Abstract:
Messaging in a controller area network is modified to hide thermal engine torque and angular velocity change requests originating with selected nodes with relatively low contention access priority from an engine controller and to route the messages instead through an intermediary controller which is an independent source of thermal engine torque and angular velocity change requests. More specifically, in a hybrid vehicle having a body controller with operational control over power take off equipment, a hybrid controller and a thermal engine controller, angular velocity and torque change requests to support power take off operation are embedded in auxiliary input/output messages. The hybrid controller operates on these auxiliary messages, conflating the embedded angular velocity and torque change requests with its own and rebroadcast in conventional form.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The technical field relates generally to motor vehicle controller area networks and, more particularly, to modification of the communication strategy for hybrid vehicles to avoid conflicting responses by controllers to messages broadcast on the network bus. 
         [0003]    2. Description of the Problem 
         [0004]    Hybrid vehicles are generally equipped with at least two prime movers for developing mechanical power. One prime mover may be a dual function system that can develop mechanical power both for traction or power for take-off (PTO) equipment and which can be backdriven as a step in the conversion of mechanical energy to potential energy for storage. An electric traction motor which can be used for regenerative braking of the vehicle to generate electricity is suitable as such a prime mover, as are pneumatic and hydraulic accumulator based systems and mechanical fly wheels. The other prime mover is typically a thermal engine such as an internal combustion engine (ICE) which may supply mechanical power for traction, to backdrive the electric traction motor for the generation of electricity, to run a generator, and may be able to provide non-regenerative vehicle braking (e.g., engine or “Jake” brakes). The internal combustion engine for a hybrid-ICE/electric vehicle will be called on to carry out at least one of the listed functions and in some parallel type hybrid vehicles will perform more than one. 
         [0005]    The development of vocational commercial truck chassis configured with hybrid electric drive systems which can propel the vehicle as well as provide angular velocity to PTO equipment has increased the complexity of integration of the chassis&#39;s systems (and subsystems), the hybrid electric system and installed PTO equipment, particularly on parallel type hybrid vehicles. One consequence of this increased complexity is reflected in the potential for increased data traffic on the controller area network [CAN] relating to managing the variable rate of change in the angular velocity and moment of inertia of the thermal/internal combustion engine under the management of an engine controller. Multiple controllers or “nodes” on the CAN can be the source of torque/speed requests to which the engine controller is programmed to respond. Among the possible sources of such broadcasts are a transmission controller, an ABS controller, a body controller, and a hybrid controller. The messages generated by the different sources can easily be in conflict with one another with respect to changes in angular speed and torque requested from the thermal engine. 
         [0006]    Conflicts in the timing of messages are handled through a control strategy referred to as, “non-destructive bit wise arbitration”. Arbitration priorities contained in the CAN message structure establish which among conflicting messages has priority to the serial communication bus of the network. If the source of the speed/torque message has a high enough arbitration priority (i.e., a low absolute numeric value), and the other node(s) on the CAN bus with a higher priorities are not in direct conflict with the immediate source, then the controller for the thermal engine responds to the speed/torque message and adjusts the output of the thermal engine accordingly. However, the lower priority node may attempt to broadcast its request following handling of the original request. Where the follow up message changes the result from the original message, variation in the thermal engine&#39;s output can result. In addition, data traffic on the serial communication bus can began to increase with data traffic, particularly relating to operation of the thermal engine, but affecting access to the bus generally. 
         [0007]    A parallel hybrid vehicle with PTO capability greatly increases the chances for conflicting requests for changes in thermal engine angular speed and torque messages. For example, in a conventional (non-hybrid) vehicle, if the operator of the vehicle desires to increase the thermal engine&#39;s angular velocity by the means of a remotely mounted engine speed control device, he could do so through a sensor connected to the body controller which would in turn process and condition the input data as output data for broadcast on the CAN bus as a speed/torque message. A vehicle “up-fitted” for hybrid operation with an electric traction motor/generator which can act as a prime mover in conjunction with the thermal engine to supply angular velocity and torque changes the issue. In this configuration both the hybrid controller and the thermal engine controller will have the task of “co-managing” operation of the thermal engine to adjust the output of the thermal engine depending upon the availability of speed or torque from the electric traction motor/generator. This co-management strategy can become very complex considering the many real time transitions which will take place requiring the thermal engine to act as the prime mover exclusively (the motor/generator operating to charge the battery pack under power from the thermal engine) or the hybrid electric traction motor/generator acting as the prime mover supporting electrified power take off (ePTO) operation. 
