Abstract:
A method for determining a control parameter of a power or torque distribution regulator for a hybrid drive of a work machine having the steps of automatically determining a work cycle that has just been performed by the work machine, and selecting of the control parameter as a function of the work cycle determined in the previous step.

Description:
RELATED APPLICATIONS 
       [0001]    This application is a continuation application of International Application Serial No. PCT/EP2014/058216, which has an international filing date of Apr. 23, 2014, and which claims the benefit of German Application Ser. No. 102013208320.3, filed on May 7, 2013. The disclosures of these aforementioned applications are hereby expressly incorporated by reference in their entirety. 
     
    
     FIELD OF THE DISCLOSURE 
       [0002]    The present disclosure relates to a method for determining a control parameter of a power or torque distribution regulator for a hybrid drive of a work machine and to a corresponding control device. 
       BACKGROUND 
       [0003]    Hybrid drives for work machines comprise a combustion engine, a generator driven by a combustion engine, a charge storage device and an electric motor. The propulsion of the work machine or the driving of components driven by the work machine is ensured by a power train in which the driving torques of the combustion engine and of the electric motor are superposed by a summation gear, as a rule a planet gear, or they act jointly on a shaft. By distributing the driving power to the power provided by the combustion engine and the power provided by the charge storage device. Such hybrid drives provide an additional freedom in comparison to conventional drives, in which only the power of the combustion engine can be changed. In order to specify the torque of the combustion engine and the torque of the electric motor, or to distribute a power to be provided to the combustion engine and to the electric motor, different types of regulators are known to be used, and in particular proportional-integral regulators or heuristic regulators. 
         [0004]    These so-called power or torque distribution regulators have to take into consideration other general conditions such as maintaining a certain charge in the charge storage device, and have to be optimized in the sense of an optimization of the overall level of efficiency. Since a preview of the future power need of the work machine is not possible, as would be required for an optimal regulator taking into consideration all the circumstances, control parameters of the regulators (referred to as suboptimal regulators) are specified in such a manner that they work with the most optimal level of efficiency possible for the power demand in the case of a predetermined cycle. Accordingly, in the case of a proportional-integral regulator, for example, the factors, with which the power demand is included proportionally and integrally in the output value for the distribution of a power to be provided to the combustion engine and to the electric motor, are optimized for the predetermined cycle. 
         [0005]    Work machines usually run through different work cycles in the context of the activities to be performed. For example, when spreading manure the load is relatively low, in the case of bale pressing the load is cyclical, alternating between a relatively low and relatively high load, and for plowing the load is relatively high. The adaptation of the control parameter of the regulator is not optimal for all work conditions or states. 
         [0006]    In one known example, a method is provided for the adaptive control of a hybrid vehicle whose combustion engine drives a generator which in turn supplies a charge storage device and an electric motor, the latter alone being used to propel the vehicle. A controller compares a work procedure with a stored reference work procedure in order to determine in which load category the hybrid vehicle is being operated and selects a current control curve and a current rise curve for the operation of the electric motor as a function of the respective load category. The user can additionally specify which task is to be accomplished at a given time, and the controller selects the respective load category as a function of the task. Accordingly, on the one hand, a manual input for the respective cycle may be used and, on the other hand, only the current uptake of the electric motor is controlled; thus no adaptation of the control parameters of a regulator occurs. 
         [0007]    Thus, a need exists for refining a method for determining a control parameter of a power or torque distribution regulator for a hybrid drive of a work machine and of a corresponding power or torque distribution regulator. 
       SUMMARY 
       [0008]    In one embodiment. the method according to this disclosure for determining a control parameter of a power or torque distribution regulator for a hybrid drive of a work machine may have the following steps: (a) automatic determination of a work cycle that has just been performed by the work machine, and (b) selection of the control parameter as a function of the work cycle determined in step (a). 
         [0009]    In other words, one first determines in what work cycle the work machine is at a given time. For this purpose, for example, a classification of measured values acquired by sensors occurs on the basis of pattern recognition by a classification algorithm. The classification algorithm can use procedures which themselves are known such as, for example, a Bayes classifier, a nearest neighbor classifier, a k-nearest neighbor classifier, distance functions, or decision trees. The measured values relate in particular to the speed, a transmission ratio of a manual transmission, the condition of a power take-off shaft, or data transmitted via a data bus. As soon as the current work cycle is known, then at least one control parameter associated with this work cycle is selected and used by the power or torque distribution regulator for the distribution of a power (or torque) to be provided to the combustion engine and to the electric motor. By changing the control parameters, the dynamic behavior of the power or torque distribution regulator may be improved. 
         [0010]    In one example, the control parameter is in particular a factor by means of which the respective torque or power demand is included proportionally or integrally in the output value of the power or torque distribution regulator, implemented as a proportional-integral regulator. 
