Patent Publication Number: US-8972084-B2

Title: Control system for equipment on a vehicle with a hybrid-electric powertrain

Description:
RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Patent Application No. 61/113,702 filed on Nov. 12, 2008, which is herein incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a hydraulic load control system for power take off (“PTO”) equipment on a vehicle with a hybrid-electric powertrain, and more particularly to a system and method for transitioning between internal combustion engine powered operation of the PTO and hybrid-electric powertrain powered operation of the PTO that supplies power for the hydraulic load. 
     BACKGROUND 
     Many vehicles now utilize hybrid-electric powertrains in order to increase the efficiency of the vehicle. A hybrid-electric powertrain typically involves an internal combustion engine that operates a generator that produces electrical power that may be used to drive electric motors used to move the vehicle. The electric motors may be used to provide power to wheels of the vehicle to move the vehicle, or the electric motors may be used to supplement power provided to the wheels by the internal combustion engine and a transmission. In certain operational situations, the electric motors may supply all of the power to the wheels, such as under low speed operations. In addition to providing power to move the vehicle, the hybrid-electric powertrain may be used to power a PTO of the vehicle, sometimes also referred to as an electric PTO or EPTO when powered by a hybrid-electric powertrain, that in turn powers PTO driven accessories. 
     In some vehicles, such as utility trucks, for example, a PTO may be used to drive a hydraulic pump for an on-board vehicle hydraulic system. In some configurations, a PTO driven accessory may be powered while the vehicle is moving. In other configurations, a PTO driven accessory may be powered while the vehicle is stationary and the vehicle is being powered by the internal combustion engine. Still others may be driven while the vehicle is either stationary or traveling. Control arrangements are provided for the operator for any type of PTO configuration. 
     In some PTO applications the vehicle&#39;s particular internal combustion engine may be of a capacity that makes it inefficient as a source of motive power for the PTO application due to the relatively low power demands, or intermittent operation, of the PTO application. Under such circumstances the hybrid-electric powertrain may power the PTO, that is, use of the electric motor and generator instead of the IC engine to support mechanical PTO, may be employed. Where power demands are low, the electric motor and generator will typically exhibit relatively low parasitic losses compared to an internal combustion engine. Where power demand is intermittent, but a quick response is provided, the electric motor and generator provides such availability without incurring the idling losses of an internal combustion engine. 
     Conventionally, once a hybrid electric vehicle equipped for EPTO enters the EPTO operational mode, the electric motor and generator remains unpowered until an active input or power demand signal is provided. Typically, the power demand signal results from an operator input received through a body mounted switch which is part of data link module. Such a module could be the remote power module described in U.S. Pat. No. 6,272,402 to Kelwaski, the entire disclosure of which is incorporated herein by this reference. The switch passes the power demand signal over a data bus such as a Controller Area Network (CAN) now commonly used to integrate vehicle control functions. 
     A power demand signal for operation of the traction motor is only one of the possible inputs that could occur and which could be received by a traction motor controller connected to the controller area network of the vehicle. Due to the type, number and complexities of the possible inputs that can be supplied from a data link module added by a truck equipment manufacturer (TEM), as well as from other sources, issues may arise regarding adequate control of the electric motor and generator, particularly during the initial phases of a product&#39;s introduction, or during field maintenance, especially if the vehicle has been subject to operator modification or has been damaged. As a result the traction motor may not operate as expected. In introducing a product, a TEM can find itself in a situation where the data link module cannot provide accurate power demand requests for electric motor and generator operation for EPTO operation due to programming problems, interaction with other vehicle programming, or other architectural problems. 
     A hybrid-electric powertrain may solely power the PTO of the vehicle when the PTO is operating a PTO driven accessory adapted to only be utilized by a stopped vehicle, such as lift attachment, or a digging attachment. In some situations, the hybrid-electric powertrain is not capable of providing sufficient power to the PTO, and thus, the PTO needs to be powered by the internal combustion engine. In other situations, batteries of the hybrid-electric powertrain may need to be recharged. In both of these situations, if the PTO is being powered by the hybrid-electric powertrain, the PTO must be stopped, such that the internal combustion engine may be started to deliver power to the PTO, or to recharge batteries of the hybrid-electric powertrain. Therefore, a need exists for a system and method that is capable of shutting down a PTO that is being driven by a hybrid-electric powertrain, such that an internal combustion engine may be started to power the PTO, or to recharge batteries of the hybrid-electric powertrain. 
