Abstract:
A control system for a hybrid vehicle equipped with power takeoff equipment provides a multi-bus, network environment, integrating operation of a vehicle electric traction motor, power takeoff equipment including prospectively hydraulic motion control equipment and a vehicle thermal engine. The control system is readily programmable to allow reconfiguration depending upon the character of the equipment installed. Efficient utilization of the vehicle&#39;s thermal engine and enhanced system robustness is obtained.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Technical Field:  
         [0002]     The invention relates to integrating power takeoff equipment with a motor vehicle control system, and more particularly to extend functionality, simplify system modification, improve robustness and optimize fuel usage in a hybrid diesel/electric vehicle platform.  
         [0003]     2. Description of the Problem:  
         [0004]     The use of a hybrid vehicle chassis to support power takeoff (PTO) equipment, such as aerial towers (colloquially called “cherry pickers”), garbage trucks, liquid fuel delivery trucks and the like, is relatively new. Integration of the control of PTO equipment, particularly in a way which best utilizes the fuel reserve of the vehicle, has been given little attention. Were control of the PTO equipment simply carried over from conventional vehicles there would be no operational optimization of the system and the systems would remain highly inflexible.  
         [0005]     Many contemporary vehicles are now equipped with body computers, local controllers and controller area networks to implement most aspects of vehicle control. In vehicles designed, built and sold by International Truck and Engine Corporation, an Electrical System Controller (“ESC”) carries out the functions of the body computer. Local controllers which communicate with each other and with the ESC to distribute data and requests essential for operation of local programming by which control is implemented.  
         [0006]     In a conventional vehicle only the vehicle&#39;s engine is usually capable of meeting the power demands required by PTO equipment. This engine, typically a diesel capable of moving a truck at highway speeds, is designed to provide far more power than is required by the PTO equipment and accordingly is not operated in an optimal manner when the vehicle is supporting PTO operation. The problem is magnified in the environment of an aerial tower vehicle where the vehicle is not moving during PTO operation and PTO operation itself may only be occasional as demanded by an operator. If the engine is kept running much fuel is wasted with the engine idling while waiting for operator inputs and in parasitic losses. In certain types of hybrid configurations the traction motor used for starting the vehicle from a standing start may be available for supporting PTO. Electrical motors suffer far less from parasitic losses than do thermal engines and demand relatively little power input in excess of their output. However, it is not a simple matter of just applying the traction motor to supporting PTO operation. Any operational scheme must take into battery charge status and be able to sustain PTO operation from the thermal engine if required.  
         [0007]     Prior art vehicles equipped for PTO operations have typically included an array of relays and extensive hardwiring to support the equipment. This has made the vehicles difficult to modify and subject to hardware failure. Further complicating merged control of the systems is that major subsystems of such a vehicle, particularly a hybrid vehicle come from different manufacturers. For example, in the aerial tower, hybrid vehicle considered in the present application Eaton Corp. supplies the traction motor, transmission, transmission controller, hybrid controller, lithium-ion battery, gear selection controller and inverter; International Truck and Engine supplies the body computer, engine and integrates the components into a vehicle, the chassis mounted PTO equipment may come from a number of sources although the preferred source for an aerial tower is Altec Industries which supplies electromagnetic controlled hydraulic valves, proximity switches, toggle switches, electric motors, relays, solenoids and lights.  
         [0008]     The Eaton sub-system consists of modular sub-components installed on the International chassis. Unless coupled, these the subcomponents along with much of the International chassis&#39; system have no clue as to what is going on with the chassis mounted PTO equipment. It is however, absolutely imperative that these systems do know, because it is their job to provide hydraulic and electrical potential to the chassis mounted PTO equipment via the transmission mounted PTO and supporting chassis electrical architecture at the appropriate times and for the appropriate intervals to support precise equipment functionality. Conversely, these systems need to communicate with the chassis mounted PTO equipment for the same reasons previously assigned. The problem created by this communication gap is two fold. The first problem is that the chassis mounted PTO equipment has no way to communicate with the rest of the controllers on the datalink architecture. The second problem is that were the chassis mounted PTO equipment to have a means of communication, what messages would be passed and how would they be formatted? In addition, what systems on the vehicle data bus would listen to on the datalink as it relates to the other control modules and their associated components? 