         [0011]    In another example the work machine in which the power or torque distribution regulator is used may be provided with a combustion engine, a generator which can be driven by the combustion engine, a charge storage device, an electric motor, and a power train having a summation gear in driving connection with the combustion engine and the electric motor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The above-mentioned aspects of the present disclosure and the manner of obtaining them will become more apparent and the disclosure itself will be better understood by reference to the following description of the embodiments of the disclosure, taken in conjunction with the accompanying drawings, wherein: 
           [0013]      FIG. 1  is a side view of an agricultural work machine in the form of a tractor with a pulled bale press; 
           [0014]      FIG. 2  is a diagram of the power train of the work machine and the associated control; and 
           [0015]      FIG. 3  is a flow diagram according to which the control works. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    The embodiments of the present disclosure described below are not intended to be exhaustive or to limit the disclosure to the precise forms in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may appreciate and understand the principles and practices of the present disclosure. 
         [0017]      FIG. 1  shows an agricultural work machine in the form of a tractor  10  and a round bale press  12  pulled by the tractor  10 . The round bale press  12  in itself is conventional and has a vehicle chassis  14  supported on wheels  16 , with a bale formation chamber  18 . The round bale press  12  via a drawbar  20  is pulled by the tractor  10 , and its elements that can be driven are driven by a power take-off shaft  22  of the tractor  10 . The tractor  10  has a vehicle chassis  24  which is supported on front steerable wheels  26  and rear driven wheels  28 . An operator workplace with a seat  32  is located in a cabin  30 . From the cabin, a steering wheel  34 , a gas pedal  36  and an operator interface  38  with a display device and keys or the touch sensitive display device can be activated. 
         [0018]      FIG. 2  shows the power train of the work machine. The crankshaft of a combustion engine  40  implemented as a rule as a diesel engine drives (as a rule via a separating clutch, not indicated) a shaft  42  which itself drives an electric generator  44 , an intermediate gear  46  with gear wheels  48 ,  50  and  52  as well as the input side of a power take-off shaft separating clutch  54 . On the output side, the power take-off shaft separating clutch  54  is connected to an input of a power take-off shaft gear  56  which, on the output side, drives a power take-off shaft separating clutch  58 , and on which the power take-off shaft  22  of the round bale press  12  is coupled in a manner so that it can be taken off. On the output side, the intermediate gear  46  is connected to a summation gear  60  which is implemented in the form of a planet gear whose ring wheel engages with the output gear wheel  52  of the intermediate gear  52  and whose sun gear is connected to the power take-off shaft  64  of an electric motor  62 . The planet gear carrier is coupled to the input side of a manual transmission  66  which, on the output side, drives the rear wheels  28  via a differential gear  68 . 
         [0019]    In another embodiment, the power take-off shaft gear  56  can also be driven downstream of the summation gear  60 . In addition, the manual transmission  66  can be implemented as a power shift transmission, all the others are manual. In yet another embodiment, the summation gears  60  can be associated with the individual wheels  28  and optionally also the front wheels  26 . In a further embodiment, the electric motor  62  can transfer its torque directly or via a gear to the shaft  42  or another site of the power train, i.e., the summation gear  60  could then be omitted and the electric motor  62  could fulfill the function of the generator  44 . In yet another embodiment, all of the mechanical power could be generated by the electric motor  62 , wherein then the maximum powers of the generator  44  and of the electric motor  62  would have to be increased, since the mechanical driving branch is omitted. 
         [0020]    A control device  70  may have a power or torque distribution regulator  72  and a condition acquisition device  74  and is electrically connected to the generator  44 , a combustion engine controller  76 , a charge storage device  78  in the form of an accumulator (or a high-capacity capacitor or the like) and the electric motor  62 . Moreover, the control device  70  is coupled to a sensor  80  for the acquisition of the position of the gas pedal  36 , a speed sensor  82  for the acquisition of the rotational speed of one rear wheel or of the two rear wheels  28 , a sensor for the acquisition of the rotational speed of the input side of the power take-off shaft coupling  58 , a sensor  86  for the acquisition of the transmission ratio of the manual transmission  66  and a data bus  88  to which, among other parts, the operator interface  38  implemented as a virtual terminal is connected. 
         [0021]    In operation, the operator specifies via the gas pedal  36  a desired speed of the tractor  12 , which is transmitted via the sensor  80  to the control device  70 , which activates the combustion engine controller  76  and the electric motor  62  as a function of signals of the power or torque distribution regulator  72 . Depending on the specifications of the power or torque distribution regulator  72 , the control device  70  takes electrical power from the charge storage device  78  in order to drive the electric motor  62  or it charges the charge storage device  78  with electrical power from the generator  44  or with EMF recovered from the electric motor  62 . The manual transmission  66  can be shifted manually by the operator via a lever mechanism or automatically by the control device  70  or via the operator interface  38  and an actuator (not shown) controlled by the control device  70 . The power take-off shaft separating clutch  54  can be shifted via a mechanism by the operator or via the operator interface  38  or a separate switch or an actuator (not shown) controlled by the control device  70 . 