     SUMMARY 
     According to one embodiment, a vehicle having a hydraulic hybrid powertrain comprises a power take off unit, a hydraulic pump, a hydraulic accumulator, an accumulator isolation valve, an accumulator solenoid, and a vehicle hydraulic component. The hydraulic pump mechanically connects to the power take off unit and is driven by the power take off unit. The hydraulic accumulator is disposed in fluid communication with the hydraulic pump and receives and stores pressurized hydraulic fluid from the hydraulic pump. The accumulator isolation valve has a first position and second position. The accumulator isolation valve is disposed in fluid communication with the hydraulic accumulator. The accumulator solenoid connects to the accumulator isolation valve and positions the accumulator isolation valve to the first position and the second position. The vehicle hydraulic component is disposed in fluid communication with the accumulator isolation valve and the hydraulic accumulator. 
     According to another embodiment, a control system for a vehicle having a hybrid-electric powertrain comprises an electronic control module, an electronic system controller, a hybrid control module, a remote throttle, and a variable displacement hydraulic pump. The electronic system controller is disposed in electrical communication with the electronic control module. The hybrid control module is disposed in electrical communication with the electronic control module and the electronic system controller. The remote throttle is disposed in electrical communication with the electronic control module. The variable displacement hydraulic pump has a displacement adjustment portion disposed in electrical communication with the electronic system controller. The variable displacement portion has at least a first position and a second position. Wherein the variable displacement portion is moved from the first position to the second position in response to an output signal from the electronic system controller. 
     According to another embodiment, a control system for a vehicle having a hydraulic hybrid powertrain comprises a vehicle hydraulic component signal generation device, a datalink module, an electronic system controller, and an electronic control module. The datalink module is disposed in electrical communication with the vehicle hydraulic component signal generation device. The electronic system controller is disposed in electrical communication with the datalink module. The electronic control module is disposed in electrical communication with the electronic system. 
     According to one process, a method of operating a vehicle having a hydraulic hybrid powertrain is provided. An output signal is generated from a vehicle hydraulic component transducer. The output signal from the vehicle hydraulic component transducer transmits to an electronic system controller. A remote power module energizes in response to the output signal from the vehicle hydraulic component transducer user input switch. An accumulator isolation valve opens in response to energizing the remote power module. Hydraulic fluid is provided from a hydraulic accumulator to a vehicle hydraulic component in response to opening the accumulator isolation valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side elevation of a vehicle equipped for a power take-off operation. 
         FIG. 2  is a high level block diagram of a control system for the vehicle of  FIG. 1 . 
         FIG. 3  is a diagram for a state machine relating to a power take-off operation which can be implemented on the control system of  FIG. 2 . 
         FIGS. 4A-D  are schematic illustrations of a hybrid powertrain applied to support a power take-off operation. 
         FIG. 5  is a system diagram for chassis and body initiated hybrid electric motor and generator control for power take-off operation. 
         FIG. 6  is a map of input and output pin connections for a remote power module in the system diagram of  FIG. 5 . 
         FIG. 7  is a map of input and output locations for the electrical system controller of  FIG. 5 . 
         FIG. 8  is a schematic view of a vehicle having a hybrid-electric powertrain with a PTO driven hydraulic system. 
         FIG. 9  is a system diagram for a control system of the vehicle of  FIG. 8 ; 
         FIG. 10  is a schematic view of a vehicle having a hybrid-electric powertrain with a PTO driven hydraulic system having an accumulator and an accumulator isolation valve. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the figures and in particular to  FIG. 1 , a hybrid mobile aerial lift truck  1  is illustrated. Hybrid mobile aerial lift truck  1  serves as an example of a medium duty vehicle which supports a PTO vocation, or an EPTO vocation. It is to be noted that embodiments described herein, possibly with appropriate modifications, may be used with any suitable vehicle. Additional information regarding hybrid powertrains may be found in U.S. Pat. No. 7,281,595 entitled “System For Integrating Body Equipment With a Vehicle Hybrid Powertrain,” which is assigned to the assignee of the present application and which is fully incorporated herein by reference. 
     The mobile aerial lift truck  1  includes a PTO load, here an aerial lift unit  2  mounted to a bed on a back portion of the truck  1 . During configuration for EPTO operation, the transmission for mobile aerial lift truck  1  may be placed in park, the park brake may be set, outriggers may be deployed to stabilize the vehicle, and indication from an onboard network that vehicle speed is less than 5 kph may be received before the vehicle enters PTO mode. For other types of vehicles different indications may indicate readiness for PTO operation, which may or may not involve stopping the vehicle. 