       SUMMARY OF THE INVENTION  
       [0009]     According to the invention there is provided a hybrid diesel-electric vehicle equipped with power takeoff operation accessories. The hybrid diesel-electric vehicle includes a conventional public data bus with its body computer, and at least two, but preferably at least three secondary data buses. One secondary data bus interlinks a transmission controller with a hybrid system controller and transmission gear selection controller and provides a gateway to the public data bus. Another secondary controller links a generic programmable module used for PTO accessory control with the body computer, which in turn provides a gateway to the public data bus. Still another secondary data bus is connected between a switch pack and the body computer, which again provides a gateway to the public data bus.  
         [0010]     Control of the power takeoff operation accessories are integrated into one or more remote power modules (RPMs). The RPMs are extensions of a body computer/electrical system controller (ESC) through a controller area network (here a proprietary J1939 datalink interface). The ESC then carries out control of and communication for power takeoff operation accessories. In this way integration with the rest of the controllers over a public portion of the datalink architecture is effected.  
         [0011]     The integration of these varied components over a datalink architecture including their precision functionality is achieved through software preferably implemented using International Truck and Engine&#39;s Diamond Logic™ Builder (DLB) software configuration tool. The integration and control strategy takes into account the base hybrid system, transmission, auto clutch, engine, anti-block braking system (ABS) and PTO accessory functionality allowing them to work in a symbiotic relationship in according to a particular set of flexible and ever changing requirements. The claim in its broadest sense has to do with an approach/strategy of integrating a hybrid drive system to TEM chassis mounted equipment through a datalink system resident on a commercial or other wise custom truck chassis through flexible software rather than a specific set of functional requirements.  
         [0012]     Control arrangements are finalized by programming, which may be specific to a particular vehicle and alterable with time, the vehicle gains flexibility and system robustness is enhanced. In addition, energization of the PTO accessory may be effected in a way which minimizes fuel usage. The hybrid vehicle traction motor is employed, under normal circumstances, to supply power for PTO operation. Typically stored electrical power is used. This electrical power typically represents power stored from regenerative braking. However, it may also represent power stored at any time when the diesel is operated at levels where its power output exceeds immediate demands for power from the engine. In response to indication of a low state of charge of the battery, the engine may be operated to support PTO operation, but when doing so it is operated at its optimal output with the excess power produced being diverted to generate electricity for storage. Thus the engine is operated only briefly and at its optimal power level, minimizing the effect of parasitic losses.  
         [0013]     Additional effects, features and advantages will be apparent in the written description that follows. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself however, as well as a preferred mode of use, further objects and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein:  
         [0015]      FIG. 1  is a simplified illustration of a truck mounted aerial lift assembly for locating an operator in various raised positions.  
         [0016]      FIG. 2  is a high level schematic of a vehicle control system for a hybrid vehicle equipped with a PTO application.  
         [0017]      FIGS. 3A-3G  are state diagrams of the vehicle drive train.  
         [0018]      FIG. 4  illustrates the location and character of translation routines used by controllers for inter bus/data link communication.  
         [0019]      FIG. 5  is a high level flow chart illustrating operation of a preferred embodiment of the invention.  
         [0020]      FIG. 6  is a high level flow chart illustrating operation of a preferred embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     Referring now to the figures and in particular to  FIG. 1 , an example of a mobile aerial lift truck  1  is illustrated. The mobile aerial lift truck  1  includes an aerial lift unit  2  mounted to a bed on the back portion of the truck. The aerial lift unit  2  includes a lower boom  3  and an upper boom  4  pivotally interconnected to each other. The lower boom  3  is in turn mounted to rotate on the truck bed on a support  6  and rotatable support bracket  7 . The rotatable support bracket  7  includes a pivoting mount  8  for one end of lower boom  3 . A bucket  5  is secured to the free end of upper boom  4  and supports personnel during lifting of the bucket to and support of the bucket within a work area. Bucket  5  is pivotally attached to the free end of boom  4  to maintain a horizontal orientation at all times. A lifting unit  9  is interconnected between bracket  7  and the lower boom  3 . A pivot connection  10  connects the lower boom cylinder  11  of unit  9  to the bracket  7 . A cylinder rod  12  extends from the cylinder  11  and is pivotally connected to the boom  3  through a pivot  13 . Lower boom cylinder unit  9  is connected to a pressurized supply of a suitable hydraulic fluid, which allows the assembly to be lifted and lowered. As discussed below, the primary source of pressurized hydraulic fluid is preferably an automatic transmission.  
