Abstract:
A microprocessor driven two dimensional search engine examines transmission operating points within a plurality of search range spaces and assists in determining properties associated with the driveline at various operating points within the space. The size of the space is reduced by rearrangement of data.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Application No. 60/985,227 filed on Nov. 3, 2007, which is hereby incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    This disclosure relates generally to control systems for electro-mechanical transmissions. 
       BACKGROUND 
       [0003]    The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. 
         [0004]    Known powertrain architectures include torque-generative devices, including internal combustion engines and electric machines, which transmit torque through a transmission device to an output member. One exemplary powertrain includes a two-mode, compound-split, electromechanical transmission which utilizes an input member for receiving motive torque from a prime mover power source, preferably an internal combustion engine, and an output member. The output member can be operatively connected to a driveline for a motor vehicle for transmitting tractive torque thereto. Electric machines, operative as motors or generators, generate a torque input to the transmission, independently of a torque input from the internal combustion engine. The electric machines may transform vehicle kinetic energy, transmitted through the vehicle driveline, to electrical energy that is storable in an electrical energy storage device. A control system monitors various inputs from the vehicle and the operator and provides operational control of the powertrain, including controlling transmission operating state and gear shifting, controlling the torque-generative devices, and regulating the electrical power interchange among the electrical energy storage device and the electric machines to manage outputs of the transmission, including torque and rotational speed. 
       SUMMARY 
       [0005]    A method for decreasing the size of a space from within which a two-dimensional search engine selects points defined by numerical pairs for evaluation, the space including at least one two-dimensional first region, the first region having minimum and maximum abscissa and ordinate values associated with it, includes generating a plurality of contour plots, the contour plots having abscissa and ordinate axes, and including contours which are representative of a property associated with points within the first region bounded by the abscissa and ordinate axes, selecting a second region from each of the contour plots, the second regions each comprising minimum and maximum abscissa values and minimum and maximum ordinate values, providing four tables of data, the data in each table of the four tables including one of four variables selected from the group consisting of: the minimum abscissa value, the maximum abscissa value, the minimum ordinate value, and the maximum ordinate value, providing a two-dimensional input request, extracting a value for each of the minimum abscissa value, the maximum abscissa value, the minimum ordinate value, and the maximum ordinate value from the tables, to provide extracted values based upon the input request;, and defining a search space based on the extracted values. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    One or more embodiments will now be described, by way of example, with reference to the accompanying drawings, in which: 
           [0007]      FIG. 1  is a schematic diagram of an exemplary powertrain, in accordance with the present disclosure; 
           [0008]      FIG. 2  is a schematic diagram of an exemplary architecture for a control system and powertrain, in accordance with the present disclosure; 
           [0009]      FIGS. 3-8  are schematic flow diagrams of various aspects of a control scheme, in accordance with the present disclosure; 
           [0010]      FIG. 9  is a schematic power flow diagram, in accordance with the present disclosure; 
           [0011]      FIG. 10  illustrates one embodiment of a two-dimensional search range or space, which may be a region definable by coordinate axes with associated minimum and maximum abscissa and ordinate values, in accordance with the present disclosure; 
           [0012]      FIG. 11  shows a contour plot of energy losses associated with operating points for a transmission as described herein, in accordance with the present disclosure; and 
           [0013]      FIG. 12  shows one arrangement of data from a plurality of contour plots, in accordance with the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    Referring now to the drawings, wherein the showings are for the purpose of illustrating certain exemplary embodiments only and not for the purpose of limiting the same,  FIG. 1  shows an exemplary electromechanical hybrid powertrain. The exemplary electromechanical hybrid powertrain shown in  FIG. 1  comprises a two-mode, compound-split, electromechanical hybrid transmission  10  operatively connected to an engine  14 , and first and second electric machines (‘MG-A’)  56  and (‘MG-B’)  72 . The engine  14  and first and second electric machines  56  and  72  each generate power which can be transmitted to the transmission  10 . The power generated by the engine  14  and the first and second electric machines  56  and  72  and transmitted to the transmission  10  is described in terms of input torques, referred to herein as T I , T A , and T B  respectively, and speed, referred to herein as N I , N A , and N B , respectively. 
         [0015]    In one embodiment, the exemplary engine  14  comprises a multi-cylinder internal combustion engine which is selectively operative in several states to transmit torque to the transmission  10  via an input shaft  12 , and can be either a spark-ignition or a compression-ignition engine. The engine  14  includes a crankshaft (not shown) operatively coupled to the input shaft  12  of the transmission  10 . A rotational speed sensor  11  is preferably present to monitor rotational speed of the input shaft  12 . Power output from the engine  14 , comprising rotational speed and output torque, can differ from the input speed, N I , and the input torque, T I , to the transmission  10  due to torque-consuming components being present on or in operative mechanical contact with the input shaft  12  between the engine  14  and the transmission  10 , e.g., a hydraulic pump (not shown) and/or a torque management device (not shown). 
         [0016]    In one embodiment the exemplary transmission  10  comprises three planetary-gear sets  24 ,  26  and  28 , and four selectively-engageable torque-transmitting devices, i.e., clutches C 1   70 , C 2   62 , C 3   73 , and C 4   75 . As used herein, clutches refer to any type of friction torque transfer device including single or compound plate clutches or packs, band clutches, and brakes, for example. A hydraulic control circuit  42 , preferably controlled by a transmission control module (hereafter ‘TCM’)  17 , is operative to control clutch states. In one embodiment, clutches C 2   62  and C 4   75  preferably comprise hydraulically-applied rotating friction clutches. In one embodiment, clutches C 1   70  and C 3   73  preferably comprise hydraulically-controlled stationary devices that can be selectively grounded to a transmission case  68 . In a preferred embodiment, each of the clutches C 1   70 , C 2   62 , C 3   73 , and C 4   75  is preferably hydraulically applied, selectively receiving pressurized hydraulic fluid via the hydraulic control circuit  42 . 
         [0017]    In one embodiment, the first and second electric machines  56  and  72  preferably comprise three-phase AC machines, each including a stator (not shown) and a rotor (not shown), and respective resolvers  80  and  82 . The motor stator for each machine is grounded to an outer portion of the transmission case  68 , and includes a stator core with electrical windings extending therefrom. The rotor for the first electric machine  56  is supported on a hub plate gear that is operatively attached to shaft  60  via the second planetary gear set  26 . The rotor for the second electric machine  72  is fixedly attached to a sleeve shaft hub  66 . 
         [0018]    Each of the resolvers  80  and  82  preferably comprises a variable reluctance device including a resolver stator (not shown) and a resolver rotor (not shown). The resolvers  80  and  82  are appropriately positioned and assembled on respective ones of the first and second electric machines  56  and  72 . Stators of respective ones of the resolvers  80  and  82  are operatively connected to one of the stators for the first and second electric machines  56  and  72 . The resolver rotors are operatively connected to the rotor for the corresponding first and second electric machines  56  and  72 . Each of the resolvers  80  and  82  is signally and operatively connected to a transmission power inverter control module (hereafter ‘TPIM’)  19 , and each senses and monitors rotational position of the resolver rotor relative to the resolver stator, thus monitoring rotational position of respective ones of first and second electric machines  56  and  72 . Additionally, the signals output from the resolvers  80  and  82  are interpreted to provide the rotational speeds for first and second electric machines  56  and  72 , i.e., N A  and N B , respectively. 
         [0019]    The transmission  10  includes an output member  64 , e.g. a shaft, which is operably connected to a driveline  90  for a vehicle (not shown), to provide output power, e.g., to vehicle wheels  93 , one of which is shown in  FIG. 1 . The output power is characterized in terms of an output rotational speed, N O  and an output torque, T O . A transmission output speed sensor  84  monitors rotational speed and rotational direction of the output member  64 . Each of the vehicle wheels  93 , is preferably equipped with a sensor  94  adapted to monitor wheel speed, the output of which is monitored by a control module of a distributed control module system described with respect to  FIG. 2 , to determine vehicle speed, and absolute and relative wheel speeds for braking control, traction control, and vehicle acceleration management. 