     The aerial lift unit  2  includes a lower boom  3  and an upper boom  4  pivotally connected 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. A lifting unit  9  is connected 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. A source of pressurized hydraulic fluid may be an automatic transmission or a separate pump. The outer end of the lower boom  3  is connected 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  allows independent movement of the upper boom  4  relative to lower boom  3  and provides 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 source as unit  9 . 
     Referring to  FIG. 2 , a high level schematic of a control system  21  representative of a system usable with vehicle  1  control is illustrated. An electrical system controller  24 , a type of a body computer, is linked by a public datalink  18  (here illustrated as a SAE compliant J1939 CAN bus) 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 and other busses. Direct “chassis inputs” include, an ignition switch input, a brake pedal position input, a hood position input and a park brake position sensor, which are connected to supply signals to the ESC  24 . Other inputs to ESC  24  may exist. 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. Five controllers in addition to the ESC  24  are illustrated connected to the public datalink  18 . These controllers are the engine controller (“ECM”)  46 , the transmission controller  42 , a gauge cluster controller  58 , a hybrid controller  48  and an antilock brake system controller (“ABS”)  50 . Other controllers may exist on a given vehicle. Datalink  18  is 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 . 
     Vehicle  1  is illustrated as a parallel hybrid electric vehicle which utilizes a powertrain  20  in which the output of either an internal combustion engine  28 , an electric motor and generator  32 , or both, may be coupled to the drive wheels  26 . Internal combustion engine  28  may be a diesel engine. As with other full hybrid systems, the system is intended to recapture the vehicle&#39;s inertial momentum during braking or slowing. The electric motor and generator  32  is run as a generator from the wheels, and the generated electricity is stored in batteries during braking or slowing. Later the stored electrical power can be used to run the electric motor and generator  32  instead of or to supplement the internal combustion engine  28  to extend the range of the vehicle&#39;s conventional fuel supply. Powertrain  20  is a particular variation of hybrid design which provides support for PTO either from internal combustion engine  28  or from the electric motor and generator  32 . When the internal combustion engine  28  is used for PTO it can be run at an efficient power output level and used to concurrently support of PTO operation and to run the electric motor and generator  32  in its generator mode to recharge the traction batteries  34 . Usually a PTO application consumes less power than power output at a thermally efficient internal combustion engine  28  throttle setting. 
     The electric motor and generator  32  is used to recapture the vehicle&#39;s kinetic energy during deceleration by using the drive wheels  26  to drive the electric motor and generator  32 . At such times auto-clutch  30  disconnects the engine  28  from the electric motor and generator  32 . Engine  28  may be utilized to supply power 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 stopped for EPTO, but other PTO applications may exist where this is not done. 
     Powertrain  20  provides for the recapture of kinetic energy in response to the electric motor and generator  32  being back driven by the vehicle&#39;s kinetic force. The transitions between positive and negative traction motor contribution are detected and managed by a hybrid controller  48 . Electric motor and generator  32 , during braking, generates electricity which is applied to traction batteries  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 related data traffic on datalink  18  and translates these data as control signals for application to hybrid controller  48  over datalink  68 . Electric motor and generator  32 , during braking, generates electricity which is applied to the traction batteries  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 voltage step down DC/DC inverter  62 . 
     Traction batteries may be the only electrical power storage system for vehicle  1 . 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 the vehicle. This possible parallel system is not shown for the sake of simplicity of illustration. 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. However, using 12 volt components may incur a vehicle weight penalty and involve extra complexity. 
     Electric motor and 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. However, high mass utility vehicles tend to exhibit far poorer gains from hybrid locomotion than do automobiles. Thus stored electrical power is also used to power the EPTO system  22 . In addition, electric motor and 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 electric motor and 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 used 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 or idling losses which would occur if operation were intermittent. Greater efficiency is obtained by running engine  22  at close to its rated output to recharge battery  34  and provide power to the PTO, and then shutting down the engine and using battery  34  to supply electricity to electric motor and generator  32  to operate PTO system  22 . 
     An aerial lift unit  2  is an example of a system which may be used only sporadically by a worker first to raise and later to reposition its basket  5 . Operating the aerial lift unit  2  using the traction motor  32  avoids idling of engine  28 . Engine  28  runs periodically at an efficient speed to recharge the battery if battery  34  is in a state of relative discharge. 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 engine operation requests (i.e. engine start and stop signals) to ECM  46 . The availability of engine  28  may depend on certain programmed (or hardwired) interlocks, such as hood position. 
     Powertrain  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 powertrain when the engine is not being used for motive power or for recharging battery  34 . Auto clutch  30  is directly coupled to the electric motor and generator  32  which in turn is connected to a transmission  38 . Transmission  38  is in turn used to apply power from the electric motor and 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 electric motor and generator  32 . Electric motor and 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 electric motor and generator supplies electricity to inverter  36  which supplies direct current for recharging battery  34 . 