         [0022]     The outer end of the lower boom  3  is interconnected to the lower and pivot end of the upper boom  4 . A pivot  16  interconnects the outer end of the lower boom  3  to the pivot end of the upper boom  4 . An upper boom compensating cylinder unit or assembly  17  is connected between the lower boom  3  and the upper boom  4  for moving the upper boom about pivot  16  to position the upper boom relative to the lower boom  3 . The upper boom compensating cylinder unit  17  is constructed to permit independent movement of the upper boom  4  relative to lower boom  3  and to provide compensating motion between the booms to raise the upper boom with the lower boom. Unit  17  is supplied with pressurized hydraulic fluid from the same sources as unit  9 .  
         [0023]     Referring to  FIG. 2 , a high level schematic of a control system  21  which provides vehicle  1  control and fuel usage management is illustrated. An electrical system controller  24 , a type of a body computer, is linked by a public datalink  18  to a variety of local controllers which in turn implement direct control over most vehicle  1  functions. Electrical system controller (ESC)  24  may also be directly connected to selected inputs and outputs. As illustrated, an ignition switch input, a brake pedal position input and a park brake position sensor are connected to supply signals to the ESC  24 . In some embodiments, a fuel level sensor input and a throttle position input may also supply signals to the ESC  24 . Signals for PTO operational control from within a cab may be implemented using an In-cab switch pack(s)  56 . In-cab switch pack  56  is connected to ESC  24  over a proprietary data link  64  conforming to the SAE J1708 standard. Data link  64  is a low baud rate data connection, typically on the order of 9.7 Kbaud. Four major local controllers in addition to the ESC  24  are illustrated connected to the public datalink  18 . These controllers are the engine controller  46 , the transmission controller  42 , a gauge controller  58  and an antiblock brake system controller (ABS)  50 . Datalink  18  is preferably the bus for a public controller area network (CAN) conforming to the SAE J1939 standard and under current practice supports data transmission at up to 250 Kbaud. It will be understood that other controllers may be installed on the vehicle  1  in communication with datalink  18 . ABS controller  50 , as is conventional, controls application of brakes  52  and receives wheel speed sensor signals from sensors  54 . Wheel speed is reported over datalink  18  and is monitored by transmission controller  42 .  
         [0024]     Vehicle  1  is preferably a hybrid diesel electric vehicle which utilizes a drive train  20  in which the traction motor/generator  32  is connected in line with an engine  28 . As with other hybrid designs, the system is intended to recapture the vehicle&#39;s inertial momentum to supplement engine output. Drive train  20  is a particular variation of hybrid design which affords advantages in a utility application. It is further intended for operation of the engine  28  to support PTO operation both directly, and by use to generate electrical power for storage. In this way the engine  28  is run at its optimal power output level when used in direct support of PTO operation (and possibly any other time when the engine might otherwise be called on to run). A traction motor/generator  32  is used to recapture vehicle kinetic energy during deceleration by using the drive wheels  26  to drive the traction motor/generator  32 . Engine  28  may be utilized to supply power to generate electricity, to both generate electricity and operate PTO system  22 , to provide motive power to drive wheels  26 , or to provide motive power and to run a generator to generate electricity. Where the PTO system  22  is an aerial lift unit  2  it is unlikely that it would be operated when the vehicle was in motion, and the description here assumes that in fact that the vehicle will be required to be stopped, but other PTO applications may exist where such would occur. Under such circumstances, with sufficient engine capacity, it is conceivable that electrical power generation, motive power generation and PTO operation could be concurrent.  