         [0020]    The input torques from the engine  14  and the first and second electric machines  56  and  72  (T I , T A , and T B  respectively) are generated as a result of energy conversion from fuel or electrical potential stored in an electrical energy storage device (hereafter ‘ESD’)  74 . ESD  74  is high voltage DC-coupled to the TPIM  19  via DC transfer conductors  27 . The transfer conductors  27  include a contactor switch  38 . When the contactor switch  38  is closed, under normal operation, electric current can flow between the ESD  74  and the TPIM  19 . When the contactor switch  38  is opened electric current flow between the ESD  74  and the TPIM  19  is interrupted. The TPIM  19  transmits electrical power to and from the first electric machine  56  by transfer conductors  29 , and the TPIM  19  similarly transmits electrical power to and from the second electric machine  72  by transfer conductors  31 , in response to torque commands for the first and second electric machines  56  and  72  to achieve the input torques T A  and T B . Electrical current is transmitted to and from the ESD  74  in accordance with commands provided to the TPIM which derive from such factors as including operator torque requests, current operating conditions and states, and such commands determine whether the ESD  74  is being charged, discharged or is in stasis at any given instant. 
         [0021]    The TPIM  19  includes the pair of power inverters (not shown) and respective motor control modules (not shown) configured to receive the torque commands and control inverter states therefrom for providing motor drive or regeneration functionality to achieve the input torques T A  and T B . The power inverters comprise known complementary three-phase power electronics devices, and each includes a plurality of insulated gate bipolar transistors (not shown) for converting DC power from the ESD  74  to AC power for powering respective ones of the first and second electric machines  56  and  72 , by switching at high frequencies. The insulated gate bipolar transistors form a switch mode power supply configured to receive control commands. There is typically one pair of insulated gate bipolar transistors for each phase of each of the three-phase electric machines. States of the insulated gate bipolar transistors are controlled to provide motor drive mechanical power generation or electric power regeneration functionality. The three-phase inverters receive or supply DC electric power via DC transfer conductors  27  and transform it to or from three-phase AC power, which is conducted to or from the first and second electric machines  56  and  72  for operation as motors or generators via transfer conductors  29  and  31 , depending on commands received which are typically based on factors which include current operating state and operator torque demand. 
         [0022]      FIG. 2  is a schematic block diagram of the distributed control module system. The elements described hereinafter comprise a subset of an overall vehicle control architecture, and provide coordinated system control of the exemplary hybrid powertrain described in  FIG. 1 . The distributed control module system synthesizes pertinent information and inputs, and executes algorithms to control various actuators to achieve control objectives, including objectives related to fuel economy, emissions, performance, drivability, and protection of hardware, including batteries of ESD  74  and the first and second electric machines  56  and  72 . The distributed control module system includes an engine control module (hereafter ‘ECM’)  23 , the TCM  17 , a battery pack control module (hereafter ‘BPCM’)  21 , and the TPIM  19 . A hybrid control module (hereafter ‘HCP’)  5  provides supervisory control and coordination of the ECM  23 , the TCM  17 , the BPCM  21 , and the TPIM  19 . A user interface (‘UI’)  13  is operatively connected to a plurality of devices through which a vehicle operator may selectively control or direct operation of the electro-mechanical hybrid powertrain. The devices present in UI  13  typically include an accelerator pedal  113  (‘AP’) from which an operator torque request is determined, an operator brake pedal  112  (‘BP’), a transmission gear selector  114  (‘PRNDL’), and a vehicle speed cruise control (not shown). The transmission gear selector  114  may have a discrete number of operator-selectable positions, including the rotational direction of the output member  64  to enable one of a forward and a reverse direction. 
         [0023]    The aforementioned control modules communicate with other control modules, sensors, and actuators via a local area network (hereafter ‘LAN’) bus  6 . The LAN bus  6  allows for structured communication of states of operating parameters and actuator command signals between the various control modules. The specific communication protocol utilized is application-specific. The LAN bus  6  and appropriate protocols provide for robust messaging and multi-control module interfacing between the aforementioned control modules, and other control modules providing functionality such as antilock braking, traction control, and vehicle stability. Multiple communications buses may be used to improve communications speed and provide some level of signal redundancy and integrity. Communication between individual control modules can also be effected using a direct link, e.g., a serial peripheral interface (‘SPI’) bus (not shown). 
         [0024]    The HCP  5  provides supervisory control of the powertrain, serving to coordinate operation of the ECM  23 , TCM  17 , TPIM  19 , and BPCM  21 . Based upon various input signals from the user interface  13  and the powertrain, including the ESD  74 , the HCP  5  generates various commands, including: the operator torque request (‘T O     —     REQ ’), a commanded output torque (‘T CMD ’) to the driveline  90 , an engine input torque command, clutch torques for the torque-transfer clutches C 1   70 , C 2   62 , C 3   73 , C 4   75  of the transmission  10 ; and the torque commands for the first and second electric machines  56  and  72 , respectively. The TCM  17  is operatively connected to the hydraulic control circuit  42  and provides various functions including monitoring various pressure sensing devices (not shown) and generating and communicating control signals to various solenoids (not shown) thereby controlling pressure switches and control valves contained within the hydraulic control circuit  42 . 
         [0025]    The ECM  23  is operatively connected to the engine  14 , and functions to acquire data from sensors and control actuators of the engine  14  over a plurality of discrete lines, shown for simplicity as an aggregate bi-directional interface cable  35 . The ECM  23  receives the engine input torque command from the HCP  5 . The ECM  23  determines the actual engine input torque, T I , provided to the transmission  10  at that point in time based upon monitored engine speed and load, which is communicated to the HCP  5 . The ECM  23  monitors input from the rotational speed sensor  11  to determine the engine input speed to the input shaft  12 , which translates to the transmission input speed, N I . The ECM  23  monitors inputs from sensors (not shown) to determine states of other engine operating parameters which may include without limitation: a manifold pressure, engine coolant temperature, throttle position, ambient air temperature, and ambient pressure. The engine load can be determined, for example, from the manifold pressure, or alternatively, from monitoring operator input to the accelerator pedal  1   13 . The ECM  23  generates and communicates command signals to control engine actuators, which may include without limitation actuators such as: fuel injectors, ignition modules, and throttle control modules, none of which are shown. 
         [0026]    The TCM  17  is operatively connected to the transmission  10  and monitors inputs from sensors (not shown) to determine states of transmission operating parameters. The TCM  17  generates and communicates command signals to control the transmission  10 , including controlling the hydraulic circuit  42 . Inputs from the TCM  17  to the HCP  5  include estimated clutch torques for each of the clutches, i.e., C 1   70 , C 2   62 , C 3   73 , and C 4   75 , and rotational output speed, N O , of the output member  64 . Other actuators and sensors may be used to provide additional information from the TCM  17  to the HCP  5  for control purposes. The TCM  17  monitors inputs from pressure switches (not shown) and selectively actuates pressure control solenoids (not shown) and shift solenoids (not shown) of the hydraulic circuit  42  to selectively actuate the various clutches C 1   70 , C 2   62 , C 3   73 , and C 4   75  to achieve various transmission operating range states, as described hereinbelow. 
         [0027]    The BPCM  21  is signally connected to sensors (not shown) to monitor the ESD  74 , including states of electrical current and voltage parameters, to provide information indicative of parametric states of the batteries of the ESD  74  to the HCP  5 . The parametric states of the batteries preferably include battery state-of-charge, battery voltage, battery temperature, and available battery power, referred to as a range P BAT     —     MIN  to P BAT     —     MAX . 
         [0028]    Each of the control modules ECM  23 , TCM  17 , TPIM  19  and BPCM  21  is preferably a general-purpose digital computer comprising a microprocessor or central processing unit, storage mediums comprising read only memory (‘ROM’), random access memory (‘RAM’), electrically programmable read only memory (‘EPROM’), a high speed clock, analog to digital (‘A/D’) and digital to analog (‘D/A’) circuitry, and input/output circuitry and devices (‘I/O’) and appropriate signal conditioning and buffer circuitry. Each of the control modules has a set of control algorithms, comprising resident program instructions and calibrations stored in one of the storage mediums and executed to provide the respective functions of each computer. Information transfer between the control modules is preferably accomplished using the LAN bus  6  and serial peripheral interface buses. The control algorithms are executed during preset loop cycles such that each algorithm is executed at least once each loop cycle. Algorithms stored in the non-volatile memory devices are executed by one of the central processing units to monitor inputs from the sensing devices and execute control and diagnostic routines to control operation of the actuators, using preset calibrations. Loop cycles are preferably executed at regular intervals, for example at each 3.125, 6.25, 12.5, 25 and 100 milliseconds during ongoing operation of the powertrain. However, any interval between about 2 milliseconds and about 300 milliseconds may be selected. Alternatively, algorithms may be executed in response to the occurrence of any selected event. 
         [0029]    The exemplary powertrain shown in reference to  FIG. 1  is capable of selectively operating in any of several operating range states that can be described in terms of an engine state comprising one of an engine on state (‘ON’) and an engine off state (‘OFF’), and a transmission state comprising a plurality of fixed gears and continuously variable operating modes, described with reference to Table 1, below. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Engine 
                 Transmission Operating 
                 Applied 
               