     A control system  21  implements cooperation of the control elements for 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 the signals to the hybrid controller  48 . Hybrid controller  48  determines, based on available battery charge state, whether the internal combustion engine  28  or the traction motor  32  satisfies requests for power. Hybrid controller  48  with ESC  24  generates the appropriate signals for application to datalink  18  for instructing the ECM  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. For purposes of illustration only, a vehicle may come equipped with more than one PTO system, and a secondary pneumatic system using a multi-solenoid valve assembly  85  and pneumatic PTO device  87  is shown under the direct control of ESC  24 . 
     PTO  22  control is conventionally implemented through one or more remote power modules (RPMs). Remote power modules are data-linked expansion input/output modules dedicated to the ESC  24 , which is programmed to utilize them. Where RPMs  40  function as the PTO controller they can be configured to provide hardwire outputs  70  and hardwire inputs used by the PTO device  22  and to and from the load/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 application and which is fully incorporated herein by reference. At the time the &#39;402 patent was written what are now termed “Remote Power Modules” were called “Remote Interface Modules”. It is contemplated that the TEMs who provide the PTO vocation will order or equip a vehicle with RPMs  40  to support the PTO and supply a switch pack  57  for connection to the RPM  40 . TEMs are colloquially known as “body builders” and signals from an RPM  40  provided for body builder supplied vehicle vocations are termed “body power demand signals”. 
     Body power demand signals may be subject to corruption, vehicle damage or architectural conflicts over the vehicle controller area network. Accordingly an alternative mechanism is provided to generate power demand signals for the PTO from the vehicle&#39;s conventional control network. A way of providing for operator initiation of such a power demand signal without use of RPM  40  is to use the vehicle&#39;s conventional controls including controls which give rise to what are termed “chassis inputs”. Power demand signals for PTO operation originating from such alternative mechanisms are termed “chassis power demand signals”. An example of such could be flashing the headlamps twice while applying the parking brake, or some other easy to remember, but seemingly idiosyncratic control usage, so long as the control choice does not involve the PTO dedicated RPM  40 . 
     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 be reformatted, or a message on one link may be changed to 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. 
     Referring to  FIG. 3  a representative state machine  300  is used to illustrate one possible control regime. State machine  300  is entered through either of two EPTO enabled states  300 ,  302 , depending upon whether engine  28  is operating to recharge the traction batteries  34  or not. In the EPTO enabled state the conditions triggering EPTO operation have been met, but the actual PTO vocation is not powered. Depending upon the state of charge of the traction batteries  34 , engine  28  may be operating (state  302 ) or may not be running (state  304 ). In any state where the engine  28  is on the auto clutch  30  is engaged (+). The state of charge which initiates battery charging is less than the state of charge at which charging is discontinued to prevent frequent cycling of the engine  28  on and off. The EPTO enabled states ( 302 ,  304 ) provide that the transmission  38  is disengaged. In state  302  where batteries  34  are being charged, the electric motor and generator  32  is in its generator mode. In state  304  where batteries  34  are considered charged, the state of the electric motor and generator  32  need not be defined and may be left in its prior state. 
     Four EPTO operating states,  306 ,  308 ,  310  and  312  are defined. These states occur in response to either a body power demand or chassis power demand. Within PTO vehicle battery charging continues to function. State  306  provides that the engine  28  be on, the auto clutch  30  be engaged, the electric motor and generator  32  be in its generator mode and the transmission be in gear for PTO. In state  308  the engine  28  is off, the auto clutch  30  is disengaged, the traction motor is in its motor mode and running and the transmission  38  be in gear for PTO. States  306  and  308 , as a class, are exited upon loss of the body power demand signal (which may occur as a result of cancellation of PTO enable) or upon or occurrence of a chassis power demand signal. Changes in state stemming from the battery state of charge can force changes within the class between states  306  and  308 . EPTO operating states  310  and  312  are identical to states  306  and  308 , respectively, except that loss of the body power demand signal does not result in one of states  310 ,  312  being exited. Only loss of the chassis power demand signal results in exit from EPTO operating states  310  or  312 , taken as a class, although transitions within the class (i.e. between  310  and  312 ) can result from the battery state of charge. Upon loss of a chassis power demand signal the exit route from states  310 ,  312 , depends upon whether a body power demand signal is present. If it is the operational state moves from states  310  or  312  to states  306  or  308 , respectively. If it is not, then to states  302  or  304 . If the body power demand signal was lost due to exit from the EPTO enable conditions than states  302  or  304  are exited along the “OFF” routes. For transitions within a class, particularly from an engine  28  off to an engine  28  on state, an intermediary state may be provided where the auto-clutch  30  is engaged to permit the traction motor to crank the engine. 