       SUMMARY 
       [0008]    Controller area network messaging is modified to hide thermal engine torque and angular velocity change requests originating with selected nodes with relatively low contention access priority from an engine controller and to route the messages instead through an intermediary controller which is an independent source of thermal engine torque and angular velocity change requests. This creates a logical series relationship among the controllers involved. Here it is contemplated that engine torque and angular velocity requests relating to PTO operation, which typically are broadcast by a body controller, a relatively low priority controller, be routed through the hybrid controller, a higher priority controller and one which is a also a source of angular velocity and torque change requests and the controller which is the most likely source of conflicting change requests for the body controller. More specifically, when the body controller determines a need for a change in thermal engine output it broadcasts an auxiliary datalink messages (in the SAE J1939 standard an auxiliary input output or “auxio” messages with an eight byte data field) in which angular velocity and torque level change requests for the engine controller are embedded. The hybrid controller is programmed to recognize the auxiliary datalink messages and conflate the embedded requests with its own torque and angular speed change requests and to broadcast the conflated request in a single message of a type recognized by the engine controller. The engine controller is not programmed to respond to the auxiliary input/output message. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a side view of hybrid-electric vehicle carrying a power take-off operation. 
           [0010]      FIG. 2  is a high level schematic of a vehicle drive train and vehicle control system for a hybrid-electric vehicle. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    In the following detailed description example sizes/models/values/ranges may be given with respect to specific embodiments but are not to be considered generally limiting. 
         [0012]    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 commercial vehicle which supports a PTO vocation. The hybrid mobile aerial lift truck  1  includes a PTO load, here an aerial lift unit  2  mounted on a truck bed  12 . Chassis inputs distributed around the hybrid mobile aerial lift truck  1  may be used to control deployment and positioning of the aerial lift unit  2  and other elements such as outriggers or drills for PTO. The operator will usually specifically activate PTO by use of a dedicated switch which may establish a controlling location or by throttle like controls located on the vehicle body. 
         [0013]    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  12  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 . Bucket  5  is pivotally attached to the free end of boom  4  to maintain a horizontal orientation at all times. A hydraulic lifting unit  9  is interconnected between bracket  7  and the lower boom  3  by pivot connection  10  to the bracket  7  pivot  13  on the lower boom  3 . Hydraulic lifting unit  9  is connected to a pressurized supply of a suitable hydraulic fluid, which allows the assembly to be lifted and lowered. The primary source of pressurized hydraulic fluid may be a pump powered by either (or both) of two prime movers for hybrid mobile aerial lift truck  1 . Typically an internal combustion engine and an electric traction motor serve as the prime movers. 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 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 assembly  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. Upper boom compensating assembly  17  is usually supplied with pressurized hydraulic fluid from the same sources as hydraulic lifting unit  9 . Outriggers (not shown) may be used installed at the corners of the truck bed  12 . Pressurized hydraulic fluid for these operations may be supplied by a PTO hydraulic pump. 
         [0014]    Many contemporary vehicles provide integration over the control of multiple vehicle systems through use of a controller area network (CAN). A CAN is a multiple master serial data bus for connecting local nodes over the serial data bus. Messages on the serial data bus are not addressed as such but are broadcast. The controllers are usually functionally specialized to provide engine control, anti-lock braking control, transmission control, and so on. The specialized controllers are one type of CAN bus node. Any controller may be programmed to respond to the broadcast messages. Conflict for access to the bus is handled by the relative dominance of the identifier field for the data (which can reflect the source), which occurs immediately after the start-of-frame field. For example, messages from the anti-lock brake controller are given the highest priority in the Society of Automotive Engineers J1939 standard. Each type of message has a unique priority. The J1939 standard provides for torque speed request messages for the engine controller from any one of several controllers including a general body controller (typically in response to demands for power take-off applications), the anti-lock braking system controller and, on hybrid vehicles, the hybrid controller. 
         [0015]    Referring to  FIG. 2 , a high level schematic of a control system  21  implemented using a CAN and a vehicle drive train  20  for a hybrid mobile aerial lift truck  1  or other types of vocational commercial vehicles is illustrated. As part of the overall control scheme, requests for increases or decreases in angular velocity and torque for various applications, including a PTO application/device  22 , are handled. One potential source of requests for changes in available angular speed torque on the drive train, including from a thermal engine  28 , is an electrical system controller (ESC)/body controller  24 . ESC  24  is linked by a Society of Automotive Engineers (SAE) J1939 standard compliant serial data bus  18  to a variety of local controllers including two controllers with direct control over the vehicle&#39;s prime movers, which are the controllable sources of angular velocity and torque. These are the hybrid controller  48  and the engine controller (ECM)  46 , which provide direct control over the traction motor/generator  32  and thermal engine  28 . For the purposes of the present application, the possibility of using vehicle kinetic energy as a source of angular velocity and torque for any purpose other than to backdrive the traction motor/generator  32  for the generation of electricity or to be dissipated by engine braking is discounted. 