               
                 Description 
                 State 
                 Range State 
                 Clutches 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 M1_Eng_Off 
                 OFF 
                 EVT Mode 1 
                 C1 70 
                   
               
               
                 M1_Eng_On 
                 ON 
                 EVT Mode 1 
                 C1 70 
               
               
                 G1 
                 ON 
                 Fixed Gear Ratio 1 
                 C1 70 
                 C4 75 
               
               
                 G2 
                 ON 
                 Fixed Gear Ratio 2 
                 C1 70 
                 C2 62 
               
               
                 M2_Eng_Off 
                 OFF 
                 EVT Mode 2 
                 C2 62 
               
               
                 M2_Eng_On 
                 ON 
                 EVT Mode 2 
                 C2 62 
               
               
                 G3 
                 ON 
                 Fixed Gear Ratio 3 
                 C2 62 
                 C4 75 
               
               
                 G4 
                 ON 
                 Fixed Gear Ratio 4 
                 C2 62 
                 C3 73 
               
               
                   
               
             
          
         
       
     
         [0030]    Each of the transmission operating range states is described in the table and indicates which of the specific clutches C 1   70 , C 2   62 , C 3   73 , and C 4   75  are applied for each of the operating range states. As an example, a first continuously variable mode, i.e., EVT Mode  1 , or M 1 , is selected by applying clutch C 1   70  only in order to “ground” the outer gear member of the third planetary gear set  28 . The engine state can be one of ON (‘M1_Eng_On’) or OFF (‘M1_Eng_Off’). A second continuously variable mode, i.e., EVT Mode  2 , or M 2 , is selected by applying clutch C 2   62  only to connect the shaft  60  to the carrier of the third planetary gear set  28 . The engine state can be one of ON (‘M2_Eng_On’) or OFF (‘M2_Eng_Off’). For purposes of this description, when the engine state is OFF, the engine input speed is equal to zero revolutions per minute (‘RPM’), i.e., the engine crankshaft is not rotating. A fixed gear operation provides a fixed ratio operation of input-to-output speed of the transmission  10 , i.e., N I /N O , is achieved. For example, a first fixed gear operation (‘G1’) is selected by applying clutches C 1   70  and C 4   75 . A second fixed gear operation (‘G2’) is selected by applying clutches C 1   70  and C 2   62 . A third fixed gear operation (‘G3’) is selected by applying clutches C 2   62  and C 4   75 . A fourth fixed gear operation (‘G4’) is selected by applying clutches C 2   62  and C 3   73 . The fixed ratio operation of input-to-output speed increases with increased fixed gear operation due to decreased gear ratios in the planetary gears  24 ,  26 , and  28 . The rotational speeds of the first and second electric machines  56  and  72 , N A  and N B  respectively, are dependent on internal rotation of the mechanism as defined by the clutching and are proportional to the input speed measured at the input shaft  12 . 
         [0031]    In response to operator input via the accelerator pedal  113  and brake pedal  112  as captured by the user interface  13 , the HCP  5  and one or more of the other control modules determine torque commands to control the torque generative devices comprising the engine  14  and the first and second electric machines  56  and  72  to meet the operator torque request at the output member  64  and transferred to the driveline  90 . Based upon input signals from the user interface  13  and the hybrid powertrain including the ESD  74 , the HCP  5  determines the operator torque request, a commanded output torque from the transmission  10  to the driveline  90 , the input torque from the engine  14 , clutch torques for the torque-transfer clutches C 1   70 , C 2   62 , C 3   73 , C 4   75  of the transmission  10 ; and the motor torques for the first and second electric machines  56  and  72 , respectively, as is described hereinbelow. 
         [0032]    Final vehicle acceleration can be affected by other factors including, e.g., road load, road grade, and vehicle mass. The engine state and the transmission operating range state are determined based upon operating characteristics of the hybrid powertrain. This includes the operator torque request communicated through the accelerator pedal  113  and brake pedal  112  to the user interface  13  as previously described. The transmission operating range state and the engine state may be predicated on a hybrid powertrain torque demand caused by a command to operate the first and second electric machines  56  and  72  in an electrical energy generating mode or in a torque generating mode. The transmission operating range state and the engine state can be determined by an optimization algorithm or routine which determines optimum system efficiency based upon operator demand for power, battery state of charge, and energy efficiencies of the engine  14  and the first and second electric machines  56  and  72 . The control system manages torque inputs from the engine  14  and the first and second electric machines  56  and  72  based upon an outcome of the executed optimization routine, and system efficiencies are optimized thereby, to manage fuel economy and battery charging. Furthermore, operation can be determined based upon a fault in a component or system. The HCP  5  monitors the torque-generative devices, and determines the power output from the transmission  10  at output member  64  that is required to meet the operator torque request while meeting other powertrain operating demands, e.g., charging the ESD  74 . As should be apparent from the description above, the ESD  74  and the first and second electric machines  56  and  72  are electrically-operatively coupled for power flow therebetween. Furthermore, the engine  14 , the first and second electric machines  56  and  72 , and the electromechanical transmission  10  are mechanically-operatively coupled to transfer power therebetween to generate a power flow to the output member  64 . 
         [0033]      FIG. 3  shows a control system architecture for controlling and managing signal flow in a hybrid powertrain system having multiple torque generative devices, described hereinbelow with reference to the hybrid powertrain system of  FIGS. 1 and 2 , and residing in the aforementioned control modules in the form of executable algorithms and calibrations. The control system architecture is applicable to alternative hybrid powertrain systems having multiple torque generative devices, including, e.g., a hybrid powertrain system having an engine and a single electric machine, a hybrid powertrain system having an engine and multiple electric machines. Alternatively, the hybrid powertrain system can utilize non-electric torque-generative machines and energy storage systems, e.g., hydraulic-mechanical hybrid transmissions (not shown). 
         [0034]    In operation, the operator inputs to the accelerator pedal  113  and the brake pedal  112  are monitored to determine the operator torque request. The operator inputs to the accelerator pedal  113  and the brake pedal  112  comprise individually determinable operator torque request inputs including an immediate accelerator output torque request (‘Output Torque Request Accel Immed’), a predicted accelerator output torque request (‘Output Torque Request Accel Prdtd’), an immediate brake output torque request (‘Output Torque Request Brake Immed’), a predicted brake output torque request (‘Output Torque Request Brake Prdtd’) and an axle torque response type (‘Axle Torque Response Type’). As used herein, the term ‘accelerator’ refers to an operator request for forward propulsion preferably resulting in increasing vehicle speed over the present vehicle speed, when the operator selected position of the transmission gear selector  114  commands operation of the vehicle in the forward direction. The terms ‘deceleration’ and ‘brake’ refer to an operator request preferably resulting in decreasing vehicle speed from the present vehicle speed. The immediate accelerator output torque request, the predicted accelerator output torque request, the immediate brake output torque request, the predicted brake output torque request, and the axle torque response type are individual inputs to the control system. Additionally, operation of the engine  14  and the transmission  10  are monitored to determine the input speed (‘Ni’) and the output speed (‘No’). The immediate accelerator output torque request is determined based upon a presently occurring operator input to the accelerator pedal  113 , and comprises a request to generate an immediate output torque at the output member  64  preferably to accelerate the vehicle. The predicted accelerator output torque request is determined based upon the operator input to the accelerator pedal  113  and comprises an optimum or preferred output torque at the output member  64 . The predicted accelerator output torque request is preferably equal to the immediate accelerator output torque request during normal operating conditions, e.g., when any one of antilock braking, traction control, or vehicle stability is not being commanded. When any one of antilock braking, traction control or vehicle stability is being commanded the predicted accelerator output torque request remains the preferred output torque with the immediate accelerator output torque request being decreased in response to output torque commands related to the antilock braking, traction control, or vehicle stability control. 