       FIGS. 4A-D  illustrate graphically what occurs on the vehicle in the various states of the state machine implemented through appropriate programming of the ESC  24 .  FIG. 4A  corresponds to state  304 , one of the EPTO enabled state.  FIG. 4B  corresponds to state  302 , the other EPTO enabled state.  FIG. 4C  corresponds to states  308  and  312 , while  FIG. 4D  corresponds to states  306  and  310 . In  FIG. 4A  the IC engine  28  is off (state  100 ), the auto clutch is disengaged (state  102 ), the electric motor and generator  32  state may be undefined, but is shown as being motor mode ( 104 ). With electric motor and generator  32  in the motor mode the battery is shown in a discharge ready state  108 . The transmission is shown as in gear ( 106 ), though this is elective. In  FIG. 4B  battery charging  128  is occurring as a result of the IC engine running  120 , the auto clutch being engaged  122  with engine torque being applied through the auto clutch to the electric motor and generator  32  operating in its generator mode  124 . The transmission is out of gear  126 . 
       FIG. 4C  corresponds to state machine  300  states  308  and  312  with the engine  28  being off  100 , the auto clutch  30  being disengaged  102 . The battery  34  is discharging  108  to operate the traction motor in its running state  104  to apply torque to the transmission  38  which is in gear  126  to apply drive torque to the PTO.  FIG. 4D  corresponds to state machine  300  states  306  and  310 . The IC engine  28  is running  120  to supply power through an engaged  122  auto clutch to operate the electric motor and generator  32  in it generator mode to supply electrical power to a charging ( 128 ) battery and to supply torque through the transmission to the PTO application. 
       FIGS. 5-7  illustrate a specific control arrangement and network architecture on which the state machine  300  may be implemented. Additional information regarding control systems for hybrid powertrains may be found in U.S. patent application Ser. No. 12/239,885 filed on Sep. 29, 2008 and entitled “Hybrid Electric Vehicle Traction Motor Driven Power take off Control System” which is assigned to the assignee of the present application and which is fully incorporated herein by reference, as well as U.S. patent application Ser. No. 12/508,737 filed on Jul. 24, 2009, which is assigned to the assignee of the present application and which is fully incorporated herein by reference. The arrangement also provides control over a secondary pneumatic power take-off operation  87  to illustrate that conventional PTO may be mixed with EPTO on a vehicle. Electrical system controller  24  controls the secondary pneumatic PTO  87  using a multiple solenoid valve assembly  85 . Available air pressure may dictate control responses and accordingly an air pressure transducer  99  is connected to provide air pressure readings directly as inputs to the electrical system controller  24 . Alternatively, EPTO could be implemented using the pneumatic system if the traction motor PTO were an air pump. 
     The J1939 compliant cable  74  connecting ESC  24  to RPM  40  is a twisted pair of cables. RPM  40  is shown with 6 hardwire inputs (A-F) and one output. A twisted pair cable  64  conforming to the SAE J1708 standard connects ESC  24  to a inlay  64  for the cab dash panel on which various control switches are mounted. The public J1939 twisted pair cable  18  connects ESC  24  to the gauge controller  58 , the hybrid controller  48  and the transmission controller  42 . The transmission controller  42  is provided with a private connection to the cab mounted transmission control console  72 . A connection between the hybrid controller  48  and the console  72  is omitted in this configuration though it may be provided in some contexts. 
       FIG. 6  illustrates in detail the input and output pin usage for RPM  40  for a specific application. Input pin A is the Hybrid Electric Vehicle demand circuit  1  input which can be a 12 volt DC or ground signal. When active the traction motor runs continuously. Input pin B is the Hybrid Electric Vehicle demand circuit  2  input which can be a 12 volt DC or ground signal. When active, the traction motor runs continuously. Input pin C is the Hybrid Electric Vehicle demand circuit  3  input which can be a 12 volt DC or ground signal. When the signal is active the traction motor runs continuously. Input pin D is the Hybrid Electric Vehicle demand circuit  4  input which can be a 12 volt DC or ground signal. When the signal is active the traction motor runs continuously. In other words the designer can provide four remote locations for switches from which an operator can initiate a PTO body power demand signal to operate the traction motor. Input pin E is a hybrid electric vehicle remote PTO disable input. The signal can be either 12 volts DC or ground. When active PTO is disabled. Input pin F is the hybrid electric vehicle EPTO engaged feedback signal. This signal is a ground signal originating with a PTO mounted pressure or ball detent feedback switch. The output pin carries the actual power demand signal. As noted this may be subject to various interlocks. In the example the interlock conditions are that measured vehicle speed be less than 3 miles per hour, the gear setting be neutral and the park brake set. 