         [0016]    ESC  24  is typically directly connected to selected inputs (including sensors  27 ) and to outputs (such as to headlamps (not shown)). ESC  24  communicates with a dash panel  44  from which it may obtain signals indicating headlight on/off switch position and provide on/off signals to other items, such as dash instruments (not shown). Ignition position is comprehended by a sensors package  27 , directly connected to input ports of the ESC  24 . Signals relating to activating power take-off operation (PTO), and changing the output levels of the prime movers engaged to support a PTO device  22  such as a hydraulic pump, including angular velocity and torque, may be generated from a number of sources, including an in-cab switch pack  56 , an remote switch pack  52  or a remote vernier throttle  54 . Signals from the in-cab switch pack  56 , remote switch pack  52  and remote vernier throttle  54  are communicated to ESC  24  over one of the vehicle data links, such as a SAE J1708 compliant data link  64  for in-cab switch pack  56  or serial data bus  74  for switch pack  52  (through remote power module  40 ) and remote verier throttle  54  (through remote engine speed control module (RESMC)  19 ). SAE J1708 compliant data links exhibit a low baud rate data connection, typically about 9.7K baud and are typically used for transmission of on/off switch states. SAE J1939 compliant data links exhibit much higher data transmission rate and are commonly employed in controller area networks. ESC  24  places the requests into an SAE J1939 defined auxiliary input/output (auxio) message with an eight byte data field to be broadcast over the serial data bus  18  with the requested angular velocity and torque included in the message&#39;s data field. ESC  24  does not broadcast explicit thermal engine velocity and torque request messages in response to PTO related operations. 
         [0017]    Five controllers in addition to the ESC  24  are illustrated as connected to the serial data bus  18 . These controllers include an engine controller  46 , a transmission controller  42 , a hybrid controller  48 , a gauge controller  58  and an anti-lock brake system (ABS) controller  50 . Three of these controllers, the transmission controller  42 , the hybrid controller  48  and the anti-lock brake system controller (ABS)  50 , can be sources of torque/speed messages broadcast over serial data bus  18 . The hybrid controller  48  is programmed to respond to the auxiliary input output (auxio) messages from ESC  24  which carry the embedded angular velocity and torque requests relating to PTO device  22  operation. The hybrid controller  48  normally generates angular velocity and torque requests for the engine controller (ECM)  46  relating to operation of the thermal engine  28  to backdrive the traction motor/generator  32  to generate electricity to charge the traction batteries  34 . During operation of PTO device  22  the hybrid controller  48  adds or subtracts the velocity and torque change requests from ESC  24  from its own velocity and torque requests as appropriate and broadcasts the result as a angular velocity and torque change message over serial data bus  18 . 
         [0018]    Otherwise the hybrid drive train  20  operates as a conventional hybrid system with hybrid controller  48 , transmission controller  42  and engine controller  46  coordinating operations of the hybrid drive train  20  to select between the engine  28  and the traction motor  32  as the prime mover for the vehicle (or possibly to combine the output of the engine and the traction motor). During vehicle braking these same controllers coordinate disengagement and including potentially shutting down engine  28  and operation of traction motor  32  in its generation mode to recapture some of the vehicle&#39;s kinetic energy. The ESC  24  and the ABS controller  50  provide data over serial data bus  18  used for these operations, including brake pedal position, data relating to skidding, throttle position and other power demands such as for PTO device  22 . The hybrid controller further monitors a proxy relating to traction battery  34  state of charge (SOC). 
         [0019]    Hybrid drive train  20  may be a parallel hybrid diesel electric system in which the traction motor/generator  32  is connected in line with an engine  28  through an auto-clutch  30  so that the engine  28 , the traction motor/generator  32 , or both in combination, can function as the vehicle&#39;s prime mover. In a parallel hybrid-electric vehicle the fraction motor/generator  32  is used to recapture vehicle kinetic energy during deceleration by using the drive wheels  26  to back drive the traction motor/generator  32  thereby applying a portion of the vehicle&#39;s kinetic energy to the generation of electricity. The generated electricity is converted from three phase AC by the hybrid inverter  36  and applied to traction batteries  34  as direct current power. In other words the system functions to recapture a vehicle&#39;s inertial momentum during braking and convert and store the recaptured energy as potential energy for later use, including reinsertion into the hybrid drive train  20 . Thermal engine  28  is disengaged from the other components in hybrid drive train  20  by opening auto-clutch  30  during periods when the traction motor/generator  32  is back driven. 
         [0020]    Transitions between positive and negative traction motor/generator  32  electrical power consumption are detected and managed by a hybrid controller  48 . Traction motor/generator  32 , during braking, generates three phase alternating current which is applied to a hybrid inverter  36  for conversion to direct current (DC) for application to traction battery  34 . When the traction motor/generator  32  is used as a vehicle prime mover the flow of power is reversed. 