         [0035]    The immediate brake output torque request is determined based upon a presently occurring operator input to the brake pedal  112 , and comprises a request to generate an immediate output torque at the output member  64  to effect a reactive torque with the driveline  90  which preferably decelerates the vehicle. The predicted brake output torque request comprises an optimum or preferred brake output torque at the output member  64  in response to an operator input to the brake pedal  112  subject to a maximum brake output torque generated at the output member  64  allowable regardless of the operator input to the brake pedal  112 . In one embodiment the maximum brake output torque generated at the output member  64  is limited to −0.2 g. The predicted brake output torque request can be phased out to zero when vehicle speed approaches zero regardless of the operator input to the brake pedal  1   12 . When commanded by the operator, there can be operating conditions under which the predicted brake output torque request is set to zero, e.g., when the operator setting to the transmission gear selector  114  is set to a reverse gear, and when a transfer case (not shown) is set to a four-wheel drive low range. 
         [0036]    A strategic control scheme (‘Strategic Control’)  310  determines a preferred input speed (‘Ni_Des’) and a preferred engine state and transmission operating range state (‘Hybrid Range State Des’) based upon the output speed and the operator torque request and based upon other operating parameters of the hybrid powertrain, including battery power limits and response limits of the engine  14 , the transmission  10 , and the first and second electric machines  56  and  72 . The predicted accelerator output torque request and the predicted brake output torque request are input to the strategic control scheme  31   0 . The strategic control scheme  310  is preferably executed by the HCP  5  during each 100 ms loop cycle and each 25 ms loop cycle. The desired operating range state for the transmission  10  and the desired input speed from the engine  14  to the transmission  10  are inputs to the shift execution and engine start/stop control scheme  320 . 
         [0037]    The shift execution and engine start/stop control scheme  320  commands changes in the transmission operation (‘Transmission Commands’) including changing the operating range state based upon the inputs and operation of the powertrain system. This includes commanding execution of a change in the transmission operating range state if the preferred operating range state is different from the present operating range state by commanding changes in application of one or more of the clutches C 1   70 , C 2   62 , C 3   73 , and C 4   75  and other transmission commands. The present operating range state (‘Hybrid Range State Actual’) and an input speed profile (‘Ni_Prof’) can be determined. The input speed profile is an estimate of an upcoming input speed and preferably comprises a scalar parametric value that is a targeted input speed for the forthcoming loop cycle. The engine operating commands and the operator torque request are based upon the input speed profile during a transition in the operating range state of the transmission. 
         [0038]    A tactical control scheme (‘Tactical Control and Operation’)  330  is executed during one of the control loop cycles to determine engine commands (‘Engine Commands’) for operating the engine  14 , including a preferred input torque from the engine  14  to the transmission  10  based upon the output speed, the input speed, and the operator torque request comprising the immediate accelerator output torque request, the predicted accelerator output torque request, the immediate brake output torque request, the predicted brake output torque request, the axle torque response type, and the present operating range state for the transmission. The engine commands also include engine states including one of an all-cylinder operating state and a cylinder deactivation operating state wherein a portion of the engine cylinders are deactivated and unfueled, and engine states including one of a fueled state and a fuel cutoff state. An engine command comprising the preferred input torque of the engine  14  and the present input torque (‘Ti’) reacting between the engine  14  and the input member  12  are preferably determined in the ECM  23 . Clutch torques (‘Tcl’) for each of the clutches C 1   70 , C 2   62 , C 3   73 , and C 4   75 , including the presently applied clutches and the non-applied clutches are estimated, preferably in the TCM  17 . 
         [0039]    An output and motor torque determination scheme (‘Output and Motor Torque Determination’)  340  is executed to determine the preferred output torque from the powertrain (‘To_cmd’). This includes determining motor torque commands (‘T A ’, ‘T B ’) to transfer a net commanded output torque to the output member  64  of the transmission  10  that meets the operator torque request, by controlling the first and second electric machines  56  and  72  in this embodiment. The immediate accelerator output torque request, the immediate brake output torque request, the present input torque from the engine  14  and the estimated applied clutch torque(s), the present operating range state of the transmission  10 , the input speed, the input speed profile, and the axle torque response type are inputs. The output and motor torque determination scheme  340  executes to determine the motor torque commands during each iteration of one of the loop cycles. The output and motor torque determination scheme  340  includes algorithmic code which is regularly executed during the 6.25 ms and 12.5 ms loop cycles to determine the preferred motor torque commands. 
         [0040]    The hybrid powertrain is controlled to transfer the output torque to the output member  64  to react with the driveline  90  to generate tractive torque at wheel(s)  93  to forwardly propel the vehicle in response to the operator input to the accelerator pedal  113  when the operator selected position of the transmission gear selector  114  commands operation of the vehicle in the forward direction. Similarly, the hybrid powertrain is controlled to transfer the output torque to the output member  64  to react with the driveline  90  to generate tractive torque at wheel(s)  93  to propel the vehicle in a reverse direction in response to the operator input to the accelerator pedal  113  when the operator selected position of the transmission gear selector  114  commands operation of the vehicle in the reverse direction. Preferably, propelling the vehicle results in vehicle acceleration so long as the output torque is sufficient to overcome external loads on the vehicle, e.g., due to road grade, aerodynamic loads, and other loads. 