       FIG. 7  illustrates the location of chassis output pins and chassis input pins on the electrical system controller  24 . 
     The system described here provides a secondary mechanism for controlling the hybrid electric motor and generator through the use of various original equipment manufacturer (OEM) chassis inputs, circumventing the TEMs&#39; input (demand) signal sourcing devices (e.g. the RPM  40 ). Initiating this mode of operation can be made as simple as desired by use of a single in-cab mounted switch, which may be located in the switch pack  56 , or which may be made more complex and less obvious by using a sequence of control inputs to operate as a “code”. For example, with the vehicle in EPTO mode, the service brake could be depressed and held and the high beams flashed on and off twice. Once the service brake is released subsequent activations of the high beams could generate a signal for toggling the traction motor&#39;s operation. In any event, when the traction motor is under the control of “chassis initiated” inputs. TEM input states are ignored or circumvented. 
     Turning now to  FIG. 8 , a hybrid-electric powertrain with a PTO driven hydraulic system  800  is shown. The hybrid-electric powertrain with a PTO driven hydraulic system  800  comprises an internal combustion engine  802 , an electric motor and generator  803 , a PTO  804 , and a first hydraulic pump  806  and a second hydraulic pump  808 . The PTO  804  is adapted to receive power from either the internal combustion engine  802  or the electric motor and generator  803 . The PTO  804  drives the first hydraulic pump  804  and the second hydraulic pump  808 . 
     As shown in  FIG. 8 , the first hydraulic pump  806  is a fixed displacement hydraulic pump, such as a vane pump, while the second hydraulic pump  808  is a variable displacement hydraulic pump, such as a piston pump. 
     The second hydraulic pump  808  has a control motor  810  and/or a control solenoid  812  to control the adjustment of the variable displacement setting of the second hydraulic pump  808 . The control motor  810  may be a an electric motor, an electro-magnet stepper motor, or the like. The control solenoid  812  may be a an elecrto-magnetic solenoid device or the like. 
     It is contemplated that the internal combustion engine  802  may be utilized to drive the PTO  804  to power the first hydraulic pump  806 , while the electric motor and generator  803  is typically utilized to power the second hydraulic pump  808 . The use of the first hydraulic pump  806  or the second hydraulic pump  808  often depends on a load level placed on a hydraulic system  805 . A large hydraulic load will utilize the first hydraulic pump  806  driven by the internal combustion engine  802 , while a small hydraulic load will utilize the second hydraulic pump  808  driven by the electric motor and generator  803 . 
     The internal combustion engine is adapted to supply torque to the hydraulic pumps  806 ,  808  at engine speeds from about 700 RPM to about 2000 RPM. However, the electric motor and generator  803  produces a high torque level at operating speeds of less than about 1500 RPM. Therefore, when the electric motor and generator  803  is being utilized to run the second hydraulic pump  808  via the PTO  804 , displacement of the second hydraulic pump is adjusted to a larger displacement if the hydraulic load on the hydraulic system  805  requires the electric motor and generator  803  to operate at a speed above 1500 RPM. The control motor  810  and/or the control solenoid  812  increase the displacement of the second pump  808  such that electric motor and generator  803  may supply sufficient hydraulic fluid flow and pressure to the hydraulic system  805 , while also operating at a speed of less than 1500 RPM. 
     Similarly, if the load within the hydraulic system  805  decreases, the displacement of the second hydraulic pump  808  may be adjusted to a smaller displacement, and the electric motor and generator  803  may be slowed to an speed below 1500 RPM. 
     In addition to adjusting the displacement of the second hydraulic pump  808  when the load of the hydraulic system  805  changes to a load that requires the electric motor and generator to operate a speed above 1500 RPM, it is also contemplated that the second hydraulic pump  808  may be adjusted by the control motor  810  and/or the control solenoid  812  to a displacement that allows the electric motor and generator to operate at a higher level of efficiency. For example, if the electric motor and generator produces torque most efficiently at a speed of 1300 RPM, the displacement of the second hydraulic pump  808  may be adjusted so that the load of the hydraulic system  805  is met by the second hydraulic pump  808 , while the electric motor and generator is operating at the speed of 1300 RPM. 