         [0022]    For details regarding the structure and the mode of operation of the power or torque distribution regulator  72 , reference is made to the publication by Michiel Koot, J. T. B. A. Kessels, Bram de Jager, W. P. M. H. Heemels, P. P. J. van den Bosch, and Maarten Steinbuch: Energy management strategies for vehicular electric power systems, IEEE Transactions on Vehicular Technology, 54(3):771-782, 2005, and John T. B. A. Kessels, Michiel W. T. Koot, Paul P. J. van den Bosch, and Daniel B. Kok: Online energy management for hybrid electric vehicles, IEEE Transactions on Vehicular Technology, 57(6):3428-3440, 2008, the disclosures of which are hereby incorporated by reference in their entirety. 
         [0023]    The power or torque distribution regulator  72  is implemented as a proportional-integral regulator and uses control parameters that are a function of the respective activity performed by the work machine. Here, the procedure is in accordance with the flow diagram of  FIG. 3 . 
         [0024]    After the start in step  100 , in which an initialization takes place, step  102  follows, in which, by means of the condition acquisition device  74 , measured values are acquired by sensors over a certain time period and stored. These are measured values from the sensors  80  (for the gas pedal  36 ),  82  (for the speed of the tractor  10 ),  84  (for the rotation condition of the power take-off shaft coupling  58 ), and  86  (for the transmission ratio of the manual transmission  66 ). Furthermore, any desired data can be acquired by the data bus  88 , which can include, for example, an identification of an additional apparatus which may be connected to the data bus  88  (for example, manure distributor, plow or bale press, etc.) or data on the activation of the additional apparatus. 
         [0025]    In step  104 , the stored measured values are evaluated by the condition acquisition device  74  in order to recognize a pattern from which the current work cycle of the work machine can be derived. For this purpose, any desired algorithms can be used such as a Bayes classifier, a nearest neighbor classifier, a k-nearest neighbor classifier, distance functions or decision trees. On this topic, reference is made, for example, to the disclosure of DE 10 2012 220 109 A1 and the prior art cited therein (Sebastian Blank, Georg Kormann, Karsten Berns: A Modular Sensor Fusion Approach for Agricultural Machines, XXXVI CIOSTA &amp; CIGR Section V Conference, June 2011), the disclosures of which are hereby incorporated by reference in their entirety. The current work cycle is selected accordingly from several known work cycles. 
         [0026]    For example, the work cycle of the work machine will be “transport travel” if the manual transmission  66  (acquired with the sensor  86 ) is at a higher transmission ratio and the speed (acquired with the sensor  82 ) is higher than a threshold of 15 km/h, for example. Analogously, the work cycle of the work machine will be “soil processing” if the speed is below a threshold of 5 km/h, for example, and the power of the combustion engine  40  (transmitted by the combustion engine controller  76  to the condition acquisition device  74 ) is above a threshold value of 60% of its nominal power, for example. A “bale pressing” work cycle can be recognized on the basis of frequently changing loads of the combustion engine  40  or on the basis of an identification of a bale press via the data bus  88  in connection with the condition of the outlet shaft coupling  58  (sensor  84 ). A “loader work” work cycle can be recognized on the basis of an activation of a front loader via the data bus  88  or frequent direction change (sensor  82 ). 
         [0027]    Step  106  then follows, in which the condition acquisition device  74  transmits a signal pertaining to the current work cycle to the power or torque distribution regulator  72 , and the power or torque distribution regulator  72  uses a parameter set associated with the work cycle for the regulation of the load distribution to the combustion engine  40  and to the electric motor  62 . This parameter set can have a factor by means of which the given current power demand (known to the control device  70 , for example, on the basis of the position of the gas pedal  36  acquired with the sensor  80  and the power values of the combustion engine  40 , the generator  44  and the electric motor  62 ) is included proportionally in the output value, for the regulation of the torque or a load distribution to the combustion engine  40  and to the electric motor  62 , of the power or torque distribution regulator  72  implemented as a proportional-integral regulator. The parameter set can also have a factor by means of which the respective torque or power demand is included integrally in the output value of the power or torque distribution regulator  72  implemented as a proportional-integral regulator. In this manner one achieves that, in a “transport travel” work cycle, the load change procedures take place more slowly than in a “bale pressing” work cycle, for example. The parameter set can also be selected by the condition acquisition device  74  or another part of the control device  70 . 
         [0028]    During steps  102  to  106 , i.e., as long as the current work cycle is not yet known, the power or torque distribution regulator  72  works with a predetermined standard parameter set. 
         [0029]    Step  108  follows, in which verification is carried out to determine whether the work machine had a longer pause precisely at that moment (for example, longer than 30 s). Such a pause suggests a possible change in the work cycle. If this is not the case, the procedure is continued with step  106  again, i.e., the work cycle existing so far and the associated parameter set continue to be used, and otherwise, step  102  follows again, in order to determine the work cycle anew. 
         [0030]    While embodiments incorporating the principles of the present disclosure have been described hereinabove, the present disclosure is not limited to the described embodiments. Instead, this application is intended to cover any variations, uses, or adaptations of the disclosure using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this disclosure pertains and which fall within the limits of the appended claims.