encoded radio frequency (RF) signals to convey commands to a locomotive control unit (LCU)  106  mounted on board a locomotive  108 . The LCU  106  decodes the transmitted signals from the OCUs and (depending on which OCU has command authority) operates various actuators (e.g., throttle  110 , brake  112 ) to implement the commands transmitted by the OCU having command authority. Although there are two OCUs depicted in  FIG. 1 , the system  100  could also include an additional number of OCUs. 
   In addition,  FIG. 1  also illustrates an optional, on board signal repeater  114  that may be used to relay communications between the OCUs  102 ,  104  and the LCU  106 , or between the OCUs themselves. Similarly, an off board repeater (not shown) could also be used as a signal relaying device. 
   As stated above, it is desirable for the operators to be able to selectively designate which of the hand held OCUs will have command authority, and to communicate and confirm the transfer of control directly between the OCU&#39;s and the operators. This is contrast to certain existing remote control systems, such as that disclosed in the &#39;507 patent discussed earlier, in which the on-board or locomotive control unit assigns a status of “command. authority holder” to one of the operator control units and a status of “command authority non-holder” to one or more remaining operator control units. The locomotive control unit  106  in this type of command transfer system is further responsive to a “command relinquish” RF signal in order to honor the full set of commands sent from the operator control unit having “command authority holder” status, as well as a subset of commands from the operator control unit(s) having “command authority non-holder” status. If a command transfer request is sent from the “command authority holder” operator control unit to the locomotive control unit, and (assuming any safety checks are also passed) if one of the “command authority non-holder” operator control units subsequently transmits a reset signal, then the locomotive control unit shifts the status of “command authority holder” to that operator control unit that transmitted the reset signal. In effect, the locomotive control unit (i.e., the slave controller) determines from which operator control unit it will accept the full range of commands, based on the operator&#39;s action to give up control. 
   However, a significant drawback of this command transfer method is that the locomotive control unit, mounted within the unmanned locomotive (which may be some distance away from either operator of the operator control units) is ultimately the component that has the final authority for transferring the command authority from one operator control unit to another operator control unit. If there is any problem with system hardware, software, or even with external operator-to-operator coordination, then there is no person “in the loop” to manage an unexpected or erroneous transfer of authority and no confirmation to the operators that transfer has in fact been implemented. 
   Therefore, in accordance with an embodiment of the invention, there are disclosed methods and systems of transferring control of a locomotive in a operator-to-operator coordinated fashion such that human operators are left “in the loop” so as to have final authority to transfer control, and with confirmation of transfer of control to the operators but without the need for relying on external coordination for scheduling the transfer. 
   Broadly stated, under the processes and systems of the present invention embodiments, the transfer of remotely controlled locomotive control is implemented without having to communicate with the LCU  106  at all. Rather, a series of requests and acknowledges are sent through an OCU to OCU order-wire. Although the system requires that the operator first confirm that the locomotive is in an appropriate state (e.g., stopped) before transfer of control is accomplished, it is the operator and not the LCU  106  that has the final say in the transfer. 
   Referring now to  FIG. 2 , there is shown a state diagram illustrating the principles of the transfer of command between a primary OCU and a secondary OCU. It will be appreciated that although only two OCUs are shown in  FIG. 2 , the principles of the present invention embodiments are equally as applicable to a remote control system using several LCUs, one of which retains the primary command control at a given time. 
   The first OCU  102 , by way of example, is initially designated as a “primary” OCU, in that it holds the primary command authority. Within each command message transmitted to the LCU  106  by first OCU  102 , an “in control” indicator is included. In other words, the first OCU  102  generates a command authority signal included within each command message. Preferably, the first OCU  102  (initially being the primary OCU) also includes a physical indication, such as an illuminated LED  118  (FIG.  1 ), to signify to an operator of the first OCU  102  that he/she has the primary command authority. Correspondingly, the second OCU  104  is initially designated as a “secondary” OCU, in that it does not hold the primary command authority. The second OCU  104  may, however, be capable of transmitting certain universal commands, such as to engage an emergency brake or to sound a horn. Whenever a command is transmitted from a secondary OCU (such as second OCU in the initial state), a “not in control” indicator will be included with such a command. This can be in the form of a specific “non-command authority signal”, or alternatively, by the absence of a command authority signal included within a transmitted command. In addition, while retaining the status of a secondary OCU, an “in control” LED  120  ( FIG. 1 ) on the second OCU  104  will remain extinguished until such time as the second OCU obtains the primary command authority. 
   It will now be assumed that the operator of the primary OCU (first OCU  102 ) wants to transfer primary command authority to the operator of the secondary OCU (second OCU  104 ). As shown in  FIG. 2 , the operator of the primary OCU initiates a “pitch” by pressing a primary command change (PCC) button on the first OCU  102 . Before transmitting the pitch to the second OCU  104 , the first OCU confirms certain desired parameters (e.g., the locomotive not moving, the pressure in the brake system is at a predetermined level, etc.). If, for example, the locomotive is moving when the pitch is initiated, the first OCU will prompt the operator to stop the locomotive before pitching over the transfer request. 
   Assuming the desired preconditions are satisfied, the first OCU  102  then transmits a “catch” request directly to the second OCU  104 , signifying a request for the second OCU  104  to now become the primary OCU. When the catch request is received by the second OCU  104 , it then verifies or replays the catch request back to the first OCU  102 , along with a “wait” signal, while the operator of the second OCU  104  decides whether or not to accept the catch request and assume primary command authority. If the operator of the second OCU  104  decides to accept the catch request, then he/she passes this information along to the operator of the first OCU  102  by pressing a corresponding PCC button on the second OCU  104 . The second OCU  104  then prompts its operator to wait for the pitch (i.e., the transfer of primary command authority). 
   On the other hand, if the operator of the second OCU  104  does not acknowledge the catch request after a predetermined time period, then the system times out and the transfer process is aborted. However, assuming that the catch request is accepted, then the operator of the first OCU  102  must also confirm the pitch by once again pressing the PCC. This allows for a human-based final decision to transfer the primary command authority. If the pitch is not finally confirmed within a certain time period, then the transfer process is aborted. If the pitch is confirmed, then the transfer process is completed. As reflected in  FIG. 2 , the first OCU  102  now becomes the secondary OCU, wherein the “in control” LED  118  is then extinguished. Furthermore, the first OCU  102  asserts in a command message to the LCU  106  that it no longer has primary command authority. At the same time, the second OCU  104  now becomes the primary OCU. The “in control” LED  120  associated therewith is now illuminated, and a command message is sent to the LCU indicating that the second LCU  104  has primary command authority. Finally, if at some point it is desired to transfer the primary command authority from the second OCU  104  back to the first OCU  102 , then the above-described process is again implemented, beginning with the operator of the second OCU  104  initiating a pitch request. 
   An alternative representation of the state diagram of  FIG. 2  is depicted by the flow diagram of  FIG. 3 , as reflected in blocks  302  through  318 . 
   As can be seen, the above-described method provides for the transfer of command authority directly between a pair of operator control units without the need for an external coordination to schedule the transfer. In the event of a malfunction wherein two or more linked OCUs assert an “in control” command message to the LCU  106 , then the LCU  106  will report a fault and go to a “park” state. Optionally, the pitch and catch messages transmitted between OCUs may be passed through either on board signal repeater  114  or an off board signal repeater (not shown), where direct communications between OCUs are hampered. It will be appreciated by those skilled in the art that such a signal repeater would function a signal pass-through entity, and not as a device for responding to a transfer request signal or for assigning command authority to a transmitter. In other words, the operators are still charged with the ultimate transfer decision-making. 
   While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.