     The hydraulic system  805  depicted in  FIG. 8  further comprises a reservoir  814  that contains hydraulic fluid used in the hydraulic system  805 . The reservoir is in fluid communication with hydraulic motors  816 , hydraulic cylinders  817 , and hydraulic valves  818  of the hydraulic system, providing the necessary fluid to operate the hydraulic motors  816 , hydraulic cylinders  817 , and hydraulic valves  818 . 
     The electric motor and generator  803  is connected to a battery  820  and an electrical controller  822 . The battery  820  stores electrical power for use by the electric motor and generator  803 . The electrical controller  822  regulates electrical energy between the battery  820  and the electrical motor and generator  803 . 
     Turning now to  FIG. 9 , a specific control arrangement and network architecture  900  on which the hybrid-electric powertrain with a PTO driven hydraulic system  800  state may be implemented. A first remote throttle  902  and/or a second remote throttle  904  are provided on TEM components to give a user the ability to control the output of the electric motor and generator  803  or the internal combustion engine  802  in order to control the hydraulic system  805 . The first remote throttle  902  is a variable pedal throttle, while the second remote throttle  904  is a hand operated vernier throttle. 
     As shown in  FIG. 9 , the first remote throttle is electrically connected to the Engine Control Module, or Electronic Control Module, (“ECM”)  906 . The second remote throttle  904  may be electrically connected to the ECM  906  via a remote engine speed control module (“RESCM”)  908  or a remote power module  910 . The RESCM  908  and the remote power module  910  are electronically connected to an Electronic System Controller (“ESC”)  912  via a J1939 compliant cable  914 . 
     The ESC  912  is electronically connected to the ECM  906  via a J1939 compliant cable  916 . The J1939 compliant cable  916  additionally connects a gauge cluster  918 , a hybrid control module  920 , and a transmission control module  922  to the ECM  906 . The ESC  912  monitors the internal combustion engine  802  and the electric motor and generator  803  as well as the demand of the hydraulic system  805  and input from the first remote throttle  904  and/or the second remote throttle  906 , and generates control signals adapted to control the internal combustion engine  802  and the electric motor and generator  803 . The demand of the hydraulic system  805  is greatly influenced by the input from the first remote throttle  904  and/or the second remote throttle  906 . 
     The ESC  912  will generate speed commands for the internal combustion engine  802  and/or the electric motor and generator  803  such that the first hydraulic pump  804  and/or the second hydraulic pump  806  fulfill the demand of the hydraulic system  805 . For instance, the ESC  912  may generate a signal that increases or decreases the speed of the electric motor and generator  803  in order to provide sufficient hydraulic fluid flow from the second hydraulic pump  806 . Similarly, the ESC  912  may generate a signal that increases or decreases the speed of the internal combustion engine  802  in order to provide sufficient hydraulic fluid flow from the first hydraulic pump  804 . 
     The ESC  912  additionally generates an output signal that is transmitted to the second hydraulic pump  806  in the event the displacement of the second hydraulic pump  806  is to be modified. If a hydraulic load is above a predetermined threshold, the displacement of the second hydraulic pump  806  maybe For instance, if the electric motor and generator  803  is being used to power the second hydraulic pump, and the speed of the electric motor and generator  803  is approaching 2000 RPM, the ESC  912  generates an output signal that causes the control motor  810  or the control solenoid  812  to increase the displacement of the second hydraulic pump  806 , such that the output of the second hydraulic pump  806  is increased, and the speed of the electric motor and generator  803  is maintained in a proper operating range. 
     It is additionally contemplated that both the first hydraulic pump  804  and the second hydraulic pump  806  may be used simultaneously. In such a configuration the ESC  912  generates an output signal to the control motor  810  or the control solenoid  812  in order to vary the displacement of the second hydraulic pump  806 . In such a configuration, a smaller first hydraulic pump  804  may be utilized, as the second hydraulic pump  806  will provide additionally pumping capacity to satisfy the demands of the hydraulic system  805 . 
     The hydraulic system  805  of the present embodiment may be utilized to power variable speed applications, such as digger derricks, pressure diggers, document shredders, and other variable speed devices. 
     Additionally, the use of the a variable displacement second hydraulic pump  806  enhances energy utilization by the hybrid-electric powertrain with a PTO driven hydraulic system  800 , as the engine  802  and/or the electric motor and generator  803  may be operated at more efficient settings. Therefore, fuel usage, or electric power required, will be lowered. 