         [0025]     Drive train  20  provides for the recapture of kinetic energy in response to the traction motor/generator  32  being back driven by the vehicle&#39;s kinetic force. These transitions between positive and negative traction motor contribution are detected and managed by a hybrid controller  48 . Traction motor/generator  32 , during braking, generates electricity which is applied to a storage battery  34  through inverter  36 . Hybrid controller  48  looks at the ABS controller  50  datalink traffic to determine if regenerative kinetic braking would increase or enhance a wheel slippage condition if regenerative braking were initiated. Transmission controller  42  detects such traffic on datalink  18  and translates this as control signals for application to hybrid controller  48  over datalink  68 . Traction motor/generator  32 , during braking, generates electricity which is applied to a Lithium-ion storage battery  34  through hybrid inverter  36 . Some electrical power may be diverted from hybrid inverter to maintain the charge of a conventional 12-volt DC Chassis battery  60  through a DC/DC inverter  62 .  
         [0026]     Battery  34  is a lithium-ion battery and is preferably the only electrical power storage system for vehicle  1 . Lithium ion batteries are used in 42 volt DC power systems. In vehicles contemporary to the writing of this application numerous 12 volt applications remain in common use and vehicle  1  may be equipped with a parallel 12 volt system to support these systems. This possible parallel system is not shown for the sake of simplicity of illustration 12 volt DC motor vehicle power systems based on an engine driven alternator and 12 volt, 6 cell lead acid batteries have been in use for decades and are well known to those skilled in the art. Inclusion of such a parallel system would allow the use of readily available and inexpensive components designed for motor vehicle use, such as incandescent bulbs for illumination. Otherwise the weight penalty and extra complexity introduced by 12 volt components is considered undesirable.  
         [0027]     Traction motor/generator  32  may be used to propel vehicle  1  by drawing power from battery  34  through inverter  36 , which supplies 3 phase 340 volt rms power. Battery  34  is sometimes referred to as the traction battery to distinguish it from a secondary 12 volt lead acid battery  60  used to supply power to various vehicle systems. High mass vehicles tend to exhibit far poorer gains from hybrid locomotion than do conventional vehicles. The preferred use of stored electrical power is thus is power PTO system  22 . In addition, traction motor/generator  32  is used for starting engine  28  when the ignition is in the start position. Under some circumstances engine  28  is used to drive the traction motor/generator  32  with the transmission  38  in a neutral state to generate electricity for recharging battery  34  and/or engaged to the PTO system  22  to generate electricity for recharging the battery  34  and operate the PTO system  22 . This would occur in response to heavy PTO system  22  use which draws down the charge on battery  34 . Typically engine  28  has a far greater output capacity than is required for operating PTO system  22 . As a result using it to directly run PTO system  22  full time would be highly inefficient due to parasitic losses incurred in the engine. Greater efficiency is obtained by running engine  22  at close to its rated output to recharge battery  34  and then shutting down the engine and using battery  34  to supply electricity to traction motor/generator  32  to operate PTO system  22 . An aerial lift unit  2  is often used only sporadically by a worker for reposition of basket  5  and wasteful idling of engine  22  is thus avoided. Engine  22  runs periodically at an efficient speed to recharge the battery only if required by the battery  34  state of charge. Battery  34  state of charge is determined by the hybrid controller  48 , which passes this information to transmission controller  42  over datalink  68 . Transmission controller  42  can in turn can request ESC  24  to engage engine  28  by a message to the ESC  24 , which in turn sends power request signals, (and start and stop signals) to engine controller  46 . The availability of engine  28  may depend on certain programmed (or hardwired) interlocks, such as hood position.  
         [0028]     Drive train  20  comprises an engine  28  connected in line with an auto clutch  30  which allows disconnection of the engine  28  from the rest of the drive train when the engine is not required for motive power or for recharging battery  34 . Auto clutch is directly coupled to the traction motor/generator  32  which is in turn connected to a transmission  38 . Transmission  38  is in turn used to apply power from the traction motor/generator  32  to either the PTO system  22  or to drive wheels  26 . Transmission  38  is bi-directional and can be used to transmit energy from the drive wheels  26  back to the traction motor/generator  32 . Traction motor/generator  32  may be used to provide motive energy (either alone or in cooperation with the engine  28 ) to transmission  38 . When used as a generator the traction motor/generator supplies electricity to inverter  36  which supplies direct current for recharging battery  34 .  