         [0041]      FIG. 4  details signal flow in the strategic optimization control scheme  310 , which includes a strategic manager  220 , an operating range state analyzer  260 , and a state stabilization and arbitration block  280  to determine the preferred input speed (‘Ni_Des’) and the preferred transmission operating range state (‘Hybrid Range State Des’). The strategic manager (‘Strategic Manager’)  220  monitors the output speed N O , the predicted accelerator output torque request (‘Output Torque Request Accel Prdtd’), the predicted brake output torque request (‘Output Torque Request Brake Prdtd’), and available battery power P BAT     —     MIN  to P BAT     —     MAX . The strategic manager  220  determines which of the transmission operating range states are allowable, and determines output torque requests comprising a strategic accelerator output torque request (‘Output Torque Request Accel Strategic’) and a strategic net output torque request (‘Output Torque Request Net Strategic’), all of which are input the operating range state analyzer  260  along with system inputs (‘System Inputs’), power cost inputs (‘Power Cost Inputs’), and any associated penalty costs (‘Penalty Costs’) for operating outside of predetermined limits. The operating range state analyzer  260  generates a preferred power cost (‘P*cost’) and associated input speed (‘N*i’) for each of the allowable operating range states based upon the operator torque requests, the system inputs, the available battery power and the power cost inputs. The preferred power costs and associated input speeds for the allowable operating range states are input to the state stabilization and arbitration block  280  which selects the preferred operating range state and preferred input speed based thereon. 
         [0042]      FIG. 5  shows the operating range state analyzer  260  that executes searches in each candidate operating range state comprising the allowable ones of the operating range states, including M 1  ( 262 ), M 2  ( 264 ), G 1  ( 270 ), G 2  ( 272 ), G 3  ( 274 ), and G 4  ( 276 ) to determine preferred operation of the torque actuators, i.e., the engine  14  and the first and second electric machines  56  and  72  in this embodiment. The preferred operation preferably comprises a minimum power cost for operating the hybrid powertrain system and an associated engine input for operating in the candidate operating range state in response to the operator torque request. The associated engine input comprises at least one of a preferred engine input speed (‘Ni*’), a preferred engine input power (‘Pi*’), and a preferred engine input torque (‘Ti*’) that is responsive to and preferably meets the operator torque request. The operating range state analyzer  260  evaluates powertrain operation in M 1 -Engine Off ( 264 ) and M 2 -Engine Off ( 266 ) states to determine a preferred cost (‘P*cost’) for operating the powertrain system responsive to and preferably meeting the operator torque request when the engine  14  is in the engine-off state. 
         [0043]      FIG. 6  schematically shows signal flow for a 1-dimension search scheme  610 , executed in each of G 1  ( 270 ), G 2  ( 272 ), G 3  ( 274 ), and G 4  ( 276 ). A range of one controllable input, in this embodiment comprising minimum and maximum input torques (‘TiMin/Max’), is input to a 1-D search engine  415 . The 1-D search engine  415  iteratively generates candidate input torques (‘Ti(j)’) which range between the minimum and maximum input torques, each which is input to an optimization function (‘Opt To/Ta/Tb’)  440 , for n search iterations. Other inputs to the optimization function  440  include system inputs preferably comprise parametric states for battery power, clutch torques, electric motor operation, transmission and engine operation, the specific operating range state and the operator torque request. The optimization function  440  determines transmission operation comprising an output torque, motor torques, and associated battery and electrical powers (‘To(j), Ta(j), Tb(j), Pbat(j), Pa(j), Pb(j)’) associated with the candidate input torque based upon the system inputs in response to the operator torque request for the candidate operating range state. The output torque, motor torques, and associated battery powers, penalty costs, and power cost inputs are input to a cost function  450 , which executes to determine a power cost (‘Pcost(j)’) for operating the powertrain in the candidate operating range state at the candidate input torque in response to the operator torque request. The 1-D search engine  415  iteratively generates candidate input torques over the range of input torques. The optimization function  440  determines the transmission operation for each candidate input torque. The cost function  450  determines the associated power costs. The The 1-D search engine  415  identifies a preferred input torque (‘Ti*’) and associated preferred cost (‘P*cost’). The preferred input torque (‘Ti*’) comprises the candidate input torque within the range of input torques that results in a minimum power cost of the candidate operating range state, i.e., the preferred cost. 
         [0044]    The preferred operation in each of M 1  and M 2  can be determined by executing a  2 -dimensional search scheme  620 , shown with reference to  FIGS. 7 and 8 , in conjunction with executing a 1-dimensional search using the 1-dimensional search scheme  610  based upon a previously determined input speed which can be arbitrated (‘Input Speed Stabilization and Arbitration’)  615  to determine preferred input speeds (‘N*i’) and associated preferred costs (‘P*cost’) for the operating range states. 
         [0045]      FIG. 7  shows the preferred operation in each of continuously variable modes M 1  and M 2  executed in blocks  262  and  264  of the operating range state analyzer  260 . This includes executing a  2 -dimensional search scheme  620 , shown with reference to  FIGS. 6 and 8 , in conjunction with executing a 1-dimensional search using the 1-dimensional search scheme  610  based upon a previously determined input speed which can be arbitrated (‘Input Speed Stabilization and Arbitration’)  615  to determine preferred costs (‘P*cost’) and associated preferred input speeds (‘N*i’) for the operating range states. As described with reference to  FIG. 8 , the 2-dimensional search scheme  620  determines a a first preferred cost (‘2D P*cost’) and an associated first preferred input speed (‘2D N*T’). The first preferred input speed is input to the 2-dimensional search scheme  620  and to an adder  612 . The adder  612  sums the first preferred input speed and a time-rate change in the input speed (‘N I     —     DOT ’) multiplied by a predetermined time period (‘dt’). The resultant is input to a switch  605  along with the first preferred input speed determined by the 2-dimensional search scheme  620 . The switch  605  is controlled to input either the resultant from the adder  612  or the preferred input speed determined by the 2-dimensional search scheme  620  into the 1-dimensional search scheme  610 . The switch  605  is controlled to input the preferred input speed determined by the  2 -dimensional search scheme  620  into the 1-dimensional search scheme  610  (as shown) when the powertrain system is operating in a regenerative braking mode, e.g., when the operator torque request includes a request to generate an immediate output torque at the output member  64  to effect a reactive torque with the driveline  90  which preferably decelerates the vehicle. The switch  605  is controlled to a second position (not shown) to input the resultant from the adder  612  when the operator torque request does not include regenerative braking. The 1-dimensional search scheme  610  is executed to determine a second preferred cost (‘ID P*cost’) using the 1-dimensional search scheme  610 , which is input to the input speed stabilization and arbitration block  615  to select a final preferred cost and associated preferred input speed. 
         [0046]      FIG. 8  schematically shows signal flow for the 2-dimension search scheme  620 . Ranges of two controllable inputs, in this embodiment comprising minimum and maximum input speeds (‘Ni Min/Max’) and minimum and maximum input powers (‘Pi Min/Max’) are input to a 2-D search engine  410 . In another embodiment, the two controllable inputs can comprise minimum and maximum input speeds and minimum and maximum input torques. The 2-D search engine  410  iteratively generates candidate input speeds (‘Ni(j)’) and candidate input powers (‘Pi(j)’) which range between the minimum and maximum input speeds and powers. The candidate input power is preferably converted to a candidate input torque (‘Ti(j)’) ( 412 ). Each candidate input speed (‘Ni(j)’) and candidate input torque (‘Ti(j)’) are input to the optimization function (‘Opt To/Ta/Tb’)  440 , for n search iterations. Other inputs to the optimization function  440  include system inputs preferably comprising parametric states for battery power, clutch reactive torques, maximum and minimum torque outputs from the first and second electric machines  56  and  72 , engine input torque, the specific operating range state and the operator torque request. The optimization function  440  determines transmission operation comprising an output torque, motor torques, and associated battery and electrical powers (‘To(j), Ta(j), Tb(j), Pbat(j), Pa(j), Pb(j)’) associated with the candidate input power and candidate input speed based upon the system inputs and the operating torque request for the candidate operating range state. The output torque, motor torques, and associated battery powers, penalty costs and power cost inputs are input to a cost function  450 , which executes to determine a power cost (‘Pcost(j)’) for operating the powertrain at the candidate input power and candidate input speed in response to the operator torque request in the candidate operating range state. The 2-D search engine  410  iteratively generates the candidate input speeds and candidate input powers over the range of input speeds and range of input powers. The optimization function  440  determines the transmission operation for each candidate input speed and candidate input power. The cost function  450  determines the associated power costs. The 2-D search engine  410  identifies a preferred input power (‘Pi*’) and preferred input speed (‘Ni*’) and associated preferred cost (‘P*cost’). The preferred input power (‘Pi*’) and preferred input speed (‘Ni*’) comprises the candidate input power and candidate input speed that result in a minimum power cost for the candidate operating range state. 
