Process Locomotive Control Systems
 
The process locomotives are controlled by a PLC ( programmable logic controller) and may also have a HMI ( human machine interface) computer.  The PLC operates the locomotive except for those items that are contained within the electronic engine controls.  The HMI computer can interface with the PLC and the electronic engine control system in order to provide a user friendly interface.  The HMI computer is equipped with an office suite, graphics interface software, remote monitoring software, PLC diagonostics and/or programming software, engine diagnostics and/or programming software, and other software that is specific to the application in which the locomotive is to be used. Currently the only graphics interface available is the Wonderware software because it interfaces with the other software on the locomotive.  
HMI computers are common on main line locomotives selling for several million dollars each, but they are very unusual on locomotive switchers and road switchers.  The HMI computer is an industrial computer that can take the forces and vibration of the locomotive environment.  It has similar features to a standard desk top PC. For example a key board, touch screen, CD ROM drive, Superdisk drive, serial ports, parallel ports, 4 gig hard drive, cell phone modem, etc.  The HMI computer serves as a platform to interface with the electronic engine controls, the PLC microprocessor, the cell phone modem for remote monitoring, and other accessories that may be chosen like GPS, a portable AEI tag reader, RF location system (uses AEI tags attached to the cross ties for fixed locations), etc.  The HMI computer can be equipped with maintenance programs that can send reports by fax over the cell phone.  This can be used to alert the maintenance and operations departments when alarms occur or to schedule routine PM maintenance that is tied to specific datesor to engine hours.  The HMI computer can place calls for help in the locomotive is equipped with the man down emergency reporting system option.  The call can be a fax or voice recording and can be sent to any phone number with the proper capabilities on the receiving end.  The HMI computer can print car reports, keep maintenance records, and do just about anything else than can be done on a desktop PC.  Most industrial plants have many PLC microprocessors throughout their processes.  Most also have housekeeping or HMI computers though which the operators interface with the process controls. So placing this type technology on the process locomotive makes the locomotive appear more user friendly to the operators and maintenance personnel.  It is a natural extension of equipment that they are already familiar with.
 

Detroit Diesel DDEC IV control panel is shown in red and the HMI Computer touch screen is located just below it. The operator is checking status conditions using the touch screen.  He can also use the pull out keyboard which is shown below. A cell phone modem allows the HMI computer to interface with other computers and for maintenance personnel to do remote troubleshooting.

The display on the HMI computer is one of the various Wonderware graphics displays.  This one shows throttle, brake, and % traction load conditions.  The computer is also equipped with MS Windows 98 and MS Office 2000 Professional Edition plus much more.  MS WIndows 98 & MS Office are trade marked products of the Microsoft Corp.
   

This photo shows the operator entering information using the pull out keyboard with his right hand while working the throttle with his left hand.  This is the view of the control stand and control panel from the operators chair.  Notice that everything is very clean, clear, and accessable.
 
Most of the controls are located in a walk-in controls locker.  This can be pressurized.  This makes them easy to access for maintenance.  The entrance to the controls locker is just to the left of the control panel.  You can see part of the the controls locker door on the photo of the operator using the keyboard.  The latch is left of the HMI display.
 

Walk-in Controls Locker     

Interior of Controls Locker ( PLC is at top left)
 
On units without a HMI computer there is the PLC displays its alarms on a first out status display that is located on the operators manual control stand.
   

Operator's Manual Control Stand

First Out and Status Display
 
Notice the operator's control stand has the following items: (On Top top to bottom, left to right) First Out Display, Emergency Stop Button, Joy Stick Throttle Control, Train Air Brakes Apply & Release, Sand, Locomotive Forward - Neutral - Reverse, Horn, (On front side) Rear Coupler Release, Front Coupler Release. Not shown is the operator's foot pedal (dead man switch) which must be continuously depressed when the locomotive is moving and operating in manual control.
   

Operating a track switch while carrying the radio remote control transmitter on his hip.

Operating using the portable remote transmitter from the left side of the cab.
 
In addition to all of the above the process locomotives are also equipped with radio remote control.  The process locomotives can be operated in manual or remote.  Most of the time they are operated in remote because this allows for a smaller crew size; in most cases only one person is required.
There are many input devices located on the locomotive that supply information to the PLC and HMI computers.  For information return to the process locomotives features page.
24VDC v. 64 VDC:
The control power on the process locomotives is 24 VDC.  Most standard locomotives use 32 VDC or 64 VDC systems.  These voltages are not compatible with most other mobile equipment.  Most mobile equipment is either 12 VDC or 24 VDC.  Since the process locomotives use the modern engines that are already 24 VDC compatible and since most of the control hardware is 24 VDC compatible it just makes good sense to install the 24 VDC throughout the locomotive.  Even some of the light bulbs which are nominal 32 VDC work just fine on 24 VDC.  The PLC, the HMI computer, and most other accessories are 24 VDC compatible.  The 24 VDC system only requires two 12 volt batteries in series instead of eight 8 volt batteries in series.  With the smaller engines less amps are required to start them.  This allows down sizing of the entire battery system.  On locomotives with remote start/stop there is included a second set of batteries and an on board battery charger that is automatically engaged when the locomotive is parked and plugged into the overnight heater power.  That power is 240/1/60 VAC on a 40 amp circuit.  The PLC and HMI computer can be run when the locomotive is plugged into the overnight heater power because they run on the 24 VDC from the battery and battery charger.  With 24VDC control power the facility also has the additional advantage of being able to use the locomotive to jump off other mobile equipment.
There is nothing wrong with 64 VDC power for standard locomotives.  With the large engines and generators it take more power to start those units.  Because the process locomotive is so much more efficient 64 VDC control power is simply not required.
 

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