         [0029]     A control system  21  implements cooperation of the control elements to effect the operations just described. ESC  24  receives inputs relating to throttle position, brake pedal position, ignition state and PTO inputs from a user and passes these to the transmission controller  42  which in turn passes them to the hybrid controller  48 . Hybrid controller  48  determines, based on available battery charge state, requests for power. Hybrid controller  48  with ESC  24  generates the appropriate signals for application to datalink  18  for instructing the engine controller  46  to turn engine  28  on and off and, if on, at what power output to operate the engine. Transmission controller  42  controls engagement of auto clutch  30 . Transmission controller  42  further controls the state of transmission  38  in response to transmission push button controller  72 , determining the gear the transmission is in or if the transmission is to deliver drive torque to the drive wheels  26  or to a hydraulic pump which is part of PTO system  22  (or simply pressurized hydraulic fluid to PTO system  22  where transmission  38  serves as the hydraulic pump) or if the transmission is to be in neutral.  
         [0030]     PTO control is implemented through one or more remote power modules (RPMs). Remote power modules are datalinked expansion input/output modules dedicated to the ESC, which is programmed to utilize them. RPMs  40  function as the PTO controller, and provide hardwire outputs  70  and hardwire inputs  66  required by the PTO device  22  and to and from the aerial lift unit  2 . Requests for movement from the aerial lift unit  2  and position reports are applied to the proprietary datalink  74  for transmission to the ESC  24 , which translates them into specific requests for the other controllers, e.g. a request for PTO power. ESC  24  is also programmed to control valve states through RPMs  40  in PTO device  22 . Remote power modules are more fully described in U.S. Pat. No. 6,272,402 which is assigned to the assignee of the present invention and is fully incorporated herein by reference. At the time the ‘402 patent was written what are now termed “Remote Power Modules” were called “Remote Interface Modules”.  
         [0031]     Transmission controller and ESC  24  both operate as portals and/or translation devices between the various datalinks. Proprietary datalinks  68  and  74  operate at substantially higher baud rates than does the public datalink  18 , and accordingly, buffering is provided for a message passed from one link to another. Additionally, a message may have to be reformatted, or a message on one link may require another type of message on the second link, e.g. a movement request over datalink  74  may translate to a request for transmission engagement from ESC  24  to transmission controller  42 . Datalinks  18 ,  68  and  74  are all controller area networks and conform to the SAE J1939 protocol. Datalink  64  conforms to the SAE J1708 protocol.  
         [0032]      FIG. 4  illustrates that both ESC  24  and transmission controller  42  provide massage translation tables  224 ,  242 , interpretive logic  124 ,  142  and message buffering  324 ,  342  for communication occurring on one datalink requiring a response by a controller coupled only to another datalink. The transmission controller  42  and ESC  24  thus provide inter-operation between four data buses. Datalink  68  is part of a hybrid transmission controller system produced by Eaton Corporation and does not form part of the invention. In effect, ESC  24  and transmission controller  42  can act as gateways, passing messages from one channel to another or, depending upon the message, may carry out operations based on the message and issue responsive messages to any or all of the datalinks to which the particular controller is connected.  
         [0033]     FIGS.  3 A-G are a series of state diagrams illustrating the combinational modes of engine, clutch, motor/generator, battery and transmission, to effect implementation of the invention. As noted above, high mass motor vehicles benefit less from use of storage of regenerative power from braking than do low mass passenger cars. However, where such vehicles are used as mobile platforms to deliver, and power, equipment used at work sites, regenerative power is advantageously applied to powering PTO equipment due to the mismatch of the vehicle&#39;s engine to the application. The particular programming on any given vehicle may be unique to that vehicle.  
         [0034]      FIG. 3A  illustrates direct hybrid electric mode of vehicle  1  where battery  34  is the sole source of power to PTO system  22 . Engine  28  is in an off mode  100 . Autoclutch  30  is disengaged  102  so no torque is transmitted between traction motor/generator  32  and engine  28 . Instead traction motor/generator  32  draws power from battery  34  (discharge mode  108 ) and operates as a motor  104  supplying motor torque as demanded to the transmission  38 . Transmission  38  is in gear  106  to supply drive torque to either the drive wheels  26  or to a PTO system  22 .  