         [0021]    High mass vehicles tend to exhibit poorer gains from hybrid locomotion than do automobiles. Thus electrical power available from fraction battery  34  is often used to power other vehicle systems such as a PTO device  22 , which may be a hydraulic pump, by supplying electrical power to the traction motor/generator  32  which in turn provides the motive force or mechanical power used to operate the PTO device  22 . In addition, traction motor/generator  32  may be used for starting thermal engine  28 . 
         [0022]    The various local controllers may be programmed to respond to data from ESC  24  passed to serial data bus  18 . Hybrid controller  48  determines, based on available battery charge state, requests for power. Hybrid controller  48  generates the appropriate signals for application to serial data bus  18  for instructing the engine controller  46  to turn thermal 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 device  22  (or simply pressurized hydraulic fluid to PTO device  22  where transmission  38  serves as the hydraulic pump) or if the transmission is to be in neutral. 
         [0023]    PTO device  22  engagement and PTO load  23  control is implemented through one or more remote power modules (RPMs)  40 . Remote power modules  40  are data linked expansion input/output modules dedicated to the ESC  24 , which is programmed to utilize them. One RPM  40  functions as the controller for PTO device  22 , and provides any hardwire outputs  70  and hardwire inputs  66  associated with the PTO device  22 . Position sensors, valve control and the like may also be provided a PTO load  23  which may include elements such as hydraulic motors, boom extensions, etc. Requests for operation of PTO load  23  and, potentially, response reports are applied to the serial data bus  74  for transmission to the ESC  24 , which formats the request for receipt by specific controllers or as reports. ESC  24  is also programmed to control valve states through the first RPM  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. “Remote Power Modules” were referred to as “Remote Interface Modules” at the time. A second RPM  40  is illustrated which accepts switching inputs from a switch pack  52  for control of the first RPM  40  (after routing through ESC  24 ). In addition, RESCM  19  is provided to allow proportional control over the hydraulic PTO using a remote vernier throttle  54 . Direct control over thermal engine  28  angular velocity and torque output is implemented through in cab throttle  76  and remote throttle  78  which provide inputs directly to the engine controller  46 . 
         [0024]    Transmission controller and ESC  24  both operate as portals and/or translation devices between the various data links and serial data buses  68 ,  18 ,  74  and  64 . Data link  68  and serial data bus  74  may be proprietary and operate at substantially higher baud rates than does the serial data bus  18 . Accordingly, buffering is provided for messages passed between data links. 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 serial data bus  74  may translate to a request for transmission engagement from ESC  24  to transmission controller  42 . Serial data buses and links  18 ,  68  and  74  are usually controller area network buses which conform to the SAE J1939 protocol. 
         [0025]    The modification of the messaging scheme, while retaining SAE J1939 provided message types, creates a logical series relationship between the engine controller  46 , the hybrid controller  48 , and the ESC  24 . Such a logical series approach allows the ESC  24  to broadcast auxiliary datalink message/s containing various thermal engine  28  angular velocity and torque level change requests which are only known to the hybrid controller  48 . Because of the auxiliary character of these messages, the engine controller  46  does not recognize or respond to the messages. However, the hybrid controller  48  does recognize the messages and manages its own desired variable requests for the thermal engine  28  along with those of the ESC  24  and broadcasts the combined requests in the form of a single source messaging structure in the conventional format that the engine controller  46  recognizes. This virtually eliminates the conflicting responses introduced by use of parallel message structures where the hybrid controller  48  and the ESC  24  can compete with one another for some level of control of the thermal engine  28 . 
         [0026]    The existing vehicle CAN is exploited to monitor and control the operation of the chassis hybrid electric vehicle components, systems and subsystems as well as truck equipment manufactures&#39; (TEM) truck mounted equipment. The components, systems, subsystems and TEM mounted equipment monitored include the thermal engine&#39;s  28  angular velocity through the hybrid controller  48  as well as TEM and input signals coming from chassis and/or the TEM devices requesting changes in the angular velocity of the thermal engine  28  and the hybrid electric traction motor/generator  32  as primary movers. 
         [0027]    The present CAN communication strategy mediates requests originating with TEM mounted engine speed control devices, for example discrete switches, vernier devices and the like which are integrated into the existing CAN bus environment through elements such as remote power modules and remote engine speed control modules which operate through a body controller and the hybrid controller. The effective logical relationship between the engine controller, the hybrid controller and the body controller is altered. This substantially reduces conflict introduced by parallel angular velocity and engine torque message structures from differing sources where the hybrid controller and body controller compete with one another for some level of control of the thermal engine  28 . The modification is minimal since it can be implemented using existing vehicle hardware and software architectures.