         [0047]      FIG. 9  schematically shows power flow and power losses through hybrid powertrain system, in context of the exemplary powertrain system described above. There is a first power flow path from a fuel storage system  9  which transfers fuel power (‘P FUEL ’) to the engine  14  which transfers input power (‘P I ’) to the transmission  10 . The power loss in the first flow path comprises engine power losses (‘P LOSS ENG ’). There is a second power flow path which transfers electric power (‘P BAT ’) from the ESD  74  to the TPIM  19  which transfers electric power (‘P INV ELEC ’) to the first and second electric machines  56  and  72  which transfer motor mechanical power (‘P MOTOR MECH ’) to the transmission  10 . The power losses in the second power flow path include battery power losses (‘P LOSS BATT ’) and electric motor power losses (‘P LOSS MOTOR ’). The TPIM  19  has an electric power load (‘P HV LOAD ’) that services electric loads in the system (‘HV Loads’), which can include a low voltage battery storage system (not shown). The transmission  10  has a mechanical inertia power input (‘P INERTIA ’) in the system (‘Inertia Storage’) that preferably include inertias from the engine  14  and the transmission  10 . The transmission  10  has mechanical power losses (‘P LOSS MECH ’) and power output (‘P OUT ’). The brake system  94  has brake power losses (‘P LOSS BRAKE ’) and the remaining power is transferred to the driveline as axle power (‘P AXLE ’). 
         [0048]    The power cost inputs to the cost function  450  are determined based upon factors related to vehicle driveability, fuel economy, emissions, and battery usage. Power costs are assigned and associated with fuel and electrical power consumption and are associated with a specific operating points of the hybrid powertrain. Lower operating costs can be associated with lower fuel consumption at high conversion efficiencies, lower battery power usage, and lower emissions for each engine speed/load operating point, and take into account the candidate operating state of the engine  14 . As described hereinabove, the power costs may include the engine power losses (‘P LOSS ENG ’), electric motor power losses (‘P LOSS MOTOR ’), battery power losses (‘P LOSS BATT ’), brake power losses (‘P LOSS BRAKE ’), and mechanical power losses (‘P LOSS MECH ’) associated with operating the hybrid powertrain at a specific operating point which includes input speed, motor speeds, input torque, motor torques, a transmission operating range state and an engine state. 
         [0049]    The mechanical power loss in the transmission  10  includes power losses due to rotational spinning, torque transfer, and friction, and operation of parasitic loads, e.g., a hydraulic pump (not shown) for the transmission  10 . The mechanical power loss can be determined for each operating range state for the transmission  14  and input speed. Mechanical power loss related to the input speed (‘Ni’) and the output speed (‘No’) can be represented by Eq. 1: 
         [0000]        P   MECH LOSS   =a N   i   +b N   i   2   +c N   i   N   o   +d N   o   2    [1] 
         [0000]    wherein a, b, c, and d comprise calibrated scalar values determined for the specific powertrain system and each specific transmission operating range state. 
         [0050]    Thus, in fixed gear operation, i.e., in one of the fixed gear operating ranges states of G 1 , G 2 , G 3  and G 4  for the embodiment described herein, the power cost input comprising the mechanical power loss to the cost function  450  can be predetermined outside of the 1-dimension search scheme  610 . In mode operation, i.e., in one of the mode operating ranges states of M 1  and M 2  for the embodiment described herein, the power cost input comprising the mechanical power loss to the cost function  450  can be determined during each iteration of the search scheme  620 . 
         [0051]    The state stabilization and arbitration block  280  selects a preferred transmission operating range state (‘Hybrid Range State Des’) which preferably is the transmission operating range state associated with the minimum preferred cost for the allowed operating range states output from the operating range state analyzer  260 , taking into account factors related to arbitrating effects of changing the operating range state on the operation of the transmission to effect stable powertrain operation. The preferred input speed (‘Ni_Des’) is the engine input speed associated with the preferred engine input comprising the preferred engine input speed (‘Ni*’), the preferred engine input power (‘Pi*’), and the preferred engine input torque (‘Ti*’) that is responsive to and preferably meets the operator torque request for the selected preferred transmission operating range state. Due to subjective constraints imposed on a system such as that herein described, the transmission operating range state selected may not in all cases be that which is truly optimal from the standpoint of energy usage and power losses. 
         [0052]    In one embodiment, such a system may provide a search method for determining a desirable input speed for a transmission in a combination that comprises at least one torque actuator mechanically coupled to the transmission, the torque actuator contributing to the input speed of said transmission. One search method includes first selecting a potential operating point for the at least one torque actuator from a search range, in which the potential operating point has associated with it a transmission input speed value and a transmission input power value. For purposes of the disclosure, the term ‘candidate’ can be used interchangeably with the term ‘potential’ in describing operating points and transmission operating range states. A plurality of power losses associated with operation of the combination at the potential operating point is determined, each which is combined to provide a total power loss for that point. The selection of a potential operating point, determination of power losses and their combination is repeated to provide a plurality of potential operating points, each of which have a total power loss associated with them. The potential operating points are evaluated for desirability, based on at least one criteria selected from the group consisting of: objective operating criteria and subjective operating criteria, and one operating point is selected from the plurality of potential operating points. Conducting such a search method under the constraint that the output power of said transmission is kept substantially-constant provides that the contours of the power losses (costs) are more prone to be linear when defined in an N I , P I  plane, thus providing advantageous rapidity for a search engine that incorporates such methodology to convergence on an operating point of interest. 