         [0035]      FIG. 3B  illustrates an engine/battery operational mode of vehicle  1  where both the battery  34  and the engine  28  supply power to generate drive torque for use by PTO system  22 , more likely, or to propel vehicle  1 . Engine  28  is running  120 , supplying engine torque to autoclutch  30  which in turn is engaged  122 . Autoclutch  30  supplies torque to traction motor/generator  32  which is operating as a motor  124 , drawing power from battery  34  and supplementing the torque generated by the engine. The combined torque of the motor  124  and running engine  120  is applied to an in gear transmission  126  which in turn supplies drive torque to the drive wheels  26 . This operational mode would be expected under circumstances of hard acceleration or other circumstances where vehicle  1  was being used under conditions demanding high torque for operation. The total power output would typically greatly exceed any possible demand from PTO system  22 .  
         [0036]      FIG. 3C  illustrates an engine/battery operational mode of vehicle  1  where the engine  28  supplies power both to generate drive torque for use by PTO system  22 , or to propel the vehicle, and to generate electrical power to recharge  148  the battery  34 . Engine  28  is running  140 , supplying engine torque to autoclutch  30  which in turn is engaged  142 . Autoclutch  30  supplies torque to traction motor/generator  32  which is operates as a generator  144  to supply recharging current to battery  34  (battery recharge mode  148 ). The combined torque of the running engine  140  less the load imposed by generator  144  is applied to an in gear transmission  146  which in turn supplies drive torque to the drive wheels  26  or to PTO system  22 . This operational mode would be expected when a low state of charge of battery  34  has been indicated and vehicle fuel reserves are sufficient to allow continued PTO operation. Fuel reserves could be low enough to trigger discontinuing recharging and inhibit PTO operation, other than stowing the PTO system.  
         [0037]      FIG. 3D  illustrates an engine/battery operational mode of vehicle  1  where the engine  28  is operating as an engine brake  160  and the vehicle&#39;s inertia supplies drive torque used to regenerate electrical power for storage in battery  34 . Engine braking  160  may be used in response to an indication that battery  34  is close to a full charge, or because the braking demand indicated by the brake position sensed by the ESC  24  indicates that braking demand exceeds the capacity of the battery  34  to accept power. Inertial torque is applied to an in gear transmission  166  which applies regenerative torque to traction motor/generator  32  operating in generator mode  164 . Electrical power is returned to battery  34  in recharge mode  168 . Residual torque is passed by engaged clutch  162  to engine  28  operating as an engine brake  160 .  
         [0038]      FIG. 3E  illustrates a pure regenerative braking mode of vehicle  1  where the vehicle&#39;s inertia supplies drive torque used to regenerate electrical power for storage in battery  34 . Engine  28  is off  180  and autoclutch  30  is disengaged  182 . Responsive to detection of depression of a brake pedal or to indication from a speed control system of excessive speed, inertial torque is applied to an in gear transmission  186  which applies regenerative torque to traction motor/generator  32  operating in generator mode  184 . Electrical power is returned to battery  34  in recharge mode  188 . It would be theoretically possible to recover energy from PTO system  22 , such as in the circumstance of recovering energy from an elevated aerial lift unit  2 . However, the amount of energy available for recovery is regarded as too slight in an aerial lift unit  2  to justify the complication in control that this would involve. Control would have to accommodate both the recovery of the potential energy represented by the elevated lift unit and the diversion of energy that would required to control the aerial lift unit  2  for stowage or repositioning.  
         [0039]      FIG. 3F  illustrates an engine starting mode. This could occur on start up of vehicle  1 , or in response to indication of a low state of battery charge during PTO operation. Engine  28  is cranking  200  with autoclutch  30  disengaged  202  to deliver cranking torque to the engine from motor  204 . The transmission  38  is moved to neutral  206 , temporarily interrupting delivery of power to PTO system  22  if the PTO system is engaged. Where PTO system  22  is engaged, appropriate delays, or safety steps, may be programmed in to prevent inconvenient interruption of PTO system  22  operation before the engine cranks  200 . Warning is typically provided the operator and, if necessary, interlocks may be engaged to prevent undesired movement of an aerial tower, or unexpected interruption of PTO operation. The particular conditions involved depend upon the specific application, but generally would be the same as the interlocks used in present applications.  