     Turning next to  FIG. 10  a hydraulic hybrid powertrain  1000 . The hydraulic hybrid powertrain  1000  comprises an internal combustion engine  1002  a hydraulic pump  1004  connected to and driven by a PTO  1003 . The PTO may be powered by the internal combustion engine  1002 , or may be a PTO has described above that may be powered by an electric motor and generator  1005  and/or the internal combustion engine  1002 . 
     The hydraulic hybrid powertrain  1000  additionally comprises a hydraulic accumulator  1006  disposed in fluid communication with the hydraulic pump  1004 . 
     The hydraulic accumulator  1006  is adapted to store pressurized hydraulic fluid from the hydraulic pump  1004 . A hydraulic reservoir  1007  additionally is provided in fluid communication with the hydraulic pump  1004 . The hydraulic reservoir  1007  stores low pressure hydraulic fluid that may be pressurized by the hydraulic pump  1004 . 
     An accumulator isolation valve  1008  is disposed at an outlet of the hydraulic accumulator  1006 . The accumulator isolation valve  1008  controls the flow of hydraulic fluid from the hydraulic accumulator  1006 . An accumulator solenoid  1010  positions the accumulator isolation valve  1008  between at least a first position that allows hydraulic fluid to flow from the hydraulic accumulator  1006  and a second position that prevents hydraulic fluid from flowing from the hydraulic accumulator  1006 . It is contemplated that the accumulator solenoid  1010  may also position the accumulator isolation valve  1008  at a variety of intermediate positions between the first position and the second position to control the flow of hydraulic fluid from the hydraulic accumulator  1006 . 
     An accumulator transducer  1012  is disposed in fluid communication with the hydraulic accumulator  1006 . The accumulator transducer  1012  provides an output signal to monitor the pressure within the hydraulic accumulator  1012 . The accumulator transducer  1012  may be utilized to control operation of the hydraulic pump  1004  such that pressure within the hydraulic accumulator  1006  may be maintained at operating levels, yet the hydraulic pump  1004  may only be operated intermittently. 
     The hydraulic hybrid powertrain  1000  additionally comprises vehicle hydraulic system  1013 . The vehicle hydraulic system  1013  may comprise an open center hydraulic system  1015   a , a closed center hydraulic system  1015   b , or both the open center hydraulic system  1015   a , and the closed center hydraulic system  1015   b.    
     The vehicle hydraulic system  1013  comprises a vehicle hydraulic component transducer  1014 . The vehicle hydraulic component transducer  1014  generates an output signal in response to a hydraulic load within the vehicle hydraulic system. The vehicle hydraulic component transducer  1014  is in electrical communication with an ESC  1016 . The ESC  1016  is in electrical communication with a RPM  1018 , an ECM  1024 , an operator display  1026 , and a gauge cluster  1028 . 
     The ESC  1016  monitors the output of the hydraulic component transducer  1014  and causes the RPM  1018  to generate an output signal  1022  that is transmitted to the accumulator solenoid  1010  to position the accumulator isolation valve  1008 . The RPM  1018  additionally is adapted to receive input signals  1020  from vehicle hydraulic system  1013  indicating that the vehicle hydraulic system  1013  has been activated. The RPM  1018  may thus generate the output signal  1022  that is transmitted to the accumulator solenoid  101  to position the accumulator isolation valve  1008 . It is contemplated that the input signals  1020  from the vehicle hydraulic system  1013  may be utilized generate the output signal  1022  to control an initial opening of the accumulator isolation valve  1008 . It is contemplated that the input signals from the vehicle hydraulic component transducer  1014  may be utilized to generate the output signal  1022  to control the closing of the accumulator isolation valve  1008  when no hydraulic load is present within the vehicle hydraulic system  1013 . 
     The ESC  1016  may also be utilized to reduce the speed of the internal combustion engine  1002 , or even shut off the engine  1002 , when no hydraulic load is present within the vehicle hydraulic system  1013 , by communicating with the ECM  1024 . Similarly, the ESC  1016  may be utilized to increase the speed of the internal combustion engine  1002  via the ECM  1024  if the load present within the vehicle hydraulic system  1013  is not being met by the hydraulic pressure within the hydraulic accumulator  1006  and the hydraulic pump  1004  is required to raise the pressure with in the hydraulic accumulator  1006 . 
     The accumulator transducer  1012  may be used to generate a message on the operator display  1026 , or cause an indication on the gauge cluster  1028 , such that an operator may know the state of the hydraulic accumulator  1006 . 
     The accumulator isolation valve  1008  reduces internal parasitic leakage within the vehicle hydraulic system  1013  by preventing hydraulic fluid from the hydraulic accumulator  1006  to flow past the closed accumulator isolation valve  1008 .