         [0053]    A search engine such as  410  can be conceived of as operating on a defined two-dimensional space that contains points corresponding to candidate N I  and P I  values for each potential transmission operating range state, such as space S as shown in  FIG. 10  as the region on the coordinate axes bounded by P I  Min, P I  Max, N I  Min, and N I  Max, wherein P I  represents input power to the electromechanical hybrid transmission and N I  is the transmission input speed. The space S, which is the search range, is defined using hardware specifications, which typically include electric machine operating speed limits, engine operating speed limits, transmission output speed, and engine torque limits. However, in general, the space S is not disposed at a static location on the P I , N I  coordinate axes, but rather changes its position over time in response to operating conditions, which may include changes in operator torque requests and changes in road grade. Changes in the location of the space S on the P I , N I  coordinate axes can occur at every iteration of an operational loop in a microprocessor carrying out the iterations and can occur at intervals as short as 1 millisecond. Thus, over a few seconds time, the space S may effectively sweep out a very large space over potential values within the P I , N I  coordinate axes. In accordance with one embodiment of the disclosure, a reduction the effective size of the space S is effected. 
         [0054]    In one embodiment a search engine such as search engine  410  selects, either randomly or according to any desired algorithm, an N I  and P I  pair present in the space S, and a maximum transmission output torque (T O  Max) and a minimum transmission output torque (T O  Min) associated with the N I  and P I  pair chosen is calculated based on system constraints. Repetition of this method for a large number of different potential N I  and P I  pairs provides a plurality of different T O  Min and T O  Max values for each potential transmission operating range state. The method is repeated for each potential transmission operating range state and a plurality of T O  Min and T O  Max pairs are generated for the space S of and for each potential transmission operating range state and N I  and P I  pairs provided. 
         [0055]    From such plurality of different T O  Min and T O  Max values so generated by a search engine for a given potential transmission operating range state, the N I  and P I  pair having the highest T O  Max value associated with each potential transmission operating range state is generally selected as the preferred N I  and P I  pair when an operator torque request is greater than T O  Max. In some embodiments for cases in which an operator torque request is less than T O  Min, the potential N I  and P I  pair associated with the lowest T O  Min value is generally selected as the preferred N I  and P I  for the particular potential transmission operating range state under consideration. In any event, it is in generally desirable to be able to quickly locate, within a space S for each potential transmission operating range state, that N I  and P I  pair that has the least power losses associated with it. The effectiveness of such a task is inhibited by the fact that the location of the space S is moving essentially constantly, which over time makes the effective size of the search range of the space S very large. 
         [0056]    Towards reduction of the effective size of the space S, pre-calculations are undertaken in a computer simulation which in one embodiment is not operatively connected to a drivetrain as described herein. Such pre-calculations, or off-line simulations, are carried out using values for engine coolant temperature, engine torque curves, battery power limits, electric machine speed limits, electric machine torque limits, transmission oil temperature, and battery state-of-charge which are frequently encountered by a motorized vehicle during its operation, to determine maximum and minimum values for N I  and P I  which can be used to define a space S that is smaller in range than the space S that is encountered during use of a search engine and system useful therewith as herein described. Without use of a method as described herein, the search range embraced by the space S was based on N I  min and N I  max values that were based on speed-based system constraints and P I  min and P I  max values that were based on T I  min and T I  max values provided by the ECM  23 ; however a method as provided herein narrows down the search range embraced by the space S, based on off-line simulation results. 
         [0057]    In one embodiment of the disclosure the N I , P I  plane representing search range embraced by the space S is determined by first choosing one point in that plane and evaluating it for power losses. Other points are chosen, either arbitrarily or according to any desire algorithm and similarly evaluated for power loss if the system were operating at those points. By evaluating, via an off-line computer simulation, a large number of points (which may be on the order of 100,000 points), a contour plot such as that shown in  FIG. 11  is obtained. The contour lines present in the plot of  FIG. 11  represent points having equal power losses, or costs associated with operating at those points. The process of generating a plot such as that shown in  FIG. 11  is repeated for points having different combinations of transmission output speeds and transmission output torques to provide one such plot as shown in  FIG. 11  for each N O , T O  point. By such a method, an off-line “library” of plots is generated, the number of which plots is determined by the desires of the programmer, for example, in one embodiment, a library containing about 2500 of such plots is generated. 
         [0058]    Thus, according to the foregoing, the search range was determined by an off-line simulation that evaluates each point in the Ni, Pi plane within the “large” search range space S set by system constraints.  FIG. 11  shows the total power loss (Cost) at an operating point (No, To) in the Ni, Pi domain. The steep contour changes represent the violation of system constraints, e.g., To, Ta, Tb, Ti, and P Batt . The suggested search range space S excludes operating points that violate system constraints and points associated with large costs that are (subjectively) determined as non desirable. For T O  points that are beyond the deliverable T O  limits, a torque margin is included in the window search determination, so that the window does not shrink to a single point in the search plane. 
         [0059]    From  FIG. 11  one can get an idea of locations within the plot where the energy losses (costs, as expressed in units of power therein) are relatively small, which is the area labeled B within the highlighted box in  FIG. 11 . The space labeled B in  FIG. 11  may be determined using an algorithm, one example of which is shown below: 
         [0000]                                If To &gt; To Max Max − To Margin        Find Ni, Pi Range where (To Max &lt; To MaxMax −To Margin) &amp;(Ta        penalty Cost &lt; a) &amp;( Tb Penalty Cost &lt; b) &amp;(Ti penalty Cost &lt; c) &amp;        (PBatt Penalty cost ≦d)       ElseIf To &gt; To MinMin + To Margin        Find Ni, Pi Range where (To Min &lt; To MinMin +To Margin) &amp;(Ta        penalty Cost &lt; a) &amp;( Tb Penalty Cost &lt; b) &amp;(Ti penalty Cost &lt; c) &amp;        (PBatt Penalty cost ≦d)       Else        Find Ni, Pi Range where (To Min ≦ To ≦ To Max) &amp;(Ta penalty Cost        &lt; a) &amp;( Tb Penalty Cost &lt; b) &amp;(Ti penalty Cost &lt; c) &amp;(PBatt        Penalty cost ≦d) &amp;(Objective Power Loss Cost &lt; e)       End                    
in which a, b, c, and d are cost criteria that can reduce the search range to exclude operating points that reside outside of the system constraints. Setting these values to 0 will exclude all points not within the constraints. Setting the values to a small, non-zero positive value has the effect of providing a margin around each of the system constraints to minimize the effect of simulation errors that could otherwise erroneously exclude points that are within the constraints. The Ta/Tb/Ti/PBatt penalty costs refer to the costs that are imposed to the N I , P I  pair that is associated with Ta, Tb, Ti, PBatt points that are not within their achievable limits. In general, these penalty costs are provided to increase proportionally with the amount of how much each point exceeds each achievable limit. The cost criteria “e” can further reduce the search range to exclude points that are within the system constraints but have high objective power loss costs subjectively determined as being non-optimal. In the first If step, a ToMax(ToMin) is calculated for each Ni, Pi point that is evaluated by including the Output Torque limiting inside the search loop. ToMaxMax (ToMinMin) is the maximum(minimum) of all ToMax(ToMin), which represents the maximum(minimum) output torque that can be produced within the evaluated Ni, Pi range. In the Else step, the Objective Power Loss cost is the sum of battery power loss, machine power loss, engine power loss, and transmission power loss.
 