         [0040]      FIG. 3G  illustrates battery recharging  228 , typically as would occur during an interruption of PTO operation and following engine cranking. This operational state is an alternative to the mode described in connection to that describe with  FIG. 3C  and maintains interruption of PTO operation while the battery is recharged, preferably while with the engine running  220  at its most efficient loading. Torque is applied from a running engine  220  to an engaged auto clutch  222  and through the clutch to the traction motor/generator  32  operating as a generator  224 . Electrical power is used for battery recharging  228 . No drive torque is produced by a transmission which is in neutral  226 .  
         [0041]      FIGS. 5 and 6  provide a high level overview of operation of control system  20  for aerial tower equipped vehicle  1 , provided as an example of application of the invention to a specific environment. Although control is illustrated in flow chart form, those skilled in the art will appreciate that the operational steps are distributed over several controllers and the flow charts do not directly represent a single program executing on a single device, but rather operational steps achieved by cooperation of several logical processors. For aerial tower  2  operation it is preferred that the vehicle  1  be stationary, although for some types of vehicles and PTO applications, this would not be necessary. The first steps thus are directed toward determining if the vehicle  1  is stationary. The ABS controller  50  reports wheel speeds over the public datalink  18 , which is read by the transmission controller  42  as indicated at step  500 . The transmission controller  42 , monitoring transmission push button controller  72  and the drive shaft of transmission  38 , determines if neutral has been selected and if the drive shaft has zero output. The transmission controller  42  reports that the transmission  38  is in neutral after vehicle wheel speed is zero, drive shaft output is zero and the selected gear is neutral at step  502 . At step  504  the ESC  24  reads that the transmission is in neutral and determines is the park brake has been set. If YES, the ESC  24  reports that the vehicle  1  is in its stationary mode, allowing for request of use of the aerial unit  2 . If the result of any of steps  500 ,  502 , or  504  is NO, then the program returns to step  500  for continued monitoring. In other words the ESC  24  is seeing via the public datalink  18  that the Eaton transmission controller  42  is transmitting a “neutral” current gear state, as well as a vehicle speed is “zero” mph. The ESC  24  also sees that the parking brake is set “On” via a hard wire input coming from the chassis&#39; wiring.  
         [0042]     It will be understood that other requirements for PTO operation may be added here, for example, it may be required that the ESC  24  report that the hood be closed over the public datalink  18 , as determined from a hard wire connection into ESC  24 . Given the high voltages at which the hybrid traction system operates this could be required as a safety measure. While PTO operation contemplates operation of traction motor/generator  32 , hybrid controller  48  may, on account of battery status, indicate a demand for engine  28  operation, which would be communicated back via transmission controller  42  to ESC  24 , which in turn would signal to the engine controller  46  that engine  28  was to be engaged. (It is important that there be a hood closed signal such that the auto clutch and traction motor would not initiate an unexpected engine crank/start with the hood open and someone under the hood and working, should the traction motor/generator batteries state of charge fall below 28% state of charge, initiating a recharge cycle of the 340 volt traction batteries. The ESC does not read or control the traction batteries state of charge. The ESC just tells the Eaton hybrid system not to close the clutch or start the traction motor/generator due to a low state of battery charge.  
         [0043]     Once the vehicle  1  is in stationary mode PTO operation for an aerial unit  2  is allowed. As has been stated above, having a stationary vehicle may not be required in other applications. At step  508  an in-cab request for PTO operation (entered typically using switch pack  56  and applied to the ESC  24  over datalink  64 ) is awaited. As long as the request is not received execution cycles back along the NO branch to step  500 . Once a PTO request has been made operational execution advances to step  510 . If conditions for PTO operation are not met than indication may be supplied the operator of that fact. At step  510  ESC  24  reports the PTO request on public datalink  18 , from which it is read by transmission controller  42 . The transmission controller  42  will so advise hybrid controller  48  over datalink  68  (step  512 ). At step  514  the transmission controller  42  will report power availability for PTO operation over public datalink  18 . At step  516  ESC  24  is indicated as energizing the PTO device  22  and RPM  40 . In particular, the ESC  24  response to the public datalink indication by commanding one of the RPM&#39;s 12 volt outputs, set to a maximum of  20  amps, turn to “On”. In this way a “master power” source is provided to PTO device  22  so long as all the conditions described above maintain unchanged.  
         [0044]     Referring now to  FIG. 6 , PTO accessory operation is described. For as long as “Machine Enable” conditions are maintained as determined by the operations described in connection with  FIG. 5  and reflected by step  602 , and master power is present for the PTO device  22 , a fiber optic transceiver system will be energized as indicated by step  604 . With the depression (indicated as a decision step  604 ) of an aerial tower joy stick control lever&#39;s trigger (not shown) mounted at the upper controls of the aerial tower  2 , a fiber optic signal shall be transmitted down through the aerial tower&#39;s upper and lower insulated boom sections  3 , 4 , where upon it will be converted by a hardwire input  66  into a discrete 12 volt signal and sent into one of the RPM  40  inputs. At step  608  receipt by ESC  24  of indication of a 12 volt signal on one of the RPM&#39;s  40  inputs via the proprietary datalink  64  is indicated.  
         [0045]     Responsive to joy stick movement ESC  24  generates a public datalink  18  signal commanding the hybrid controller  48  (through transmission controller  42 ) to activate the traction motor/generator  32 . The character of that response is subject to some nuances directed to avoiding hydraulic shock and to determining when the operator has ceases requesting movement. Broadly stated, ESC  24  will continue to transmit the public datalink  18  signal for the traction motor/generator&#39;s  32  activation so long as it sees the aerial tower joy stick&#39;s 12 volt request at the appropriate RPM  40  input. However, once this signal stops coming into the RPM  40  input, the absence of the signal is translated in the ESC&#39;s  24  software as the operator&#39;s releasing the joy stick&#39;s trigger. ESC  24  will continue to send the public datalink  18  signal to the hybrid controller  48  to maintain the traction motor/generator&#39;s  32  operation for an adjustable time interval. The reason why the ESC  24  maintains this signal is to prevent rapid re-activations of the traction motor/generator  32  by the operator creating transient shock/pressure waves within the aerial tower&#39;s hydraulic system. Such transients can cause subtle to extreme fluctuations with in the aerial tower&#39;s normally smooth operation.  
         [0046]     For these reasons, simultaneously as the traction motor/generator  32  drives the PTO/hydraulic pump of the PTO device  22 , the ESC  24  monitors a hydraulic pressure transducer (not shown) which is installed in the return side of the aerial tower&#39;s  2  hydraulic system. ESC  24  software performs a complex running filter function that will compensate for viscosity variation due to thermal and ambient temperature changes (also monitored by sensors which are not illustrated for the sake of simplicity). It is this complex function that ultimately decides that the operator is no longer requesting, or making any hydraulic system demands. Under these conditions the ESC stops sending the public datalink message to the Eaton hybrid controller requesting the activation of the traction motor/generator&#39;s operation. As a result the traction motor/generator stops turning the PTO and awaits the ESC&#39;s next command. These steps are reflected in the flow chart where at step  614  the ESC is indicated as obtaining operating data. At step  616  the ESC  24  is indicated as initiating the filter function. At step  618 , reflecting both presence of the joy stick movement signal and in consideration of the results of the filtering function, an operator request is confirmed or not (the NO branch). If confirmed (the YES branch) execution of a step  620  is indicated which is a request to the transmission controller  42  (and implicitly the hybrid controller  48 ) for energization of the traction motor/generator  32 . Step  622  reflects continued monitoring of the status of the filtering function and joy stick position signal to determine if aerial tower unit  2  movement is still being requested. If not, step  624  is executed to cancel the request for traction motor  32  operation. Processing is returned to step  602  along the YES branch from step  622  or after step  624  as an indication that PTO enablement must be maintained. It will be understood that if PTO enablement is not maintained that the traction motor energization request is cancelled.  
         [0047]     The invention allows the advantageous application of hybrid technology to relatively high mass vehicles, saving fuel, and allowing thermal engines, when in use, to be run at power levels minimizing the production of pollutants or optimizing fuel usage.  
         [0048]     While the invention is shown in only one of its forms, it is not thus limited but is susceptible to various changes and modifications without departing from the spirit and scope of the invention.