         [0060]    A process as set forth above with respect to determining the area B on  FIG. 11  may be repeated, for each plot that exists in the library that was generated during the off-line simulation, to arrive at an area for each plot that is analogous to area B of  FIG. 11 . In the hypothetical case, such as the one mentioned above in which a library containing 2500 of such plots is generated, an area analogous to area B of  FIG. 11  is generated for each of the 2500 plots. However, the area B of  FIG. 11  can be represented by the four points which define the rectangle of area B therein, and in a method according to one embodiment of the disclosure in which a library containing 2500 of the aforementioned plots were generated, one outcome is a set of four points for each of the 2500 plots generated. 
         [0061]    An alternate representation of the four points for each of the 2500 plots so generated per the foregoing, is to provide four tables of data, each of which four tables of data comprise 2500 entries, and each of which four tables contain values of N I  min, N I  max, P I  min, and P I  max, as shown in  FIG. 12 . Such a table containing N I  min values is amplified in the bubble of  FIG. 12  and is seen to comprise fifty columns of N O  values and fifty rows of T O  values. It is well known in the art to convert power values to torque values when the rpm is known. The tables for the N I  max, P I  min, and P I  max are similarly structured. Thus, when a vehicle operator makes a power request having N O  and T O  values associated with it such as is shown at the top of  FIG. 12 , determination of the N I  min value associated with such a power request is readily found by reference to the N I  min table. For example, if the operator power request comprises an N O  value of 1000 rpm and a T O  value of 1500 Newton*Meters, a microprocessor refers to the table for the N I  min values and simply finds the box having the location 1000, 1500 and extracts the value for N I  min(a). In like fashion, values for N I  max, P I  min, and P I  max for the operator torque request having an N O  value of 1000 rpm and a T O  value of 1500 Newton*Meters are readily extracted from the other three tables. As one of ordinary skill in the art readily recognizes, the number of plots generated being 2500 in this one example was chosen for illustrative purposes, and any desired number of plots may be generated. The values of the parameters N O  and T O  in the example of  FIG. 12  are discrete numbers, and for determining numerical values of N O  and T O  which reside between the values of the rows and columns, simple mathematical interpolation is employed. 
         [0062]    Thus, a method for determining a set of values for N I  min, N I  max, P I  min, and P I  max for input to a 2-D search engine such as  410  has been provided, and these values of N I  min, N I  max, P I  min, and P I  max are sufficient to define search range space S having a substantially smaller size than what is otherwise provided by a system as described herein. This decreased size of the space S provided by a method according to this disclosure translates to decreased demand on computer resources and accordingly results in more efficient searching and faster pinpointing of exact operating points for potential transmission operating modes. 
         [0063]    It is understood that modifications are allowable within the scope of the disclosure. The disclosure has been described with specific reference to the preferred embodiments and modifications thereto. Further modifications and alterations may occur to others upon reading and understanding the specification. It is intended to include all such modifications and alterations insofar as they come within the scope of the disclosure.